Volume 31,Issue 4,2024 Table of Contents
2024, 31(4):1-12.
DOI: 10.13673/j.pgre.202406002
Abstract:
After more than 60 years of exploration and development， the conventional oil and gas in the middle and shallow layers of the oil-rich sag in Jiyang Depression and in the ultra-denudation zones at the western edge of Junggar Basin have been in the mature exploration stage， which are the main body of reserve increase in Shengli exploration area. The exploration targets are becoming increasingly complex and subtle， and the difficulty of large-scale reserve increase continues to rise. It is urgent to strengthen the research and judgment of the exploration situation and resource potential evaluation， formulate targeted exploration and development strategies， and ensure the sustainable development of exploration in Shengli Oilfield. The exploration condition and situation resource potential， and areas with reserve increase were analyzed， and the remaining resource potential and favorable exploration directions were clarified in the eastern and western parts of Shengli exploration area. It was believed that Shengli exploration area still had a resource foundation for sustainable development， with deep and ultra-deep layers having the potential for large-scale reserve increase， peripheral low exploration areas having greater exploration potential， and unconventional oil and gas being the real resource replacement field. The implementation of the“ three major exploration strategy transformations” was proposed， which included a shift from conventional oil and gas focus to equal emphasis on both conventional and non-conventional oil and gas in types， a shift from middle and shallow layers to deep and ultra-deep layers in stratigraphic systems， and a shift from mature oil areas to comprehensive exploration of the whole exploration area in the regions. An exploration development strategy of“ focusing on the whole area， successfully exploring deep layers， emphasizing both conventional and non-conventional oil and gas， and implementing coordinated promotion” was developed. The development path was proposed of“ persisting in tackling difficulties in low exploration areas to achieve breakthroughs， continuing deep and ultra-deep layer exploration to form a new position for large-scale reserve increase， emphasizing both conventional and non-conventional oil and gas to achieve stable reserve increase， and maintaining efficient management to promote high-quality exploration development”， which pointed out the direction for high-quality exploration development of Shengli Oilfield and provided ideas and directions for exploration in similar exploration areas in Bohai Bay Basin and Junggar Basin.
After more than 60 years of exploration and development， the conventional oil and gas in the middle and shallow layers of the oil-rich sag in Jiyang Depression and in the ultra-denudation zones at the western edge of Junggar Basin have been in the mature exploration stage， which are the main body of reserve increase in Shengli exploration area. The exploration targets are becoming increasingly complex and subtle， and the difficulty of large-scale reserve increase continues to rise. It is urgent to strengthen the research and judgment of the exploration situation and resource potential evaluation， formulate targeted exploration and development strategies， and ensure the sustainable development of exploration in Shengli Oilfield. The exploration condition and situation resource potential， and areas with reserve increase were analyzed， and the remaining resource potential and favorable exploration directions were clarified in the eastern and western parts of Shengli exploration area. It was believed that Shengli exploration area still had a resource foundation for sustainable development， with deep and ultra-deep layers having the potential for large-scale reserve increase， peripheral low exploration areas having greater exploration potential， and unconventional oil and gas being the real resource replacement field. The implementation of the“ three major exploration strategy transformations” was proposed， which included a shift from conventional oil and gas focus to equal emphasis on both conventional and non-conventional oil and gas in types， a shift from middle and shallow layers to deep and ultra-deep layers in stratigraphic systems， and a shift from mature oil areas to comprehensive exploration of the whole exploration area in the regions. An exploration development strategy of“ focusing on the whole area， successfully exploring deep layers， emphasizing both conventional and non-conventional oil and gas， and implementing coordinated promotion” was developed. The development path was proposed of“ persisting in tackling difficulties in low exploration areas to achieve breakthroughs， continuing deep and ultra-deep layer exploration to form a new position for large-scale reserve increase， emphasizing both conventional and non-conventional oil and gas to achieve stable reserve increase， and maintaining efficient management to promote high-quality exploration development”， which pointed out the direction for high-quality exploration development of Shengli Oilfield and provided ideas and directions for exploration in similar exploration areas in Bohai Bay Basin and Junggar Basin.
2024, 31(4):13-23.
DOI: 10.13673/j.pgre.202405012
Abstract:
Jiyang Depression， as one of the mature exploration areas in Bohai Bay Basin， has been explored and developed for over 60 years. It is urgent to solve the theoretical understanding problems such as oil and gas resource potential， exploration direction，and accumulation law to realize the sustainable development of oil and gas exploration. The evolution process of hydrocarbon generation and hydrocarbon generation potential of different types of source rocks were compared based on the analysis and testing of the sedimentary environment and organic geochemical characteristics of a large number of source rock samples in the primary hydrocarbon-generating strata and the hydrocarbon generation simulation experiment. It is found that the source rocks in the saline environment have the characteristics of high ancient productivity and low activation energy，and a“ saline and hydrocarbon-rich” of hydrocarbon generation and expulsion mode was established in the continental lake basin. It breaks through the traditional understanding that source rock in freshwater environments is the primary source of oil and gas. It is pointed out that“ strong cementation in early stage and strong dissolution in late stage” are the essential reasons for the formation of a large number of secondary dissolution pores in the deep reservoirs by analyzing the relationship between porosity and acid-base properties of formation fluid during diagenetic evolution of deep reservoirs. The genetic problem of effective reservoirs of deep clastic rocks under a high geothermal background is solved. The paper summarizes and puts forward the orderly distribution of lithology， structure-lithology， lithologystructure， and tectonic reservoirs from subsag to slope zones based on the exploration practice in Jiyang Depression. Therefore， the theoretical understanding of refined oil and gas exploration in mature exploration areas of“ saline and hydrocarbon-rich， acid-base control， and orderly accumulation” has been innovated， and the potential of remaining resources has been defined. The direction of deep exploration has been pointed out， so oil and gas exploration has changed from passive transfer to active exploration. The division and optimization method of the“ exploration layer unit” suitable for the refined exploration stage is innovatively established，and a“ seven-step” refined exploration and evaluation process is formed for mature exploration areas. The paper points out the critical exploration directions and fields with increasing reserves in the future， which provide essential guarantees for the long-term benefit and sustainable development of the oilfield based on the new geological understanding of Jiyang Depression and the results of the latest round of oil and gas resource evaluation.
Jiyang Depression， as one of the mature exploration areas in Bohai Bay Basin， has been explored and developed for over 60 years. It is urgent to solve the theoretical understanding problems such as oil and gas resource potential， exploration direction，and accumulation law to realize the sustainable development of oil and gas exploration. The evolution process of hydrocarbon generation and hydrocarbon generation potential of different types of source rocks were compared based on the analysis and testing of the sedimentary environment and organic geochemical characteristics of a large number of source rock samples in the primary hydrocarbon-generating strata and the hydrocarbon generation simulation experiment. It is found that the source rocks in the saline environment have the characteristics of high ancient productivity and low activation energy，and a“ saline and hydrocarbon-rich” of hydrocarbon generation and expulsion mode was established in the continental lake basin. It breaks through the traditional understanding that source rock in freshwater environments is the primary source of oil and gas. It is pointed out that“ strong cementation in early stage and strong dissolution in late stage” are the essential reasons for the formation of a large number of secondary dissolution pores in the deep reservoirs by analyzing the relationship between porosity and acid-base properties of formation fluid during diagenetic evolution of deep reservoirs. The genetic problem of effective reservoirs of deep clastic rocks under a high geothermal background is solved. The paper summarizes and puts forward the orderly distribution of lithology， structure-lithology， lithologystructure， and tectonic reservoirs from subsag to slope zones based on the exploration practice in Jiyang Depression. Therefore， the theoretical understanding of refined oil and gas exploration in mature exploration areas of“ saline and hydrocarbon-rich， acid-base control， and orderly accumulation” has been innovated， and the potential of remaining resources has been defined. The direction of deep exploration has been pointed out， so oil and gas exploration has changed from passive transfer to active exploration. The division and optimization method of the“ exploration layer unit” suitable for the refined exploration stage is innovatively established，and a“ seven-step” refined exploration and evaluation process is formed for mature exploration areas. The paper points out the critical exploration directions and fields with increasing reserves in the future， which provide essential guarantees for the long-term benefit and sustainable development of the oilfield based on the new geological understanding of Jiyang Depression and the results of the latest round of oil and gas resource evaluation.
3 Research progress and potential directions of oil and gas exploration in key fields of Junggar Basin
WANG Jinduo
,
ZHANG Guanlong
,
ZHUANG Xinming
,
GONG Yajun
,
QU Yansheng
,
ZHANG Yi
,
XUE Yan
,
CHENG Shiwei
2024, 31(4):24-41.
DOI: 10.13673/j.pgre.202406033
Abstract:
Shengli exploration area in Junggar Basin is mainly located in the ultra-denudation zone， complex piedmont zone， and deep subsag zone around the basin. The conditions for oil and gas accumulation are complex， and exploration is difficult. In order to clarify the potential direction of key fields in Shengli exploration area and guide the optimization of the following oil and gas exploration deployment order， the next potential directions of each key field were analyzed on the basis of systematic summary of the exploration research progress of the sedimentation， reservoir， oil source correlation， transport system， hydrocarbon accumulation mode， as well as oil and gas enrichment control factors in the ultra-denudation zone field in the western margin of Junggar Basin，the deep field of the upper combination in the central area of Junggar Basin， the ultra-deep field of the lower combination in the central area of Junggar Basin， and the piedmont zone field in the northern margin and southeastern areas of Junggar Basin. The results show that the Jurassic-Cretaceous in Hashan area， the Neogene Shawan Formation in Chepaizi area， and the Carboniferous in Chepaizi area in the ultra-denudation zone in the western margin of the Junggar Basin， as well as the Jurassic Qigu Formation in Yongjin-Zhengshacun area and the Jurassic Sangonghe Formation in Moxizhuang area in the deep area of the upper combination in the central area of the Junggar Basin， are the main positions for increasing reserves and production in the future. The Permian Upper Wuerhe Formation-Triassic Karamay Formation in Well Zheng 10 area of Shawan Sag in the ultra-deep area of the lower combination in the central area of the Junggar Basin and the Permian Fengcheng Formation-Xiazijie Formation in Well Zhuangshen 1 area of the western sag of Well Pen 1 are the next important replacement positions. The parautochthonous nappe systems of the Hashan piedmont zone in the northern margin of the Junggar Basin and the southern and northern piedmont zones of Bogda Mountain in the southeastern margin of the Junggar Basin are the favorable positions to be explored continuously in the next step. The unconventional shale gas field in the deep Carboniferous strata of Shibei Sag and Shiqiantan Sag is a reserve position that needs to be actively prepared in the future. During the“ 14th-15th Five Year Planin 2021-2030” period， Shengli exploration area should be guided by the exploration concept of“ focusing on the whole area， successfully exploring deep layers， emphasizing both conventional and unconventional oil and gas， and implementing coordinated promotion” and continuously and orderly promote exploration in various key fields of the basin.
Shengli exploration area in Junggar Basin is mainly located in the ultra-denudation zone， complex piedmont zone， and deep subsag zone around the basin. The conditions for oil and gas accumulation are complex， and exploration is difficult. In order to clarify the potential direction of key fields in Shengli exploration area and guide the optimization of the following oil and gas exploration deployment order， the next potential directions of each key field were analyzed on the basis of systematic summary of the exploration research progress of the sedimentation， reservoir， oil source correlation， transport system， hydrocarbon accumulation mode， as well as oil and gas enrichment control factors in the ultra-denudation zone field in the western margin of Junggar Basin，the deep field of the upper combination in the central area of Junggar Basin， the ultra-deep field of the lower combination in the central area of Junggar Basin， and the piedmont zone field in the northern margin and southeastern areas of Junggar Basin. The results show that the Jurassic-Cretaceous in Hashan area， the Neogene Shawan Formation in Chepaizi area， and the Carboniferous in Chepaizi area in the ultra-denudation zone in the western margin of the Junggar Basin， as well as the Jurassic Qigu Formation in Yongjin-Zhengshacun area and the Jurassic Sangonghe Formation in Moxizhuang area in the deep area of the upper combination in the central area of the Junggar Basin， are the main positions for increasing reserves and production in the future. The Permian Upper Wuerhe Formation-Triassic Karamay Formation in Well Zheng 10 area of Shawan Sag in the ultra-deep area of the lower combination in the central area of the Junggar Basin and the Permian Fengcheng Formation-Xiazijie Formation in Well Zhuangshen 1 area of the western sag of Well Pen 1 are the next important replacement positions. The parautochthonous nappe systems of the Hashan piedmont zone in the northern margin of the Junggar Basin and the southern and northern piedmont zones of Bogda Mountain in the southeastern margin of the Junggar Basin are the favorable positions to be explored continuously in the next step. The unconventional shale gas field in the deep Carboniferous strata of Shibei Sag and Shiqiantan Sag is a reserve position that needs to be actively prepared in the future. During the“ 14th-15th Five Year Planin 2021-2030” period， Shengli exploration area should be guided by the exploration concept of“ focusing on the whole area， successfully exploring deep layers， emphasizing both conventional and unconventional oil and gas， and implementing coordinated promotion” and continuously and orderly promote exploration in various key fields of the basin.
2024, 31(4):42-59.
DOI: 10.13673/j.pgre.202405018
Abstract:
The exploration area of Shengli Oilfield was studied， and the difference in geological characteristics of shale oil in continental lake basins in eastern and western China and its influence on the enrichment law were systematically compared. Controlled by paleogeomorphology， paleoclimate， paleowater medium， and other factors in Eocene The Upper Submember of 4th Member of Eocene Shahejie Formation （E s4 U）-The Lower Submember of 3rd Member of Eocene Shahejie Formation （E s3 L ） of Jiyang Depression，the organic-rich lamellar carbonate shale was widely distributed. The synergistic evolution of hydrocarbon generation of organic-rich clay lamina and reservoir formation of carbonate-rich lamina provided favorable conditions for the large-scale enrichment of free hydrocarbons.The strong rifting of Fengcheng Formation in Hashan area in the northwest margin of Junggar Basin led to strong volcanic activity. Under the combined influence of volcanic eruption materials and paleoclimate， large-scale distribution of organic-rich lamellar alkali-bearing felsic shale lithofacies was observed. More felsic minerals were formed during the evolution of hydrocarbon generation and reservoir formation，accompanied by a large number of matrix dissolution pores and intercrystalline pores，which laid an essential foundation for shale oil enrichment. In the process of multi-stage thrusting in Hashan area，the quasi-in-situ system continued to generate hydrocarbons， with more oil and less gas. The relatively good storage conditions，as well as abnormal high pressure caused by structural overburden pressure and pressurization due to hydrocarbon generation， provide necessary conditions for high shale oil production. Under the background of salt water in Haiji Lake， Lucaogou Formation in the southeastern margin of Junggar Basin was affected by volcanic debris and microorganisms to form the primary lithofacies combination type of organic-rich lamellar shale and organic-poor interlayer dolomite. The organic-rich shale of Lucaogou Formation in the piedmont zone around Bogda Mountain has entered the mature evolution stage， and the structural stability area in the exploration area of Shengli Oilfield was a potential area for shale oil exploration.
The exploration area of Shengli Oilfield was studied， and the difference in geological characteristics of shale oil in continental lake basins in eastern and western China and its influence on the enrichment law were systematically compared. Controlled by paleogeomorphology， paleoclimate， paleowater medium， and other factors in Eocene The Upper Submember of 4th Member of Eocene Shahejie Formation （E s4 U）-The Lower Submember of 3rd Member of Eocene Shahejie Formation （E s3 L ） of Jiyang Depression，the organic-rich lamellar carbonate shale was widely distributed. The synergistic evolution of hydrocarbon generation of organic-rich clay lamina and reservoir formation of carbonate-rich lamina provided favorable conditions for the large-scale enrichment of free hydrocarbons.The strong rifting of Fengcheng Formation in Hashan area in the northwest margin of Junggar Basin led to strong volcanic activity. Under the combined influence of volcanic eruption materials and paleoclimate， large-scale distribution of organic-rich lamellar alkali-bearing felsic shale lithofacies was observed. More felsic minerals were formed during the evolution of hydrocarbon generation and reservoir formation，accompanied by a large number of matrix dissolution pores and intercrystalline pores，which laid an essential foundation for shale oil enrichment. In the process of multi-stage thrusting in Hashan area，the quasi-in-situ system continued to generate hydrocarbons， with more oil and less gas. The relatively good storage conditions，as well as abnormal high pressure caused by structural overburden pressure and pressurization due to hydrocarbon generation， provide necessary conditions for high shale oil production. Under the background of salt water in Haiji Lake， Lucaogou Formation in the southeastern margin of Junggar Basin was affected by volcanic debris and microorganisms to form the primary lithofacies combination type of organic-rich lamellar shale and organic-poor interlayer dolomite. The organic-rich shale of Lucaogou Formation in the piedmont zone around Bogda Mountain has entered the mature evolution stage， and the structural stability area in the exploration area of Shengli Oilfield was a potential area for shale oil exploration.
LI Junliang
,
LIU Huimin
,
WANG Yong
,
ZHANG Kuihua
,
ZHOU Guangqing
,
LI Zheng
,
WANG Weiqing
,
FANG Zhengwei
,
ZHANG Shun
,
LIU Xinjin
,
LIU Peng
,
ZHANG Zilin
,
WEI Xiaoliang
2024, 31(4):60-72.
DOI: 10.13673/j.pgre.202405007
Abstract:
Shale oil in Jiyang continental faulted basin is a realistic new field for subsequent resource， with enormous exploration potential. It is an important resource base for the sustainable development of Shengli Oilfield. The results of geological research and exploration of shale oil were analyzed in Jiyang continental faulted basin in recent years， and the new progress was systematically reviewed in shale sedimentation， reservoir formation， hydrocarbon generation， shale oil enrichment theory， and supporting fracturing stimulation technologies for Jiyang continental faulted basin. The results show that ① A shale lithofacies classification scheme is proposed based on mineral composition， sedimentary structure， crystallization， and abundance of organic matter ， which can be summarized as“ four elements and three ends.” The mechanism of“ four paleo-environment factors control shale lithofacies” is revealed，and the orderly“ ring-shaped” distribution of shale lithofacies is confirmed. ② The core micro/nano CT scanning， argon ion polishing scanning electron microscopy， FIB-FESEM， nuclear magnetic resonance freeze-thaw， and small-angle X-ray scattering are integrated to form the quantitative characterization technologies of multi-scale shale pore and fracture systems. It is clear that the spaces of the shale reservoir in Jiyang continental faulted basin are divided into both pores and fractures， mainly inorganic pores and fractures. It is revealed that calcite recrystallization， dissolution， and conversion from illite/smectite to illite are the most critical reservoir formation mechanisms， and a reservoir model of shale pore and fracture network is established. ③ The oil content evaluation method of organic-rich shale is developed， which reveals the characteristics of high paleo-productivity， early generation， and early enrichment of organic-rich shale in the saline lake basin. The shale oil resources in Jiyang continental faulted basin are estimated to be more than 1010 t. ④ The shale oil enrichment is controlled by the spatiotemporal coupling of hydrocarbon generation and reservoir formation of bedded/laminated shale， which is characterized by“ early formation of saline source rock， inorganic pore， and fracture reservoirs， microscopic source-reservoir integration， and dual coupling enrichment.” ⑤ The comprehensive evaluation system and target selection process for shale oil exploration in continental faulted basins are established， which involves four characteristics and four determinations. ⑥ The fracturing stimulation technologies are developed of“ combined fracture network fracturing”and“ horizontal well multistage fracturing” suitable for Jiyang continental faulted basin. According to the actual situation of Shengli Oilfield， the exploration idea is proposed of“ increasing storage and production in main subsags， exploring new positions in small oil-rich subsags， implementing resources in peripheral small subsags， and taking into account the optimization of mineral rights，”to orderly promote the large-scale increase in storage and production of shale oil in Jiyang continental faulted basin. The relevant achievements and supporting technologies are significant for shale oil exploration and development in similar oilfields.
Shale oil in Jiyang continental faulted basin is a realistic new field for subsequent resource， with enormous exploration potential. It is an important resource base for the sustainable development of Shengli Oilfield. The results of geological research and exploration of shale oil were analyzed in Jiyang continental faulted basin in recent years， and the new progress was systematically reviewed in shale sedimentation， reservoir formation， hydrocarbon generation， shale oil enrichment theory， and supporting fracturing stimulation technologies for Jiyang continental faulted basin. The results show that ① A shale lithofacies classification scheme is proposed based on mineral composition， sedimentary structure， crystallization， and abundance of organic matter ， which can be summarized as“ four elements and three ends.” The mechanism of“ four paleo-environment factors control shale lithofacies” is revealed，and the orderly“ ring-shaped” distribution of shale lithofacies is confirmed. ② The core micro/nano CT scanning， argon ion polishing scanning electron microscopy， FIB-FESEM， nuclear magnetic resonance freeze-thaw， and small-angle X-ray scattering are integrated to form the quantitative characterization technologies of multi-scale shale pore and fracture systems. It is clear that the spaces of the shale reservoir in Jiyang continental faulted basin are divided into both pores and fractures， mainly inorganic pores and fractures. It is revealed that calcite recrystallization， dissolution， and conversion from illite/smectite to illite are the most critical reservoir formation mechanisms， and a reservoir model of shale pore and fracture network is established. ③ The oil content evaluation method of organic-rich shale is developed， which reveals the characteristics of high paleo-productivity， early generation， and early enrichment of organic-rich shale in the saline lake basin. The shale oil resources in Jiyang continental faulted basin are estimated to be more than 1010 t. ④ The shale oil enrichment is controlled by the spatiotemporal coupling of hydrocarbon generation and reservoir formation of bedded/laminated shale， which is characterized by“ early formation of saline source rock， inorganic pore， and fracture reservoirs， microscopic source-reservoir integration， and dual coupling enrichment.” ⑤ The comprehensive evaluation system and target selection process for shale oil exploration in continental faulted basins are established， which involves four characteristics and four determinations. ⑥ The fracturing stimulation technologies are developed of“ combined fracture network fracturing”and“ horizontal well multistage fracturing” suitable for Jiyang continental faulted basin. According to the actual situation of Shengli Oilfield， the exploration idea is proposed of“ increasing storage and production in main subsags， exploring new positions in small oil-rich subsags， implementing resources in peripheral small subsags， and taking into account the optimization of mineral rights，”to orderly promote the large-scale increase in storage and production of shale oil in Jiyang continental faulted basin. The relevant achievements and supporting technologies are significant for shale oil exploration and development in similar oilfields.
2024, 31(4):73-83.
DOI: 10.13673/j.pgre.202405006
Abstract:
In response to the strong multi-solution problem of conventional seismic exploration methods in geological sweet spot prediction of shale， this paper fully explored one-dimensional whole rock analysis data and well logging data， two-dimensional geological data， three-dimensional post-stack seismic data， and five-dimensional offset vector tile （OVT） orientation information. In addition， the paper researched geological sweet spot identification technology of shale based on fuzzy fusion prediction to improve the accuracy of geological sweet spot prediction of shale. Firstly， the approximate distribution direction of faults in the study area and the distribution area of favorable shale lithofacies were statistically analyzed， and the sensitive azimuthal section was selected to stack the OVT data based on azimuth. Then， the fractures on the plane were analyzed based on pre-stack preferred azimuth， and the two-dimensional prediction of favorable shale lithofacies was carried out using a feedforward neural network. Finally， a fuzzy fusion technology based on an improved Sigmoid and Takagi-Sugeno （TS） function was developed， which could weigh the significance of controlling factors in geological sweet spot identification of shale according to their degree of influence and effectively integrate the predicted results of azimuthal anisotropy fractures on the plane with those of neural network-based shale lithofacies，so as to realize decision-making integration for identifying geological sweet spots of shale. This technology has been applied in the classification and grading evaluation of geological sweet spots of shale in the Lower Submember of the 3 rd Member of Shahejie formation （Es3U） in Bonan Depression. Areas with poorly developed fractures and unfavorable lithofacies that could interfere with the analysis of geological sweet spots of shale were filtered out. Based on the predictions of fractures and lithofacies， The geological sweet spots of shale in the study area were categorized into three classes. The areas characterized by the superposition of developed fractures and favorable lithofacies were classified as sweet spots of Class I， which showed a high degree of consistency with actual drilling results and achieved notable application effects. The research results indicate that the classification and grading evaluation can be achieved using the geological sweet spot identification technology of shale based on fuzzy fusion prediction， which improves prediction reliability and provides reliable technical support for shale oil exploration.
In response to the strong multi-solution problem of conventional seismic exploration methods in geological sweet spot prediction of shale， this paper fully explored one-dimensional whole rock analysis data and well logging data， two-dimensional geological data， three-dimensional post-stack seismic data， and five-dimensional offset vector tile （OVT） orientation information. In addition， the paper researched geological sweet spot identification technology of shale based on fuzzy fusion prediction to improve the accuracy of geological sweet spot prediction of shale. Firstly， the approximate distribution direction of faults in the study area and the distribution area of favorable shale lithofacies were statistically analyzed， and the sensitive azimuthal section was selected to stack the OVT data based on azimuth. Then， the fractures on the plane were analyzed based on pre-stack preferred azimuth， and the two-dimensional prediction of favorable shale lithofacies was carried out using a feedforward neural network. Finally， a fuzzy fusion technology based on an improved Sigmoid and Takagi-Sugeno （TS） function was developed， which could weigh the significance of controlling factors in geological sweet spot identification of shale according to their degree of influence and effectively integrate the predicted results of azimuthal anisotropy fractures on the plane with those of neural network-based shale lithofacies，so as to realize decision-making integration for identifying geological sweet spots of shale. This technology has been applied in the classification and grading evaluation of geological sweet spots of shale in the Lower Submember of the 3 rd Member of Shahejie formation （Es3U） in Bonan Depression. Areas with poorly developed fractures and unfavorable lithofacies that could interfere with the analysis of geological sweet spots of shale were filtered out. Based on the predictions of fractures and lithofacies， The geological sweet spots of shale in the study area were categorized into three classes. The areas characterized by the superposition of developed fractures and favorable lithofacies were classified as sweet spots of Class I， which showed a high degree of consistency with actual drilling results and achieved notable application effects. The research results indicate that the classification and grading evaluation can be achieved using the geological sweet spot identification technology of shale based on fuzzy fusion prediction， which improves prediction reliability and provides reliable technical support for shale oil exploration.
2024, 31(4):84-95.
DOI: 10.13673/j.pgre.202405070
Abstract:
The occurrence characteristics and mobility are essential aspects of shale oil evaluation，as well as exploration and development.However， there are still significant challenges in characterizing the occurrence characteristics and mobility of shale oil due to the strong heterogeneity，as well as the complex pore structure and fluid properties of shale. New research methods and experimental techniques have emerged in recent years with the intensifying exploration and development of shale oil in China and abroad.Therefore，progress in research methods and experimental techniques were summarized for evaluating shale oil occurrence characteristics and mobility， and issues were proposed that need to be considered in the research on shale oil occurrence characteristics and mobility. The most direct method for qualitative evaluation of shale oil occurrence characteristics is the advanced high-resolution imaging techniques for image observation among existing techniques. The oil saturation index method and classification evaluation method based on statistical analysis have advantages in evaluating shale oil mobility in mature exploration areas. At present， the multi-temperature stage pyrolysis parameter method is a fast and efficient method to characterize the shale oil quantity in different occurrence states quantitatively，and it has a good application prospect in the evaluation of shale oil content，shale oil mobility，and resource quantity. The following issues should be fully considered while studying the occurrence characteristics and mobility of shale oil in the future：① developing highly simulated shale oil enrichment，flow，and development simulation experiments to ensure similarity between experimental conditions and underground geological conditions；② conducting microscopic flow experiments of micro- and nano-scale shale oil to explore the microscopic flow mechanism and control factors of shale oil；③ dissecting the differences in occurrence characteristics and mobility of shale oil in different basic thin layers， as well as the contributions of different basic thin layers to shale oil content and mobility； ④ combining the microscopic occurrence form， fluid mechanism， and macroscopic geological parameters of shale oil to determine and evaluate the macroscopic geological conditions and parameters.
The occurrence characteristics and mobility are essential aspects of shale oil evaluation，as well as exploration and development.However， there are still significant challenges in characterizing the occurrence characteristics and mobility of shale oil due to the strong heterogeneity，as well as the complex pore structure and fluid properties of shale. New research methods and experimental techniques have emerged in recent years with the intensifying exploration and development of shale oil in China and abroad.Therefore，progress in research methods and experimental techniques were summarized for evaluating shale oil occurrence characteristics and mobility， and issues were proposed that need to be considered in the research on shale oil occurrence characteristics and mobility. The most direct method for qualitative evaluation of shale oil occurrence characteristics is the advanced high-resolution imaging techniques for image observation among existing techniques. The oil saturation index method and classification evaluation method based on statistical analysis have advantages in evaluating shale oil mobility in mature exploration areas. At present， the multi-temperature stage pyrolysis parameter method is a fast and efficient method to characterize the shale oil quantity in different occurrence states quantitatively，and it has a good application prospect in the evaluation of shale oil content，shale oil mobility，and resource quantity. The following issues should be fully considered while studying the occurrence characteristics and mobility of shale oil in the future：① developing highly simulated shale oil enrichment，flow，and development simulation experiments to ensure similarity between experimental conditions and underground geological conditions；② conducting microscopic flow experiments of micro- and nano-scale shale oil to explore the microscopic flow mechanism and control factors of shale oil；③ dissecting the differences in occurrence characteristics and mobility of shale oil in different basic thin layers， as well as the contributions of different basic thin layers to shale oil content and mobility； ④ combining the microscopic occurrence form， fluid mechanism， and macroscopic geological parameters of shale oil to determine and evaluate the macroscopic geological conditions and parameters.
2024, 31(4):96-111.
DOI: 10.13673/j.pgre.202405023
Abstract:
The Carboniferous and Permian are important coal-bearing strata in North China， which develop various oil and gas resources such as coalbed methane， coal-bearing shale gas， tight coal-bearing sandstone gas， and coal-formed oil. Massive research and exploration results have shown that coal-bearing strata have good exploration prospects. Compared with those of the Ordos Basin，the exploration and research levels of the Carboniferous and Permian coal-bearing strata in Jiyang-Linqing area are relatively lower. The reservoir formation conditions of coal-bearing strata in Jiyang-Linqing area and Ordos Basin were comparatively analyzed，and the exploration directions for coal-bearing strata in Jiyang-Linqing area were proposed based on systematically summarizing the research progress of oil and gas resource types and enrichment conditions in coal-bearing strata in North China. The research results show that the coal-bearing strata in North China are mainly composed of Taiyuan Formation and Shanxi Formation， formed in the sedimentary environment of the epeiric sea delta. They have strong cyclicity and are developed into symbiotic coalbed methane reservoirs， coal-bearing shale gas reservoirs， and tight coal-bearing sandstone gas reservoirs. Coal， carbonaceous mudstones， and dark mudstones with high organic carbon content are the material basis for the formation of coal-bearing oil and gas resources，and coal-bearing source rock development areas with rich hydrogen have certain exploration potential for coal-formed oil.Preservation conditions are key factors for the enrichment of coalbed methane and coal-bearing shale gas. The high porosity and permeability zones caused by sedimentation and diagenesis are the sweet spot areas for tight coal-bearing sandstone gas. There are good exploration prospects for coal-bearing gas and coal-formed oil in Jiyang-Linqing area. Conducting a systematic evaluation by exploring a set of lithological combinations is an essential technical approach to improving the exploration efficiency of coal-bearing strata. The favorable exploration targets are Taiyuan Formation on the south slope of Dongying Sag and Huimin Sag， the western part of Chezhen Sag， and the Gubei buried hills.
The Carboniferous and Permian are important coal-bearing strata in North China， which develop various oil and gas resources such as coalbed methane， coal-bearing shale gas， tight coal-bearing sandstone gas， and coal-formed oil. Massive research and exploration results have shown that coal-bearing strata have good exploration prospects. Compared with those of the Ordos Basin，the exploration and research levels of the Carboniferous and Permian coal-bearing strata in Jiyang-Linqing area are relatively lower. The reservoir formation conditions of coal-bearing strata in Jiyang-Linqing area and Ordos Basin were comparatively analyzed，and the exploration directions for coal-bearing strata in Jiyang-Linqing area were proposed based on systematically summarizing the research progress of oil and gas resource types and enrichment conditions in coal-bearing strata in North China. The research results show that the coal-bearing strata in North China are mainly composed of Taiyuan Formation and Shanxi Formation， formed in the sedimentary environment of the epeiric sea delta. They have strong cyclicity and are developed into symbiotic coalbed methane reservoirs， coal-bearing shale gas reservoirs， and tight coal-bearing sandstone gas reservoirs. Coal， carbonaceous mudstones， and dark mudstones with high organic carbon content are the material basis for the formation of coal-bearing oil and gas resources，and coal-bearing source rock development areas with rich hydrogen have certain exploration potential for coal-formed oil.Preservation conditions are key factors for the enrichment of coalbed methane and coal-bearing shale gas. The high porosity and permeability zones caused by sedimentation and diagenesis are the sweet spot areas for tight coal-bearing sandstone gas. There are good exploration prospects for coal-bearing gas and coal-formed oil in Jiyang-Linqing area. Conducting a systematic evaluation by exploring a set of lithological combinations is an essential technical approach to improving the exploration efficiency of coal-bearing strata. The favorable exploration targets are Taiyuan Formation on the south slope of Dongying Sag and Huimin Sag， the western part of Chezhen Sag， and the Gubei buried hills.
2024, 31(4):112-124.
DOI: 10.13673/j.pgre.202405015
Abstract:
Jiyang Depression is rich in petroleum resources. However， as the exploration degree intensifies， the exploration difficulty of the Paleogene conventional petroleum reservoirs is increasing. Therefore， exploring new fields and ensuring the effective supplement of resources is urgent. The strata in Jiyang Depression is well developed， and the pre-Paleogene buried hill is widely distributed，with a great thickness and significant exploration potential. However， the exploration results are unsatisfactory due to the early formation of deep buried hills， complex geological evolution history， and poor quality of deep seismic data. In recent years，with continuous breakthroughs in experimental technologies， deepening research on basic geology， and massive seismic data processing methods， the exploration of buried hills has yielded many promising leads. This has led to an understanding of petroleum exploration in buried hills characterized by multiple periods of structures contributing to hills， multiple sets of source rocks supplying hydrocarbons in conjunction， multi-element control of advantageous reservoir formation， and various modes of orderly controlling the reservoir. The risk direction and exploration targets for deep buried hills were clarified， and the ways for further petroleum potential exploration in Jiyang Depression were pointed out through an in-depth dissection of the discovered reservoirs，coupled with the exploration experience of neighboring areas. Specifically， the risk exploration directions for each stratum were as follows：faultfractured bodies，fault-dissolved bodies， and other enclosures within the buried hills of the Archean； concealed fault block traps and internal grain beaches， as well as lithologic traps formed by layer-following dissolution of the lower Paleozoic； deep coalmeasure gas reservoirs with a burial depth of greater than 2 000 meters of the upper Paleozoic； lithologic traps controlled by fractures and sand bodies of the Mesozoic.
Jiyang Depression is rich in petroleum resources. However， as the exploration degree intensifies， the exploration difficulty of the Paleogene conventional petroleum reservoirs is increasing. Therefore， exploring new fields and ensuring the effective supplement of resources is urgent. The strata in Jiyang Depression is well developed， and the pre-Paleogene buried hill is widely distributed，with a great thickness and significant exploration potential. However， the exploration results are unsatisfactory due to the early formation of deep buried hills， complex geological evolution history， and poor quality of deep seismic data. In recent years，with continuous breakthroughs in experimental technologies， deepening research on basic geology， and massive seismic data processing methods， the exploration of buried hills has yielded many promising leads. This has led to an understanding of petroleum exploration in buried hills characterized by multiple periods of structures contributing to hills， multiple sets of source rocks supplying hydrocarbons in conjunction， multi-element control of advantageous reservoir formation， and various modes of orderly controlling the reservoir. The risk direction and exploration targets for deep buried hills were clarified， and the ways for further petroleum potential exploration in Jiyang Depression were pointed out through an in-depth dissection of the discovered reservoirs，coupled with the exploration experience of neighboring areas. Specifically， the risk exploration directions for each stratum were as follows：faultfractured bodies，fault-dissolved bodies， and other enclosures within the buried hills of the Archean； concealed fault block traps and internal grain beaches， as well as lithologic traps formed by layer-following dissolution of the lower Paleozoic； deep coalmeasure gas reservoirs with a burial depth of greater than 2 000 meters of the upper Paleozoic； lithologic traps controlled by fractures and sand bodies of the Mesozoic.
2024, 31(4):125-134.
DOI: 10.13673/j.pgre.202405008
Abstract:
The conventional petroleum field in Jiyang Depression has always been the main battlefield of exploration and development in Shengli Oilfield. It has experienced more than 60 years of exploration and development and entered the mature exploration stage as a whole，but it still has a relatively large scale of reserve increase every year，which is not consistent with the traditional growth trend of proven petroleum-in-place in oil and gas-bearing basins. The critical issues concerning the exploration decisions of Shengli Oilfield need to be clarified urgently，including the growth law of the conventional proven petroleum-in-place in Jiyang Depression，the strong trend of reserve increase，and the main fields for reserve increase. By analyzing the exploration process of Jiyang Depression，the geological characteristics，resource conditions， exploration investment， theory and technology，resource sequence，and other exploration elements were analyzed，revealing the exploration discovery law of conventional petroleum in Jiyang Depression. The broom-shaped model prediction method and proven rate method of resource were used to predict the growth trend of conventional proven petroleum-in-place. The scale and favorable direction of future reserve increase of conventional petroleum in Jiyang Depression were clarified by analyzing the main fields with reserve increase. The results show that the complex geological characteristics of Jiyang Depression and the relatively abundant remaining resources determine the diversity of exploration objects，the tortuosity of the exploration process， and the long-term nature of exploration history. The conventional petroleum in Jiyang Depression can still maintain a long period of stable reserve increase under conditions of ensuring a relatively stable exploration investment，continuing to innovate the exploration theory and key technologies， and maintaining a relatively reasonable resource sequence.Jiyang Depression can still produce about 2.5 × 108t of conventional proven petroleum-in-place in the next 10 years under the current economic and technical conditions and the relative guarantee of exploration investment. It is pointed out that the Neogene river sandstone reservoir， lithologic oil and gas reservoirs in the Upper Submember of the 4th Member of the Eocene Shahejie Formation（Es4U）-the Lower 3rd Member of the Eocene Shahejie Formation（Es4L）， and other mature fields are still the ballast stones for stable reserve increase. Kongdian Formation-the deep field of the Lower Submember of the 4th Member of the Eocene Shahejie Formation（Es4L） is an essential field for large-scale reserve increase，and the pre-Paleogene buried hill is a favorable direction for the petroleum enrichment and high yield. In the future， the exploration progress in the unconventional and new energy fields should be closely tracked， and the research results of the growth law and the reserve increase trend of conventional proven petroleum-in-place in Jiyang Depression should be constantly improved and revised to make them more conform to the development trend of oilfield exploration and guide the oilfield exploration decisions.
The conventional petroleum field in Jiyang Depression has always been the main battlefield of exploration and development in Shengli Oilfield. It has experienced more than 60 years of exploration and development and entered the mature exploration stage as a whole，but it still has a relatively large scale of reserve increase every year，which is not consistent with the traditional growth trend of proven petroleum-in-place in oil and gas-bearing basins. The critical issues concerning the exploration decisions of Shengli Oilfield need to be clarified urgently，including the growth law of the conventional proven petroleum-in-place in Jiyang Depression，the strong trend of reserve increase，and the main fields for reserve increase. By analyzing the exploration process of Jiyang Depression，the geological characteristics，resource conditions， exploration investment， theory and technology，resource sequence，and other exploration elements were analyzed，revealing the exploration discovery law of conventional petroleum in Jiyang Depression. The broom-shaped model prediction method and proven rate method of resource were used to predict the growth trend of conventional proven petroleum-in-place. The scale and favorable direction of future reserve increase of conventional petroleum in Jiyang Depression were clarified by analyzing the main fields with reserve increase. The results show that the complex geological characteristics of Jiyang Depression and the relatively abundant remaining resources determine the diversity of exploration objects，the tortuosity of the exploration process， and the long-term nature of exploration history. The conventional petroleum in Jiyang Depression can still maintain a long period of stable reserve increase under conditions of ensuring a relatively stable exploration investment，continuing to innovate the exploration theory and key technologies， and maintaining a relatively reasonable resource sequence.Jiyang Depression can still produce about 2.5 × 108t of conventional proven petroleum-in-place in the next 10 years under the current economic and technical conditions and the relative guarantee of exploration investment. It is pointed out that the Neogene river sandstone reservoir， lithologic oil and gas reservoirs in the Upper Submember of the 4th Member of the Eocene Shahejie Formation（Es4U）-the Lower 3rd Member of the Eocene Shahejie Formation（Es4L）， and other mature fields are still the ballast stones for stable reserve increase. Kongdian Formation-the deep field of the Lower Submember of the 4th Member of the Eocene Shahejie Formation（Es4L） is an essential field for large-scale reserve increase，and the pre-Paleogene buried hill is a favorable direction for the petroleum enrichment and high yield. In the future， the exploration progress in the unconventional and new energy fields should be closely tracked， and the research results of the growth law and the reserve increase trend of conventional proven petroleum-in-place in Jiyang Depression should be constantly improved and revised to make them more conform to the development trend of oilfield exploration and guide the oilfield exploration decisions.
2024, 31(4):135-153.
DOI: 10.13673/j.pgre.202405009
Abstract:
Oil and gas reservoir modeling integrates multidisciplinary information from logging， geology， and seismic data through geostatistics and other methods， and it is a powerful tool for oil and gas field development. The geological model of reservoirs can quantitatively characterize the variation and distribution of various geological features of the reservoir in three-dimensional space and is a high generalization of the type， geometry， scale， internal structure of the oil and gas reservoir， reservoir parameters， and fluid distribution. The geological model of reservoirs is the core of the geological model of oil and gas reservoirs， which can comprehensively characterize the sedimentary characteristics， heterogeneity， physical properties， and fluid characteristics. However， it is difficult to characterize reservoir distribution under the condition of a large-scale sedimentary system and sparse well pattern in the exploration stage， covering ① quantitative representation of geological knowledge， including how to represent the experience of geological experts digitally； ② it is impossible to accurately and quantitatively describe the development scale， distribution direction，and structural characteristics of geological bodies directly with logging data and construct geological models under the condition of sparse well pattern， and complex sedimentary systems in large-scale space cannot be characterized by simple mathematical functions； ③ traditional geostatistics and other methods can not realize the fusion of seismic， logging， geological， reservoir， and other multi-dimensional data in the construction of exploration model. Therefore， the theory and technology of reservoir modeling based on deterministic modeling and stochastic modeling， such as traditional geostatistics， have met great challenges. On the basis of systematic analysis of traditional reservoir modeling technology processes and methods， the authors constructed a multidisciplinary big data knowledge base of geoscience covering geology， logging， seismic， analytical， and laboratory information and carried out the characterization of the sedimentary facies pattern library by hierarchical clustering through multi-dimensional data condensation and the intelligent modeling based on the generation network. In addition， a multidisciplinary collaborative modeling technology strategy and system are proposed for oil and gas reservoir exploration， which quantitatively characterized the matching relationship among structure， sediment， and reservoir. This technology system has been systematically applied in the exploration and deployment of steep slope and subsag belts in the north of Dongying Sag， and the geological models of lithofacies， physical properties，and oil and gas migration and accumulation has been constructed， which integrates multiple information such as paleogeomorphology，paleoprovenance， transport channels， logging， and seismic attributes. Based on the new paradigm of the model， the deployment of well locations has been guided， and the exploration practice of complex glutenites and shale oil in continental faulted basins has been supported. The authors further discuss the development trend and application prospect of oil and gas reservoir exploration and modeling technology in the future by deeply analyzing the practical difficulties and accuracy of exploration and modeling in the north belt of Dongying Sag.
Oil and gas reservoir modeling integrates multidisciplinary information from logging， geology， and seismic data through geostatistics and other methods， and it is a powerful tool for oil and gas field development. The geological model of reservoirs can quantitatively characterize the variation and distribution of various geological features of the reservoir in three-dimensional space and is a high generalization of the type， geometry， scale， internal structure of the oil and gas reservoir， reservoir parameters， and fluid distribution. The geological model of reservoirs is the core of the geological model of oil and gas reservoirs， which can comprehensively characterize the sedimentary characteristics， heterogeneity， physical properties， and fluid characteristics. However， it is difficult to characterize reservoir distribution under the condition of a large-scale sedimentary system and sparse well pattern in the exploration stage， covering ① quantitative representation of geological knowledge， including how to represent the experience of geological experts digitally； ② it is impossible to accurately and quantitatively describe the development scale， distribution direction，and structural characteristics of geological bodies directly with logging data and construct geological models under the condition of sparse well pattern， and complex sedimentary systems in large-scale space cannot be characterized by simple mathematical functions； ③ traditional geostatistics and other methods can not realize the fusion of seismic， logging， geological， reservoir， and other multi-dimensional data in the construction of exploration model. Therefore， the theory and technology of reservoir modeling based on deterministic modeling and stochastic modeling， such as traditional geostatistics， have met great challenges. On the basis of systematic analysis of traditional reservoir modeling technology processes and methods， the authors constructed a multidisciplinary big data knowledge base of geoscience covering geology， logging， seismic， analytical， and laboratory information and carried out the characterization of the sedimentary facies pattern library by hierarchical clustering through multi-dimensional data condensation and the intelligent modeling based on the generation network. In addition， a multidisciplinary collaborative modeling technology strategy and system are proposed for oil and gas reservoir exploration， which quantitatively characterized the matching relationship among structure， sediment， and reservoir. This technology system has been systematically applied in the exploration and deployment of steep slope and subsag belts in the north of Dongying Sag， and the geological models of lithofacies， physical properties，and oil and gas migration and accumulation has been constructed， which integrates multiple information such as paleogeomorphology，paleoprovenance， transport channels， logging， and seismic attributes. Based on the new paradigm of the model， the deployment of well locations has been guided， and the exploration practice of complex glutenites and shale oil in continental faulted basins has been supported. The authors further discuss the development trend and application prospect of oil and gas reservoir exploration and modeling technology in the future by deeply analyzing the practical difficulties and accuracy of exploration and modeling in the north belt of Dongying Sag.
2024, 31(4):154-163.
DOI: 10.13673/j.pgre.202312011
Abstract:
Deep source rocks undergo high degrees of evolution， leading to a significant decrease in biomarker content in crude oil as maturity increases. The decrease affects the reliability of the oil source correlation with conventional biomarker parameters. To better use the δ13CPDB value for identifying deep crude oil sources， authors analyzed the δ13CPDB values of four group components in the soluble organic matter from naturally evolved source rock profiles in Dongying Sag， Jiyang Depression， Bohaiwan Basin and the products of physical experiments on hydrocarbon generation and expulsion. Considering the relative content of alkane， authors discussed the carbon isotope fractionation effects in the crude oil from deep source rock. Additionally， authors proposed the working thought and procedure for identifying the source of deep oil with the δ13CPDB values. The carbon isotope fractionation effects resulting from high thermal maturity are obvious in deep source rocks. The δ13CPDB values of the four group components of soluble organic matter from source rocks （alkane， aromatics， non-hydrocarbon， and asphaltene） exhibit a significant elevation with increasing burial depth. Specifically， the δ13CPDB values of alkane exhibit the most pronounced change， exceeding 5‰， while aromatics show a change of around 4‰. The changes in the δ13CPDB value of non-hydrocarbon and asphaltene are relatively small， ranging from 2‰ to 3‰. As burial depth increases， the alkane contents in soluble organic matter increase from around 40% to over 80%. Correspondingly，the δ13CPDB values of alkane increase from around ?30‰ to over ?24‰， and the alkane contents show a great correlation with the variations of its δ13CPDB values. Similar results can also be observed from the δ13CPDB values of group components from physical experiments on hydrocarbon generation with the same type of source rock samples. In these experiments， the variations in the δ13CPDB values of alkane can reach 4‰， while those in aromatics， non-hydrocarbon， and asphaltene are relatively low， ranging from 1‰ to 3‰. When utilizing carbon isotopes to identify the source of deep oil， it is essential to first check the correlation between alkane contents and their δ13CPDB values to identify if the carbon isotope fractionation effects derived from thermal maturation exists.Subsequently， the δ13CPDB values of alkane should be properly recovered before utilizing it to identify the source of the oil. According to the abovementioned methods， authors identified the source of light oil from Chepaizi Uplift in the Western region of Junggar Basin. It confirmed the presence of carbon isotope fractionation effects in the light oil derived from thermal evolution. It shows a great possibility that the light oil is sourced from the underlying high-maturity source rock of the Permian， which is of important practical significance in the evaluation and deployment of the petroleum exploration target in this area.
Deep source rocks undergo high degrees of evolution， leading to a significant decrease in biomarker content in crude oil as maturity increases. The decrease affects the reliability of the oil source correlation with conventional biomarker parameters. To better use the δ13CPDB value for identifying deep crude oil sources， authors analyzed the δ13CPDB values of four group components in the soluble organic matter from naturally evolved source rock profiles in Dongying Sag， Jiyang Depression， Bohaiwan Basin and the products of physical experiments on hydrocarbon generation and expulsion. Considering the relative content of alkane， authors discussed the carbon isotope fractionation effects in the crude oil from deep source rock. Additionally， authors proposed the working thought and procedure for identifying the source of deep oil with the δ13CPDB values. The carbon isotope fractionation effects resulting from high thermal maturity are obvious in deep source rocks. The δ13CPDB values of the four group components of soluble organic matter from source rocks （alkane， aromatics， non-hydrocarbon， and asphaltene） exhibit a significant elevation with increasing burial depth. Specifically， the δ13CPDB values of alkane exhibit the most pronounced change， exceeding 5‰， while aromatics show a change of around 4‰. The changes in the δ13CPDB value of non-hydrocarbon and asphaltene are relatively small， ranging from 2‰ to 3‰. As burial depth increases， the alkane contents in soluble organic matter increase from around 40% to over 80%. Correspondingly，the δ13CPDB values of alkane increase from around ?30‰ to over ?24‰， and the alkane contents show a great correlation with the variations of its δ13CPDB values. Similar results can also be observed from the δ13CPDB values of group components from physical experiments on hydrocarbon generation with the same type of source rock samples. In these experiments， the variations in the δ13CPDB values of alkane can reach 4‰， while those in aromatics， non-hydrocarbon， and asphaltene are relatively low， ranging from 1‰ to 3‰. When utilizing carbon isotopes to identify the source of deep oil， it is essential to first check the correlation between alkane contents and their δ13CPDB values to identify if the carbon isotope fractionation effects derived from thermal maturation exists.Subsequently， the δ13CPDB values of alkane should be properly recovered before utilizing it to identify the source of the oil. According to the abovementioned methods， authors identified the source of light oil from Chepaizi Uplift in the Western region of Junggar Basin. It confirmed the presence of carbon isotope fractionation effects in the light oil derived from thermal evolution. It shows a great possibility that the light oil is sourced from the underlying high-maturity source rock of the Permian， which is of important practical significance in the evaluation and deployment of the petroleum exploration target in this area.
2024, 31(4):164-173.
DOI: 10.13673/j.pgre.202405021
Abstract:
Due to large burial depths， ultra-deep clastic rock reservoirs have poor physical properties and low oil and gas productivity.However， the newly drilled Well Zheng10 in Shawan Sag， Sinopec exploration area， has encountered high-quality thick reservoirs in the Triassic Karamay Formation at a buried depth of 6 700 m， and conventional tests have obtained high industrial oil and gas flow. To reveal the characteristics of this set of reservoirs and favorable main controlling factors， clarify the direction of ultradeep clastic rock exploration， and reduce the risk of further oil and gas exploration in this area， this paper comprehensively analyzed the data of core， well logging， cast thin sections， physical properties， scanning electron microscopy， and diagenetic evolution of the reservoirs， and discussed the petrological， physical， and pore characteristics of reservoirs in the Triassic Karamay Formation in this area. The results show that the ultra-deep clastic rocks of the Triassic Karamay Formation in Well Zheng10 area are deposited in the front of the braided river delta. The lithology is dominated by glutenites， gravel-bearing fine sandstones， and fine sandstones， and the rock types are mainly feldspar lithic sandstones with low composition maturity. The remaining primary pores and solution pores dominate the reservoir space. The average porosity of the reservoirs is 9.1%， and the average permeability is 2.85 mD. The reservoir belongs to the ultra-low porosity and ultra-low permeability type and low porosity and low permeability type as a whole. Favorable sedimentary facies zones， constructive diagenesis， and abnormal high-pressure control the development and distribution of favorable reservoirs in this area. Among them， sedimentary microfacies are the basis of favorable reservoir development.The fine sandstones deposited in the underwater distributary channel at the front of the braided river delta are better sorted and rounded. The contents of the muddy matrix are low， and the physical properties of the reservoir are better， which are the dominant phase zones for favorable reservoir development. The sodium feldspar cements generated in the early diagenetic process are dissolved by acids in the later period， which increases the dissolution pores and is an essential constructive diagenesis. The abnormal high-pressures formed by continuous oil and gas charging form early and develop continuously for a long time， playing an important construction role. The research results have a guiding role for the subsequent ultra-deep oil and gas exploration in this area.
Due to large burial depths， ultra-deep clastic rock reservoirs have poor physical properties and low oil and gas productivity.However， the newly drilled Well Zheng10 in Shawan Sag， Sinopec exploration area， has encountered high-quality thick reservoirs in the Triassic Karamay Formation at a buried depth of 6 700 m， and conventional tests have obtained high industrial oil and gas flow. To reveal the characteristics of this set of reservoirs and favorable main controlling factors， clarify the direction of ultradeep clastic rock exploration， and reduce the risk of further oil and gas exploration in this area， this paper comprehensively analyzed the data of core， well logging， cast thin sections， physical properties， scanning electron microscopy， and diagenetic evolution of the reservoirs， and discussed the petrological， physical， and pore characteristics of reservoirs in the Triassic Karamay Formation in this area. The results show that the ultra-deep clastic rocks of the Triassic Karamay Formation in Well Zheng10 area are deposited in the front of the braided river delta. The lithology is dominated by glutenites， gravel-bearing fine sandstones， and fine sandstones， and the rock types are mainly feldspar lithic sandstones with low composition maturity. The remaining primary pores and solution pores dominate the reservoir space. The average porosity of the reservoirs is 9.1%， and the average permeability is 2.85 mD. The reservoir belongs to the ultra-low porosity and ultra-low permeability type and low porosity and low permeability type as a whole. Favorable sedimentary facies zones， constructive diagenesis， and abnormal high-pressure control the development and distribution of favorable reservoirs in this area. Among them， sedimentary microfacies are the basis of favorable reservoir development.The fine sandstones deposited in the underwater distributary channel at the front of the braided river delta are better sorted and rounded. The contents of the muddy matrix are low， and the physical properties of the reservoir are better， which are the dominant phase zones for favorable reservoir development. The sodium feldspar cements generated in the early diagenetic process are dissolved by acids in the later period， which increases the dissolution pores and is an essential constructive diagenesis. The abnormal high-pressures formed by continuous oil and gas charging form early and develop continuously for a long time， playing an important construction role. The research results have a guiding role for the subsequent ultra-deep oil and gas exploration in this area.
2024, 31(4):174-183.
DOI: 10.13673/j.pgre.202405040
Abstract:
There is great exploration potential for ultra-deep reservoirs in Junggar Basin， and reservoir prediction with seismic data is the main technical means of oil and gas exploration at present. However， due to the low signal-to-noise ratio of seismic data of ultra-deep reservoirs， unclear reservoir-seismic data correspondence， and few actual drilling wells， it is difficult to establish an effective initial model for seismic inversion， which restricts the accuracy and reliability of ultra-deep reservoir prediction. Gravity inversion，as an important quantitative interpretation method， can obtain the characteristics of underground density distribution and provide support for geological interpretation. According to the density model， a relatively reliable low-frequency model can be established for seismic inversion， which can overcome the difficulty of applying seismic data in ultra-deep reservoirs to a certain extent.Meanwhile， the acquisition of gravity data is economical and convenient compared with that of seismic data， and it is easier to be applied in practice. Therefore， a new technique applying gravity inversion to seismic data-based reservoir prediction was developed in this article. Firstly， a quasi-neural network gravity inversion technique based on Gaussian radial basis functions was proposed to solve the gravity inversion problem and improve the resolution and reliability of gravity inversion. Then， the density body obtained by gravity inversion was used as training data， and a neural network was trained together with seismic and logging data to establish the initial model of seismic inversion. Finally， seismic inversion was carried out with the initial model constraints. This technique broke through the application bottleneck of single seismic data in ultra-deep reservoir prediction and overcame the limitations of logging constraints， providing a reliable initial model for seismic inversion. The application of this technique to the prediction of ultra-deep clastic rock reservoirs in Junggar Basin was consistent with the existing geological knowledge， indicating that this method had high practical value and application potential for ultra-deep reservoir prediction and could provide technical support for ultra-deep reservoir exploration.
There is great exploration potential for ultra-deep reservoirs in Junggar Basin， and reservoir prediction with seismic data is the main technical means of oil and gas exploration at present. However， due to the low signal-to-noise ratio of seismic data of ultra-deep reservoirs， unclear reservoir-seismic data correspondence， and few actual drilling wells， it is difficult to establish an effective initial model for seismic inversion， which restricts the accuracy and reliability of ultra-deep reservoir prediction. Gravity inversion，as an important quantitative interpretation method， can obtain the characteristics of underground density distribution and provide support for geological interpretation. According to the density model， a relatively reliable low-frequency model can be established for seismic inversion， which can overcome the difficulty of applying seismic data in ultra-deep reservoirs to a certain extent.Meanwhile， the acquisition of gravity data is economical and convenient compared with that of seismic data， and it is easier to be applied in practice. Therefore， a new technique applying gravity inversion to seismic data-based reservoir prediction was developed in this article. Firstly， a quasi-neural network gravity inversion technique based on Gaussian radial basis functions was proposed to solve the gravity inversion problem and improve the resolution and reliability of gravity inversion. Then， the density body obtained by gravity inversion was used as training data， and a neural network was trained together with seismic and logging data to establish the initial model of seismic inversion. Finally， seismic inversion was carried out with the initial model constraints. This technique broke through the application bottleneck of single seismic data in ultra-deep reservoir prediction and overcame the limitations of logging constraints， providing a reliable initial model for seismic inversion. The application of this technique to the prediction of ultra-deep clastic rock reservoirs in Junggar Basin was consistent with the existing geological knowledge， indicating that this method had high practical value and application potential for ultra-deep reservoir prediction and could provide technical support for ultra-deep reservoir exploration.
2024, 31(4):184-195.
DOI: 10.13673/j.pgre.202405014
Abstract:
Shengli Oilfield has abundant oil and gas resources， with multiple types of reservoirs， and logging evaluation plays an essential role in exploration and development. The development history and the characteristics of logging evaluation technologies for reservoirs were systematically reviewed to celebrate the institute's 60th birthday. Summarizing experience and predicting the future have positive significance for the development and application in the professional logging field. A series of mature evaluation technologies formed in three types of reservoirs， including conventional sandstone reservoirs， complex reservoirs， and unconventional shale reservoirs， were systematically summarized according to the characteristics and evaluation difficulties of reservoirs. For conventional sandstone reservoirs， a highly applicable identification technology for oil layers was systematically developed， and an innovative method for establishing electrical standards constrained by the lower limits of lithology and oil potential was developed under multi-layer joint testing conditions. In addition， a pioneering logging modeling technology was proposed based on different diagenetic zones. Various technologies were developed for complex reservoirs， including logging identification of sandstone lithology in steep slope zones， effectiveness evaluation of low-permeability sandstone reservoirs， and identification and evaluation of oil layers with low resistivity. For unconventional shale reservoirs， a logging evaluation technology of reservoir parameters was preliminarily developed to evaluate the storage properties and oil potential mainly based on two-dimensional nuclear magnetic resonance experiments. These logging evaluation technologies for different types of reservoirs reflected the combination of wellbore data and geological understanding， as well as the integration of rock physics and logging models， and they demonstrated the ability of logging to serve geology and reservoirs and achieved good application results. In the future， the remaining resources will mainly be distributed in hidden oil and gas reservoirs and deep layers. In order to meet the needs of exploration and development， it is necessary to strengthen the analysis of experimental data， gas logging， and testing production data， combine logging evaluation and geology，intensify the application of new logging technologies such as logging while drilling， imaging， and nuclear magnetic resonance，carry out comprehensive research and evaluation， and expand the evaluation and prediction of production capacity of oil layers from the perspective of evaluation objectives. Moreover， it is necessary to fully rely on expert experience to select samples and deepen the application of big data/artificial intelligence on the basis of conventional technologies， which will definitely achieve good results.
Shengli Oilfield has abundant oil and gas resources， with multiple types of reservoirs， and logging evaluation plays an essential role in exploration and development. The development history and the characteristics of logging evaluation technologies for reservoirs were systematically reviewed to celebrate the institute's 60th birthday. Summarizing experience and predicting the future have positive significance for the development and application in the professional logging field. A series of mature evaluation technologies formed in three types of reservoirs， including conventional sandstone reservoirs， complex reservoirs， and unconventional shale reservoirs， were systematically summarized according to the characteristics and evaluation difficulties of reservoirs. For conventional sandstone reservoirs， a highly applicable identification technology for oil layers was systematically developed， and an innovative method for establishing electrical standards constrained by the lower limits of lithology and oil potential was developed under multi-layer joint testing conditions. In addition， a pioneering logging modeling technology was proposed based on different diagenetic zones. Various technologies were developed for complex reservoirs， including logging identification of sandstone lithology in steep slope zones， effectiveness evaluation of low-permeability sandstone reservoirs， and identification and evaluation of oil layers with low resistivity. For unconventional shale reservoirs， a logging evaluation technology of reservoir parameters was preliminarily developed to evaluate the storage properties and oil potential mainly based on two-dimensional nuclear magnetic resonance experiments. These logging evaluation technologies for different types of reservoirs reflected the combination of wellbore data and geological understanding， as well as the integration of rock physics and logging models， and they demonstrated the ability of logging to serve geology and reservoirs and achieved good application results. In the future， the remaining resources will mainly be distributed in hidden oil and gas reservoirs and deep layers. In order to meet the needs of exploration and development， it is necessary to strengthen the analysis of experimental data， gas logging， and testing production data， combine logging evaluation and geology，intensify the application of new logging technologies such as logging while drilling， imaging， and nuclear magnetic resonance，carry out comprehensive research and evaluation， and expand the evaluation and prediction of production capacity of oil layers from the perspective of evaluation objectives. Moreover， it is necessary to fully rely on expert experience to select samples and deepen the application of big data/artificial intelligence on the basis of conventional technologies， which will definitely achieve good results.
2024, 31(4):196-206.
DOI: 10.13673/j.pgre.202405041
Abstract:
Geothermal resources are widely distributed in Jiyang Depression， with great potential. They would be essential directions for the development and utilization of geothermal resources of Shengli Oilfield in the future. The geothermal geological conditions were systematically sorted out， such as thermal reservoir， thermal cover， and heat source of hydrothermal geothermal resources and geothermal resources of dry-hot rocks in Jiyang Depression， and the amounts of two types of geothermal resources were calculated respectively to reveal their geothermal resource potential to develop and utilize geothermal resources in Jiyang Depression scientifically and efficiently，. The results show that hydrothermal geothermal resources in Jiyang Depression are mainly deposited in the Guantao Formation， Dongying Formation， and Lower Paleozoic strata. Among them， Guantao Formation is the strata with the largest potential for hydrothermal geothermal resources， featuring a wide distribution and massive resources. It is the critical stratum for exploration and utilization in the next step. Jiyang Depression is a sedimentary basin with a cold crust and hot mantle and has a high geothermal flow value. The thermal reservoirs in the geothermal resources of dry-hot rocks are mainly magmatic rocks and metamorphic rocks of the Archean. The heat flow in the deep mantle is the main heat source. The distribution area of thermal reservoirs is large and has high temperatures， and the resources are primarily distributed in Bohai Bay Basin. Geothermal resources are rich in Jiyang Depression. It is suggested that the relationship between hydrothermal geothermal resources and oil and gas， as well as the evaluation of resource zoning， should be strengthened to accelerate the development and utilization of geothermal resources. The exploration and development of geothermal resources of dry-hot rock is still in the initial stage. Research on the selection of thermal reservoir types and heat source mechanisms should be strengthened in the future.
Geothermal resources are widely distributed in Jiyang Depression， with great potential. They would be essential directions for the development and utilization of geothermal resources of Shengli Oilfield in the future. The geothermal geological conditions were systematically sorted out， such as thermal reservoir， thermal cover， and heat source of hydrothermal geothermal resources and geothermal resources of dry-hot rocks in Jiyang Depression， and the amounts of two types of geothermal resources were calculated respectively to reveal their geothermal resource potential to develop and utilize geothermal resources in Jiyang Depression scientifically and efficiently，. The results show that hydrothermal geothermal resources in Jiyang Depression are mainly deposited in the Guantao Formation， Dongying Formation， and Lower Paleozoic strata. Among them， Guantao Formation is the strata with the largest potential for hydrothermal geothermal resources， featuring a wide distribution and massive resources. It is the critical stratum for exploration and utilization in the next step. Jiyang Depression is a sedimentary basin with a cold crust and hot mantle and has a high geothermal flow value. The thermal reservoirs in the geothermal resources of dry-hot rocks are mainly magmatic rocks and metamorphic rocks of the Archean. The heat flow in the deep mantle is the main heat source. The distribution area of thermal reservoirs is large and has high temperatures， and the resources are primarily distributed in Bohai Bay Basin. Geothermal resources are rich in Jiyang Depression. It is suggested that the relationship between hydrothermal geothermal resources and oil and gas， as well as the evaluation of resource zoning， should be strengthened to accelerate the development and utilization of geothermal resources. The exploration and development of geothermal resources of dry-hot rock is still in the initial stage. Research on the selection of thermal reservoir types and heat source mechanisms should be strengthened in the future.
2024, 31(4):207-216.
DOI: 10.13673/j.pgre.202405013
Abstract:
Various symbiotic/associated oil and gas resources have been found in the exploration area of Shengli Oilfield， and some of them serve as strategic resources for guaranteeing the security of national defense， agriculture， high-tech， and other industries，which are of great value in development and utilization. The current exploration and development status， occurrence characteristics，ore-forming conditions， and comprehensive utilization prospects of helium， brine （potassium salt）， and uranium ore that have been deeply studied and industrially produced in China were analyzed. The results show that ① the high helium anomalies are mainly distributed in more than 10 areas of the Jiyang Depression and Qaidam Basin， as well as in multiple layers of the Proterozoic-Cenozoic， associated with conventional natural gas， non-hydrocarbon gas， and shale gas； ② Jiyang Depression and Qaidam Basin provide the paleoclimate and palaeoenvironment for developing brine （potassium salt） from the Paleogene to the Quaternary. The oilfield water in Dongying Sag contains abundant amounts of bromine， lithium， and potassium， and more potassium and lithium are found in the oilfield water in Qaidam Basin， with the content in some areas reaching industrial grade； ③ the sandstone is the primary type of uranium ore. The multiple wells in Chepaizi Uplift exhibit highly abnormal gamma values in the Cretaceous and Neogene，indicating that this area is the most favorable prospective area of associated uranium ore. In other exploration areas of Shengli Oilfield， such as Tuha Basin， Qaidam Basin， and Jiyang Depression， the forming conditions for uranium ore are observed， including uranium sources， structures， lithofacies， hydrogeology， etc.， and natural gamma logging data from some wells show high abnormal values. Overall， the symbiotic/associated oil and gas resources in the exploration area of Shengli Oilfield show the characteristics of various types， multiple layers， and wide abnormal areas. It is necessary to fully take the natural advantages of Shengli Oilfield in terms of basic exploration data， basic geological achievements， and engineering facilities，to systematically carry out research on the reservoir forming （ore-forming） law of symbiotic/associated oil and gas resources， evaluate resource potential， and innovate extraction technology as soon as possible， to achieve a new business growth pole.
Various symbiotic/associated oil and gas resources have been found in the exploration area of Shengli Oilfield， and some of them serve as strategic resources for guaranteeing the security of national defense， agriculture， high-tech， and other industries，which are of great value in development and utilization. The current exploration and development status， occurrence characteristics，ore-forming conditions， and comprehensive utilization prospects of helium， brine （potassium salt）， and uranium ore that have been deeply studied and industrially produced in China were analyzed. The results show that ① the high helium anomalies are mainly distributed in more than 10 areas of the Jiyang Depression and Qaidam Basin， as well as in multiple layers of the Proterozoic-Cenozoic， associated with conventional natural gas， non-hydrocarbon gas， and shale gas； ② Jiyang Depression and Qaidam Basin provide the paleoclimate and palaeoenvironment for developing brine （potassium salt） from the Paleogene to the Quaternary. The oilfield water in Dongying Sag contains abundant amounts of bromine， lithium， and potassium， and more potassium and lithium are found in the oilfield water in Qaidam Basin， with the content in some areas reaching industrial grade； ③ the sandstone is the primary type of uranium ore. The multiple wells in Chepaizi Uplift exhibit highly abnormal gamma values in the Cretaceous and Neogene，indicating that this area is the most favorable prospective area of associated uranium ore. In other exploration areas of Shengli Oilfield， such as Tuha Basin， Qaidam Basin， and Jiyang Depression， the forming conditions for uranium ore are observed， including uranium sources， structures， lithofacies， hydrogeology， etc.， and natural gamma logging data from some wells show high abnormal values. Overall， the symbiotic/associated oil and gas resources in the exploration area of Shengli Oilfield show the characteristics of various types， multiple layers， and wide abnormal areas. It is necessary to fully take the natural advantages of Shengli Oilfield in terms of basic exploration data， basic geological achievements， and engineering facilities，to systematically carry out research on the reservoir forming （ore-forming） law of symbiotic/associated oil and gas resources， evaluate resource potential， and innovate extraction technology as soon as possible， to achieve a new business growth pole.
YANG Guang
,
GAO Xiangcheng
,
LI Yongzhong
,
LI Xiuguo
,
GUO Zhaojiang
,
ZHAO Jiejie
,
WANG Hui
,
ZHENG Shengli
,
DONG Fuqi
2024, 31(4):217-226.
DOI: 10.13673/j.pgre.202405045
Abstract:
The core is one of the core strategic resources in the exploration and development of oil and gas fields and plays an important role in the research on facies of oil and gas reservoirs，physical properties of reservoirs， and oil content. Compared with the paper data，the physical geological data of the core has the characteristics of reduction and variability，and the original appearance of the core cannot be preserved for a long time，thus reducing the utilization value of the core. Digital core technologies can collect the original data of the core in time，enrich the geological information of the core，and improve the utilization rate of core data， so it is of great significance to research digital core technologies. According to the production practice of core digitization construction in Shengli Oilfield， the concept， equipment，and technical content of core digitization were described， and many important digital core technologies such as core gamma spectrometry measurement，XRF element testing，magnetic susceptibility testing， and CT scanning were analyzed. The geological application effects of each technology were discussed. The research results show that digital core technologies have the advantages of fast testing， good continuity，large data， and high precision. They can accurately reflect the characteristics of sediment changes and provide an important geological basis for the research on sedimentary genesis， reservoir description and evaluation， material composition， and other issues of shales，carbonate，and glutenite，with a broad application prospect. Digital core data is the continuous data of core scale obtained directly from the core，which is between the original data and the result data in terms of the nature of the data，and it focuses more on the originality of the core，which is the first-hand geological data. Digital core data has unique and important application value and is an important technical means to improve the application level of the core.
The core is one of the core strategic resources in the exploration and development of oil and gas fields and plays an important role in the research on facies of oil and gas reservoirs，physical properties of reservoirs， and oil content. Compared with the paper data，the physical geological data of the core has the characteristics of reduction and variability，and the original appearance of the core cannot be preserved for a long time，thus reducing the utilization value of the core. Digital core technologies can collect the original data of the core in time，enrich the geological information of the core，and improve the utilization rate of core data， so it is of great significance to research digital core technologies. According to the production practice of core digitization construction in Shengli Oilfield， the concept， equipment，and technical content of core digitization were described， and many important digital core technologies such as core gamma spectrometry measurement，XRF element testing，magnetic susceptibility testing， and CT scanning were analyzed. The geological application effects of each technology were discussed. The research results show that digital core technologies have the advantages of fast testing， good continuity，large data， and high precision. They can accurately reflect the characteristics of sediment changes and provide an important geological basis for the research on sedimentary genesis， reservoir description and evaluation， material composition， and other issues of shales，carbonate，and glutenite，with a broad application prospect. Digital core data is the continuous data of core scale obtained directly from the core，which is between the original data and the result data in terms of the nature of the data，and it focuses more on the originality of the core，which is the first-hand geological data. Digital core data has unique and important application value and is an important technical means to improve the application level of the core.
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