Volume 26,Issue 3,2019 Table of Contents
2019, 26(3):1-8.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.001
Abstract:
Jiyang Depression has stepped into medium-high exploration stage，and the discovered reserves distributes in shapes of several circles. There are still many reserves blank areas on the migration pathway from hydrocarbon kitchen to discovered oil-gas fields，and there is big potential for the undiscovered traps in blank area including lithologic traps，structural-lithologic traps，and unconformity traps to capture and accumulate hydrocarbon into reservoirs. By analyzing the exploration process of the lithologic traps in the saddle structure of Gudong-Hongliu Oilfield and the north slope of Kendong Swell，the inspiration from trap exploration on petroleum migration pathway and proposes of research ideas were described briefly. Taking the research process of the structural traps in the periphery area of Jiangjiadian Oilfield between Linnan hydrocarbon kitchen of Huimin Sag and Qudi Oilfield as an example，the main research idea and methods were introduced.The bridge between hydrocarbon kitchen and oil-gas field were built up through oil-source correlation，the target strata were built up by analyzing hydrocarbon reservoirs，the possible conductive layers and trap types were identified by studying the sedimentary environment，and the exploration targets were determined by effectively identifying and evaluating the traps. The summary and proposal of the research ideas and methods of“evaluation of traps on migration pathway from source kitchen to oil and gas field”are significant to guide the hydrocarbon exploration in the future.
Jiyang Depression has stepped into medium-high exploration stage，and the discovered reserves distributes in shapes of several circles. There are still many reserves blank areas on the migration pathway from hydrocarbon kitchen to discovered oil-gas fields，and there is big potential for the undiscovered traps in blank area including lithologic traps，structural-lithologic traps，and unconformity traps to capture and accumulate hydrocarbon into reservoirs. By analyzing the exploration process of the lithologic traps in the saddle structure of Gudong-Hongliu Oilfield and the north slope of Kendong Swell，the inspiration from trap exploration on petroleum migration pathway and proposes of research ideas were described briefly. Taking the research process of the structural traps in the periphery area of Jiangjiadian Oilfield between Linnan hydrocarbon kitchen of Huimin Sag and Qudi Oilfield as an example，the main research idea and methods were introduced.The bridge between hydrocarbon kitchen and oil-gas field were built up through oil-source correlation，the target strata were built up by analyzing hydrocarbon reservoirs，the possible conductive layers and trap types were identified by studying the sedimentary environment，and the exploration targets were determined by effectively identifying and evaluating the traps. The summary and proposal of the research ideas and methods of“evaluation of traps on migration pathway from source kitchen to oil and gas field”are significant to guide the hydrocarbon exploration in the future.
2019, 26(3):9-19.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.002
Abstract:
As the oilfield with only 50 million-ton reserves that has been overall developed of SINOPEC during the 12th Five-Year Plan，Chunfeng Oilfield has established a strategic goal of building a million-ton oil production base within five years at the very beginning of its development. In view of the lack of effective reservoir description，development mode，engineering technology，management system，and other difficult problems in the efficient development of thin-shallow superheavy oil reservoir，targeted systemic researches were conducted centered on“three-new and three-high”mode. Eventually seven innovative key technologies were developed，technologies of two meters thin-shallow detailed reservoir prediction and high-efficiency thermal compound oil recovery have been developed to solve the problem of efficient production. Horizontal well sand-control plug-drilling-free integrated technology of drilling and completion，as well as horizontal pump integrated technology of steam injection and oil production were proposed to solve the problem of effective development.High-dryness circulating fluidized-bed environmental protection boiler，as well as produced water low-temperature multi·effect mechanical compression evaporation technology were improved to realize green and low-carbon development. Intelligent oilfield efficient management operation system was constructed to improve labor productivity and to reduce the development cost. Chunfeng Oilfield developed nearly 50 million tons of reserves and has established a stable oil production of million tons for four years from 2015 to 2018. The capacity construction investment and full cost per unit reduced by about one-third. While producing great economic and social benefits，these key technologies have enriched the theory and technology of heavy oil reservoir development. They have been applied in Xinjiang，Henan，East Shengli and other similar oilfields in China，and support the scale profitable development of low grade super-heavy oil reservoir.
As the oilfield with only 50 million-ton reserves that has been overall developed of SINOPEC during the 12th Five-Year Plan，Chunfeng Oilfield has established a strategic goal of building a million-ton oil production base within five years at the very beginning of its development. In view of the lack of effective reservoir description，development mode，engineering technology，management system，and other difficult problems in the efficient development of thin-shallow superheavy oil reservoir，targeted systemic researches were conducted centered on“three-new and three-high”mode. Eventually seven innovative key technologies were developed，technologies of two meters thin-shallow detailed reservoir prediction and high-efficiency thermal compound oil recovery have been developed to solve the problem of efficient production. Horizontal well sand-control plug-drilling-free integrated technology of drilling and completion，as well as horizontal pump integrated technology of steam injection and oil production were proposed to solve the problem of effective development.High-dryness circulating fluidized-bed environmental protection boiler，as well as produced water low-temperature multi·effect mechanical compression evaporation technology were improved to realize green and low-carbon development. Intelligent oilfield efficient management operation system was constructed to improve labor productivity and to reduce the development cost. Chunfeng Oilfield developed nearly 50 million tons of reserves and has established a stable oil production of million tons for four years from 2015 to 2018. The capacity construction investment and full cost per unit reduced by about one-third. While producing great economic and social benefits，these key technologies have enriched the theory and technology of heavy oil reservoir development. They have been applied in Xinjiang，Henan，East Shengli and other similar oilfields in China，and support the scale profitable development of low grade super-heavy oil reservoir.
2019, 26(3):20-30.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.003
Abstract:
The faulted lacustrine basin in eastern China is rich in underground hot water resources. The lack of isotopic and trace element analysis tests for underground hot water in this type of basin limits the research of the origin and evolution of underground hot water in this area and restricts the exploration and development of underground hot water. In this study，Dongying Sag was taken as the main research area，the constant ion characteristics，ion parameters and other indicators were first used to classify the underground hot water in the research area. The source and evolution process of underground hot water in the faulted lacustrine basin were discussed by using temperature and pressure characteristics of different types of underground hot water and the water-rock reaction products of reservoirs. Studies have shown that there are three different types of underground hot water in Dongying Sag. The first type of underground hot water is meteoric water which is concentrated in Dongying Formation and Guantao Formation，and it is in an open environment of normal temperature and atmospheric pressure that experiences a certain degree of atmospheric infiltration transformation and evaporation concentration of atmospheric precipitation. The second type of underground hot water is the lake water which is concentrated in the three segments of Shahejie Formation，Dongying Formation and Guantao Formation，and it is in an atmospheric-overpressure transition system that experiences water consumption concentration，CO2 injection from organic sources and related waterrock reactions. The third type of underground hot water is the origin saline lacustrine water which is concentrated in the fourth member and the third member of Shahejie Formation，and it is totally in an overpressure system that experiences water consumption concentration，CO2 injection from organic sources and karstenite dissolution.
The faulted lacustrine basin in eastern China is rich in underground hot water resources. The lack of isotopic and trace element analysis tests for underground hot water in this type of basin limits the research of the origin and evolution of underground hot water in this area and restricts the exploration and development of underground hot water. In this study，Dongying Sag was taken as the main research area，the constant ion characteristics，ion parameters and other indicators were first used to classify the underground hot water in the research area. The source and evolution process of underground hot water in the faulted lacustrine basin were discussed by using temperature and pressure characteristics of different types of underground hot water and the water-rock reaction products of reservoirs. Studies have shown that there are three different types of underground hot water in Dongying Sag. The first type of underground hot water is meteoric water which is concentrated in Dongying Formation and Guantao Formation，and it is in an open environment of normal temperature and atmospheric pressure that experiences a certain degree of atmospheric infiltration transformation and evaporation concentration of atmospheric precipitation. The second type of underground hot water is the lake water which is concentrated in the three segments of Shahejie Formation，Dongying Formation and Guantao Formation，and it is in an atmospheric-overpressure transition system that experiences water consumption concentration，CO2 injection from organic sources and related waterrock reactions. The third type of underground hot water is the origin saline lacustrine water which is concentrated in the fourth member and the third member of Shahejie Formation，and it is totally in an overpressure system that experiences water consumption concentration，CO2 injection from organic sources and karstenite dissolution.
2019, 26(3):31-37.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.004
Abstract:
Sedimentary types，characteristics and depositional model of gravity flow developing in the upper submember of the first member of Liushagang Formation in Weixi’nan Sag were studied based on drilling，logging，core，experimental data and 3D seismic. The results show that there are three types of gravity flows including debris flow，turbidite current and slump deposit in the upper submember of the first member of Liushagang Formation in Weixi’nan Sag，among which debris flow and slump mainly develop in the study region. Debris flow can be divided into sandy debris flow and muddy debris flow according to its lithological composition. The sandy debris flow is characterized by massive structures，argillaceous rigup and floating mud-gravel.Well-developed plastic deformation structures in slumps deposit which shows the characteristics of gravity flow deposits，and retains the characteristics of traction flow deposits. The coupling of lake level change，provenance system，slope broken and source channel controls the sedimentary types and distribution of gravity flow，and two classical depositional models of gravity flow are summarized including north-west provenance delta-faulted slope-erosion channel and west provenance delta-synsedimentary slope broken.
Sedimentary types，characteristics and depositional model of gravity flow developing in the upper submember of the first member of Liushagang Formation in Weixi’nan Sag were studied based on drilling，logging，core，experimental data and 3D seismic. The results show that there are three types of gravity flows including debris flow，turbidite current and slump deposit in the upper submember of the first member of Liushagang Formation in Weixi’nan Sag，among which debris flow and slump mainly develop in the study region. Debris flow can be divided into sandy debris flow and muddy debris flow according to its lithological composition. The sandy debris flow is characterized by massive structures，argillaceous rigup and floating mud-gravel.Well-developed plastic deformation structures in slumps deposit which shows the characteristics of gravity flow deposits，and retains the characteristics of traction flow deposits. The coupling of lake level change，provenance system，slope broken and source channel controls the sedimentary types and distribution of gravity flow，and two classical depositional models of gravity flow are summarized including north-west provenance delta-faulted slope-erosion channel and west provenance delta-synsedimentary slope broken.
2019, 26(3):38-45.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.005
Abstract:
The oil and water relationship of low oil-saturated super-heavy oil reservoir is generally complicated. In this kind of reservoir，the study of oil-water distribution rule is the basis for probable reserves evaluation and development.Based on the data of logging，core analysis and development performance，the evaluation of oil-bearing property of reservoir and the oil and water distribution characteristics were studied in Ng6 layer in the east region of Gudao Oilfield，and it is believed that the reservoir is a low oil-saturated reservoir with complicated oil and water relationship. The weak driving forces dominated by gravity and buoyancy are difficult to drain the original water in pores with small throats，which leads to a lower oil saturation of sand bodies in the river edge and river beach with poor physical property. After the accumulation of oil and gas，the intense movement of Gubei Fault make oil density increase to 1.01 g/cm3，and continuous oil column with a certain length is able to make oil overcome capillarity pressure and blow out of pore to gather in low part of the structure and make inversion of oil and water. Directed by reservoir development mechanism based on oil-water distribution characteristics and control factors，the oil-water distribution pattern of Ng6 low oil-saturated super-heavy oil can be divided into four patterns including，lithological controlled patternⅠ，tectonic controlled patternⅡ，tectonic and lithological controlled patternⅢ，and oil-water density differentiation controlled patternⅣ. This research formulates the differentiated development strategy and realizes reserves evaluation and effective utilization.
The oil and water relationship of low oil-saturated super-heavy oil reservoir is generally complicated. In this kind of reservoir，the study of oil-water distribution rule is the basis for probable reserves evaluation and development.Based on the data of logging，core analysis and development performance，the evaluation of oil-bearing property of reservoir and the oil and water distribution characteristics were studied in Ng6 layer in the east region of Gudao Oilfield，and it is believed that the reservoir is a low oil-saturated reservoir with complicated oil and water relationship. The weak driving forces dominated by gravity and buoyancy are difficult to drain the original water in pores with small throats，which leads to a lower oil saturation of sand bodies in the river edge and river beach with poor physical property. After the accumulation of oil and gas，the intense movement of Gubei Fault make oil density increase to 1.01 g/cm3，and continuous oil column with a certain length is able to make oil overcome capillarity pressure and blow out of pore to gather in low part of the structure and make inversion of oil and water. Directed by reservoir development mechanism based on oil-water distribution characteristics and control factors，the oil-water distribution pattern of Ng6 low oil-saturated super-heavy oil can be divided into four patterns including，lithological controlled patternⅠ，tectonic controlled patternⅡ，tectonic and lithological controlled patternⅢ，and oil-water density differentiation controlled patternⅣ. This research formulates the differentiated development strategy and realizes reserves evaluation and effective utilization.
2019, 26(3):46-53.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.006
Abstract:
The Hashan area in the northwestern margin of Junggar Basin is a complex piedmont tectonic belt，in which the Carboniferous volcanic nappe forming in the continental margin island arc is an important oil and gas reservoir in this area.To understand the volcanic reservoir development characteristics and control factors in the complex tectonic belt，using a large number of outcrops，core，thin section，scanning electron microscopy and imaging logging analysis data，the characteristics of volcanic reservoir，influencing factors and accumulating model were studied. The results show that the carboniferous volcanic rock is mainly composed of 2 types and 5 kinds of lithology，including lava（basalt，andesite，and basaltic-andesite）and volcaniclastic rocks（volcanic breccia and tuff）. Lithology and lithofacies are the internal factors influencing volcanic reservoirs development，while weathering and leaching and tectonism are the external factors. The genetic types of reservoirs include the lithofacies-fault type and the lithofacies-fold type. The volcanic breccia，tuff and andesite developing at the front wing and core of nappe，and weathering crust of faults intersection，and eruption cycle boundary are favorable distribution areas of volcanic reservoirs.
The Hashan area in the northwestern margin of Junggar Basin is a complex piedmont tectonic belt，in which the Carboniferous volcanic nappe forming in the continental margin island arc is an important oil and gas reservoir in this area.To understand the volcanic reservoir development characteristics and control factors in the complex tectonic belt，using a large number of outcrops，core，thin section，scanning electron microscopy and imaging logging analysis data，the characteristics of volcanic reservoir，influencing factors and accumulating model were studied. The results show that the carboniferous volcanic rock is mainly composed of 2 types and 5 kinds of lithology，including lava（basalt，andesite，and basaltic-andesite）and volcaniclastic rocks（volcanic breccia and tuff）. Lithology and lithofacies are the internal factors influencing volcanic reservoirs development，while weathering and leaching and tectonism are the external factors. The genetic types of reservoirs include the lithofacies-fault type and the lithofacies-fold type. The volcanic breccia，tuff and andesite developing at the front wing and core of nappe，and weathering crust of faults intersection，and eruption cycle boundary are favorable distribution areas of volcanic reservoirs.
2019, 26(3):54-62.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.007
Abstract:
The Chang8 tight reservoir of Triassic Yanchang Formation in Fuxian area of the southern Ordos Basin was taken as an example to systematically study the reservoir petrology characteristics，reservoir physical characteristics and diagenesis，and to discusses the influence of diagenetic facies types and differential diagenesis on reservoir physical property by thin section observation，scanning electron microscope（SEM）and X-ray diffraction. The results show that the main rock lithology of Chang8 tight reservoir in the study area is ultrafine to fine arkose with complex and different diagenesis. Diagenetic facies of the reservoir can be divided into three types：mechanical compaction diagenetic facies，carbonate cementation diagenetic facies，and weak compaction-weak cementation diagenetic facies. The sand of mechanical compaction diagenetic facies becomes tight reservoir mainly due to the mechanical compaction in the early stage of diagenesis and are mainly distributed in sand bodies with weak hydrodynamics. The sand of carbonate cementation diagenetic facies are densified in the early stage of diagenesis due to the massive precipitation of carbonate cement. The sand of weak compactionweak cementation diagenetic facies are mostly distributed in the sand body with strong hydrodynamics in the middle or lower part of the distributary channel. It has a high content of rigid grains and forms a large amount of chlorite cement in the early stage of diagenesis. Therefore，the ability to resist compaction is significantly improved，and the chlorite membrane inhibits the formation of other types of cement to a certain extent，thereby providing sufficient space for pore fluid activity，resulting in the development of dissolution，which constitutes a relatively high-quality reservoir in the study area.
The Chang8 tight reservoir of Triassic Yanchang Formation in Fuxian area of the southern Ordos Basin was taken as an example to systematically study the reservoir petrology characteristics，reservoir physical characteristics and diagenesis，and to discusses the influence of diagenetic facies types and differential diagenesis on reservoir physical property by thin section observation，scanning electron microscope（SEM）and X-ray diffraction. The results show that the main rock lithology of Chang8 tight reservoir in the study area is ultrafine to fine arkose with complex and different diagenesis. Diagenetic facies of the reservoir can be divided into three types：mechanical compaction diagenetic facies，carbonate cementation diagenetic facies，and weak compaction-weak cementation diagenetic facies. The sand of mechanical compaction diagenetic facies becomes tight reservoir mainly due to the mechanical compaction in the early stage of diagenesis and are mainly distributed in sand bodies with weak hydrodynamics. The sand of carbonate cementation diagenetic facies are densified in the early stage of diagenesis due to the massive precipitation of carbonate cement. The sand of weak compactionweak cementation diagenetic facies are mostly distributed in the sand body with strong hydrodynamics in the middle or lower part of the distributary channel. It has a high content of rigid grains and forms a large amount of chlorite cement in the early stage of diagenesis. Therefore，the ability to resist compaction is significantly improved，and the chlorite membrane inhibits the formation of other types of cement to a certain extent，thereby providing sufficient space for pore fluid activity，resulting in the development of dissolution，which constitutes a relatively high-quality reservoir in the study area.
2019, 26(3):63-69.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.008
Abstract:
The acoustic impedance of fluid-filled fractures has a significant difference with that of rocks. The energy of the sound wave decays when the acoustic wave passes the fractures. In order to effectively identify the single-well fracture sections in tight sandstone gas reservoirs，based on the EXDT full wave processing data in Area K of Ordos Basin，the array acoustic wave amplitude attenuation features were analyzed and calibrated by the core analysis，thin slice observation and micro-resistivity imaging data. The response characteristics of the increment of the acoustic amplitude attenuation values were clarified，and the cutoff values were determined as：the compressional amplitude attenuation value is more than 12.5 db/m，the shear amplitude attenuation value is more than 13 db/m，and the Stoneley wave amplitude attenuation value is more than 5.6 db/m. As a result，the identification of single-well fracture sections was well achieved. The case analysis of Area K in Ordos Basin shows that the fractures in Layer Qian5，He2，He4 and He6 relatively develop corresponding to a significant amplitude attenuation of array acoustic wave，and have a good correspondence with the main producing interval.The fractures improve the permeability of tight sandstone reservoirs obviously and contribute positively to reservoirs productivity. Therefore the accurate identification of the single-well fracture section has a guiding significance for the perforation.
The acoustic impedance of fluid-filled fractures has a significant difference with that of rocks. The energy of the sound wave decays when the acoustic wave passes the fractures. In order to effectively identify the single-well fracture sections in tight sandstone gas reservoirs，based on the EXDT full wave processing data in Area K of Ordos Basin，the array acoustic wave amplitude attenuation features were analyzed and calibrated by the core analysis，thin slice observation and micro-resistivity imaging data. The response characteristics of the increment of the acoustic amplitude attenuation values were clarified，and the cutoff values were determined as：the compressional amplitude attenuation value is more than 12.5 db/m，the shear amplitude attenuation value is more than 13 db/m，and the Stoneley wave amplitude attenuation value is more than 5.6 db/m. As a result，the identification of single-well fracture sections was well achieved. The case analysis of Area K in Ordos Basin shows that the fractures in Layer Qian5，He2，He4 and He6 relatively develop corresponding to a significant amplitude attenuation of array acoustic wave，and have a good correspondence with the main producing interval.The fractures improve the permeability of tight sandstone reservoirs obviously and contribute positively to reservoirs productivity. Therefore the accurate identification of the single-well fracture section has a guiding significance for the perforation.
2019, 26(3):70-77.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.009
Abstract:
Xujiahe Formation in western Sichuan Depression is one of the main gas producing horizons in Sichuan Basin.Based on the analysis of core observations，drilling and well data，it is considered that four sedimentary microfacies including underwater distributary channel，estuary dam，distributary bay and sheet sand are developed in the Upper 4th Member of Xujiahe Formation. Combined with common/cast thin section observations，scanning electron microscopy and X-ray diffraction，the diagenetic facies and tectonic facies of the reservoirs are studied in depth，and the diagenetic facies is divided into compacted facies，carbonate cemented facies，dissolved facies，kaolinite-corrosion facies，and carbonate cemented-corrosion facies，tectonic facies is divided into fracture facies and non-fracture facies. By comprehensively considering the influence of sedimentary，diagenetic and structural factors on the reservoir，the petrophysical facies of the reservoir in the Upper 4th Member of Xujiahe Formation is divided into five types including Ⅰ，Ⅱ1，Ⅱ2，Ⅲand Ⅳphysical facies. Among them，TypeⅠis a high-porosity matrix-fractured reservoir，Type Ⅱ1 is a high-porosity matrix reservoir，Type Ⅱ2 is a lowporosity matrix-fracture reservoir，Ⅲis a low-porosity matrix reservoir，and Type Ⅳ is mudstone. Based on the logging data，the logging criteria of various rock physical phases are established to provide a basis for the establishment of a single well petrophysical facies.
Xujiahe Formation in western Sichuan Depression is one of the main gas producing horizons in Sichuan Basin.Based on the analysis of core observations，drilling and well data，it is considered that four sedimentary microfacies including underwater distributary channel，estuary dam，distributary bay and sheet sand are developed in the Upper 4th Member of Xujiahe Formation. Combined with common/cast thin section observations，scanning electron microscopy and X-ray diffraction，the diagenetic facies and tectonic facies of the reservoirs are studied in depth，and the diagenetic facies is divided into compacted facies，carbonate cemented facies，dissolved facies，kaolinite-corrosion facies，and carbonate cemented-corrosion facies，tectonic facies is divided into fracture facies and non-fracture facies. By comprehensively considering the influence of sedimentary，diagenetic and structural factors on the reservoir，the petrophysical facies of the reservoir in the Upper 4th Member of Xujiahe Formation is divided into five types including Ⅰ，Ⅱ1，Ⅱ2，Ⅲand Ⅳphysical facies. Among them，TypeⅠis a high-porosity matrix-fractured reservoir，Type Ⅱ1 is a high-porosity matrix reservoir，Type Ⅱ2 is a lowporosity matrix-fracture reservoir，Ⅲis a low-porosity matrix reservoir，and Type Ⅳ is mudstone. Based on the logging data，the logging criteria of various rock physical phases are established to provide a basis for the establishment of a single well petrophysical facies.
10 Dynamic productivity prediction method of five-spot fractured well pattern in high water cut stage
2019, 26(3):78-84.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.010
Abstract:
The fractured well pattern productivity study is of great significance to optimization and development adjustment in the high water cut stage. Due to the heterogeneity of the reservoir，the remaining oil distribution in the high water cut stage is uneven. According to the streamline distribution characteristics of five-spot well pattern，injection-production units for the five-spot well pattern were divided into 4 injection-production areas，and each area was subdivided into several calculating units. Considering the uneven distribution of the remaining oil，the dynamic productivity prediction method for each calculating unit was proposed by using streamline integral method，material balance principle and steady-state sequential replacement method，and the productivity of five-sport well pattern was further calculated by summarizing the productivity of each calculating unit. The accuracy of the method was verified by comparing with the actual production data with the relative error of less than 5%，which meets the demands of the field. The influences of reservoir coefficient，reservoir heterogeneity，dimensionless fracture conductivity，fracture penetration ratio and remaining oil saturation at early fracturing stage were analyzed. The results show that a better reservoir coefficient and a higher remaining oil saturation lead to the higher productivity. The reservoir coefficient and remaining oil saturation in the fracture control area have great influences on the productivity at initial stage after fractured. The productivity increases with the increase of the dimensionless fracture conductivity and penetration ratio，but the effect of the dimensionless fracture conductivity on the productivity decreases with the increase of the dimensionless fracture conductivity.
The fractured well pattern productivity study is of great significance to optimization and development adjustment in the high water cut stage. Due to the heterogeneity of the reservoir，the remaining oil distribution in the high water cut stage is uneven. According to the streamline distribution characteristics of five-spot well pattern，injection-production units for the five-spot well pattern were divided into 4 injection-production areas，and each area was subdivided into several calculating units. Considering the uneven distribution of the remaining oil，the dynamic productivity prediction method for each calculating unit was proposed by using streamline integral method，material balance principle and steady-state sequential replacement method，and the productivity of five-sport well pattern was further calculated by summarizing the productivity of each calculating unit. The accuracy of the method was verified by comparing with the actual production data with the relative error of less than 5%，which meets the demands of the field. The influences of reservoir coefficient，reservoir heterogeneity，dimensionless fracture conductivity，fracture penetration ratio and remaining oil saturation at early fracturing stage were analyzed. The results show that a better reservoir coefficient and a higher remaining oil saturation lead to the higher productivity. The reservoir coefficient and remaining oil saturation in the fracture control area have great influences on the productivity at initial stage after fractured. The productivity increases with the increase of the dimensionless fracture conductivity and penetration ratio，but the effect of the dimensionless fracture conductivity on the productivity decreases with the increase of the dimensionless fracture conductivity.
2019, 26(3):85-91.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.011
Abstract:
The strong heterogeneity and high viscosity of crude oil in shallow fault-block reservoirs with small oil content lead to a rapid edge water coning problem during the production. The N2 huff and puff has the potential of controlling edge water coning since the N2 can supply the power of the reservoir. Therefore，the feasibility of N2/N2-surfactan/N2-CO2 huff and puff for controlling the edge water coning and enhancing oil recovery was studied in laboratory by the radial flow model with edge water at high temperature and high pressure. The factors including maximum reduction of water cut，water control duration，and increase of oil recovery were selected to evaluate and compare the effect of controlling the water coning and improving oil production and to analyze the mechanism of controlling edge water coning and improving oil production at different pressures. The results show that：N2/N2-surfactant/N2-CO2 huff and puff all have the ability of controlling edge water coning；the N2 huff and puff has the best ability of controlling water coning，but has the least ability of improving oil production with a low displacement efficiency；the N2 compound huff and puff has the ability of controlling edge water coning，and has the better ability of improving oil production than N2 huff and puff with the surfactant and CO2 to improve the oil displacement efficiency.
The strong heterogeneity and high viscosity of crude oil in shallow fault-block reservoirs with small oil content lead to a rapid edge water coning problem during the production. The N2 huff and puff has the potential of controlling edge water coning since the N2 can supply the power of the reservoir. Therefore，the feasibility of N2/N2-surfactan/N2-CO2 huff and puff for controlling the edge water coning and enhancing oil recovery was studied in laboratory by the radial flow model with edge water at high temperature and high pressure. The factors including maximum reduction of water cut，water control duration，and increase of oil recovery were selected to evaluate and compare the effect of controlling the water coning and improving oil production and to analyze the mechanism of controlling edge water coning and improving oil production at different pressures. The results show that：N2/N2-surfactant/N2-CO2 huff and puff all have the ability of controlling edge water coning；the N2 huff and puff has the best ability of controlling water coning，but has the least ability of improving oil production with a low displacement efficiency；the N2 compound huff and puff has the ability of controlling edge water coning，and has the better ability of improving oil production than N2 huff and puff with the surfactant and CO2 to improve the oil displacement efficiency.
2019, 26(3):92-98.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.012
Abstract:
Efficient development of tight oil reservoirs is an important task in the petroleum field. Spontaneous imbibition is an important mechanism for tight oil development，which is receiving increasing attention. Natural cores and artificial cores of the tight sandstone reservoirs in Xinjiang Oilfield were selected. Experiments with improved dynamic imbibition device were carried out to study the influence of permeability，temperature，pressure，core length and fracture density on the dynamic imbibition recovery. In addition，a new dimensionless normalized model of the imbibition recovery was proposed through normalization on the experimental parameters. The new model has a better fitting to the dynamic experimental data than the widely used Ma model. The results show that core permeability has a positive or negative correlation with the dynamic imbibition recovery within a certain permeability level；a higher temperature and a shorter core corresponds to a higher imbibition recovery under the same other conditions；higher fluid pressure is more favorable to the dynamic imbibition at the optimal pressure range of 5-7 MPa in the experimental study；increment of the imbibition recovery is linearly related to the fracture density.
Efficient development of tight oil reservoirs is an important task in the petroleum field. Spontaneous imbibition is an important mechanism for tight oil development，which is receiving increasing attention. Natural cores and artificial cores of the tight sandstone reservoirs in Xinjiang Oilfield were selected. Experiments with improved dynamic imbibition device were carried out to study the influence of permeability，temperature，pressure，core length and fracture density on the dynamic imbibition recovery. In addition，a new dimensionless normalized model of the imbibition recovery was proposed through normalization on the experimental parameters. The new model has a better fitting to the dynamic experimental data than the widely used Ma model. The results show that core permeability has a positive or negative correlation with the dynamic imbibition recovery within a certain permeability level；a higher temperature and a shorter core corresponds to a higher imbibition recovery under the same other conditions；higher fluid pressure is more favorable to the dynamic imbibition at the optimal pressure range of 5-7 MPa in the experimental study；increment of the imbibition recovery is linearly related to the fracture density.
2019, 26(3):99-104.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.013
Abstract:
In order to study the microscopic migration characteristics of heavy oil by CO2 flooding and its influence on the recovery at high temperature and high pressure（70 ℃，8 MPa），the microscopic visualization simulation system of high temperature and high pressure was used to simulate the displacement process of heavy oil by CO2 flooding in different stages and different regions，and its microscopic migration characteristics were studied. The effect of CO2 on recovery of heavy oil in this process was quantitatively analyzed. The results show that the process of CO2 flooding can be divided into three parts：oil and gas being soluble with each other，asphaltene precipitation，and gas-carrying asphaltene particles migration. At the stage of first gas flooding，CO2 moves freely with small bubbles，and then deformation，merge or splitting occurs. Finally，dominated by continuous phase migration. During the closing time，CO2 dissolves in heavy oil and precipitates out with asphaltene；at the stage of second gas flooding，CO2 carries some asphaltene particles and migrates continuously，and the swept volume increase. In addition，the reaction conditions in the process of CO2 flooding are adjusted to balance the interaction of gas viscosity reduction and asphaltene precipitation，so as to promote the effective migration of oil and gas and improve the recovery.
In order to study the microscopic migration characteristics of heavy oil by CO2 flooding and its influence on the recovery at high temperature and high pressure（70 ℃，8 MPa），the microscopic visualization simulation system of high temperature and high pressure was used to simulate the displacement process of heavy oil by CO2 flooding in different stages and different regions，and its microscopic migration characteristics were studied. The effect of CO2 on recovery of heavy oil in this process was quantitatively analyzed. The results show that the process of CO2 flooding can be divided into three parts：oil and gas being soluble with each other，asphaltene precipitation，and gas-carrying asphaltene particles migration. At the stage of first gas flooding，CO2 moves freely with small bubbles，and then deformation，merge or splitting occurs. Finally，dominated by continuous phase migration. During the closing time，CO2 dissolves in heavy oil and precipitates out with asphaltene；at the stage of second gas flooding，CO2 carries some asphaltene particles and migrates continuously，and the swept volume increase. In addition，the reaction conditions in the process of CO2 flooding are adjusted to balance the interaction of gas viscosity reduction and asphaltene precipitation，so as to promote the effective migration of oil and gas and improve the recovery.
2019, 26(3):105-110.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.014
Abstract:
New well production forecast method based on long-term and short-term memory（LSTM）neural network was proposed to solve the problems that artificial intelligence production prediction method commonly used in oilfields cannot consider the temporal correlation of data with time. Based on the introduction of principle and modeling steps of back propagation（BP）neural network，recurrent neural network（RNN），and LSTM neural network，development indicators affecting yearly oil production of new single well were selected taking the yearly production forecast of new single well of an oilfield as an example，the corresponding LSTM neural network were trained，and the yearly oil production of new single well was forecasted. The forecasted results were compared to those of support vector regression model and BP neural network. The results show that the forecast model has good fitting result with higher forecast accuracy. The forecast method based on LSTM neural network can be used as a new artificial intelligence method for the oil production forecast of new well in oilfields. It is a new method to accurately forecast the oil production of new wells in oilfield and to guide oilfield development decision making.
New well production forecast method based on long-term and short-term memory（LSTM）neural network was proposed to solve the problems that artificial intelligence production prediction method commonly used in oilfields cannot consider the temporal correlation of data with time. Based on the introduction of principle and modeling steps of back propagation（BP）neural network，recurrent neural network（RNN），and LSTM neural network，development indicators affecting yearly oil production of new single well were selected taking the yearly production forecast of new single well of an oilfield as an example，the corresponding LSTM neural network were trained，and the yearly oil production of new single well was forecasted. The forecasted results were compared to those of support vector regression model and BP neural network. The results show that the forecast model has good fitting result with higher forecast accuracy. The forecast method based on LSTM neural network can be used as a new artificial intelligence method for the oil production forecast of new well in oilfields. It is a new method to accurately forecast the oil production of new wells in oilfield and to guide oilfield development decision making.
2019, 26(3):111-116.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.015
Abstract:
Hydraulic fracturing is an important stimulation method for the low-permeability oil and gas reservoirs，and an increasing number of studies in this aspect have been proposed. However，the heterogeneity of reservoirs has not been considered in the most studies，in spite of that the heterogeneity is one of the key geological factor affecting the fracturing performance. Therefore，in this study，a model was proposed based on the material point method to estimate the stimulation of heterogeneous reservoir，and the J-integral was used to estimate the stimulated reservoir area and to evaluate the heterogeneity. The simulated in-situ differential stress field was compared with the microseismic detection results so as to verify the accuracy of the model. The results show that the calculation results of model considering the heterogeneity highly matched with the actual microseismic signals in the field；a higher J-integral curve fluctuation indicated a stronger heterogeneity of reservoir；15-stage hydraulic fracture stimulation is the most reasonable with the ratio of stimulated reservoir area as 0.87 and the growth rate less than 0.01；the fractures at the two wings of the heterogeneous reservoir were quite different，and they are different from the designed half-length of the fractures.
Hydraulic fracturing is an important stimulation method for the low-permeability oil and gas reservoirs，and an increasing number of studies in this aspect have been proposed. However，the heterogeneity of reservoirs has not been considered in the most studies，in spite of that the heterogeneity is one of the key geological factor affecting the fracturing performance. Therefore，in this study，a model was proposed based on the material point method to estimate the stimulation of heterogeneous reservoir，and the J-integral was used to estimate the stimulated reservoir area and to evaluate the heterogeneity. The simulated in-situ differential stress field was compared with the microseismic detection results so as to verify the accuracy of the model. The results show that the calculation results of model considering the heterogeneity highly matched with the actual microseismic signals in the field；a higher J-integral curve fluctuation indicated a stronger heterogeneity of reservoir；15-stage hydraulic fracture stimulation is the most reasonable with the ratio of stimulated reservoir area as 0.87 and the growth rate less than 0.01；the fractures at the two wings of the heterogeneous reservoir were quite different，and they are different from the designed half-length of the fractures.
2019, 26(3):117-122.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.016
Abstract:
Traditional shale gas productivity models do not consider the effect of gas-water two-phase flow on the productivity during the backflow of fracturing fluid. This study proposes a new shale gas productivity model that considers the effect of gas-water two-phase flow as well as the effect of shale gas adsorption，desorption，diffusion，slippage，stress sensitivity，and capillary imbibition. The model calculates the productivity of shale gas and the distribution of formation fluid saturation using the SS method based on the finite difference theory. The model was applied to a real field case to analyze how shale gas productivity was affected by the permeability of fracture network，the permeability of artificial major fractures，the length of artificial major fractures，the adsorption and desorption of shale gas，and the capillary force on shale gas. The results were compared to field observations. In the early period of production，the daily shale gas production first raised，peaked，and then dropped due to the backflow of the fracturing fluid. Compared to the case considering no backflow of fracturing fluid，the case considering the backflow of fracturing fluid has significantly lower shale gas production at the early period but similar production at the later period. The shale gas production at the early period increased with increasing fracture network permeability，artificial major fracture permeability，and artificial major fracture length. The shale gas adsorption and desorption had little effect on the shale gas production at the early period. The capillary force，however，would lower the backflow rate of the fracturing fluid，thus increasing the shale gas production，which is consistent with field observations.
Traditional shale gas productivity models do not consider the effect of gas-water two-phase flow on the productivity during the backflow of fracturing fluid. This study proposes a new shale gas productivity model that considers the effect of gas-water two-phase flow as well as the effect of shale gas adsorption，desorption，diffusion，slippage，stress sensitivity，and capillary imbibition. The model calculates the productivity of shale gas and the distribution of formation fluid saturation using the SS method based on the finite difference theory. The model was applied to a real field case to analyze how shale gas productivity was affected by the permeability of fracture network，the permeability of artificial major fractures，the length of artificial major fractures，the adsorption and desorption of shale gas，and the capillary force on shale gas. The results were compared to field observations. In the early period of production，the daily shale gas production first raised，peaked，and then dropped due to the backflow of the fracturing fluid. Compared to the case considering no backflow of fracturing fluid，the case considering the backflow of fracturing fluid has significantly lower shale gas production at the early period but similar production at the later period. The shale gas production at the early period increased with increasing fracture network permeability，artificial major fracture permeability，and artificial major fracture length. The shale gas adsorption and desorption had little effect on the shale gas production at the early period. The capillary force，however，would lower the backflow rate of the fracturing fluid，thus increasing the shale gas production，which is consistent with field observations.
2019, 26(3):123-128.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.017
Abstract:
The continental reservoirs are major development objects in China. There are a variety of challenges during this types of reservoirs development and the principle contradictions vary at different development stages. Therefore the theoretical basis of developing the reservoirs with high efficiency is to regard the development process as a whole life cycle with a priority to dynamic progressive. Based on the research on systematic dynamic synergetic progressive development rule，the principle of the dynamic synergetic progressive development was proposed，with the major leading force as the subdivision of series of strata and the adaptation of well patterns，and the driving force as the media transcendence. Six sequences on displacement media and five classical combinations about its progressive capacity were optimized through library experiment and numerical simulation. Based on these，combining with six development elements on the media transcendence，subdivision of series of strata，and adaptation of well patterns，etc.，a pagoda-like chart about all the development elements by pyramid principle was established，which illuminates the synergetic development pattern of all the development elements in whole life-cycle dominated by dynamic progress. In 2010，according to the chart and normal replacement progressive typical combination model，the development of gas flooding was implemented in north Liuzan block. The percentage recovery of OOIP at the end of the stage reached 23.4%，which increased by 14.8% than that of water flooding.
The continental reservoirs are major development objects in China. There are a variety of challenges during this types of reservoirs development and the principle contradictions vary at different development stages. Therefore the theoretical basis of developing the reservoirs with high efficiency is to regard the development process as a whole life cycle with a priority to dynamic progressive. Based on the research on systematic dynamic synergetic progressive development rule，the principle of the dynamic synergetic progressive development was proposed，with the major leading force as the subdivision of series of strata and the adaptation of well patterns，and the driving force as the media transcendence. Six sequences on displacement media and five classical combinations about its progressive capacity were optimized through library experiment and numerical simulation. Based on these，combining with six development elements on the media transcendence，subdivision of series of strata，and adaptation of well patterns，etc.，a pagoda-like chart about all the development elements by pyramid principle was established，which illuminates the synergetic development pattern of all the development elements in whole life-cycle dominated by dynamic progress. In 2010，according to the chart and normal replacement progressive typical combination model，the development of gas flooding was implemented in north Liuzan block. The percentage recovery of OOIP at the end of the stage reached 23.4%，which increased by 14.8% than that of water flooding.
2019, 26(3):129-134.
DOI: 10.13673/j.cnki.cn37-1359/te.2019.03.018
Abstract:
After the long-term water flooding，the oil reservoirs in the ultra-high water cut stage have unbalanced displacement in the plane and vertical direction，which affects their development effect. In order to achieve the equilibrium displacement，a numerical simulation technique was proposed to quantitatively characterize the displacement multiple and identify the difference in the displacement degree at different positions of the reservoir. According to the relationship among displacement multiple，residual oil saturation，and percentage recovery of OOIP，the displacement multiple was graded and evaluated. The ultra-high water cut reservoir was divided into four zones：weak displacement zone，strong displacement zone，high water consumption zone，and ineffective water injection zone. The distribution pattern of displacement multiple in different zones was determined，basis on this，the strategies for improving the displacement multiple of the weak displacement zone，changing the direction of liquid flow in the strong displacement zone，controlling the high water consumption zone by injection and production，and restraining and regulating the ineffective water injection were formed. The well pattern adjustment and optimization scheme of theⅧ-Ⅸoil zones in Shuanghe Oilfield was proposed. After the implementation，the waterflood recovery factor was increased by 1.43%，which achieved good application results.
After the long-term water flooding，the oil reservoirs in the ultra-high water cut stage have unbalanced displacement in the plane and vertical direction，which affects their development effect. In order to achieve the equilibrium displacement，a numerical simulation technique was proposed to quantitatively characterize the displacement multiple and identify the difference in the displacement degree at different positions of the reservoir. According to the relationship among displacement multiple，residual oil saturation，and percentage recovery of OOIP，the displacement multiple was graded and evaluated. The ultra-high water cut reservoir was divided into four zones：weak displacement zone，strong displacement zone，high water consumption zone，and ineffective water injection zone. The distribution pattern of displacement multiple in different zones was determined，basis on this，the strategies for improving the displacement multiple of the weak displacement zone，changing the direction of liquid flow in the strong displacement zone，controlling the high water consumption zone by injection and production，and restraining and regulating the ineffective water injection were formed. The well pattern adjustment and optimization scheme of theⅧ-Ⅸoil zones in Shuanghe Oilfield was proposed. After the implementation，the waterflood recovery factor was increased by 1.43%，which achieved good application results.
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