Volume 21,Issue 4,2014 Table of Contents
2014, 21(4):1-4.
Abstract:
At present, a large amount of oil reserves are in their late stage of super high water cut in Shengli oilfield. How to understand the potential of improving the recovery of this part of resources is a strategic issue closely related to the long-term development of oilfield. Based on the production practice and the laboratory research results, sustainable development ideas and research proposals were proposed aiming at reservoirs with super high water cut in the late stage. There is also abundant of reserves accumulating in extra.low permeability and tight oil reservoirs in Shengli oilfield. How to make a cost-effective development and recovery improvement of this kind of resources will be the main issues to face. Suggestions about key technique breakthroughs, supporting technology researches, development means of supplementing energy and so on are presented for the extra low permeability reservoirs. In addition, with the acceleration of the city planning and construction pace, the oil field development has become to be performed in city-center today otherwise in salt wasteland before. It is more and more common that reserves of great development potential are under ground with no space for development drilling; and the corresponding construction and management model have been proposed.
At present, a large amount of oil reserves are in their late stage of super high water cut in Shengli oilfield. How to understand the potential of improving the recovery of this part of resources is a strategic issue closely related to the long-term development of oilfield. Based on the production practice and the laboratory research results, sustainable development ideas and research proposals were proposed aiming at reservoirs with super high water cut in the late stage. There is also abundant of reserves accumulating in extra.low permeability and tight oil reservoirs in Shengli oilfield. How to make a cost-effective development and recovery improvement of this kind of resources will be the main issues to face. Suggestions about key technique breakthroughs, supporting technology researches, development means of supplementing energy and so on are presented for the extra low permeability reservoirs. In addition, with the acceleration of the city planning and construction pace, the oil field development has become to be performed in city-center today otherwise in salt wasteland before. It is more and more common that reserves of great development potential are under ground with no space for development drilling; and the corresponding construction and management model have been proposed.
2014, 21(4):5-9.
Abstract:
According to the gist of SINOPEC 2013 new management measures of exploration and reserves, the future exploration should follow the way of high efficiency. Based on analysis of 2013 exploration results in the eastern exploration area of Shengli oilfield，it was suggested that exploration in this area should focus on strengthening the new field of exploration, evaluating exploration targets comprehensively and integrating exploration and development in the new situation. By systematically analyzing exploration situation and potential of eastern area of Shengli oilfield in the mid-late period of 12th Five-Year Plan, the exploration direction and countermeasures for different exploration direction have been clearly proposed. The mature exploration area should still be the main field to enhance reserves while emphases should be put on fine exploration, reserves gaps and high quality and large scale reserves; in view of the low degree of exploration and understanding in Es4x-Ek and the pre Paleogene formation and the peripheral areas, systematic research and active exploration should be carried out with confidence to achieve breakthroughs; when it comes to unconventional oil and gas, the main issues of tight sandstone oil and gas exploration should focus on reservoir development mechanism research and supporting development techniques for reservoir protection and stimulation, while for the shale oil and gas researches on“sweet spot”identification standards, target prediction and hydrocarbon accumulating mechanism are the primary issues.
According to the gist of SINOPEC 2013 new management measures of exploration and reserves, the future exploration should follow the way of high efficiency. Based on analysis of 2013 exploration results in the eastern exploration area of Shengli oilfield，it was suggested that exploration in this area should focus on strengthening the new field of exploration, evaluating exploration targets comprehensively and integrating exploration and development in the new situation. By systematically analyzing exploration situation and potential of eastern area of Shengli oilfield in the mid-late period of 12th Five-Year Plan, the exploration direction and countermeasures for different exploration direction have been clearly proposed. The mature exploration area should still be the main field to enhance reserves while emphases should be put on fine exploration, reserves gaps and high quality and large scale reserves; in view of the low degree of exploration and understanding in Es4x-Ek and the pre Paleogene formation and the peripheral areas, systematic research and active exploration should be carried out with confidence to achieve breakthroughs; when it comes to unconventional oil and gas, the main issues of tight sandstone oil and gas exploration should focus on reservoir development mechanism research and supporting development techniques for reservoir protection and stimulation, while for the shale oil and gas researches on“sweet spot”identification standards, target prediction and hydrocarbon accumulating mechanism are the primary issues.
2014, 21(4):10-15.
Abstract:
As a typical rifted basin, Bonan sag has discovered all types of oil and gas accumulations that have been found in rifted basins, including conventional & intermediate & unconventional reservoirs that distributed from the margins to the center of the sag. Controlled by structural evolution, the petroleum geologic conditions include multi-stage tectonic movement, multi-set source rock, multistage generation and expulsion of hydrocarbons, multi-stage hydrocarbon migration and accumulation. The“five multi”are related to each other and determine the order of oil and gas distribution to form a unified whole of oil and gas distribution. The continuance of hydrocarbon distribution is characterized by the multi-layer of hydrocarbon accumulation in vertical and multi-type reservoirs distributed in horizontal. The control factors of the order of oil and gas distribution including the distribution and strike of tectonic unit, the condition of source rock, the origin and distribution of reservoir, the characteristic of cap rock and trap, the dynamic of petroleum migration and accumulation, which are organic integrated and related. In recent years, according to the understanding of the order and continuance of the distribution of hydrocarbon, the thought of stereoscopic exploration is used on the basis of conventional oil and gas exploration. Continuous oil and gas accumulations have been discovered represented by large-scale near-source tight reservoir and shale oil and gas, and exploration of conventional oil and gas also have made great progress.
As a typical rifted basin, Bonan sag has discovered all types of oil and gas accumulations that have been found in rifted basins, including conventional & intermediate & unconventional reservoirs that distributed from the margins to the center of the sag. Controlled by structural evolution, the petroleum geologic conditions include multi-stage tectonic movement, multi-set source rock, multistage generation and expulsion of hydrocarbons, multi-stage hydrocarbon migration and accumulation. The“five multi”are related to each other and determine the order of oil and gas distribution to form a unified whole of oil and gas distribution. The continuance of hydrocarbon distribution is characterized by the multi-layer of hydrocarbon accumulation in vertical and multi-type reservoirs distributed in horizontal. The control factors of the order of oil and gas distribution including the distribution and strike of tectonic unit, the condition of source rock, the origin and distribution of reservoir, the characteristic of cap rock and trap, the dynamic of petroleum migration and accumulation, which are organic integrated and related. In recent years, according to the understanding of the order and continuance of the distribution of hydrocarbon, the thought of stereoscopic exploration is used on the basis of conventional oil and gas exploration. Continuous oil and gas accumulations have been discovered represented by large-scale near-source tight reservoir and shale oil and gas, and exploration of conventional oil and gas also have made great progress.
2014, 21(4):16-18.
Abstract:
Usually, the study of fluvial river type and the single genetic sand body is mainly on the analyses of particle size distribution,sand body shape, sedimentary tectonics and so on. Observations on modern channel deposits show that at the transition stage of sequence evolution, not only the channel form changes, but also sands of different genetic types present alternately. Under the condition of dense well pattern with oil well spacing 75 m, injection well spacing 75 m, and injector-producer spacing 150 m in one block of Gudao oilfield, study was carried out to identify and compare sand body genetic type of meandering river and braided river by using the evolution mode of river regime. Ng1+2 sand formation is proved as braided stream sedimentary by establishing 6 kinds of vertically stacked evolution model of river regime, including braided stream-meandering river, meandering river-braided river, braided riverbraided stream, braided stream-braided river, braided stream-meandering and meandering river-braided stream. Four kinds of stratigraphic correlation modes were proposed to identify single sand body, which are vertical comparison near marker bed, superimposed channel sand body contrast, channel sand body incised comparison and lateral phase comparison. Four types of sand body amalgamations were established combined with field injection-production relation which include single channel internal, channel-channel, channel-abandoned channel, and channel-overbank-channel. Differences exist in injection-production connectivity owing to the differences in sand body amalgamations. The differences of connectivity mainly control differential accumulations of remaining oil at the extra high water-cut stage, and guide well pattern adjustment to improve the water flooding as well as chemical flooding recovery efficiency.
Usually, the study of fluvial river type and the single genetic sand body is mainly on the analyses of particle size distribution,sand body shape, sedimentary tectonics and so on. Observations on modern channel deposits show that at the transition stage of sequence evolution, not only the channel form changes, but also sands of different genetic types present alternately. Under the condition of dense well pattern with oil well spacing 75 m, injection well spacing 75 m, and injector-producer spacing 150 m in one block of Gudao oilfield, study was carried out to identify and compare sand body genetic type of meandering river and braided river by using the evolution mode of river regime. Ng1+2 sand formation is proved as braided stream sedimentary by establishing 6 kinds of vertically stacked evolution model of river regime, including braided stream-meandering river, meandering river-braided river, braided riverbraided stream, braided stream-braided river, braided stream-meandering and meandering river-braided stream. Four kinds of stratigraphic correlation modes were proposed to identify single sand body, which are vertical comparison near marker bed, superimposed channel sand body contrast, channel sand body incised comparison and lateral phase comparison. Four types of sand body amalgamations were established combined with field injection-production relation which include single channel internal, channel-channel, channel-abandoned channel, and channel-overbank-channel. Differences exist in injection-production connectivity owing to the differences in sand body amalgamations. The differences of connectivity mainly control differential accumulations of remaining oil at the extra high water-cut stage, and guide well pattern adjustment to improve the water flooding as well as chemical flooding recovery efficiency.
2014, 21(4):19-22.
Abstract:
he north slope of Chenjiazhuang uplift locates at the margin of the basin with widely distributed stratigraphic overlap traps.The oil source condition and reservoir-seal combinations are favorable for the formation of stratigraphic reservoirs. According to previous studies, the floor condition is the main factor which determines the effectiveness of stratigraphic traps in this area. By comparative analyses of petrophysical properties of the fans and oil properties, the lateral blockage ability of the heavy oil rim of the fan bodies is firstly proposed, by which the floor condition of Pretertiary is weakened and the exploration strategy of viscous crude oil stratigraphic reservoir is broaden. According to the quantitative analysis of the key elements of the reservoir, the key of exploration has been pointed out and the exploration process of viscous crude oil stratigraphic reservoir should be expected in this area.
he north slope of Chenjiazhuang uplift locates at the margin of the basin with widely distributed stratigraphic overlap traps.The oil source condition and reservoir-seal combinations are favorable for the formation of stratigraphic reservoirs. According to previous studies, the floor condition is the main factor which determines the effectiveness of stratigraphic traps in this area. By comparative analyses of petrophysical properties of the fans and oil properties, the lateral blockage ability of the heavy oil rim of the fan bodies is firstly proposed, by which the floor condition of Pretertiary is weakened and the exploration strategy of viscous crude oil stratigraphic reservoir is broaden. According to the quantitative analysis of the key elements of the reservoir, the key of exploration has been pointed out and the exploration process of viscous crude oil stratigraphic reservoir should be expected in this area.
2014, 21(4):23-27.
Abstract:
In recent years, shale gas has become a hot field of global unconventional natural gas and has attracted attentions of many countries and oil companies. However, there are no evaluation methods and criterions of regional selection for marine shale gas in South China. Based on geological background and controlling factors of shale gas accumulation, the paper discussed the ideas and methods of shale gas favorable targets evaluation in the southern China through analogical study of the shale gas accumulation conditions between South China and America. Since the shale age is old and has high thermal evolution degree, the preservation condition is poor and the structure condition and surface condition is complex in South China. Evaluation systems and criterions of regional selection of marine shale gas in South China should take the preservation conditions as the core while considering the geological evaluation and economic evaluation at the same time. By using the evaluation methods to guide the exploration, well PengyeHF-1 was drilled with a strategic breakthrough in SINOPEC marine shale gas exploration.
In recent years, shale gas has become a hot field of global unconventional natural gas and has attracted attentions of many countries and oil companies. However, there are no evaluation methods and criterions of regional selection for marine shale gas in South China. Based on geological background and controlling factors of shale gas accumulation, the paper discussed the ideas and methods of shale gas favorable targets evaluation in the southern China through analogical study of the shale gas accumulation conditions between South China and America. Since the shale age is old and has high thermal evolution degree, the preservation condition is poor and the structure condition and surface condition is complex in South China. Evaluation systems and criterions of regional selection of marine shale gas in South China should take the preservation conditions as the core while considering the geological evaluation and economic evaluation at the same time. By using the evaluation methods to guide the exploration, well PengyeHF-1 was drilled with a strategic breakthrough in SINOPEC marine shale gas exploration.
2014, 21(4):28-32.
Abstract:
Black shales of the lower Cambrian Niutitang formation in the northwestern Guizhou are widespread. The research results about hydrothermal mineralization at home and abroad have been applied into the study of organic-rich black shales. The correlation between hydrothermal characteristic elements and organic matter abundance was analyzed through the sedimentary geochemistry and organic geochemistry test data. Two sets of samples from similar sedimentary environments but different in hydrothermal activities were selected. Ancient productivity and redox environment have been restored. It is proved that hydrothermal activity can provide material basis for the development of marine organisms and increase the paleoproductivity. It will also increase the degree of hypoxia in the anoxic environment and improved organic matter preservation conditions. Overall, favorable conditions can be provided for the development of the source rock.
Black shales of the lower Cambrian Niutitang formation in the northwestern Guizhou are widespread. The research results about hydrothermal mineralization at home and abroad have been applied into the study of organic-rich black shales. The correlation between hydrothermal characteristic elements and organic matter abundance was analyzed through the sedimentary geochemistry and organic geochemistry test data. Two sets of samples from similar sedimentary environments but different in hydrothermal activities were selected. Ancient productivity and redox environment have been restored. It is proved that hydrothermal activity can provide material basis for the development of marine organisms and increase the paleoproductivity. It will also increase the degree of hypoxia in the anoxic environment and improved organic matter preservation conditions. Overall, favorable conditions can be provided for the development of the source rock.
2014, 21(4):33-36.
Abstract:
Exploration and practice have confirmed that natural gas resources are abundant in Sulige, where large gas fields have been found in the north and east. However, gas exploration has no breakthrough in the southern area of Sulige. Based on large amounts of laboratory data analyses and using the method of mathematical statistics, the geologic conditions in the southern region of Sulige have been studied in detail including hydrocarbon conditions, reservoir properties, reservoir-cap portfolio allocation, migration carriers and accumulation conditions. It is revealed that the upper Paleozoic gas reservoirs in the Sulige southern area are favorable of geological conditions which are well-developed overlaying coal-bearing source rocks, large-scale banded sand body distributed from the north west to south east in the block, thick and far-ranging caprock and intermittent and direct caprock. Therefore, a perfect play (source-reservoirseal) of the upper Paleozoic in southern area of Sulige is likely to form under good conditions of accumulation and preservation as lithologic trap; effective carriers for gas migration and near-source lithologic traps can provide good conditions for gas accumulation and preservation. Reservoir evaluation showed that the southern area of Sulige has great exploration potential. Areas of Jingbian-Gaoqiao, Anbian-Wuqi, Anbian-Tiebiancheng and Yanchi-Jiyuan are favorable for future natural gas exploration.
Exploration and practice have confirmed that natural gas resources are abundant in Sulige, where large gas fields have been found in the north and east. However, gas exploration has no breakthrough in the southern area of Sulige. Based on large amounts of laboratory data analyses and using the method of mathematical statistics, the geologic conditions in the southern region of Sulige have been studied in detail including hydrocarbon conditions, reservoir properties, reservoir-cap portfolio allocation, migration carriers and accumulation conditions. It is revealed that the upper Paleozoic gas reservoirs in the Sulige southern area are favorable of geological conditions which are well-developed overlaying coal-bearing source rocks, large-scale banded sand body distributed from the north west to south east in the block, thick and far-ranging caprock and intermittent and direct caprock. Therefore, a perfect play (source-reservoirseal) of the upper Paleozoic in southern area of Sulige is likely to form under good conditions of accumulation and preservation as lithologic trap; effective carriers for gas migration and near-source lithologic traps can provide good conditions for gas accumulation and preservation. Reservoir evaluation showed that the southern area of Sulige has great exploration potential. Areas of Jingbian-Gaoqiao, Anbian-Wuqi, Anbian-Tiebiancheng and Yanchi-Jiyuan are favorable for future natural gas exploration.
2014, 21(4):37-41.
Abstract:
Previous researches on relative sea (lake)-level curve in Pearl River Mouth Basin mainly focused on the Neogene marine basins. Due to data limitations, there are few in-depth studies of the lake level changes of the Paleogene continental basin. Wenchang formation in Enping sag is an important source and reservoir segment, but relative lake-level curve can only be studied according to the seismic data because of no drilling drilled through Wenchang formation. Based on 3D seismic data, the relative lake-level curve of Wenchang period were plotted quantitatively by means of Wheeler transform，then it was compared with the curve qualitatively constructed by traditional onlap reflection. The results show that both curves consistent with each other in the overall trend, but recognition accuracy are different. Quantitative relative lake-level curve has the following advantages: ①High resolution, not only reflects the overall trend of lake level, but also effectively reflects the small magnitude of lake level fluctuations, providing conditions to identify high-level sequence stratigraphic unit;②Objectivity, qualitative relative lake-level curve constructed by onlap reflection are mainly based on human subjectivity with multiple interpretations, while quantitative curve by means of Wheeler transform is more objectivity without human impact and effectively reducing multiple interpretations; ③High efficiency, quantitative automatic sequence stratigraphy tracking effectively reduces the workload of human interpretation and greatly improves work efficiency. Based on the constructed relative lake-level curve, Wenchang formation could be divided into two rifting cycles and further subdivided into seven three-order sequences.
Previous researches on relative sea (lake)-level curve in Pearl River Mouth Basin mainly focused on the Neogene marine basins. Due to data limitations, there are few in-depth studies of the lake level changes of the Paleogene continental basin. Wenchang formation in Enping sag is an important source and reservoir segment, but relative lake-level curve can only be studied according to the seismic data because of no drilling drilled through Wenchang formation. Based on 3D seismic data, the relative lake-level curve of Wenchang period were plotted quantitatively by means of Wheeler transform，then it was compared with the curve qualitatively constructed by traditional onlap reflection. The results show that both curves consistent with each other in the overall trend, but recognition accuracy are different. Quantitative relative lake-level curve has the following advantages: ①High resolution, not only reflects the overall trend of lake level, but also effectively reflects the small magnitude of lake level fluctuations, providing conditions to identify high-level sequence stratigraphic unit;②Objectivity, qualitative relative lake-level curve constructed by onlap reflection are mainly based on human subjectivity with multiple interpretations, while quantitative curve by means of Wheeler transform is more objectivity without human impact and effectively reducing multiple interpretations; ③High efficiency, quantitative automatic sequence stratigraphy tracking effectively reduces the workload of human interpretation and greatly improves work efficiency. Based on the constructed relative lake-level curve, Wenchang formation could be divided into two rifting cycles and further subdivided into seven three-order sequences.
2014, 21(4):42-45.
Abstract:
The characteristics of S1k1 reservior in Shun9 well block of Tazhong were investigated based on the data from core analysis,log, magnetic resonance, rate-controlled mercury penetration, high pressure mercury injection, and observations of scanning electron microscope and thin section. The fine lithic sandstone and fine feldspathic lithic sandstone are the major lithology type of this reservoir which is characterized by low compositional maturity and medium texture maturity. The pore space types of reservoir mainly include the residual of primary intergranular pores, secondary intergranular pores and microfractures. The petrophysical properties of the reservoir are not favorable with low porosity and permeability. The pore structure is complex with medium sorting coefficient, gentle skewness, high displacement pressure, high median pressure, low median radius and efficiency of mercury withdrawal. It is the throat rather than the porosity that controls the permeability of the reservoir because of the small throat radius and high pore throat radio. Affected by the low permeability, the saturation of mobile fluid is low. The compaction and cementation are the key destructive diagenesis and the dissolution is the key constructive diagenesis. They are the major factors that affect the quality of the reservoir. The matrix porosity is 7.13% at the end of the diagenesis evolution of the reservoir. According to the petrophysical properties of reservoir and pore structure parameters, the S1k1 reservoir was classified into 3 types and type I is better than the others.
The characteristics of S1k1 reservior in Shun9 well block of Tazhong were investigated based on the data from core analysis,log, magnetic resonance, rate-controlled mercury penetration, high pressure mercury injection, and observations of scanning electron microscope and thin section. The fine lithic sandstone and fine feldspathic lithic sandstone are the major lithology type of this reservoir which is characterized by low compositional maturity and medium texture maturity. The pore space types of reservoir mainly include the residual of primary intergranular pores, secondary intergranular pores and microfractures. The petrophysical properties of the reservoir are not favorable with low porosity and permeability. The pore structure is complex with medium sorting coefficient, gentle skewness, high displacement pressure, high median pressure, low median radius and efficiency of mercury withdrawal. It is the throat rather than the porosity that controls the permeability of the reservoir because of the small throat radius and high pore throat radio. Affected by the low permeability, the saturation of mobile fluid is low. The compaction and cementation are the key destructive diagenesis and the dissolution is the key constructive diagenesis. They are the major factors that affect the quality of the reservoir. The matrix porosity is 7.13% at the end of the diagenesis evolution of the reservoir. According to the petrophysical properties of reservoir and pore structure parameters, the S1k1 reservoir was classified into 3 types and type I is better than the others.
11 Genetic analysis and reservoir characteristics of Sha3 igneous in eastern sag of Liaohe depression
2014, 21(4):46-49.
Abstract:
In order to expand exploration space of Sha3 igneous in eastern sag, Liaohe depression, using core observation, thin-section analysis, seismic and logging methods, genesis and reservoir characteristics of igneous rock were studied thoroughly in Sha3 member in eastern sag. The results show that the igneous develops well in the layer of that area, presenting beaded distribution along faults and multi-stage superimposed. The major three rock types are lava, vein rock and pyroclastic rock. Volcanic erupted following the fissure pattern and igneous mainly distributed in the downthrown of faults. The major petrographic types are outbreak, overflow and volcanic sedimentary facies. Among them, the outbreak facies are the most favorable ones for igneous exploration. Main faults control igneous formation mechanism. The igneous rock belongs to fracture-pore type reservoir and its reservoir property is controlled by the factors of structural fracture, igneous lithology and lithofacies. Comprehensive evaluation shows that the igneous in the study area is characteristic of widespread distribution in horizontal, multi-stage superposition in vertical, and adjacent to the deep source rocks in lateral. It is favorable for the formation of complex reservoirs and also is the key target area for deep igneous exploration.
In order to expand exploration space of Sha3 igneous in eastern sag, Liaohe depression, using core observation, thin-section analysis, seismic and logging methods, genesis and reservoir characteristics of igneous rock were studied thoroughly in Sha3 member in eastern sag. The results show that the igneous develops well in the layer of that area, presenting beaded distribution along faults and multi-stage superimposed. The major three rock types are lava, vein rock and pyroclastic rock. Volcanic erupted following the fissure pattern and igneous mainly distributed in the downthrown of faults. The major petrographic types are outbreak, overflow and volcanic sedimentary facies. Among them, the outbreak facies are the most favorable ones for igneous exploration. Main faults control igneous formation mechanism. The igneous rock belongs to fracture-pore type reservoir and its reservoir property is controlled by the factors of structural fracture, igneous lithology and lithofacies. Comprehensive evaluation shows that the igneous in the study area is characteristic of widespread distribution in horizontal, multi-stage superposition in vertical, and adjacent to the deep source rocks in lateral. It is favorable for the formation of complex reservoirs and also is the key target area for deep igneous exploration.
2014, 21(4):50-53.
Abstract:
The structural-depositional framework of Dongpu sag has a zonation from east to west and north to south. Through comprehensive analysis on the ratio of extensional and downfaulted rate and volcanic distribution, it is suggested that depositional period in Sha3 member is favorable to large-scale development of the hydrocarbon source rocks due to the small extensional rate and fast downfaulted rate and inactive volcanic activity in the north of Dongpu sag; thus that the south of Dongpu sag is not good for the development of the hydrocarbon source rocks in comparison. The structural-depositional evolution in the research area has impact on spatial combination of reservoirs and cap rocks and oil-gas migration and accumulation model. Abnormal pressure develops in Dongpu sag and the pressure decreases gradually from the subsag belt to the central uplift belt and western slope belt. So the central uplift belt and western slope belt become the directional areas of centrifugal flow that can provide favorable hydrodynamic condition for oil-gas accumulation under the role of buoyancy. The northern research area is more favorable for oil-gas accumulation than the south for better source-reservoir-seal combination and migration-accumulation conditions.
The structural-depositional framework of Dongpu sag has a zonation from east to west and north to south. Through comprehensive analysis on the ratio of extensional and downfaulted rate and volcanic distribution, it is suggested that depositional period in Sha3 member is favorable to large-scale development of the hydrocarbon source rocks due to the small extensional rate and fast downfaulted rate and inactive volcanic activity in the north of Dongpu sag; thus that the south of Dongpu sag is not good for the development of the hydrocarbon source rocks in comparison. The structural-depositional evolution in the research area has impact on spatial combination of reservoirs and cap rocks and oil-gas migration and accumulation model. Abnormal pressure develops in Dongpu sag and the pressure decreases gradually from the subsag belt to the central uplift belt and western slope belt. So the central uplift belt and western slope belt become the directional areas of centrifugal flow that can provide favorable hydrodynamic condition for oil-gas accumulation under the role of buoyancy. The northern research area is more favorable for oil-gas accumulation than the south for better source-reservoir-seal combination and migration-accumulation conditions.
2014, 21(4):54-57.
Abstract:
Through the analysis of geochemical characteristics of core samples, it is showed that volcano rocks are mainly basalt and trachyandesite in Chagan depression and the rock type can be identified better by logging crossplot. Based on morphological sign of volcano rock lithofacies, seismic profiles and single well facies, the main facies developed in Chagan depression are determined as volcano channel facies, explosive facies, overflow facies and volcano sedimentary facies. And different rock lithofacies have different type of rock combinations. Drilling data reveal that volcano rock of Su2 has medium porosity and extra-low permeability, which is better than that of Su1 extra-low porosity and extra-low permeability; the petrophysical properties of the volcano reservoir are mainly controlled by fracture development withstrong heterogeneity. Exploration practice shows that the oil and gas accumulations in volcano reservoirs in Chagan depression are characteristic of near-source accumulation, an joint control of good quality reservoir and fracture zone; Uligi structural belt and the central structural belt are favorable areas for oil & gas accumulation, which are near the hydrocarbon generation center and have favorable fractures to increase the reservoir space and facilitate the way to hydrocarbon source rocks.
Through the analysis of geochemical characteristics of core samples, it is showed that volcano rocks are mainly basalt and trachyandesite in Chagan depression and the rock type can be identified better by logging crossplot. Based on morphological sign of volcano rock lithofacies, seismic profiles and single well facies, the main facies developed in Chagan depression are determined as volcano channel facies, explosive facies, overflow facies and volcano sedimentary facies. And different rock lithofacies have different type of rock combinations. Drilling data reveal that volcano rock of Su2 has medium porosity and extra-low permeability, which is better than that of Su1 extra-low porosity and extra-low permeability; the petrophysical properties of the volcano reservoir are mainly controlled by fracture development withstrong heterogeneity. Exploration practice shows that the oil and gas accumulations in volcano reservoirs in Chagan depression are characteristic of near-source accumulation, an joint control of good quality reservoir and fracture zone; Uligi structural belt and the central structural belt are favorable areas for oil & gas accumulation, which are near the hydrocarbon generation center and have favorable fractures to increase the reservoir space and facilitate the way to hydrocarbon source rocks.
2014, 21(4):58-61.
Abstract:
Oil saturation is an important parameter in evaluation of oil and gas resources. It is difficult to calculate the oil saturation in mud shale formation because the saturation models using today are mainly for sandstone and argillaceous sandstone reservoir. An example from Zhanhua sag has been analyzed. It is pointed out that the major space is fracture and micropore in this kind of reservoir. The conductive mechanism is also analyzed based on the experiment data. On basis of the pore structure exponent m and saturation exponent n, the oil saturation of shale formations was calculated using the Archie formula. The results show that the saturation and coring analysis data achieve a good match in numerical value. Archie formula is a practical equation which is based on the theoretical analysis of physical model and improved by the actual core experimental verification. Therefore, Archie formula can be used to calculate water saturation and meet the demand of calculating accuracy when the log interpretation theory for shale formation is not mature.
Oil saturation is an important parameter in evaluation of oil and gas resources. It is difficult to calculate the oil saturation in mud shale formation because the saturation models using today are mainly for sandstone and argillaceous sandstone reservoir. An example from Zhanhua sag has been analyzed. It is pointed out that the major space is fracture and micropore in this kind of reservoir. The conductive mechanism is also analyzed based on the experiment data. On basis of the pore structure exponent m and saturation exponent n, the oil saturation of shale formations was calculated using the Archie formula. The results show that the saturation and coring analysis data achieve a good match in numerical value. Archie formula is a practical equation which is based on the theoretical analysis of physical model and improved by the actual core experimental verification. Therefore, Archie formula can be used to calculate water saturation and meet the demand of calculating accuracy when the log interpretation theory for shale formation is not mature.
2014, 21(4):62-66.
Abstract:
At present for the shallow extra low permeability reservoir, displacement efficiency in drainage development is poor and it is difficult for water injection. Whereas, nitrogen gas flooding technology has provided a potential effective means for recovery improvement in extra low permeability area. Combining the field characteristics, through indoor nitrogen displacement experiments in extra low permeability core after a period of water flooding, influence of nitrogen injection parameters on recovery was analyzed. The effects of nitrogen/water alternating injection and pure nitrogen flooding were compared and water/nitrogen flooding slug ratio was optimized. Indoor experiments on natural and artificial cores have proved that nitrogen displacement after water flooding could improve the recovery of 3%-10% and increase the fluid injection pressure, while better gas flooding effect would be achieved under lower water content.There is a new recognition that step rise existed in gas injection amount versus nitrogen gas flooding recovery, which means that gas injection amount can be optimized according to field requirements. Compared with nitrogen flooding, nitrogen/water alternating injection had an obviously increase in recovery and injection pressure that reached the largest value at sixth nitrogen/water alternating injection rounds; in addition, the optimized gas/water slug ratio was 2∶1.
At present for the shallow extra low permeability reservoir, displacement efficiency in drainage development is poor and it is difficult for water injection. Whereas, nitrogen gas flooding technology has provided a potential effective means for recovery improvement in extra low permeability area. Combining the field characteristics, through indoor nitrogen displacement experiments in extra low permeability core after a period of water flooding, influence of nitrogen injection parameters on recovery was analyzed. The effects of nitrogen/water alternating injection and pure nitrogen flooding were compared and water/nitrogen flooding slug ratio was optimized. Indoor experiments on natural and artificial cores have proved that nitrogen displacement after water flooding could improve the recovery of 3%-10% and increase the fluid injection pressure, while better gas flooding effect would be achieved under lower water content.There is a new recognition that step rise existed in gas injection amount versus nitrogen gas flooding recovery, which means that gas injection amount can be optimized according to field requirements. Compared with nitrogen flooding, nitrogen/water alternating injection had an obviously increase in recovery and injection pressure that reached the largest value at sixth nitrogen/water alternating injection rounds; in addition, the optimized gas/water slug ratio was 2∶1.
2014, 21(4):67-70.
Abstract:
A number of heavy oil reservoirs show anomalously good primary performance under cold heavy oil production. Foamy oil behavior is believed to be the main reason. Previous numerical simulation of primary depletion in foamy oil reservoirs is still based primarily on empirical adjustments to the conventional solution gas drive models. While these models do not involve the gas dynamic process? es in foamy oil flow. This paper presents a numerical model including the non-equilibrium rate processes of the foamy oil. The model was tested by the primary depletion experiment and investigates the effects of various process parameters on oil recovery. It was observed that higher oil recovery was predicted under higher pressure decline rate. The maximum volume of the oil decreases as the gas decay coefficient λs increases. And the greater the bubble growth index b is, the later the foamy oil forms.
A number of heavy oil reservoirs show anomalously good primary performance under cold heavy oil production. Foamy oil behavior is believed to be the main reason. Previous numerical simulation of primary depletion in foamy oil reservoirs is still based primarily on empirical adjustments to the conventional solution gas drive models. While these models do not involve the gas dynamic process? es in foamy oil flow. This paper presents a numerical model including the non-equilibrium rate processes of the foamy oil. The model was tested by the primary depletion experiment and investigates the effects of various process parameters on oil recovery. It was observed that higher oil recovery was predicted under higher pressure decline rate. The maximum volume of the oil decreases as the gas decay coefficient λs increases. And the greater the bubble growth index b is, the later the foamy oil forms.
2014, 21(4):71-74.
Abstract:
The post evaluation is the last and indispensable procedure of the project life cycle, but the operation of the method is too complex and needs heavy computation, so it is difficult for implementation. The key to the method for the comprehensive assessment for the post evaluation of the project is to establish a system that both meets the requirement of the post evaluation on the project and provides the evaluation index and weight coefficient for the project objective. Also, the post evaluation of the sustainability and the degree of success can be conducted by the system. The method was discussed by integrating combination evaluation method with the success degree method and modifying and taking the secondary development project as the case. The method is characterized of simple, reliable, comparable, objective and operable. The simple method can be applied to the non-detail post evaluation and it is easy to be popularized and applied.
The post evaluation is the last and indispensable procedure of the project life cycle, but the operation of the method is too complex and needs heavy computation, so it is difficult for implementation. The key to the method for the comprehensive assessment for the post evaluation of the project is to establish a system that both meets the requirement of the post evaluation on the project and provides the evaluation index and weight coefficient for the project objective. Also, the post evaluation of the sustainability and the degree of success can be conducted by the system. The method was discussed by integrating combination evaluation method with the success degree method and modifying and taking the secondary development project as the case. The method is characterized of simple, reliable, comparable, objective and operable. The simple method can be applied to the non-detail post evaluation and it is easy to be popularized and applied.
2014, 21(4):75-78.
Abstract:
A new technology named multi-thermal fluids, as an innovative technology for offshore heavy oil, has been used in pilot test of Bohai oilfield, but the mechanism of multi-thermal fluids on enhanced oil recovery and reservoir adaptability has still not enough indepth research. Through theoretical analysis, numerical simulation and experiment analysis, the stimulation mechanism of components in multi-thermal fluids and the coupling of components was studied to discuss the mechanism of multi-thermal fluids on enhanced oil recovery; at the same time, based on crude oil viscosity, permeability, heterogeneity parameters and other data from heavy oil reservoirs in Bohai oilfield, the effect of multi-thermal fluids and the adapted reservoir conditions were compared with steam stimulation. The results show that: compared with steam stimulation, the multi-thermal fluid can enlarge heating volume, increase formation energy, reduce heat loss, and so on, but it carries less total enthalpy. As a result, multi-thermal fluids technology is more suitable for the heavy oil reservoirs which have relatively low oil viscosity, weak heterogeneity, thin oil layer and small natural energy.
A new technology named multi-thermal fluids, as an innovative technology for offshore heavy oil, has been used in pilot test of Bohai oilfield, but the mechanism of multi-thermal fluids on enhanced oil recovery and reservoir adaptability has still not enough indepth research. Through theoretical analysis, numerical simulation and experiment analysis, the stimulation mechanism of components in multi-thermal fluids and the coupling of components was studied to discuss the mechanism of multi-thermal fluids on enhanced oil recovery; at the same time, based on crude oil viscosity, permeability, heterogeneity parameters and other data from heavy oil reservoirs in Bohai oilfield, the effect of multi-thermal fluids and the adapted reservoir conditions were compared with steam stimulation. The results show that: compared with steam stimulation, the multi-thermal fluid can enlarge heating volume, increase formation energy, reduce heat loss, and so on, but it carries less total enthalpy. As a result, multi-thermal fluids technology is more suitable for the heavy oil reservoirs which have relatively low oil viscosity, weak heterogeneity, thin oil layer and small natural energy.
2014, 21(4):79-83.
Abstract:
The author has studied the percolation characteristics and displacement mechanism of fractured reservoir by dual-media numerical simulation in detail, as well as sensitivity analysis of the impact of development effect. The results show that the rock stress sensitivity is the key to decide fractured reservoir development strategy. It decides the development model, the ability to maintain reservoir pressures and the recovery of matrix system and fracture system. The crossflow between matrix system and fracture system is very difficult to occur in natural or artificial water energy that sufficient to maintain reservoir pressure. It only appears in the development process of reducing reservoir pressure. Regarding the matrix system, capillary pressure dialysis is the most important percolation characteristics and displacement mechanism. Its recovery ratio may reach over 4%. Regarding the fracture system, the displacement process depends on the external driving pressure differential and is characteristic of pipe flow. Its recovery ratio may reach over 75%. Gravity exists objectively but is rather weak. In process of numerical simulation of fractured reservoir, the oil-water relative permeability curve shape of matrix system and fracture system mainly affects the rise law of water cut, but little on recovery.
The author has studied the percolation characteristics and displacement mechanism of fractured reservoir by dual-media numerical simulation in detail, as well as sensitivity analysis of the impact of development effect. The results show that the rock stress sensitivity is the key to decide fractured reservoir development strategy. It decides the development model, the ability to maintain reservoir pressures and the recovery of matrix system and fracture system. The crossflow between matrix system and fracture system is very difficult to occur in natural or artificial water energy that sufficient to maintain reservoir pressure. It only appears in the development process of reducing reservoir pressure. Regarding the matrix system, capillary pressure dialysis is the most important percolation characteristics and displacement mechanism. Its recovery ratio may reach over 4%. Regarding the fracture system, the displacement process depends on the external driving pressure differential and is characteristic of pipe flow. Its recovery ratio may reach over 75%. Gravity exists objectively but is rather weak. In process of numerical simulation of fractured reservoir, the oil-water relative permeability curve shape of matrix system and fracture system mainly affects the rise law of water cut, but little on recovery.
2014, 21(4):84-88.
Abstract:
In view of the characteristics of high hardness, high temperature and high salt in Tazhong 402CⅢ reservoir, the foam agent was selected by means of experiments of compatibility, foamability and thermal stability. The operation parameters were ascertained by physical simulation experiment. Oil displacement experiment was also conducted under the reservoir condition. The results indicate that，under the reservoir condition (temperature 110 ℃, salinity 11.52×104 mg/L, Ca2+&Mg2+ 7 654 mg/L), CS-1 was optimized as foaming agent for foam flooding and the working concentration was 0.2%-0.3%. Gas-liquid mixed injection with gas liquid ratio of 1.5∶1, 1 mL/min of injection rate and 0.5 PV of injection quantity were the best operation parameters of foam flooding. And oil displacement ex? periment shows water flooding recovery increases by 4.12% on the basis of 56.63%. It can provide reference to further enhance oil recovery (EOR) of the high temperature and high salt oil fields.
In view of the characteristics of high hardness, high temperature and high salt in Tazhong 402CⅢ reservoir, the foam agent was selected by means of experiments of compatibility, foamability and thermal stability. The operation parameters were ascertained by physical simulation experiment. Oil displacement experiment was also conducted under the reservoir condition. The results indicate that，under the reservoir condition (temperature 110 ℃, salinity 11.52×104 mg/L, Ca2+&Mg2+ 7 654 mg/L), CS-1 was optimized as foaming agent for foam flooding and the working concentration was 0.2%-0.3%. Gas-liquid mixed injection with gas liquid ratio of 1.5∶1, 1 mL/min of injection rate and 0.5 PV of injection quantity were the best operation parameters of foam flooding. And oil displacement ex? periment shows water flooding recovery increases by 4.12% on the basis of 56.63%. It can provide reference to further enhance oil recovery (EOR) of the high temperature and high salt oil fields.
2014, 21(4):89-92.
Abstract:
The wettability of rock is a combined effect of rock, crude oil and water. It has direct impact on the distribution of the fluid in the reservoir and determines the degree of difficulty of the fluid percolation. Reservoir rock wettability research is of significance to determine a reasonable flooding way and enhanced oil recovery. In order to find out the carbonate reservoir core wettability and its influencing factors, Amott method was used to measure the wettability and imbibitions recovery degree of carbonate rocks and the wettability changes of carbonate rocks after steam flooding. At the same time, in order to do qualitative test for the wettability of carbonate rocks,the oil-water flowing experiment under both reservoir and high temperature(150 ℃) was carried out. The results show that: the carbonate reservoir core is oil wetting or weak oil wetting, and the reservoir seepage resistance is high, which is different from the ordinary sandstone reservoir’s water wetting characteristics; studies suggest that the rock mineral composition and the different constituents of crude oil are the main reasons that cause the differences; steam flooding could cause the decrease of carbonate rocks wetting index to improve the rock’s wettability at certain extent, and also the reservoir’s seepage. The oil-water relative permeability experiment on this core further proved the conclusion. This understanding can provide a theoretical basis for the optimization of development schemes.
The wettability of rock is a combined effect of rock, crude oil and water. It has direct impact on the distribution of the fluid in the reservoir and determines the degree of difficulty of the fluid percolation. Reservoir rock wettability research is of significance to determine a reasonable flooding way and enhanced oil recovery. In order to find out the carbonate reservoir core wettability and its influencing factors, Amott method was used to measure the wettability and imbibitions recovery degree of carbonate rocks and the wettability changes of carbonate rocks after steam flooding. At the same time, in order to do qualitative test for the wettability of carbonate rocks,the oil-water flowing experiment under both reservoir and high temperature(150 ℃) was carried out. The results show that: the carbonate reservoir core is oil wetting or weak oil wetting, and the reservoir seepage resistance is high, which is different from the ordinary sandstone reservoir’s water wetting characteristics; studies suggest that the rock mineral composition and the different constituents of crude oil are the main reasons that cause the differences; steam flooding could cause the decrease of carbonate rocks wetting index to improve the rock’s wettability at certain extent, and also the reservoir’s seepage. The oil-water relative permeability experiment on this core further proved the conclusion. This understanding can provide a theoretical basis for the optimization of development schemes.
22 Laboratory research on nitrogen foam injection in fracture-vuggy reservoir for enhanced oil recovery
2014, 21(4):93-96.
Abstract:
A visualized physical model was designed according to the similarity theory. The remaining oil development effects of nitrogen gas injection and nitrogen foam injection after bottom water driving were studied comparatively and EOR mechanisms for nitrogen foam flooding was analyzed through physical simulation. Experimental results illustrate that the remaining oil exists as the“attic oil”after bottom water driving. Both the nitrogen gas injection and nitrogen foam injection can displace remaining oil effectively. However,the foam flooding can enhance sweep efficiency through the effect of mobility control and plugging, adding that foam has a higher displacement efficiency in swept region, which leads to a higher ultimate recovery than gas injection. The experiments show a possible way to tap remaining oil and enhance oil recovery for the carbonate fracture-vuggy reservoir after bottom water driving.
A visualized physical model was designed according to the similarity theory. The remaining oil development effects of nitrogen gas injection and nitrogen foam injection after bottom water driving were studied comparatively and EOR mechanisms for nitrogen foam flooding was analyzed through physical simulation. Experimental results illustrate that the remaining oil exists as the“attic oil”after bottom water driving. Both the nitrogen gas injection and nitrogen foam injection can displace remaining oil effectively. However,the foam flooding can enhance sweep efficiency through the effect of mobility control and plugging, adding that foam has a higher displacement efficiency in swept region, which leads to a higher ultimate recovery than gas injection. The experiments show a possible way to tap remaining oil and enhance oil recovery for the carbonate fracture-vuggy reservoir after bottom water driving.
2014, 21(4):97-100.
Abstract:
Since the permeability of gas shale is extremely low, hydraulic fracturing is the main measure to obtain an economic shale gas productivity. Shale reservoirs have long production cycles and artificial fracture conductivity is extremely sensitive to the fracture deformation. A large number of narrow self-supporting fractures play an important role in the gas desorption and flow. Shale reservoir has a certain creep characteristic, its creep rate increases with the clay content. After fracturing, the reservoir generates a large number of cracks and crack-closure creep is the main part. Fracturing treatment greatly increases the reservoir creep rate and the impacts of creep on the fracture conductivity cannot be ignored. The fracture closure creep rate is related to the interactions between fracture interfaces and proppant. It is also proportional to the matrix creep rate. Complex fracture network and tiny fractures have larger creep rate and greater effects on flow conductivity. Therefore, the creep deformation of fractures should be taken into account in shale gas numerical simulation. And, in-situ stress calculation and proppant selection should also consider the effect of creep. Maintaining fluid pressure is helpful to enhance fracture conductivity and improve gas well productivity and recovery.
Since the permeability of gas shale is extremely low, hydraulic fracturing is the main measure to obtain an economic shale gas productivity. Shale reservoirs have long production cycles and artificial fracture conductivity is extremely sensitive to the fracture deformation. A large number of narrow self-supporting fractures play an important role in the gas desorption and flow. Shale reservoir has a certain creep characteristic, its creep rate increases with the clay content. After fracturing, the reservoir generates a large number of cracks and crack-closure creep is the main part. Fracturing treatment greatly increases the reservoir creep rate and the impacts of creep on the fracture conductivity cannot be ignored. The fracture closure creep rate is related to the interactions between fracture interfaces and proppant. It is also proportional to the matrix creep rate. Complex fracture network and tiny fractures have larger creep rate and greater effects on flow conductivity. Therefore, the creep deformation of fractures should be taken into account in shale gas numerical simulation. And, in-situ stress calculation and proppant selection should also consider the effect of creep. Maintaining fluid pressure is helpful to enhance fracture conductivity and improve gas well productivity and recovery.
2014, 21(4):101-103.
Abstract:
The pressure gradient between the injection and production wells is the core of displacement slug length optimization in the decision-making process of profile modification. However, displacement slug length calculation method is based on experience and lack of theoretical basis currently. In this article, seepage mechanics theory is used to calculate the interwell pressure gradient under the premise of the homogeneous reservoir. The influence of different injection-production well spacing on interwell pressure gradient was analyzed. The finite element numerical simulation was used to calculate the interwell pressure gradient under high permeable zone and profile modification. The influence of different geological conditions and development conditions on interwell pressure gradient was analyzed. Through this article’s demonstration, the permeability of high permeable zone has little influence on interwell pressure gradient. The profile control treatment has great influence on interwell pressure gradient and the plugging agent slug sustain major pressure drop between injection and production wells. An interval of less than 10 meters from the bottom of the well is the main pressure drop zone. It is recommended to inject a 10 meters displacement slug after injecting the major gels.
The pressure gradient between the injection and production wells is the core of displacement slug length optimization in the decision-making process of profile modification. However, displacement slug length calculation method is based on experience and lack of theoretical basis currently. In this article, seepage mechanics theory is used to calculate the interwell pressure gradient under the premise of the homogeneous reservoir. The influence of different injection-production well spacing on interwell pressure gradient was analyzed. The finite element numerical simulation was used to calculate the interwell pressure gradient under high permeable zone and profile modification. The influence of different geological conditions and development conditions on interwell pressure gradient was analyzed. Through this article’s demonstration, the permeability of high permeable zone has little influence on interwell pressure gradient. The profile control treatment has great influence on interwell pressure gradient and the plugging agent slug sustain major pressure drop between injection and production wells. An interval of less than 10 meters from the bottom of the well is the main pressure drop zone. It is recommended to inject a 10 meters displacement slug after injecting the major gels.
2014, 21(4):104-106.
Abstract:
As the oilfield development goes longer, the economic benefits generated by infill well become lower year by year. And the economic limit well pattern becomes the key factor for oilfield development decision making. Based on traditional well pattern calculation method, the well spacing and average well-controlled recoverable reserves of infill wells in 15 typical development units at different stages were studied, and the relationship between well spacing and well-controlled recoverable reserves were set up. Combining with the study of economic limit for well-controlled recoverable reserves, a new method to calculate the economic limit well pattern for old oilfields has been established. By using this new method to calculate the well pattern based on economic limit for No.2 district of Shengtuo oilfield under different oil prices, the results showed that it has potential for infill wells under high oil price, and the higher the oil price, the greater the potential for more infill wells.
As the oilfield development goes longer, the economic benefits generated by infill well become lower year by year. And the economic limit well pattern becomes the key factor for oilfield development decision making. Based on traditional well pattern calculation method, the well spacing and average well-controlled recoverable reserves of infill wells in 15 typical development units at different stages were studied, and the relationship between well spacing and well-controlled recoverable reserves were set up. Combining with the study of economic limit for well-controlled recoverable reserves, a new method to calculate the economic limit well pattern for old oilfields has been established. By using this new method to calculate the well pattern based on economic limit for No.2 district of Shengtuo oilfield under different oil prices, the results showed that it has potential for infill wells under high oil price, and the higher the oil price, the greater the potential for more infill wells.
2014, 21(4):107-110.
Abstract:
In order to improve the reserve utilization and petroleum recovery of low permeability reservoir, we summarized the study results of Boxing low permeability reservoir and other related information; in the way of combining theoretical research and laboratory experiment, we studied percolation mechanism of the low permeability reservoirs. According to the corresponding percolation character of low permeability reservoir with different permeability grades, ordinary low permeability, extra low permeability and super low permeability are divided. For the extra low permeability and super low permeability reservoirs which are difficult to exploit, various differential development techniques such as normal water-injection, small well-distance water-injection, large-scale suppression with no waterinjection,gas-driving method and irregular method of long-distance level well exploitation were adopted, which have achieved promi? nent technical progress. We also evaluated the suitability of the technique used in low permeability development. We propose that the fluid in the low permeability reservoir is possessed with certain flowing ability, and all of the low permeability reservoirs could be exploited efficiently by using differential development technique to improve the percolation condition.
In order to improve the reserve utilization and petroleum recovery of low permeability reservoir, we summarized the study results of Boxing low permeability reservoir and other related information; in the way of combining theoretical research and laboratory experiment, we studied percolation mechanism of the low permeability reservoirs. According to the corresponding percolation character of low permeability reservoir with different permeability grades, ordinary low permeability, extra low permeability and super low permeability are divided. For the extra low permeability and super low permeability reservoirs which are difficult to exploit, various differential development techniques such as normal water-injection, small well-distance water-injection, large-scale suppression with no waterinjection,gas-driving method and irregular method of long-distance level well exploitation were adopted, which have achieved promi? nent technical progress. We also evaluated the suitability of the technique used in low permeability development. We propose that the fluid in the low permeability reservoir is possessed with certain flowing ability, and all of the low permeability reservoirs could be exploited efficiently by using differential development technique to improve the percolation condition.
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