Reservoir quality is one of the important geological factors controlling the development of tight oil in the Honghe oilfield,Ordos Basin,northwestern China.Analyses of core,well logging,mud logging and geophysical dat...Reservoir quality is one of the important geological factors controlling the development of tight oil in the Honghe oilfield,Ordos Basin,northwestern China.Analyses of core,well logging,mud logging and geophysical data as well as thin sections(casting and fluorescence)were combined with testing methods(such as grain size analysis,constant-rate mercury injection,and scanning electron microscopy)to characterize the microporeethroat development in reservoirs of the eighth member of Yanchang For-mation in the oilfield.From the perspective of sedimentation and diagenesis,the mechanisms causing reservoir quality difference were explored and a method for characterizing reservoir quality difference and distribution was proposed.The results show that complex and diverse poreethroat configurations and multi-scale throat development are the microscale manifestations of reservoir quality differences in the member.Three types of poreethroat combinations are recognized,including intergranular pore-wide lamellar throat,intergranular and intragranular pore-wide lamellar throat,and intergranular/clustered micropore-wide lamellar throat.Different diagenesis processes and intensities under the control of sedimentary conditions determine the differential development of the reservoirs.Diagenetic facies are the indicators of reservoir quality.Diagenetic facies with chlorite cementation-moderate dissolution indicates reservoirs with the most ideal physical properties for hydrocarbon accumulation,while that with moderate calcite and kaolinite cementations are usually observed in reservoirs with less ideal physical properties.Reservoirs with the worst physical properties often correlate with diagenetic facies with strong calcite cementation and compaction facies.A multi-level constrained method under the control of sedimentation and diagenetic facies is proposed for characterizing tight reservoir quality difference in the member.The spatial distribution of sedimentary elements is analyzed through sedi-mentary configurations,the diagenetic facies distribution is constrained by sedimentary elements and the reservoir quality distribution is predicted with constraint of diagenetic facies.It suggests that the high-quality reservoirs in the member occur vertically in the middle of thick channel sandstone,while poor reservoirs occur in the upper or lower parts of the channel sandstone due to intensive compaction and cementation.Laterally,the quality of reservoirs enhances along the channels with a change in shape to lens or strips along the middle and downstream sections.展开更多
Research and development of water lock inhibiting measures is very crucial in verifying the link mechanism between the internal factors of water lock and its extent of damage.Based on conventional water-lock physics e...Research and development of water lock inhibiting measures is very crucial in verifying the link mechanism between the internal factors of water lock and its extent of damage.Based on conventional water-lock physics experiments,however,only the consequence of macro water lock damage can be investigated,while the microscopic mechanism cannot be studied.In this paper,3D digital cores of low-permeability sandstones were prepared by means of high-resolution micro-CT scan,and their equivalent pore network model was built as well.Virtual“imbibition”experiments controlled by capillary force were carried out by using pore-scale flow simulation.Then the link mechanism between the microscopic internal factors(e.g.wettability,water saturation and pore-throat structure parameters)and the water-lock damage degree was discussed.It is shown that the damage degree of water lock reduces gradually as the wettability transits from water wet to gas wet.Therefore,the water lock damage can be reduced effectively and gas-well productivity can be improved so long as the capillary environment is changed from strong water wettability to weak gas wettability.The more different the initial water saturation is from the irreducible water saturation,the more serious the water lock damage is.The damage degree of water lock is in a negative correlation with the coordinate number,but a positive correlation with the poreethroat ratio.Based on the existing research results,water lock tends to form in the formations composed of mediumsized throats.It is concluded that there is a critical throat radius,at which the water lock is the most serious.展开更多
基金Sponsored by the Key Research Project of Sinopec Science and Technology Department(Grant No.G5800-17-ZS-KJB010).
文摘Reservoir quality is one of the important geological factors controlling the development of tight oil in the Honghe oilfield,Ordos Basin,northwestern China.Analyses of core,well logging,mud logging and geophysical data as well as thin sections(casting and fluorescence)were combined with testing methods(such as grain size analysis,constant-rate mercury injection,and scanning electron microscopy)to characterize the microporeethroat development in reservoirs of the eighth member of Yanchang For-mation in the oilfield.From the perspective of sedimentation and diagenesis,the mechanisms causing reservoir quality difference were explored and a method for characterizing reservoir quality difference and distribution was proposed.The results show that complex and diverse poreethroat configurations and multi-scale throat development are the microscale manifestations of reservoir quality differences in the member.Three types of poreethroat combinations are recognized,including intergranular pore-wide lamellar throat,intergranular and intragranular pore-wide lamellar throat,and intergranular/clustered micropore-wide lamellar throat.Different diagenesis processes and intensities under the control of sedimentary conditions determine the differential development of the reservoirs.Diagenetic facies are the indicators of reservoir quality.Diagenetic facies with chlorite cementation-moderate dissolution indicates reservoirs with the most ideal physical properties for hydrocarbon accumulation,while that with moderate calcite and kaolinite cementations are usually observed in reservoirs with less ideal physical properties.Reservoirs with the worst physical properties often correlate with diagenetic facies with strong calcite cementation and compaction facies.A multi-level constrained method under the control of sedimentation and diagenetic facies is proposed for characterizing tight reservoir quality difference in the member.The spatial distribution of sedimentary elements is analyzed through sedi-mentary configurations,the diagenetic facies distribution is constrained by sedimentary elements and the reservoir quality distribution is predicted with constraint of diagenetic facies.It suggests that the high-quality reservoirs in the member occur vertically in the middle of thick channel sandstone,while poor reservoirs occur in the upper or lower parts of the channel sandstone due to intensive compaction and cementation.Laterally,the quality of reservoirs enhances along the channels with a change in shape to lens or strips along the middle and downstream sections.
基金Project supported by the National Natural Science Foundation of China for the Youth,“Study on the Effect of Shale Bedding Architecture on Features of Ultrasonic Wave and Its Application”(No.41502287)the S&T Program of Chongqing Land and Resources Bureau“Evaluation on Gas Saturation in Shale based on Digital Core Technology”(No.CQGT-KJ-2015018)Sinopec Key Geophysical Laboratory Open Fund Project“Apparent Characteristics of Shale Reservoir and Digital Rock Physics Laboratory Study”(No.33550006-15-FW2099-0015).
文摘Research and development of water lock inhibiting measures is very crucial in verifying the link mechanism between the internal factors of water lock and its extent of damage.Based on conventional water-lock physics experiments,however,only the consequence of macro water lock damage can be investigated,while the microscopic mechanism cannot be studied.In this paper,3D digital cores of low-permeability sandstones were prepared by means of high-resolution micro-CT scan,and their equivalent pore network model was built as well.Virtual“imbibition”experiments controlled by capillary force were carried out by using pore-scale flow simulation.Then the link mechanism between the microscopic internal factors(e.g.wettability,water saturation and pore-throat structure parameters)and the water-lock damage degree was discussed.It is shown that the damage degree of water lock reduces gradually as the wettability transits from water wet to gas wet.Therefore,the water lock damage can be reduced effectively and gas-well productivity can be improved so long as the capillary environment is changed from strong water wettability to weak gas wettability.The more different the initial water saturation is from the irreducible water saturation,the more serious the water lock damage is.The damage degree of water lock is in a negative correlation with the coordinate number,but a positive correlation with the poreethroat ratio.Based on the existing research results,water lock tends to form in the formations composed of mediumsized throats.It is concluded that there is a critical throat radius,at which the water lock is the most serious.
