The Quantitative Fault Sealing And Its Controlling Effect On Oil And Gas Accumulation In Gaoyou Depression

Taking slope area of Gaoyou Sag in North Jiangsu Basin as research object,on the basis of fault observation and description,combined with regional geological background analysis,a great deal of investigation and research on fault sealing mechanism and sealing type of clastic rock are carried out.Based on the calibration principle and method of fault sealing ability,the oil-water anatomy of related traps is carried out,and a set of evaluation models for lateral sealing ability of fault is established finally.Based on the statistics of fault distance,reservoir thickness and cover thickness in slope area of Gaoyou Sag,it is determined that butt sealing and fault rock sealing are developed in slope area of Gaoyou Sag,and fault rock sealing is the main factor.The oil-water dissecting of oil-water related reservoirs has been carried out to determine whether the fault has the function of separating oil-water,and the data of oil-water interface and height of hydrocarbon column of each oil-water unit are calculated,which is based on this.A quantitative evaluation model for lateral sealing ability of faults in slope area of Gaoyou Sag was established by statistical analysis of the relationship between(SGR)content of fault zone and(AFPD)of overfault pressure difference.The critical SGR limit of lateral fault sealing in slope area of Gaoyou Sag is determined to be 29.8%,and the relationship between SGR and the height of hydrocarbon column which can be sealed by fault is determined: H=429.04ln(SGR)-1445.2.On the basis of the relationship between SGR and fault distance,the height-fault distance diagram of hydrocarbon column under different sand-soil ratios is obtained.Based on the evaluation model of lateral sealing ability of fault,the fault of controlling circle in slope area of Gaoyou Sag can be evaluated and the sealing ability of fault circle can be determined.Based on the evaluation model of lateral sealing property of faults,the differences between the height of laterally sealed hydrocarbon columns of faults with different sand-soil ratios under the same fault distance are analyzed through the lateral comparison of the inner and outer slopes in the slope area of Gaoyou Sag.Through the calculation of the fault sealing evaluation model in the study area,it is found that the height of the sealed hydrocarbon column is different for the faults with different sand-to-land ratios.In the slope area of Gaoyou Sag,the outer slopes are butt closed,and most of Funing formation is thick sandstone sandstones with very thin mudstone partition layer,and the partition layer has no oil-water separation effect,so they are uniform oil-water interface,and the sand-soil ratio is less than 30%.The inner slope not only contains butt sealing,but also fault rock seal,mainly fault rock seal,mostly sand-mud thin interlayer,part of mudstone partition thickness has the function of separating water,including multiple oil-water interface and reservoir unit,and the inner slope contains a lot of oil-water interface and reservoir unit,and the inner slope contains not only the butt seal,but also the fault rock seal.The sand-soil ratio is more than 30%.The comparison shows that the sand-soil ratio is less than 30%,the sand-soil ratio is 30%-40%,the sand-land ratio is 40%-50%,and the sand-land ratio is more than 50%.The comparison shows that the higher the ratio of sand to sand is,the higher the height of hydrocarbon column which can be sealed by fault is,that is,the easier to form seal and the stronger the sealing ability is under the same fault distance.On the contrary,the lower the sand-soil ratio is,the higher the height of hydrocarbon column which can be sealed by fault is,the less easy to form seal,and the weaker the sealing ability is.