Effect of Fault Condensed Belts on Oil Migration and Accumulation in Combination of Upper Source Rocks and Lower Reservoirs——An Example of Fuyu,Yangdachengzi Oil Layer in Sanzhao Depression of Songliao Basin

To understand the effect of fault condensed belts on oil migration and accumulation of F,Y oil layer in Sanzhao depression,the development and genesis of fault condensed belts were studied by using seismic interpretation results.The development of a number of T2 faults was discovered in F,Y oil layer of Sanzhao depression.These T2 faults were distributed in 35 fault condensed belts in horizontal plane.They were formed by the control action of basement action,regulation with oblique extension and distribution of volcanic mouth.By anatomy of oil reservoirs and study of space match relation between oil reservoirs and accumulation conditions,it was discovered that oil accumulation model of F,Y oil layer in Sanzhao depression was that the oil from K1q1nsource rock migrated down to F,Y oil layer through boundary faults of fault condensed belts under the action of overpressure and migrated laterally to two sides of fault condensed belts under the action of buoyancy,at last,accumulating in fault blocks or fault-lithology traps on horst structure architecture.By the study of space match relation between fault condensed belts and oil distribution,four control actions of fault condensed belts were discovered in oil migration and accumulation of F,Y oil layer:①Two sides of fault condensed belts were favorable areas for oil to accumulate;②The nearer is the F,Y oil layer from bottom of K1q1 n source rock the more abundant is the oil accumulation in vicinity of fault condensed belts;③Horst structures of two sides of fault condensed belts were favorable places for oil to accumulate;④The nearer distance from boundary faults of fault condensed belts,the higher productivity of oil well is.