Research On Faults Sealing In Western Gaoyou Depression Of Subei Basin

Gaoyou depression was a half graben depression formed by differentialuplifting subsidence movement of fault blocks. The faults in the western Gaoyoudepression widely developed and the hydrocarbon enrichment is very high. The complexgeology conditions and the variegated reservoir types related to faults made the faultsealing research very important.Through palaeogrowth index and activity velocity, the activity laws of ten differentgrades of faults were researched. The conclusions showed that faults of different gradshad different activity strength. Faults of grad two had two strong active stages, inaccordance with Wubao and Zhenwu stage; however, faults of grade three and four hadonly one active stage, in accordance with Zhenwu stage.By physical simulation, the formation process of growth fault was studied and itshowed that, there were muddy sedimentary layers in faulted zone. Muddy sedimentarylayer was a kind of muddy layer developed when the fault generated. It was divided intothree kinds, namely adhereing type, fracture type and broken type. The differences oftype were influenced by mud thickness, depth and fault displace and so on. Differenttypes had different impact on vertical sealing.The lateral and vertical sealing and its influence over the pool forming wererespectively researched through SSF, lithologic contraposition and the mud content in thefaulted zone, the pressure on the fault plane and so on. The conclusions gained by SSFshowed that, the critical value of SSF was 1.8, and was decreasing from formationFuning to Sanduo, thus, the sealing was from poor to good, which was favorable forhydrocarbon migration and accumulation. The conclusion gained from the muddy matrixin the faulted zone showed that, the matrix in formation Sanduo and Dainan was mostlymud, so the vertical sealing was good.The configuration of the active stage of faults and the poor forming stage was perfect. From the time when hydrocarbon migrated in a large scale to now, the activityintensity of most part of faults was fading and it was favorable for the reservation of theoil accumulated. The transport patterns in different area were distinct. In huangjue area,vertical transport was more important, while lateral in weizhuang area and steppedpattern in majiazui area..