Research And Application Of Reservoir Controlling Fault Sealing In The South Of Jinhu Depression

Jinhu Depression,which is one of the major gas and oil gathering areas of Subei basin,is located in the west of Dongtai Hollow.The fault system in the south of the depression is extremely complex,and the fault is vital important to the formation of oil and gas reservoir.Fault-nose and fault-block oil reservoirs account for most of the existed reservoirs.So,searching structural reservoir is still the most important in exploring small fault block reservoirUnder the guidance of sedimentology,structural geology and petroleum geology,combining with seismic data,core date and well-logging date,the structural characteristic,the sedimentary characteristics and the fault sealing are analyzed.The faults are interpreted subtly by 3D seismic interpretation and divided into four levels,among which level three are the most.The complanate fault complex includes parallel-aligned,skew-type,pinniform,echelon,horsetail;in profile,the fault complex mainly includes “Y” font,graben and horst,step fault.On the base of correlation of strata,stratum thickness maps and sand thickness maps are drawn to analyze the distribution of the reservoir;combining with core date,the sedimentary facies are confirmed: the sedimentary facies of E1f2 are the shore shallow lake;the sedimentary facies of E1f3 are front of delta;the upper part of E1f4 are front of delta,the lower part are lacustrine facies.Combining with the distribution of sandstone and mudstone,we can analyze the source-reservoir-caprock association: the mudstones of E1f2 and E1f4 are well source rocks and regional cap rocks;the sandstones of E1f2 and E1f4 have priority to form oil and gas reservoir because of their position.The mudstones of E1f3 are local cap rocks.Through lithologic contraposition,SGR and so on,we can study the lateral fault sealing;through the mud content in the faulted zone,DT,the pressure on the fault plane,we can study the vertical fault sealing.The results are as follows: Chajian' lateral fault sealing is well,the vertical fault sealing of E1f4 is also well,by contrast,the vertical fault sealing of E1f3 and E1f2 is worse than that of E1f4;Tongcheng's lateral fault sealing is well enough to form oil and gas reservoir.Through study the distribution of oil and gas reservoirs,we find that oil and gas mainly gather together in the fan-shaped fault block.If there are good reservoir in fan-shaped fault blocks,it is likely to form oil and gas reservoir.So,combined with the distribution of sedimentary facies,we can predict favorable oil and gas reservoir by select fan-shaped fault blocks with good permeability.