The Research Of Sedimentary Facies And Reservoir Prediction Of The Eocene In Eastern Area Of The Deep Depression In Gaoyou Depression

The Gaoyou Depression is the major oil exploration in Jiangsu oil field. According to the exploration level of upper and middle formations are high in Gaoyou depression, the next exploration direction are refined. The reservoir of the oil-bearing formation in the upper petroleum system (Dainan formation, Sanduo formation) are more faults, large depth of burial, poor physical property and thin monolayer thickness, so the output of generally conventional test oil is lower. Therefore, to research the sedimentary system and distribution regular of advantage sand body, and then to study the reservoir characteristics and research the distribution of advantage reservoir, it can provide geological basis for the next phase of oil and gas exploration.First, grounding on stratigraphy of equence stratigraphy and theory of sedimentlogy, choosing traditionally formation divided method, selecting the typical section in the area, the E2d1 section of Gaoyou depression are divided into three sand bed groups; the E2d2 section of Gaoyou depression are divided into five sand bed groups; the E2s1 section of Gaoyou depression are divided into seven sand bed groups; and on the based then the formation framework of the research area is established.The study of sedimentary environment of Dainan and Sanduo formation of Gaoyou depression is carried out through rock observation, log response, sizing analysis and the predecessors'research based on formation framework built. And the study makes clear that they are most developed Nearshore Subaqueous Fans during sediment of E2d1 section; they are most developed Fan-delta during sediment of E2d2 section and early period of E2s1 section; they are mainly developed Fluvial Facies since middle period of E2s1 section. The sedimentary facies here can be further divided into six subfacies which are composed of middle of Nearshore Subaqueous Fans, Nearshore Subaqueous Fans front, Fan-delta plain, Fan-delta front, the former fan-delta and braided river subfacies, and these subfacies include ten microfacies which are composed of sub-distributary channel, sub-distributary bay, front in the fan, clay objects in fan-side, braided distributary channel, sublacustrine fan, channel bar, interchannel area, river flank and peripheral and braided river. Through analyzing the evolvement of sedimentary in every layer, it is found that the lake area is gradually shrinking, fan body size increases from E2d section to early period of E2s1; the lake receded and a fluvial sedimentary strata from middle period of E2s1 to late period of E2s1. It shows that sand body show progradation deposition.Though the study of micro-features of reservoir, we can see that it is middle porosity and low permeability reservoirs. With the constraints of the geological conditions, combinning the well datas and seismic datas, we can predict the distribution of reservoir by the method of wave impedance inversion. We can classify the reservoirs into 4 categories combining sedimentary facies, lithologic characteristic, diagenesis, pore structure and physical properties of reservoir, of whichâ… andâ…¡is good reservoirs,â…¢andâ…£is bad reservoirs. Based on reservoir evaluation, we predicted six horizons of favorable reservoir distribute, they are E2d11,E2d12,E2d23,E2d25,E2s16 and E2s17.