Study On Reservoir Forming Characteristics And Indentification Of Stratigraphic Overlapped Oil Reservoir Of Upper Dainan Formation In Northern Slope Of Gaoyou Sag

Through the method of geological comprehensive research and seismic techniques to identify the development model and characteristics of stratum,sedimentary pattern and distribution rule of sand body,structural characteristics of unconformity and the petroleum migration laws of Daiyi member.Seismic technology is used to establish the seismic overlap recognition model.Combined with the result of structural interpretation to describe the stratum overlap wire accurately and predict the plan distribution of sand body for determining boundary and thickness of sand body.Finally,structural characteristics of T₃⁰ are used to determine trap by“five-line".That is,through implementation of lithologic pinch-out line,stratum overlap line,stratum erosion line,structural line of sand body top surface and sand body thickness contour line to find favorable overlap trap position.Four main achievements are as follows:1 Through the principle of sequence stratigraphy and high-resolution sequence stratigraphy,based on the deposition cycle division,dividing and comparing the stratum by marking layer of logging and seismic reflection characteristics,to establish stratigraphic development model of study area.2 Analyzed the sedimentary system by geologic comprehensive method to establish the sedimentary types and patterns of sand body.3 Based on analyzing the accumulation condition of stratigraphic trap,which clear that the stratigraphic overlap reservoir type is stratigraphic overlap traps or tectonics and stratigraphic overlap traps.Using comprehensive seismic techniques to establish the seismic overlap recognition pattern,describe the stratum overlap lines accurately,predict the plan distribution of sand body and find a favorable overlap trap position.4 The characteristics of the reservoir are lower-generation and upper-storage pattern by comprehensive analysis.the influence of petroleum migration and transportation system on accumulation are determined.The structural characteristics of the unconformity determine that petroleum accumulation model in Gaoyou sag is controlled by faults,sand-fault and sand-fault-unconformity.The fault as petroleum transportation system is the main controlling factor of petroleum accumulation in this area,and the transmission efficiency is dominated by low transmission efficiency model.The accumulation model in this area is mainly reservoir with fault.