Methods for Delineation of Fractured Oil Bearing Conglomerate Reservoir

摘要

A few conglomerate oil bearing reservoirs were discovered atrnthe northwest end of Langgu sub-depression, a local lacustrinernsub-depression of the famous North China’s Bohaiwan Basin.rnAmong them, Tong 43 block is complicated in pore spaces,rnaccording to core analysis and FMI log pictures, both matrixrnpores and fractures occurred in this reservoir. 5 wells havernbeen drilled so far. The oil productivity and the degree ofrnfracturing of the reservoir of each well are of great variation.rnTherefore, the nature of fractures and their distribution mustrnbe clearly understood prior to production drilling program.rnTwo types of analysis have been applied in this study: 1)rngeologic analysis on genetic conditions of fractures, includingrnstudies of structural features, sedimentary facies andrndeformation of faulting; 2) seismic techniques, to discover thernrelationship between fractures and anomaly of seismicrnattributes, and azimuthal seismic anisotropy, thus outlining therndistribution of fractures based on seismic data processing.rnThrough this study, three sets of fracture detecting techniquesrnhave been effectively established: 1) techniques based onrngenetic analysis; 2) techniques based on seismic attributesrnanalysis, where analysis on discrepancy between different postrnstack attributes has been applied; and 3) pre-stack seismicrntechniques based on amplitude and frequency analysis on 3Drnseismic volume processed with varied azimuthal gathers. Inrnthis analysis, azimuthal seismic anisotropy analysis on P wavernseismic data played an important part in fracture interpretationrnabout orientation and intensity. The results of the fracturerndetection of each technique were reevaluated by comparingrnwith well data and geologic conditions. The properties of oilrnbearing Tong 43 conglomerate bodies were evaluated inrngreater detail afterwards, and rich oil bearing zones werernlocated. This study not only provides guidance for productionrndrilling program of Tong 43 block, but can be a reference forrnsimilar reservoir delineation as well.