Unconformity Trap Reservoir Prediction Based On Pre-stack Seismic Inversion

Unconformity trap reservoirs as an important type of complex reservoirs,has become an important exploration target for current oil reserve increasing.Compared with conventional structural reservoir,it has a greater concealment,and is also more difficult in seismic identifying and predicting.Jiyang Depression Chengdao regional unconformity developed multiple levels of stratigraphic traps,The study shows that the remaining potential stratigraphic reservoirs resources is rich,and the exploration is vast,with good prospects for exploration and development.This paper studies Chengdao pre-Tertiary unconformity trap reservoir,utilizes geological and geophysical data,combines rock physics,pre-stack seismic inversion,reservoir fluid identification and other areas method,carried out the related research work for unconformity stratigraphic trap reservoir prediction and fluid identification.For adjacent high-speed pre-Tertiary formations,reservoir has the same intensity reflection phase as the unconformity,resulting reservoir identification is difficult.We study a strong reflection seismic stratigraphic unconformity identification method by analyzing seismic data superimposed on the angle unconformity reflection characteristics,and a strong reflection characteristics matching pursuit extracted wavelet based spectral decomposition and then extract the unconformity strong ideological reflection characteristics recorded strong reflection finalized unconformity separating match.Model and the practical application of research show that the identification method highlight weak information which had been drowned in the reservoir strong reflection event out,and the reservoir identification accuracy is greatly improved,and also laid the foundation for fluid identification work.Conventional fluid factor based on rock elastic properties is affected seriously by porosity,Gassmann fluid items affected by the porosity has improvement,but based on the solid-liquid decoupling fluid factor can better identify the artifacts due to the elimination of fluid caused by the influence of porosity.Based on the two-phase medium theory to study the solid-liquid decoupled sensitive fluid factor build mode and contact with seismic reflection characteristics.We derived solid-liquid decoupled AVO and elastic impedance approximate equations containing the fluid equivalent bulk modulus,and used the elastic impedance inversion to realize extracting fluid equivalent bulk modulus,avoiding the indirect calculation of cumulative error.The actual application shows that in the situation of the purpose reservoir porosity in little change,Gassmann fluid term can be used as a fluid factor,but the clastic reservoirs with dramatic changes in porosity should adopt the fluid equivalent bulk modulus to fluid identification.