Pre-stack Inversion And Reservoir Prediction In A Structure Of Xihu Sag

Xihu sag was located in the northeast of the East China Sea shelf basin, it is the main target area of oil and gas exploration in the East China Sea Shelf Basin. Reservoir in this area belong to the delta plain and delta front channel sand underwater distributary channel and mouth bar, the main target fault development, reservoir complex distribution. The distribution of P-wave impedance value of Hydrocarbon formations of sandstone was overlapping with the mudstone and the dry layer, using conventional impedance inversion method is difficult to effectively identify favorable reservoir. For this kind of geological conditions, we need to increase the shear wave information, utilization of P-wave and shear wave information to predict favorable reservoir.In this paper, we use pre-stack time migrated seismic data as the basis, for the fine evaluation of exploratory wells for the bridge, analysis reservoir and well logging, geophysical response characteristics; to solve the current exploration and geology problem of structure of Huagang formation in Xihu sag as the goal. Focus on exploration ideas and methods of of joint inversion of P-wave and S-wave Huagang formation reservoir, analyse the relationship between the district reservoir characteristics and geophysical parameters, using reasonable parameters for reservoir inversion to predict sandstone reservoirs development regularity. Using reservoir physical parameters response, reservoir development situation, structural features to predict oil and gas development area in plane.In this paper we preprocessed the well data and seismic data from the A structure of Xihu sag, corrected DT, density curve distortion caused by the hole diameter collapsed. To determine the sensitive reservoir parameters of the study area, making the P-wave impedance and S-wave impedance, and Vp/Vs, Poisson’s ratio, density, coefficient Lame elastic parameters of the cross-plot and histogram to finalize the dividing line. Finally we determined Vp/Vs is sensitive to sandstone and Lame coefficient multiplying density is sensitive to fluid in the study area. The dividing line to identify sand or shale is that Vp/Vs of sandstone is less than 1.75, the dividing line to identify fluid is that Lam? elastic parameter of effective reservoir is less than 3.2*107. We have finished fine horizon and fault interpretation of 12 small layer of Huagang in the study area, making synthetic seismogram establish stratigraphic framework and low frequency geological model, on this basis, the use of Rocktrace module of Jason software for three main targets H5, H8, H11 prestack sparse pulse inversion. Obtained Vp/Vs, P-impedence, S-impedence, density data volume. To make top and bottom layer sand body interpretation of three main purpose horizon. Composing the top boundry of sandstone structure map interface, extract sandstone thickness, the effective reservoir thickness and layer attribute. The direction of channel sandstone of the 3 main purpose layers was northeast-southwest or north-south, the reservoir is mainly distributed in the central and northern of the work area. Get three target layer plane distribution of effective reservoir, porosity and P-impedance by a negative correlation to predict porosity. Combining structure, porosity, reservoir carved out a comprehensive analysis of the distribution of four favorable areas, mainly in the main high focus of the middle part and the second high focus of the southwest of the study area, which provide the basis for the next oil and gas exploration area.