3D-VSP and Surface Full-azimuth Seismic Integrated Study in Daqing Oil Field

Abstract

Abstract Along with the progress of VSP techniques, especially the improvement of downhole geophone manufacture and VSP data processing methods, now the survey mode has developed from zero offset VSP, offset VSP to Walkaway-VSP, Walkaround-VSP and 3D-VSP corresponding to different geological objectives. VSP techniques have obtained partial success in parameter estimation, high precision imaging and reservoir characterization, but obtained dataset is range limited and imaging still need to be improved. In order to broaden the range of survey and expand the advantages of VSP to surface seismic, large array 3D-VSP and full-azimuth surface seismic survey were carry out in XJWZ area of Daqing oil field. The reservoir of this area is mainly formed by volcanic and its distribution is very complex due to many periods of volcanic overlap in this area. Previous seismic surveys are mainly 2D and narrow azimuth 3D, the results still cannot be used for anisotropy analysis and fracture discrimination effectively, say nothing of satisfying the requirements of developing plan establishing. So a joint survey of 3D-VSP and full-azimuth surface seismic was implemented. This project tries to combine the advantages of VSP and surface seismic, measuring in borehole and surface simultaneously. Thus, real three-dimensional survey was achieved. Some comprehensive studies are presented in this paper, these research work include: 3D-VSP and full-azimuth surface seismic simultaneous survey design; Q factor and anisotropy parameter estimated from VSP and applied to 3D seismic processing; characterize reservoir and predict gas saturation with final images. The interpreted results have been used for well drilling and wet gas has been founded, so the validity of this method has been proved. Introduction The work area studied here is located in northeast part of China. Objective is a gas-bearing volcanic reservoir. The formation and distribution of volcanic reservoir in this area is extremely complicated (Figure 1). It is shown in early-stage study that the YC Formation in this area is characterized as a very complicated vertically superimposed structure due to numerous volcanic eruptions (Figure 2). Volcanic rock holds a sensitive spatial variation in its lithofacies. In the past, only the 2D and the narrow-azimuth 3D surface seismic surveys were carried out in this area, which have a certain limitation in identifying the anisotropy of volcanic rocks and the fracture zones, and therefore can not meet the requirements on working out the development program for the oil field at latter stage.