The Research Of Variable Velocity Structure Mapping Methods In X Area Of Biyang Depression

Because of the complicated structure and large lateral variations of layer velocity in Biyang depression, the variable velocity mapping is used in study area in order to improve the accuracy of structural mapping.Based on the high-precision3D seismic data of120km2and drilling data of40wells in study area, velocity field analysis, variable velocity mapping and structural trap identification are used in H31to H37sand groups. According to the geological characteristics of study area, the method of establishing the velocity field is combined with well and seismic. The velocity field of study area can be gotten by combining time depth relationship which is interpolated under the control of TO layer with velocity spectrum and corrected through log data. Three aspects achievements are got:1. As the influence of formation change on velocity is considered in the method, the structure depth is coincided with layer data of well point after time-depth conversion. From the3D display of velocity field and average velocity plan, the velocity changes reasonably in horizontality and verticality, the velocity of well point and the single well are matched well and the velocity changing accord with the geology rule.2. The velocity field is used by variable velocity structure mapping in H31to H37sand groups, the accuracy is greatly improved compared with the Dix formula structure mapping. Errors are in the scope of regulation and satisfy the needs of exploration and development in the study area;3.The typical traps are identified and analyzed through structure maps of H31to H37sand groups in the study area. Trap types are mainly structural traps. Trap formation is influenced by faulting and the main traps are fault nose and block traps. Five new traps are identified in the study area and the oil-bearing analysis is mainly test on the no.4and the no.5fault nose traps. There are good oil and gas display and it has great value to exploiting in H35and H37sand groups through the analysis of trap elements, shale content inversion and hydrocarbon indicator. The reliability of the method of variable velocity structure mapping which combined with well and seismic is further proved.