Velocity model and time-depth conversion for the northwestern South China Sea deepwater areas

摘要

There are rich natural gas resources in the northwestern South China Sea deepwater areas, with poor degree of exploration. Because of the unique tectonic, sedimentary background of the region, velocity model building and time-depth conversion have been an important and difficult problem for a long time. Recent researches in this direction have revealed three major problems for deepwater areas, i.e., the way to determine error correction for drilling velocity, the optimization of velocity modeling, and the understanding and analysis of velocity variations in the slope areas. The present contribution proposes technical solutions to the problems:(1) velocity correction version can be established by analyzing the geology, reservoir, water depths and velocity spectrum characteristics;(2) a unified method can be adopted to analyze the velocity variation patterns in drilled pale structural positions;and (3) across-layer velocity is analyzed to establish the velocity model individually for each of the layers. Such a solution is applicable, as shown in an example from the northwestern South China Sea deepwater areas, in which an improved prediction precision is obtained.