Velocity Model Building for the Low Relief Structure - Case Study in Tarim

A low relief structure refers to a type of relatively flat geologic body where the relief of the hydrocarbon trap is usually small, e.g., between 10 to 30 meters. Low relief structures are an important type of oil and gas reservoir in the Tarim Oilfield. Due to low relief, deep burial, lateral velocity change, and thickness variations of the overburden layers, accurate positioning of the structure in depth is very difficult by conventional prestack time or depth imaging. In this study area, however, there are many wells penetrated to the deep low relief structure. To fully utilize the well information for depth imaging, a new approach for building more accurate VTI model is used. We have used both Diving Wave Tomography (DWT) and Multi-Well Constrained Depth Imaging (MWCDI) technologies in our workflow. As the result, the miss-ties from our final depth image are less than 5m at well locations. The workflow with DWT and MWCDI can be applied to any land and shallow marine data. We will show how the DWT and MWCDI are applied with a case study.