Publications

An Earth model solely based on tomography is non-unique – especially, in the presence of anisotropy or complex geology, such as highly folded overthrust zone, where tomography velocity inversion becomes highly non-linear.This is often the case with sub-salt or sub-basalt, where incidence angles are small. To manage the inherent non-uniqueness, we constrain the tomography using geologic information in conjunction with thermal history modelling and rock physics principles. The resulting constrained model is then input to Reverse Time Migration (RTM) for imaging. This workflow is termed Rock Physics Guided Velocity Modelling for Migration and Pore Pressure (Dutta et al. 2011). A novel feature of this technology is to use predicted pore pressure as a guide to improve the quality of the Earth Model. Thus, we produce a velocity model that not only flattens the CIP gathers but also limits the velocity field to its physically and geologically plausible ranges. To facilitate the implementation of this workflow, we also introduce a new technique based on this concept to quality control the velocity model. This is called “pore pressure scan” technology. It is similar to conventional velocity scan approach, but it works directly in the pore pressure domain using a rock physics template. The results of this new method have been evaluated on several blind wells and it shows a significantly improved pore pressure estimation over that obtained by the conventional tomography based approach. In addition, we find that the new approach also improves the image quality. We present case studies from both Indonesia and the USA to illustrate how the technology works.