A New Approach to Imaging and Pore Pressure Analysis in Depth Domain in Complex Geologic Areas: Use of Rock Physics Constrained Velocity Modeling and Reverse-Time Migration
An Earth model solely based on tomography is non-unique. To manage the inherent non-uniqueness, we have developed a new workflow that constrains the tomography using geology in conjunction with thermal history modeling and rock physics principles. The resulting constrained model is then input to Reverse-Time Migration (RTM) for further migration. This workflow is termed Rock Physics Guided Velocity Modeling for Migration and Pore Pressure (Dutta et al. 2014). 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 it to its “physically plausible ranges”, such as for example, that these be within the “hydrostatic” and fracture pressure” limits. The process works well without any well control. To facilitate the implementation of this workflow, we also introduced 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 that is a part of the current workflow for velocity modeling. Anisotropy parameters are then estimated using the rock physics template as well. We have evaluated the process 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 found that the new approach also improved the image quality significantly. We will present several case studies to illustrate how the technology works in complex areas such as subsalt pore pressure analysis. In addition, we can also incorporate the current model to Full Waveform Inversion (FWI) technology. We shall present results to show how the process works using Revolution II, dual - coil (all azimuth and large offset) seismic data.
AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015