New Integrated Workflows for Improved Pore Pressure Prediction and Seismic Imaging

Abstract

As petroleum exploration has gravitated towards deep, poorly imaged often sub-salt reservoirs, it has become critical to develop new approaches that can be used to improve quality of seismic image and pre-drill pressure predictions. Seismic imaging usually is based on tomography to derive a velocity model. For difficult area, such as subsalt where tomography cannot be used reliably, subsalt velocity scan or HBI (horizon based interpolation) become very useful. This presentation introduces new geologically constrained pressure and velocity workflows that integrate basin modeling, tomography, geomechanics, and petrophysics. They honor stratigraphy, depositional environment and account for the evolution of rock properties due to burial or changing pressure / temperature conditions, diagenesis, etc. Our workflows consist of several steps that include basin modeling, tomography, petrophysical and geomechanical data analysis and integration, building hybrid velocity models, and pre-stack depth migration. The process of basin model building and subsequent depth imaging starts in the shallow section, where the image is typically better and iteratively propagates downwards. After each iteration a hybrid velocity model is built using velocities from tomography and velocities from basin modeling. Here are two examples of hybrid model building: (1) When the measure of gather flatness for common image gathers satisfies a predefined threshold error level, the velocity values for the region in the tomography velocity model are used; when the measure of gather flatness does not satisfy the predefined threshold error level, the velocity values for the region in the tomography velocity model are replaced with the corresponding velocity values for the region in the basin modeling derived velocity model. The hybrid model is then smoothed before being used in pre-stack depth migration (2) Use of velocities from tomography in the shallow hydrostatic pore pressure section and velocities from basin modeling in the abnormal pore pressure (below hydrostatic) section, where tomography typically looses fidelity. Selected case studies indicate that in addition to improved pre-drill pressure predictions new workflows result in improved image and ability to interpret deep subsalt section.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015