3-D SEISMIC SURVEY DESIGN VIA MODELING AND REVERSE TIME MIGRATION: PIERCE JUNCTION SALT DOME, TEXAS

Abstract

Seismic forward modeling studies are required for adequately imaging complex geological structures, such as folds, faults, and domes. Many U.S. Gulf Coast salt domes are used for oil and gas exploration, brine production, and underground hydrocarbon storage. For this reason, it is crucial to image the flank of the salt domes and surrounding sediments. Allied Geophysical Laboratories (AGL) carried out a 2-D seismic study in the Texas Brine Company facility to image the Pierce Junction salt dome. However, we were not able to image the salt flanks because of improper survey design. This led to the current study which proposes a 2-D and a 3-D seismic survey design using modeling and Reverse Time Migration (RTM) imaging. We gathered original 2-D seismic, topography, and gravity data to build 2-D and 3-D velocity models of the Pierce Junction salt dome area. We processed the original 2-D data and extracted the velocities of the cap rock and near surface sediments for use in velocity models. We modelled gravity data collected in a north-south direction and performed analyses on the synthetic seismic data to determine new 2-D conventional seismic survey parameters that could be achieved with the limited acquisition equipment of AGL. We modeled synthetic shot gathers by a finite difference method using the full (two-way) acoustic wave equation, and generated seismic images using the Reverse Time Migration (RTM) method. We determined the optimum parameters of the new 2-D seismic survey by reviewing the quality of the results. These parameters were able to adequately image the salt dome and its surrounding sediments. We then modified the 2-D parameters for a new 3-D survey, and obtained synthetic RTM images based on the 3-D velocity model. Optimal 2-D and 3-D seismic survey designs for the Pierce Junction salt dome area were achieved using seismic modeling and RTM imaging. We found RTM imaging to be a novel and powerful method for determining seismic survey parameters for complex geological structures.