Geological Modelling for 3-D Seismic Survey Design and Acquisition—A Case Study From Offshore Malaysia

Abstract

The ubiquitous presence of Miocene carbonate reefs offshore Malaysia has posed significant challenges to conventional seismic acquisition and imaging techniques. These carbonate platforms and pinnacle reefs have complex morphology and highly variable velocities, resulting in inadequate illumination of deeper stratigraphy due to low signal to noise ratio and complex wave propagation. Historical seismic interpretation of these features has considered that “all carbonates are the same”, resulting in errors in velocity analysis and imaging. This case study is based on a better geological understanding of the carbonates, and the intra-reef lithologies. The latter are highly carbonaceous shales and marls, with significantly lower velocities than the immediately adjacent true reefs. Understanding the geological differences allows for the creation of a detailed anisotropic 3D subsurface model of rock properties (typically acoustic P wave velocity and density), and then the synthetic propagation of waves through this model, to create synthetic seismic shot records. From this data, different survey designs were extracted and modelled using various azimuth combinations, and processed with current imaging algorithms to understand their relative benefits and to understand the relative benefits. This case study demonstrates the importance of the geology as input to 3D finite difference seismic modelling, and is an effective workflow in understanding the optimum acquisition design and processing options.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015