3D Gravity Modeling of Complex Salt Features in the Southern Gulf of Mexico

Mauricio Nava-Flores,Carlos Ortiz-Aleman,Alfredo Trujillo-Alcantara,Jaime Urrutia-Fucugauchi,Carlos Couder-Castañeda,Mauricio G Orozco-Del-Castillo,Alejandro Rodriguez-Castellanos

doi:10.1155/2016/1702164

Abstract

We present a three-dimensional (3D) gravity modeling and inversion approach and its application to complex geological settings characterized by several allochthonous salt bodies embedded in terrigenous sediments. Synthetic gravity data were computed for 3D forward modeling of salt bodies interpreted from Prestack Depth Migration (PSDM) seismic images. Density contrasts for the salt bodies surrounded by sedimentary units are derived from density-compaction curves for the northern Gulf of Mexico’s oil exploration surveys. By integrating results from different shape- and depth-source estimation algorithms, we built an initial model for the gravity anomaly inversion. We then applied a numerically optimized 3D simulated annealing gravity inversion method. The inverted 3D density model successfully retrieves the synthetic salt body ensemble. Results highlight the significance of integrating high-resolution potential field data for salt and subsalt imaging in oil exploration.

Highlights

Hydrocarbon exploration is largely based on geophysical methods among which seismic reflection is the most intensely employed
We present a three-dimensional (3D) gravity modeling and inversion approach and its application to complex geological settings characterized by several allochthonous salt bodies embedded in terrigenous sediments
The gravity anomaly grid generated by the 3D Inverted Model (3DInvM) shows that, despite the apparent differences in the central part of the grid corresponding to the gravity minimum, the amplitudes are similar to the observed gravity (Figure 12)

Summary

Introduction

Hydrocarbon exploration is largely based on geophysical methods among which seismic reflection is the most intensely employed. Physical property contrasts of salt features such as highly contrasting seismic velocities relative to the surrounding media lead to complex wave diffraction patterns and lack of illumination near and below them. In this context, gravity methods are well suited to support seismic prospection and improve subsalt imaging by taking full advantage of the density contrasts between salt bodies and surrounding sedimentary targets. The seismic wave high velocity contrasts at salt-sediment interface result in strong refractions and reflections, making it difficult to image the bottom and structures beneath salt bodies. Subsalt structural complexities present major barriers, requiring new approaches and integrative analyses of seismic and potential field data

Methods

Results

Conclusion