Perdido Reimaging: Overview of Model Building and Imaging Challenges and Solutions

Abstract

Summary

We present an overview of challenges and solutions for Perdido reimaging, a depth-imaging project located over the southern Perdido Fold Belt, Salina del Bravo province, subsalt belt and adjacent inboard and outboard areas, in the western Gulf of Mexico. Geology within this 40,000 sq. km area comprises not only complex allochthonous salt and subsalt structures but also pervasive, complex shale, both in a setting that has undergone multiple compressional regimes. Given these geological challenges for imaging, a multidiscipline approach is proposed to provide solutions for earth model building to improve image quality for regional subsurface mapping as well as for hydrocarbon exploration. Key geophysical techniques include broadband deghosting, utilization of gravity measurements and modeling for salt interpretation, integrating borehole information, multi-azimuth tomography, as well as both refraction and reflection full-waveform inversion.

Applications

The same geological aspects that make hydrocarbon exploration in this region conceivable also pose significant challenges for velocity modeling and imaging. Our workflow leverages both well-established methods and more recent technologies. Early and consisent usage of stratigraphic mapping and petro-physical analysis is key to guiding and validating model updates in complex compressional zones that exhibit large spatial and depth variability in velocity. In combination, tomography and full-waveform inversion can provide robust bulk model updates over a regional setting, shallow to deep, even starting from a simple 1D function. Gravity information proved not only useful for assessing interpretation error in the massive, amalgamated canopies of the Salina del Bravo, but also for discerning other potential errors in the larger earth model, such as the thick shale, elevated Mesozoic strata, and autochthonous salt presence.

Conclusions

We employed a multi-measurement workflow for this region through which allowed us to resolve a more accurate earth model. The workflow includes a multifaceted approach to the velocity update for shale, salt & subsalt. We demonstrate that with this strategy, significant image uplift can be achieved through Kirchhoff depth and reverse time migrations over legacy volumes.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018