--> Predict Sandstone Distribution by Integrated Study of Mass Transported Deposit Using Borehole Image and Seismic Data: A Case Study From Northern Gulf of Mexico

AAPG ACE 2018

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Predict Sandstone Distribution by Integrated Study of Mass Transported Deposit Using Borehole Image and Seismic Data: A Case Study From Northern Gulf of Mexico

Abstract

Many Upper Tertiary reservoirs in the Gulf of Mexico (GoM) are sandstones deposited either in channel levee systems or lobe systems in the intra-slope deepwater environment. One of the major uncertainties about those reservoirs is their distribution, which is likely controlled by salt tectonics. The current salt structure, however, does not represent the salt structure when the sands were deposited. It is difficult, if not impossible, to restore the salt history based on current salt structures. It is well known that salt movement results in a great amount of mass transported deposits (MTDs) in GoM. The internal structure or texture of MTDs, therefore, may provide some information about the history of salt movement.

Borehole images on the other hand are widely used to characterize the internal structure or texture of MTDs; and the dips of MTDs from borehole images can be used to define the paleo slope, which controls the movement of MTDs and sand distribution.

In this integrated case study, all the available data, including borehole images, seismic volumes, and other petrophysical logs, were used to characterize the reservoir sands and MTDs. The MTDs and other lithofacies were defined based on textures from the borehole images and triaxial induction logs from two wells. Based on dips from borehole images, paleo flow directions of reservoir sands were defined. A relationship between lithofacies and relative acoustic impedance (RAI) volume was established; and the lithofacies defined on the wellbore was populated into 3d guided by the RAI volume. Geobodies of possible remnants of salt bodies were extracted from the seismic volume. The integrated results suggest that the location of salt remnants is likely the center of a paleo salt body. The evacuation of the salt body created a small basin for sand lobes to deposit. The dips from the MTDs provided information about the center of the small (or mini) basin, thus establishing a relationship between the dip pattern and sandstone distribution. If this relationship is valid for the other upper Tertiary MTDs in the GoM area, a new method can be developed which may enable us to predict the sandstone distribution using borehole images and provide guidance for petroleum exploration and field development in the future.