Framework Model Building in Highly Complex Structures Utilizing Multi-Azimuth 3D Seismic Data: Case History from Bahrain Field

Abstract

Abstract The workflow discussed in this paper shows the process of building a complex fault framework using wide-azimuth seismic and abundant well data. 3D fault interpretation using azimuthal seismic volumes allows for subtle fault detection and better fault definition. Using special workflows which "snap" seismic faults to the well fault cuts, we illustrate how to build, and quickly update a very complex structure framework with a high level of accuracy. The Bahrain field is a salt-cored, elongated and almost N-S anticline, with multiple oil and gas reservoirs in formations of Paleozoic, Jurassic, and Cretaceous age. Structural deformation has been nearly continuous from Triassic to early Tertiary, with a complex growth and deformation history (Samahiji and Chaube, SPE 1987), resulting in a highly-faulted structure with compartmentalized and fractured reservoirs. Therefore, building an adequate structure framework model is critical for the new development of this field, where over 250 wells per year are being drilled in various reservoirs. The existing 3D seismic survey in Awali field was acquired in 1998. Though it was intended and initially processed as a narrow azimuth volume, it has been recently reprocessed in wide azimuth mode using new and advanced processing technology (Maili et al, EAGE-Copenhagen, 2012). This advanced processing was made possible by the particular acquisition geometry (cross spread with 8 receiver lines live), allowing for wide azimuth data in the upper part of section where many of the key oil producing reservoirs are located. This new approach to structure framework building using automated workflows described here allows rapid framework updates to be made with data from newly drilled wells, and makes it possible to shorten the cycle time for geologic model building and maintain an "evergreen" model. This up-to-date structure framework also plays a key role in operations for planning new wells and drilling following-up.