INCREASING OIL RECOVERY THROUGH ADVANCED REPROCESSING OF 3D SEISMIC, GRANT CANYON AND BACON FLAT FIELDS, NYE COUNTY, NEVADA

Makoil, Inc., of Orange, California, with the support of the U.S. Department of Energy has reprocessed and reinterpreted the 3D seismic survey of the Grant Canyon area, Railroad Valley, Nye County, Nevada. The project was supported by Dept. of Energy Grant DE-FG26-00BC15257. The Grant Canyon survey covers an area of 11 square miles, and includes Grant Canyon and Bacon Flat oil fields. These fields have produced over 20 million barrels of oil since 1981, from debris slides of Devonian rocks that are beneath 3,500 to 5,000 ft of Tertiary syntectonic deposits that fill the basin of Railroad Valley. High-angle and low-angle normal faults complicate the trap geometry of the fields, and there is great variability in the acoustic characteristics of the overlying valley fill. These factors combine to create an area that is challenging to interpret from seismic reflection data. A 3D seismic survey acquired in 1992-93 by the operator of the fields has been used to identify development and wildcat locations with mixed success. Makoil believed that improved techniques of processing seismic data and additional well control could enhance the interpretation enough to improve the chances of success in the survey area. The project involved the acquisition of hardware and software for survey interpretation, survey reprocessing, and reinterpretation of the survey. SeisX, published by Paradigm Geophysical Ltd., was chosen as the interpretation software, and it was installed on a Dell Precision 610 computer work station with the Windows NT operating system. The hardware and software were selected based on cost, possible addition of compatible modeling software in the future, and the experience of consulting geophysicists in the Billings area. Installation of the software and integration of the hardware into the local office network was difficult at times but was accomplished with some technical support from Paradigm and Hewlett Packard, manufacturer of some of the network equipment. A number of improvements in the processing of the survey were made compared to the original work. Pre-stack migration was employed, and some errors in muting in the original processing were found and corrected. In addition, improvements in computer hardware allowed interactive monitoring of the processing steps, so that parameters could be adjusted before completion of each step. The reprocessed survey was then loaded into SeisX, v. 3.5, for interpretation work. Interpretation was done on 2, 21-inch monitors connected to the work station. SeisX was prone to crashing, but little work was lost because of this. The program was developed for use under the Unix operating system, and some aspects of the design of the user interface betray that heritage. For example, printing is a 2-stage operation that involves creation of a graphic file using SeisX and printing the file with printer utility software. Because of problems inherent in using graphics files with different software, a significant amount of trial and error is introduced in getting printed output. Most of the interpretation work was done using vertical profiles. The interpretation tools used with time slices are limited and hard to use, but a number to tools and techniques are available to use with vertical profiles. Although this project encountered a number of delays and difficulties, some unavoidable and some self-inflicted, the result is an improved 3D survey and greater confidence in the interpretation. The experiences described in this report will be useful to those that are embarking on a 3D seismic interpretation project.

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