The East Vacuum Grayburg/San Andres Unit (EVGSAU), operated by Phillips Petroleum Company, is the site selected for a comprehensive evaluation of the use of foam for improving the effectiveness of a CO2 flood. The four-year project is jointly funded by the EVGSAU Working Interest Owners (WIO), the U.S. Department of Energy (DOE), and the State of New Mexico. The Petroleum Recovery Research Center (PRRC), a division of the New Mexico Institute of Mining and Technology (NMIMT), is providing laboratory and research support for the project. A Joint Project Advisory Team (JPAT) composed of technical representatives from numerous major oil companies provides input, review, and guidance for the project.
The EVGSAU, located about 15 miles northwest of Hobbs in Lea County, is the site of the first full-scale miscible carbon dioxide injection project in the state of New Mexico. The 5000-acre CO2 project is divided into three water-alternating-gas (WAG) areas where CO2 injection was initiated in September of 1985. A 2:1 WAG ratio was chosen so that while CO2 is injected into one area, water is injected into the other two areas of approximately equal pore volumes. After each fourth month of operation, CO2 injection is rotated into another WAG area.
While tertiary oil response at the EVGSAU is very favorable, some wells are showing excessive CO2 breakthrough, thereby increasing CO2 recycling and compression costs. This project includes a field demonstration of the use of foam to reduce the mobility of the injected CO2, reduce excessive CO2 production, improve the volumetric sweep efficiency of the injected CO2, and increase the incremental oil recovery from the tertiary project. Thus, a suitable pattern in the EVGSAU was selected, based on the criterion that the production there be typical of other patterns without a distinctly better- or worse record of CO2 breakthrough than in the rest of the field. An observation well was drilled in the pattern; location of this well is approximately 150 ft from the pattern injection well. The observation well was cored and logged to improve reservoir characterization in the pattern area, as well as to provide reservoir cores for laboratory tests with suitable foam-generating surfactants. In- order to use the borehole as a logging monitor well, the bottom 800 ft was cased with fiberglass.
The objective of this four-year project is to conduct reservoir studies, laboratory tests, simulation runs, and field tests to evaluate the use of foam for mobility control- or fluid diversion in a CO2 flood. A geological characterization of the pilot area and surrounding patterns has been assembled for the history matching and reservoir simulation studies that are in progress. The foam-flood mechanistic model developed at the PRRC is being incorporated into the field-scale reservoir simulator.
This paper summarizes the project plans, the baseline field testing, and the laboratory test results that pertain to surfactant selection. This overview provides a background for subsequent papers that will report on various aspects of the project.