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Planning a CO2 Tertiary Recovery Project, Means San Andres Unit

C. J. George, L. H. Stiles

In evaluating and planning a CO2 project in the Means San Andres unit, Andrews County, Texas, close coordination between geology and reservoir engineering was important to the project's success.

Additional recovery from the 6,700-ac CO2 project area is expected to be 38 million bbl of oil, a combination of tertiary from CO2 injection and primary and secondary from infill drilling. The project included drilling 380 wells, which reduced the spacing to 10 ac and provided a large amount of new data for improved reservoir description and engineering analysis.

The Means field is geologically located on the northeastern edge of the Central Basin platform and produces from dolomite in the Grayburg and San Andres Formations between 4,200 and 4,800 ft deep. The field was discovered in 1934 and was initially developed on 40-ac spacing. In 1963, the field was unitized and water injection began. Large-scale infill drilling with pattern modification occurred during the 1970s and 1980s. The CO2 tertiary project began in 1983.

The reservoir description work consisted of a paleoenvironmental study based on detailed core description, volumetric original-oil-in-place determination, and a study of reservoir continuity for determining additional oil recovery with closer well spacing. Additional evaluation included laboratory testing, reservoir simulation, and a field pilot that successfully remobilized waterflood residual oil.

AAPG Search and Discovery Article #91037©1987 AAPG Southwest Section, Dallas, Texas, March 22-24, 1987.