Abstract

The Mabee field is located in Andrews and Martin counties, Texas in the west-central portion of the Midland basin. Production from the San Andres dolomites has yielded over 95 MMBO by primary and secondary methods since the field discovery in 1943. A detailed geologic description of the reservoir was critical for the planning and operation of a tertiary CO₂ project. Texaco initiated a CO₂ flood in the southeast corner of the field in January of 1992.

Examination of over 5,000 feet of core established six major facies in an overall shallowing upward sequence. The top of the productive interval is identified by a thin shale unit, designated as the “B"marker. The uppermost (1)supratidal and (2)oncolite/pisolite facies are nonproductive due to occlusion of porosity by anhydrite. Production is from the dolomitized (3)subtidal and (4)ooid facies. The (5)sandstone facies is tightly cemented and acts as a barrier to fluid migration. The lowermost (6)open marine facies is below the oil/water contact. The reservoir was divided into three zones based on the facies and petrophysical characteristics. They define the vertical and lateral continuity of the reservoir across the field.

Determination of the depositional facies led to an increased understanding of reservoir performance. Three dimensional modeling of the reservoir has been useful as a tool for predicting the behavior of the CO₂ flood.