Abstract

The Grayburg reservoir of the Foster - South Cowden Field has been producing since 1938, and under waterflood since 1962. Production had declined to near abandonment level at the start of this project. The initial approach of this study was to construct a flow model with conventional data. Logs and cores provided the basis for a geological model. Production data was assembled and validated along with the few measured pressures taken early in the field’s history. Production testing of all wells was initiated with new equipment to provide accurate current production data. Pressure transient testing of all wells was initiated to provide accurate current pressures. History matching of pressure and water-cut data validated the flow model, and the flow model has since guided field operation, subject to the limits imposed by the spacing of the well data (one reliable well log per 32 acres of reservoir). At this scale, compartmentalization and heterogeneity of the reservoir is obvious, and the use of 3-D seismic is required to define porosity in the area between wells.

The 3-D seismic data set was reprocessed to retain high frequencies, thereby improving vertical resolution to the range of 50 ft. Seismic bin size is 110 by 110 ft. Traces from the seismic inversion model exhibit a high degree of correlation to the well log data. A correlation was developed between seismic velocities and porosity for each geologic zone. The correlation was used to develop porosity maps for each zone in the flow model. The resulting flow model was validated through the history matching process, and used to guide the redevelopment of the waterflood.