Performance History of the Midland Farms, North (Grayburg) Field

The Midland Farms, North (Grayburg) field, located in Andrews County, Tex., was discovered in July, 1953. The crude was highly undersaturated at the original reservoir pressure, with a saturation pressure of only 132 psia. Consequently, early in its producing life, this field was determined to be producing by rock and fluid expansion. A low primary recovery of only 10 per cent of original oil in place and low producing rates during the major portion of the producing life were predicted. Unitization and secondary recovery studies were commenced 1 1/2 years after discovery. A peripheral water flood utilizing injection wells located at or near the oil-water contact was determined to be the optimum secondary recovery method. It was estimated that ultimate recovery under peripheral water flooding would be 27 per cent of original oil in place. The Midland Farms, North (Grayburg) field was unitized in Sept., 1956, and water injection was commenced shortly thereafter. Performance under water injection has been highly satisfactory, and no significant operating problems have developed. Average reservoir pressure has been increased approximately 300 psi. A number of wells have experienced considerable increases in producing capacity. Several limited-capacity wells have been restored to top-allowable producing rates. Uniform entry of induced edge water and bottom water into the oil pay apparently has occurred. An adequate amount of reservoir engineering data enabled recognition of the producing mechanism of the field early in its life and aided in designing a secondary recovery program. Cooperation of operators in the field resulted in early unitization and initiation of peripheral water flooding. This project is one of the first water floods to be conducted in a West Texas carbonate reservoir. Early ideas and predictions of poor performance in carbonate reservoirs are indicated to be incorrect by data from the Midland Farms, North (Grayburg) field. General The Midland Farms, North (Grayburg) field is located in southeast Andrews County, Tex., approximately 10 miles south of the city of Andrews and on the extreme western edge of the Midland basin. It is located in an area containing several large, prolific Grayburg fields (as shown on Fig. 1). The Grayburg pay, from which the subject field produces, is the shallowest producing horizon in this multi-pay area. The Midland Farms, North (Grayburg) field was discovered in July, 1953, with the completion of Pan American Petroleum Corp. (formerly Stanolind Oil and Gas Co.) Midland Farms AE No. 1 (now Midland Farms, North Grayburg Unit Well No. 13). Initial pumping potential of the discovery well was 158 BOPD and 8 BWPD. The entire productive area includes 1,970 acres. A total of 44 wells was drilled within the unit boundary, resulting in 40 completions and four dry holes. Development was made in an orderly fashion on 40-acre spacing. Cumulative oil production to the date of unitization, Sept. l, 1956, totaled approximately 1.5 million bbl. Cumulative production to Jan. 1, 1961, was approximately 3.6 million bbl. Structure Fig. 2 is a structure map of the field contoured on top of the Grayburg porosity. The structure is a north-south trending anticline with approximately 100 ft of closure. Maximum dip is 200 ft/mile in an easterly direction. JPT P. 857^