Early Performance Review of a Successful Pressure Maintenance Project in a Deep Louisiana Reservoir

Abstract

Abstract The Broussard oil sand unit, operated by Tidewater Oil Co, is located in the Erath field, Vermilion Parish, La. The unit was formed as a reservoir-wide pressure maintenance project utilizing salt water injection below 12,500 ft. Formation of a reservoir-wide unit was accomplished and pressure maintenance operations were initiated in April, 1961. Actual performance of the project during the more than three years of operation has been very close to predicted performance. Reservoir productive capacity is in excess of the unit allowable of 1,764 BOPD. Performance of the project to date indicates that ultimate recovery from the reservoir will reach or exceed the predicted value of 7.4 million STB oil. Introduction The Broussard oil sand unit is located in the Erath field of Vermilion Parish, La. (Fig. 1). The Broussard sand was proven productive with the completion of the Tidewater Oil Co. H. H. Broussard Well No. 1 (B-4) in Jan., 1957. Development of the reservoir was completed in 1959, with 13 oil completions producing 1,538 B/D from an average depth of 12,440 ft sub-sea. In addition to the 13 producing wells, four dry holes were drilled before the reservoir limits were completely defined. Pressure-production performance of the reservoir indicated the reservoir energy mechanism is solution-gas drive with a weak water drive. Reservoir engineering studies indicated that the natural reservoir energy would recover only 31 per cent of the estimated 12.8 million STB oil initially in place. Secondary recovery feasibility studies indicated that pressure maintenance by water injection could greatly increase the ultimate recovery from the reservoir. The reservoir was unitized on a 100 per cent acre-foot basis, effective April 1, 1961. On that date, Tidewater Oil Co. became operator of the first reservoir-wide unit to be formed under Louisiana Department of Conservation Act 441, Act 441 provides for forced pooling of a reservoir to prevent mineral waste if 75 per cent of both the royalty interest owners and the working interest owners approve the unitization. Sixteen days after unitization was effective, pressure maintenance operations were initiated by down-dip water injection in one well. Additional development has expanded the injection pattern to five wells, all of which are injecting water below a depth of 12,500 ft sub-sea. The pressure maintenance project has been in operation for over three years. During this time over 1.9 million bbl of oil have been produced and 3.1 million bbl of water have been injected. This paper is a review of the operation of the project during the three years since unitization with a comparison of predicted pressure maintenance performance vs the actual performance. Geological and Reservoir Data The Broussard oil sand unit is one of Louisiana's and the petroleum industry's deepest water injection projects in an oil reservoir. The reservoir is located on a monocline from a depth range of 12,200 to 12,600 ft sub-sea (Fig. 2). JPT P. 1357^