Miscible Drive Field Applications in the Seminole City Pool

Abstract

Introduction This paper discusses a field test of a gas-driven liquid propane process being conducted by The Carter Oil Co. and supplements previously published information on the project. It presents a brief history of the still incomplete project and includes an evaluation of the method, based on present knowledge. The process consists of injecting a predetermined volume of propane into a reservoir at a pressure above the vapor pressure of propane and driving the propane and oil to the production wells by means of an immiscible-phase gas drive. The test was carried out in the C–2 Block leases (Seminole, Okla.) in the Booch sand. The sand is about 3,600 ft deep, averages 30-md permeability and 18 per cent porosity, and ranges in thickness in the test area from 12 to 30 ft. Connate water is estimated at 35 per cent. The field was depleted by primary means for about 20 years and at the time the test started was producing 15 B/D at a gas-oil ratio of 7,500 scf/bbl. History of Test The reservoir was repressured with gas and 143,000 bbl of liquid propane were injected into two gas injection wells after which a gas drive of the propane was started. Since then total oil production has amounted to 142,000 bbl from five production wells. Approximately 12,000 bbl of this production is attributed to water injection which was used to create a barrier to hydrocarbon migration on the north end of the test area. Breakthrough of injected propane into the production wells occurred almost immediately after the start of the test, contrary to laboratory experiments with linear, homogeneous models. About 73,000 bbl of propane have been produced for an over-all oil-propane ratio of 1.95. Approximately 600,000 Mcf of gas have been injected. Because the field test is not only unconfined but also consists of incomplete well patterns, estimates have been made that only about 76,000 bbl of propane went into the test pattern and that approximately 40,000 bbl more oil would have been produced had the test been confined. This would yield a "recovery" of 2.2 bbl of oil per bbl of propane injected.