Field Results of Miscible-Displacement Program Using Liquid Propane Driven by Gas, Parks Field Unit, Midland County, Texas

Abstract

Abstract A miscible-displacement program utilizing a propane slug driven by residue gas has been in operation in the Parks field unit approximately three years. A total of 1,540,000 bbl of liquid propane was injected into 23 wells between June, 1957, and July, 1958. During July, 1958, residue gas injection was begun at an injection rate of approximately 10 MMcf/D. Gas has been injected at this rate to the present time, and cumulative gas injection to July 1, 1960, has totaled 6,871 MMcf. It is concluded at this time that the project can be declared an engineering success since field results indicate an oil bank has been created by a gas-driven propane slug. It is further concluded that the project will be an economic success insofar as additional oil recovery over primary is concerned. However, the project has not been in operation a sufficient length of time to declare it an economic success in regard to oil recovery over that which it is believed could have been obtained by water injection. The answer to this question is yet to be determined. It is estimated that the ultimate recovery of the oil originally in place would have been 17 per cent by primary depletion, 41 per cent by water injection and will be 55 per cent by propane-gas-water injection. Introduction Miscible displacement is an oil-recovery process which is rapidly gaining popularity inasmuch as the process recovers 100 per cent of the oil in place in the swept volume. In comparison, straight gas injection normally recovers only 45 to 55 per cent, and water injection recovers 60 to 70 per cent of the oil originally in place in the swept area. The Parks field unit is an early field-wide example of the slug-type miscible-displacement process wherein a slug of fluid is injected into the reservoir which is miscible with both the reservoir and displacing fluids. In the Parks project, the slug was composed essentially of propane, and the displacing fluid is residue gas which is miscible with the propane at the existing reservoir conditions. Laboratory tests indicate extremely high recoveries from the swept reservoir volume by the miscible-slug process, but this is only a partial answer to the economic applicability of the process in an actual reservoir. The final answer can only be determined by field tests. The two main questions which must be answered through field testing are the following. How much volume will be swept? What minimum-size LPG slug can be utilized and still maintain miscibility throughout the process? Obtaining answers to these questions were two of the many objectives considered in arriving at the decision to install a field-wide miscible-slug process of such magnitude as the Parks project.