Optimizing Gas-Lift Systems

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the 49th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Texas, Oct. 6–9, 1974. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract The most profitable distribution of gas to wells in a continuous flow gas-lift system can be determined by an analytical procedure. The procedure utilizes well procedure. The procedure utilizes well test information and calculations of vertical two-phase flow behavior to predict individual well producing rate responses to changes in gas input rate. The optimum distribution of the available gas can be calculated based on each well's contribution to the profit for the system. A computer program was developed to perform the calculations for the procedure. This program has been used in a Venezuela field program has been used in a Venezuela field with 1500 gas-lift wells. A modified version of the program has been used in a Texas field containing 150 gas-lift wells. Introduction For the past several years Exxon Production Research Company (EPRCo) has Production Research Company (EPRCo) has assisted their affiliate in Venezuela, Creole Petroleum Corporation, in improving their gas-lift system efficiency. One of the results of this work has been the development of a calculation technique for determining the optimum distribution of gas to gas-lift wells. The determination of the optimum gas distribution has particular significance to Creole because of their need to use a large portion of the existing compressor facilities to inject produced gas in subsurface reservoirs. As the allocation of available gas for pressure maintenance projects increases, less gas is available projects increases, less gas is available for gas-lifting oil wells. To maintain oil production at desirable levels, Creole must make optimum use of available gas on those wells which will supply the most oil consistent with good reservoir engineering practices. Creole also has other incentives for determining the optimum gas distribution in a gas-lift system. First, there is a need to properly reallocate gas when a compressor station is down for regular maintenance or due to equipment failure. Second, bottlenecks in the gas-oil treating facilities may unnecessarily limit highly productive wells which require only small amounts of gas-lift gas. Therefore, Creole recognized they could improve their daily operations by minimizing the amount of gas required to maintain gas-lifted oil production.