Field Experiments in Spacing of Steam Soak Wells

Abstract

This paper was prepared for the Improved Oil Recovery Symposium of the Society of Petroleum Engineers of AIME, to be held in Tulsa, Okla., April 22–24, 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 requested 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. Introduction By mid-1972 Atlantic Richfield Co.'s leases in the Midway Sunset field, Kern County, Calif., were thought to be adequately developed. Most of the leases had begun to decline and some were approaching uneconomic status. In late 1972, an engineering effort was made to determine the feasibility of infill drilling that followed an earlier stake's survey. The effort involved a conceptual analysis of the parameters that influence steam-soak stimulation, which is widely used in the heavy, viscous oil production of the leases. The results obtained supported an experimental infill drilling program in selected leases, consisting of multiwell packages to test adequately the premise that packages to test adequately the premise that additional economic reserves could be found in some of these old, developed reservoirs. During the last two months of 1972 and the first half of 1973, Atlantic Richfield Co. drilled 23 new wells in three leases, which represented the 10 percent of all the wells drilled in the Midway Sunset field during that time. These wells were drilled using an optimized-package approach designed to reduce over-all costs per well and to obtain valid statistical data. The encouraging results obtained from the drilling program and the recent crude oil price increases program and the recent crude oil price increases have prompted additional drilling during the fourth quarter of 1973, when 12 more wells were drilled. Future plans for 1974 include an additional drilling program. The fact that, during 1972 and 1973, Midway Sunset field reached its peak of production and had the greatest number of wells drilled, may be an indication that other operators are reaching the same conclusions as those set forth here. Background Kuo et al. in 1970 published the results of a model of the steam-soak process based on the production performance of a reservoir in which gravity drainage was the dominant production mechanism. Their model assumed that the production mechanism. Their model assumed that the steam zone temperature was constant and that the heated area was gradually enlarged by conduction. Kuo's results were reported in comparison to earlier work done by Seba and Perry. These two papers, as well as earlier ones by Towson and papers, as well as earlier ones by Towson and Boberg and by Clossman, Ratliff and Truitt, were concerned with predicting oil production rates from stimulation with steam. Their work offers valuable insight into the steam-soak process, as does the work of other process, as does the work of other authors. The work of Kuo et al. sought to combine a temperature distribution with a model of the fluid flow, but excluded consideration of individual steam-soak cycles. The work of Clossman et al. predicted first-cycle performance of stratified reservoirs where performance of stratified reservoirs where crossflow from adjoining strata increased the flow of oil.