Comparison of Conventional Cyclic Steaming and Steamflooding in a Massive, Dipping, Midway Sunset Field Reservoir

Abstract

SPE Members Abstract Two thermally enhanced oil recovery methods, cyclic steaming and steamflooding, have been investigated by means of numerical modeling for a massive, dipping, Midway Sunset Field reservoir. Comparative economics have been evaluated for the development alternatives. The results of the investigation indicate that ultimate recovery efficiency is not sensitive to the method of steam delivery to the reservoir. Cyclic steaming methods recovered the same percentage of original oil in place as did steamflooding. The cyclic operations required several times longer than steamflooding to reach the same ultimate recovery efficiency. On a steam utilization efficiency basis (oil to steam ratio), cyclic steaming with small steam slug volumes proved to be the most efficient recovery method. As the rate of steam injection increased, the steam utilization efficiency decreased, regardless of the manner in which steam was delivered to the reservoir. Despite having the poorest steam utilization efficiency, steamflooding provided far superior economics as compared to conventional low or moderate slug volume cyclic steaming. This is directly attributable to steamflooding having the fastest rate of increase in average reservoir temperature and therefore the greatest rate of net recovery as compared to the alternatives investigated. Steamflooding exhibited a much quicker payout of development capital and a greater present value return per dollar invested. Introduction While thermally enhanced oil recovery methods are an attractive method of extracting heavy oil, due to the large development capital costs and the significant expense in steam generation, it is important to look critically at development alternatives and to choose the method that is most attractive to the investor. A cyclic steaming project is operated significantly different from that of a steamflood. Consequently, it requires a different facilities configuration in order to allow effective optimization during its operation. It is costly to install a facilities design tailored to one method, and then to retrofit for an alternative operating strategy. It is therefore essential to choose the more attractive manner in which steam is to be delivered to the reservoir and to install and operate the project in this manner. Thermal EOR textbooks indicate that, in general, greater recovery efficiencies are possible with steamflooding than with cyclic steaming. It is generally written that while steamflooding can be expected to recover 50–60% of the original oil in place, cyclic steaming typically recovers only 10–25%. Cyclic steaming is viewed as a stimulation method with rapid response while there is a lag in the production response associated with steamflooding. The Potter Sand in the Midway Sunset Field has been developed and operated with cyclic steaming as well as a steamflood by various operators. Both methods are viewed by their respective operators as technical and economic successes. P. 429^

Enhanced Oil Recovery: An Update Review

“…The Midway Sunset Field [258] represents another example of an onshore turbiditic deposit in California (Bakersfield area). The traditional scheme again is a form of steamflooding (or stimulation).…”