A Sensitivity Analysis of Cyclic Solvent Stimulation for Post-CHOPS EOR: Application on an Actual Field Case

Abstract

Summary An uncertainty-screening procedure was performed to assess the feasibility of cyclic solvent stimulation as a post-cold heavy-oil production with sands (CHOPS) enhanced-oil-recovery (EOR) method. To achieve this, three cycles of cyclic solvent stimulation were modeled on a previously history-matched Albertan CHOPS field with 15 wells. The results were compared with a base model at each cycle in terms of oil production, gas production, and gas-injection volumes. The emphasis was on both uncertain parameters (wormhole vertical location, strength of foamy oil, time-dependent gas dissolution/exsolution) and operational input (injection pattern, injection rate, injection/soaking time). It was shown that bottom-located wormholes and nonequilibrium gas dissolution/exsolution could highly affect incremental oil production and project net present values (NPVs), but unfortunately, they cannot be controlled in practice. On the other hand, injection pattern, injection rate, and injection/soaking time, as operational inputs, can contribute to project profitability. Next, an economic model was developed, and after-tax NPV of the field was introduced as an economic indicator. This uncertainty analysis revealed that an increase in operational input such as injection rate may enhance oil recovery from a technical point of view, but does not necessarily increase project profitability (NPVs), yet an optimum value exists. It was shown that such an economic model had the priority to oil-recovery factor or cumulative oil production because it could incorporate costs and sales simultaneously by performing continuous discounting, and allow the asset holder to maximize NPVs by selecting the best development strategy.