An Optimized-Hybrid In-Situ-Upgrading and Steam-Injection Process for Enhanced-Heavy-Oil Recovery in a Naturally Fractured Reservoir

Abstract

Summary The subsurface hybridization of the in-situ-upgrading process (IUP) and steam injection (i.e., the hybrid-IUP/steam recovery scheme) integrates the advantages of process robustness and bitumen upgrading of the IUP with the relatively low capital-expenditure (CapEx) requirement and faster subsurface heat delivery of steam-injection-driven heating. The hybrid-IUP/steam scheme significantly reduces CapEx compared with the IUP recovery scheme, and increases robustness and reliability compared with the solely steam-injection-driven recovery processes because it is less sensitive to variability in geology and reservoir properties. We first demonstrate the advantages of the hybrid-IUP/steam recovery scheme using a mechanistic model for a real-life heavy-oil reservoir. An integrated surface/subsurface-economic evaluation using simplified economic indicators shows that the hybrid scheme has attractive attributes. Then, we further mature the hybrid scheme in terms of increasing its robustness with respect to subsurface uncertainties through a multirealization robust optimization workflow. By use of this workflow, pattern designs that are less prone to subsurface uncertainties have been developed, thereby improving the robustness of main subsurface-economic-performance indicators. Two promising design families and example designs stemming from these families have been identified that exceed standalone-IUP performance in terms of subsurface-recovery-performance indicators in a statistical sense. In this context, cumulative-probability distribution functions (CDFs) of main pattern-performance indicators have been computed using realistic dual-permeability/dual-porosity (DP/DP) mechanistic subsurface models by rigorously taking into account the effects of major subsurface uncertainties with a design-of-experiments (DOE) and Monte Carlo sampling-driven uncertainty-quantification workflow applied after robust optimization. The key conclusions of this study are the following: Hydrocarbon recovery from the upper section of the reservoir (formation above the heaters) is critical for driving the benefits of the hybrid scheme beyond standalone-IUP performance. The presence of a reasonable level of vertical fracture connectivity between steam-injection and electrically heated formations plays a significant role in the improved performance over the standalone-IUP recovery scheme. Shifting the steam injection to the same formation with the heaters results in suboptimal pattern performance for the investigated design families. Effective lateral heating with steam is important for the economic performance of the hybrid scheme. Fracture-architecture-related heterogeneities [namely, bed-bounded and bed-crossing (mesofractures)] play a significant role in lateral heating with steam (supported by electrical heaters). The optimal operation strategy features relatively early and high-rate steam injection as well as using 12 to 14 heaters, two producers, and one steam injector per a 92- to 110-m-wide pattern. Ceasing steam injection upon a significant amount of live-steam breakthrough at the producer is required during the main steam-heating period for optimal recovery performance. Injectivity plays an important role for the hybrid-pattern performance. A realistic enhanced-injectivity scenario noticeably improves pattern performance.