In-situ recovery of heavy-oil from fractured carbonate reservoirs: Optimization of steam-over-solvent injection method

• A hybrid optimization was applied for steam/solvent injection in fractured reservoirs.
• This framework ensures better solution space coverage and less computation.
• It also enables testing multiple scenarios with few optimization experiments.
• Huff-and-puff is more economical than continuous solvent injection.

In this paper, a hybrid global optimization framework is used to optimize the design of a new process called Steam-Over-Solvent in Fractured Reservoirs (SOS-FR) proposed by Al-Bahlani and Babadagli (2008. Heavy-oil recovery in naturally fractured reservoirs with varying wettability by steam solvent co-injection. In: Paper 117626 Presented at SPE International Thermal Operations and Heavy Oil Symposium, Calgary, Canada, 20–23 October. doi:10.2118/117626-MS), Al-Bahlani and Babadagli (2009a. Steam-over-solvent injection in fractured reservoirs (SOS-FR) for heavy-oil recovery: experimental analysis of the mechanism. In: Paper 123568 Presented at SPE Asia Pacific Oil and Gas Conference & Exhibition, Jakarta, Indonesia, 4–6 August. doi: 10.2118/123568-MS), Al-Bahlani and Babadagli (2009b. Laboratory and field scale analysis of steam-over-solvent injection in fractured reservoirs (SOS-FR) for heavy-oil recovery. In: Paper 124047 Presented at SPE Annual Technical Conference and Exhibition, New Orleans, Louisiana, 4–7 October. doi: 10.2118/124047-MS), Al-Bahlani and Babadagli (2011a. J. Petrol. Sci. Eng. 78 (2): 338–346), Al-Bahlani and Babadagli (2011b. Energy Fuels 25: 4528–4539). The hybrid framework integrates genetic algorithm with orthogonal arrays and response surface proxies for better convergence behavior and higher computational efficiency. The SOS-FR technique consists of a heating phase using steam injection, subsequent solvent injection, and low temperature steam injection for solvent retrieval and additional oil recovery. Solvent injection can be continuous or cyclic where the solvent is injected, soaked, and then fluids are produced. This paper studies both scenarios over single and multiple matrix field scaled reservoirs by adjusting the injections’ durations and rates. As a result, about 30 design elements for four base benchmark models are optimized, and the profit and efficiency is doubled comparing with the benchmark models using optimal injection scheme suggested by our optimization framework.