Comparative analysis of wellbore electrical heating, low-frequency heating, and steam injection for in-situ conversion in continental shale oil reservoirs

In-situ conversion represents a potential method for developing immature continental shale oil, with efficient heating technology serving as its key component. This study employs coupled thermo-hydraulic-chemical numerical simulation techniques to comprehensively compare the feasibility and efficiency of three methods-wellbore electrical heating, low-frequency electrical heating, and steam injection-during the in-situ conversion process from the perspectives of reservoir heating efficiency, kerogen and heavy oil decomposition, and oil/gas production. The comparison reveals that steam injection, due to the introduction of significant water content, exhibits the poorest heating performance, whereas low-frequency electrical heating demonstrates the most effective results in reservoir heating. When employing electrical heating, particularly low-frequency methods, higher proportions of kerogen and heavy oil decomposition lead to increased overall oil and gas production. Steam heating offers advantages in heavy oil accumulation and production as well as wellbore protection, yet it yields higher water production as a drawback. Through an integrated discussion across five dimensions-heating capacity, wellbore protection, kerogen decomposition, heavy oil decomposition, and fluid production-we find that low-frequency electrical heating performs the best overall. The insights and comparisons discussed in this paper are expected to guide the selection and optimization of heating strategies for in-situ conversion.