Background A well group acts as a multi-well synergistic unit, and its configuration directly determines both the selection of optimal injection–production process and the utilization efficiency of stratigraphic conditions, ultimately affecting the overall performance of resource recovery.

Methods Using numerical simulations, this study assessed the performance of autothermic pyrolysis in situ conversion (ATS) under three vertical well group configurations: one injection well and one production well (1I1P), one injection well surrounded by four production wells (1I4P), and one injection well surrounded by six production wells (1I6P). Furthermore, it revealed the synergistic mechanisms between well group configuration and energy efficiency.

Results and Conclusions  Considering drilling costs, ATS under the 1I4P configuration showed the highest comprehensive efficiency. During the thermal excitation phase of ATS, a gas injection rate of 400 m³/h for preheating exhibited optimal energy efficiency under consistent temperature of preheating gas and duration. During the autothermic reaction control stage, a gas injection rate of less than 200 m³/h failed to initiate the autothermic pyrolysis reaction, while an excessive rate exceeding 1000 m³/h interrupted the reaction process. Within the effective injection rate range, a gas injection rate of 400 m³/h yielded the optimal energy return ratio. The comparison of the performance of the 1I4P well pattern under varying well spacing values reveals that 25-meter spacing between the injection and production wells yielded high comprehensive energy efficiency. In this case, strata with a low oil content of 4% can be effectively developed using ATS, yielding an ideal energy ratio. Through joint optimization of well spacing and gas injection parameters, the development of field-scale oil shale through ATS yielded a peak energy return ratio of 8.85 after 3.7 years and a cumulative oil production of 10519.5 t over four years. Moreover, ATS exhibited high economic viability in terms of average operating cost per barrel while contributing to the preservation of a considerable amount of available residual heat. The findings of this study provide support for the industrial application of the in situ conversion of oil shale by offering both a theoretical basis for well group configuration design and an economic assessment framework.