Post‐Stimulation Hydraulic Response and Productivity Constraints of a Low‐Productivity Carbonate Geothermal Well in the Small Intramontane Basin, Beijing Piedmont, North China

ABSTRACT The Houcheng Basin, a small intramontane basin in the Beijing piedmont, North China, hosts Mesoproterozoic Jixianian dolomite geothermal reservoirs. Unlike adjacent rift basins such as the Jizhong Depression, which develop high‐quality carbonate reservoirs under favorable preservation conditions, the Houcheng Basin represents a tectonically constrained setting where sustainable geothermal exploitation remains challenging. This study investigates Well 960 in the Houcheng Basin by integrating stimulation records, variable‐frequency pumping–recovery tests, a homogeneous axisymmetric radial‐flow finite‐element model, and core and thin‐section observations to evaluate post‐stimulation productivity limitations. Increasing pump frequency from 30 to 37 Hz increased steady discharge by only 24%, whereas steady drawdown increased by 179% and specific capacity decreased by 56%. The maximum tested discharge was 15.26 m 3 /h, still below the project‐level target of 40 m 3 /h. A homogeneous radial‐flow reference model constrained by the 30‐Hz stage reproduced the overall response at the lowest pumping intensity, but the observed end‐stage drawdowns at 33 and 37 Hz exceeded the upper bounds of the reference‐model ensemble by 29.82 and 51.65 m, respectively. Observed water‐level recovery after pumping was also faster than predicted by the reference model. These responses indicate increasing excess head loss at higher pumping intensities that cannot be adequately represented by a single, constant equivalent transmissivity. Core and thin‐section observations show that some fractures are partly filled with carbonate cements and solid bitumen, indicating that geometric fracture development does not necessarily correspond to hydraulic effectiveness. The Well 960 case indicates that post‐completion stimulation may not fully offset productivity risks associated with inadequate identification of hydraulically effective reservoir intervals. For comparable small intramontane basins in North China, geothermal development should place greater emphasis on pre‐drilling assessment of reservoir effectiveness and use post‐drilling dynamic hydraulic responses to refine estimates of development potential.