Interwell interference risk identification and fracturing-design optimization in stacked shale gas development: a case study of the 1H21 platform

Interwell interference is a major constraint on stacked shale gas development, as reduced well spacing and limited vertical separation may enhance hydraulic-fracture interaction. In this study, field pressure monitoring, tracer diagnosis, and three-dimensional hydraulic-fracture simulations were integrated to identify interference-prone fracturing stages on the 1H21 platform. A pressure increase greater than 3 MPa was defined as a strong pressure response, and tracer returns were treated as independent evidence of cross-well fluid migration. The simulations showed that cluster number, vertical stress contrast, fluid volume per stage, proppant intensity, horizontal stress contrast, and natural-fracture development jointly controlled fracture extension and risk-stage distribution. Unlike conventional spacing evaluations based mainly on predicted fracture half-length, the workflow combines stage-scale field evidence with geological and treatment controls to classify medium- and high-risk stages. The identified medium- and high-risk stages showed an 83.8% spatial matching rate with same-layer field pressure-response records. In the optimized simulation scenario, the number of high-risk stages decreased from 19 to 0, and the total number of medium- and high-risk stages decreased by 57.4%. The workflow supports field-constrained stage screening; however, its thresholds are platform-specific, and the simulated optimization requires field and production evaluation.