Optimizing Shut-In Time Using Saturation Rebalancing Mechanism in Unconventional Reservoir

Abstract Unconventional reservoirs require hydraulic fracturing for commercial production, making it essential for productivity enhancement. Non-uniform fracture propagation alters subsurface density, inducing measurable surface gravity responses. Microgravity technology monitors these density changes to infer fluid dynamics and fracture geometry. Precise gravity anomaly separation is critical for resolving reservoir density variations. Depth continuation was optimized to isolate reliable residual anomalies (e.g., Well MD-2-5D). This study implements real-time microgravity fracturing monitoring and establishes a shut-in time optimization method based on coalbed methane imbibition principles to accelerate gas breakthrough. Post-frac shut-in enables gas-water substitution between matrix and fractures: insufficient shut-in causes delayed production, while excessive shut-in dissipates near-well energy, shortening natural flow periods and reducing rates. Optimized shut-in balances these effects, accelerating breakthrough while extending natural flow and increasing production. Field validation in Midong's coalbed methane confirms this method enhances stimulation effectiveness.