Simulation of Full-Area Propped Fracture Propagation and Productivity in Shale Gas Reservoirs

Low-viscosity slickwater is the dominant fracturing fluid for shale gas reservoir stimulation, characterized by superior capability in generating complex fracture networks yet inadequate proppant transport performance. This deficiency commonly leads to a limited propped fracture length and undesirable proppant placement profile. To address these challenges and enhance proppant placement quality as well as single-well gas productivity, a fully coupled numerical model integrating nonplanar 3D fracture propagation, proppant transport dynamics, and a black-oil model is developed using field geological and engineering parameters from actual horizontal wells. The impacts of key fracturing operation parameters on proppant transport behavior and well productivity are systematically investigated via numerical simulations. Results indicate that both proppant transport distance and gas production increase with rising injection rate, but the growth rate diminishes when the injection rate exceeds 16 m3/min. Similarly, increasing fracturing fluid viscosity improves proppant transport distance and gas production, while no further enhancement is observed once the viscosity surpasses 63 mPa·s. Smaller proppant particle size contributes to longer proppant transport distance but results in gradual degradation of well productivity. Under a constant total proppant volume, merely substituting a large fraction of small-sized proppants extends propped fracture length but fails to boost gas production. Optimally incorporating a moderate proportion of ultrafine proppants based on the original field scheme achieves superior proppant transport distance and productivity performance. Field tests validate that appropriately increasing fracturing fluid viscosity and ultrafine proppant dosage facilitates full-area proppant placement and contributes positively to gas production enhancement in shale gas reservoirs. The findings of this study provide significant guidance for optimizing injection rate design, fracturing fluid selection, and proppant type screening in shale gas hydraulic fracturing operations.