A two-layer model–based coupled simulation study of multi-cluster hydraulic fracture propagation and proppant transport in shale

Effective proppant placement in multi-cluster hydraulic fractures is crucial for shale gas fracturing; however, existing numerical methods face challenges in accurately coupling dynamic fracture propagation with suspended-load transport, bed erosion, and accumulation at the field scale. To address this, a coupled solution integrating the DDM with an improved TLM was developed. This solution incorporates a logarithmic near-bed velocity profile to refine bed shear stress calculations, thereby capturing dynamic flow allocation, fracture-tip extension, and proppant bed evolution within a unified framework. The key findings are: (1) Increasing spacing from 6 m to 25 m minimizes stress interference, reducing flow allocation disparities among clusters by 96%, thereby promoting more uniform fracture propagation and bed-load transport; (2) Higher rates elevate net pressure and reduce pressure drop differences across perforations but increase shear within fractures, exacerbating proppant placement disparities; (3) As viscosity increases from 3 mPa·s to 5 mPa·s, bed-load transport differences intensify, causing a sevenfold rise in placement discrepancies; at 10 mPa·s most proppants remain suspended, transitioning to a suspended-load transport regime and nearly eliminating inter-cluster distribution differences; (4) Larger proppants tend to accumulate near fracture inlets, which can help ensure more uniform inter-cluster distribution. In contrast, smaller proppants are more susceptible to flow variations, often resulting in uneven placement across clusters. (5) Additionally, under high proppant concentrations, proppant dunes reach equilibrium sooner, and creeping motion dominates particle transport, significantly reducing inter-cluster placement non-uniformity. The proposed coupled DDM–TLM model can reasonably predict proppant behavior in multi-cluster fractures and underpins the optimization of shale gas fracturing treatments.