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

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.