Study on proppants transportation and fracture damage in shale millimeter-scale rough fractures

TANG Wei; ZHAI Cheng; LIU Ting; XU Jizhao; WANG Yu; YU Xu; SUN Yong; CONG Yuzhou; ZHENG Yangfeng; CHEN Aikun; XU Hexiang; LAI Yongshuai; PI Chengjian

doi:10.13247/j.cnki.jcumt.20250165

Abstract：Millimeter-scale fractures in the hydraulic fracture network of shale reservoirs are impor-tant pathways for shale gas seepage.It is of great significance to investigate the characteristics of proppant migration and settlement in these millimeter-scale fractures and the supporting perfor-mance of proppants after settlement.Based on the coupled methods of computational fluid dynamics(CFD)with discrete element method(DEM),and finite difference method(FDM)with DEM,a numerical research approach was proposed to comprehensively explore proppant migration in frac-tures and their supporting effect on fractures after settlement.First,the geometric model of the frac-ture surface for split shale was obtained through laser scanning,and a CFD-DEM model for the proppants transport carried by fracturing fluid within millimeter-aperture fracture was established.The transport characteristics of proppants under different parameters were analyzed and the settle-ment distribution of proppants was obtained.Then,a shale model with millimeter-aperture fracture was established,and the proppants obtained in CFD-DEM simulation were imported into the frac-ture of the shale model.The evolution of fracture aperture under stress,the stress-bearing character-istics of proppants,and the damage law of fracture surfaces were investigated.The research results indicate that smaller proppant particle size,higher fracturing fluid flow rate,and higher fracturing fluid viscosity are more conducive to proppant migration.When mixed proppants with different par-ticle sizes are used,the settlement of large-sized proppants hinders the migration of small-sized prop-pants,thereby forming settlement zones.The proportion of proppants that mainly bear stress is small,and they are mainly distributed in areas where the fracture surfaces have large inclination.There is no obvious correlation between the compression amount of fracture aperture and the prop-pant coverage rate on fracture surfaces,but it is significantly affected by stress magnitude and prop-pant size.Under the action of stress,stress concentration occurs around proppants,leading to ten-sile and shear damage to fracture surfaces.Tensile failure is the main damage form of fracture sur-faces,and the damage volume increases with the increase of proppant particle size.