Migration and Distribution Laws of Proppants in Complex Lithology Reservoirs in Offshore Areas

Fracture conductivity is a key factor to determine the fracturing effect. Optimizing proppant particle size distribution is critical for ensuring efficient proppant placement within fractures. To address challenges associated with the low-permeability reservoirs in the Lufeng Oilfield of the South China Sea—including high heterogeneity, complex lithology, and suboptimal fracturing outcomes—JRC (Joint Roughness Coefficient) was employed to quantitatively characterize the lithological properties of the target formation. A CFD-DEM (Computational Fluid Dynamics-Discrete Element Method) two-way coupling approach was then utilized to construct a fracture channel model that simulates proppant transport dynamics. The proppant particle size under different lithology was optimized. The results show that: (1) In rough fractures, proppant particles exhibit more chaotic migration behavior compared to their movement on smooth surfaces, thereby increasing the risk of fracture plugging; (2) Within the same particle size range, for proppants with mesh sizes of 40/70 or 20/40, fracture conductivity decreases as roughness increases. In contrast, for 30/50 mesh proppants, conductivity initially increases and then decreases with rising roughness; (3) Under identical roughness conditions, the following recommendations apply based on fracture conductivity behavior relative to proppant particle size: When JRC < 46, conductivity increases with larger particle sizes, with 20/40 mesh proppant recommended; When JRC > 46, conductivity decreases as particle size increases; 40/70 mesh proppant is thus recommended to maintain effective conductivity; At JRC = 46, conductivity first increases then decreases with increasing particle size, making 30/50 mesh the optimal choice. The research findings provide a theoretical foundation for optimizing fracturing designs and enhancing fracturing performance in the field.