CFD-DEM simulation of proppant transport under variable injection strategies in rough fracture network with supercritical CO2

Abstract

Supercritical CO₂ fracturing is a reservoir stimulation technology with broad application prospects, and the effective placement of proppant in the rough fracture network produced by fracturing is the key to determining the stimulation effect of the operating wells. In this study, an experimentally validated computational fluid dynamics-discrete element method (CFD-DEM) model is used to simulate supercritical CO₂ transport proppant in a rough fracture network. The results show that in rough fracture networks, the use of small-sized proppant (0.2 mm) or low-density proppant (1250 kg/m³) significantly increases the amount of proppant within branching fractures, as well as the transport distance. Combination injection gives better proppant dune placement compared to single type of proppant injection, where the pumping schedule of larger and then smaller proppant sizes is effective in increasing propping of branching fracture. The efficacy of pulse injection in enhancing proppant transport distance using supercritical CO₂ is significantly constrained by the absence of suitable fiber materials.