Extensive analysis of single ceramic proppant fracture mechanism and the influence of realistic extreme reservoir conditions on proppant mechanical performance

Abstract

Proppants, the main component in reservoir stimulation projects, are used to keep fractures open and allow the efficient extraction of oil/gas. Although natural sand was very often used as a proppant in past decades, ceramic proppants have gained attention due to their lower crush resistance. This study reports a coupled numerical and experimental approach to the comprehensive analysis of the ceramic proppant fracture mechanism and the influence of realistic reservoir/fracture fluid (dry, deionized (DI) water, brine, and oil) environments on its mechanical performance. Ceramic proppants simulated using discrete element modelling (DEM) were calibrated and validated using laboratory-scale coupled CT-scan one-dimensional single-pellet compression tests. The CT-scanning performed on a single proppant subjected to increasing loading stages detected the transition of existing proppant internal pores to micro-fractures, which ultimately led to the failure of the proppant. Furthermore, single proppant fracture initiation, propagation and coalescence processes are discussed with the assistance of DEM simulations. In addition, exposure to different reservoir/fracture fluids revealed substantial proppant strength degradation, causing early proppant failure at lower stress. The coupled process of mineral leaching and pore-induced micro-cracking is identified as a key parameter in the reduction of ceramic proppant strength. Furthermore, the existence of pores/flaws within the proppant microstructure results in the possibility of stress-intensified corrosion, leading to early proppant crushing.