Numerical Study of the Proppant Transportation in the Nonplanar Fracture

Abstract

ABSTRACT: The sand-carrying fluid flow in complex hydraulic fracture is crucial to improve the fracture conductivity. Previous research on proppant transportation simulation has mainly focused on planar fracture. This paper presents a proppant transportation model of the nonplanar fracture. Based on the computational fluid dynamics (CFD) and discrete element method (DEM), a 3D coupled model was established to simulate the transportation of proppant in the nonplanar fracture. Proppant distribution is quantitatively evaluated by the height and length as the proppant bed reaches the equilibrium state. The numerical model also investigated the effects of proppant density, proppant size and fluid velocity on the proppant transportation. The results show that the sand-carrying fluid flow in nonplanar fracture has higher flow resistance compared with the planar fracture. Proppant with large size may reduce the usage amount but tend to form sand plugging. Further analysis reveals that as the proppant density decreases, the average height of the proppant bed also increases and the distribution distance is much longer. The results in this paper can help design the parameters of proppant and fracturing fluid, which can make the nonplanar fracture maintain a high and enduring conductivity. 1. INTRODUCTION In recent years, hydraulic fracturing technology has often been required to perform reservoir stimulation when extracting unconventional oil and gas (Barbati et al., 2016). Proppant plays an important role in supporting fracture conductivity after hydraulic fracturing. The flow of sand-carrying fluid is a complicated process (Osiptsov, 2017; Lecampion and Garagash, 2014). Therefore, studying the transportation and distribution of proppant in fractures has an important impact on evaluating the reservoir stimulation effect. Most previous studies were based on the fact that the fractures were planar, and they conducted experiments on proppant transportation rules by building visual devices. Babcock et al. (1967) first proposed two parameters describing proppant distribution, namely equilibrium velocity and bank build-up constant, through straight fracture experiments. Based on the research, Clark et al. (1977) designed a transparent and planar fracture model to observe the suspended prop flow. Later, Roodhart (1985) built a vertical slot flow model to study the proppant setting in non-Newtonian fracturing fluids. Then, Liu and Sharma (2005) presented an experimental study to investigate the impact of fracture width and fluid rheology on proppant transportation. Fernández et al. (2015) showed the final proppant placement under different pumping rates and particle sizes by a narrow planar wedge-shaped fracture setup. Through similar experimental equipment, Peng et al. (2023) studied the effects of pumping rates, liquid viscosity and proppant type on the stimulation.