Modeling and Analysis of Micro Proppant Transport and Deposition in Rough Fracture Networks

ABSTRACT Micro-proppants are instrumental in maintaining secondary fractures, which evolve around primary propped fractures in unconventional formations. Given their minute size, micro-proppants can infiltrate induced fractures, thereby augmenting production through the fracture network. Yet, the mechanisms through which micro-proppants bolster the conductivity of secondary fractures remain incompletely elucidated. To bridge this knowledge gap, we have conducted a simulation study that models the transport and sedimentation of micro-proppants in rough fractures. We utilized a coupled computational fluid dynamics and discrete element method (CFD-DEM) for this purpose. Our research also considers key determinants such as particle properties, fracture morphology, and injection parameters to assess their impact on the flow field and micro-proppant distribution. Preliminary findings indicate that, unlike larger proppants, micro-proppants are not impeded by rough and tortuous fracture surfaces, enabling a more uniform proppant distribution due to their smaller particle size. These insights deepen our comprehension of particle settling behavior in rough rock fractures and underscore the benefits of using micro-proppants. They will also assist in the design of more effective fracture enhancement projects. INTRODUCTION Hydraulic fracturing serves as a pivotal method for enhancing oil and gas recovery from wells. This is accomplished by the high-pressure injection of a mixture comprising water, sand, and chemicals into rock formations. This process induces fractures in the rock, thereby releasing entrapped hydrocarbons. Despite its experimental beginnings in 1947 in the Hugoton gas field of Grant County, Kansas, in the United States, the first successful commercial application was not realized until 1950. Numerous oil and gas fields would be economically nonviable without the implementation of hydraulic fracturing. Proppants, solid particles instrumental in maintaining the created fracture pathways and preventing fracture closure post-fluid injection, are an integral part of the fracturing process. The placement and properties of the proppant bed within the stimulated fracture network are crucial determinants of the efficacy of the fracture network and the eventual productivity of the well (Kong et al., 2015; Montgomery et al., 2010). Recent decades have witnessed improved understanding of proppant transport mechanisms in hydraulic fracturing, thanks to numerical simulation. This has led to the optimization of proppant types, fracturing fluid compositions, and injection strategies.