CFD-DEM Approach to Study the Proppant Transport and Placement under Different Perforation Conditions in Tortuous Hydraulic Fractures

Summary Hydraulic fracturing technology is widely used to extract unconventional and conventional gas/oil reservoirs. However, the distribution and packing pattern of the proppant remain as significant concerns in hydraulic fracturing, because they help enhance unconventional reservoir production by optimizing operational parameters. Previous studies focused on the proppant transport mechanism with critical factors, such as the perforation condition (perforation properties), in a straight fracture model, but the simplified fracture shape cannot generate enough actual results because the fracture is tortuous after shear displacement. As a result, there is a need to further study the effect of perforation conditions on proppant transport and distribution in tortuous fractures. The aim of this study is to present a combined numerical approach using computational fluid dynamics (CFD) and discrete element method (DEM) to simulate the fluid phase and proppant behavior, respectively. The CFD-DEM model was validated against the experimental results and found to be suitable for predicting proppant transport and distribution with different perforation conditions. The main conclusions are summarized as follows: (1) In various degrees of the tortuous fracture model, the final proppant packing shape was overall quadrilateral under the top- and middle-perforation injection modes. On the contrary, the proppant packing shape was triangular under bottom-perforation injection mode, resulting in a low dune height near the perforation. Furthermore, the final packing patterns changed from double-peaked stack to sole-peaked stack due to the injection mode changing to multiple-perforation injection mode. (2) In the tortuous fracture model, the bottom-perforation injection and multiple-perforation injection mode strategies should be applied first to improve the proppant transport efficiency.