Proppant Transport Characteristics in Tortuous Fractures Induced by Supercritical CO2 Fracturing

Supercritical CO2 fracturing is an important development trend to reach the goal of "dual carbon" and avoid the problem that hydraulic fracturing is influenced by water resource. In order to clarify the transport characteristics of proppant in the fractures induced by supercritical CO2 fracturing, this paper reconstructs the fracture surface of rock samples after supercritical CO2 fracturing using the laser morphological scanning technology, and establishes a model of proppant carrying and transport of supercritical CO2 in tortuous fractures on the basis of CFDDEM method. In addition, the transport and placement characteristics of proppant in tortuous fractures are analyzed by comparing with flat fractures, and the effects of proppant density, injection rate of proppant carrying liquid, proppant concentration and other key parameters on proppant transport and distribution in fractures are investigated. And the following research results are obtained. First, compared with those in flat fractures, the flow paths of the proppant carrying supercritical CO2 liquid in tortuous fractures are tortuous and diverse, and the proppant presents stronger fluctuations and jumps laterally and vertically during its transport. Second, the proppant placement in tortuous fractures morphologically presents a wavy or even clustered non-uniform distribution. Third, low-density proppant has a better pass-ability in tortuous fractures, and the high injection rate can reduce the influence of tortuous fracture structure on proppant blocking. Fourth, if the concentration of injected proppant in the tortuous fracture is too low, good fracturing support effect cannot be achieved, and the optimal value under the simulation conditions in this paper is around 3%. In conclusion, the simulation results are of important theoretical and engineering significance to understanding the mechanism of proppant blocking in the pumping process of proppant carrying liquid for supercritical CO2 fracturing and optimizing the field fracturing design. (C) 2022 Sichuan Petroleum Administration. Publishing services by Elsevier B.V. on behalf of KeAi Communication Co. Ltd.