Numerical study on the effect of discontinuous proppant pumping on the proppant distribution and fracture conductivity

The pump schedule with intermittent injection of proppant has been adopted in hydraulic fracturing of oilfield, with an expectation for its ability to enhance the fracture conductivity and reduce the usage of proppant, like the technology named as channel fracturing. The industrial demand has stimulated many scholars to carry out a series of researches related to the performance of discontinuous proppant pumping and obtained favorable feedbacks. However, how do different proppant schemes quantify their impact on the fracture conductivity are still unclear and this leads to challenges for optimization of such schemes. Therefore, in this paper, a planar 3D fracturing model with fluid-solid coupling is presented to simulate the fracturing process by adopting discontinuous proppant pumping, for quantificationally estimating the fracturing performance. First, thirteen groups of comparable cases were elaborately designed by varying the treatment parameters respectively. Subsequently, these numerical results were analyzed to discuss in detail the effects of proppant usage amount, particle size, volume fraction and pump schedule on the proppant distribution and conductivity within the fracture. An interesting insight is found that a reducing of proppant usage by about 20% with a proper scheme can still maintain enough high conductivity without significant damage of flow path. In the case for using relatively small to medium-sized proppant, a more aggressive proppant scheme is recommended to enhance the fracture conductivity. Also, intermittent proppant pumping with a higher frequency is proposed especially in the case of using large-sized proppant, as its effectiveness for profitably adjusting the proppant distribution and increasing the median conductivity. This study provides useful guidance for optimization design of hydraulic fracturing.