Transport feasibility of proppant by supercritical carbon dioxide fracturing in reservoir fractures

The pure supercritical carbon dioxide (SC-CO2) fracturing prevents the clay from swelling and avoids the water lock as compared with the slick-water fracturing. The CO2 molecule could replace the CH4 adsorbed in organic matter and tiny particles on the clay mineral surface in the formation. This leads to an increased cumulative gas production rate. The SC-CO2 fracturing is an alternative waterless fracturing technique for an effective future development of shale gas reservoirs. Due to its low density and viscosity as compared with the slick-water, it attracts attentions for the proppant transport. In this paper, the two phase flow of the SC-CO2 and the proppant in fractures during the SC-CO2 fracturing is analyzed with the computational fluid dynamics method. The characteristics of the proppant transport by the SC-CO2 fracturing and the slick-water fracturing are compared. Moreover, a sensitivity analysis is also performed to see the influence of various parameters on the proppant transport ability of the SC-CO2 fracturing. It is shown that the proppants in the SC-CO2 and the slick-water have similar distribution characteristics. Reducing the proppant density, the proppant diameter, and the solid volume fraction as well as increasing the injection rate can all have similar filling effects on the fractures. The feasibility of the proppant transport by the SC-CO2 fracturing in fractures is revealed and a guidance is provided for the SC-CO2 fracturing design.