The characterization of incline-induced flow conductivity in shale's proppant-packed crack: Lab-scale study

The flow conductivity of crack-bearing shale and its influence factors are crucial for shale gas production. To understand the effect of the inclination angle on the conductivity of cracks, the shale samples with prefabricated cracks were prepared to investigate the conductivity of the proppant-packed cracks by the self-developed sand-carrying and crack-expanding test system. The results indicate that, within the range of 0-3 degrees of inclination angle, the greater inclination angle of cracks leads to lower conductivity. The inclination angle is proportional to the sand production from shale cracks. The increasing inclination angle can reduce the influence of proppant particle size on the conductivity of cracks, it reflected that the roughness of the crack surface reduced from 10.59 to 7.11 and the embeddedness depth of proppant decreased from 0.457 mm to 0.424 mm under closed pressure of 40 MPa. Based on the Hertz contact theory and combining the 3D morphological scanning method, the calculation method for proppant embedding depth and the modified conductivity model in inclined cracks were proposed, finally, the relationship between crack surface roughness and flow conductivity is established considering the crack inclination angle. These new findings provide a theoretical foundation for predicting and optimizing proppant-packed crack conductivity in shale gas mining.