Proppant takes an essential role in propping the fracture open after pumping ceases in the horizontal drilling and hydraulic fracturing process for unconventional reservoir. However, the relatively smooth proppant may degrade the surface roughness, and alter the friction type from sliding to rolling, both of which may largely reduce the rock shear resistance. The experimental results show that there is a large decrease on both rock peak shear strength and shear stiffness with addition of proppant. The rock with reducing shear resistance has less ability to resist the horizontal shear stress due to gas transportation in the horizontal direction, making it more possible for the rock to induce relative movement. Based on the experimental data, there is a huge increase in proppant embedment rate with shear stress once obvious relative movement (like dilation) appears. Therefore, it is worth to investigate the change of rock shear resistance with the addition of proppant and keep the actual shear stress within the limit by controlling gas flow rate to prevent the relative movement of rock and maintain better proppant embedment behavior.

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