Since the coal seam is soft with low permeability in China, the stimulation effect of vertical well hydraulic fracturing technology is limited while horizontal well fracturing has instable wellbore leading to wellbore collapsing. Therefore, floor horizontal well hydraulic fracturing technology is proposed, that is drilling in the floor sandstone and connecting the coal seam by hydraulic fractures. A test area has been undertaken in 3# coal seam, southern Qinshui Basin, to demonstrate this technology. Through optimizing the well path, borehole structure, fracturing designs, and fracture propagation performance, a set of treatments were developed and applied successfully. The result shows that drilling floor horizontal well along with minimum horizontal principle stress, applying U-type well structure, and designing fractures with 3 stages, 130m half fracture length and 30D·cm flow conductivity achieves better production performance.

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