Method for constructing artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in roof aquifer

A method for constructing an artificial water-conducting channel through pulse hydraulic fracturing of drainage boreholes in a roof aquifer, comprising the following steps:

• S100, collecting hydrogeological information of a mining area, and exploring a specific stratigraphic horizon and water volume of a roof sandstone fissure aquifer;
• S200, extracting rock samples from the roof sandstone fissure aquifer for a segmented pulse hydraulic fracturing simulation experiment to study the relationship of a pulse pressure peak, a pulse frequency, a segment length, a segment interval length, and a fracturing duration with fracture development, so as to determine an optimal pulse frequency, an optimal pulse pressure peak, an optimal segment length, an optimal segment interval length, and an optimal fracturing duration for segmented pulse hydraulic fracturing in a drainage operation area;
• S300, determining drainage borehole arrangement parameters, drainage borehole arrangement forms, and segmented pulse hydraulic fracturing parameters according to a fracture development law and the specific stratigraphic horizon and water volume of the roof sandstone fissure aquifer derived from the segmented pulse hydraulic fracturing simulation experiment;
• S400, drilling according to the drainage borehole arrangement parameters and the drainage borehole arrangement forms, and surveying a site after the drilling, to determine placement positions of pulse hydraulic fracturing equipment;
• S500, installing a water-stopping casing and a matching spherical orifice water shutoff valve at an orifice of the drainage borehole drilled, externally connecting the spherical orifice water shutoff valve to a return flowmeter to monitor a water return volume at the orifice, determining whether the artificial water-conducting channel formed by pulse hydraulic fracturing is connected to water from roof fissures according to the difference between a water injection volume of a pulse hydraulic fracturing pump, a filtration loss of a rock stratum, and the water return volume at the orifice, and estimating a water volume of a water-bearing area of the roof connected to the artificial water-conducting channel;
• S600, before a fracturing operation, arranging an artificial water-conducting trough in a roadway near the orifice of the drainage borehole;
• and after the pulse hydraulic fracturing equipment is transported to a designated operation location, checking equipment quantity and integrity, and connecting the equipment;
• S700, after checking connections of the pulse hydraulic fracturing equipment, sequentially advancing a shutoff valve, a downhole packer, a check valve, a near-orifice packer, and a high-pressure sealed drill rod to a designed first-segment hydraulic fracturing position through a drilling rig to start a segmented pulse hydraulic fracturing operation;
• after the first-segment pulse hydraulic fracturing is completed, retracting part of the high-pressure sealed drill rod through the drilling rig, wherein a total length of the retracted high-pressure sealed drill rod is equal to a segment interval length;
• and then performing next-segment pulse hydraulic fracturing, and repeating the above operations for segmented pulse hydraulic fracturing of a single borehole until the pulse hydraulic fracturing of all fracturing segments designed in the single borehole is completed;
• S800, after the pulse hydraulic fracturing operation is completed, turning off the pulse hydraulic fracturing pump, opening a pressure relief valve in a pipeline to release residual fracturing fluid in the pipeline, and after a pressure in the pipeline drops to 0, sequentially retracting the high-pressure sealed drill rod, the near-orifice packer, the check valve, the downhole packer, the shutoff valve, and other equipment, and checking their integrity;
• repeating the above pulse hydraulic fracturing process and sequentially completing the segmented pulse hydraulic fracturing of all boreholes;
• and
• S900, after completing the pulse hydraulic fracturing operation, monitoring and counting the water return volumes and other parameters of the drainage boreholes, evaluating the effect of pulse hydraulic fracturing on optimizing the drainage of water from the roof sandstone fissure aquifer, and adjusting the spherical orifice water shutoff valve in time to control water outflow from the drainage borehole.