Patent ID: 11970945
Assignee: CHONGQING UNIVERSITY
Field: Civil engineering (Other fields)
Classification: CPC E | IPC E

Claim 4:
5. A dividing drilling slotting-fracturing combined permeability enhancement and hole protection method of the system according to claim 2, comprising following steps:
S201, installing and supporting firmly a drilling rig, a pump, a tank and a connecting pipeline after these equipment are transported to a construction site; connecting the pipeline, an emulsion pump, laying a high-pressure pipeline and debugging the high-pressure pipeline; completing an inspection of related systems after a preparation for equipment installation and connection is completed;
S202, constructing a drainage borehole according to an outburst prevention design of a working face and according to preset positions of a fracturing borehole and a slotting borehole;
S203, sequentially connecting a diamond compact drill bit and a hydraulic slotting shallow spiral drill pipe, and installing a hydraulic slotting spray head with a nozzle at a front end of the high-pressure water jet drill pipe; pushing the drill bit to connect the drill pipe with the drill bit, pushing the drilling rig, starting the drilling rig to make the drill pipe rotate at a low speed, and drilling the borehole by using low-pressure water;
S204, turning on a high-pressure water pump to make the water enter the drill pipe through an ultra-high pressure hose after the drill bit is drilled to a designed position; controlling a stop valve, adjusting a pressure at a drilling rig end, and adjusting the pressure valve to gradually increase the pressure of a jet system; and carrying out rotary cutting on a coal body of a borehole wall by using a high-pressure water jet from a high-pressure spray head after the pressure is stable, where a rotary cutting duration for each cutter is 20-25 minutes;
S205, withdrawing with the drill bit and the drill pipe after a slot is formed, opening a front end fixing device of the support, and leaving the flexible support and the support pipe in the borehole;
S206, controlling the stop valve, letting the water return to a water tank through the high-pressure water pipe, and removing the drill pipe at this position;
S207, disassembling a withdrawn drill pipe after the drill pipe is withdrawn, connecting the water injection support pipe with a hydraulic pump, and applying a hydraulic pressure to a hole protection support; turning on the tractors, triggering the tractors at the slot, and making a first flexible support bundle around the slot through a movement of slide rails;
S208, connecting the water injection support pipe to the hydraulic pump, and applying a hydraulic pressure to the hole protection support to unfold the first flexible support for fitting around the slot;
S209, controlling a stop valve to make the water enter the borehole through the high-pressure water pipe and the drill pipe when the drill bit is withdrawn to a next slotting position, and first delivering the water to the borehole for a period of time to remove residues in the borehole, and then slotting after return water from the borehole is normal;
S210, immediately stopping the pressure and turning off the water pump after all the slotting is completed, closing a pressure relief valve, dismantling a hydraulic slotting shallow spiral integral drill pipe and piling dismantled drill pipes neatly, and keeping a high-low pressure conversion slotting device, a diamond compact drill bit and an ultra-high pressure rotary water tail properly;
S211, constructing the fracturing borehole at an appropriate position on an other side of a gas-rich zone;
S212, adjusting the pressure of a drilling rig end, and drilling from a borehole position of a hydraulic slotting borehole to the preset position with the drilling rig; withdrawing the drill pipe and the drill bit, and meanwhile sealing the borehole in a fracturing area with cement slurry, and leaving a flexible support and the support pipe in the borehole;
S213, adjusting an expansion device of a one-way valve, adjusting the one-way valve according to the fracturing borehole position, and sequentially expanding the flexible support and changing an expansion position of the flexible support;
S214, connecting a high-pressure pipeline adapter to a hydraulic fracturing pump group with a fracturing string to start the hydraulic fracturing pump group, opening the water tank to make the high-pressure water reach a fracturing channel through the high-pressure pipeline, and starting hydraulic fracturing on the slotting borehole;
S215, immediately stopping the pressure and turning off the water pump after the all the fracturing is completed, connecting pipes for gas drainage, and recording a gas drainage concentration and a purity in time; and
S216, opening the one-way valve from an outlet section after the drainage reaches the standard, and starting to relieve the pressure step by step according to the positions of the fracturing borehole and the slot, and recovering the water injection support pipe and the contracted first flexible support.