Drill-power-based directional hydraulic fracturing system for downhole quick slotting and method thereof

Abstract

Provided are a drill-power-based directional hydraulic fracturing system for downhole quick slotting and a method thereof. The directional hydraulic fracturing system includes a water injection pump, a high pressure rubber pipe arranged on the water injection pump is in communication with a drill, a dedicated sealing drill rod for hydraulic fracturing is arranged on the drill, a front segment of the drill rod may be connected with a directional borehole sealer through threads and a sealing ring is provided at the threaded connection. The main steps include drilling, slotting, borehole sealing and fracturing. Firstly, a drill-cut integrated tool is installed at a front end of the drill rod. After drilling is completed, hydraulic slotting, permeability improvement and pressure relief are performed without changing a drill bit. After slotting is completed, the drill bit is retreated, and the directional borehole sealer is installed and pushed to a predetermined position for efficiency sealing. After sealing is completed, high pressure water injection fracturing is performed to increase fissure density and scope with high pressure penetration as main. Thus, water injection for the coal seam with high ground pressure and low porosity is realized. In this way, coal bumps are effectively prevented, the powder dust concentration is reduced and the disasters such as gas and fire are prevented.

Claims

1. A drill-power-based directional hydraulic fracturing method for downhole quick slotting, comprising a drill-power-based directional hydraulic fracturing system for downhole quick slotting, comprising a drill, wherein a water injection pump and a drill are connected with a high pressure rubber pipe and a dedicated sealing drill rod is arranged on the drill; a drill-cut integrated tool is arranged at a front end of the drill rod; three gas-water outlets with hole diameters of 6 mm-8 mm are designed on a three-wing drill bit and a reaming drill bit of the drill-cut integrated tool; after drilling is completed, hydraulic slotting is performed directly without retreating the drill bit; a plurality of directional borehole sealers are arranged on the drill rod, the directional borehole sealer comprises an outer shell which is internally provided with a communicating pipe, a lower straight-through opening of the communicating pipe is in communication with a transition pipe, an upper straight-through opening of the communicating pipe is in communication with a water inlet pipe, the communicating pipe between the upper straight-through opening and the lower straight-through opening is provided with a side-through water inlet respectively, and the side-through water inlet is provided with a side through opening; a borehole sealing capsule is provided on the outer shell, a sealing ring is provided on both sides of the borehole sealing capsule respectively, and a plurality of through holes are arranged uniformly on the outer shell in the borehole sealing capsule, and transition pipes between two adjacent directional borehole sealers are connected with a water pipe connector; the directional borehole sealer and the drill rod are arranged in the borehole; the drill rod is a dedicated sealing drill rod for hydraulic fracturing and is provided with a sealing ring so that high pressure water enters the directional borehole sealer through the drill rod, wherein the method is performed according to the steps of drillingslottingborehole sealingfracturing as follows: A. a drill-cut integrated tool is installed at a front segment of the drill rod to perform drilling by starting the drill; during the drilling, the gas-water outlets on the three-wing drill bit and the reaming drill bit act to discharge slags; after the hydraulic cut drilling reaches a predetermined position, the water injection pump is started and switched to high pressure water; the drill remains in a rotation state, and a coal mass is cut with the hydraulic power in the borehole to form a hydraulic slot; after slotting requirements are satisfied, rotation and high pressure water are both stopped and the drill rod is pulled out slowly; B. the drill-cut integrated tool is disassembled and the directional borehole sealer is assembled; the threaded connection of the drill rod and the directional borehole sealer is well sealed; the drill is started to push the directional borehole sealer to a predetermined position; the water injection pressure is set to less than 5 MPa; the pressurized water supplied by the water injection pump is transported to the drill through a high pressure rubber pipe so that the pressurized water enters the drill rod and further enters the directional borehole sealer; low pressure water enters the interior of the borehole sealing capsule through the water inlet pipe of the directional borehole sealer; the lower straight-through opening serves as a water inlet and the upper straight-through opening serves as a water outlet; water is injected into the borehole sealing capsule through the side-through opening; the outer shell has a through hole connected with the borehole sealing capsule; both ends of an outer wall of the outer shell are provided with a sealing ring for fixing the borehole sealing capsule respectively; when the borehole sealing capsule is filled up with water, the borehole sealing capsule has a diameter of greater than 94 mm and thus effectively seals the borehole; when the water injection pressure exceeds 5 MPa, a pressure control valve on the directional borehole sealer will open to allow high pressure water to enter the borehole; C. after the borehole sealing is completed, hydraulic fracturing is performed; the water injection pressure is slowly increased to 30 MPa while change of a pressure gauge is observed; the high pressure water injection is performed for 10 minutes; the first stage of fracturing work is completed; after the water injection pump is shut down and the pressure is released, the directional borehole sealer restores to a normal size; D. the drill is adjusted to pump the directional borehole sealer to the second stage of fracturing work; the second stage of the fracturing work is performed by repeating steps B and C and so on until the fracturing work is completed.

2. The drill-power-based directional hydraulic fracturing method for downhole quick slotting according to claim 1, wherein the above drill-cut integrated tool comprises a reaming drill bit, a three-wing drill bit is provided at a front end of the reaming drill bit, and gas-water outlets are provided on the three-wing drill bit and the reaming drill bit behind the three-wing drill bit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram illustrating a structure of a directional borehole sealer according to an example of the present disclosure.

(2) FIG. 2 is a schematic diagram illustrating a structure of a hydraulic fracturing system according to an example of the present disclosure.

(3) FIG. 3 is a schematic diagram illustrating a structure of a drill-cut integrated tool according to an example of the present disclosure.

(4) Numerals of drawings are described as follows: 1water inlet pipe, 2sealing ring, 3borehole sealing capsule, 4side through water inlet, 5side through opening, 6water pipe connector, 7upper straight through opening, 8through hole, 9outer shell, 10low straight through hole, 11water injection pump, 12high pressure rubber pipe, 13drill, 14borehole, 15drill rod, 16hydraulic slot, 17directional borehole sealer, 18coal mass, 19reaming drill bit, 20gas-water outlet, 21three wing drill bit.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(5) The present disclosure provides a drill-power-based directional hydraulic fracturing system for downhole quick slotting and a method thereof. To make the object, technical solutions and effects of the present disclosure clearer, the present disclosure will be detailed below further. It is understood that the specific examples described herein are merely used for explaining the present disclosure rather than limiting the present disclosure.

(6) The present disclosure provides a drill-power-based directional hydraulic fracturing system for downhole quick slotting. As shown in FIG. 2, the system includes a drill 13. A dedicated hollow sealing drill rod 15 is arranged on the drill 13. A drill-cut integrated tool is arranged on a front end of the drill rod 15. Further, the drill rod 15 is further provided with a directional borehole sealer 17. The directional borehole sealer 17 is arranged in a borehole 14 together with the drill rod 15. A high pressure rubber pipe 12 is in communication with a water injection pump 11 to supply corresponding pressurized water. The above drill-cut integrated tool includes a reaming drill bit 19. A three wing drill bit 21 is provided on a front end of the reaming drill bit 19. Gas-water outlets 20 are provided on the three wing drill bit 21 and the reaming drill bit 19 behind the three wing drill bit 21. As shown in FIG. 1, the above directional borehole sealer includes an outer shell 9. The outer shell is internally provided with a communicating pipe. A lower straight-through opening 10 of the communicating pipe is in communication with a transition pipe and an upper straight-through opening 7 of the communicating pipe is in communication with a water inlet pipe 1. The communicating pipe between the upper straight-through opening 7 and the lower straight-through opening 10 is provided with a side-through water inlet 4. The side-through water inlet 4 is provided with a side through opening 5. The outer shell 9 is provided with a borehole sealing capsule 3, and a sealing ring 2 is provided on both sides of the borehole sealing capsule 3 respectively. A plurality of through holes are uniformly distributed on the outer shell 9 inside the borehole sealing capsule 3. The transition pipes between two adjacent directional borehole sealers are connected with a water pipe connector 6.

(7) The present disclosure further provides a drill-power-based directional hydraulic fracturing method for downhole quick slotting, which mainly includes steps of drilling, slotting, borehole sealing and fracturing. The method include the following steps.

(8) At step A, A drill-cut integrated tool is installed at a front segment of a drill rod 15 to perform drilling by starting the drill. During the drilling, the gas-water outlets 20 on the three wing drill bit and the reaming drill bit act to discharge slags. After the hydraulic cut drilling reaches a predetermined position, the water injection pump 11 is started and switched to high pressure water. The drill 13 remains in a rotation state, and the coal mass is cut with the hydraulic power in the borehole to form a hydraulic slot 16. After slotting requirements are satisfied, rotation and high pressure water are both stopped and the drill rod 15 is pulled out slowly.

(9) At step B, The pressurized water supplied by the water injection pump 11 is transported to the drill 13 through a high pressure rubber pipe 12 so that the pressurized water enters the drill rod 15. The threaded connection of the drill rod 15 and the directional borehole sealer 17 is well sealed. Low pressure water enters the water inlet pipe 1 of the directional borehole sealer 17 through the drill rod 15 and flows into the interior of the borehole sealing capsule 3. The lower straight-through opening 10 serves as a water inlet and the upper straight-through opening 7 serves as a water outlet. Water is injected into the borehole sealing capsule 3 through the side-through opening 6. The outer shell 9 has a through hole connected with the borehole sealing capsule 3. Both ends of an outer wall of the outer shell 9 are provided with a sealing ring for fixing the borehole sealing capsule 3 respectively. When the borehole sealing capsule 3 is filled up with water, the borehole sealing capsule 3 has a diameter of greater than 94 mm and thus can effectively seal the borehole 14. When the water injection pressure exceeds 5 MPa, a pressure control valve on the directional borehole sealer 17 will open to allow high pressure water to enter the borehole 4.

(10) At step C, after step B is completed, hydraulic fracturing is performed. The water injection pressure is slowly increased to 30 MPa while change of a pressure gauge is observed. The water injection is performed for about 10 minutes to complete the first stage of fracturing work. After the water injection pump 11 is shut down and the pressure is released, the directional borehole sealer 17 restores to a normal size.

(11) At step D, The drill 13 is adjusted to pump the directional borehole sealer 17 to the second stage of fracturing work. The second stage of the fracturing work is performed by repeating steps B and C and so on until the fracturing work is completed.

(12) To further describe the present disclosure, descriptions are made below with more detailed examples. The hydraulic fracturing of a coal seam of a roadway side of a mine is taken as example.

(13) At step 1, drilling and slotting

(14) A specially-made drill bit 21 is added before a drilling tool. Three gas-water outlets 20 with hole diameters of 6 mm-8 mm on the drill bit. At the same time, three gas-water outlets 20 are arranged on the reaming drill bit 19. During drilling, the gas-water outlets 20 on the three-wing drill bit 21 and the reaming drill bit 19 act to discharge slags. When the drilling reaches a predetermined position, switching is performed to high pressure water to perform in-borehole hydraulic cutting.

(15) The drill 13 and the drilling tool are installed. After the hydraulic cut drilling reaches a predetermined position, the water injection pump is started and performs corresponding switching. The drill 13 remains in a rotation state for hydraulic cutting. After slotting requirements are satisfied, rotation and high pressure water are both stopped and the drill rod is pulled out slowly. According to the site work, the borehole 14 has a diameter of 94 mm and a hole depth of 40 m and the hydraulic slot 16 has a radius of 0.5 m.

(16) At step 2, the directional borehole sealer performs borehole sealing based on drill power.

(17) Based on the traditional borehole sealing technique, a directional borehole sealer is adopted to perform directional sealing of multi-segment fracturing of long borehole. In this way, pressurized sealing of a middle segment of the borehole is realized to seal a big fissure of the middle segment of the borehole, thereby improving the sealing effect. A pressurized borehole sealing apparatus mainly includes a water injection pump, a high pressure rubber pipe, a drill, a drill rod, and a directional borehole sealer.

(18) The pressurized water supplied by the water injection pump 11 is transported to the drill 13 through a high pressure rubber pipe 12 so that the pressurized water enters the drill rod 15. The threaded connection of the drill rod 15 and the directional borehole sealer 17 is well sealed. Low pressure water enters the water inlet pipe 1 of the directional borehole sealer 17 through the drill rod 15 and flows into the interior of the borehole sealing capsule 3. The outer shell 9 provides support and protection for the borehole sealing capsule 3 to prevent the borehole sealing capsule 3 from being damaged due to deformation occurring at the time of assembly and deep drilling. The lower straight-through opening 10 serves as a water inlet and the upper straight-through opening 7 serves as a water outlet. Water is injected into the borehole sealing capsule 3 through the side-through opening 6. The outer shell 9 has a through hole connected with the borehole sealing capsule 3. Both ends of an outer wall of the outer shell 9 are provided with a sealing ring for fixing the borehole sealing capsule 3 respectively. When the borehole sealing capsule 3 is filled up with water, the borehole sealing capsule 3 has a diameter of greater than 94 mm and thus can effectively seal the borehole. When the water injection pressure exceeds 5 MPa, a pressure control valve on the directional borehole sealer 17 will open to allow high pressure water to enter the borehole 14.

(19) At step 3, high pressure hydraulic fracturing is performed.

(20) After step 2 is completed, hydraulic fracturing is performed. Water injection pressure is slowly increased to 30 MPa, and water injection is continuously performed for about 10 minutes so that the first stage of fracturing work is completed. After the water injection pump 11 is shut down for pressure relief, the directional borehole sealer 17 restores to a normal size.

(21) At step 4, cyclic work

(22) The drill 13 is adjusted to pump the directional borehole sealer 17 to the second stage of fracturing work. The second stage of the fracturing work is performed by repeating steps B and C and so on until the fracturing work is completed.

(23) Of course, the above descriptions are merely preferred examples of the present disclosure which do not limit the present disclosure. It is noted that all equivalent substitutions and noticeable variations made by persons of skill in the prior art under the teaching of the present disclosure shall fall within the scope of protection of the present disclosure and therefore shall be protected by the present disclosure.