CN112727403B - Method of Blowout Suppression in Soft Coal Gas Drainage Drilling with Synergy of Floor Slotting and Acid Intrusion - Google Patents

Abstract

The invention discloses a soft coal gas extraction drilling hole spray inhibiting method with cooperation of base plate slotting and acid cutting, wherein a slot is formed below a coal bed through base plate drilling and hydraulic slotting, and a rock breaking zone is formed between the slot and the coal bed; injecting acid liquor into the slot, continuously eroding the rock in the rock breaking zone by the acid liquor, finally forming an acid-eroded crack in the rock breaking zone, forming a passage between the coal bed and the slot, and acidizing the coal bed by the acid liquor entering the passage, thereby effectively promoting gas desorption; in addition, the formed slot not only increases the contact area of the acid liquid and the rock fracture zone, creates a reaction space for acidizing and erosion, but also provides a pressure relief space for the coal dust to gush out under the action of ground stress and gas pressure; the phenomenon that the soft coal gas extraction drill hole is sprayed is effectively inhibited, and the safety of gas extraction is greatly improved; meanwhile, the acid liquor after the reaction can not be remained in the coal body to influence the follow-up exploitation.

Description

Method of Blowout Suppression in Soft Coal Gas Drainage Drilling with Synergy of Floor Slotting and Acid Intrusion

technical field

The invention relates to a method for suppressing blowout in a soft coal gas extraction borehole, in particular to a method for suppressing blowout in a borehole for soft coal gas extraction, in which floor slits and acid intrusion are coordinated.

Background technique

Gas drainage is a key technology for gas disaster control, and more than 80% of coal seams in my country have the characteristics of high gas, low permeability, micro-porosity and strong adsorption, resulting in low gas drainage and high drainage costs. At present, scholars at home and abroad have proposed the methods of hydraulic slitting and acid fracturing to increase coal seam fractures, so as to improve gas drainage efficiency and eliminate the danger of coal seam outburst. However, the existing hydraulic slitting technology is prone to produce water lock effect, which leads to the failure to improve the gas drainage rate of coal seams. In addition, the acid fracturing method has limited acidizing effect due to the small contact area between the acid liquid and the coal body. As the depth increases, the primary fissures and porosity of the coal body become smaller, and it is difficult to achieve the expected effect by simply relying on the acid fracturing method. In addition, there is also a method in the prior art, which uses hydraulic slits to form gaps in the coal seam, and then injects acid solution into these gaps for acidification treatment, thereby increasing the desorption effect of coal seam gas and improving gas drainage efficiency; but This method will cause damage to the soft coal seam. Since the soft coal seam itself has poor supporting effect, the gap will be quickly closed under the action of the internal stress of the soft coal seam, so that the acid liquid injection process cannot continue; at the same time, the acid liquid is directly injected into the coal seam. And stay in the coal seam, resulting in part of the unreacted acid will affect the subsequent mining of the coal seam.

Therefore, how to ensure that the contact area between the acid liquid and the coal body increases to improve the gas desorption effect, and the acid liquid will not remain in the coal body to affect the subsequent mining, and at the same time, it can effectively suppress the pulverized coal injection hole phenomenon in the gas drainage hole , is an urgent technical problem to be solved in this industry.

SUMMARY OF THE INVENTION

Aiming at the problems existing in the above-mentioned prior art, the present invention provides a method for suppressing injection of soft coal gas through drilling holes for gas drainage in soft coal, in which floor slits and acid intrusion are coordinated, which can increase the contact area between the acid liquid and the coal and improve the gas desorption effect. In addition, the acid liquid will not remain in the coal body to affect the subsequent mining, and at the same time, the phenomenon of pulverized coal injection holes in the gas drainage holes can be effectively suppressed.

In order to achieve the above-mentioned purpose, the technical scheme adopted in the present invention is: a method for suppressing injection of soft coal gas through drilling holes for cooperating floor slitting and acid invasion, and the specific steps are:

a. Construct an acid attack hole from the bottom plate to the coal seam, stop drilling at 0.1m from the coal seam, and construct 3 gas drainage holes parallel to the acid attack hole on both sides of the acid attack hole and adjacent to each other. The interval of gas drainage boreholes is 4m. During the drilling process, the rock between the borehole and the coal seam will be shaken and broken, thus forming a rock broken zone;

b. Use hydraulic slitting equipment to extend into the deepest part of the acid invasion drilling hole and the gas drainage drilling hole respectively, and cut a slot with a thickness of 0.1m perpendicular to the acid invasion drilling hole and the gas drainage drilling hole, so that the slot It is interconnected with the acid attack borehole and each gas drainage borehole, and the slot is parallel to the coal seam;

c. Extend one end of the acid injection pipe and one end of the liquid return pipe into the slot through the acid invasion drilling hole, and make one end of the liquid return pipe reach the top of the slot, the other end of the acid injection pipe is equipped with valve A, and the other end of the liquid return pipe is equipped with a valve A. There is a valve B, one end of a plurality of gas drainage pipes is respectively extended into the slot through each gas drainage hole, and a valve C is respectively installed at the other end of each gas drainage pipe;

d. Use a hole sealer to seal the acid invasion hole and each gas extraction hole, and the other end of the acid injection pipe is connected to the acid pump and the acid tank in turn through the pipeline;

e. Close each valve C, open the acid pump, valve A and valve B, and inject the acid in the acid tank into the slot through the acid injection pipe. When the acid flows out from the other end of the return pipe, close the valve A and valve B, at this time, the acid liquid contacts the rock crushing zone in the slot and erodes the rock, so that the coal powder in the coal seam enters the slot through the crack of the rock crushing zone;

f. Open valve B every 24 hours and detect the composition of the effluent. When the content of pulverized coal in the effluent exceeds 40%, open each valve C, empty the acid liquid in the slot, and then drain the return pipe and each gas pump. The mining pipes are all connected to the gas extraction pipe network, and gas extraction from the coal seam starts at this time.

Further, when the bottom plate is argillaceous sandstone, carbonate, metamorphic rock and shale, the composition of the acid solution in parts by mass is: 20-25 parts of hydrochloric acid, 0.8-1.2 parts of thickening agent, 3.5 parts of cross-linking agent and 0.025 part of gel breaker.

Further, when the bottom plate is limestone, marble, quartz sandstone and dolomite, the composition of the acid solution according to the mass fraction is: 15-20 parts of hydrochloric acid, 8-10 parts of formic acid, 1-1.5 parts of corrosion inhibitor, stable iron ions 0.5 to 1 part of the agent and 0.2 to 0.3 part of the drainage aid.

Compared with the prior art, the present invention adopts the synergistic method of floor slitting and acid invasion. First, a slit is formed under the coal seam through the bottom hole drilling technology and the hydraulic slitting technology, and rocks are formed between the slit and the coal seam. crushed zone; then inject acid into the fractured groove, and use the acid erosion method to continuously erode the rock in the rock fractured zone through the acid liquid, and finally form acid-invaded fractures in the rock fractured zone, making the coal seam and fractured zone. A channel is formed, and the acid liquid enters the channel to acidify the coal seam, which effectively promotes gas desorption; in addition, the formed slot not only increases the contact area between the acid liquid and the rock fracture zone, but also creates a reaction space for acidification and erosion. The gushing of powder under the action of ground stress and gas pressure provides a pressure relief space; it prevents the phenomenon of pulverized coal injection holes during the gas extraction process; The invention combines the floor slitting technology with the acid erosion method through the cross-penetration method of various disciplines, which can not only increase the contact area between the acid liquid and the rock without destroying the coal seam, but also solve the coal seam hydraulic slitting. The affected area is small and cannot create enough reaction space for acidification erosion; and because the slot is set in the floor rock layer, it can play a good role in resisting stress and deformation, and can be used continuously; it not only effectively inhibits soft coal The phenomenon of spray holes in gas drainage holes also greatly improves the safety of gas drainage; at the same time, the reacted acid will not remain in the coal body to affect subsequent mining.

Description of drawings

Figure 1 is a schematic diagram of the overall structure of the present invention after construction.

In the picture: 1- Bottom plate, 2- Coal seam, 3- Acid invasion hole, 4- Gas drainage hole, 5- Rock fracture zone, 6- Slot, 7- Acid injection pipe, 8- Liquid return pipe, 9 -Valve A, 10-Valve B, 11-Gas extraction pipe, 12-Valve C, 13-Sealer, 14-Acid pump, 15-Acid tank.

Detailed ways

The present invention will be further described below.

As shown in Figure 1, a method for suppressing blowout by drilling holes for soft coal gas drainage in which floor slits and acid intrusion are coordinated. The specific steps are as follows:

a. Construct an acid attack hole 3 from the base plate 1 to the coal seam 2, stop drilling at 0.1m away from the coal seam, and construct 3 gas drainage drills parallel to the acid attack hole 3 on both sides of the acid attack hole 3 respectively Hole 4, and the interval between adjacent gas drainage holes 4 is 4m. During the drilling process, the rock between the hole and the coal seam 2 will be shaken and broken, thus forming a rock broken zone 5;

b. Use hydraulic slitting equipment to extend into the deepest part of the acid invasion hole 3 and the gas drainage hole 4 respectively, and cut a slot with a thickness of 0.1m perpendicular to the acid invasion hole 3 and the gas drainage hole 4 6. Make the slot 6 communicate with the acid penetration borehole 3 and each gas extraction borehole 4, and the slot 6 is parallel to the coal seam 2;

c, one end of the acid injection pipe 7 and one end of the liquid return pipe 8 are stretched into the slot 6 through the acid invasion drill hole 3, and one end of the liquid return pipe 8 is made to reach the top of the slot 6, and the other end of the acid injection pipe 7 is equipped with a valve A9 , the other end of the liquid return pipe 8 is equipped with a valve B10, one end of a plurality of gas extraction pipes 11 is respectively extended into the slot 6 through each gas extraction hole 4, and the other end of each gas extraction pipe 11 is respectively equipped with a valve B10. valve C12;

d, utilize the hole sealer 13 to seal the acid invasion hole 3 and each gas extraction hole 4, and the other end of the acid injection pipe 7 is connected to the acid pump 14 and the acid tank 15 successively through the pipeline;

e. Close each valve C12, open the acid pump 14, valve A9 and valve B10, and inject the acid in the acid tank 15 into the slot 6 through the acid injection pipe 7, when the other end of the return pipe 8 has acid When flowing out, close valve A9 and valve B10, at this moment, the acid solution is made to contact and erode the rock with the rock crushing zone 5 in the slot 6, so that the pulverized coal in the coal seam 2 enters the slot 6 through the crack of the rock crushing zone 5; When the bottom plate 1 is argillaceous sandstone, carbonate, metamorphic rock and shale, the composition of the acid solution according to the mass fractions is: 20-25 parts of hydrochloric acid, 0.8-1.2 parts of thickener, 3.5 parts of cross-linking agent and 0.025 part of gel breaker; when the bottom plate 1 is limestone, marble, quartz sandstone and dolomite, the composition of the acid solution according to the mass parts is: 15-20 parts of hydrochloric acid, 8-10 parts of formic acid, and 1-1.5 parts of corrosion inhibitor parts, 0.5-1 part of iron ion stabilizer and 0.2-0.3 part of drainage aid; the above-mentioned thickener, crosslinking agent, gel breaker, corrosion inhibitor, iron ion stabilizer and drainage aid are all existing materials.

f. Open the valve B10 every 24h and detect the composition of the effluent. When the content of pulverized coal in the effluent exceeds 40%, open each valve C12, empty the acid liquid in the slot 6, and then empty the liquid return pipe 8 and each The gas extraction pipes 11 are all connected to the gas extraction pipe network, and the gas extraction for the coal seam 2 starts at this time.

Claims (3)

1. a soft coal gas extraction borehole suppression method for cooperating with acid invasion of floor slitting, is characterized in that, concrete steps are: a. Construct an acid attack hole from the bottom plate to the coal seam, stop drilling at 0.1m from the coal seam, and construct 3 gas drainage holes parallel to the acid attack hole on both sides of the acid attack hole and adjacent to each other. The interval of gas drainage boreholes is 4m. During the drilling process, the rock between the borehole and the coal seam will be shaken and broken, thus forming a rock broken zone; b. Use hydraulic slitting equipment to extend into the deepest part of the acid invasion drilling hole and the gas drainage drilling hole respectively, and cut a slot with a thickness of 0.1m perpendicular to the acid invasion drilling hole and the gas drainage drilling hole, so that the slot It is interconnected with the acid attack borehole and each gas drainage borehole, and the slot is parallel to the coal seam; c. Extend one end of the acid injection pipe and one end of the liquid return pipe into the slot through the acid invasion drilling hole, and make one end of the liquid return pipe reach the top of the slot, the other end of the acid injection pipe is equipped with valve A, and the other end of the liquid return pipe is equipped with a valve A. There is a valve B, one end of a plurality of gas drainage pipes is respectively extended into the slot through each gas drainage hole, and a valve C is respectively installed at the other end of each gas drainage pipe; d. Use a hole sealer to seal the acid invasion hole and each gas extraction hole, and the other end of the acid injection pipe is connected to the acid pump and the acid tank in turn through the pipeline; e. Close each valve C, open the acid pump, valve A and valve B, and inject the acid in the acid tank into the slot through the acid injection pipe. When the acid flows out from the other end of the return pipe, close the valve A and valve B, at this time, the acid liquid contacts the rock crushing zone in the slot and erodes the rock, so that the coal powder in the coal seam enters the slot through the crack of the rock crushing zone; f. Open valve B every 24h and detect the composition of the effluent. When the content of pulverized coal in the effluent exceeds 40%, open each valve C, empty the acid liquid in the slot, and then drain the return pipe and each gas pump. The mining pipes are all connected to the gas extraction pipe network, and gas extraction from the coal seam starts at this time. 2. The soft coal gas extraction drilling method for suppressing blowout of a kind of floor slitting and acid invasion phase synergy according to claim 1, is characterized in that, when the floor is argillaceous sandstone or carbonate or metamorphic rock or shale The composition of the acid solution is: 20-25 parts of hydrochloric acid, 0.8-1.2 parts of thickener, 3.5 parts of cross-linking agent and 0.025 part of gel breaker. 3. the soft coal gas extraction borehole suppression method of a kind of floor slotting and acid invasion phase coordination according to claim 1, is characterized in that, when the floor is limestone or marble or quartz sandstone or dolomite, The composition of the acid solution in parts by mass is: 15-20 parts of hydrochloric acid, 8-10 parts of formic acid, 1-1.5 parts of corrosion inhibitor, 0.5-1 part of iron ion stabilizer and 0.2-0.3 part of drainage aid.

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