CN106121604B - It is a kind of to utilize CO2Drive away the method for coal-bed gas and residual gas with modified water - Google Patents

Abstract

The invention discloses a method for removing coal seam gas and residual gas by using _CO2 and modified water. The removal of gas and residual gas is carried out in three stages: conventional gas extraction stage, gas phase displacement stage and hydraulic displacement stage; gas drainage is carried out first, followed by the gas phase displacement stage, and finally the hydraulic displacement stage; this method can effectively improve the extraction efficiency of coal seam gas, expand the scope of coal seam gas displacement by using carbon dioxide gas, and improve the coal seam gas displacement. The high permeability provides convenient conditions for hydraulic displacement. By injecting modified water into the coal seam, it not only absorbs the excess carbon dioxide gas in the coal seam, but also penetrates deep into the coal body to increase the water content of the coal seam.

Description

A method for removing coal seam gas and residual gas by using CO2 and modified water

technical field

The invention relates to a method for driving coal seam gas and residual gas, in particular to a method for driving coal seam gas and residual gas by using _CO2 and modified water.

Background technique

At present, coal seam gas is the main source of danger in coal seam mining. The accumulation of a large amount of gas may easily cause coal and gas outburst accidents. Drainage is an effective means to prevent and control coal seam gas disasters.

In order to promote the efficient extraction of coal seam gas, a large number of technicians have proposed displacement of coal seam gas to improve the extraction efficiency. Currently, hydraulic displacement and inert gas displacement are the most widely used methods. Both have their own advantages and disadvantages. Hydraulic flooding can not only displace the gas in the coal seam, but also increase the strength of the coal seam and also play a role in dust suppression. However, compared with gas, the amount of water in the coal seam The infiltration capacity is weak, so the effective range of hydraulic displacement is not ideal, and the drilling space is small in the application, and the construction volume is large. Inert gas (CO ₂ ) has a better effect in driving coal seam gas, and its influence range is larger. However, inert gas remains in the coal seam during the gas removal process, especially CO ₂ , which has a strong adsorption capacity, which far exceeds the gas adsorption capacity in the coal seam, causing unpredictable secondary hidden dangers. How to efficiently drive out gas in coal seams without causing secondary hidden dangers has become a key research work for coal mine disaster prevention and control. It can be seen that scientific methods that can efficiently displace coal seam gas and avoid secondary hidden dangers can provide effective technical support for coal seam gas prevention and control.

Contents of the invention

Aiming at the problems existing in the above-mentioned prior art, the present invention provides a method for driving coal seam gas and residual gas by using _CO2 and modified water, which not only expands the scope of coal seam gas displacement, but also improves the permeability of coal seam to provide water power for hydraulic displacement. Convenient conditions; the residual gas can also be absorbed through hydraulic displacement to avoid the occurrence of secondary hidden dangers.

In order to achieve the above object, the technical solution adopted in the present invention is: the method for utilizing _CO and modified water to drive away coal seam gas and residual gas, the specific steps are:

A. Select an area without faults and gushing water in the coal seam, measure the original gas pressure value in the coal seam in this area, and drill at least three drill holes into the coal seam in the area, and the distance between each drill hole is 10m~15m. Each borehole is connected to the drainage system for gas drainage;

B. During the gas drainage process, monitor and record the gas concentration value of the drainage. When the average gas concentration of each borehole is reduced to 50% of the initial gas concentration, stop the gas drainage for each borehole interval. Connect the borehole where the drainage is stopped to the CO ₂ injection device, and the remaining boreholes are normally used for gas drainage;

C. Turn on the CO ₂ injection device to inject CO ₂ gas into the borehole where the drainage is stopped, and the gas injection pressure is at least twice the original pressure value of the coal seam gas, and the remaining boreholes are normally drained;

D. Monitor and record the mixed gas concentration value extracted from each extraction borehole. When the ratio of _CO2 gas concentration to _CH4 gas concentration in the extracted mixed gas increases to 4:1, turn off the _CO2 injection device. The rest of the boreholes are being drained normally;

E. Remove the CO ₂ injection device, connect the CO ₂ injection boreholes to the drainage system and start the drainage work, and continue to drain each borehole until the mixed concentration of CO ₂ gas and CH ₄ gas drops to 5% of the extracted gas When % is below, disconnect the injection CO _The borehole is connected with the extraction system, and the liquid injection device is connected with the above-mentioned disconnected borehole, and the aqueous solution injected by the liquid injection device is an alkaline mixed solution;

F, the liquid injection device adopts the low-pressure slow injection method to inject water into the borehole. The pressure of the water injection is 2MPa to 4MPa, and the water injection volume is 4% of the coal mass in this area. The coal mass in this area is based on the thickness of the coal seam and The range of coal seams in this area is obtained by multiplying the volume of coal in this area by the density of coal, and the remaining boreholes continue to carry out drainage work;

G. When liquid seeps out of the drill hole that is continuously pumped, stop the work of the liquid injection device, disconnect the connection between the water injection hole and the liquid injection device, connect the water injection hole to the drainage system, and start the pumping. Drainage continued in all boreholes until the drainage system was removed when mining began to mine the coal seam in the area.

Further, the alkaline mixed solution is a saturated NaOH aqueous solution.

Further, the distances between the various boreholes are 10m.

Compared with the prior art, the present invention adopts three stages to remove gas and residual gas: conventional gas drainage stage, gas phase displacement stage and hydraulic displacement stage; gas drainage is carried out first, then gas phase displacement stage, The final hydraulic displacement stage; this method can effectively improve the extraction efficiency of coal seam gas, use carbon dioxide gas to expand the range of coal seam gas displacement, and improve the permeability of coal seams to provide convenient conditions for hydraulic displacement. Injecting modified water not only absorbs excess carbon dioxide gas in the coal seam, but also penetrates deep into the coal body to increase the water content of the coal seam.

Description of drawings

Fig. 1 is the construction position schematic diagram of the present invention.

In the figure: 1, coal seam, 2, rock formation.

Detailed ways

The present invention will be further described below.

Embodiment: as shown in Figure 1, concrete steps of the present invention are:

A. Select an area without faults and gushing water in the coal seam, measure the original gas pressure value in the coal seam in this area, and drill three boreholes into the coal seam, namely A borehole, B borehole and C borehole. The distance between the two boreholes is 10m~15m. After completion, the three boreholes are connected to the drainage system for gas drainage;

B. During the process of gas drainage, monitor and record the gas concentration value of the drainage. When the average gas concentration of each drilling hole is reduced to 50% of the initial gas concentration, stop the gas for drilling A and C Drainage, connect borehole A and borehole C to the _CO2 injection device, and borehole B is normally used for gas drainage;

C. Turn on the CO ₂ injection device to inject CO ₂ gas into boreholes A and C, the gas injection pressure is at least twice the original pressure value of the coal seam gas, and the drainage work is carried out normally in borehole B;

D. Monitor and record the mixed gas concentration value extracted from each extraction borehole. When the ratio of _CO2 gas concentration to _CH4 gas concentration in the extracted mixed gas increases to 4:1, turn off the _CO2 injection device. Borehole B is normally drained;

E. Remove the CO ₂ injection device, connect borehole A and borehole C to the drainage system and start the drainage work, and the three boreholes will continue to drain until the mixed concentration of CO ₂ gas and CH ₄ gas decreases to the extracted gas When below 5%, disconnect the A borehole and C borehole and the connection of the extraction system, connect the liquid injection device with the A borehole and the C borehole, and the aqueous solution injected by the liquid injection device is an alkaline mixed solution;

F. The liquid injection device uses a low-pressure slow injection method to inject water into the A borehole and the C borehole. The pressure of the water injection is 2MPa to 4MPa, and the water injection volume is 4% of the coal mass in this area. The coal mass in this area is In order to obtain the coal body volume in the area multiplied by the coal body density according to the thickness of the coal seam and the range of the coal seam in the area, the B borehole continues to carry out drainage work;

G. When the liquid seeps out in the continuous drainage of borehole B, stop the liquid injection device, disconnect the connection between borehole A and borehole C and the liquid injection device, and connect borehole A and borehole C into the drainage system , the drainage was started, and the three boreholes continued to drain until the drainage system was removed when the coal seam in the area began to be mined.

Further, the alkaline mixed solution is a saturated NaOH aqueous solution.

Further, the three boreholes are separated by 10m.

Claims (3)

1. a kind of utilizing CO₂Drive away the method for coal-bed gas and residual gas with modified water, which is characterized in that the specific steps are：

A, the region that selection is discharged without tomography and no swell in coal seam, measures gas reset pressure value in the regional coal-seam, to area At least three drillings are set in the coal seam of domain, 10m~15m is separated by between each drilling, after the completion to each drilling connection extraction system System carries out gas pumping；

B, the gas concentration that extraction goes out is monitored and recorded during gas pumping, when the average mash gas extraction concentration of each drilling When being reduced to the 50% of initial mash gas extraction concentration, each drilling is spaced and stops gas pumping, drilling and the note of extraction will be stopped CO₂Device connects, remaining drilling is normally carried out gas pumping；

C, note CO is opened₂Device injects CO into the drilling for stopping extraction₂Gas, gas injection pressure are at least coal-bed gas original 2 times of beginning pressure value, remaining drilling are normally carried out extraction work；

D, the mixed gas concentration value extracted out in each extraction borehole is monitored and records, as CO in the mixed gas that extraction goes out₂Gas Concentration and CH₄Gas concentration ratio is increased to 4:When 1, note CO is closed₂Device, remaining drilling are normally carried out extraction work；

E, note CO is removed₂Device will note CO₂Drilling connect with extraction system after start extraction work, it is each drilling continue extraction Until CO₂Gas and CH₄When gas mixture concentration is down to extraction and goes out 5% or less gas, note CO is disconnected₂Drilling and extraction system Connection, priming device is connect with the drilling of above-mentioned disconnection, and the aqueous solution of the priming device injection is alkaline mixed solution；

F, it is 2MPa to 4MPa, water filling that priming device, which uses low pressure slow injection mode aqueous solution into drilling, aqueous solution pressure, Amount of solution is the 4% of the region coal body quality, and the described region coal body quality is to be obtained according to coal seam thickness and the regional coal-seam range Go out the region coal body volume and be multiplied by coal body density, remaining drilling persistently carries out extraction work；

G, when liquid exudation occurs in the drilling of lasting extraction, stop priming device work, disconnect aqueous solution drilling and fluid injection Aqueous solution drilling is connected into extraction system by the connection of device, proceeds by extraction, and all drillings continue extraction until starting to adopt Extraction system is removed when digging the regional coal-seam.

2. utilizing CO according to described in claim 1₂Drive away the method for coal-bed gas and residual gas, feature with modified water It is, the alkaline mixed solution is the NaOH aqueous solutions of saturation.

3. utilizing CO according to described in claim 1₂Drive away the method for coal-bed gas and residual gas, feature with modified water It is, is separated by 10m between each drilling.