Progressive gas extraction method for soft coal seam area

Abstract

The application discloses a kind of soft coal seam area progressive gas extraction method, belong to gas control technical field.The method includes the following main steps: A, first area gas extraction construction:a, construction first stage gas extraction borehole;B, form first stage effective extraction area;C, construction second stage gas extraction borehole;D, form second stage effective extraction area;E, construction third stage gas extraction borehole;F, form third stage effective extraction area;B, other area gas extraction construction: repeat step a to step f in step A, and first stage gas extraction borehole in the latter area is located in the third stage effective extraction area in the former area;C, repeat step B, i.e., gradually complete the gas extraction work of entire coal seam between already excavated roadway and to be excavated roadway.The method can reduce drilling workload, improve hole completion rate, improve gas extraction efficiency and soft coal seam mining safety.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of soft coal seam area progressive gas extraction method, belong to gas control technical field. BACKGROUND

[0002] Soft coal seam is generally defined as the coal seam with the anti-loose strength less than 50% and the firmness coefficient not more than 1.0. It also has low permeability, high gas content and high pressure. High gas and coal and gas outburst have been restricting the safe and efficient production of mine. Production practice shows that gas extraction is an effective technical means to prevent and control gas accidents and realize rational utilization of gas.

[0003] Chinese patent document with publication number CN107740677A discloses a kind of soft coal seam across working face long drilling gas extraction method, comprising: drilling construction step, in the coal seam working face one side has been excavated roadway, along the coal seam construction long drilling gas extraction to the other side to be excavated roadway;Screen pipe placement step, lower into hole protection screen pipe in the long drilling gas extraction;Gas extraction step, connect gas extraction pipeline with hole protection screen pipe to carry out gas pre-extraction. It can realize long drilling construction of soft coal seam in coal mine, through effective control of drilling trajectory, it can improve drilling depth and greatly improve coal seam drilling rate. Through drilling trajectory measurement, actual drilling trajectory can be determined, to avoid the blind area of extraction in conventional drilling construction as much as possible, which is beneficial to realize regional gas control.

[0004] However, the gas extraction method has the following disadvantages:

[0005] Firstly, each soft coal seam long drilling hole extends from the excavated roadway to the to-be-excavated roadway, the drilling depth of the long drilling hole is long, and the hole forming rate is low.

[0006] Secondly, there is an extraction blind area when the long drilling holes are arranged in a fan shape, which leads to insufficient gas extraction and increases the safety risk of soft coal seam mining. When the long drilling holes are arranged in parallel, the drilling workload is huge due to the need to extend each long drilling hole from the excavated roadway to the to-be-excavated roadway and the low hole forming rate, which significantly reduces the gas extraction efficiency. SUMMARY

[0007] To solve the above technical problems, the present application provides a kind of soft coal seam area progressive gas extraction method.

[0008] The present application is realized by the following technical solutions:

[0009] A kind of soft coal seam area progressive gas extraction method, comprising the following main steps:

[0010] A, first area gas extraction construction:

[0011] a. drilling the first stage gas extraction borehole along the coal seam in the direction of the to-be-excavated roadway in the excavated roadway on one side of the coal seam face;

[0012] b. extracting gas using the first stage gas extraction borehole, the gas extraction time being t1, to form a first stage effective extraction area;

[0013] c. drilling the second stage gas extraction borehole along the coal seam in the direction of the to-be-excavated roadway in the excavated roadway, the depth of the second stage gas extraction borehole being d2, d1 < d2 < the distance between the excavated roadway and the to-be-excavated roadway, and the second stage gas extraction borehole penetrating the first stage effective extraction area;

[0014] d. extracting gas using the second stage gas extraction borehole, the gas extraction time being t2, t2 > t1, to form a second stage effective extraction area;

[0015] e. drilling the third stage gas extraction borehole along the coal seam in the direction of the to-be-excavated roadway in the excavated roadway, the depth of the third stage gas extraction borehole being d3, and the third stage gas extraction borehole penetrating the second stage effective extraction area and the to-be-excavated roadway;

[0016] f. extracting gas using the third stage gas extraction borehole, the gas extraction time being t3, t3 > t2, to form a third stage effective extraction area;

[0017] B. other gas extraction construction in the area: repeating steps a to f in step A, and the first stage gas extraction borehole in the next area being located in the third stage effective extraction area in the previous area;

[0018] C. repeating step B, which can gradually complete the gas extraction work in the entire coal seam between the excavated roadway and the to-be-excavated roadway.

[0019] In step A, 1 / 3 of the distance between the excavated roadway and the to-be-excavated roadway < d1 < 1 / 2 of the distance between the excavated roadway and the to-be-excavated roadway.

[0020] In step A, d2 = 2 x d1.

[0021] The diameters of the first stage gas extraction borehole, the second stage gas extraction borehole and the third stage gas extraction borehole are all greater than 85 mm.

[0022] The drilling speed of the first stage gas extraction borehole, the second stage gas extraction borehole and the third stage gas extraction borehole is 0.5-1 m / min.

[0023] The second stage gas extraction borehole is close to the edge of the first stage effective extraction area, the third stage gas extraction borehole is close to the edge of the second stage effective extraction area, and the first stage gas extraction borehole in the latter area is close to the edge of the third stage effective extraction area in the former area.

[0024] The extraction negative pressure of the gas extracted in step A is 8-20 KPa.

[0025] t1=10 days, t2=30 days, and t3=40 days in step A.

[0026] The effective extraction radius of the first stage effective extraction area, the second stage effective extraction area, and the third stage effective extraction area R = Aln ( t) + B , wherein t is the gas extraction duration, in days, A , B is a coefficient.

[0027] The inclination length of the coal seam working face is 160-200 m.

[0028] The beneficial effects of the present application are as follows:

[0029] 1. In the same area, the gas extraction borehole of the latter stage penetrates the effective extraction area of the former stage, and the hardness of the coal seam in the range of the effective extraction area of the former stage has been effectively improved after gas extraction, significantly reducing the probability of hole collapse and sticking of the gas extraction borehole of the latter stage, and greatly improving the hole completion rate.

[0030] 2. Three gas extraction boreholes are arranged in the same area, and the depth of the first stage gas extraction borehole is less than the depth of the second stage gas extraction borehole, which is less than the distance between the excavated roadway and the to-be-excavated roadway. Therefore, the number of gas extraction boreholes in the same area is small, and the depth of the first stage gas extraction borehole and the second stage gas extraction borehole is small, which reduces the drilling workload while improving the hole completion rate and efficiency of the first stage gas extraction borehole and the second stage gas extraction borehole.

[0031] 3. The depth of the gas extraction borehole of each stage in the same area and the gas extraction duration of each stage effective extraction area are designed to ensure that the effective extraction area of the latter stage completely covers the effective extraction area of the former stage, and the third stage effective extraction area covers the to-be-excavated roadway, completely eliminating the gas extraction blind area in the area, ensuring that the gas in the area can be fully extracted, and significantly improving the safety of soft coal seam mining in the area.

[0032] 4. The first-stage gas drainage borehole in the later area is located in the third-stage effective drainage area of ​​the previous area. While improving the borehole formation rate of the first-stage gas drainage borehole in the later area, it also makes the third-stage effective drainage areas of the front and rear areas partially overlap, completely eliminating the gas drainage blind zone between adjacent areas and improving the safety of soft coal seam mining between the extended roadway and the roadway to be excavated.

[0033] 5. The drilling depth of gas drainage boreholes in the same area is progressively advanced, while the effective drainage areas of the third stage in adjacent areas are overlapped and progressively arranged. This reduces the amount of drilling work, increases the borehole formation rate, and improves the efficiency of gas drainage and the safety of mining soft coal seams. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the progressive drilling design for soft coal seam areas according to the present invention.

[0035] Figure 2 This is a schematic diagram of the progressive effective extraction area layout in the soft coal seam region according to the present invention.

[0036] Figure 3 The effective gas extraction radius of this invention R With sampling duration t The fitted curve. Detailed Implementation

[0037] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0038] like Figure 1 and Figure 2 As shown, the progressive gas extraction method for soft coal seams according to the present invention includes the following main steps:

[0039] A. Gas extraction construction in the first area:

[0040] a. Construct the first-stage gas drainage borehole along the coal seam towards the roadway to be excavated on one side of the coal seam working face. The depth of the first-stage gas drainage borehole is d1. When using it, select a ZUW-1900R drilling rig, connect the drill bit to the drilling rig, calibrate the hole position, and then drill down to the designed hole depth.

[0041] b. Gas is extracted using the first-stage gas extraction boreholes, with a gas extraction time of t1, forming the first-stage effective extraction area.

[0042] c. drilling the second stage gas extraction borehole in the direction of the to-be-excavated roadway along the coal seam in the excavated roadway, the depth of the second stage gas extraction borehole being d2, d1 < d2 < the distance between the excavated roadway and the to-be-excavated roadway, and the second stage gas extraction borehole penetrating the first stage effective extraction area.

[0043] d. extracting gas by using the second stage gas extraction borehole, the gas extraction time being t2, t2 > t1, and forming a second stage effective extraction area.

[0044] e. drilling the third stage gas extraction borehole in the direction of the to-be-excavated roadway along the coal seam in the excavated roadway, the depth of the third stage gas extraction borehole being d3, and the third stage gas extraction borehole penetrating the second stage effective extraction area and the to-be-excavated roadway.

[0045] f. extracting gas by using the third stage gas extraction borehole, the gas extraction time being t3, t3 > t2, and forming a third stage effective extraction area. The third stage gas extraction borehole penetrates the to-be-excavated roadway, and the gas extraction time is t3 > t2, which ensures that there is no blind area in the gas extraction of the area, and the area of the third stage effective extraction area is the effective gas extraction area of the corresponding area.

[0046] B. Gas extraction construction in other areas: repeat steps a to f in step A, and the first stage gas extraction borehole in the latter area is located in the third stage effective extraction area in the former area. Ensure that there is no gas extraction blind area between adjacent areas.

[0047] C. Repeat step B to gradually complete the gas extraction work of the entire coal seam between the excavated roadway and the to-be-excavated roadway.

[0048] After the gas extraction borehole is completed, one end of the hole protection screen pipe is lowered into the bottom of the gas extraction borehole, and the other end extends outside the hole. A PVC pipe or a steel pipe is sleeved on the hole outside section of the hole protection screen pipe and is sealed. The hole protection screen pipe is connected with the negative pressure gas extraction pipeline, and gas extraction can be started according to the designed time to form the corresponding effective extraction area.

[0049] In step A of the present application, 1 / 3 of the distance between the excavated roadway and the to-be-excavated roadway < d1 < 1 / 2 of the distance between the excavated roadway and the to-be-excavated roadway.

[0050] In step A of the present application, d2 = 2 x d1.

[0051] The diameters of the first stage gas extraction borehole, the second stage gas extraction borehole and the third stage gas extraction borehole are all greater than 85 mm. In the process of coal seam directional drilling extraction, the large-diameter borehole has better hole forming effect than the small-diameter borehole, and the hole diameter greater than 85 mm is more conducive to improving the extraction effect.

[0052] The drilling speed of the first stage gas extraction drill hole, the second stage gas extraction drill hole and the third stage gas extraction drill hole is 0.5-1 m / min. If the drilling speed is too small, the drilling efficiency will be reduced; if the drilling speed is too large, the hole collapse will be easily caused; therefore, the drilling speed is designed as 0.5-1 m / min, which ensures the hole forming rate and the drilling efficiency.

[0053] The second stage gas extraction drill hole is close to the edge of the first stage effective extraction area, the third stage gas extraction drill hole is close to the edge of the second stage effective extraction area, and the first stage gas extraction drill hole in the latter area is close to the edge of the third stage effective extraction area in the former area. Under the premise of ensuring the hole forming rate and eliminating the gas extraction blind area, the spacing between the holes is as large as possible, so as to reduce the number of drill holes and the drilling workload, and improve the gas extraction efficiency.

[0054] The extraction negative pressure of the gas extracted in the step A is 8-20 KPa.

[0055] In the step A, t1=10 days, t2=30 days, and t3=40 days.

[0056] The effective extraction radius of the first stage effective extraction area, the second stage effective extraction area and the third stage effective extraction area R = Aln ( t) + B , wherein t is the gas extraction duration, in days, A , B is a coefficient. According to the formula, the effective extraction radius R increases with the extension of the extraction duration t , but there is a limit, when the extraction duration t is greater than 10 days, the change of the extraction negative pressure has a negligible effect on the effective extraction radius R . The calculation formula of the effective extraction radius R is designed, which is convenient for determining the hole spacing, eliminating the gas extraction blind area while ensuring the hole forming rate.

[0057] The formula R = Aln(t) + B is a fitting relationship between the effective extraction radius R and the extraction duration t in the actual working condition, which aims to explain the logarithmic relationship between the effective extraction radius R of the gas extraction and the extraction duration t , and the coefficient A, B is different in different working conditions.

[0058] Example: the definition index of the effective extraction radius R is that the residual gas content is less than 6 m3 / t or effective extraction radius is determined when extraction rate reaches 30%. According to the requirement that extraction rate is not less than 30%, residual content of coal seam gas is calculated, and when residual content of coal seam gas at somewhere around the extraction borehole is reduced to the calculated value, it is determined that the position is within the effective influence range of the extraction borehole.

[0059] The comparison and determination results of residual gas content of coal seam after gas extraction and original gas content are shown in the following table:

[0060]

[0061] 4 groups of extraction boreholes are considered to reach the standard after the gas content is reduced by more than 30% after extraction. When the coefficient A =0.6853 and the coefficient B =1.0606, the effective extraction radius R =0.6853 ln is calculated according to the formula t =0.6853 R -1.0606, and the fitting curve of the effective extraction radius Figure 3 and the extraction duration R is obtained, as shown in the figure. t From the fitting curve, it can be seen that the effective extraction radius R and the extraction duration t have a logarithmic relationship, and the effective extraction radius R increases with the extension of the extraction duration t , but the increasing trend is more and more slow, which shows that it is not meaningful to continue extraction after a certain extraction duration t .

[0062] The inclination length of the coal seam working face is 160m~200m. In use, the inclination length of the coal seam working face is 180m. The inclination length of the coal seam working face is a process parameter that must be clearly defined in the early stage of design in combination with mine production capacity, coal seam mining conditions, technical equipment and management level. Increasing the length of the working face is beneficial to efficient production, but too long working face will lead to difficulties in equipment management and safety management, and reduce the advancing speed, which is not conducive to stable and high yield. Too small inclination length of the working face will lead to the fact that mechanical equipment cannot enter or the working space is too small, causing working difficulties and low production efficiency.

[0063] The progressive gas extraction method in the soft coal seam area has the following beneficial effects:

[0064] 1. In the same area, the gas extraction borehole of the next stage penetrates the effective extraction area of the previous stage, and the hardness of the coal seam in the range of the previous stage effective extraction area has been effectively improved after gas extraction, which significantly reduces the probability of hole collapse and sticking of the gas extraction borehole in the later stage, and greatly improves the hole completion rate.

[0065] 2、The same area is arranged three gas extraction drill holes, and the first stage gas extraction drill hole depth < second stage gas extraction drill hole depth < distance between the excavated roadway and the to-be-excavated roadway, so it can be seen that the number of gas extraction drill holes in the same area is small, and the depth of the first stage gas extraction drill hole and the second stage gas extraction drill hole is small, which reduces the drilling workload while improving the hole forming rate and efficiency of the first stage gas extraction drill hole and the second stage gas extraction drill hole; if there are less than three gas extraction drill holes in the same area, the depth of the hole which is smaller than the distance between the excavated roadway and the to-be-excavated roadway will be lengthened, resulting in a decrease in the hole forming rate; and if there are more than three gas extraction drill holes in the same area, although it helps to improve the hole forming rate, it also increases the drilling workload, resulting in a decrease in the gas extraction efficiency.

[0066] 3、The depth of the gas extraction drill hole in each stage in the same area is designed, and the gas extraction time of the effective extraction area in each stage is designed, to ensure that the effective extraction area in the next stage completely covers the effective extraction area in the previous stage, and the third stage effective extraction area covers the to-be-excavated roadway, completely eliminating the gas extraction blind area in the area, ensuring that the gas in the area can be fully extracted, and significantly improving the safety of soft coal seam mining in the area.

[0067] 4、The first stage gas extraction drill hole in the next area is located in the third stage effective extraction area in the previous area, which improves the hole forming rate of the first stage gas extraction drill hole in the next area while making the third stage effective extraction area of the previous and next areas partially overlap, completely eliminating the gas extraction blind area between adjacent areas, and improving the safety of soft coal seam mining between the excavated roadway and the to-be-excavated roadway.

[0068] 5、The hole depth of the gas extraction drill hole in each stage in the same area is progressively excavated, and the third stage effective extraction area of adjacent areas is overlapped and arranged progressively, which reduces the drilling workload, improves the hole forming rate, and improves the gas extraction efficiency and the safety of soft coal seam mining.

Claims

1. A progressive gas extraction method for soft coal seams, characterized in that: The main steps include: A. Gas extraction construction in the first area: a. Construct the first stage gas drainage borehole along the coal seam towards the roadway to be excavated in the already excavated roadway on one side of the coal seam working face. The depth of the first stage gas drainage borehole is d1. b. Gas is extracted using the first-stage gas extraction boreholes. The gas extraction time is t1, forming the first-stage effective extraction area. c. Construct a second-stage gas drainage borehole along the coal seam in the direction of the roadway to be excavated within the already excavated roadway. The depth of the second-stage gas drainage borehole is d2, where d1 < d2 < the distance between the already excavated roadway and the roadway to be excavated, and the second-stage gas drainage borehole penetrates the effective drainage area of ​​the first stage. d. Gas is extracted using the second-stage gas extraction borehole. The gas extraction time is t2, where t2 > t1, forming the effective extraction area for the second stage. e. Construct a third-stage gas drainage borehole along the coal seam in the direction of the roadway to be excavated within the already excavated roadway. The depth of the third-stage gas drainage borehole is d3, and the third-stage gas drainage borehole penetrates the effective drainage area of ​​the second stage and the roadway to be excavated. f. Gas is extracted using the third-stage gas extraction borehole. The gas extraction time is t3, where t3 > t2, forming the effective extraction area of ​​the third stage. B. Gas extraction construction in other areas: Repeat steps a to f in step A, and the first stage gas extraction borehole in the later area is located in the third stage effective extraction area of ​​the previous area. C. Repeat step B to gradually complete the gas extraction work of the entire coal seam between the excavated roadway and the roadway to be excavated; In step A, 1 / 3 of the distance between the excavated roadway and the roadway to be excavated is less than d1, which is less than 1 / 2 of the distance between the excavated roadway and the roadway to be excavated. In step A, d2 = 2 × d1; In step A, the negative pressure for gas extraction is 8 kPa to 20 kPa. In step A, t1 = 10 days, t2 = 30 days, and t3 = 40 days. The effective extraction radii of the first-stage effective extraction area, the second-stage effective extraction area, and the third-stage effective extraction area. R = Aln ( t) + B ,in t This refers to the gas extraction time, expressed in days. A , B is a coefficient.

2. The progressive gas extraction method for soft coal seams as described in claim 1, characterized in that: The diameters of the first-stage gas extraction borehole, the second-stage gas extraction borehole, and the third-stage gas extraction borehole are all greater than 85 mm.

3. The progressive gas extraction method for soft coal seams as described in claim 1, characterized in that: The drilling speed of the first-stage gas extraction borehole, the second-stage gas extraction borehole, and the third-stage gas extraction borehole is 0.5 to 1 m / min.

4. The progressive gas extraction method for soft coal seams as described in claim 1, characterized in that: The second-stage gas drainage borehole is close to the edge of the first-stage effective drainage area, the third-stage gas drainage borehole is close to the edge of the second-stage effective drainage area, and the first-stage gas drainage borehole in the later area is close to the edge of the third-stage effective drainage area in the previous area.

5. The progressive gas extraction method for soft coal seams as described in claim 1, characterized in that: The dip length of the coal seam working face is 160m~200m.

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