An accurate method for predicting surrounding rock gas outburst

Abstract

The present invention belongs to the technical field of gas prediction, and provides an accurate method for predicting surrounding rock gas outburst. The method includes: preliminarily determining the rock formations that may contain surrounding rock gas; determining the maximum generation of surrounding rock gas in the rock formations that may contain surrounding rock gas; directional tracking of coal seam gas escape to obtain the gas storage in the rock formations that contain surrounding rock gas; surrounding rock gas verification and parameter determination, drilling and exploring the rock formations that may have the danger of surrounding rock gas outburst, determining whether there is surrounding rock gas, and determining surrounding rock gas parameters; dividing the surrounding rock gas outburst danger area and the surrounding rock gas outburst relatively safe area; combining the gas geological map, according to the gas outburst phenomenon in coal tunneling, directly judging whether there is the danger of surrounding rock gas outburst.

Description

Technical Field

[0001] The invention belongs to the technical field of gas prediction and provides an accurate method for predicting surrounding rock gas outburst. Background Art

[0002] Coal and gas outburst is a gas dynamic phenomenon in a mine caused by mining disturbance of gas geological bodies in coal-bearing strata. It is one of the major disasters in underground coal mine production. Due to the limitation of coal and gas outburst mechanism, the current prediction of coal and gas outburst is studied in coal seams, from coal seam to coal seam. Through the theoretical study of coal and gas zoning, it is found that the cause of outburst is another gas geological unit. Therefore, the prediction method of coal and gas outburst has also made a major breakthrough.

[0003] Experts and scholars at home and abroad have conducted a large number of physical simulation tests, but the mechanism of coal and gas outburst is still in the hypothesis stage. The engineering and technical personnel of this application team recognized from engineering practice and expanded the research from coal seams to coal-bearing strata, and proposed the "gas geological zoning theory", which explained the mechanism of coal and gas outburst as follows: During the mining activities in coal-bearing strata, the gas in the coal body near the tunnel and the mining working face diffuses and seeps toward the mining working face, forming a low-potential area. The mining disturbance destroys the closure of the geological body where the elastic energy of gas accumulates, and the gas in the high-potential area spontaneously enters the coal body in the low-potential area, squeezing, splitting, destroying, and crushing the coal body in the low-potential area, causing coal and gas to protrude into the mining space.

[0004] On this basis, the applicant proposed the classification of coal and gas outburst types and the distribution of outburst areas, namely: surrounding rock gas outburst, adjacent coal seam gas outburst and coal seam geological anomaly area gas outburst.

[0005] The applicant believes that coal-bearing strata deposition is divided into source-cap deposition and source-reservoir-cap deposition, with source-reservoir-cap deposition being the main type. Coal seams generate gas and store gas, which is self-generation and self-storage; under source-reservoir-cap deposition conditions, coal seams generate gas and migrate upward to the rock reservoir, which is lower generation and upper storage. Since coal-bearing strata deposition is cyclic deposition, under the conditions of coal seam groups, the rock reservoir can be at the top or the bottom of the coal seam. Therefore, surrounding rock gas outbursts can be further divided into surrounding rock gas outbursts in the roof of coal seams and surrounding rock gas outbursts in the bottom of coal seams. Because the pores and cracks in the surrounding rock are much larger than those in coal seams, the surrounding rock gas is mainly free and its migration is mainly by seepage. The surrounding rock gas concentration is high, the dry gas concentration is greater than 50%, the gas pressure is high, the connectivity is good, and the replenishment is fast. Under suitable conditions, it can even accumulate into reservoirs, causing greater hazards.

[0006] my country has been studying coal seam gas outbursts for a long time and has adopted many control measures, but has just started studying surrounding rock gas outbursts. Therefore, surrounding rock gas outburst predictions should be carried out before mine design, well construction, horizontal extension, and succession of different gas geological mining areas. Summary of the invention

[0007] In order to solve the above problems and realize coal and gas outburst prediction, the present invention provides an accurate surrounding rock gas outburst prediction method.

[0008] The present invention adopts the following technical solution: an accurate method for predicting surrounding rock gas outburst, comprising:

[0009] S100: Based on the type of coal seam deposits mined in the mine, preliminarily determine the rock strata that may contain surrounding rock gas;

[0010] S200: Calculate the coal seam gas loss amount, and determine the maximum generation amount of surrounding rock gas in the rock layer where surrounding rock gas may be stored in step S100 according to the coal seam gas loss amount;

[0011] S300: Directional tracking of coal seam gas loss, analyzing whether the coal seam gas loss is completely lost to the atmosphere, or completely or partially enters the rock formation where surrounding rock gas may be stored, and obtaining the gas storage capacity in the rock formation where surrounding rock gas is stored;

[0012] S400: Surrounding rock gas verification and parameter determination: drilling and exploring the rock formations that may have the danger of surrounding rock gas outburst, determining whether there is surrounding rock gas, and determining the surrounding rock gas parameters;

[0013] S500: Based on the surrounding rock gas parameters actually measured by S400, the surrounding rock gas outburst layer and surrounding rock gas parameters are determined, and then the surrounding rock gas outburst danger area and the surrounding rock gas outburst relatively safe area are divided through gas geological analysis;

[0014] S600: Combined with the gas geological map, based on the gas outburst phenomenon during coal tunneling, directly determine whether there is a danger of gas outburst in the surrounding rock.

[0015] In step S100, the coal seam deposition types include: coal seam deposition types include source-reservoir-cap deposition, source-cap deposition and coal seam group deposition, wherein surrounding rock gas exists in source-reservoir-cap deposition.

[0016] In step S200, the gas loss of the mined coal seam is calculated by the following formula:

[0017] E=Gt-W

[0018] Where, E: coal seam gas loss, m 3 / t;

[0019] Gt: apparent gas generation rate, m 3 / t;

[0020] W: gas content per ton of coal m 3 / t.

[0021] Determine the apparent gas occurrence rate based on the type and rank of coal seams mined in the mine;

[0022] Gt=109.890Ro-21.978

[0023] Where Gt: apparent gas generation rate, m 3 / t;

[0024] Ro: measured vitrinite reflectance of coal type.

[0025] In step S200, the coal seam gas loss amount refers to the amount of gas overflowing into the surrounding rock, and the coal seam gas loss amount = the maximum amount of surrounding rock gas generated.

[0026] In step S300: gas storage capacity = maximum generation of surrounding rock gas - coal seam gas loss.

[0027] In step S400, the surrounding rock gas parameters include surrounding rock gas pressure, concentration, extraction flow rate and barrier layer thickness; surrounding rock gas pressure ≥ 0.5 MPa, gas extraction flow rate ≥ 0.1 m 3 / min and the concentration is ≥30%, it is determined that surrounding rock gas exists.

[0028] Step S500 includes:

[0029] S501: Calculate the protrusion hazard index,

[0030] O b =P0 / He

[0031] Where 0 b : Highlight the risk index;

[0032] P0: surrounding rock gas pressure;

[0033] He: effective barrier thickness;

[0034] S502: Surrounding rock gas pressure P0 ≥ 0.5 MPa or outburst hazard index 0 b The area with a gas pressure of ≥0.05 is defined as the dangerous area of ​​surrounding rock gas outburst; the surrounding rock gas pressure P0 is less than 0.5MPa and 0 b The area with a value less than 0.05 is considered to be a relatively safe area for surrounding rock gas outburst.

[0035] In step S600, if one of the following situations occurs during coal tunneling on the gas geological map, it is determined that there is a risk of surrounding rock gas outburst:

[0036] ① Gas dynamic phenomenon or coal and gas outburst occur continuously in the same coal lane;

[0037] ② The prominent locations occur repeatedly during lane repair;

[0038] ③ During the outburst, the amount of gas ejected exceeds the gas content of the ejected coal by more than 2 times.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] First of all, the present invention realizes the innovation of theoretical basis, breaks through the theoretical basis that coal and gas outburst is caused by the coal seam itself, and is more suitable for the mechanism and truth of coal and gas outburst.

[0041] Secondly, the present invention achieves a breakthrough in the dimensional prediction from the coal seam to the coal-bearing strata. The prediction range is expanded from plane to three-dimensional, which is more in line with reality, and the scope of prevention and control is wider, more comprehensive and safer.

[0042] Third, this application predicts the outburst danger area, and determines it using two methods: outburst danger index and outburst phenomenon. Among them, the prediction of outburst danger index creatively proposes the surrounding rock gas pressure P0 outburst danger index 0b, which is more in line with the coal and gas outburst mechanism and more in line with the outburst mechanism than the previous simple coal seam outburst danger identification index (original coal seam gas pressure, coal solidity coefficient, coal gas destruction type, coal gas release initial velocity). BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0045] like Figure 1 As shown, an accurate method for predicting surrounding rock gas outburst includes the following steps:

[0046] S100: Based on the type of coal seam deposits mined in the mine, preliminarily determine the rock strata that may contain surrounding rock gas.

[0047] In step S100, the coal seam deposition types include: coal seam deposition types include source-reservoir-cap deposition, source-cap deposition and coal seam group deposition, wherein surrounding rock gas exists in source-reservoir-cap deposition.

[0048] At present, the mechanism of coal and gas outburst in the world is unclear. It is generally believed that gas is generated in coal seams, stored in coal seams, and outbursts in coal seams, which is self-generated and self-stored. Through theoretical deduction and establishment of outburst models, the gas geological zoning theory is creatively proposed and verified by practice. In the source-reservoir-cap sedimentary strata, gas is generated in coal seams and stored in coal-bearing strata (i.e. coal seams and surrounding rocks). The main cause of outburst is the participation of surrounding rock gas.

[0049] S200: Calculate the coal seam gas loss amount, and determine the maximum generation amount of surrounding rock gas in the rock strata that may contain surrounding rock gas in step S100 based on the coal seam gas loss amount.

[0050] In step S200, the gas loss of the mined coal seam is calculated by the following formula:

[0051] E=Gt-W

[0052] Where, E: coal seam gas loss, m 3 / t;

[0053] Gt: apparent gas generation rate, m 3 / t;

[0054] W: gas content per ton of coal m 3 / t.

[0055] Among them, the apparent gas occurrence rate is determined according to the type and rank of coal seams mined in the mine;

[0056] Gt=109.890Ro-21.978

[0057] Where Gt: apparent gas generation rate, m 3 / t;

[0058] Ro: measured vitrinite reflectance of coal type.

[0059] In step S200, the amount of coal seam gas loss refers to the amount of gas lost to the surrounding rock or the atmosphere. The amount of coal seam gas loss = the maximum amount of surrounding rock gas generated. It can be analyzed and determined that the gas is generated in the coal seam and stored in the coal-bearing strata. The large amount of surrounding rock gas is the prerequisite for surrounding rock gas outburst.

[0060] S300: Directional tracking of coal seam gas loss, analyzing whether the coal seam gas loss is completely lost to the atmosphere, or completely or partially enters the rock formation where surrounding rock gas may be stored, and obtaining the gas storage capacity in the rock formation where surrounding rock gas is stored;

[0061] In step S300: surrounding rock gas storage = maximum surrounding rock gas generation - coal seam gas loss to the atmosphere. The coal seam gas generation is much greater than the current coal seam gas content. After the generated gas reaches the coal seam gas content saturation, it escapes outward during the coal formation process, which is the coal seam gas loss. Part of the lost gas enters the surrounding rock and forms surrounding rock gas.

[0062] S400: Surrounding rock gas verification and parameter determination, drilling and exploration of rock formations that may have the risk of surrounding rock gas outburst, to determine whether there is surrounding rock gas, and to determine the gas reservoir that causes the outburst of the mined coal seam, and to determine the surrounding rock gas pressure, concentration, extraction flow rate and barrier layer thickness; surrounding rock gas pressure ≥ 0.5MPa, gas extraction flow rate ≥ 0.1 m 3 / min and the concentration is ≥30%, it is determined that surrounding rock gas exists; otherwise, it is considered that there is no outstanding danger of surrounding rock gas.

[0063] S500: Based on the surrounding rock gas parameters actually measured by S400, the surrounding rock gas outburst layer and surrounding rock gas parameters are determined, and then through gas geological analysis, the surrounding rock gas outburst danger area and the surrounding rock gas outburst relatively safe area are divided.

[0064] Step S500 includes:

[0065] S501: Calculate the protrusion hazard index,

[0066] O b =P0 / He

[0067] Where 0 b : Highlight the risk index;

[0068] P0: surrounding rock gas pressure;

[0069] He: effective barrier thickness;

[0070] S502: Surrounding rock gas pressure P0 ≥ 0.5 MPa or outburst hazard index 0 b The area with a gas pressure of ≥0.05 is defined as the dangerous area of ​​surrounding rock gas outburst; the surrounding rock gas pressure P0 is less than 0.5MPa and 0 b The area with a value less than 0.05 is considered to be a relatively safe area for surrounding rock gas outburst.

[0071] S600: Combined with the gas geological map, based on the gas outburst phenomenon during coal tunneling, directly determine whether there is a danger of gas outburst in the surrounding rock.

[0072] In step S600, if one of the following situations occurs during coal tunneling on the gas geological map, it can be directly predicted as a region with surrounding rock gas outburst:

[0073] ① There is gas dynamic phenomenon in the coal seam or coal and gas outbursts occur continuously in the same coal roadway;

[0074] ② Coal and gas outbursts occurred repeatedly during tunnel repair at the outburst site;

[0075] ③ During the outburst, the amount of gas ejected exceeds by more than 2 times the gas content of the ejected coal.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An accurate method for predicting surrounding rock gas outburst, characterized in that: include: S100: Based on the type of coal seam deposits mined in the mine, preliminarily determine the rock strata that may contain surrounding rock gas; S200: Calculate the coal seam gas loss amount, and determine the maximum generation amount of surrounding rock gas in the rock layer where surrounding rock gas may be stored in step S100 according to the coal seam gas loss amount; S300: Directional tracking of coal seam gas loss, analyzing whether the coal seam gas loss is completely lost to the atmosphere, or completely or partially enters the rock formation where surrounding rock gas may be stored, and obtaining the gas storage capacity in the rock formation where surrounding rock gas is stored; S400: Surrounding rock gas verification and parameter determination: drilling and exploring the rock formations that may have the danger of surrounding rock gas outburst, determining whether there is surrounding rock gas, and determining the surrounding rock gas parameters; S5 00: Based on the surrounding rock gas parameters actually measured by S400, the surrounding rock gas outburst layer and surrounding rock gas parameters are determined, and then the surrounding rock gas outburst dangerous area and the surrounding rock gas outburst relatively safe area are divided through gas geological analysis; S600: Combined with the gas geological map, based on the gas outburst phenomenon during coal tunneling, directly determine whether there is a danger of gas outburst in the surrounding rock.

2. The accurate surrounding rock gas outburst prediction method according to claim 1 is characterized in that: In the step S100, the coal seam deposition types include: coal seam deposition types include source-reservoir-cap deposition, source-cap deposition and coal seam group deposition, wherein surrounding rock gas exists in source-reservoir-cap deposition.

3. The accurate surrounding rock gas outburst prediction method according to claim 1 is characterized in that: In step S200, the gas loss of the mined coal seam is calculated by the following formula: E=Gt-W Where, E: coal seam gas loss, m 3 / t; Gt: apparent gas generation rate, m 3 / t; W: gas content per ton of coal m 3 / t.

4. The accurate surrounding rock gas outburst prediction method according to claim 3 is characterized in that: Determine the apparent gas occurrence rate based on the type and rank of coal seams mined in the mine; Gt=109.890Ro-21.978 Where Gt: apparent gas generation rate, m 3 / t; Ro: measured vitrinite reflectance of coal type.

5. The accurate surrounding rock gas outburst prediction method according to claim 1 or 4, characterized in that: In step S200, the coal seam gas loss amount refers to the amount of gas overflowing into the surrounding rock, and the coal seam gas loss amount = the maximum amount of surrounding rock gas generated.

6. The accurate surrounding rock gas outburst prediction method according to claim 1 is characterized in that: In the step S300: gas storage capacity = maximum generation of surrounding rock gas - coal seam gas loss.

7. The accurate surrounding rock gas outburst prediction method according to claim 1 is characterized in that: In step S400, the surrounding rock gas parameters include surrounding rock gas pressure, concentration, extraction flow rate and barrier layer thickness; surrounding rock gas pressure ≥ 0.5 MPa, gas extraction flow rate ≥ 0.1 m 3 / min and the concentration is ≥30%, it is determined that surrounding rock gas exists.

8. The accurate surrounding rock gas outburst prediction method according to claim 1 is characterized in that: The step S500 includes: S501: Calculate the protrusion hazard index, O b =P0 / He Where 0 b : Highlight the risk index; P0: surrounding rock gas pressure; He: effective barrier thickness; S502: Surrounding rock gas pressure P0 ≥ 0.5 MPa or outburst hazard index 0 b The area with a gas pressure of ≥0.05 is defined as the dangerous area of ​​surrounding rock gas outburst; the surrounding rock gas pressure P0 is less than 0.5MPa and 0 b The area with a value less than 0.05 is considered to be a relatively safe area for surrounding rock gas outburst.

9. The accurate surrounding rock gas outburst prediction method according to claim 1 is characterized in that: In step S600, if one of the following situations occurs during coal tunneling on the gas geological map, it is determined that there is a risk of surrounding rock gas outburst: ① Gas dynamic phenomenon or coal and gas outburst occur continuously in the same coal lane; ② The prominent locations occur repeatedly during lane repair; ③ During the outburst, the amount of gas ejected exceeds the gas content of the ejected coal by more than 2 times.

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