CN103411868B - A kind of method of testing of Permeability Coefficent in Coal Seam - Google Patents

A kind of method of testing of Permeability Coefficent in Coal Seam Download PDF

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CN103411868B
CN103411868B CN201310317597.8A CN201310317597A CN103411868B CN 103411868 B CN103411868 B CN 103411868B CN 201310317597 A CN201310317597 A CN 201310317597A CN 103411868 B CN103411868 B CN 103411868B
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gas
coal seam
coal
pressure
boring
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CN103411868A (en
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宋超
邓增社
陈通
王鹏
薛卫峰
赵泓超
徐文全
司俊鸿
王小军
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Shaanxi Coal and Chemical Technology Institute Co Ltd
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Abstract

The invention discloses a kind of method of testing of Permeability Coefficent in Coal Seam, comprise the steps: to keep at a certain distance away the boring of two same depth and construct in vertical coal seam, and record spacing of wells d; Obtain the absolute gas pressure P in coal seam; Tracer gas is injected in a boring wherein, and it is connected with air compressor, and provide certain pressure to it, another boring is connected with gas drainage system line seal; Detect tracer gas, and determine that this boring is from being connected to gas drainage system pipeline to tracer gas time t used being detected; Computing formula test result being updated to Permeability Coefficent in Coal Seam tries to achieve Permeability Coefficent in Coal Seam; Computation process is simple, provides certain gas injection pressure by compressor, and to be connected with gas drainage system pipeline in another boring and to make aperture keep negative pressure, and can obtain tracer gas by Quick Measuring, test period is short, and general applicability is strong.

Description

A kind of method of testing of Permeability Coefficent in Coal Seam
Technical field
The present invention relates to control of coalmine gas technical field, particularly relate to a kind of method of testing of Permeability Coefficent in Coal Seam.
Background technology
China is not only at present maximum in the world coal production state, and is maximum consumption of coal state, for a long time, coal in Chinese primary energy production and consumption structure proportion always more than 2/3rds.Along with the increase of the pit mining degree of depth and the rising of terrestrial stress, the outburst hazard in coal seam is increased day by day, China has become the most serious country of global coal and gas prominent accident, and the number of times of coal and gas prominent and intensity also all reach the first in the world.Gas pumping is effective control gas accident, the guardian technique means solving China's coal-mine Safety production questions.And Permeability Coefficent in Coal Seam is the mark of coal seam coal gas dynamics complexity, it is the important parameter evaluating coal bed gas extraction complexity and gas outburst prevention treatment; Permeability Coefficent in Coal Seam is foundation and the basis of gas pumping design.Therefore, accurately test Permeability Coefficent in Coal Seam plays vital effect in the gas pumping work of mine.
Current China mainly adopts boring redial flow method test Permeability Coefficent in Coal Seam.But this method of testing needs to cross repeatedly tentative calculation at one group of formula back warp when calculating permeability coefficient just can find suitable computing formula, brings inconvenience to calculating.Simultaneously theoretical analysis also shows, existing computing method also also exist and cannot find suitable computing formula or there is the problems such as two conflicting result of calculations.And first boring redial flow method needs the original gas pressure in Accurate Determining coal seam, then tests each moment drilling gas flow; Its test period is longer, and for the less coal seam of coal-bed gas pressure, coal-bed gas pressure and drilling gas flow are often difficult to Accurate Determining, and thus its applicability also receives certain restriction.
Summary of the invention
The object of the invention is the defect overcoming prior art, provide a kind of calculate simple, test period is short, can the method for testing of Permeability Coefficent in Coal Seam of Measurement accuracy.
For achieving the above object, the present invention is by the following technical solutions:
A method of testing for Permeability Coefficent in Coal Seam, comprises the steps:
(1) comparatively intact in coal seam, without tomography, place without shatter belt, keep at a certain distance away the boring of two same depth and construct in vertical coal seam, and record spacing of wells d;
(2) the absolute gas pressure P in coal seam is obtained;
(3) tracer gas is injected in a boring wherein, and is connected with this borehole sealing by air compressor, the pressure P that air compressor provides ythe absolute gas pressure P in coal seam that step (2) obtains should be greater than; Another boring is connected with gas drainage system line seal, and measures this drilling orifice negative pressure P c;
(4) tracer gas is detected, until tracer gas detected in the drilling orifice place be connected with gas pumping system every day; And determine that this boring is from being connected to gas drainage system pipeline to tracer gas time t used being detected;
(5) calculate Permeability Coefficent in Coal Seam λ, specifically comprise the steps:
1) measure the percolation flow velocity of tracer gas in coal seam, calculating formula is as follows:
v = d t
The percolation flow velocity of v-tracer gas in coal seam in formula, m/d;
D-spacing of wells, m;
T-tracer gas the time used detected, d;
2) calculate Permeability Coefficent in Coal Seam, computation process is as follows:
From Darcy's law:
v = - k μ ∂ p ∂ x
K-permeability in formula, m 2;
μ-coefficient of dynamic viscosity, Pas;
The definition of Permeability Coefficent in Coal Seam is had again to be:
λ = - Bk 2 μ P n
λ-Permeability Coefficent in Coal Seam in formula, m 2/ (MPa 2d);
B-unit conversion factor;
P n-normal atmospheric pressure, MPa;
By above-mentioned two formula simultaneous and the computing formula that integration can obtain Permeability Coefficent in Coal Seam be:
λ = Bvd 2 P n ( P Y - P C )
P in formula ythe pressure that-air compressor provides, MPa;
P c-drilling orifice extraction negative pressure, MPa.
Described step 2) in obtain coal seam absolute gas pressure P concrete steps and be:
1) after drilling construction puts in place, measure coal seam gas-bearing capacity, and the technical analysis that samples of coal pulled carries out coal obtains porosity and the unit weight of the moisture of coal, ash content and coal, and the gas-absorbent constant a of coal, b value;
2) the absolute gas pressure in inverse coal seam, circular is: by the gas-absorbent constant a of gas bearing capacity, technical analysis result and coal recorded, and b value substitutes into following computation model and carries out computing, tries to achieve the absolute gas pressure P in coal seam:
W = abP 1 + bP · 100 - A d - M ad 100 · 1 1 + 0.31 M ad + 10 πP γ
The absolute gas pressure in P-coal seam in formula, MPa;
W-coal seam gas-bearing capacity, m 3/ t;
The gas-absorbent constant of a, b-coal;
A d-pit ash, %;
M adthe moisture of-coal, %;
The porosity of π-coal, m 3/ m 3:
The unit weight of γ-coal, t/m 3.
Choose the maximal value of the absolute gas bearing capacity in coal seam of acquisition as the calculated value in later step.
Be connected to the boring of gas drainage system pipeline, connecting pipe should be provided with threeway and valve at aperture place, for measuring aperture negative pressure and carrying out trace gas detection.
Described tracer gas is SF 6tracer gas.
The invention provides a kind of simple method for testing bacterial resistance of Permeability Coefficent in Coal Seam, construct the boring of two same depth in vertical coal seam, obtain the absolute gas pressure in coal seam, tracer gas is injected in a boring, tracer gas is detected, by detecting that tracer gas time used and the spacing of wells calculate drilling gas flow, in conjunction with the definition of Permeability Coefficent in Coal Seam from another hole, the computing formula obtaining Permeability Coefficent in Coal Seam tries to achieve Permeability Coefficent in Coal Seam, and computation process is simple; There is provided certain pressure by compressor, and to be connected with gas drainage system pipeline in another boring and to make aperture keep negative pressure, can obtain tracer gas by Quick Measuring, test period is short, and general applicability is strong.
Further, by the gas-absorbent constant a of gas bearing capacity, technical analysis result and coal recorded, b substitutes into computation model and carries out computing, inverse tries to achieve the absolute gas pressure in coal seam, by the spacing of wells and detect that the tracer gas time used tries to achieve drilling gas flow, finally try to achieve Permeability Coefficent in Coal Seam; Solve traditional coal seam permeability coefficient method of testing present low gas coal-bed gas pressure, drilling gas flow is difficult to the problems such as Accurate Determining, test process is simple.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of test macro of the present invention;
In figure: 1-injecting hole; 2-extraction detect aperture; 3-coal seam; 4-air compressor; 5-tensimeter; 6-connecting hose; 7-ring flange; 8-stop valve; 9-gas drainage system pipeline; The d-spacing of wells.
Embodiment
Below in conjunction with the drawings and specific embodiments, the invention will be further described.
See Fig. 1, in the present embodiment, on coal seam 3, d separated by a distance constructs two and holes, one is injecting hole 1, one is extraction detect aperture 2, injecting hole 1 is connected to air compressor 4 by connecting hose 6, connected by ring flange 7 between the two, the pressure that air compressor 4 provides is observed by tensimeter 5; Extraction detect aperture 2 is connected to gas drainage system pipeline 9 by connecting hose, connected by ring flange 7 between the two, also connected by ring flange between gas drainage system pipeline, and be negative pressure in gas drainage system pipeline, the gas in extraction detect aperture 2 can be extracted; Connecting hose between extraction detect aperture 2 and gas drainage system pipeline 9 is provided with gas detect mouth, and installs stop valve 8, is in closed condition when stop valve 8 is flat, opens stop valve 8 and detect when need carry out gas detect.
The Permeability Coefficent in Coal Seam method of testing of the present embodiment, comprises the steps:
(1) comparatively intact in coal seam, without tomography, place without shatter belt, the boring of and construct in vertical coal seam two same depth of keeping at a certain distance away, is respectively injecting hole 1 and extraction detect aperture 2, and records spacing of wells d.
(2) after drilling construction puts in place, carry out gas bearing capacity test job, and samples of coal pulled carries out the technical analysis of coal and the gas-absorbent constant a of coal, b value; Two borings survey gas bearing capacity and get maximal value as the calculated value in later step; Wherein the technical analysis of coal mainly comprises porosity and the unit weight of the moisture of coal, ash content, volatile matter and coal.
(3) inverse coal-bed gas pressure, circular is: by the gas-absorbent constant a of gas bearing capacity, technical analysis result and coal recorded, and b value substitutes into following computation model and carries out computing, tries to achieve coal-bed gas pressure P:
W = abP 1 + bP · 100 - A d - M ad 100 · 1 1 + 0.31 M ad + 10 πP γ
The absolute gas pressure in P-coal seam in formula, MPa;
W-coal seam gas-bearing capacity, m 3/ t;
The gas-absorbent constant of a, b-coal;
A d-pit ash, %;
M adthe moisture of-coal, %;
The porosity of π-coal, m 3/ m 3:
The unit weight of γ-coal, t/m 3.
(4) in two borings of constructing complete, insert the sealing of hole sleeve pipe of certain length, and carry out airtight shutoff between the wall of a borehole and sleeve pipe, prevent gas leakage.
(5) in injecting hole 1, a certain amount of SF is injected 6tracer gas, and air compressor 4 is connected with injecting hole 1, the pressure P that air compressor provides ythe coal-bed gas pressure P being greater than step 3 inverse should be ensured, P ysize is observed by tensimeter 5; Extraction detect aperture 2 is connected with gas drainage system pipeline 9, and measures aperture negative pressure P c.All utilize connecting hose 6 to connect between each linkage section, connected by ring flange 7 between each pipeline.
(6) SF is detected in stop valve 8 place every day 6tracer gas, until detect SF 6tracer gas; And determine that this boring is from being connected to gas drainage system pipeline 9 to SF being detected 6tracer gas time t used.
(7) calculate Permeability Coefficent in Coal Seam λ, specifically comprise the steps:
1) SF is measured 6the percolation flow velocity of tracer gas in coal seam, calculating formula is as follows:
v = d t
V-SF in formula 6the percolation flow velocity of tracer gas in coal seam, m/d;
D-spacing of wells, m;
T-SF detected 6the tracer gas time used, d.
2) calculate Permeability Coefficent in Coal Seam, computation process is as follows:
From Darcy's law:
v = - k μ ∂ p ∂ x
K-permeability in formula, m 2;
μ-coefficient of dynamic viscosity, Pas;
The definition of Permeability Coefficent in Coal Seam is had again to be:
λ = - Bk 2 μ P n
λ-Permeability Coefficent in Coal Seam in formula, m 2/ (MPa 2d);
B-unit conversion factor;
P n-normal atmospheric pressure, MPa;
By above-mentioned two formula simultaneous and the computing formula that integration can obtain Permeability Coefficent in Coal Seam be:
λ = Bvd 2 P n ( P Y - P C )
P in formula ythe pressure that-air compressor provides, MPa;
P c-drilling orifice extraction negative pressure, MPa.
The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, obviously, those skilled in the art can carry out various change and modification to the present invention and not depart from the spirit and scope of the present invention.Like this, if these amendments of the present invention and modification belong within the scope of claim of the present invention and equivalent technologies thereof, then the present invention is also intended to comprise these change and modification.

Claims (4)

1. a method of testing for Permeability Coefficent in Coal Seam, is characterized in that comprising the steps:
(1) comparatively intact in coal seam, without tomography, place without shatter belt, keep at a certain distance away the boring of two same depth and construct in vertical coal seam, and record spacing of wells d;
(2) the absolute gas pressure P in coal seam is obtained;
Obtaining the absolute gas pressure P concrete steps in coal seam is:
1) after drilling construction puts in place, measure coal seam gas-bearing capacity, and the technical analysis that samples of coal pulled carries out coal obtains porosity and the unit weight of the moisture of coal, ash content and coal, and the gas-absorbent constant a of coal, b value;
2) the absolute gas pressure in inverse coal seam, circular is: by the gas-absorbent constant a of gas bearing capacity, technical analysis result and coal recorded, and b value substitutes into following computation model and carries out computing, tries to achieve the absolute gas pressure P in coal seam:
W = a b P 1 + b P · 100 - A d - M a d 100 · 1 1 + 0.31 M a d + 10 π P γ
The absolute gas pressure in P-coal seam in formula, MPa;
W-coal seam gas-bearing capacity, m 3/ t;
The gas-absorbent constant of a, b-coal;
A d-pit ash, %;
M adthe moisture of-coal, %;
The porosity of π-coal, m 3/ m 3:
The unit weight of γ-coal, t/m 3;
(3) tracer gas is injected in a boring wherein, and is connected with this borehole sealing by air compressor, the pressure P that air compressor provides ythe absolute gas pressure P in coal seam that step (2) obtains should be greater than; Another boring is connected with gas drainage system line seal, and measures this drilling orifice negative pressure P c;
(4) tracer gas is detected, until tracer gas detected in the drilling orifice place be connected with gas drainage system pipeline every day; And determine that this boring is from being connected to gas drainage system pipeline to tracer gas time t used being detected;
(5) calculate Permeability Coefficent in Coal Seam λ, specifically comprise the steps:
1) measure the percolation flow velocity of tracer gas in coal seam, calculating formula is as follows:
v = d t
The percolation flow velocity of v-tracer gas in coal seam in formula, m/d;
D-spacing of wells, m;
T-tracer gas the time used detected, d;
2) calculate Permeability Coefficent in Coal Seam, computation process is as follows:
From Darcy's law:
v = - k μ ∂ p ∂ x
K-permeability in formula, m 2;
μ-coefficient of dynamic viscosity, Pas;
The definition of Permeability Coefficent in Coal Seam is had again to be:
λ = - B k 2 μP n
λ-Permeability Coefficent in Coal Seam in formula, m 2/ (MPa 2d);
B-unit conversion factor;
P n-normal atmospheric pressure, MPa;
By above-mentioned two formula simultaneous and the computing formula that integration can obtain Permeability Coefficent in Coal Seam be:
λ = B v d 2 P n ( P Y - P C )
P in formula ythe pressure that-air compressor provides, MPa;
P c-drilling orifice extraction negative pressure, MPa.
2. the method for testing of Permeability Coefficent in Coal Seam according to claim 1, is characterized in that: choose the maximal value of the absolute gas bearing capacity in coal seam of acquisition as the calculated value in later step.
3. the method for testing of Permeability Coefficent in Coal Seam according to claim 1, is characterized in that: the boring being connected to gas drainage system pipeline, and connecting pipe should be provided with threeway and valve at aperture place, for measuring aperture negative pressure and carrying out trace gas detection.
4. the method for testing of Permeability Coefficent in Coal Seam according to claim 1, is characterized in that: described tracer gas is SF 6tracer gas.
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