CN104695935A - Well drilling position selection method in consideration of coal seam crushing degree - Google Patents

Abstract

The invention discloses a well drilling position selection method in consideration of a coal seam crushing degree, and belongs to the field of coalbed methane drilling engineering. A bulk rock core is obtained from a coal seam drilling hole of a block to be drilled to determine rock type coefficients and geology strength indexes of coal rocks; the experimental sample processing is performed for the obtained bulk rock core to obtain multiple sets of standard cylinder coal rock core samples; the uniaxial compressive strength test is performed for the obtained multiple sets of coal rock cores by an uniaxial compressive strength tester, and the average value of multiple sets of test values serves as the uniaxial compressive strength of the coal rocks in the block to be drilled; a coal rock crushing coefficient formula is determined according to the Hoek-Brown criterion for evaluating the coal seam crushing degree; and a ground stress field of the coal seam in the bock to be drilled is determined according to a multiple linear regression method, and the maximal main stress value, the minimal main stress value, the uniaxial compressive strength and the rock body coefficient of each unit of the coal seam of the block to be drilled are substituted into the coal rock crushing coefficient formula to calculate the crushing coefficient of the coal seam of the block to be drilled.

Description

A kind of drilling well selection of conceal silo location method considering coal seam degree of crushing

Technical field:

The present invention relates to a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing, belong to CBM Drilling engineering field.

Background technology:

At present, the rule of CBM exploration and development well location layout: 1. coal bed gas resource evaluation; 2. favorable block is preferred; 3. well location is arranged.In above-mentioned steps, drilling well well location arranges the selection and the engineering experience that depend primarily on Enriching Coalbed Methane district.But, according to the data of CBM Drilling scene feedback, utilize the preferred drilling well well location of said method often to occur the drilling failure such as cave-in, bit freezing in drilling process.For this reason, in the urgent need to providing a kind of drilling well selection of conceal silo location method from the angle of prevention drilling well risk.

The existence in the anisotropy of coal petrography physico-mechanical properties and hugger, crack, destroys the integrality of coal petrography, makes coal petrography have breakable feature.This character of coal petrography determines in CBM Drilling process and drilling well risk very easily occurs.Meanwhile, field engineering experience also generally believes, coal seam degree of crushing is the key factor controlling drilling well risk.Therefore, finding a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing, is one of CBM Drilling engineering field problem in the urgent need to address.

Goal of the invention:

Main purpose of the present invention is the technical need for CBM Drilling selection of conceal silo location, sets up a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing.Compared with traditional CBM Drilling selection of conceal silo location method, consider that the drilling well selection of conceal silo location method of coal seam degree of crushing mainly contains following three aspect goals of the invention: (1), by predicting the degree of crushing in block object coal seam to be drilled, can make drilling well well location away from broken serious region, coal seam; (2) field engineering experience generally believes, coal seam degree of crushing is the key factor controlling drilling well risk.By drilling well well location being selected in more weak broken region and not broken region, the drilling well risk caused by coal seam fragmentation effectively can be reduced; (3) auxiliary conventional CBM Drilling selection of conceal silo location scheme, determines optimum drilling well well location position.

Summary of the invention:

For overcoming the defect of prior art, the object of the present invention is to provide a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing, reducing the drilling well risk caused by coal seam fragmentation, the auxiliary selection of conceal silo location problem solved in CBM Drilling engineering field.

For achieving the above object, technical scheme of the present invention is as follows:

1, a drilling well selection of conceal silo location method for coal seam degree of crushing is considered, containing following steps

(1), from block object coal bed drilling to be drilled obtain bulk rock core, determine rock type coefficient and the Geological stength index of coal petrography;

(2), to the bulk rock core obtained experimental sample processing is carried out, obtained many group standard cylinder coal rock core test piece;

(3), adopt uniaxial compressive test machine to carry out uniaxial compressive strength test to obtained many groups coal petrography heart, will the coal petrography uniaxial compressive strength of average as block to be drilled of test value be organized more;

(4), according to Hoek-Brown rule definition coal petrography fragmentation factor formula, in order to evaluate coal seam degree of crushing;

(5), determine according to multiple linear regression analysis method the stress field in block object coal seam to be drilled to obtain the major principal stress value of each unit in block object coal seam to be drilled, minimum principal stress value;

(6), by the major principal stress value of each unit in block object coal seam to be drilled, minimum principal stress value, uniaxial compressive strength, rock mass coefficient substitutes into coal petrography fragmentation factor formula, calculates the fragmentation factor in block object coal seam to be drilled;

(7), according to the field experience of coal seam drilling, the corresponding relation of different degree of crushing region, object coal seam and CBM Drilling selection of conceal silo location is set up;

(8), according to different degree of crushing region, the block object coal seam to be drilled divided, coal bed gas straight well drilling well well location is selected.

The invention has the beneficial effects as follows: by predicting the degree of crushing in block object coal seam to be drilled, propose a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing, the present invention is adopted to select drilling well well location effectively can avoid the comparatively serious region of coal seam degree of crushing, the effect serve to a certain extent and prevent cave-in, reducing drilling well risk.

Accompanying drawing illustrates:

Fig. 1 is the schematic flow sheet of the drilling well selection of conceal silo location method of consideration coal seam of the present invention degree of crushing;

Fig. 2 is the horizontal major principal stress isogram in a certain coal seam;

Fig. 3 is the horizontal minimum principal stress isogram in a certain coal seam;

Fig. 4 is a certain coal seam fragmentation factor isogram;

Fig. 5 is the different degree of crushing Region dividing in a certain coal seam and optimum drilling well well location map.

Detailed description of the invention:

As shown in Figure 1, a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing, step is as follows:

(1), from block object coal bed drilling to be drilled obtain bulk rock core, determine rock type Coefficient m i and the geological strength index GSI of coal petrography;

Rock type coefficient 1 (this table derives from monograph " practical rock mass engineering project technology " book of Canadian Evert Hoek, the 139th page) of can tabling look-up obtains.

Table 1

Rock mass geology intensity index 2 (this figure derives from monograph " practical rock mass engineering project technology " book of Canadian Evert Hoek, the 145th page) of can tabling look-up obtain.

Table 2

(2), to the bulk rock core obtained carry out experimental sample processing, obtained many group standard cylinder coal rock core test piece, standard cylinder coal petrography heart height of specimen is 50mm (± 1mm), and diameter is 25mm (± 0.5mm);

(3), adopt uniaxial compressive test machine to carry out uniaxial compressive strength test to obtained many groups coal petrography heart, will the coal petrography uniaxial compressive strength σ of average as block to be drilled of test value be organized more _ci;

(4), according to Hoek-Brown criterion (Hoek-Brown) coal petrography fragmentation factor ξ is defined, in order to evaluate coal seam degree of crushing:

$\mathrm{\ξ}=\frac{{\mathrm{\σ}}_1}{{\mathrm{\σ}}_3+{\mathrm{\σ}}_{\mathrm{ci}}{(m_b\frac{{\mathrm{\σ}}_3}{{\mathrm{\σ}}_{\mathrm{ci}}}+s)}^{\mathrm{\α}}}---\left(1\right)$

$m_b=m_i\exp \left(\frac{\mathrm{GSI}-100}{28-14D}\right)s=\exp \left(\frac{\mathrm{GSI}-100}{9-3D}\right)\mathrm{\α}=\frac{1}{2}+\frac{1}{6}(e^{-\mathrm{GSI}/15}-e^{-20/3})$

(2)

In formula: σ ₁, σ ₃be respectively maximum, the minimum principal stress suffered by coal petrography, MPa; σ _cifor coal petrography uniaxial compressive strength, MPa; m _bfor rock mass coefficient, with rock type Coefficient m _irelevant, without unit; S, α are rock mass coefficient, without unit; D is rock mass Discontinuous Factors, and disturbance is taken as 0, is undisturbed and is taken as 1;

(5), determine according to multiple linear regression analysis method the stress field in block object coal seam to be drilled to obtain the major principal stress value σ of each unit in block object coal seam to be drilled ₁, minimum principal stress value σ ₃

Concrete steps comprise:

1., multiple linear regression equations is defined:

${\mathrm{\α}}_k=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{L}_i{\mathrm{\σ}}_{\mathrm{ik}}---\left(3\right)$

In formula, σ _kfor the stress regression calculated value of corresponding observation point k, σ _k=[σ _xkσ _ykσ _zkτ _xykτ _yzkτ _zxk] ^t; I=1 ... n is corresponding different operating mode respectively; σ _ikfor the stress FEM (finite element) calculation value of corresponding i operating mode k observation point, σ _ik=[σ _ixkσ _iykσ _izkτ _ixykτ _iyzkτ _izxk] ^t; L _ifor regression coefficient undetermined;

2., suppose there is m observation point, calculate the residual sum of squares (RSS) S of least square method _residual:

In formula: for the observation of the k observation point j stress components; for the FEM (finite element) calculation value of the k observation point j stress components under i operating mode;

According to principle of least square method, residual sum of squares (RSS) S _residualwhen reaching minimum value, should meet:

$\left|\begin{array}{cccc}\underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\left({\mathrm{\σ}}_{\mathrm{jk}}^1\right)}^2& \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^1{\mathrm{\σ}}_{\mathrm{jk}}^1& \·\·\·& \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^1{\mathrm{\σ}}_{\mathrm{jk}}^n\\ & \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\left({\mathrm{\σ}}_{\mathrm{jk}}^2\right)}^2& \·\·\·& \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^2{\mathrm{\σ}}_{\mathrm{jk}}^n\\ & \·\·\·& & \·\·\·\\ & & & \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\left({\mathrm{\σ}}_{\mathrm{jk}}^n\right)}^2\end{array}\right|\left|\begin{array}{c}{L}_1\\ L_2\\ \·\·\·\\ L_n\end{array}\right|=\left|\begin{array}{c}\underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^{*}{\mathrm{\σ}}_{\mathrm{jk}}^1\\ \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^{*}{\mathrm{\σ}}_{\mathrm{jk}}^2\\ \·\·\·\\ \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^{*}{\mathrm{\σ}}_{\mathrm{jk}}^n\end{array}\right|$

3., solving equation obtains n regression coefficient L=(L undetermined ₁, L ₂..., L _n) ^t, then the geostatic stress of any unit P in object coal seam can be obtained by following formula superposition:

${\mathrm{\σ}}_{\mathrm{jP}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{L}_i{\mathrm{\σ}}_{\mathrm{jP}}^i$

In formula, j=(1,2 ..., 6) ^tfor the purpose of 6 components of any unit geostatic stress in coal seam;

(6), by the major principal stress value σ of each unit in block object coal seam to be drilled ₁, minimum principal stress value σ ₃, uniaxial compressive strength σ _ci, rock mass Coefficient m _b, s, α substitute into coal petrography fragmentation factor formula (1), calculate the fragmentation factor in block object coal seam to be drilled.

According to coal petrography fragmentation factor, coal seam is divided into fracture area (I), comparatively forcing crushing district (II), more weak fracture area (III), non-fracture area (IV).Wherein, the corresponding relation of coal seam degree of crushing and fragmentation factor is in table 3;

Table 3

(7), according to the field experience of coal seam drilling, the corresponding relation of different degree of crushing region, object coal seam and CBM Drilling selection of conceal silo location is described as:

1. fracture area (I): forbid in this region to select drilling well well location;

2. comparatively forcing crushing district (II): do not advise in this region selecting drilling well well location, if drilling well well location need be selected strictly should to control drilling parameter;

3. more weak fracture area (III): drilling well well location can be selected in this region, and suitably can relax drilling parameter;

4. non-fracture area (IV): in this region, pay the utmost attention to drilling well well location;

(8), according to different degree of crushing region, the block object coal seam to be drilled divided, by coal bed gas straight well drilling well selection of conceal silo location in non-fracture area (IV), more weak fragmentation (III) region, and the position that prioritizing selection coal seam fragmentation factor is minimum;

According to different degree of crushing region, the block object coal seam to be drilled divided, coal bed gas horizontal well and lateral wellbore track thereof are selected in non-fracture area (IV), more weak fragmentation (III) region, and the well track that position, coal seam, prioritizing selection well track place fragmentation factor average is minimum.

Embodiment one

The drilling well selection of conceal silo location method considering coal seam degree of crushing is further illustrated for a certain block CBM Drilling selection of conceal silo location.

(1), from certain coal bed drilling get bulk rock core, determined the rock type Coefficient m i=15 of coal petrography by 1 rock type coefficient of tabling look-up (this figure derives from monograph " practical rock mass engineering project technology " book of Canadian Evert Hoek, the 139th page).With reference to the rock mass geology intensity index (this figure derives from monograph " practical rock mass engineering project technology " book of Canadian Evert Hoek, the 145th page) of table 2, determine geological strength index GSI=55 of coal petrography;

(2), to the coal seam bulk rock core obtained carry out experimental sample processing, obtained 20 groups of standard cylinder coal rock core test piece, standard cylinder coal petrography heart height of specimen is 50mm (± 1mm), and diameter is 25mm (± 0.5mm);

(3), uniaxial compressive test machine is adopted to carry out uniaxial compressive strength test to obtained 20 groups of coal petrography hearts, using the coal petrography uniaxial compressive strength σ of the average of 20 groups of test values as block to be drilled _ci=25MPa;

(4) coal petrography fragmentation factor ξ is defined according to Hoek-Brown criterion (Hoek-Brown), in order to evaluate coal seam degree of crushing;

(5) determine object coal seam stress field, obtain coal seam each unit major principal stress value σ ₁, minimum principal stress value σ ₃, as shown in Figure 2 and Figure 3;

(6) by major principal stress σ ₁, minimum principal stress σ ₃, coal petrography uniaxial compressive strength σ _ci, rock mass Coefficient m _b, s, α substitute into coal petrography fragmentation factor formula (1) and calculate fragmentation factor, divides different degree of crushing region, coal seam, as shown in Figure 4;

(7) corresponding relation of different degree of crushing region, object coal seam and CBM Drilling selection of conceal silo location is set up;

(8) different degree of crushing regions, object coal seam and optimum drilling well well location is determined, as shown in Figure 5.

As mentioned above, embodiments of the invention are explained, but as long as do not depart from inventive point of the present invention in fact and effect can have a lot of distortion, this will be readily apparent to persons skilled in the art.Therefore, such variation is also all included within protection scope of the present invention.

Claims (7)

1. consider a drilling well selection of conceal silo location method for coal seam degree of crushing, it is characterized in that step is as follows:

Step (1), obtain rock core from block object coal bed drilling to be drilled, determine rock type coefficient and the Geological stength index of coal petrography;

Step (2), experimental sample processing is carried out to the rock core obtained, much more obtained group standard cylinder coal rock core test piece;

Step (3), employing uniaxial compressive test machine carry out uniaxial compressive strength test to obtained many groups coal petrography heart, will organize the coal petrography uniaxial compressive strength of average as block to be drilled of test value more

Step (4), according to Hoek-Brown rule definition coal petrography fragmentation factor formula, in order to evaluate coal seam degree of crushing;

Step (5), determine according to multiple linear regression analysis method the stress field in block object coal seam to be drilled to obtain the major principal stress value of each unit in block object coal seam to be drilled, minimum principal stress value;

Step (6), by the major principal stress value of each unit in block object coal seam to be drilled, minimum principal stress value, uniaxial compressive strength, rock mass coefficient substitutes into coal petrography fragmentation factor formula, calculates the fragmentation factor in block object coal seam to be drilled;

Step (7), field experience according to coal seam drilling, set up the corresponding relation of different degree of crushing region, object coal seam and CBM Drilling selection of conceal silo location;

Step (8), according to different degree of crushing region, the block object coal seam to be drilled divided, select coal bed gas straight well drilling well well location.

2. a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing according to claim 1, it is characterized in that, standard cylinder coal petrography heart height of specimen is 50mm, error ± 1mm; Diameter is 25mm, error ± 0.5mm.

3. a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing according to claim 1 and 2, it is characterized in that, core experiment number of sets of sample is for being no less than 20 groups.

4. a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing according to claim 3, is characterized in that, the corresponding relation of different degree of crushing region, coal seam and CBM Drilling selection of conceal silo location is:

1. fracture area: forbid in this region to select drilling well well location;

2. comparatively forcing crushing district: do not advise in this region selecting drilling well well location, if drilling well well location need be selected strictly should to control drilling parameter;

3. more weak fracture area: drilling well well location can be selected in this region, and suitably can relax drilling parameter;

4. non-fracture area: pay the utmost attention to drilling well well location in this region.

5. a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing according to claim 1 or 4, is characterized in that, coal bed gas horizontal well and lateral wellbore track thereof are selected in non-fracture area, more weak broken region.

6. a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing according to claim 5, is characterized in that, the well track that position, coal seam, prioritizing selection well track place fragmentation factor average is minimum.

7. a kind of drilling well selection of conceal silo location method considering coal seam degree of crushing according to claim 1,2,4 or 6, is characterized in that concrete steps comprise:

1., multiple linear regression equations is defined:

${\mathrm{\σ}}_k=\underset{i=l}{\overset{n}{\mathrm{\Σ}}}{L}_i{\mathrm{\σ}}_{\mathrm{ik}}$

In formula, σ _kfor the stress regression calculated value of corresponding observation point k, σ _k=[σ _xkσ _ykσ _zkτ _xykτ _yzkτ _zxk] ^t; I=1 ... n is corresponding different operating mode respectively; σ _ikfor the stress FEM (finite element) calculation value of corresponding i operating mode k observation point, σ _ik=[σ _ixkσ _iykσ _izkτ _ixykτ _iyzkτ _izxk] ^t; L _ifor regression coefficient undetermined;

2. the residual sum of squares (RSS) S of least square method, is calculated _residual:

In formula: for the observation of the k observation point j stress components; for the FEM (finite element) calculation value of the k observation point j stress components under i operating mode; M observation point number;

According to principle of least square method, residual sum of squares (RSS) S _residualwhen reaching minimum value, should meet:

$\left|\begin{array}{cccc}\underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\left({\mathrm{\σ}}_{\mathrm{jk}}^1\right)}^2& \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^1{\mathrm{\σ}}_{\mathrm{jk}}^1& \·\·\·& \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^1{\mathrm{\σ}}_{\mathrm{jk}}^n\\ & \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\left({\mathrm{\σ}}_{\mathrm{jk}}^2\right)}^2& \·\·\·& \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^2{\mathrm{\σ}}_{\mathrm{jk}}^n\\ & \·\·\·& & \·\·\·\\ & & & \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\left({\mathrm{\σ}}_{\mathrm{jk}}^n\right)}^2\end{array}\right|\left|\begin{array}{c}{L}_1\\ L_2\\ \·\·\·\\ L_n\end{array}\right|=\left|\begin{array}{c}\underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^{*}{\mathrm{\σ}}_{\mathrm{jk}}^1\\ \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^{*}{\mathrm{\σ}}_{\mathrm{jk}}^2\\ \·\·\·\\ \underset{k=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{6}{\mathrm{\Σ}}}{\mathrm{\σ}}_{\mathrm{jk}}^{*}{\mathrm{\σ}}_{\mathrm{jk}}^n\end{array}\right|$

3., solving equation obtains n regression coefficient L=(L undetermined ₁, L ₂..., L _n) ^t, then the geostatic stress of any unit P in object coal seam can be obtained by following formula superposition:

${\mathrm{\σ}}_{\mathrm{jP}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{L}_i{\mathrm{\σ}}_{\mathrm{jP}}^i$

In formula, j=(1,2 ..., 6) ^tfor the purpose of 6 components of any unit geostatic stress in coal seam.