CN102102514A - Technology for determining coal bed intensity by using coal ash - Google Patents

Abstract

The invention relates to a technology for determining coal bed intensity by using coal ash, which is suitable for the technical field of well wall stabilization in well drilling for coal bed methane. The method comprises the following steps of: classifying, cleaning, baking and crushing coal rock debris obtained by logging, performing proximate analysis of coal according to the national standard, and determining the ratio of ash to volatile; judging the coal grade of the coal rock according to the volatile value; selecting the corresponding empirical formula of the relationship between the ash and the intensity according to the coal grade and calculating the intensity of coal rock blocks; and solving the coal reservoir intensity by combining a geological strength index (GSI) value and applying a Hoek-Brown rock mass strength empirical formula. The method is provided by combining the field on the basis of the Hoek-Brown rock mass strength empirical formula, and is suitable for the requirement for acquiring the parameters of the coal bed intensity in the well wall stabilization prediction of well drilling for the coal bed methane, and the prediction method is simple and has a good effect.

Description

Coal ash is determined coal seam intensity technology

Technical field

The present invention relates to the wellbore stability technical field in the coal bed gas drilling well, be specifically related to coal ash and determine coalbed methane reservoir intensity technology.

Background technology

Coal is a kind of extremely inhomogeneous organic rock that is transformed into by plant remains, has two groups in the coal petrography usually and is bordering on vertical hugger, and hugger is in the different times of coal-forming, the phenomenon of splitting that cause in the coal seam under the various natural force effects.Main fracture set face cleat is grown more perfect, and extension can reach hundreds of rice, and end hugger group is grown between face cleat, has linked up face cleat.Except that hugger, also often grow in the coal seam cracks such as joint, secondary joint.The mutual cross-cut in these cracks has formed complicated fissure system.Because the effect of hugger and joint fissure, coal body is cut into the fritter of discontinuous approximate trapezoid body one by one, has destroyed the integrality in coal seam.

Since the particularity of coal bed texture, the growth in various cracks in the coal petrography, and cause its mechanical property to have: discontinuity, non-homogeneity, anisotropy and permeability---Study in Stability of Borehole Wall is complicated unusually.The coal seam mechanical strength is low, and crack and hugger are grown, and homogenieity is poor, has the effect of higher shear stress.Thereby the coal seam section borehole wall is extremely unstable, cave-in, leakage and bit freezing very easily takes place in drilling process even bury down-hole accident such as well.

From the mechanics angle, the special tectonic in coal seam can be summed up in the point that two aspects, the one, the stress that borehole wall coal petrography is subjected to, the 2nd, the intensity of coal petrography to the influence of borehole collapse.Borehole wall stability studies just that well Zhou Yanshi state is whether stable still to be destroyed, and the prediction of coal seam intensity is the key technology that solves coal bed gas drilling stability evaluation problem.The domestic and international at present prediction in coal seam intensity mostly is the prediction of strength after the artificial geological conditions generaI investigation about coal mine roadway borehole wall crack, but the core difficulty is got in coal bed gas drilling well coal seam, the prediction of strength of this method incompatibility coal seam drilling well.The coal seam intensity The Application of Technology of determining coal ash can realize carrying out real-time estimate to boring the coal seam intensity of meeting.

Summary of the invention

The purpose of this invention is to provide in the coal bed gas drilling process the prediction while drilling method of coal seam intensity, utilize this method can predict the intensity of coalbed methane reservoir simple, convenient, fast, prediction effect is good.

Utilize above-mentioned purpose, the present invention adopts following technical scheme:

Coal ash is determined coal seam reservoirs intensity technology, and this The Application of Technology method comprises step:

(1) volatile matter that obtains coal petrography, grey divided data are tested in Industrial Analysis according to coal petrography;

(2) judge that according to volatile matter this well bores the coal rank of meeting under coal seam;

(3) according to the empirical formula of coal rank selection coal petrography ash content and intensity, substitution ash divided data is asked for coal petrography sillar intensity;

(4) in conjunction with the GSI value, use Hoek-Brown intensity empirical formula, then get the coal output layer rock mass strength.

Wherein, the Industrial Analysis method (GB/T212-2008) of National Standard coal is adopted in the coal petrography Industrial Analysis ".

Wherein, the criteria for classifying of coal rank is seen National Standard Chinese Coal Classification national standard (GB5751-86) ".

Wherein, coal petrography ash content and intensity empirical formula are in this method:

${\mathrm{\σ}}_{\mathrm{ci}}=\mathrm{AF}{C}_{\mathrm{ad}}^2-{\mathrm{BFC}}_{\mathrm{ad}}+C---\left(1\right)$

In the formula, σ _Ci---coal petrography sillar uniaxial compressive strength; FC _Ad---coal petrography content of ashes percentage, %; A, B, C---empirical coefficient by the coal rank decision, can be measured by laboratory experiment.

Wherein, Hoek-Brown intensity empirical formula is in this method:

${\mathrm{\σ}}_1^{\′}={\mathrm{\σ}}_3^{\′}+{\mathrm{\σ}}_{\mathrm{ci}}{(m_b\frac{{\mathrm{\σ}}_3^{\′}}{{\mathrm{\σ}}_{\mathrm{ci}}}+s)}^a---\left(2\right)$

In the formula, $m_b=m_i\exp \left(\frac{\mathrm{GSI}-100}{28-14D}\right)$

$s=\exp \left(\frac{\mathrm{GSI}-100}{9-3D}\right)$

$a=\frac{1}{2}+\frac{1}{6}(e^{-\mathrm{GSI}/15}-e^{-20/3})$

D is explosion or the stress release coefficient to the rock mass level of disruption.When the value of this value never is subjected to disturbance 0 is 1 during to maximum perturbation, and concrete numerical value please refer to " HOEK-BROWN FAILURE CRITERION-2002 EDITION ".With σ ' ₃=0 substitution formula (2) can obtain the uniaxial compressive strength σ of coal petrography rock mass _CmassFor:

σ _cmass＝σ _cis ^a (3)

For complete coal and rock, s=1 is for damaged coal and rock, s＜1 are arranged.

Coal seam provided by the invention prediction of strength technology, be suitable in the coal bed gas drilling process prediction to coal seam intensity, also be fit to simultaneously in the coal mining prediction to coal seam intensity, this method is the new method that proposes in conjunction with on-the-spot practical application effect on rock mechanics parameter laboratory experiment based measurement, through the on-site actual situations check, has good effect.

Description of drawings

Fig. 1 determines the flow chart of coal seam intensity technology for coal ash point-score of the present invention.

The specific embodiment

The coal ash that the present invention proposes is determined the method for coal seam intensity, is described as follows in conjunction with the accompanying drawings and embodiments.

Because the particularity of coal bed texture, the growth in various cracks in the coal petrography, cause its mechanical property to have: discontinuity, non-homogeneity, anisotropy and permeability, make that the coal seam mechanical strength is low, crack and hugger are grown, and homogenieity is poor, the drilling extracting core difficulty, and core is difficult to process code test coal core after being subjected to stress release, mechanical disturbance, dehydration.Cause the serious distortion of indoor intensity result of the test.

The domestic and international at present prediction in coal seam intensity mostly is the prediction of strength after the artificial geological conditions generaI investigation about coal mine roadway borehole wall crack, but the core difficulty is got in coal bed gas drilling well coal seam, the prediction of strength of this method incompatibility coal seam drilling well.The coal seam intensity The Application of Technology of determining coal ash can realize carrying out real-time estimate to boring the coal seam intensity of meeting.

Coal petrography sillar strength determining method of the present invention by the landwaste that returns in the coal seam drilling well of collecting, is cleaned, oven dry, pulverize after, according to the Industrial Analysis method (GB/T212-2008) of National Standard coal " after the burning, measure ash content, the volatilization score value of coal petrography bits.Consult " Chinese Coal Classification national standard (GB5751-86) " and determine that this well bores the landwaste coal rank of meeting the coal seam.According to the empirical formula of coal rank selection coal petrography ash content and intensity, substitution ash divided data is asked for coal petrography sillar intensity;

Described coal petrography ash content and intensity empirical formula are:

${\mathrm{\σ}}_{\mathrm{ci}}=\mathrm{AF}{C}_{\mathrm{ad}}^2-{\mathrm{BFC}}_{\mathrm{ad}}+C---\left(1\right)$

In the formula, σ _Ci---coal petrography sillar uniaxial compressive strength; FC _Ad---coal petrography content of ashes percentage, %; A, B, C---empirical coefficient by the coal rank decision, can be measured by laboratory experiment.

After described GSI value was the borehole wall crack spread image of taking by under-mine TV or photo, the Geological Strength Index that corresponding Hock-Brown provides determined that the coal and rock quality consults coal petrography GSI value.

Definite method of described coal seam intensity is determined by the empirical formula that provides in " HOEK-BROWN FAILURE CRITERION-2002EDITION ".

Wherein, Hoek-Brown intensity empirical formula is in this method:

${\mathrm{\σ}}_1^{\′}={\mathrm{\σ}}_3^{\′}+{\mathrm{\σ}}_{\mathrm{ci}}{(m_b\frac{{\mathrm{\σ}}_3^{\′}}{{\mathrm{\σ}}_{\mathrm{ci}}}+s)}^a---\left(2\right)$

In the formula, $m_b=m_i\exp \left(\frac{\mathrm{GSI}-100}{28-14D}\right)$

$s=\exp \left(\frac{\mathrm{GSI}-100}{9-3D}\right)$

$a=\frac{1}{2}+\frac{1}{6}(e^{-\mathrm{GSI}/15}-e^{-20/3})$

D is explosion or the stress release coefficient to the rock mass level of disruption.When the value of this value never is subjected to disturbance 0 is 1 during to maximum perturbation.

With σ ' ₃=0 substitution formula (2) can obtain the uniaxial compressive strength σ of coal petrography rock mass _CmassFor:

σ _cmass＝σ _cis ^a (3)

For complete coal and rock, s=1 is for damaged coal and rock, s＜1 are arranged.

Above embodiment only is used to illustrate the present invention; and be not limitation of the present invention; the those of ordinary skill in relevant technologies field; under the situation that does not break away from the spirit and scope of the present invention; can also make various variations and modification; therefore all technical schemes that are equal to also belong to category of the present invention, and scope of patent protection of the present invention should be defined by the claims.

Claims (5)

1. coal ash is determined coal seam intensity technology, it is characterized in that, this method may further comprise the steps:

The volatile matter that obtains coal petrography, grey divided data are tested in Industrial Analysis according to coal petrography;

Judge that according to volatile matter content this well bores the coal rank of meeting under coal seam;

According to the empirical formula of coal rank selection coal petrography ash content and intensity, substitution ash divided data is asked for coal petrography sillar intensity;

In conjunction with the GSI value, use Hoek-Brown intensity empirical formula, then get the coal output layer rock mass strength.

2. coal ash as claimed in claim 1 is determined coal seam intensity technology, it is characterized in that, the intensity of obtaining the coal seam in this method is that the landwaste that returns in the coal bed gas drilling well is carried out Industrial Analysis prediction coal petrography sillar intensity, thereby determine indirectly.

3. coal ash as claimed in claim 1 or 2 is determined coal seam intensity technology, it is characterized in that the Industrial Analysis method (GB/T212-2008) of determining to be based on the National Standard coal of the ash content of coal petrography landwaste, volatile matter in this method " carry out.Coal rank is divided and is based on National Standard Chinese Coal Classification national standard (GB5751-86) in this method " determine.

4. coal ash as claimed in claim 1 is determined coal seam intensity technology, it is characterized in that, this method coal petrography sillar intensity determine to be based on the result who adds up after a large amount of laboratory tests, its empirical formula fitting degree is higher.Obtain described coal petrography ash content and intensity by formula (1):

In the formula, σ _Ci---coal petrography sillar uniaxial compressive strength; FC _Ad---coal petrography content of ashes percentage, %; A, B, C---empirical coefficient by the coal rank decision, can be measured by laboratory experiment.

5. coal ash as claimed in claim 1 is determined coal seam intensity technology, it is characterized in that, the determining of this method coal seam intensity is based on Hoek-Brown intensity empirical formula (2), determined that by sillar the method for rock mass calculates:

In the formula,

D is explosion or the stress release coefficient to the rock mass level of disruption.When the value of this value never is subjected to disturbance 0 is 1 during to maximum perturbation, and concrete numerical value please refer to " HOEK-BROWN FAILURE CRITERION-2002EDITION ".

With σ ' ₃=0 substitution formula (2) can obtain the uniaxial compressive strength σ of coal petrography rock mass _CmassFor:

σ _cmass＝σ _cis ^a (3)?。

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