CN110533349B - Coal seam gas content calculation and error analysis method - Google Patents
Coal seam gas content calculation and error analysis method Download PDFInfo
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Abstract
The invention discloses a coal seam gas content calculation method and an error analysis method, wherein the calculation method comprises the following steps: s1 determining an in situ desorption equation V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )‑V 1 Solution (II) S2, desorbing the coal core, and fitting an S3 equation; the error analysis method comprises error analysis of residual desorption amount and error analysis of total gas content. The invention provides a field desorption equation and combines a specific field gas desorption process to calculate the total gas content, the gas loss amount and the residual desorption amount of a deep coal bed; the relative error of the gas content is reduced; meanwhile, a corresponding error analysis method is provided to assist the on-site desorption equation to calculate the gas content more accurately, so that the accuracy and the reliability of the deep coal seam gas content calculation are improved, and the objective evaluation on the deep gas content and the occurrence geological conditions is further facilitated.
Description
Technical Field
The invention belongs to the technical field of coal seam gas content measurement, and particularly relates to a deep coal seam gas content calculation and error analysis method.
Background
The coal bed gas content is one of the main parameters of the coal bed gas and is an important basic parameter necessary for coal and coal bed gas exploration and development.
The gas content of the coal seam in the geological exploration period consists of four parts: gas loss (V) 1 ) Gas desorptionQuantity (V) 2 ) Vacuum heating degassing volume (V) before grinding 3 ) And the amount of deaerated gas (V) after pulverization 4 ). The sum of the amount of degassing gas before crushing and the amount of degassing gas after crushing may also be referred to as a gas residual amount. The gas desorption amount is measured by a field desorption tank, the gas residual amount is measured by a laboratory, and the gas loss amount is mainly calculated by the field desorption rule of the coal core.
At present, the method for calculating the gas content of the coal bed in the period of domestic geological exploration mainly comprises
Methods (graphical and analytical methods): accumulated desorption quantity V and/or accumulated desorption quantity is determined according to the exposure time t of the coal core of the drill hole>
The determination is made in a linear relationship. Connecting and extending the connecting lines of all points which are in a linear relation within a period of time and intersecting with a vertical coordinate, wherein the intercept of the straight line on the vertical axis is the required gas loss amount; or the gas loss amount can be obtained by the least square method based on the coordinate values of these points. For the graphical method, the
Plotting all the measuring points on coordinate paper as an abscissa, connecting all the points which are in a linear relation within a period of time and begin to desorb, and prolonging the connection with an ordinate axis; the intercept of the straight line on the vertical axis is the required gas loss. For the analytical method, V and @, since the coal sample begins to be exposed for a period of time>
In a linear relationship, i.e. </or>
Wherein a and b are constant numbers, when->
When V = a, the value of a is the determined gas loss.
The deep coal seam is influenced by a high ground stress field, a temperature field and a fluid pressure field, and the occurrence of geological conditions is complex. Compared with the conventional shallow coal seam, when deep coal seam products are collected, the gas dissipation time in the drill lifting process is advanced, and the conventional gas content testing method does not consider the dissipation amount of the free gas when calculating the dissipation gas amount, so that the testing result is lower. The literature reports that: when the buried depth of the coal seam is less than 500m, 70% of measured values are lower by 15-25%, and 20% of measured values are higher by 10-15%; when the buried depth of the coal seam is more than 500m (particularly close to 800 m), the measured value generally tends to be lower and increase along with the increase of the hole depth, 85% of the measured values are lower by 30-40%, the highest value is more than 50%, and only 8% of the measured values are higher by 5-10%. As shown in FIG. 2, related researches show that the calculated value of the method for the deep coal seam is small, and the objective evaluation effect of the deep gas content and the occurrence geological conditions is restricted due to certain errors of the obtained gas content value and the real content of the deep gas.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a method for calculating the gas content of a coal seam and analyzing errors.
The invention solves the technical problems through the following technical means:
a coal seam gas content calculation method comprises the following steps:
s1, determining an on-site desorption equation:
V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 solution (II)
Wherein A is the upper limit gas desorption total amount of the coal core desorption, B is the coefficient related to the gas adsorption speed and the heat of adsorption, V 1 Solution (II) For the amount of gas lost, V, to solve 2 Cumulative amount of desorbed gas, T 0 ＝t 0 +t，t 0 ＝1/2t 1 +t 2 ，
V 3 Solution (II) ＝A-V 1 Solution (II) -V 2 ，V 3 Solution (II) Calculating a value for the residual desorption;
s2, desorbing the coal core: the drill hole is made of slurry medium or clear water medium, and when the coal core of the drill hole is lifted to the half depth of the hole opening, the initial desorption time of the coal core is used. Desorbing the coal core to be lifted on site, and recording the time t of lifting the drill during the desorption 1 Time t for filling 2 Recording the desorption time t in the desorption tank and the accumulated gas desorption amount V along with the time t at the same time 2 ；
And (3) fitting an S3 equation: the gas accumulated desorption amount V of the coal core sample along with the time 2 Projected in a coordinate system, and subjected to fitting of a field desorption equation to determine A and V 1 Solution (II) A is the calculated value of the total coal bed gas content, V 1 Solution (II) The calculated value of the gas loss of the coal bed is obtained.
Further, in order to realize accurate calculation of gas content based on-site measured data, residual desorption amount V obtained by degassing before crushing and degassing after crushing in a laboratory is calculated 3 Fruit of Chinese wolfberry The accumulated desorption amount was plotted on a graph paper as a part thereof, and the equation was subjected to correction fitting.
Furthermore, the on-site desorption equation is simultaneously suitable for the on-site desorption data of the gas in different desorption speeds, different accumulated desorption durations, different observation time intervals and the like.
Further, data correction is carried out by using single-point correction or double-point correction;
the single-point correction method comprises the following steps:
(1) Establishing coordinates
Projected on a piece of coordinate paper, wherein V 3 Vacuum heating degassing amount before pulverizing, V 4 For the amount of degassing after comminution, V 3 +V 4 Continuously desorbing in a desorption tank with time, and corresponding to a desorption time t i ；
(2) Using formula V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) To coordinate point
Performing repeated fitting optimization to ensure that the coordinate point is greater or less>
Satisfies formula V as accurately as possible 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) The extension trend of the curve;
(3) Finally obtaining the desorption time coordinate of the optimal fitting result, obtaining the A, B parameter value of the fitting equation and the V under the condition 1 Solution (II) ，V 1 Solution (II) The calculated gas loss is obtained;
the double-point correction method comprises the following steps:
(1) Establishing coordinates
And &>
Projected on a graph paper, where V 3 Vacuum heating degassing amount before pulverizing, V 4 In order to remove air moisture after shredding>
Corresponds to V 3 Considered as a component of the cumulative desorption amount, the corresponding analysis time is t i-1 In conjunction with>
Corresponds to V 3 +V 4 Considered as a component of the cumulative desorption amount, the corresponding analysis time is t i ；
(2) Using formula V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) To coordinate point
And
performing repeated fitting optimization to make the coordinate point->
And &>
Satisfies formula V as accurately as possible 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) The extension trend of the curve;
(3) Finally obtaining the desorption time coordinate of the optimal fitting result, and obtaining the A, B parameter value of the fitting equation and the V under the condition 1 Solution (II) ，V 1 Solution (II) The calculated gas loss is obtained;
further, the gas desorption to V can be calculated 2 And V 3 +V 4 The theoretical observation time interval corresponding to time is t Δ ＝t i -t. At this time, t is the maximum cumulative desorption amount V 2 Corresponding cumulative desorption observation time.
The invention also provides an error analysis method for coal seam gas content calculation, which comprises the error analysis of residual desorption amount and the error analysis of total gas content;
wherein the error analysis equation of the residual desorption amount is as follows:
RE＝100％×(V 3 solution (II) -V 3 Fruit of Chinese wolfberry )/V 3 Fruit of Chinese wolfberry ；
The error analysis equation of the total gas content is as follows:
R＝100％×(A-V general assembly Solution (II) )/V General assembly Solution (II) Wherein V is General assembly Solution (II) ＝V 1 Solution (II) +V 2 +V 3 Fruit of Chinese wolfberry 。
Further, gas loss error analysis at different drilling lifting time is also included;
wherein, the gas loss error analysis equation of different drilling time is:
RE＝100％×[V 0 (t 1 ’)-V 0 (t 1 )]/V 0 (t 1 )；
V 0 (t 1 ) Drill lifting time t for minimum simulation 1 ' amount of coal bed gas lost, i.e. actual field desorption true exposure time t 1 According to the field desorption equation V under the condition 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) Obtained V 1 Solution (II) A value of (d);
V 0 (t 1 ') simulation drilling time point t for simulation drilling 1 At time, the exposure time t can be determined 1 The loss amount of coal bed gas;
wherein, V 0 (t 1 ’)＝V 1 ’(t 1 ’)-V 0 ’(t 1 ’)；
In the formula, V 0 ’(t 1 ') simulated drill lifting time t 1 The actual desorbed gas amount at time;
V 1 ’(t 1 ') simulated drill lifting time t 1 The gas loss at time, from the in situ desorption equation V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) According to the simulated drill lifting time t 1 ' solving;
T 0 ’＝t 0 ’+t，T 0 ' Total desorption time;
t 0 ’＝1/2t 1 ’+t 2 t 0 ' calculated loss time, t, designed for simulation of coal core samples 2 The canning time;
t 1 ’＝t 1 +2×T 0 ，t 1 ' to simulate the time from the lifting of the coal core to the arrival at the surface of the earth, T 0 Is at t 1 ' time the core of coal under conditions has been desorbed in the desorption tank.
Further, the method also comprises the analysis of the loss amount and the upper limit desorption amount relative errors caused by different desorption time points;
wherein, the analysis equation of loss amount relative error caused by different amount desorption time points is as follows:
RE V ＝100％×(V 1 k -V 1 n )/V 1 n ；
wherein, the analysis equation of the upper limit desorption amount relative error caused by different amounts of desorption time points is as follows:
RE A ＝100％×(A k -A n )/A n ；
in the formula, V 1 k And A k Respectively corresponding to desorption time points t n The gas loss amount and the upper limit desorption amount of (b); are all according to equation V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) Fitting to obtain n as an observation time point, wherein n =1,2,3,4 and … …; corresponding to an accumulated observation time t n (ii) a k is a calculation time point, k =1,2,3,4, … … n, and k is not more than n;
V 1 n and A n The gas loss and the upper limit desorption, i.e. t, at the observation point of the longest time n Take the value at the maximum.
Further, different desorption time points t are included n Analyzing the relative error of the accumulated gas desorption amount;
wherein the different desorption time points t n The analysis equation of the accumulated gas desorption amount relative error is as follows:
RE＝100％×(V 2 n ’-V 2 n )/V 2 n ；
in the formula, V 2 n For different quantities desorption time points t n Corresponding cumulative gas desorption, V, of the actual test 2 n Is a point of time t n Corresponding fitting cumulative gas desorption, V 2 n ' Desorption from site equation V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) Found by fitting, V 2 n ' that is, V 2 ，n＝1，2，3，4……。
Further, an error analysis equation of the residual desorption amount, an error analysis equation of the total gas content, an error analysis equation of gas loss amounts at different drilling raising times, an analysis equation of loss amount relative errors caused by different desorption time points, an analysis equation of upper limit desorption amount relative errors caused by different desorption time points, and t n The time accumulated gas desorption amount relative error analysis equation can be used for field gas desorption data in different modes and error analysis of gas loss amount calculation methods such as a linear method, a logarithmic method, a polynomial method, a power function method, an Amoco method and the like.
The beneficial effects of the invention are as follows: the invention provides an on-site desorption equation and combines a specific on-site gas desorption process to calculate the total gas content, the gas loss amount and the residual desorption amount of a deep coal bed; the relative error of the gas content is reduced; meanwhile, a corresponding error analysis method is provided to assist the field desorption equation to calculate the gas content more accurately, so that the accuracy and the reliability of the calculation of the gas content of the deep coal seam are improved, and the objective evaluation of the deep gas content and the occurrence geological conditions is further facilitated.
Drawings
FIG. 1 shows desorption data for examples 1 and 2;
FIG. 2 shows a conventional method
Fitting calculation results of the method;
FIG. 3 is a schematic representation of the method using equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) Fitting the calculation result;
FIG. 4 is a schematic representation of the method using equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) Fitting and correcting the calculation result by using a single point;
FIG. 5 shows the equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) Fitting and using the calculation result of the double-point correction;
FIG. 6 is desorption data corresponding to examples 3 to 6;
FIG. 7 is a graph showing the relative error in gas loss amounts obtained by simulating different drilling times in example 4;
FIG. 8 is a graph showing the gas loss V at different observation points n for the desorption time in example 5 1 k And upper limit desorption amount A k Relative error of (2);
FIG. 9 shows different desorption time points t in example 6 n The accumulated gas desorption amount relative error is calculated;
FIG. 10 is a comparison of the relative error in gas loss obtained in example 6 according to the calculation method employed herein and other commonly employed methods, simulating different pull-out times.
Detailed Description
In order to make the objects, 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 with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
This example combines the experimental data of gas field desorption to equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) For explanation and explanation.
And (3) desorbing experimental data on a gas field, wherein the desorption time is 120min generally. The acquisition of time interval points generally complies with GB/T23249-2009 method for measuring coal bed gas content in geological prospecting period. The specific method comprises the following steps: the observation time is continuously 120min. The reading interval is specified as follows: reading every 2-5 min after 1-2 min from the first point to the third point within 60min before observation; the reading is carried out once every 10min-20min in the second hour. In addition, AQ 1046-2007 method for measuring gas content of coal bed in geological exploration period regulates reading interval time as follows: continuously observing for 120 min; reading every 3-5min after the first point is spaced for 2min within 60min before observation; the readings are taken every 10-20min during the second hour.
The volume data of the desorption amount of gas used in this example and the examples described later are volume data under the standard conditions corrected.
With V 2 As a vertical coordinate, with
For the abscissa, all the measured points are projected on a piece of coordinate paper, using equation V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) Correction is performed and V is read from the curve fitting equation 1 Solution (II) Values, corresponding experimental data are detailed in fig. 1, and corresponding fitting results are shown in fig. 3; in addition, the same experimental data are used with +>
The fitting results corresponding to the method are shown in fig. 2.
In FIG. 1, the data of the field desorption of the gas loss are shown, and the unit of the measured value and the fitting value in FIG. 1 is mL.
In conjunction with FIGS. 2 and 3, conventional techniques are used
Method and equation V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) The fitting method gives gas losses of 516mL and 1213mL, respectively, which are conventional->
The method results in a lower result, and equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) The fitting distorts the result.
Example 2
To is directed atIn the examples, equation V is used 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) And (3) performing related calculation of gas analysis amount, wherein although the method can perform relatively accurate fitting on the on-site gas content, according to national and industrial standards, the on-site gas desorption time in the geological exploration period is generally 120 minutes. When the method is applied to 120-minute gas desorption data on site, distortion of a fitting curve and distortion of a calculation result can be caused, so that the calculated gas loss amount is inconsistent with the actual gas loss amount. Therefore, the method needs further optimization and improvement, improves the calculation accuracy of the gas content, and is convenient for field application.
Combining the experimental data of FIG. 1 in example 1, as V 2 As a vertical coordinate, with
And projecting all the measuring points on coordinate paper for an abscissa. Degassing a laboratory before crushing and degassing after crushing to obtain a residual desorption amount V 3 +V 4 Plotting part of the accumulated desorption amount on a piece of coordinate paper by using an equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) Correction is performed and V is read from the curve fitting equation 1 Solution (II) The values, corresponding to the fitting results, are shown in fig. 4. The gas loss obtained by the single-point correction fitting method is 794mL.
Combining the experimental data of FIG. 1 in example 1, as V 2 As a vertical coordinate, with
And projecting all the measuring points on coordinate paper for an abscissa. Degassing a laboratory before crushing and degassing after crushing to obtain a residual desorption amount V 3 And V 3 +V 4 Respectively, as a part of the accumulated desorption amount, and is plotted on a piece of coordinate paper by using an equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) Correction is performed and V is read from the curve fitting equation 1 Solution (II) Value, corresponding fitting junctionThe result is shown in FIG. 5. The gas loss obtained by adopting a double-point correction fitting method is 790mL.
Combining the embodiment 1 and the embodiment 2, the calculation result of the gas analysis amount obtained by adopting the single-point correction method and the double-point correction method is more fit with the actual gas desorption process, and the equation V is eliminated 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) And the distortion of the fitting curve and the distortion of the calculation result are corrected, and the method is more suitable for field 120-minute gas desorption data and more beneficial to calculation of gas desorption amount.
Example 3
For the convenience of relative error analysis, the embodiment adopts another data sample with more data points as the relative error solution of the residual desorption amount and the relative error solution of the upper limit desorption amount of the embodiment. Detailed data are shown in FIG. 6, which corresponds to a fit result of
V 2 ＝2524.1×0.04×T 0 1/2 /(1+0.04×T 0 1/2 )-315.5
Solving the relative error of the residual desorption amount: RE =100% × (V) 3 Solution (II) -V 3 Fruit of Chinese wolfberry )/V 3 Fruit of Chinese wolfberry ；
For gas field desorption data, a =2524.1ml 2 =489.7mL (actual desorption observed time is integrated 2280min from actual desorption data read, assuming desorption observed time is 120min complete, then V 2 Cumulative on-site gas desorption for 120min time), V 1 Solution (II) =315.5mL (read from fitting equation);
then V 3 Solution (II) ＝A-V 1 Solution (II) -V 2 ＝2524.1-315.5-489.7＝1718.9mL；
The sum of the total gas desorption amount after 120min and the laboratory degassing desorption amount is regarded as the actual desorption amount V 3 Apparent nature Then, there are:
V 3 apparent nature ＝V After 120min Solution (II) +V 3 Fruit of Chinese wolfberry ＝980.45+1072.2＝2052.6mL；
RE =100% × (V) 3 Solution (II) -V 3 Apparent nature )/V 3 Apparent nature ＝100％×(1718.9-2052.6)/2052.6＝16.3％。
Solving the relative error of the upper limit desorption amount: r =100% × (A-V) General assembly Solution (II) )/V General assembly Solution (II) Wherein V is General assembly Solution (II) ＝V 1 Solution (II) +V 2 +V 3 Fruit of Chinese wolfberry ，V 1 Solution (II) From equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) Read out, V 2 Obtained by field desorption experiment of a desorption tank, and obtained by degassing and desorption in a laboratory 3 Fruit of Chinese wolfberry ；
For the experimental data of desorption in the gas field, the following are included:
V 3 apparent nature ＝V After 120min Solution (II) +V 3 Fruit of Chinese wolfberry ＝980.45+1072.15＝2052.6mL
V General assembly Solution (II) ＝V 1 Solution (II) +V 2 +V 3 Apparent nature ＝315.5+489.7+2052.6＝2857.8mL
R＝100％×(A-V General assembly Solution (II) )/V General assembly Solution (II) ＝100％×(2524.1-2857.8)/2857.8＝-11.68％
Example 4
In order to facilitate the analysis of relative error, the present embodiment uses another data sample with more data points as the desorption experimental data of the present embodiment, and the equation V is calculated 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) The gas quantity error analysis is carried out and the method is verified, and the detailed data are shown in figure 6; the gas loss error analysis method for simulating different drilling time comprises the following steps:
1) As with the graphical method and the analytical method, the drilling hole is a slurry medium or a clean water medium under the specified working condition, and the initial desorption time of the coal core is when the coal core of the drilling hole is lifted to the half depth of the hole opening.
2) Let t 1 ' to simulate the time to reach the surface of the coal core (i.e. drilling)Analog Total Exposure time, t 1 ’≥t 1 )，T 0 Is at t 1 ' the time when the coal core under the condition is desorbed in the desorption tank is t 1 ' to the real drill lifting time t 1 And 2 times of the time that the coal core has been desorbed in the desorption tank, namely:
t 1 ’＝t 1 +2×T 0
3) Then the calculated loss amount time t of the core sample simulation design for the hypothetical analysis of simulated different total exposure times in the borehole 0 Equal to half the simulated total exposure time in the borehole and the can filling time t 2 (coal core reaches surface to loading into desorption tank):
t 0 ’＝1/2t 1 ’+t 2
4) The total desorption time T 0 ' is a time t of analog loss 0 The sum of the' observation time t for desorbing the coal core sample in the desorption tank is as follows:
T 0 ’＝t 0 ’+t
5) When the simulated drill lifting time of the drill hole is t 1 Time, coal bed gas simulation loss V 1 ’(t 1 ') is:
V 1 ’(t 1 ’)＝V 0 (t 1 ’)+V 0 ’(t 1 ’)
in the formula: v 0 (t 1 ') simulation drilling time point t for simulation drilling 1 At time, the exposure time t can be determined 1 Amount of coal bed gas loss, V 0 ’(t 1 ') simulated drill lifting time t 1 Actual amount of desorbed gas at time
V 1 ’(t 1 ') simulated drill lifting time t 1 The gas loss at time from the in situ desorption equation V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) According to the simulated drill lifting time t 1 ' solving.
6) When simulating drill lifting time t 1 ' to the real drill lifting time t 1 When, V 0 (t 1 ’)＝V 1 ’(t 1 ’)；
7) When simulating drill lifting time t 1 ’>t 1 When, V 0 (t 1 ’)＝V 1 ’(t 1 ’)-V 0 ’(t 1 ’)；
8) Drill lifting time t for different simulations 1 ', all can adopt the equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) Calculating different simulated drill lifting time points t 1 Gas loss at time V 1 ’(t 1 ') and further determining the exposure time t 1 Coal bed gas loss V 0 (t 1 ’)；
9) Defining a minimum simulated drill lifting time t 1 ' (in this case, the real drill lifting time t is 1 ) Coal bed gas loss V 0 (t 1 ) Simulating the gas loss V of other drilling lifting time designed as true value 0 (t 1 ') is observed. The real exposure time t of the simulated borehole can be calculated 1 And (3) performing mapping analysis on the relative error of the gas loss amount, wherein the Relative Error (RE) is calculated by the following formula:
RE＝100％×[V 0 (t 1 ’)-V 0 (t 1 )]/V 0 (t 1 )；
10 FIG. 7 is a schematic representation using equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) Obtaining gas loss and relative error at different simulation drilling lifting time; FIG. 3 is a schematic representation of the method using equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) The obtained relative error of the gas loss amount obtained by simulating different drilling lifting time is shown in the attached drawing in detail in the content of the figure 3.
Simulation drill lifting time t 1 ' is a dynamic value, which can vary; the value thereof may be set to 22min (i.e., the actual drill-up time t) according to circumstances as in fig. 7 1 )、30min、62min、112min、162min、222min。
Example 5
The present embodiment is directed toIn example 2, the residual desorption amount V obtained by degassing before pulverization and degassing after pulverization in the laboratory was used 3 +V 4 For desorption tank gas desorption amount V 2 Correcting, adopting equation V due to uncertainty of desorption time length of gas field 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) When fitting solution is carried out on desorption data, the fitting result is inconsistent due to different numbers of desorption points, and therefore errors exist in loss obtained through calculation. For the convenience of relative error analysis, the data sample in fig. 6 with a large number of data points is used as an example in the present embodiment to provide a method for analyzing the loss amount relative error caused by different desorption time points in example 2 as follows:
(1) If n observation time points are provided, the accumulated observation time is t n ，n＝1，2，3，4，……n。
(2) Total desorption time T of coal sample 0 Calculated exposure time t for the purpose before filling 0 And the desorption observation time t after canning n Sum, i.e. T 0 ＝t 0 +t n 。
(3) Adopting numerical program software (or Excel fitting, programming and the like) to observe the time point t n Cumulative gas desorption amount of (V) 2 n Using equation V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) Fitting to obtain different desorption time points t n Corresponding gas loss V 1 n And upper limit desorption amount A n 。
(4) Respectively setting the gas loss amount and the upper limit desorption amount of the observation point with the longest time as V 1 n And A n The actual value is the gas loss V of the observation point n at different desorption times 1 k And upper limit desorption amount A k The Relative Error (RE) of (k =1,2,3,4, … … n) can be found by the following equation:
RE V ＝100％×(V 1 k -V 1 n )/V 1 n
RE A ＝100％×(A k -A n )/A n
(5) FIG. 8 is a graph of gas desorption experimental data for different number of desorption time points t n Cumulative gas desorption amount of V 2 n By the formula V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) Fitting and obtaining the gas loss V of observation points n at different desorption times 1 k And upper limit desorption amount A k (k =1,2,3,4, … … n).
Example 6
This example provides a residual desorption V for the laboratory degassing before comminution and degassing after comminution as in example 1 3 +V 4 For desorption tank gas desorption amount V 2 Make a correction of V 2 ＝AB T 0 1/2 /(1+B T 0 1/2 )-V 1 Solution (II) Fitting the change rule of the square root of the true gas desorption amount along with the time to obtain the fitted gas desorption amount and carrying out error analysis. For the purpose of relative error analysis, the data sample in fig. 6 with a large number of data points is used as the analysis object in the present embodiment.
For different amounts of desorption time t n Cumulative gas desorption V of the actual test 2 n Setting its corresponding time point t n Fitting cumulative gas desorption amount of V 2 n ', then different desorption time points t can be obtained n The accumulated gas desorption amount is relatively wrong. The expression is as follows:
RE＝100％×(V 2 n ’-V 2 n )/V 2 n
aiming at gas fine desorption experimental data, at different desorption time points t n The cumulative gas desorption amount relative error in time is shown in fig. 9.
It should be noted that the gas content calculation method mentioned herein can be applied not only to the determination of the gas content in the coal core in the geological exploration drilling of the coal bed, but also to the determination of the gas content in the coal core sample in the exploration of coal and coal bed gas.
It should be noted that the related error analysis method mentioned herein can not only perform error analysis on the gas loss calculation method provided herein, but also can be applied to the gas desorption data and the gas desorption data of the coal core sample in coal and coal bed gas exploration
And performing error analysis by using a method, a logarithm method, a polynomial method, amoco and other common gas loss calculation methods at home and abroad.
Fig. 10 is a comparison of the relative error in gas loss obtained by simulating different drill-up times, as determined according to the calculation method employed herein and other commonly employed methods.
Particularly, the gas desorption points are long in time and many in points, so that the time points of individual intervals can be prolonged, shortened, lacked or deleted, but the influence on the calculation effect is not large.
In summary, combining example 1 and example 2, the present invention proposes an in situ desorption equation V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) The total gas content, the gas loss amount and the residual desorption amount of the deep coal bed can be calculated by combining a specific field analysis process; the calculation results of the examples 1 and 2 are subjected to error analysis by combining the examples 3-6, and the results of error analysis data show that the in-situ desorption equation V provided by the invention 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) The error of the calculation result is smaller, and the error is smaller and tends to be stable along with the increase of the desorption time point quantity and the observation time point, so that the accurate calculation of the coal seam gas content is facilitated, particularly the deep coal seam gas, and the objective evaluation of the deep coal seam gas content and the occurrence geological conditions is further facilitated.
It should be noted that, in this document, if there are first and second, etc., relational terms are only used for distinguishing one entity or operation from another entity or operation, and there is no necessarily any requirement or suggestion that any actual relation or order exists between the entities or operations. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or apparatus that comprises the element.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A coal seam gas content calculation method is characterized by comprising the following steps:
s1, determining an on-site desorption equation:
V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 solution (II)
Wherein A is the upper limit gas desorption total amount of the coal core desorption, B is the coefficient related to the gas adsorption speed and the heat of adsorption, V 1 Solution (II) Is the loss of gas, V 2 Cumulative amount of desorbed gas, T 0 ＝t 0 +t，t 0 ＝1/2t 1 +t 2 ，
V 3 Solution (II) ＝A-V 1 Solution (II) -V 2 ，V 3 Solution (II) Calculating a value for the residual desorption;
s2, desorbing the coal core: the drill hole is a slurry medium or a clear water medium, and the coal core of the drill holeWhen the depth of the hole is half of the depth of the hole, the initial desorption time of the coal core is taken; desorbing the coal core to be lifted on site, and recording the time t of lifting the drill during the desorption 1 Time t for filling 2 Simultaneously recording the desorption time t in the desorption tank and the accumulated desorption amount V over the time t 2 (ii) a And recording the residual desorption V by laboratory measurement 3 Fruit of Chinese wolfberry ；
Fitting an S3 equation: the accumulated desorption amount V of the coal core sample along with the time 2 Projected in a coordinate system, and subjected to fitting of a field desorption equation to determine A and V 1 Solution (II) If the value of (A) is the calculated value of the total content of coal bed gas, V 1 Solution (II) The calculated value of the gas loss of the coal bed is obtained.
2. The method of claim 1, wherein the residual desorption amount V is calculated 3 Fruit of Chinese wolfberry The accumulated desorption amount was plotted on a piece of graph paper as a part of the accumulated desorption amount, and the equation was corrected and fitted.
3. The method for calculating the gas content in the coal seam according to claim 2, wherein the on-site desorption equation is suitable for calculating gas desorption data obtained by a coal seam gas content determination method.
4. The method for calculating the coal seam gas content according to claim 3, wherein data correction is performed by using single-point correction or double-point correction;
the single-point correction method comprises the following steps:
(1) Establishing coordinates
Projected on a piece of coordinate paper, wherein V 3 Vacuum heating degassing amount before pulverizing, V 4 For the amount of degassing after comminution, V 3 +V 4 Continuously desorbing in a desorption tank with time, and corresponding to a desorption time t i ；
(2) Using formula V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) To coordinate point
Performing repeated fitting optimization to make the coordinate point
Satisfies formula V as accurately as possible 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) The extension trend of the curve;
(3) Finally obtaining the desorption time coordinate of the optimal fitting result, and obtaining the A, B parameter value of the fitting equation and the V under the condition 1 Solution (II) ，V 1 Solution (II) The calculated gas loss is obtained;
the double-point correction method comprises the following steps:
(1) Establishing coordinates
And
projected on a graph paper, where V 3 Vacuum heating degassing amount before pulverizing, V 4 For the amount of degassing after comminution, coordinates
Corresponds to V 3 Considered as a component of the cumulative desorption amount, the corresponding analysis time is t i-1 Coordinate of
Corresponds to V 3 +V 4 Considered as a component of the cumulative desorption amount, the corresponding analysis time is t i ；
(2) Using formula V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) To coordinate point
And
performing repeated fitting optimization to make coordinate points
And
satisfies formula V as precisely as possible 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) The extension trend of the curve;
(3) Finally obtaining the desorption time coordinate of the optimal fitting result, obtaining the A, B parameter value of the fitting equation and the V under the condition 1 Solution (II) ，V 1 Solution (II) The calculated gas loss is obtained.
5. The method of claim 4, wherein the calculation of the gas desorption to V is performed 2 And V 3 +V 4 The theoretical observation time interval corresponding to time is t Δ ＝t i T, where t is the maximum cumulative desorption V 2 Corresponding cumulative desorption observation time.
6. The method for analyzing the error of the coal seam gas content calculation method according to any one of claims 1 to 5, characterized by comprising the steps of analyzing the error of residual desorption amount and analyzing the error of total gas content;
wherein the error analysis equation of the residual desorption amount is as follows:
RE＝100％×(V 3 solution (II) -V 3 Fruit of Chinese wolfberry )/V 3 Fruit of Chinese wolfberry ；
The error analysis equation of the total gas content is as follows:
R＝100％×(A-V general assembly Solution (II) )/V General assembly Solution (II) Wherein V is General assembly Solution (II) ＝V 1 Solution (II) +V 2 +V 3 Fruit of Chinese wolfberry 。
7. The error analysis method of the coal seam gas content calculation method according to claim 6, characterized by further comprising the error analysis of gas loss amount at different drilling time;
wherein, the gas loss error analysis equation of different drilling time is:
RE＝100％×[V 0 (t 1 ’)-V 0 (t 1 )]/V 0 (t 1 )；
V 0 (t 1 ) For minimum simulated drill lifting time t 1 ' amount of coal bed gas lost, i.e. actual field desorption true exposure time t 1 According to the field desorption equation V under the condition 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) Obtained V 1 Solution (II) A value of (d);
V 0 (t 1 ') time points t for different simulated drilling 1 ' calculated exposure time t 1 The loss amount of coal bed gas;
wherein, V 0 (t 1 ’)＝V 1 ’(t 1 ’)-V 0 ’(t 1 ’)；
In the formula, V 0 ’(t 1 ') simulated drill lifting time t 1 The actual desorbed gas quantity at time, read from the desorption data;
V 1 ’(t 1 ') simulated drill lifting time t 1 The gas loss at time, from the in situ desorption equation V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) According to the simulated drill lifting time t 1 ' solving;
T 0 ’＝t 0 ’+t，T 0 ' is the total desorption time;
t 0 ’＝1/2t 1 ’+t 2 t 0 ' calculated loss time, t, designed for core sample simulation 2 The canning time;
t 1 ’＝t 1 +2×T 0 ，t 1 ' to simulate the time from the lifting of the coal core to the arrival at the surface of the earth, T 0 Is at t 1 ' time the core of coal under conditions has been desorbed in the desorption tank.
8. The method for analyzing the error of the coal bed gas content calculation method according to claim 7, further comprising analyzing relative errors of the loss amount and the upper limit desorption amount caused by different desorption time points;
wherein, the analysis equation of loss amount relative error caused by different amount desorption time points is as follows:
RE V ＝100％×(V 1 k -V 1 n )/V 1 n ；
wherein, the analysis equation of the upper limit desorption amount relative error caused by different amounts of desorption time points is as follows:
RE A ＝100％×(A k -A n )/A n ；
in the formula, V 1 k And A k Respectively corresponding to desorption time points t n The gas loss amount and the upper limit desorption amount of (b); are all according to equation V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) Fitting to obtain n as an observation time point, wherein n =1,2,3,4 and … …; corresponding to a cumulative observation time of t n (ii) a k is a calculation time point, k =1,2,3,4, … … n, and k is not more than n;
V 1 n and A n The gas loss and the upper limit desorption, i.e. t, at the observation point of the longest time n Take the value at the maximum.
9. According to claim8, the error analysis method of the coal seam gas content calculation method is characterized by further comprising different desorption time points t n Analyzing the relative error of the accumulated gas desorption amount;
wherein the different desorption time points t n The relative error analysis equation of the accumulated gas desorption amount is as follows:
RE＝100％×(V 2 n ’-V 2 n )/V 2 n ；
in the formula, V 2 n For different quantities desorption time points t n Corresponding cumulative gas desorption, V, of the actual test 2 n ' is a time point t n Corresponding fitting cumulative gas desorption, V 2 n ' Desorption from site equation V 2 ＝AB·T 0 1/2 /(1+B·T 0 1/2 )-V 1 Solution (II) Found by fitting, V 2 n ' that is, V 2 ，n＝1，2，3，4……。
10. The method for analyzing errors in the calculation method of coal seam gas content according to claim 9, wherein the equation for analyzing errors in residual desorption amount, the equation for analyzing errors in total gas content, the equation for analyzing errors in gas loss amount at different drilling time, the equation for analyzing relative errors in loss amount caused by desorption time points in different quantities, the equation for analyzing relative errors in upper limit desorption amount caused by desorption time points in different quantities, and the equation for analyzing errors in desorption time points t in different quantities n The time accumulated gas desorption amount relative error analysis equation can be used for error analysis by a linear method, a logarithmic method, a polynomial method and an Amoco method gas loss amount calculation method.
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| CN102128765A (en) * | 2010-12-09 | 2011-07-20 | 中国矿业大学 | Method for directly and rapidly measuring coal seam gas content in underground coal mine |
| CN103983534A (en) * | 2014-05-26 | 2014-08-13 | 河南理工大学 | Gas loss calculation method |
| RU2601205C1 (en) * | 2015-08-07 | 2016-10-27 | Акционерное общество "Метан Кузбасса" | Method of determining gas content of coal beds |
| CN106680451A (en) * | 2015-11-09 | 2017-05-17 | 河南理工大学 | Underground rapid measurement method for coal and gas outburst parameter as well as apparatus thereof |
| CN108458951A (en) * | 2018-04-02 | 2018-08-28 | 河南理工大学 | The method that coal seam gas-bearing capacity is quickly determined by desorption efficiency |
| CN109406750A (en) * | 2018-12-06 | 2019-03-01 | 西安科技大学 | A kind of coal seam gas-bearing capacity directly measures loss amount calculation method |
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| CN102128765A (en) * | 2010-12-09 | 2011-07-20 | 中国矿业大学 | Method for directly and rapidly measuring coal seam gas content in underground coal mine |
| CN103983534A (en) * | 2014-05-26 | 2014-08-13 | 河南理工大学 | Gas loss calculation method |
| RU2601205C1 (en) * | 2015-08-07 | 2016-10-27 | Акционерное общество "Метан Кузбасса" | Method of determining gas content of coal beds |
| CN106680451A (en) * | 2015-11-09 | 2017-05-17 | 河南理工大学 | Underground rapid measurement method for coal and gas outburst parameter as well as apparatus thereof |
| CN108458951A (en) * | 2018-04-02 | 2018-08-28 | 河南理工大学 | The method that coal seam gas-bearing capacity is quickly determined by desorption efficiency |
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