Fitting method of well fluid absorption coefficient for gamma detector

Abstract

The present invention discloses a method for fitting the well fluid absorption coefficient of a gamma detector, comprising: using a gamma detector to measure the standard fluid absorption coefficient corresponding to different equivalent water layer thicknesses along the well axis of a borehole, wherein the equivalent water layer thickness includes a plurality of equivalent water layer thickness values, and the well fluid absorption coefficient includes a plurality of well fluid absorption values; taking at least three adjacent data pairs corresponding to the equivalent water layer thickness value and the well fluid absorption value as a data point group, adding trend lines to the data points of the data point group to form a curve segment, and the endpoints of the curve segments of the adjacent data point groups overlap to form a data pair scatter curve; performing point-by-point error control between the fitting value and the standard value for the data pair corresponding to each curve segment, so that the relative error between the fitting value and the standard value falls within the required range. The present invention aims at the phenomenon of missing ore caused by the well fluid correction error in the prior art, and can prevent the situation of missing ore caused by the gamma interpretation software interpretation.

Description

Technical Field

[0001] The invention belongs to the gamma logging technology, and in particular relates to a fitting method for a well fluid absorption coefficient of a gamma detector. Background Art

[0002] Gamma logging plays a very important role in uranium mining geological work. It is a method of detecting the intensity of gamma rays released by radioactive uranium elements contained in underground rock formations in the borehole, and then obtaining the uranium content of the rock formations by calculation.

[0003] In the gamma logging process, the wellbore fluid in the borehole absorbs part of the gamma rays in the formation, and the greater the density of the wellbore fluid, the greater the impact of the wellbore fluid, and the stronger the ability of the wellbore fluid to absorb gamma rays, resulting in a low measured gamma ray intensity, which affects the accurate calculation of the subsequent content. For this reason, the "Gamma Logging Specification" clearly regulates the wellbore fluid correction method and the wellbore fluid absorption coefficient of the gamma ray intensity of the equivalent water layer thickness for different types of instruments and different well conditions (vertical or inclined state of the borehole).

[0004] In practical applications, the calculated measured equivalent water layer thickness and the corresponding interval value given in the specification are linearly interpolated to obtain the well fluid absorption coefficient (referred to as the standard well fluid absorption coefficient).

[0005] There is another method for calculating the well fluid absorption coefficient that is widely used in actual work, that is, regression analysis, which uses regression technology to establish a functional relationship between different equivalent water layer thicknesses given in the specification and the standard absorption coefficient, fit it into a mathematical expression, and then substitute the calculated measured equivalent water layer thickness into the formula to find the well fluid absorption coefficient (referred to as calculating the well fluid absorption coefficient). This method is suitable for automatic continuous calculation by computer programming.

[0006] The above-mentioned standard well fluid absorption coefficient and calculated well fluid absorption coefficient both belong to the well fluid absorption coefficient of gamma ray intensity.

[0007] After all, regression analysis is a statistical method, which allows a certain amount of data fluctuation between the regression value and the sample data (the standard absorption coefficient given by the specification, the same below). If you do not pay attention to this data fluctuation (referred to as error for short), unacceptable results will occur: the inability to accurately correct the well fluid absorption will result in low logging gamma intensity, thus causing missed ore.

[0008] The gamma interpretation software currently used in the sandstone-type uranium exploration system has once had an example of missing a mine. When the gamma data of the ZKB2020-6 borehole logging in the ×× area of ​​the ×× basin was interpreted using the above interpretation software, the calculated well fluid absorption coefficient of the well fluid at 406.9 meters was 18%, while the standard well fluid absorption coefficient of the well fluid at this point calculated using the standard calculation method was 22.99%, a difference of 4.99%. The well fluid correction coefficient calculated by the software corrected the gamma irradiation rate to 28.86nC / (kg·h), and the interpreted uranium content was 0.0212% (Table 1). Points like this are treated as false anomalies of deconvolution interpretation and excluded from the list of uranium thin layers because their irradiation rate is less than the instrument sensitivity of 30.42 (Nc / kg·h) / 0.01%eU.

[0009] Table 1 Comparison of the correction and processing results of the well fluid absorption coefficient using the standard and calculation methods for the ZKB20020-6 borehole gamma automatic interpretation

[0010]

[0011]

[0012] The FD-3019 gamma detector is the most widely used instrument type in the uranium geological exploration industry. The borehole with an inclination of 90° is the most common borehole design used in sandstone uranium exploration, and the logging probe is measured along the well axis when the borehole is vertical. In the sandstone uranium exploration system, the FD-3019 gamma detector is used to measure the well fluid absorption coefficient along the well axis. When the gamma interpretation software is used for interpretation, the result will show the situation of missing ore due to the well fluid correction error.

[0013] like Figure 1 As shown, it is a data scatter plot of the well fluid absorption coefficient of different equivalent water layer thicknesses measured along the well axis by the FD-3019 gamma detector given in the "Gamma Well Logging Specification" in the prior art.

[0014] It can be seen from the scatter plot that the curve obtained by measuring the wellbore absorption coefficient of different equivalent water layer thicknesses along the well axis using the FD-3019 gamma detector given in the "Gamma Well Logging Specifications" is similar in shape to a negative exponential growth curve. When fitting using the regression analysis method, the sixth-order polynomial was used, but there is still a large relative error between the regression value and the sample data. Summary of the invention

[0015] The purpose of the present invention is to provide a fitting method for the well fluid absorption coefficient of a gamma detector, which can prevent the ore leakage caused by the well fluid correction error in the prior art and avoid the ore leakage caused by the gamma interpretation software.

[0016] To achieve the above purpose, the technical solution used in the present invention is:

[0017] The fitting method of the gamma detector well fluid absorption coefficient includes:

[0018] Using a gamma detector to measure standard fluid absorption coefficients corresponding to different equivalent water layer thicknesses along the well axis of the borehole, the equivalent water layer thickness includes a plurality of equivalent water layer thickness values, and the well fluid absorption coefficient includes a plurality of well fluid absorption values;

[0019] At least three adjacent data pairs corresponding to the equivalent water layer thickness value and the well fluid absorption value are used as a data point group, and trend lines are added to the data points of the data point group to form a curve segment, and the endpoints of the curve segments of adjacent data point groups overlap to form a data pair scatter curve;

[0020] For each data pair corresponding to the curve segment, error control is performed point by point between the fitting value and the standard value, so that the relative error between the fitting value and the standard value falls within the required range.

[0021] Furthermore, each equivalent water layer thickness value corresponds to a well fluid absorption value.

[0022] Furthermore, the gamma detector selected is the FD-3019 gamma detector, and the borehole is in a vertical or inclined state.

[0023] Furthermore, a scatter plot corresponding to the equivalent water layer thickness value and the well fluid absorption value is produced, including:

[0024] Put the equivalent water layer thickness value and the well fluid absorption value into an Excel table. For the water layer thickness column and the absorption coefficient column in the Excel table, starting from the first row of equivalent water layer thickness value and standard well fluid absorption value, select the continuous data pairs, open the Insert option in the Excel menu bar, then open the Chart option in the toolbar of the option, select the Scatter Plot Tool, and make the curve segment corresponding to the data point group;

[0025] In the curve segment of the data pair, right-click and select the Add Trend Line option in the pop-up window to implement error control point by point between the fitted value and the standard value of the data pair; check the error data corresponding to the data pair. If the relative error is within the required range, this round of fitting is successful.

[0026] Further, the relative error between the fitted value and the standard value is calculated using the formula: δ represents the relative error between the fitted value and the standard value. represents the fitted value, X i Indicates standard value.

[0027] Furthermore, if the relative error is outside the required range, the number of fitted data pairs is reduced and fitting is continued until the relative error is within the required range.

[0028] Furthermore, a second-order polynomial fitting is selected.

[0029] Furthermore, 5 data pairs are selected to form a data point group, and the curve segments of the data pair scatter curve are piecewise fitted.

[0030] Furthermore, if the relative error is outside the required range, a straight line fitting method is selected.

[0031] Furthermore, the second round of fitting takes the ending data pair of the previous round of fitting as the starting point, and then selects the adjacent arranged data pairs to continue fitting, controlling the error point by point until all the data pairs are fitted.

[0032] The technical effects of the present invention include:

[0033] The present invention adopts the method of segmented fitting and segmented point-by-point error control to fit the functional relationship between different equivalent water layer thicknesses measured by the FD-3019 gamma detector along the well axis and the well fluid absorption coefficient given in the "Gamma Well Logging Specifications" with high precision. This can completely prevent the situation where ore leakage is easily caused when using gamma interpretation software for interpretation. The application has achieved good results and can prevent the occurrence of ore leakage incidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a data scatter plot of the well fluid absorption coefficient of different equivalent water layer thicknesses measured along the well axis by the FD-3019 gamma detector given in the "Gamma Well Logging Specification" in the prior art;

[0035] Figure 2 It is a schematic diagram of the piecewise fitting and point-by-point error control method in the present invention. DETAILED DESCRIPTION

[0036] The following description sufficiently illustrates specific embodiments of the invention to enable those skilled in the art to practice and reproduce the invention.

[0037] The fitting method of the well fluid absorption coefficient of the gamma detector includes the following specific steps:

[0038] Step 1: using a gamma detector to measure the standard fluid absorption coefficient corresponding to different equivalent water layer thicknesses along the well axis of the borehole, the equivalent water layer thickness includes a plurality of equivalent water layer thickness values, and the well fluid absorption coefficient includes a plurality of well fluid absorption values;

[0039] Each equivalent water layer thickness value corresponds to a well fluid absorption value.

[0040] In this preferred embodiment, the gamma detector is a FD-3019 gamma detector, and the borehole is in a vertical or inclined state.

[0041] Step 2: Take at least three adjacent data pairs corresponding to the equivalent water layer thickness value and the well fluid absorption value as a data point group, add trend lines to the data points of the data point group to form a curve segment, and overlap the endpoints of the curve segments of adjacent data point groups to form a data pair scatter curve;

[0042] like Figure 2 The figure shows a schematic diagram of the segmented fitting and point-by-point error control method in the present invention.

[0043] To make a scatter plot of equivalent water layer thickness and well fluid absorption values, the specific operations are:

[0044] Put the equivalent water layer thickness value and well fluid absorption value into an Excel table. For the water layer thickness column and absorption coefficient column in the Excel table, starting from the first row of equivalent water layer thickness value and standard well fluid absorption value, select 5 consecutive data pairs, open the "Insert" option in the Excel menu bar, then open the "Chart" option in the toolbar of the option, and finally select the "Scatter Plot" tool to complete the curve segment corresponding to the data point group.

[0045] The rationale for selecting five data pairs is that the original standard data pairs are fitted as a whole using exponential, logarithmic, and power methods. From the fitting results shown in the scatter plot, there is a large error between the fitting results and the standard values. Even when the polynomial is fitted up to the sixth order, there is an intolerable error. Therefore, piecewise fitting of the five data pairs is the best choice.

[0046] In this preferred embodiment, the equivalent water layer thickness value measured by the FD-3019 gamma detector along the well axis is 29 data, with a value range of 2.5 to 130 mm.

[0047] Process other data point groups in turn to complete the data pair scatter curve.

[0048] Step 3: For each data pair corresponding to the curve segment, error control is performed point by point between the fitting value and the standard value, so that the relative error between the fitting value and the standard value falls within the required range.

[0049] Step 3.1: In the curve segment of the 5 data pairs, right-click and select the "Add Trendline (R)..." option in the pop-up window. In the "Set Trendline Format" window, select 2nd order polynomial and display the formula and display R square value;

[0050] Because from a rough look at the scatter plot, the results of the second-order polynomial fitting are in good agreement with the standard values. The high order affects the computer's computing speed and is not conducive to its promotion and application.

[0051] Step 3.2: Implement error control point by point between the fitted values ​​and the standard values ​​of the five data pairs;

[0052] The specific method of implementing error control point by point is: write the Excel fitting formula into the corresponding position of the "fit value" column ( Figure 2 ), X in formula (1) is a data in the “water layer thickness” column in the original standard data column.

[0053] Calculate the relative error between the fitted value and the standard value using the following formula:

[0054]

[0055] Where: δ represents the relative error between the fitted value and the standard value, %;

[0056] represents the fitted value, %;

[0057] X i Indicates standard value, %

[0058] Figure 2 In the relative position of the "Relative Error 1" column, enter formula (1). is the data in the Fitted Values ​​column, X i It is the data in the "Absorption Value" column of the original standard data column.

[0059] Step 3.3: Check the error data in the "Relative Error 1" column. If the relative error is within the required range (between -0.5% and 0.32%, the current round of fitting is considered successful and the fitting formula is recorded. If the relative error is outside the required range, reduce the number of fitting data pairs from five to four and continue fitting according to the above steps, calculate the relative error in the "Relative Error 2" column, and check the error calculation results. If the relative error is still outside the required range, reduce the number of fitting data pairs from four to three and continue fitting according to the above steps, calculate the relative error in the "Relative Error 3" column, and check the error calculation results until the relative error is within the required range. Three data pairs are the minimum number of data to fit with a second-order polynomial. If the relative error is outside [-0.5%, 0.32%], it means that the group of data pairs is not suitable for fitting with a second-order polynomial, and a straight line method is used instead until the relative error is between [-0.5%, 0.32%].

[0060] The second round of fitting takes the ending data pair of the previous round of fitting as the starting point, and then selects 5 consecutive data pairs to continue fitting, controlling the error point by point until all 29 data pairs are fitted.

[0061] By adopting the segmented fitting and point-by-point error control method of the present invention, the 29 data points of different equivalent water layer thicknesses (D) and well fluid absorption coefficients (η) measured by the FD-3019 gamma detector along the well axis given in the specification are divided into 12 curve segments, and the function expression and relative error of each curve segment regression are listed as follows:

[0062] Ⅰ. When D>=2.5 and D<=7.5:

[0063] η=-0.008*D 2 +0.54*D-0.2

[0064] R 2 =1, relative error 0%~1.31×0%;

[0065] II. When D>7.5 and D<=12.5:

[0066] η=0.016*D 2 +0.12*D+1.6

[0067] R 2 =1, relative error 0%~0%;

[0068] III. When D>12.5 and D<=20:

[0069] η=0.52*D 0.939

[0070] R 2 =0.999, relative error -0.50%~0.19%;

[0071] IV. When D>20 and D<=30:

[0072] η=0.37D+1.2833

[0073] R 2 =0.9998, relative error -0.19%~0.32%;

[0074] V. When D>30 and D<=40:

[0075] η=0.008*D 2 -0.26*D+13

[0076] R 2 =1, relative error 0%~0%

[0077] VI. When D>40 and D<=60:

[0078] η=0.31*D+3.04

[0079] R2 =0.9997, relative error -0.32%~0.26%;

[0080] VII. When D>60 and D<=70:

[0081] η=0.004*D 2 -0.26*D(i)+7.4

[0082] R 2 =1.00, relative error 0%~0%;

[0083] VIII. When D>70 and D(i)<=80:

[0084] η=0.24*D(i)+7.4

[0085] R 2 =1.00, relative error 0%~0%;

[0086] IX. When D>80 and D(i)<=90:

[0087] η=0.002*D 2 -0.13*D+24.2

[0088] R 2 =1.00, relative error 0%~0%;

[0089] Ⅹ. When D>90 and D<=110:

[0090] η=-0.003*D 2 +0.741*D-13.91

[0091] R 2 =0.999, relative error -0.03%~0.03%;

[0092] Ⅺ. When D(i)>110 and D(i)<=120:

[0093] η=-0.004*D 2 +1.02*D-32.5

[0094] R 2 =1, relative error 0%~0%;

[0095] Ⅻ. When D(i)>120 and D(i)<=130:

[0096] η=0.002*D 2 -0.43*D+55.1

[0097] R 2 =1Relative error 0.00%~0.00%.

[0098] In order to verify the application effect of the improved absorption coefficient, the above formula was applied to the program to interpret the gamma data of borehole logging ZKB2020-6 in the ×× area of ​​the ×× basin. The results are shown in Table 2.

[0099] Table 2 Comparison of correction and processing results of well fluid absorption coefficient using improved calculation and standard method for ZKB20020-6 borehole gamma automatic interpretation

[0100]

[0101]

[0102] As can be seen from Table 2, the difference between the improved calculated absorption coefficient and the standard absorption coefficient is only a slight error in the decimal place. The corrected exposure rate at 406.9 meters is 30.80nC / (kg·h), and the uranium content interpreted by the five-point deconvolution is 0.0228%. Since the gamma ray exposure rate at this point is greater than the sensitivity of the instrument, it is identified as a thin uranium layer. This example shows that the improved calculated absorption coefficient has completely changed the shortcomings of the original program calculation, allowing the logging software to calculate the correct interpretation results.

[0103] The terms used in the present invention are illustrative and exemplary, rather than restrictive. Since the present invention can be implemented in various forms without departing from the spirit or essence of the technical solution, it should be understood that the above embodiments are not limited to any of the aforementioned details, but should be widely interpreted within the spirit and scope defined by the attached claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the attached claims.

Claims

1. A method for fitting the absorption coefficient of a gamma detector well fluid, characterized in that: include: Using a gamma detector to measure standard fluid absorption coefficients corresponding to different equivalent water layer thicknesses along the well axis of the borehole, the equivalent water layer thickness includes a plurality of equivalent water layer thickness values, and the well fluid absorption coefficient includes a plurality of well fluid absorption values; At least three adjacent data pairs corresponding to the equivalent water layer thickness value and the well fluid absorption value are taken as a data point group, trend lines are added to the data points of the data point group to form curve segments, and scatter plots corresponding to the equivalent water layer thickness value and the well fluid absorption value are produced, including: putting the equivalent water layer thickness value and the well fluid absorption value into an Excel table, selecting continuous data pairs from the first row of equivalent water layer thickness value and standard well fluid absorption value for the water layer thickness column and the absorption coefficient column in the Excel table, opening the Insert option in the Excel menu bar, then opening the Chart option in the toolbar of the option, selecting the Scatter Plot Tool, and producing curve segments corresponding to the data point group; in the curve segment of the data pair, right-clicking and selecting the Add Trend Line option in the pop-up window, and implementing error control point by point between the fitted value of the data pair and the standard value; checking the error data corresponding to the data pair, if the relative error is within the required range, the current round of fitting is successful; the endpoints of the curve segments of adjacent data point groups coincide to form a scatter curve of the data pair; Calculate the relative error between the fitted value and the standard value using the formula: δ represents the relative error between the fitted value and the standard value. represents the fitted value, Xi 表 Indicates standard value; For each data pair corresponding to the curve segment, error control is performed point by point between the fitting value and the standard value, so that the relative error between the fitting value and the standard value falls within the required range.

2. The method for fitting the gamma detector well fluid absorption coefficient according to claim 1, characterized in that: Each equivalent water layer thickness value corresponds to a well fluid absorption value.

3. The method for fitting the gamma detector well fluid absorption coefficient according to claim 1, characterized in that: The gamma detector used is FD-3019 gamma detector, and the borehole is in vertical or inclined state.

4. The method for fitting the gamma detector well fluid absorption coefficient according to claim 1, characterized in that: If the relative error is outside the required range, the number of fitted data pairs will be reduced and fitting will continue until the relative error is within the required range.

5. The method for fitting the gamma detector well fluid absorption coefficient according to claim 1, characterized in that: A 2nd order polynomial fit was selected.

6. The method for fitting the gamma detector well fluid absorption coefficient according to claim 1, characterized in that: Five data pairs are selected to form a data point group, and the curve segments of the data pair scatter curve are piecewise fitted.

7. The method for fitting the gamma detector well fluid absorption coefficient according to claim 4, characterized in that: If the relative error is outside the required range, use the straight line fitting method.

8. The method for fitting the gamma detector well fluid absorption coefficient according to claim 7, characterized in that: The second round of fitting takes the ending data pair of the previous round of fitting as the starting point, and then selects adjacent arranged data pairs to continue fitting, controlling the error point by point until all data pairs are fitted.

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