Density logging instrument probe and calibration method based on X-ray source

Abstract

The invention discloses a density logging instrument probe for calibration based on an X-ray source and a calibration method thereof, belonging to the technical field of nuclear logging. Specifically, a detachable line short section and a Cs-137 source short section are used to form a density logging instrument probe, and the Cs-137 source short section is replaced by the X-ray source short section. The natural logarithm of the near-source distance count rate and the natural logarithm of the far-source distance count rate obtained by the X-ray source calibration are converted into those of the Cs-137 source by using the near-source distance coefficient and the far-source distance coefficient corresponding to each density, so as to complete the calibration of the density logging instrument of the Cs-137 source, and finally the Cs-137 source short section is installed for logging. Since the X-ray source has no radioactivity when it is not powered on, the invention uses the X-ray source to complete the calibration of the density logging instrument, which can completely eliminate the radiation exposure of the operator during the instrument calibration process.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear well logging, and in particular relates to a density well logging instrument probe calibrated based on an X-ray source and a calibration method thereof. Background Art

[0002] Density logging generally uses gamma rays emitted by a Cs-137 gamma source to irradiate the formation and measures the volume density of the formation based on the photoelectric effect and the Compton effect. At present, density logging is one of the most effective logging methods for determining formation density. It plays an important role in identifying formation lithology, calculating physical parameters, dividing reservoirs, etc., and is a must-measure item in cable logging methods. However, the existing method of using a gamma source for density logging will cause radiation damage to operators.

[0003] Radiation damage mainly occurs during the installation of Cs-137 sources during logging construction and instrument calibration. Instrument calibration refers to the entire work of establishing the conversion relationship between the measurement output data of the logging instrument and the standard value of the inherent physical parameters of the measured formation. It is a method to ensure the unit uniformity and accurate and reliable value of the measurement output data of the logging instrument. The calibration working standard well of the instrument calibration is a special measurement standard instrument for petroleum nuclear logging that reproduces and preserves the standard value of the physical parameters related to the standard formation and nuclear logging. It is generally a physical model well, and the value does not change due to different measurement methods or measuring instruments. The calibrator is a special measurement standard instrument for petroleum nuclear logging that simulates and preserves the proper value of a specific model of nuclear logging instrument. It is a value simulator, and the value may change due to different measurement methods or measuring instruments. The working standard well calibration and calibrator calibration of the density instrument are important links in the instrument manufacturing, factory inspection and use process. At present, operating engineers are required to repeatedly install the Cs-137 source.

[0004] The X-ray source is not radioactive if it is not powered on. X-ray source calibration can reduce the operator's radiation exposure working time and completely eliminate the operator's radiation exposure during the instrument calibration process.

[0005] Therefore, a density logging instrument probe and a calibration method based on an X-ray source are needed, which has a positive significance for reducing the working time of operators exposed to radiation. Summary of the invention

[0006] In view of the radiation problem of operators caused by repeated installation of Cs-137 sources during calibration of existing instruments, the present invention provides a density logging instrument probe and a calibration method based on an X-ray source for calibration, which can completely eliminate the radiation exposure of operators during density instrument calibration operations.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A density logging instrument probe for calibration based on an X-ray source comprises a line short section 21 and a Cs-137 source short section 22, wherein the line short section 21 and the Cs-137 source short section 22 are connected via a detachable structure;

[0009] The density logging instrument probe is calibrated using an X-ray source pup joint 31, which replaces the Cs-137 source pup joint 22 and is connected to the line pup joint 21 via a detachable structure. After the calibration is completed, the line pup joint 21 and the Cs-137 source pup joint 22 are connected to perform density logging.

[0010] Furthermore, the line short section 21 includes a far detector crystal 24 , a near detector crystal 25 and a circuit system 26 .

[0011] Furthermore, positioning pins 28 are provided to achieve positioning between the line short section 21 and the Cs-137 source short section 22 , and between the line short section 21 and the X-ray source short section 31 .

[0012] Furthermore, the detachable structure is a connecting screw 27 .

[0013] Furthermore, the Cs-137 source short section 22 has a Cs-137 source 23 inside, and the X-ray source short section 31 has an X-ray source 32 inside.

[0014] The method for calibrating a probe of a density logging instrument based on an X-ray source comprises the following steps:

[0015] Step 1: Connect the line short section 21 and the Cs-137 source short section 22, and obtain the near-source counting rate N of the Cs-137 source 23 by calibrating with a calibrator. γS The natural logarithm of lnN γS The linear relationship between the density and the far-source count rate N of the Cs-137 source 23 γL The natural logarithm of lnN γL A linear relationship with density;

[0016] Step 2: Connect the line short section 21 and the X-ray source short section 31, and obtain the near-source distance count rate N of the X-ray source 32 by calibrating with a calibrator. XS The natural logarithm of lnN XS The linear relationship between the density and the far-source count rate N of the X-ray source 32 XL The natural logarithm of lnN XL A linear relationship with density;

[0017] Step 3: According to the results of step 1 and step 2, calculate the near-source distance coefficient X corresponding to each density. S and the distance coefficient X L ;

[0018] Step 4: Connect the line short section 21 and the X-ray source short section 31, and obtain the near-source count rate N of the X-ray source 32 at the corresponding density through the working standard well scale of different densities. XS The natural logarithm of 'lnN XS ', and the far-source counting rate N XL The natural logarithm of 'lnN XL ';

[0019] Step 5, based on X S and X L , calculate the near-source counting rate N of Cs-137 source 23 at the corresponding density γS The natural logarithm of 'lnN γS ', far-source counting rate N γL The natural logarithm of 'lnN γL ':

[0020] n γS '=X S ×lnN XS '

[0021] n γL '=X L ×lnN XL '

[0022] Step 6: Cs-137 source 23 at different densities γS ' and lnN γL ', put it into the calculation formula of the density value and its correction amount in the calibration standard of the petroleum nuclear logging instrument, solve it to obtain the density calibration response coefficient corresponding to the Cs-137 source 23, connect the line short section 21 and the Cs-137 source short section 22, and obtain the calibrated density logging instrument probe.

[0023] Furthermore, the near-source distance coefficient X in step 3 S and the distance coefficient X L are the corresponding near-source distance count rate logarithmic ratio lnN γS / lnN XS and the logarithmic ratio of the count rate from the far source, lnN γL / lnN XL , or the corresponding near-source counting rate ratio N γS / N XS and the ratio of the far-source count rate N γL / N XL .

[0024] Furthermore, both step 1 and step 2 utilize scale blocks 41 of different densities to calibrate the scaler.

[0025] Furthermore, step 4 uses at least five working standard well scales of different densities.

[0026] The present invention also proposes the application of the density logging instrument probe calibrated based on an X-ray source in a density logging instrument.

[0027] Furthermore, the density logging instrument is a density logging while drilling instrument or a density logging cable instrument.

[0028] Furthermore, the density logging while drilling instrument includes a while drilling drill collar 103 , and a mud channel 106 and a drill collar cavity 112 located inside the while drilling drill collar 103 ; the density logging instrument probe calibrated based on an X-ray source is installed inside the drill collar cavity 112 .

[0029] The beneficial effects of the present invention are:

[0030] The present invention proposes a density logging instrument probe for calibration based on an X-ray source and a calibration method thereof. A detachable line short section and a Cs-137 source short section are used to form the density logging instrument probe, and the Cs-137 source short section is replaced by the X-ray source short section to complete the calibration of the density logging instrument of the Cs-137 source, and finally the Cs-137 source short section is installed to perform logging. Since the X-ray source has no radioactivity when it is not powered on, the present invention uses the X-ray source to complete the calibration of the density logging instrument, which can completely eliminate the radiation exposure of operators during the instrument calibration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the three-dimensional structure of a Cs-137 source probe of a density logging instrument calibrated based on an X-ray source provided in Example 1 of the present invention;

[0032] Figure 2 A schematic diagram of the planar structure of a Cs-137 source probe of a density logging instrument based on an X-ray source for calibration provided in Example 1 of the present invention; wherein (a) is Figure 1 (b) is the top view; (c) is the section BB of the top view;

[0033] Figure 3 It is a schematic diagram of the three-dimensional structure of the X-ray source probe of the density logging instrument installed with the X-ray source pup joint in Example 1 of the present invention;

[0034] Figure 4 Schematic diagram of the planar structure of the X-ray source probe of the density logging instrument equipped with the X-ray source short section in Example 1 of the present invention; wherein (a) is Figure 3 (b) is the top view; (c) is the section BB of the top view;

[0035] Figure 5This is a schematic diagram of the scale of the density logging instrument probe in which the Cs-137 source is placed in Example 1 of the present invention;

[0036] Figure 6 A schematic diagram of the scale of a density logging instrument probe in which an X-ray source is placed in Example 1 of the present invention;

[0037] Figure 7 is the near-source counting rate N of the Cs-137 source in Example 1 of the present invention γS The natural logarithm of lnN γS A linear relationship with density;

[0038] Figure 8 is the far-source counting rate N of the Cs-137 source in Example 1 of the present invention γL The natural logarithm of lnN γL A linear relationship with density;

[0039] Fig. 9 is the near-source count rate N of the X-ray source in Example 1 of the present invention XS The natural logarithm of lnN XS A linear relationship with density;

[0040] Fig.10 is the far-source count rate N of the X-ray source in Example 1 of the present invention XL The natural logarithm of lnN XL A linear relationship with density;

[0041] Fig.11 is the near-source counting rate N of the Cs-137 source in Example 1 of the present invention γS The natural logarithm of lnN γS The linear relationship between the density and the count rate N at the near-source distance of the X-ray source XS The natural logarithm of lnN XS Overlay of the linear relationship with density;

[0042] Fig.12 is the far-source counting rate N of the Cs-137 source in Example 1 of the present invention γL The natural logarithm of lnN γL The linear relationship between the density and the far-source count rate N of the X-ray source XL The natural logarithm of lnN XL Overlay of the linear relationship with density;

[0043] Fig.13 This is a schematic diagram of an implementation scheme of a density logging while drilling instrument based on X-ray source calibration in Example 1 of the present invention;

[0044] Fig.14This is a schematic diagram of the installation of a density logging instrument probe and a while-drilling drill collar in Example 1 of the present invention;

[0045] Fig.15 This is a schematic diagram of an implementation scheme of a density logging cable instrument based on X-ray source calibration in Example 1 of the present invention;

[0046] The descriptions of the symbols in the accompanying drawings are as follows:

[0047] Formation 101, borehole 102, while drilling drill collar 103, while drilling instrument electronic circuit short section 104, while drilling instrument CS-137 source short section 105, mud channel 106, cable instrument body 107, cable instrument power short section 108, cable instrument line short section 109, cable instrument CS-137 source short section 110, while drilling density probe 111, drill collar cavity for installing while drilling density probe 112, line short section 21, CS-1 37 source short section 22, Cs-137 source 23, far detector crystal 24, near detector crystal 25, circuit system 26, first connecting screw 27, positioning pin 28, line short section end face 29, Cs-137 source short section end face 210, Cs-137 source active body 211, X-ray source short section 31, X-ray source 32, second connecting screw 33, X-ray source short section end face 34, scale block 41, section AA, section BB. DETAILED DESCRIPTION

[0048] In order to better understand the purpose and function of the present invention, the present invention is described in more detail below in conjunction with the accompanying drawings. In the following specific embodiments, many specific details are set forth to provide a thorough understanding of embodiments of the present invention. However, those skilled in the art will appreciate that embodiments of the present invention may be implemented without these specific details.

[0049] Example 1

[0050] This embodiment provides a Cs-137 source probe for density logging instrument based on X-ray source calibration, and its three-dimensional structure is as follows: Figure 1 As shown, the planar structure is Figure 2 As shown, it includes a line short section 21 and a Cs-137 source short section 22, and the line short section 21 and the Cs-137 source short section 22 are connected by a detachable structure; the Cs-137 source short section 22 has a Cs-137 source 23 inside, specifically a Cs-137 source active body 211; the line short section 21 includes a far detector crystal 24, a near detector crystal 25 and a circuit system 26.

[0051] Specifically, Figure 1The installation and disassembly process between the line short section 21 and the Cs-137 source short section 22 is shown. Two positioning pins 28 are set on the line short section end face 29 to match the corresponding pin holes on the Cs-137 source short section end face 210, and at least two first connecting screws 27 are set on the Cs-137 source short section end face 210 to match the corresponding screw holes on the line short section end face 29, thereby achieving the fit between the line short section end face 29 and the Cs-137 source short section end face 210, and the fastening between the line short section 21 and the Cs-137 source short section 22, ensuring that they have the same positional relationship after repeated disassembly and assembly.

[0052] Figure 2 (a) Figure 1 The top view of the CS-137 source probe of the density logging tool shown. Figure 2 (b) and Figure 2 (c) are schematic diagrams of section AA and section BB in the top view, respectively. It can be seen that in section AA, the circuit system 26, the far detector crystal 24, the near detector crystal 25 and the Cs-137 source active body 211 are arranged in sequence, and the axes of the far detector crystal 24, the near detector crystal 25 and the Cs-137 source active body 211 are all located on section AA.

[0053] Among them, the Cs-137 source 23 emits gamma rays, and the far detector crystal 24 and the near detector crystal 25 realize detection. Under the premise that the parameters of the circuit system 26, the far detector crystal 24 and the near detector crystal 25 remain unchanged, the instrument response is mainly affected by the geometric conditions, specifically: the long source distance L between the far detector crystal 24 and the Cs-137 source active body 211, the short source distance S between the near detector crystal 25 and the Cs-137 source active body 211, the centerline distance M of the Cs-137 source active body 211 from the far detector crystal 24 or the near detector crystal 25, and the distance N from the axis of the Cs-137 source 23 to the end face 210 of the Cs-137 source short section; L = L1 + N, S = S1 + N, L1 is the distance from the far detector crystal 24 to the end face 29 of the line short section, S1 is the distance from the near detector crystal 25 to the end face 29 of the line short section. Since the line short section 21 and the Cs-137 source short section 22 have the same positional relationship after being disassembled and assembled for many times, L, S, M and N remain unchanged.

[0054] The density logging instrument Cs-137 source probe uses an X-ray source pup joint 31 for calibration. The X-ray source pup joint 31 replaces the Cs-137 source pup joint 22 and is connected to the line pup joint 21 via a detachable structure. The X-ray source pup joint 31 has an X-ray source 32 inside. After the calibration is completed, the line pup joint 21 and the Cs-137 source pup joint 22 are connected to perform density logging.

[0055] Specifically, Figure 3The disassembly process between the line short section 21 and the X-ray source short section 31 is shown. By setting a positioning pin 28 and a second connecting screw 33 between the line short section 21 and the X-ray source short section 31, the fitting between the line short section end face 29 and the X-ray source short section end face 34 is achieved, and the fastening between the line short section 21 and the X-ray source short section 31 is ensured to have the same positional relationship after repeated disassembly and assembly; wherein, the pin hole on the X-ray source short section end face 34 corresponds to the pin hole on the Cs-137 source short section end face 210, and the second connecting screw 33 is set on the X-ray source short section end face 34, and the length is slightly different from that of the first connecting screw 27.

[0056] Figure 4 for Figure 3 The planar structure of the X-ray source probe of the density logging tool with the X-ray source short section 31 installed is shown. Figure 4 (a) is a top view, Figure 4 (b) and Figure 4 (c) are schematic diagrams of section AA and section BB in the top view, respectively. It can be seen that the axes of the far detector crystal 24, the near detector crystal 25 and the X-ray source 32 are all located on section AA.

[0057] Among them, the X-ray source 32 emits X-rays; the line short section 21 remains unchanged, and the instrument response is mainly affected by geometric conditions, specifically: the long source distance L' between the far detector crystal 24 and the X-ray source 32, the short source distance S' between the near detector crystal 25 and the X-ray source 32, the distance O of the axis of the X-ray source 32 from the center line of the far detector crystal 24 or the near detector crystal 25, and the distance P from the emission port of the X-ray source 32 to the end face 34 of the X-ray source short section; L' = L1 + P, S' = S1 + P. Since the line short section 21 and the X-ray source short section 31 have the same positional relationship after being disassembled and assembled multiple times, L', S', O and P remain unchanged.

[0058] This embodiment also proposes a calibration method for a density logging instrument probe based on an X-ray source, comprising the following steps:

[0059] Step 1: Connect the line short section 21 and the Cs-137 source short section 22, and use the scale blocks 41 of different densities to calibrate the scaler to obtain the near-source counting rate N of the Cs-137 source. γS The natural logarithm of lnN γS The linear relationship between the density and the far-distance count rate N of the Cs-137 source γL The natural logarithm of lnN γL The linear relationship between and density is as follows: Figure 7 and Figure 8 As shown;

[0060] In this embodiment, a scale block 41 made of pure metal materials with different density values ​​is used, and the density measurement range of the metal material is selected as 1.1 g / cm 3 ~3g / cm 3 Intermediate values, such as magnesium blocks (ρ = 1.74 g / cm 3 ) and aluminum block (ρ=2.7g / cm 3 );like Figure 5 As shown, a density logging instrument probe of a Cs-137 source is placed in the scale block 41 to calibrate the scaler;

[0061] Step 2: Connect the line short section 21 and the X-ray source short section 31, and use the scale blocks 41 of different densities to calibrate the scaler to obtain the near-source count rate N of the X-ray source. XS The natural logarithm of lnN XS The linear relationship between the density and the far-distance count rate N of the X-ray source XL The natural logarithm of lnN XL The linear relationship between and density is as follows: Fig. 9 and Fig.10 As shown;

[0062] like Figure 6 As shown, in this embodiment, a density logging instrument probe replacing the X-ray source short section 31 is placed in the scale block 41 to perform scaler calibration;

[0063] Step 3: Figure 7 and Fig. 9 Plotted on a graph, we get Fig.11 , calculate the near-source distance coefficient X corresponding to each density S , specifically the logarithmic ratio of the near-source distance count rate X S (X S <1):

[0064] X S =lnN γS / lnN XS

[0065] Will Figure 8 and Fig.10 Plotted on a graph, we get Fig.12 , calculate the distant source distance coefficient X corresponding to each density L , specifically the logarithmic ratio of the far-source count rate X L (X L <1):

[0066] X L =lnN γL / lnN XL

[0067] Step 4: Connect the line short section 21 and the X-ray source short section 31, and obtain the near-source count rate N of the X-ray source at the corresponding density by using at least five working standard well calibrations of different densities according to the standard process of oil nuclear logging instrument calibration. XS The natural logarithm of 'lnN XS ', and the far-source counting rate N XL The natural logarithm of 'lnN XL ';

[0068] In this embodiment, an X-ray source is used to calibrate each density instrument during the instrument manufacturing process. This involves calibration during instrument manufacturing, factory inspection, and use. The process refers to "SY / T6582-2019 Petroleum Nuclear Logging Instrument Calibration Specification" or "SY / T6582.3-2003 Petroleum Nuclear Logging Instrument Calibration Part 3: Compensated Density Lithology Density Logging Instrument Calibration";

[0069] Step 5, based on X S and X L , calculate the near-source counting rate N of the Cs-137 source at the corresponding density under any conditions γS The natural logarithm of 'lnN γS ', far-source counting rate N γL The natural logarithm of 'lnN γL ':

[0070] n γS '=X S ×lnN XS '

[0071] n γL '=X L ×lnN XL '

[0072] Step 6: lnN of Cs-137 source at different densities γS ' and lnN γL ', put it into the calculation formula of the density value and its correction value in the calibration standard of the petroleum nuclear logging instrument, solve it to get the density calibration response coefficient corresponding to the Cs-137 source, connect the line short section 21 and the Cs-137 source short section 22, and get the calibrated density logging instrument probe, which can be used for density logging.

[0073] For example, for "SY / T6582.3-2003 Petroleum Nuclear Logging Instrument Calibration Part 3: Compensated Density Lithology Density Logging Instrument Calibration":

[0074] ρ=AlnN ss +BlnN ls +C

[0075] Δρ=ρ-(DlnNls +E)

[0076] in:

[0077] n ss =lnN γS '=X S ×lnN XS '

[0078] n ls =lnN γL '=X L ×lnN XL '

[0079] N ls It indicates the count rate of the density logging tool at long source distance, cps, counts per second;

[0080] N ss It represents the short-source distance count rate measured by the density logging tool, cps;

[0081] ρ represents the density value, g / cm 3 ;

[0082] Δρ represents the density correction value;

[0083] A, B, C, D, and E are density scale response coefficients.

[0084] By adopting at least five working standard well calibrations of different densities, A, B, C, D and E can be solved and then a density logging instrument probe with calibration can be obtained.

[0085] The density logging instrument probe calibrated based on an X-ray source proposed in this embodiment can be applied to a density logging while drilling instrument or a density logging cable instrument.

[0086] Specifically, Fig.13 The invention is an implementation scheme of a density logging while drilling instrument based on X-ray source calibration, comprising a circular while drilling drill collar 103, and a mud channel 106 and a drill collar cavity 112 located inside the while drilling drill collar 103; Fig.14 As shown, the density logging instrument probe based on X-ray source calibration is installed inside the drill collar cavity 112, including the while drilling instrument electronic circuit short section 104 and the while drilling instrument CS-137 source short section 105; wherein, the mud channel 106 is used to circulate mud; the while drilling instrument electronic circuit short section 104 includes sodium iodide or iodine bromide crystal, photomultiplier tube, high voltage and preamplifier circuit, and the while drilling instrument electronic circuit short section 104 may also include a digital circuit; the density logging while drilling instrument is placed inside the wellbore 102 of the formation 101.

[0087] Fig.15The invention discloses a density logging cable instrument implementation scheme based on X-ray source calibration, comprising a cable instrument body 107, a cable instrument power short section 108 and a density logging instrument probe based on X-ray source calibration; the density logging instrument probe based on X-ray source calibration comprises a cable instrument line short section 109 and a cable instrument Cs-137 source short section 110; the cable instrument line short section 109 comprises a sodium iodide or iodine bromide crystal, a photomultiplier tube, a high voltage and a preamplifier circuit, and considering the weight and space limitations, the cable instrument line short section 109 generally does not include a digital circuit; the density logging cable instrument is placed inside a wellbore 102 in a formation 101.

[0088] The while drilling instrument electronic circuit short section 104 and the cable instrument line short section 109 are specifically the line short section 21 in this embodiment, and the while drilling instrument CS-137 source short section 105 and the cable instrument CS-137 source short section 110 are specifically the CS-137 source short section 22 in this embodiment.

[0089] Example 2

[0090] This embodiment proposes a density logging instrument probe and a calibration method thereof based on an X-ray source. The structure of the density logging instrument probe is exactly the same as that of the embodiment 1. The calibration method is different from that of the embodiment 1 in that the near-source distance coefficient X corresponding to each density calculated in step 3 is converted into S The specific formula is adjusted to: Calculate the near-source distance count rate ratio X S (X S <1):

[0091] X S =N γS / N XS

[0092] Calculate the distant source distance coefficient X corresponding to each density L The specific formula is adjusted to: Calculate the far source distance count rate ratio X L (X L <1):

[0093] X L =N γL / N XL

[0094] The other steps are exactly the same.

[0095] In summary, the present invention adopts a detachable line short section and a Cs-137 source short section to form a density logging instrument probe, and uses an X-ray source short section to replace the Cs-137 source short section to complete the calibration of the density logging instrument of the Cs-137 source, and finally installs the Cs-137 source short section to perform logging; since the X-ray source has no radioactivity when it is not powered on, the present invention uses the X-ray source to complete the calibration of the density logging instrument, which can eliminate the radiation exposure of the operator during the instrument calibration process.

[0096] The above embodiments are only used to illustrate the technical method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical method of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A method for calibrating a probe of a density logging instrument based on an X-ray source, characterized in that: The density logging instrument probe comprises a line short section and a Cs-137 source short section, and the line short section and the Cs-137 source short section are connected via a detachable structure; an X-ray source short section is used for calibration, and the X-ray source short section replaces the Cs-137 source short section and is connected to the line short section via a detachable structure; after the calibration is completed, the line short section and the Cs-137 source short section are connected to perform density logging; The calibration method comprises the following steps: Step 1: Connect the line short section and the Cs-137 source short section, and obtain the near-source counting rate N of the Cs-137 source by calibrating with the calibrator. γS The natural logarithm of lnN γS The linear relationship between the density and the far-distance count rate N of the Cs-137 source γL The natural logarithm of lnN γL A linear relationship with density; Step 2: Connect the line short section and the X-ray source short section, and obtain the near-source count rate N of the X-ray source by calibrating the scaler. XS The natural logarithm of lnN XS The linear relationship between the density and the far-distance count rate N of the X-ray source XL The natural logarithm of lnN XL A linear relationship with density; Step 3: According to the results of step 1 and step 2, calculate the near-source distance coefficient X corresponding to each density. S and the distance coefficient X L , respectively, are the corresponding near-source distance count rate logarithmic ratio lnN γS / lnN XS and the logarithmic ratio of the count rate from the far source, lnN γL / lnN XL , or the corresponding near-source counting rate ratio N γS / N XS and the ratio of the far-source count rate N γL / N XL ; Step 4: Connect the line short section and the X-ray source short section, and obtain the near-source count rate N of the X-ray source at the corresponding density through the working standard well scale of different densities. XS The natural logarithm of 'lnN XS ', and the far-source counting rate N XL The natural logarithm of 'lnN XL '; Step 5, based on X S and X L , calculate the near-source counting rate N of the Cs-137 source at the corresponding density γS The natural logarithm of 'lnN γS ', far-source counting rate N γL The natural logarithm of 'lnN γL ': lnN γS '=X S ×lnN XS ' lnN γL '=X L ×lnN XL ' Step 6: lnN of Cs-137 source at different densities γS ' and lnN γL ', put it into the calculation formula of density value and correction value in the calibration standard of petroleum nuclear logging instrument, solve it to get the density calibration response coefficient corresponding to Cs-137 source, connect the line short section and Cs-137 source short section to get the density logging instrument probe with calibration completed.

2. The calibration method for a density logging instrument probe based on an X-ray source according to claim 1, characterized in that: The line short section includes a far detector crystal, a near detector crystal and a circuit system.

3. The calibration method of the density logging instrument probe based on the X-ray source calibration according to claim 1, characterized in that: Positioning pins are provided between the line short section and the Cs-137 source short section, and between the line short section and the X-ray source short section to achieve positioning.

4. The calibration method for a density logging instrument probe based on an X-ray source according to any one of claims 1 to 3, characterized in that: The Cs-137 source short section has a Cs-137 source inside, and the X-ray source short section has an X-ray source inside.

5. The calibration method for a density logging instrument probe based on an X-ray source calibration according to claim 1, characterized in that: In both step 1 and step 2, the calibrator is calibrated using calibrating blocks of different densities.

6. The calibration method for a density logging instrument probe based on an X-ray source calibration according to claim 1, characterized in that: Step 4 uses at least five working standard well scales of different densities.

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