Source spacing determination method, system and equipment for density logging and storage medium

Abstract

The invention discloses a spacing determination method, system and device for density logging and a storage medium, and belongs to the technical field of pulse radioactive source logging in oil-gas exploration. Comprising the following steps: establishing a stratum detection model by utilizing Monte Carlo simulation software; obtaining the relationship between the counting rate and the long source spacing and the relationship between the counting rate and the short source spacing through a stratum detection model, and preliminarily screening the value ranges of the long source spacing and the short source spacing; further screening the value ranges of the long spacing and the short spacing according to the statistical error and the measurement precision of the stratum detection model; and determining a final value range of the short spacing by using a short spacing compensation function and a sensitivity requirement. The method can quickly determine the value range of long spacing and short spacing, has higher accuracy, is reasonable, can help to improve the accuracy of density instrument data, obtains high-precision stratum density parameters, enables subsequent logging interpretation and analysis to be more accurate, and improves the accuracy of the density instrument data. And certain logging cost can be saved.

Description

Technical Field

[0001] The invention belongs to the technical field of pulsed radioactive source logging in oil and gas exploration, and relates to a source distance determination method, system, equipment and storage medium for density logging. Background Art

[0002] At present, density logging is one of the indispensable logging methods in traditional logging methods. Density logging uses gamma sources to release gamma rays. Gamma rays interact with formation materials, thereby attenuating or disappearing. Long and short detectors record gamma count rates to study formation density. At present, lithologic density logging is widely used in the petroleum logging industry. It can not only measure the photoelectric absorption cross-section index, but also accurately measure the density value of the formation, which plays a great role in the analysis of different formation porosity and lithology. The determination of the source distance of the density logging instrument will directly affect the accuracy of the logging data. Reasonable density logging source distance is of great significance for the measurement of complex structures, complex lithology, and complex pore structures. Reasonable source distance confirmation method for density logging instruments can help improve the accuracy of data, make subsequent logging interpretation and analysis more accurate, and save certain logging costs. At present, the source distance of the long detector is mainly determined by the relationship between the count rate and the source distance and the measurement error; the source distance of the short detector is mainly determined by the sensitivity of the instrument. However, the source distance error determined by a single method is large. Summary of the invention

[0003] The purpose of the present invention is to solve the technical problem that the source distance determined by a single method in the prior art has a large error, and to provide a method, system, device and storage medium for determining the source distance of density logging.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a method for determining source distance of density logging, comprising the following steps:

[0006] Establishing formation detection model using Monte Carlo simulation software;

[0007] The relationship between the count rate and the long source distance and the short source distance is obtained from the formation detection model, and the range of the long source distance and the short source distance is preliminarily selected;

[0008] The range of long source distance and short source distance is further screened according to the statistical error and measurement accuracy of the formation detection model;

[0009] The short source distance compensation function and sensitivity requirements are used to determine the final value range of the short source distance.

[0010] A further improvement of the present invention is:

[0011] The method of establishing a stratum detection model using Monte Carlo simulation software comprises the following steps:

[0012] A logging instrument model is established; the logging instrument comprises a radioactive source, a long source distance detector, a short source distance detector, an instrument housing and a shielding body; the radioactive source is a 137Cs source; the material of the logging instrument housing is a titanium alloy; the material of the shielding body is a tungsten-nickel-iron material; the logging instrument has a diameter of 42 mm and a length of 500 mm; the long source distance detector is a cylindrical lanthanum bromide crystal with a radius of 14 mm and a length of 13 mm, and the short source distance detector is a cylindrical lanthanum bromide crystal with a radius of 17 mm and a length of 20 mm;

[0013] A borehole and formation model was established; the borehole and formation were designed as a series of cylinders, with a borehole radius of 10 cm, a formation radius of 10 cm-80 cm, and a height of 100 cm.

[0014] The relationships between the count rate and the long source distance and the short source distance are obtained from the formation detection model, and the preliminary screening of the value ranges of the long source distance and the short source distance comprises the following steps:

[0015] estimating a maximum long source distance value range of a long source distance detector and a maximum short source distance value range of a short source distance detector of the logging instrument;

[0016] Uniformly selecting a number of point values ​​in the maximum long source distance value range and the maximum short source distance value range, respectively, and inputting the point values ​​into the formation detection model to obtain the counting rate corresponding to each point value, thereby obtaining the relationship between the counting rate and the long source distance and the short source distance;

[0017] Since the counting rate corresponding to the long source distance needs to measure a deeper stratum, the higher the counting rate received by the long source distance detector, the more conducive it is to analyzing the physical properties of the reservoir. Therefore, the long source distance detector requires a high counting rate to further screen the value range of the long source distance; and the short source distance mainly measures the mud cake and plays a compensatory role, so the appropriate counting rate can meet the demand and further screen the value range of the short source distance.

[0018] The further screening of the value ranges of the long source distance and the short source distance according to the statistical error and measurement accuracy of the formation detection model comprises the following steps:

[0019] Input different values ​​of long source distance and short source distance in the formation detection model to obtain corresponding measurement results;

[0020] Performing error analysis on the measurement results to obtain the relationship between the long source distance, the short source distance and the error respectively;

[0021] The formation detection model simulation density logging requires that the measurement error is less than 1%, based on which the value ranges of long source distance and short source distance are further screened.

[0022] Determining the final value range of the short source distance by using the short source distance compensation function and the sensitivity requirement comprises the following steps:

[0023] Evenly select a number of point values ​​in the value range of the short source distance after further screening, and input the point values ​​into the formation detection model to obtain the counting rate corresponding to each point value, and then calculate the relative sensitivity from the counting rate to obtain the relationship between the relative sensitivity and the short source distance;

[0024] Since the greater the relative sensitivity, the less favorable it is for short detectors to measure reservoirs, the range of values ​​for short source distances continues to narrow.

[0025] According to the compensation function of short source distance for long source distance, the relative sensitivities under several different combinations of long source distance and short source distance are obtained. The final value range of short source distance is determined because the larger the relative sensitivity, the less favorable it is for short detectors to measure reservoirs.

[0026] The sensitivity A and relative sensitivity S are:

[0027] The sensitivity A is:

[0028]

[0029] In actual work, the sensitivity A is represented by relative sensitivity S, which is:

[0030]

[0031] Where N is the counting rate and ρ is the formation density.

[0032] The compensation function of the short source distance to the long source distance specifically includes:

[0033] When the long source distance is fixed and the short source distance increases, the distance between the long source distance detector and the short source distance detector decreases, and both the sensitivity and relative sensitivity decrease; when the density increases, the relative sensitivity decreases, while the sensitivity remains unchanged; therefore, the short source distance and the distance between the long source distance detector and the short source distance detector should be increased to improve the sensitivity, thereby determining the final value range of the short source distance.

[0034] In a second aspect, the present invention provides a source distance determination system for density logging, characterized in that it comprises:

[0035] Modeling unit, using Monte Carlo simulation software to establish a formation detection model;

[0036] Preliminary screening of units, using the formation detection model to obtain the relationship between the count rate and the long detector source distance and the short detector source distance, and preliminary screening of the value range of the long source distance and the short source distance;

[0037] The secondary screening unit further screens the value range of long source distance and short source distance according to the statistical error and measurement accuracy of the formation detection model;

[0038] The final screening unit determines the final value range of the short source distance by using the short source distance compensation function and the sensitivity requirements.

[0039] In a third aspect, the present invention provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the source distance determination method for density logging as described in any one of claims 1 to 7 when executing the computer program.

[0040] In a fourth aspect, the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the method for determining the source distance of density logging according to any one of claims 1 to 7.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The invention discloses a method for determining source distance of density logging, which determines the value range of long source distance and short source distance by combining elements such as counting rate, statistical error and measurement accuracy, firstly determines the reasonable range of long and short source distance by using the relationship between counting rate and source distance, then reduces the value range of long and short source distance by using statistical error and measurement accuracy on the basis of the first step, and finally determines the value range of long and short source distance of density logging by using the compensation function of short source distance to long source distance and the sensitivity of short source distance. The invention can quickly determine the value range of long and short source distance, and has higher accuracy, and the reasonable source distance confirmation method of density logging instrument can help improve the accuracy of density instrument data, obtain high-precision formation density parameters, make subsequent logging interpretation and analysis more accurate, and can also save certain logging costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 A flow chart of a method for determining source distance of density logging in the present invention;

[0045] Figure 2 It is a schematic diagram of a formation detection model in a method for determining source distance of density logging in the present invention;

[0046] Figure 3 A schematic diagram of the relationship between the long source distance and the count rate after simulation using the formation detection model of the present invention;

[0047] Figure 4 A schematic diagram showing the relationship between short source distance and count rate after simulation using the formation detection model of the present invention;

[0048] Figure 5 A schematic diagram showing the relationship between the long source distance and the error after simulation using the formation detection model of the present invention;

[0049] Figure 6 A schematic diagram showing the relationship between short source distance and error after simulation using the formation detection model of the present invention;

[0050] Figure 7 A graph showing the relationship between the error of the density measurement value and the count rate when the formation detection model of the present invention is used for measurement;

[0051] Figure 8 Schematic diagram of the relationship between long source distance and counting rate;

[0052] Fig. 9 This is a schematic diagram of the relationship between short source distance and relative sensitivity;

[0053] Fig.10 A system diagram of a method for determining source distance of density logging in the present invention;

[0054] Fig.11 This is a module diagram of an electronic device for a method for determining source distance of density logging in the present invention. DETAILED DESCRIPTION

[0055] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0056] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0058] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0059] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0060] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0061] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0062] See also Figure 1 The embodiment of the present invention provides a method for determining the source distance of density logging, comprising the following steps:

[0063] S1, using Monte Carlo simulation software to establish a formation detection model;

[0064] S2, the relationship between the count rate and the long source distance and the short source distance is obtained from the formation detection model, and the value range of the long source distance and the short source distance is preliminarily selected;

[0065] S3, further screening the value range of long source distance and short source distance according to the statistical error and measurement accuracy of the formation detection model;

[0066] S4, using the short source distance compensation function and sensitivity requirements to determine the final value range of the short source distance.

[0067] The invention discloses a method for determining source distance of density logging, which determines the value range of long source distance and short source distance by combining elements such as counting rate, statistical error and measurement accuracy, firstly determines the reasonable range of long and short source distance by using the relationship between counting rate and source distance, then reduces the value range of long and short source distance by using statistical error and measurement accuracy on the basis of the first step, and finally determines the value range of long and short source distance of density logging by using the compensation function of short source distance to long source distance and the sensitivity of short source distance. The invention can quickly determine the value range of long and short source distance, and has higher accuracy, and the reasonable source distance confirmation method of density logging instrument can help improve the accuracy of density instrument data, obtain high-precision formation density parameters, make subsequent logging interpretation and analysis more accurate, and can also save certain logging costs.

[0068] The content of the present invention is described in detail below in conjunction with specific embodiments:

[0069] Step 1: Use Monte Carlo simulation software to establish a formation detection model.

[0070] See also Figure 2 , formation detection model, and Monte Carlo numerical simulation. The instrument structure mainly includes radioactive source, detector, instrument housing, shielding body, etc. The radioactive source adopts 137Cs source, the instrument housing adopts titanium alloy, the shielding body adopts tungsten nickel iron material, the lower part of the instrument is wrapped with a boron sleeve, and the size information of the main part of the logging instrument is as follows: the logging instrument has a diameter of 42mm and a length of 500mm; the long source distance detector has a radius of 14mm and a cylindrical lanthanum bromide crystal with a length of 13mm, and the short source distance detector is a cylindrical lanthanum bromide crystal with a radius of 17mm and a length of 20mm; the wellbore and the formation are designed as a series of cylinders, the wellbore radius is 10cm, the formation part radius is 10cm-80cm, and the height is 100cm.

[0071] This example uses Monte Carlo (MCNP) numerical simulation to establish Figure 2 In the formation detection model shown, the formation material to be detected is set as a pure sandstone formation with a porosity of 10% and 100% saturation with water, and the long detector and the short detector are simulated respectively by changing the source distance.

[0072] Step 2: Obtain the relationship between the count rate and the long source distance and the short source distance from the formation detection model, and preliminarily select the value range of the long source distance and the short source distance.

[0073] According to the actual density logging instrument, the simulated porosity φ is 0%, 10%, 20%, 30%, and 40% respectively. The long source distance of the long detector is 37cm-41cm, and the short source distance of the short detector is 16cm-20cm. The relationship between the counting rate and the long source distance and the short source distance is obtained, as shown in the figure: Figure 3 and Figure 4As shown. The longer the source distance, the deeper the formation needs to be measured. The higher the count rate received by the detector, the more conducive it is to analyzing the physical properties of the reservoir. Therefore, the detector with a longer source distance requires a higher count rate. Figure 3 After analysis, we found that the range of the long source distance is 37-40cm. The short source distance mainly measures the mud cake and plays a compensation role, so the appropriate counting rate can meet the demand. Figure 4 After analysis, it was found that the range of short source distance is 16cm-20cm.

[0074] Step three: further screen the value range of long source distance and short source distance according to the statistical error and measurement accuracy of the formation detection model.

[0075] By analyzing the errors corresponding to the measurement results obtained by Monte Carlo numerical simulation, we can get the relationship between source distance and error. As the source distance increases, the measurement error becomes larger, such as Figure 5 and Figure 6 As shown. Monte Carlo numerical simulation density logging requires the measurement error to be less than 1%. Figure 5 and Figure 6 The relationship shown in the figure shows that for long source distance, when the source distance is 41cm, the measurement error is higher than 1%, and the measurement range of long source distance is 37-40cm. For short source distance, since the distance to the source is closer, the counting rate is larger and the measurement accuracy is higher, so when the source distance is 16-20cm, the measurement error is less than 1%.

[0076] According to the measurement accuracy analysis of the EILog instrument (source is 1.5Ci), we get Figure 7 The relationship between the error of density measurement and the count rate. It can be seen from the figure that when the density error is below 0.01g / cm3, the minimum count rate required is 3070cps. Since the density error is mainly determined by the long source distance, the relationship between the long source distance count rate and the long source distance is calculated here, as shown in the figure. Figure 8 As shown in the figure, when the density error is below 0.01g / cm3, the required minimum counting rate is 3070cps, and the maximum source distance should be below 39cm. Comprehensive consideration shows that the longest source distance should be selected between 37-39cm.

[0077] Step 4: Use the short source distance compensation function and sensitivity requirements to determine the final value range of the short source distance.

[0078] In density logging, short detectors need to measure the physical properties of the near-surface formation, so the sensitivity requirements for short detectors are relatively high. The sensitivity definition formula is:

[0079]

[0080] In actual work, relative sensitivity S is often used to represent the sensitivity of the instrument, and its definition formula is:

[0081]

[0082] The relationship between relative sensitivity and short source distance is as follows: Fig. 9 As shown in the figure, with the increase of short source distance, the relative sensitivity increases. High sensitivity is not conducive to the measurement of near-ground layers at short source distance, so the value of short source distance can be shortened to less than 19 cm.

[0083] According to the compensation function of short source distance for long source distance, this paper further determines the value range of short source distance by comparing the sensitivity under different source distance combinations, as shown in the following table:

[0084] Table 1 Sensitivity analysis of different source distance combinations

[0085]

[0086] Table 1 shows that when the long source distance is fixed, the short source distance increases, the distance between the near and far detectors decreases, and the absolute sensitivity and relative sensitivity of density measurement decrease; the greater the density, the lower the relative sensitivity, while the absolute sensitivity remains unchanged. Therefore, from the perspective of density measurement sensitivity, the source distance and detector spacing should be increased as much as possible to improve the sensitivity. Therefore, from the perspective of the combined sensitivity of the short source distance and the long source distance, the short source distance can be between 16-18cm.

[0087] See also Fig.10 The embodiment of the present invention provides a source distance determination system for density logging, comprising:

[0088] Modeling unit, using Monte Carlo simulation software to establish a formation detection model;

[0089] Preliminary screening of units, using the formation detection model to obtain the relationship between the count rate and the long detector source distance and the short detector source distance, and preliminary screening of the value range of the long source distance and the short source distance;

[0090] The secondary screening unit further screens the value range of long source distance and short source distance according to the statistical error and measurement accuracy of the formation detection model;

[0091] The final screening unit determines the final value range of the short source distance by using the short source distance compensation function and the sensitivity requirements.

[0092] See also Fig.11 The third object of the present invention is to provide an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for determining the source distance of density logging when executing the computer program.

[0093] Establishing formation detection model using Monte Carlo simulation software;

[0094] The relationship between the count rate and the long source distance and the short source distance is obtained from the formation detection model, and the range of the long source distance and the short source distance is preliminarily selected;

[0095] The range of long source distance and short source distance is further screened according to the statistical error and measurement accuracy of the formation detection model;

[0096] The short source distance compensation function and sensitivity requirements are used to determine the final value range of the short source distance.

[0097] A fourth object of the present invention is to provide a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method for determining the source distance of density logging are implemented.

[0098] Establishing formation detection model using Monte Carlo simulation software;

[0099] The relationship between the count rate and the long source distance and the short source distance is obtained from the formation detection model, and the range of the long source distance and the short source distance is preliminarily selected;

[0100] The range of long source distance and short source distance is further screened according to the statistical error and measurement accuracy of the formation detection model;

[0101] The short source distance compensation function and sensitivity requirements are used to determine the final value range of the short source distance.

[0102] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0103] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1A device that provides the functions specified in a block or multiple blocks.

[0104] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0105] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps of the functions specified in one or more boxes, such as Figure 8 shown.

[0106] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for determining source distance of density logging, characterized in that: The following steps are involved: Establishing formation detection model using Monte Carlo simulation software; The relationship between the count rate and the long source distance and the short source distance is obtained from the formation detection model, and the range of the long source distance and the short source distance is preliminarily selected; The range of long source distance and short source distance is further screened according to the statistical error and measurement accuracy of the formation detection model; The short source distance compensation function and sensitivity requirements are used to determine the final value range of the short source distance.

2. The method for determining source distance of density logging according to claim 1, characterized in that: The method of establishing a stratum detection model using Monte Carlo simulation software comprises the following steps: A logging instrument model is established; the logging instrument comprises a radioactive source, a long source distance detector, a short source distance detector, an instrument housing and a shielding body; the radioactive source is a 137Cs source; the material of the logging instrument housing is a titanium alloy; the material of the shielding body is a tungsten-nickel-iron material; the logging instrument has a diameter of 42 mm and a length of 500 mm; the long source distance detector is a cylindrical lanthanum bromide crystal with a radius of 14 mm and a length of 13 mm, and the short source distance detector is a cylindrical lanthanum bromide crystal with a radius of 17 mm and a length of 20 mm; A borehole and formation model was established; the borehole and formation were designed as a series of cylinders, with a borehole radius of 10 cm, a formation radius of 10 cm-80 cm, and a height of 100 cm.

3. The method for determining source distance of density logging according to claim 1, characterized in that: The relationships between the count rate and the long source distance and the short source distance are obtained from the formation detection model, and the preliminary screening of the value ranges of the long source distance and the short source distance comprises the following steps: estimating a maximum long source distance value range of a long source distance detector and a maximum short source distance value range of a short source distance detector of the logging instrument; Uniformly selecting a number of point values ​​in the maximum long source distance value range and the maximum short source distance value range, respectively, and inputting the point values ​​into the formation detection model to obtain the counting rate corresponding to each point value, thereby obtaining the relationship between the counting rate and the long source distance and the short source distance; Since the counting rate corresponding to the long source distance needs to measure a deeper stratum, the higher the counting rate received by the long source distance detector, the more conducive it is to analyzing the physical properties of the reservoir. Therefore, the long source distance detector requires a high counting rate to further screen the value range of the long source distance; and the short source distance mainly measures the mud cake and plays a compensatory role, so the appropriate counting rate can meet the demand and further screen the value range of the short source distance.

4. The method for determining source distance of density logging according to claim 1, characterized in that: The further screening of the value ranges of the long source distance and the short source distance according to the statistical error and measurement accuracy of the formation detection model comprises the following steps: Input different values ​​of long source distance and short source distance in the formation detection model to obtain corresponding measurement results; Performing error analysis on the measurement results to obtain the relationship between the long source distance, the short source distance and the error respectively; The formation detection model simulation density logging requires that the measurement error is less than 1%, based on which the value ranges of long source distance and short source distance are further screened.

5. The method for determining source distance of density logging according to claim 4, characterized in that: Determining the final value range of the short source distance by using the short source distance compensation function and the sensitivity requirement comprises the following steps: Evenly select a number of point values ​​in the value range of the short source distance after further screening, and input the point values ​​into the formation detection model to obtain the counting rate corresponding to each point value, and then calculate the relative sensitivity from the counting rate to obtain the relationship between the relative sensitivity and the short source distance; Since the greater the relative sensitivity, the less favorable it is for short detectors to measure reservoirs, the range of values ​​for short source distances continues to narrow. According to the compensation function of short source distance for long source distance, the relative sensitivities under several different combinations of long source distance and short source distance are obtained. The final value range of short source distance is determined because the larger the relative sensitivity, the less favorable it is for short detectors to measure reservoirs.

6. The method for determining source distance of density logging according to claim 5, characterized in that: The sensitivity A and relative sensitivity S are: The sensitivity A is: In actual work, the sensitivity A is represented by relative sensitivity S, which is: Where N is the counting rate and ρ is the formation density.

7. The method for determining source distance of density logging according to claim 5, characterized in that: The compensation function of the short source distance to the long source distance specifically includes: When the long source distance is fixed and the short source distance increases, the distance between the long source distance detector and the short source distance detector decreases, and both the sensitivity and relative sensitivity decrease; when the density increases, the relative sensitivity decreases, while the sensitivity remains unchanged; therefore, the short source distance and the distance between the long source distance detector and the short source distance detector should be increased to improve the sensitivity, thereby determining the final value range of the short source distance.

8. A density logging source distance determination system, characterized in that: include: Modeling unit, using Monte Carlo simulation software to establish a formation detection model; Preliminary screening of units, using the formation detection model to obtain the relationship between the count rate and the long detector source distance and the short detector source distance, and preliminary screening of the value range of the long source distance and the short source distance; The secondary screening unit further screens the value range of long source distance and short source distance according to the statistical error and measurement accuracy of the formation detection model; The final screening unit determines the final value range of the short source distance by using the short source distance compensation function and the sensitivity requirements.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for determining source distance of density logging according to any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the steps of the method for determining source distance of density logging according to any one of claims 1 to 7.

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