A method, system, and computer device for environmental correction of formation porosity

Abstract

The application discloses a formation porosity environmental correction method, system and computer equipment, and relates to the technical field of neutron logging, and the method comprises the steps of: obtaining a specific value of a thermal neutron detector count ratio of a preset formation when logging by using a neutron porosity logging instrument; correcting the specific value of the thermal neutron detector count ratio of the preset formation; determining a target apparent porosity acquisition strategy corresponding to the specific value of the corrected thermal neutron detector count ratio; calculating a specific value of an apparent porosity of the preset formation according to the target apparent porosity acquisition strategy and the specific value of the corrected thermal neutron detector count ratio; and determining a specific value of a corrected porosity of the preset formation based on a relationship between the specific value of the apparent porosity and apparent porosity-correction porosity corresponding to an environmental factor associated with logging. The application can reduce the influence of the environmental factor on the apparent porosity, and obtain a more accurate formation porosity.

Description

Technical Field

[0001] This invention relates to the field of neutron logging technology, and in particular to an environmental correction method, system and computer equipment for formation porosity. Background Technology

[0002] Porosity logging is a crucial part of open-hole logging. Traditional neutron porosity logging typically uses an Am-Be neutron source as the radiation source. However, this method poses radiation hazards to operators and carries the risk of the source becoming stuck downhole; failure to retrieve it would result in environmental radiation damage.

[0003] Due to its environmental friendliness, the use of controllable neutron sources to replace traditional chemical sources such as Am-Be for "passive" green logging has become the main direction of neutron logging technology. Controllable source neutron porosity logging is developing rapidly and has broad application prospects.

[0004] Neutron porosity logging instruments are affected by the complex environment of the wellbore and formation. Influencing factors include well diameter, lithology, well fluid salinity, formation water salinity, mud density, mud cake thickness, gaps, and formation temperature. These factors result in a non-negligible deviation between the porosity directly measured by the instrument and the actual formation porosity. Therefore, environmental correction for neutron porosity logging must be performed during field measurements, especially comprehensive correction for multiple environmental factors.

[0005] The 14MeV neutrons generated by the DT neutron generator have a large inelastic scattering cross section in the formation. The influence mechanism of various environmental factors on porosity measurement is very different from that of chemical source neutron instruments. The existing environmental correction method for chemical source neutron porosity logging is no longer applicable. It is necessary to establish a multi-factor environmental correction method suitable for DT source neutron porosity logging.

[0006] Currently, most mature environmental correction methods for neutron porosity measurement in China are designed for chemical sources. However, for controlled-source neutron porosity measurement, on the one hand, the inelastic scattering of neutron transport cannot be ignored, leading to a more complex interaction mechanism between neutrons and the formation compared to chemical source neutrons. This also results in a decrease in the sensitivity of porosity measurement, making environmental correction more technically challenging. On the other hand, research on environmental correction methods for controlled-source neutron porosity measurement in China is still in its early stages, and the technology is not yet mature. Summary of the Invention

[0007] The technical problem to be solved by this invention is to address the shortcomings of existing technologies, and specifically provides an environmental correction method, system, and computer equipment for formation porosity, as detailed below:

[0008] 1) In a first aspect, the present invention provides an environmental correction method for formation porosity, the specific technical solution of which is as follows:

[0009] When logging using a neutron porosity logging instrument, the specific value of the thermal neutron detector count ratio of the preset formation is obtained;

[0010] The specific value of the thermal neutron detector count ratio of the preset formation is corrected to obtain the corrected specific value of the thermal neutron detector count ratio.

[0011] Determine the target apparent porosity acquisition strategy corresponding to the specific value of the corrected thermal neutron detector count ratio, and calculate the specific value of the apparent porosity of the preset formation based on the target apparent porosity acquisition strategy and the specific value of the corrected thermal neutron detector count ratio.

[0012] Based on the specific value of apparent porosity and the relationship between apparent porosity and corrected porosity corresponding to environmental factors associated with well logging, the specific value of corrected porosity for the preset formation is determined.

[0013] The beneficial effects of the formation porosity environmental correction method provided by this invention are as follows:

[0014] It can reduce the impact of environmental factors on apparent porosity and obtain more accurate formation porosity.

[0015] Based on the above scheme, the environmental correction method for formation porosity of the present invention can be further improved as follows.

[0016] Furthermore, the specific value of the thermal neutron detector count ratio for the preset formation is corrected to obtain the corrected specific value of the thermal neutron detector count ratio, including:

[0017] The specific value R of the thermal neutron detector count ratio of the preset formation is corrected using a correction formula to obtain the corrected specific value R′ of the thermal neutron detector count ratio. The correction formula is as follows: Where r1 is the source distance of the near-thermal neutron detector of the neutron porosity logging instrument, and r2 is the source distance of the far-thermal neutron detector of the neutron porosity logging instrument. L′ f Indicates: Corrected fast neutron deceleration length, L f The fast neutron deceleration length, L0 represents the deceleration length L of fast neutrons during inelastic scattering under pure water conditions. f The amount of contribution, E′ is the initial energy of the fast neutron, E″ is the average energy of the neutron after inelastic scattering, and ζ H Σ represents the average logarithmic energy loss of hydrogen. in_O It is the inelastic scattering cross section of oxygen, Σ el_H It is the elastic scattering cross section of hydrogen.

[0018] Furthermore, the target apparent aperture acquisition strategy corresponding to the specific value of the corrected thermal neutron detector count ratio is determined, including:

[0019] The system determines whether the corrected thermal neutron detector count ratio exceeds a preset thermal neutron detector count ratio threshold. If the result is yes, the target apparent aperture acquisition strategy is to calculate the apparent aperture based on the density-containing inversion formula between the thermal neutron detector count ratio and the apparent aperture. If the result is no, the target apparent aperture acquisition strategy is to calculate the apparent aperture based on the density-free inversion formula between the thermal neutron detector count ratio and the apparent aperture.

[0020] Furthermore, the relationship between apparent porosity and corrected porosity corresponding to a single environmental factor is as follows: The apparent porosity correction formula for a single environmental factor is: Where φ′ represents the corrected porosity, φ a For apparent porosity, A, B, C, and D are correction coefficients;

[0021] Based on the specific value of apparent porosity and the relationship between apparent porosity and corrected porosity corresponding to environmental factors associated with well logging, the specific value of corrected porosity for the preset formation is determined, including:

[0022] When the environmental factor associated with well logging is a single environmental factor, the specific value of the apparent porosity is calibrated according to the apparent porosity correction formula corresponding to the single environmental factor, and the specific value of the corrected porosity of the preset formation is determined.

[0023] Furthermore, the process of obtaining the specific values ​​of A, B, C, and D includes:

[0024] Data fitting was performed on multiple sets of one-to-one corresponding apparent porosity and corrected porosity under the influence of a single environmental factor to obtain the specific values ​​of A, B, C and D under the influence of a single environmental factor.

[0025] Furthermore, based on the specific value of apparent porosity and the relationship between apparent porosity and corrected porosity corresponding to well logging-related environmental factors, the specific value of corrected porosity for the preset formation is determined, which also includes:

[0026] When the environmental factors associated with well logging are multiple environmental factors, and when the judgment result is yes, calculate the total correction amount corresponding to the multiple environmental factors, and determine the specific value of the corrected porosity by summing the total correction amount corresponding to the multiple environmental factors and the specific value of the apparent porosity.

[0027] Furthermore, the process of calculating the total correction amount corresponding to multiple environmental factors includes:

[0028] When there are two environmental factors with a strong coupling relationship among multiple environmental factors, the correction amount corresponding to the two environmental factors can be calculated by using the relationship between the apparent porosity and the corrected porosity of the two environmental factors.

[0029] Using the aperture correction formula corresponding to each environmental factor that does not have a strong coupling relationship, the correction amount corresponding to each environmental factor that does not have a strong coupling relationship is calculated;

[0030] The sum of the correction values ​​for each pair of environmental factors with strong coupling and the correction values ​​for each environmental factor without strong coupling is taken as the total correction value for multiple environmental factors.

[0031] Furthermore, based on the specific value of apparent porosity and the relationship between apparent porosity and corrected porosity corresponding to well logging-related environmental factors, the specific value of corrected porosity for the preset formation is determined, which also includes:

[0032] When the judgment result is negative, the correction amount corresponding to each environmental factor is calculated. The multiple environmental factors are sorted in descending order of correction amount. The specific value of the corrected porosity corresponding to the first single environmental factor is used as the specific value of the apparent porosity corresponding to the second single environmental factor. The specific value of the corrected porosity corresponding to the second single environmental factor is calculated. The specific value of the corrected porosity corresponding to the second single environmental factor is used as the specific value of the apparent porosity corresponding to the third single environmental factor. The specific value of the corrected porosity corresponding to the third single environmental factor is calculated. After traversing all environmental factors, the specific value of the last calculated corrected porosity is used as the specific value of the corrected porosity of the preset formation.

[0033] 2) Secondly, the present invention also provides an environmental correction system for formation porosity, the specific technical solution of which is as follows:

[0034] It includes an acquisition module, a correction module, a determination module, a calculation module, and a calibration module;

[0035] The acquisition module is used to obtain the specific value of the thermal neutron detector count ratio of a preset formation when logging using a neutron porosity logging instrument.

[0036] The correction module is used to correct the specific value of the thermal neutron detector count ratio of the preset formation to obtain the corrected specific value of the thermal neutron detector count ratio.

[0037] The determination module is used to: determine the target aperture acquisition strategy corresponding to the specific value of the corrected thermal neutron detector count ratio;

[0038] The calculation module is used to: calculate the specific value of the apparent porosity of the preset formation based on the target apparent porosity acquisition strategy and the specific value of the corrected thermal neutron detector count ratio;

[0039] The correction module is used to determine the specific value of the corrected porosity of a preset formation based on the specific value of the apparent porosity and the relationship between the apparent porosity and the corrected porosity corresponding to the environmental factors associated with well logging.

[0040] Based on the above scheme, the formation porosity environmental correction system of the present invention can be further improved as follows.

[0041] Furthermore, the correction module is specifically used for:

[0042] The specific value R of the thermal neutron detector count ratio of the preset formation is corrected using a correction formula to obtain the corrected specific value R′ of the thermal neutron detector count ratio. The correction formula is as follows: Where r1 is the source distance of the near-thermal neutron detector of the neutron porosity logging instrument, and r2 is the source distance of the far-thermal neutron detector of the neutron porosity logging instrument. L′ f Indicates: Corrected fast neutron deceleration length, L f The fast neutron deceleration length, L0 represents the deceleration length L of fast neutrons during inelastic scattering under pure water conditions. f The amount of contribution, E′ is the initial energy of the fast neutron, E″ is the average energy of the neutron after inelastic scattering, and ζ H Σ represents the average logarithmic energy loss of hydrogen. in_O It is the inelastic scattering cross section of oxygen, Σ el_H It is the elastic scattering cross section of hydrogen.

[0043] Furthermore, it was determined that the module is specifically used for:

[0044] The system determines whether the corrected thermal neutron detector count ratio exceeds a preset thermal neutron detector count ratio threshold. If the result is yes, the target apparent aperture acquisition strategy is to calculate the apparent aperture based on the density-containing inversion formula between the thermal neutron detector count ratio and the apparent aperture. If the result is no, the target apparent aperture acquisition strategy is to calculate the apparent aperture based on the density-free inversion formula between the thermal neutron detector count ratio and the apparent aperture.

[0045] Furthermore, the relationship between apparent porosity and corrected porosity corresponding to a single environmental factor is as follows: The apparent porosity correction formula for a single environmental factor is: Where φ′ represents the corrected porosity, φ a For apparent porosity, A, B, C, and D are correction coefficients;

[0046] The calibration module is specifically used to: when the environmental factor associated with the well logging is a single environmental factor, to calibrate the specific value of the apparent porosity according to the apparent porosity calibration formula corresponding to the single environmental factor, and to preset the specific value of the calibration porosity of the formation.

[0047] Furthermore, the calibration module is also specifically used for:

[0048] Data fitting was performed on multiple sets of one-to-one corresponding apparent porosity and corrected porosity under the influence of a single environmental factor to obtain the specific values ​​of A, B, C and D under the influence of a single environmental factor.

[0049] Furthermore, the calibration module is also specifically used for:

[0050] When the environmental factors associated with well logging are multiple environmental factors, and when the judgment result is yes, calculate the total correction amount corresponding to the multiple environmental factors, and determine the specific value of the corrected porosity by summing the total correction amount corresponding to the multiple environmental factors and the specific value of the apparent porosity.

[0051] Furthermore, the process by which the correction module calculates the total correction amount corresponding to multiple environmental factors includes:

[0052] When there are two environmental factors with a strong coupling relationship among multiple environmental factors, the correction amount corresponding to the two environmental factors can be calculated by using the relationship between the apparent porosity and the corrected porosity of the two environmental factors.

[0053] Using the aperture correction formula corresponding to each environmental factor that does not have a strong coupling relationship, the correction amount corresponding to each environmental factor that does not have a strong coupling relationship is calculated;

[0054] The sum of the correction values ​​for each pair of environmental factors with strong coupling and the correction values ​​for each environmental factor without strong coupling is taken as the total correction value for multiple environmental factors.

[0055] Furthermore, the correction module is specifically used for: when the judgment result is negative, calculating the correction amount corresponding to each environmental factor, sorting the multiple environmental factors in descending order of correction amount, taking the specific value of the corrected porosity corresponding to the first single environmental factor as the specific value of the apparent porosity corresponding to the second single environmental factor, calculating the specific value of the corrected porosity corresponding to the second single environmental factor, taking the specific value of the corrected porosity corresponding to the second single environmental factor as the specific value of the apparent porosity corresponding to the third single environmental factor, calculating the specific value of the corrected porosity corresponding to the third single environmental factor, and after traversing all environmental factors, taking the specific value of the last calculated corrected porosity as the specific value of the corrected porosity of the preset formation.

[0056] 3) In a third aspect, the present invention also provides a computer device, the computer device including a processor coupled to a memory, the memory storing at least one computer program, the at least one computer program being loaded and executed by the processor to enable the computer device to implement any of the above-mentioned environmental correction methods for formation porosity.

[0057] 4) In a fourth aspect, the present invention also provides a computer-readable storage medium storing at least one computer program, which is loaded and executed by a processor to enable a computer to implement any of the above-described environmental correction methods for formation porosity.

[0058] It should be noted that the beneficial effects of the technical solutions of the second to fourth aspects of the present invention and their corresponding possible implementations can be found in the above description of the technical effects of the first aspect and its corresponding possible implementations, and will not be repeated here. Attached Figure Description

[0059] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0060] Figure 1 This is a schematic flowchart of an environmental correction method for formation porosity according to an embodiment of the present invention;

[0061] Figure 2 The response curve of the thermal neutron detector count ratio R versus porosity φ under standard porosity well conditions;

[0062] Figure 3 This is a schematic diagram of the structure of an environmental correction system for formation porosity according to an embodiment of the present invention;

[0063] Figure 4 This is a schematic diagram of the structure of a computer device according to an embodiment of the present invention. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0065] like Figure 1 As shown, an environmental correction method for formation porosity according to an embodiment of the present invention includes the following steps:

[0066] S1. When logging using a neutron porosity logging instrument, obtain the specific value of the thermal neutron detector count ratio of the preset formation;

[0067] The preset formation can be understood as: the formation at a preset depth from the wellhead, such as the formation 500 meters from the wellhead.

[0068] S2. Correct the specific value of the thermal neutron detector count ratio of the preset formation to obtain the corrected specific value of the thermal neutron detector count ratio.

[0069] S3. Determine the target apparent porosity acquisition strategy corresponding to the specific value of the corrected thermal neutron detector count ratio. Based on the target apparent porosity acquisition strategy and the specific value of the corrected thermal neutron detector count ratio, calculate the specific value of the apparent porosity of the preset formation.

[0070] S4. Based on the specific value of apparent porosity and the relationship between apparent porosity and corrected porosity corresponding to environmental factors associated with well logging, determine the specific value of corrected porosity for the preset formation.

[0071] Optionally, in S2, the specific value of the thermal neutron detector count ratio of the preset formation is corrected to obtain the corrected specific value of the thermal neutron detector count ratio, including:

[0072] S20. The specific value R of the thermal neutron detector count ratio of the preset formation is corrected using the correction formula to obtain the corrected specific value R′ of the thermal neutron detector count ratio. The correction formula is as follows: Where r1 is the source distance of the near-thermal neutron detector of the neutron porosity logging instrument, and r2 is the source distance of the far-thermal neutron detector of the neutron porosity logging instrument. L′ f Indicates: Corrected fast neutron deceleration length, L f For the fast neutron deceleration length, L0 represents the deceleration length L of fast neutrons during inelastic scattering under pure water conditions. f The amount of contribution, E′ is the initial energy of the fast neutron, E″ is the average energy of the neutron after inelastic scattering, and ζ H Σ represents the average logarithmic energy loss of hydrogen. in_O It is the inelastic scattering cross section of oxygen, Σ el_H It is the elastic scattering cross section of hydrogen. R is derived from the two-group diffusion theory.

[0073] Optionally, in S3, determining the target apparent aperture acquisition strategy corresponding to the specific value of the corrected thermal neutron detector count ratio includes:

[0074] S30. Determine whether the specific value of the corrected thermal neutron detector count ratio exceeds the preset thermal neutron detector count ratio threshold, and obtain the judgment result. When the judgment result is yes, the target apparent aperture acquisition strategy is: calculate the apparent aperture based on the density-containing inversion formula between the thermal neutron detector count ratio and the apparent aperture. When the judgment result is no, the target apparent aperture acquisition strategy is: calculate the apparent aperture based on the density-free inversion formula between the thermal neutron detector count ratio and the apparent aperture.

[0075] The environmental correction method for formation porosity of the present invention is carried out on the basis of apparent porosity inversion. Figure 2 This is the response curve of a thermal neutron detector count ratio R versus porosity φ under standard porosity well conditions. Based on the definition of relative porosity sensitivity, The response curve shows a high sensitivity S in the low porosity region, which can meet the requirements of porosity logging; however, the sensitivity S is low in the high porosity region and cannot meet the requirements of porosity logging.

[0076] To meet the requirements of neutron porosity measurement, this invention employs different target apparent porosity acquisition strategies based on the relationship between the specific value of the corrected thermal neutron detector count ratio and a preset thermal neutron detector count ratio threshold. For example... Figure 2 In this method, a preset thermal neutron detector count ratio threshold can be set to 2.2. When the corrected thermal neutron detector count ratio exceeds the preset threshold, the target apparent porosity acquisition strategy is as follows: Apparent porosity is calculated based on the density-containing inversion formula between the thermal neutron detector count ratio and apparent porosity. This target apparent porosity acquisition strategy can be called the apparent porosity inversion method based on the density-containing inversion formula. When the thermal neutron detector count ratio does not exceed the preset threshold, the target apparent porosity acquisition strategy is as follows: Apparent porosity is calculated based on the density-free inversion formula between the thermal neutron detector count ratio and apparent porosity. This target apparent porosity acquisition strategy can be called the apparent porosity inversion method based on the density-free inversion formula. The two apparent porosity acquisition strategies are used in combination in segments. One of the apparent porosity acquisition strategies is selected as the target apparent porosity acquisition strategy according to the actual situation to calculate the specific value of the apparent porosity of the preset formation.

[0077] It should be noted that the preset thermal neutron detector count ratio threshold can be set according to the actual situation.

[0078] The process of obtaining the density-free inversion formula and the density-containing inversion formula is as follows:

[0079] 1) In low porosity regions, based on the response curve of porosity φ and the thermal neutron detector count ratio R″, a density-free inversion formula for porosity φ, φ = f(R″), was established. This density-free inversion formula is only applicable to low porosity regions with high sensitivity. Specifically, the density-free inversion formula is the low formation porosity model in the invention patent entitled "A Neutron Logging Method, System, and Electronic Equipment for Measuring Formation Porosity" (Publication No.: CN116029128A, Application No.: 202310008812.X).

[0080] 2) In high porosity regions, to achieve apparent porosity inversion, density correction is introduced, and a density-inverted formula for porosity φ, φ = f(ρ, R″), is established. In this formula, porosity φ is a function of the thermal neutron detector count ratio R″ and the formation density ρ. Apparent porosity inversion requires formation density data. This inversion formula is applicable to all porosity regions, especially high porosity regions. Specifically, the density-inverted formula is the high formation porosity model in the invention patent entitled "A Neutron Logging Method, System, and Electronic Equipment for Measuring Formation Porosity" (Publication No.: CN116029128A, Application No.: 202310008812.X).

[0081] Optionally, in the above technical solution, the relationship between the apparent aperture and the corrected aperture corresponding to a single environmental factor is as follows: The apparent aperture correction formula for a single environmental factor is: Where φ′ represents the corrected porosity, φ a For apparent porosity, A, B, C, and D are correction coefficients, and each of A, B, C, and D is a function of a single environmental factor.

[0082] In S4, based on the specific value of apparent porosity and the relationship between apparent porosity and corrected porosity corresponding to well logging-related environmental factors, the specific value of corrected porosity for the preset formation is determined, including:

[0083] S40. When the environmental factor associated with well logging is a single environmental factor, the specific value of the apparent porosity is calibrated according to the apparent porosity correction formula corresponding to the single environmental factor, and the specific value of the corrected porosity of the preset formation is determined.

[0084] Optionally, in the above technical solution, the process of obtaining the specific values ​​of A, B, C, and D includes:

[0085] Data fitting is performed on multiple sets of one-to-one corresponding apparent porosity and corrected porosity under the influence of each single environmental factor to obtain the specific values ​​of A, B, C and D under the influence of each single environmental factor. For example, orthogonal polynomial regression method can be used to fit data on multiple sets of one-to-one corresponding apparent porosity and corrected porosity under the influence of each single environmental factor, or other data fitting methods can be used.

[0086] Among these, multiple environmental factors include well diameter, lithology, well fluid salinity, formation water salinity, mud density, mud cake thickness, gaps, and formation temperature. When environmental factors differ from standard calibration conditions, the apparent porosity directly measured by the logging instrument deviates from the actual porosity of the formation. For example, when two or more environmental factors deviate from standard well conditions simultaneously, multi-environmental comprehensive correction should be performed.

[0087] Among them, the multiple sets of one-to-one corresponding apparent aperture and corrected aperture under the influence of a single environmental factor refer to the multiple sets of one-to-one corresponding apparent aperture and corrected aperture under the influence of only one environmental factor. The apparent aperture correction formula corresponding to a single environmental factor refers to the apparent aperture correction formula obtained by fitting when only one environmental element is involved. Therefore:

[0088] Each individual environmental factor corresponds to a set of specific values ​​for A, B, C, and D. Substitute the specific values ​​of A, B, C, and D corresponding to each individual environmental factor into... The aperture correction formula corresponding to each single environmental factor is obtained.

[0089] Optionally, in S4, determining the specific value of the corrected porosity of the preset formation based on the specific value of the apparent porosity and the relationship between the apparent porosity and the corrected porosity corresponding to the environmental factors associated with well logging, further includes:

[0090] S41. When the environmental factors associated with well logging are multiple environmental factors, and when the judgment result is yes, calculate the total correction amount corresponding to the multiple environmental factors, and determine the specific value of the corrected porosity by summing the total correction amount corresponding to the multiple environmental factors and the specific value of the apparent porosity.

[0091] Optionally, in S41, the process of calculating the total correction amount corresponding to multiple environmental factors includes:

[0092] S410. When there are two environmental factors with a strong coupling relationship among multiple environmental factors, the correction amount corresponding to the two environmental factors is calculated by using the relationship between the apparent porosity and the corrected porosity of the two environmental factors.

[0093] Various environmental factors collectively influence porosity measurement results, and there is a certain degree of coupling between different environmental factors. The coupling process of multiple environments is very complex. In order to achieve multi-environment correction, multiple environmental factors should be decoupled. First, it is necessary to determine whether there are two environmental factors with a strong coupling relationship. If there is a strong coupling relationship between two environmental factors, the mutual influence between the two environmental factors cannot be ignored.

[0094] The process for determining whether two environmental factors in a multi-environment environment have a strong coupling relationship is as follows:

[0095] Let's take any two environmental factors as an example, denoted as environmental factor E. i and environmental factors E j Let environmental factor E i and environmental factors E j The parameter values ​​range from [a0, a′] to [b0, b′]. The apparent porosity of the two environmental factors under different parameter conditions are φ(a′, b′), φ(a′, b0), φ(a0, b′), and φ(a0, b0), respectively. Δ is the measurement error of the neutron porosity logging tool. The parameter γ is defined to measure the environmental factor E. i and environmental factors E j The degree of coupling between them, where:

[0096]

[0097] If γ < 1, then environmental factor E is determined. i and environmental factors E j There is no strong coupling relationship between them. If γ≥1, the environmental factor E is determined to be... i and environmental factors E j There is a strong coupling relationship between them.

[0098] The specific process for calculating the correction amount corresponding to any two environmental factors with a strong coupling relationship, based on the relationship between the apparent porosity and the corrected porosity, is as follows:

[0099] The relationship between the apparent porosity and the corrected porosity for any two environmental factors with a strong coupling relationship is: Coupled Environment Correction Formula. The Coupled Environment Correction Formula for any two environmental factors with a strong coupling relationship is: Where φ″ represents the corrected porosity, φ a For apparent porosity, A mn B mn C mn D mn A is the correction factor. mn B mn C mnD mn All are environmental factors E m and environmental factors E n The function of environmental factors E m and environmental factors E n For any two environmental factors that have a strong coupling relationship.

[0100] It should be noted that orthogonal polynomial regression was used to fit multiple sets of one-to-one corresponding apparent porosity and corrected porosity under the influence of any two environmental factors with strong coupling to obtain A. mn B mn C mn D mn The specific values ​​can be understood as follows: each pair of environmental factors with a strong coupling relationship corresponds to a set of A. mn B mn C mn D mn The specific values ​​are determined by assigning a set of A values ​​to each pair of environmental factors with strong coupling relationships. mn B mn C mn D mn Substitute the specific value into We obtain the coupling environment correction formula for each pair of environmental factors with strong coupling relationship.

[0101] The correction value corresponding to any two environmental factors that have a strong coupling relationship is:

[0102] Substitute the specific value of the apparent porosity into the coupling environment correction formula corresponding to the two environmental factors to obtain the specific value of the corrected porosity corresponding to the two environmental factors. The difference between the specific value of the corrected porosity corresponding to the two environmental factors and the specific value of the apparent porosity is the correction amount corresponding to the two environmental factors. Continue until the correction amount corresponding to any two environmental factors with a strong coupling relationship is obtained.

[0103] S411. Using the aperture correction formula corresponding to each environmental factor that does not have a strong coupling relationship, calculate the correction amount corresponding to each environmental factor that does not have a strong coupling relationship.

[0104] Among them, the porosity correction formula for any environmental factor that does not have a strong coupling relationship is: the porosity correction formula obtained only when the environmental factor that does not have a strong coupling relationship is affected. For example, when the environmental factor that does not have a strong coupling relationship is mud density, the porosity correction formula corresponding to mud density is obtained only when the mud density is affected.

[0105] The correction value for any environmental factor that does not have a strong coupling relationship is:

[0106] Substitute the specific value of the apparent porosity into the apparent porosity correction formula corresponding to the single environmental factor (the influence of the environmental factor that does not have a strong coupling relationship exists) to obtain the specific value of the corrected porosity corresponding to the environmental factor that does not have a strong coupling relationship. The difference between the specific value of the corrected porosity corresponding to the environmental factor that does not have a strong coupling relationship and the specific value of the apparent porosity is the correction amount corresponding to the environmental factor that does not have a strong coupling relationship. Continue until the correction amount corresponding to each environmental factor that does not have a strong coupling relationship is obtained.

[0107] S412. The sum of the correction values ​​corresponding to the two environmental factors with strong coupling relationship and the correction values ​​corresponding to the environmental factors without strong coupling relationship is taken as the total correction value for multiple environmental factors.

[0108] Optionally, in S4, determining the specific value of the corrected porosity of the preset formation based on the specific value of the apparent porosity and the relationship between the apparent porosity and the corrected porosity corresponding to the environmental factors associated with well logging, further includes:

[0109] When the judgment result is negative, the correction amount corresponding to each environmental factor is calculated. The multiple environmental factors are sorted in descending order of correction amount. The specific value of the corrected porosity corresponding to the first single environmental factor is used as the specific value of the apparent porosity corresponding to the second single environmental factor. The specific value of the corrected porosity corresponding to the second single environmental factor is calculated. The specific value of the corrected porosity corresponding to the second single environmental factor is used as the specific value of the apparent porosity corresponding to the third single environmental factor. The specific value of the corrected porosity corresponding to the third single environmental factor is calculated. After traversing all environmental factors, the specific value of the last calculated corrected porosity is used as the specific value of the corrected porosity of the preset formation.

[0110] The specific value of the corrected porosity corresponding to each single environmental factor is calculated using the corresponding apparent porosity correction formula for that single environmental factor.

[0111] The correction amount for each environmental factor is specifically calculated with reference to S411. The specific value of the apparent porosity is substituted into the apparent porosity correction formula for each environmental factor under a single environmental factor to calculate the specific value of the corrected porosity for each environmental factor. The difference between the corrected porosity and the specific value of the apparent porosity is then calculated to obtain the correction amount for each environmental factor.

[0112] In another embodiment, multiple environmental factors are sorted in descending order of correction amount, and the priority of each environmental factor is set sequentially according to the sorting sequence, with the environmental factor with the largest correction amount set as the highest priority.

[0113] When multiple environmental factors are involved, the error of environmental correction can be reduced by adjusting the correction order. Multi-environment sequential correction requires first prioritizing each environmental factor, and then performing environmental corrections sequentially according to priority from highest to lowest using single-environment or coupled-environment correction formulas to obtain a corrected porosity that approximates the true porosity.

[0114] The following embodiments provide data support for the present invention:

[0115] Using porosity measurement under the influence of five environmental factors as an example, this paper illustrates the implementation process and applicable scope of independent correction based on density inversion formula and sequential correction based on density-free inversion formula. Table 1 shows the correction results of this example. The values ​​of each environmental factor in this example are as follows:

[0116] Group 1: Well diameter 250mm, sandstone, well fluid salinity 100ppm, formation salinity 100ppm, mud density 1.4g / cm³ 3 ;

[0117] Group 2: Sandstone, well fluid salinity 150 ppm, mud density 1.4 g / cm³ 3 10mm thick mud cake, 150℃ temperature;

[0118] Group 3: 150mm well diameter, sandstone, formation mineralization of 150ppm, mud cake thickness of 15mm, and gap of 19mm.

[0119] Table 1 shows the results obtained using the present invention.

[0120] Table 1:

[0121]

[0122]

[0123] In the above embodiments, although the steps are numbered S1, S2, etc., they are only specific embodiments given by the present invention. Those skilled in the art can adjust the execution order of S1, S2, etc. according to the actual situation, which is also within the protection scope of the present invention. It can be understood that in some embodiments, some or all of the above embodiments may be included.

[0124] like Figure 3 As shown, an environmental correction system 200 for formation porosity according to an embodiment of the present invention includes an acquisition module 201, a correction module 202, a determination module 203, a calculation module 204, and a correction module 205.

[0125] The acquisition module 201 is used to: obtain the specific value of the thermal neutron detector count ratio of a preset formation when logging using a neutron porosity logging instrument;

[0126] The correction module 202 is used to: correct the specific value of the thermal neutron detector count ratio of the preset formation to obtain the corrected specific value of the thermal neutron detector count ratio;

[0127] The determination module 203 is used to: determine the target apparent aperture acquisition strategy corresponding to the specific value of the corrected thermal neutron detector count ratio;

[0128] The calculation module 204 is used to: calculate the specific value of the apparent porosity of the preset formation based on the target apparent porosity acquisition strategy and the specific value of the corrected thermal neutron detector count ratio;

[0129] The correction module 205 is used to determine the specific value of the corrected porosity of the preset formation based on the specific value of the apparent porosity and the relationship between the apparent porosity and the corrected porosity corresponding to the environmental factors associated with well logging.

[0130] Based on the above scheme, the formation porosity environmental correction system of the present invention can be further improved as follows.

[0131] Optionally, in the above technical solution, the correction module 202 is specifically used for:

[0132] The specific value R of the thermal neutron detector count ratio of the preset formation is corrected using a correction formula to obtain the corrected specific value R′ of the thermal neutron detector count ratio. The correction formula is as follows: Where r1 is the source distance of the near-thermal neutron detector of the neutron porosity logging instrument, and r2 is the source distance of the far-thermal neutron detector of the neutron porosity logging instrument. L′ f Indicates: Corrected fast neutron deceleration length, L f For the fast neutron deceleration length, L0 represents the deceleration length L of fast neutrons during inelastic scattering under pure water conditions. f The amount of contribution, E′ is the initial energy of the fast neutron, E″ is the average energy of the neutron after inelastic scattering, and ζ H Σ represents the average logarithmic energy loss of hydrogen. in_O It is the inelastic scattering cross section of oxygen, Σ el_H It is the elastic scattering cross section of hydrogen.

[0133] Optionally, in the above technical solution, the determining module 203 is specifically used for:

[0134] The system determines whether the corrected thermal neutron detector count ratio exceeds a preset thermal neutron detector count ratio threshold. If the result is yes, the target apparent aperture acquisition strategy is to calculate the apparent aperture based on the density-containing inversion formula between the thermal neutron detector count ratio and the apparent aperture. If the result is no, the target apparent aperture acquisition strategy is to calculate the apparent aperture based on the density-free inversion formula between the thermal neutron detector count ratio and the apparent aperture.

[0135] Optionally, in the above technical solution, the relationship between the apparent aperture and the corrected aperture corresponding to a single environmental factor is as follows: The apparent aperture correction formula for a single environmental factor is: Where φ′ represents the corrected porosity, φ a For apparent porosity, A, B, C, and D are correction coefficients;

[0136] The calibration module 205 is specifically used to: when the environmental factor associated with the well logging is a single environmental factor, to calibrate the specific value of the apparent porosity according to the apparent porosity calibration formula corresponding to the single environmental factor, and to determine the specific value of the calibration porosity of the preset formation.

[0137] Optionally, in the above technical solution, the calibration module 205 is further specifically used for:

[0138] Data fitting was performed on multiple sets of one-to-one corresponding apparent porosity and corrected porosity under the influence of a single environmental factor to obtain the specific values ​​of A, B, C and D under the influence of a single environmental factor.

[0139] Optionally, in the above technical solution, the calibration module 205 is further specifically used for:

[0140] When the environmental factors associated with well logging are multiple environmental factors, and when the judgment result is yes, calculate the total correction amount corresponding to the multiple environmental factors, and determine the specific value of the corrected porosity by summing the total correction amount corresponding to the multiple environmental factors and the specific value of the apparent porosity.

[0141] Optionally, in the above technical solution, the process by which the correction module 205 calculates the total correction amount corresponding to multiple environmental factors includes:

[0142] When there are two environmental factors with a strong coupling relationship among multiple environmental factors, the correction amount corresponding to the two environmental factors can be calculated by using the relationship between the apparent porosity and the corrected porosity of the two environmental factors.

[0143] Using the aperture correction formula corresponding to each environmental factor that does not have a strong coupling relationship, the correction amount corresponding to each environmental factor that does not have a strong coupling relationship is calculated;

[0144] The sum of the correction values ​​for each pair of environmental factors with strong coupling and the correction values ​​for each environmental factor without strong coupling is taken as the total correction value for multiple environmental factors.

[0145] Optionally, in the above technical solution, the correction module 205 is further specifically used for: when the judgment result is negative, calculating the correction amount corresponding to each environmental factor, sorting the multiple environmental factors in descending order of correction amount, taking the specific value of the correction porosity corresponding to the first single environmental factor as the specific value of the apparent porosity corresponding to the second single environmental factor, calculating the specific value of the correction porosity corresponding to the second single environmental factor, taking the specific value of the correction porosity corresponding to the second single environmental factor as the specific value of the apparent porosity corresponding to the third single environmental factor, calculating the specific value of the correction porosity corresponding to the third single environmental factor, and after traversing all environmental factors, taking the specific value of the last calculated correction porosity as the specific value of the correction porosity of the preset formation.

[0146] It should be noted that the beneficial effects of the formation porosity environmental correction system 200 provided in the above embodiments are the same as those of the formation porosity environmental correction method described above, and will not be repeated here. Furthermore, the system provided in the above embodiments is only illustrated by the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the system can be divided into different functional modules according to the actual situation to complete all or part of the functions described above. In addition, the system and method embodiments provided in the above embodiments belong to the same concept, and their specific implementation process is detailed in the method embodiments, and will not be repeated here.

[0147] like Figure 4 As shown, an embodiment of the present invention provides a computer device 300, which includes a processor 320 coupled to a memory 310. The memory 310 stores at least one computer program 330, which is loaded and executed by the processor 320 to enable the computer device 300 to implement any of the above-mentioned formation porosity environmental correction methods. Specifically:

[0148] The computer device 300 can vary considerably due to differences in configuration or performance. It may include one or more processors 320 (Central Processing Units, CPUs) and one or more memories 310. The one or more memories 310 store at least one computer program 330, which is loaded and executed by the one or more processors 320 to enable the computer device 300 to implement any of the formation porosity environmental correction methods provided in the above embodiments. Of course, the computer device 300 may also have wired or wireless network interfaces, a keyboard, and input / output interfaces for input and output. The computer device 300 may also include other components for implementing device functions, which will not be elaborated upon here.

[0149] An embodiment of the present invention provides a computer-readable storage medium storing at least one computer program, which is loaded and executed by a processor to enable a computer to implement any of the above-described environmental correction methods for formation porosity.

[0150] Alternatively, the computer-readable storage medium may be a read-only memory (ROM), a random access memory (RAM), a compact disc read-only memory (CD-ROM), magnetic tape, a floppy disk, and an optical data storage device, etc.

[0151] In an exemplary embodiment, a computer program product or computer program is also provided, which includes computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform any of the aforementioned formation porosity environmental correction methods.

[0152] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and represent a limitation on a specific order or sequence. Where appropriate, the order of use for similar objects can be interchanged so that the embodiments of this application described herein can be implemented in an order other than that shown or described.

[0153] Those skilled in the art will recognize that this invention can be implemented as a system, method, or computer program product. Therefore, this invention can be specifically implemented in the following forms: it can be entirely hardware, entirely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software, generally referred to herein as a "circuit," "module," or "system." Furthermore, in some embodiments, this invention can also be implemented as a computer program product contained in one or more computer-readable media, which includes computer-readable program code.

[0154] Any combination of one or more computer-readable media can be used. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0155] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An environmental correction method for formation porosity, characterized in that, include: When logging using a neutron porosity logging instrument, the specific value of the thermal neutron detector count ratio of the preset formation is obtained; The specific value of the thermal neutron detector count ratio of the preset formation is corrected to obtain the corrected specific value of the thermal neutron detector count ratio. Determine the target apparent porosity acquisition strategy corresponding to the specific value of the corrected thermal neutron detector count ratio, and calculate the specific value of the apparent porosity of the preset formation based on the target apparent porosity acquisition strategy and the specific value of the corrected thermal neutron detector count ratio. Based on the specific value of the apparent porosity and the relationship between the apparent porosity and the corrected porosity corresponding to the environmental factors associated with well logging, the specific value of the corrected porosity of the preset formation is determined. The specific value of the thermal neutron detector count ratio of the preset formation is corrected to obtain the corrected specific value of the thermal neutron detector count ratio, including: The specific value of the thermal neutron detector count ratio for the preset formation is obtained using the correction formula. The correction is performed to obtain the specific value of the corrected thermal neutron detector count ratio. The corrected formula is: ,in, The source distance of the near-thermal neutron detector in the neutron porosity logging instrument is given. The source distance of the far-thermal neutron detector in the neutron porosity logging instrument is [missing information]. , Indicates: the corrected fast neutron deceleration length. For the fast neutron deceleration length, , Represents: the deceleration length of fast neutrons by inelastic scattering under pure water conditions. The amount of contribution, , The initial energy of the fast neutron. The average energy of the neutron after inelastic scattering. The average logarithmic energy loss of hydrogen. It is the inelastic scattering cross section of oxygen. It is the elastic scattering cross section of hydrogen. .

2. The environmental correction method for formation porosity according to claim 1, characterized in that, Determining the target aperture acquisition strategy corresponding to the specific value of the corrected thermal neutron detector count ratio includes: The system determines whether the specific value of the corrected thermal neutron detector count ratio exceeds a preset thermal neutron detector count ratio threshold, and obtains a determination result. When the determination result is yes, the target aperture acquisition strategy is: to calculate the aperture based on the density-containing inversion formula between the thermal neutron detector count ratio and the aperture. When the determination result is no, the target aperture acquisition strategy is: to calculate the aperture based on the density-free inversion formula between the thermal neutron detector count ratio and the aperture.

3. The environmental correction method for formation porosity according to claim 2, characterized in that, The relationship between apparent porosity and corrected porosity corresponding to a single environmental factor is as follows: The apparent porosity correction formula for a single environmental factor is: ,in, Indicates corrected porosity. For apparent porosity, , , and All are correction factors; Based on the specific value of the apparent porosity and the relationship between apparent porosity and corrected porosity corresponding to environmental factors associated with well logging, the specific value of the corrected porosity of the preset formation is determined, including: When the environmental factor associated with well logging is a single environmental factor, the specific value of the apparent porosity is calibrated according to the apparent porosity correction formula corresponding to the single environmental factor, and the specific value of the corrected porosity of the preset formation is determined.

4. The environmental correction method for formation porosity according to claim 3, characterized in that, , , and The process of obtaining the specific value includes: Data fitting was performed on multiple sets of one-to-one corresponding apparent porosity and corrected porosity under the influence of a single environmental factor to obtain the porosity under the influence of a single environmental factor. , , and The specific value.

5. The environmental correction method for formation porosity according to claim 4, characterized in that, Based on the specific value of the apparent porosity and the relationship between the apparent porosity and the corrected porosity corresponding to the environmental factors associated with well logging, the specific value of the corrected porosity of the preset formation is determined, which also includes: When the environmental factors associated with well logging are multiple environmental factors, and when the judgment result is yes, the total correction amount corresponding to the multiple environmental factors is calculated, and the sum of the total correction amount corresponding to the multiple environmental factors and the specific value of the apparent porosity is determined as the specific value of the corrected porosity.

6. The environmental correction method for formation porosity according to claim 5, characterized in that, The process of calculating the total correction for multiple environmental factors includes: When there are two environmental factors with a strong coupling relationship among multiple environmental factors, the correction amount corresponding to the two environmental factors can be calculated by using the relationship between the apparent porosity and the corrected porosity of the two environmental factors. Using the aperture correction formula corresponding to each environmental factor that does not have a strong coupling relationship, the correction amount corresponding to each environmental factor that does not have a strong coupling relationship is calculated; The sum of the correction values ​​for each pair of environmental factors with strong coupling and the correction values ​​for each environmental factor without strong coupling is taken as the total correction value for multiple environmental factors.

7. The environmental correction method for formation porosity according to claim 6, characterized in that, Based on the specific value of the apparent porosity and the relationship between the apparent porosity and the corrected porosity corresponding to the environmental factors associated with well logging, the specific value of the corrected porosity of the preset formation is determined, which also includes: When the judgment result is negative, the correction amount corresponding to each environmental factor is calculated. The multiple environmental factors are sorted in descending order of correction amount. The specific value of the corrected porosity corresponding to the first single environmental factor is used as the specific value of the apparent porosity corresponding to the second single environmental factor. The specific value of the corrected porosity corresponding to the second single environmental factor is calculated. The specific value of the corrected porosity corresponding to the second single environmental factor is used as the specific value of the apparent porosity corresponding to the third single environmental factor. The specific value of the corrected porosity corresponding to the third single environmental factor is calculated. After traversing all environmental factors, the specific value of the last calculated corrected porosity is used as the specific value of the corrected porosity of the preset formation.

8. An environmental correction system for formation porosity, characterized in that, It includes an acquisition module, a correction module, a determination module, a calculation module, and a calibration module; The acquisition module is used to: obtain the specific value of the thermal neutron detector count ratio of a preset formation when logging using a neutron porosity logging instrument; The correction module is used to: correct the specific value of the thermal neutron detector count ratio of the preset stratum, and obtain the corrected specific value of the thermal neutron detector count ratio; The determining module is used to: determine the target aperture acquisition strategy corresponding to the specific value of the corrected thermal neutron detector count ratio; The calculation module is used to: calculate the specific value of the apparent porosity of the preset stratum based on the target apparent porosity acquisition strategy and the specific value of the corrected thermal neutron detector count ratio; The correction module is used to: determine the specific value of the corrected porosity of the preset formation based on the specific value of the apparent porosity and the relationship between the apparent porosity and the corrected porosity corresponding to the environmental factors associated with well logging; The correction module is specifically used for: The specific value of the thermal neutron detector count ratio for the preset formation is obtained using the correction formula. After correction, the specific value of the corrected thermal neutron detector count ratio is obtained. The corrected formula is: ,in, The source distance of the near-thermal neutron detector in a neutron porosity logging instrument. The source distance of the far-thermal neutron detector in the neutron porosity logging instrument. , Indicates: the corrected fast neutron deceleration length. For the fast neutron deceleration length, , Represents: the deceleration length of fast neutrons by inelastic scattering under pure water conditions. The amount of contribution, , The initial energy of the fast neutron. The average energy of the neutron after inelastic scattering. The average logarithmic energy loss of hydrogen. It is the inelastic scattering cross section of oxygen. It is the elastic scattering cross section of hydrogen. .

9. A computer device, characterized in that, The computer device includes a processor coupled to a memory storing at least one computer program, which is loaded and executed by the processor to enable the computer device to implement an environmental correction method for formation porosity as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores at least one computer program, which is loaded and executed by a processor to enable the computer to implement an environmental correction method for formation porosity as described in any one of claims 1 to 7.

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