Calculation method and device for porosity of tight gas formations

Abstract

The present application provides a method and device for calculating the porosity of a tight gas formation, which can improve the accuracy of porosity calculation and help reduce the difficulty of oil and gas development in tight gas formations. The method includes: obtaining first parameters of the tight gas formation based on multiple nuclear logging methods, the first parameters including the formation capture cross section, formation density, apparent hydrogen index, formation element content, and formation thermal neutron cross section; selecting parameters that satisfy a linear volume physics model from the first parameters to obtain second parameters, the second parameters including at least one of the formation capture cross section, formation density, apparent hydrogen index, or formation thermal neutron cross section; constructing a porosity response equation based on the second parameters and a shale content parameter of the tight gas formation, the shale content parameter being determined based on the formation composition of the tight gas formation; and solving the porosity response equation to obtain the porosity.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas exploration, and in particular to a method and device for calculating the porosity of tight gas formations. Background Art

[0002] Oil and gas development refers to the economic activity of building production capacity and producing oil and gas from proven oil and gas fields. Currently, the reservoirs explored for oil and gas reserves are mostly tight gas formations, making oil and gas development more difficult.

[0003] At present, most models constructed with multi-core logging parameters are used to calculate the porosity of tight gas formations. However, the porosity of tight gas formations is relatively low, and many nuclear logging parameters are not sensitive to changes in porosity, that is, the obtained porosity accuracy is not high. As a result, the application of porosity calculation methods based on models constructed with multi-core logging parameters in tight gas formations is not ideal. Summary of the Invention

[0004] The present application provides a method and device for calculating the porosity of tight gas formations, which can improve the accuracy of calculated porosity and help reduce the difficulty of oil and gas development in tight gas formations.

[0005] In the first aspect, the present application provides a method for calculating the porosity of a tight gas formation, the method comprising: obtaining a first parameter of the tight gas formation based on a plurality of nuclear logging methods, the first parameter including the formation capture cross section, formation density, apparent hydrogen index, formation element content, and formation thermal neutron cross section; selecting a parameter satisfying a linear volume physics model from the first parameter to obtain a second parameter, the second parameter including at least one of the formation capture cross section, formation density, apparent hydrogen index, or formation thermal neutron cross section; constructing a porosity response equation based on the second parameter and the mud content parameter of the tight gas formation, the mud content parameter being determined based on the formation components of the tight gas formation; solving the porosity response equation to obtain the porosity.

[0006] The method for calculating the porosity of tight gas formations provided in the embodiments of the present application selects parameters that satisfy the linear volume physics model from a variety of nuclear logging parameters, removes parameters that are insensitive to porosity, and determines mud content parameters based on the formation components of the tight gas formation. This further optimizes the parameters for constructing the porosity response equation, improves the accuracy of the porosity calculation, and helps reduce the difficulty of oil and gas development in tight gas formations.

[0007] In conjunction with the first aspect, in certain implementations of the first aspect, the multiple nuclear logging methods include neutron lifetime logging, pulsed neutron density logging, pulsed thermal neutron porosity logging, geo-element logging, and thermal neutron cross-section logging. The formation capture cross section is obtained based on the neutron lifetime logging method; the formation density is obtained based on the pulsed neutron density logging method; the apparent hydrogen index is obtained based on the pulsed thermal neutron porosity logging method; the formation element content is obtained based on the geo-element logging method; and the formation thermal neutron cross section is obtained based on the thermal neutron cross-section logging method.

[0008] In conjunction with the first aspect, in certain implementations of the first aspect, the porosity response equation is expressed by the following formula:

[0009]

[0010] in, is the porosity, s g is the gas saturation, V ma 、V sh 、V w and V g are the volume of stratum skeleton, mud, water in porosity and gas in pores, Σ ma ,Σ sh ,Σ w and Σ g are the macroscopic capture cross sections of formation skeleton, mud, water in porosity and gas in pores, respectively; ρ ma , ρ sh , ρ w and ρ g are the volume densities of the formation skeleton, mud, water in porosity, and gas in pores; HI ma , HI sh , HI w and HI g are the hydrogen index of the formation skeleton, mud, water in porosity and gas in pores, TNXS ma 、TNXS sh 、TNXS w and TNXS g are the thermal neutron cross sections of the formation skeleton, mud, water in porosity, and gas in pores, respectively. a ,Σ,ρ b and TNXS are apparent hydrogen index, formation capture cross section, formation density and formation thermal neutron cross section, respectively.

[0011] In combination with the first aspect, in certain implementations of the first aspect, solving the porosity response equation to obtain the porosity includes: solving the porosity response equation based on a weighted least squares method to obtain the porosity.

[0012] In combination with the first aspect, in certain implementations of the first aspect, the method further includes: performing error analysis on the porosity based on a Monte Carlo method to obtain an error analysis result.

[0013] In a second aspect, the present application provides a device for calculating the porosity of a tight gas formation, the device comprising an acquisition module and a processing module. The processing module is used to: obtain a first parameter of the tight gas formation based on a plurality of nuclear logging methods, the first parameter comprising a formation capture cross section, formation density, apparent hydrogen index, formation element content, and formation thermal neutron cross section; and, select a parameter that satisfies a linear volume physics model from the first parameter to obtain a second parameter, the second parameter comprising at least one of the formation capture cross section, formation density, apparent hydrogen index, or formation thermal neutron cross section. The processing module is used to: construct a porosity response equation based on the second parameter and a shale content parameter of the tight gas formation, the shale content parameter being determined based on the formation composition of the tight gas formation; and, solve the porosity response equation to obtain the porosity.

[0014] In conjunction with the second aspect, in certain implementations of the second aspect, the multiple nuclear logging methods include neutron lifetime logging, pulsed neutron density logging, pulsed thermal neutron porosity logging, geo-element logging, and thermal neutron cross-section logging. The formation capture cross section is obtained based on neutron lifetime logging; the formation density is obtained based on pulsed neutron density logging; the apparent hydrogen index is obtained based on pulsed thermal neutron porosity logging; the formation element content is obtained based on geo-element logging; and the formation thermal neutron cross section is obtained based on thermal neutron cross-section logging.

[0015] In conjunction with the second aspect, in certain implementations of the second aspect, the porosity response equation is expressed by the following formula:

[0016]

[0017] in, is the porosity, s g is the gas saturation, V ma 、V sh 、V w and V g are the volume of stratum skeleton, mud, water in porosity and gas in pores, Σ ma ,Σ sh ,Σ w and Σ g are the macroscopic capture cross sections of formation skeleton, mud, water in porosity and gas in pores, respectively; ρ ma , ρ sh , ρ w and ρ gare the volume densities of the formation skeleton, mud, water in porosity, and gas in pores; HI ma , HI sh , HI w and HI g are the hydrogen index of the formation skeleton, mud, water in porosity and gas in pores, TNXS ma 、TNXS sh 、TNXS w and TNXS g are the thermal neutron cross sections of the formation skeleton, mud, water in porosity, and gas in pores, respectively. a ,Σ,ρ b and TNXS are apparent hydrogen index, formation capture cross section, formation density and formation thermal neutron cross section, respectively.

[0018] In combination with the second aspect, in certain implementations of the second aspect, the acquisition module is further used to: solve the porosity response equation based on a weighted least squares method to obtain the porosity.

[0019] In combination with the second aspect, in certain implementations of the second aspect, the processing module is further used to: perform error analysis on the porosity based on a Monte Carlo method to obtain an error analysis result.

[0020] In a third aspect, the present application provides a device for calculating the porosity of a tight gas formation, comprising a processor and a memory. The processor is configured to read instructions stored in the memory to execute the method of any possible implementation of the first aspect.

[0021] Optionally, there are one or more processors and one or more memories.

[0022] Optionally, the memory may be integrated with the processor, or the memory may be provided separately from the processor.

[0023] In the specific implementation process, the memory can be a non-transitory memory, such as a read-only memory (ROM), which can be integrated with the processor on the same chip or can be set on different chips. The embodiments of the present application do not limit the type of memory and the setting method of the memory and the processor.

[0024] The calculation device for the porosity of tight gas formations in the third aspect mentioned above can be a chip. The processor can be implemented by hardware or by software. When implemented by hardware, the processor can be a logic circuit, an integrated circuit, etc.; when implemented by software, the processor can be a general-purpose processor, which is implemented by reading the software code stored in the memory. The memory can be integrated in the processor or can be located outside the processor and exist independently.

[0025] In a fourth aspect, the present application provides a computer-readable medium, which stores a computer program (also referred to as code, or instructions) which, when executed on a computer, enables the computer to execute a method in any possible implementation of any of the above aspects.

[0026] In a fifth aspect, the present application provides a computer program product, which includes: a computer program (also referred to as code, or instructions), which, when executed, enables a computer to execute a method in any possible implementation of the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic flow chart of a method for calculating the porosity of a tight gas formation provided in an embodiment of the present application;

[0028] Figure 2 is a schematic diagram of a porosity calculation result provided in an embodiment of the present application;

[0029] Figure 3 is a schematic block diagram of a device for calculating the porosity of a tight gas formation provided in an embodiment of the present application;

[0030] Figure 4 This is a schematic block diagram of another device for calculating the porosity of tight gas formations provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] The technical solution in this application will be described below with reference to the accompanying drawings.

[0032] Oil well logging is a method of measuring geophysical parameters using geophysical properties of rock formations, such as electrochemical, electrical, acoustic, and radioactive properties. During oil drilling, logging is performed after reaching the designed well depth to obtain various petroleum geological and engineering data, which serve as raw materials for well completion and oilfield development.

[0033] Oil and gas development refers to the economic activity of building production capacity and producing oil and gas from proven oil and gas fields. Currently, the reservoirs explored for oil and gas reserves are mostly tight gas formations, making oil and gas development more difficult.

[0034] Petroleum well logging methods include electrical logging, sonic logging, and nuclear logging. Electrical and sonic logging are significantly affected by pore structure, while nuclear logging is less so. Therefore, models constructed using multiple nuclear logging parameters are currently mostly used to calculate the porosity of tight gas formations. However, tight gas formations have low porosity, and many nuclear logging parameters are insensitive to porosity changes, resulting in low porosity accuracy. Consequently, porosity calculation methods based on models constructed using multiple nuclear logging parameters are not ideal for tight gas formations.

[0035] In view of this, an embodiment of the present application provides a method and device for calculating the porosity of tight gas formations, which can improve the accuracy of calculated porosity and help reduce the difficulty of oil and gas development in tight gas formations.

[0036] Before introducing the calculation method and calculation device for the porosity of tight gas formations provided in the embodiments of the present application, the following points are explained.

[0037] First, in the embodiments shown below, the first, second, and various numerical numbers are only used for the convenience of description and are not intended to limit the scope of the embodiments of the present application. For example, they are used to distinguish different parameters.

[0038] Second, in the embodiments shown below, "at least one" refers to one or more, and "more" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b and c can represent: a, or b, or c, or a and b, or a and c, or b and c, or a, b and c, where a, b, c can be single or multiple.

[0039] Figure 1 The present invention provides a schematic flow chart of a method 100 for calculating the porosity of a tight gas formation. The method can be executed by a computing device. Figure 1 As shown, the method 100 may include the following steps:

[0040] S101. Obtain first parameters of a tight gas formation based on a plurality of nuclear logging methods. The first parameters include a formation capture cross section, a formation density, an apparent hydrogen index, a formation element content, and a formation thermal neutron cross section.

[0041] The various nuclear logging methods may include neutron lifetime logging, pulsed neutron density logging, pulsed thermal neutron porosity logging, earth element logging, thermal neutron cross-section logging, etc. It should be understood that the embodiments of the present application are not limited to the listed nuclear logging methods.

[0042] The formation capture cross section can be obtained based on the neutron lifetime logging method; the formation density can be obtained based on the pulsed neutron density logging method; the apparent hydrogen index can be obtained based on the pulsed thermal neutron porosity logging method; the formation element content can be obtained based on the earth element logging method; and the formation thermal neutron cross section can be obtained based on the thermal neutron cross section logging method.

[0043] S102. Select parameters that satisfy the linear volume physics model from the first parameters to obtain second parameters, where the second parameters include at least one of a formation capture cross section, a formation density, an apparent hydrogen index, or a formation thermal neutron cross section.

[0044] It should be understood that the formation capture cross section, formation density, apparent hydrogen index, and formation thermal neutron cross section are all parameters that satisfy the linear volume physics model.

[0045] It should also be understood that the linear volume physical model can be understood as a well logging response, and parameters are selected according to the well logging response to obtain the above-mentioned second parameter.

[0046] S103. Construct a porosity response equation based on the second parameter and a shale content parameter of the tight gas formation. The shale content parameter of the tight gas formation is determined based on the formation components of the tight gas formation.

[0047] Under different formation conditions, the logging responses of each substance in the porosity response equation will also be different. For example, the rock skeleton is generally composed of multiple minerals, mud can be a mixture of different types of clay, the types of fluids have diverse characteristics, and the density of gases is also different. These will affect the parameters obtained based on the nuclear logging method. Therefore, in order to facilitate the construction of the porosity response equation, it is necessary to approximate fluids of the same type but different properties as one fluid. Therefore, the embodiments of the present application make corresponding adjustments to the parameters of the porosity response equation based on the formation composition of the tight gas formation.

[0048] Specifically, the shale content parameter of the tight gas formation is determined according to the formation components of the tight gas formation, and the porosity response equation is constructed according to the shale content parameter of the tight gas formation and the above-mentioned second parameter.

[0049] S104. Solve the porosity response equation to obtain the porosity.

[0050] For example, the porosity response equation can be solved based on the weighted least squares method to obtain the porosity, that is, the variance of the parameters of the porosity response equation is minimized based on the weighted least squares method to obtain the optimal solution and then obtain the porosity.

[0051] The method for calculating the porosity of tight gas formations provided in the embodiments of the present application selects parameters that satisfy the linear volume physics model from a variety of nuclear logging parameters, removes parameters that are insensitive to porosity, and determines mud content parameters based on the formation components of the tight gas formation. The parameters for constructing the porosity response equation are further optimized, which can improve the accuracy of the calculated porosity and help reduce the difficulty of oil and gas development in tight gas formations.

[0052] The neutron lifetime logging method can obtain the formation capture cross section by measuring the change of neutron counts over time. The formation capture cross section can satisfy the linear volume physics model.

[0053] The pulsed neutron density logging method can measure formation density by utilizing the attenuation of inelastic gamma rays produced by neutrons. This formation density can satisfy a linear volume physics model.

[0054] The pulsed thermal neutron porosity logging method can measure the apparent hydrogen index to determine the deceleration capacity of the formation. The apparent hydrogen index conforms to the linear volume physics model.

[0055] Specifically, the pulsed thermal neutron porosity logging method actually provides a measurement parameter called apparent limestone porosity. However, apparent limestone porosity is significantly affected by lithology. For example, in sandstone formations, apparent limestone porosity varies nonlinearly with porosity. If the response equation constructed using apparent limestone porosity is directly used to solve the problem, the resulting porosity will deviate from the formation porosity. This deviation is particularly pronounced in tight gas formations. Therefore, to improve the calculation accuracy of tight gas formation porosity, the present embodiment converts apparent limestone porosity into an apparent hydrogen index, whose response pattern is more consistent with the linear volume physics model.

[0056] The aforementioned geoelement logging methods can measure formation element content using captured gamma spectroscopy and inelastic gamma spectroscopy. Formation element content primarily refers to the mineral content within the rock framework. Formation element content is difficult to reflect the properties of formation pore fluids and is therefore generally not used in constructing porosity response equations. However, it can be used as auxiliary information for optimization solutions.

[0057] The thermal neutron cross-section logging method is a controlled source thermal neutron cross-section logging method launched by Schlumberger in 2018. This method can measure formation thermal neutron cross-sections and is unaffected by excavation effects, with responses conforming to a linear volume physics model.

[0058] The formation thermal neutron cross section can be indirectly obtained using measurement parameters. For example, the formation thermal neutron cross section can be measured by measuring the elastic scattering cross section of the formation at a neutron energy of 0.025 eV using the capture gamma ratio and the gamma count ratio during the pulse.

[0059] As an optional embodiment, when the fluid in the pore is a mixture of gas and water, the porosity response equation can be expressed by the following formula:

[0060]

[0061] in, is the porosity, s g is the gas saturation, V ma 、V sh 、V w and V g are the volume of stratum skeleton, mud, water in porosity and gas in pores, Σ ma ,Σ sh ,Σ w and Σ g are the macroscopic capture cross sections of formation skeleton, mud, water in porosity and gas in pores, respectively; ρ ma , ρ sh , ρ w and ρ g are the volume densities of the formation skeleton, mud, water in porosity, and gas in pores; HI ma , HI sh , HI w and HI g are the hydrogen index of the formation skeleton, mud, water in porosity and gas in pores, TNXS ma 、TNXS sh 、TNXS w and TNXS g are the thermal neutron cross sections of the formation skeleton, mud, water in porosity, and gas in pores, respectively. a ,Σ,ρ b and TNXS are apparent hydrogen index, formation capture cross section, formation density and formation thermal neutron cross section, respectively.

[0062] It should be understood that the apparent hydrogen index, formation capture cross section, formation density and formation thermal neutron cross section can be measured by measuring instruments.

[0063] It should also be understood that since the optimal logging interpretation requires an overdetermined set of equations to ensure the accuracy of porosity measurement, the number of the above-mentioned porosity response equations is greater than the number of unknowns.

[0064] As an optional embodiment, error analysis is performed on the porosity based on the Monte Carlo method to obtain error analysis results.

[0065] For example, a tight gas formation with complex skeleton and pore fluid properties may be selected, and an error analysis of the porosity may be performed based on the Monte Carlo method to obtain an error analysis result.

[0066] Figure 2 A schematic diagram showing the calculation results of porosity is shown in FIG. Figure 2 As shown, the first vertical row represents the depth, which increases gradually from top to bottom. It should be understood that only 170 meters (m) to 240 meters are shown in the figure. The second vertical row includes curves showing the measured values ​​of formation capture cross section, neutron porosity and formation density as a function of depth. The range of formation capture cross section is [0, 25] cubic feet (cu), the range of neutron porosity is [-5, 50]%, and the range of formation density is [1.5, 3] grams per cubic meter (g / cm 3 ). The third vertical row includes curves showing how the measured values ​​of the formation thermal neutron cross section and the apparent hydrogen index vary with depth, wherein the range of the formation thermal neutron cross section is [0,3]1 / cm (1 / cm), and the range of the apparent hydrogen index is [0,50]%. The fourth vertical row includes curves showing how the porosity calculated by the method shown in the embodiment of the present application (also referred to as the comprehensive multi-parameter method), the neutron porosity method, and the thermal neutron cross section method varies with depth, wherein the porosity range of each method is [0,50]pu, which can be understood as a percentage. The fifth vertical row shows how the content of formation components varies with depth, wherein the formation components may include skeleton, mud, gas, oil, and water.

[0067] according to Figure 2 The porosity calculated by the method shown in the embodiment of the present application, the neutron porosity method, and the thermal neutron cross-section method is shown. Error analysis is performed on the three types of porosity based on the Monte Carlo method to obtain the error size under different mud content conditions and the error size under different porosity conditions.

[0068] Table 1 shows the magnitude of the errors under different shale content conditions. As shown in Table 1, the shale content can be 0%, 20%, or 50%. When the shale content is 0%, the porosity errors calculated by the integrated multi-parameter method, the neutron porosity method, and the thermal neutron cross-section method are 1.06, 2.49, and 2.14, respectively. When the shale content is 20%, the porosity errors calculated by the integrated multi-parameter method, the neutron porosity method, and the thermal neutron cross-section method are 0.97, 4.35, and 2.88, respectively. When the shale content is 40%, the porosity errors calculated by the integrated multi-parameter method, the neutron porosity method, and the thermal neutron cross-section method are 1.40, 8.23, and 2.19, respectively.

[0069] Table 1

[0070]

[0071] Table 2 shows the error magnitudes under different porosity conditions. As shown in Table 2, the porosity can be 5 pu, 10 pu, or 15 pu. It should be understood that pu can represent a percentage. When the porosity is 5 pu, the errors of the porosity calculated by the integrated multi-parameter method, the neutron porosity method, and the thermal neutron cross-section method are 0.98, 0.95, and 1.40, respectively. When the porosity is 10 pu, the errors of the porosity calculated by the integrated multi-parameter method, the neutron porosity method, and the thermal neutron cross-section method are 1.56, 4.56, and 6.25, respectively. When the porosity is 15 pu, the errors of the porosity calculated by the integrated multi-parameter method, the neutron porosity method, and the thermal neutron cross-section method are 2.40, 2.41, and 2.08, respectively.

[0072] Table 2

[0073]

[0074] Tables 1 and 2 show that for tight gas formations where the pore fluid is a mixture of gas and water, the errors of the porosity calculated by the integrated multi-parameter method under different shale content conditions or different porosity conditions are smaller than those of the neutron porosity method and the thermal neutron cross-section method.

[0075] Combined with the above Figure 1 and Figure 2 , describes the method of the embodiment of the present application in detail, and will be combined with 3 and Figure 4 , describe in detail the device of the embodiment of the present application.

[0076] Figure 3 A device 300 for calculating the porosity of a tight gas formation provided in an embodiment of the present application is shown. The device 300 includes: an acquisition module 310 and a processing module 320. The acquisition module 310 is used to: obtain first parameters of the tight gas formation based on multiple nuclear logging methods, the first parameters including the formation capture cross section, formation density, apparent hydrogen index, formation element content, and formation thermal neutron cross section; and, select parameters that satisfy the linear volume physics model from the first parameters to obtain second parameters, the second parameters including at least one of the formation capture cross section, formation density, apparent hydrogen index, or formation thermal neutron cross section. The processing module 320 is used to: construct a porosity response equation based on the second parameter and the shale content parameter of the tight gas formation, the shale content parameter being determined based on the formation composition of the tight gas formation; and, solve the porosity response equation to obtain the porosity.

[0077] Optionally, the multiple nuclear logging methods include neutron lifetime logging, pulsed neutron density logging, pulsed thermal neutron porosity logging, geo-element logging, and thermal neutron cross-section logging. The formation capture cross section is obtained based on the neutron lifetime logging method; the formation density is obtained based on the pulsed neutron density logging method; the apparent hydrogen index is obtained based on the pulsed thermal neutron porosity logging method; the formation element content is obtained based on the geo-element logging method; and the formation thermal neutron cross section is obtained based on the thermal neutron cross-section logging method.

[0078] Alternatively, the porosity response equation is expressed as follows:

[0079]

[0080] in, is the porosity, s g is the gas saturation, V ma 、V sh 、V w and V g are the volume of stratum skeleton, mud, water in porosity and gas in pores, Σ ma ,Σ sh ,Σ w and Σ g are the macroscopic capture cross sections of the formation skeleton, mud, water in porosity, and gas in pores, respectively; ρ ma , ρ sh , ρ w and ρ g are the volume densities of the formation skeleton, mud, water in porosity, and gas in pores; HI ma , HI sh , HI w and HI g are the hydrogen index of the formation skeleton, mud, water in porosity and gas in pores, TNXS ma 、TNXS sh 、TNXS w and TNXS g are the thermal neutron cross sections of the formation skeleton, mud, water in porosity, and gas in pores, respectively. a ,Σ,ρ b and TNXS are apparent hydrogen index, formation capture cross section, formation density and formation thermal neutron cross section, respectively.

[0081] Optionally, the acquisition module 310 is further configured to solve the porosity response equation based on a weighted least squares method to obtain the porosity.

[0082] Optionally, the processing module 320 is further configured to perform error analysis on the porosity based on a Monte Carlo method to obtain an error analysis result.

[0083] It should be understood that the device here is embodied in the form of a functional module. The term "module" here may refer to an application specific integrated circuit (ASIC), an electronic circuit, a processor (such as a shared processor, a proprietary processor or a group processor, etc.) and a memory for executing one or more software or firmware programs, a merged logic circuit and / or other suitable components that support the described functions. In an optional example, those skilled in the art will understand that the device may be specifically the computing device in the above embodiment, or the functions of the computing device in the above embodiment may be integrated into the device, and the device may be used to execute the various processes and / or steps corresponding to the computing device in the above method embodiment. To avoid repetition, they will not be described here.

[0084] The apparatus described above has the functionality to implement the corresponding steps performed by the computing device in method 100 described above. These functions can be implemented via hardware or via hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the aforementioned functions. For example, the acquisition module can be a communication interface, such as a transceiver interface.

[0085] Figure 4 A device 400 for calculating the porosity of a tight gas formation, provided in an embodiment of the present application, is shown. The device 400 includes a processor 410, a communication interface 420, and a memory 440. The processor, communication interface, and memory communicate with each other via an internal connection path. The memory is used to store instructions, and the processor is used to execute the instructions stored in the memory, thereby transmitting data between the communication interface and the memory.

[0086] The above-mentioned device is used to execute each process and step in the above-mentioned method for calculating the porosity of a tight gas formation. Specifically, the processor 410 is used to: obtain first parameters of the tight gas formation based on multiple nuclear logging methods, the first parameters including the formation capture cross section, formation density, apparent hydrogen index, formation element content, and formation thermal neutron cross section; select parameters that satisfy a linear volume physics model from the first parameters to obtain second parameters, the second parameters including at least one of the formation capture cross section, formation density, apparent hydrogen index, or formation thermal neutron cross section; construct a porosity response equation based on the second parameters and a shale content parameter of the tight gas formation, the shale content parameter being determined based on the formation composition of the tight gas formation; and solve the porosity response equation to obtain the porosity.

[0087] It should be understood that the apparatus 400 can be used to execute the various steps and / or processes corresponding to the computing device in the above-mentioned method embodiment. Optionally, the memory 440 may include read-only memory and random access memory, and provide instructions and data to the processor. A portion of the memory may also include non-volatile random access memory. For example, the memory may also store device type information. The processor 410 can be used to execute instructions stored in the memory, and when the processor 410 executes the instructions stored in the memory, the processor 410 is used to execute the various steps and / or processes of the above-mentioned method embodiment corresponding to the computing device.

[0088] It should be understood that in the embodiments of the present application, the processor of the above-mentioned device may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc.

[0089] During implementation, each step of the above method can be completed by an integrated logic circuit of hardware in a processor or by instructions in the form of software. The steps of the method disclosed in conjunction with the embodiments of the present application can be directly embodied as being executed by a hardware processor, or can be executed by a combination of hardware and software units in the processor. The software unit can be located in a storage medium mature in the art, such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. The storage medium is located in a memory, and the processor executes the instructions in the memory, and in combination with its hardware, completes the steps of the above method. To avoid repetition, a detailed description is not given here.

[0090] The present application provides a computer-readable storage medium for storing a computer program for implementing the method for calculating the porosity of tight gas formations shown in various possible implementations of the above embodiments.

[0091] The present application provides a computer program product, which includes a computer program (also referred to as code, or instructions). When the computer program runs on a computer, the computer can execute the method for calculating the porosity of tight gas formations shown in the various possible implementations in the above embodiments.

[0092] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0093] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0094] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0095] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0096] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0097] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0098] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for calculating the porosity of a tight gas formation, characterized in that: include: obtaining first parameters of the tight gas formation based on multiple nuclear logging methods, the first parameters including formation capture cross section, formation density, apparent hydrogen index, formation element content, and formation thermal neutron cross section; Selecting parameters that satisfy a linear volume physics model from the first parameters to obtain second parameters, where the second parameters include at least one parameter of the formation capture cross section, the formation density, the apparent hydrogen index, or the formation thermal neutron cross section; A porosity response equation is constructed based on the second parameter and a shale content parameter of the tight gas formation. The shale content parameter is determined based on the formation composition of the tight gas formation. The porosity response equation is expressed by the following formula: in, is the porosity, s g is the gas saturation, V ma 、V sh 、V w and V g are the volume of stratum skeleton, mud, water in porosity and gas in pores, Σ ma ,Σ sh ,Σ w and Σ g are the macroscopic capture cross sections of the formation skeleton, the mud, the water in the porosity, and the gas in the pores, respectively; ρ ma , ρ sh , ρ w and ρ g are the volume densities of the stratum skeleton, the mud, the water in the porosity, and the gas in the pores, respectively; HI ma , HI sh , HI w and HI g are the hydrogen indexes of the stratum skeleton, the mud, the water in the porosity, and the gas in the pores, TNXS ma 、TNXS sh 、TNXS w and TNXS g are the thermal neutron cross sections of the formation skeleton, the mud, the water in the porosity, and the gas in the pores, HI a ,Σ,ρ b and TNXS are respectively the apparent hydrogen index, the formation capture cross section, the formation density and the formation thermal neutron cross section; The porosity response equation is solved to obtain the porosity.

2. The method according to claim 1, characterized in that The multiple nuclear logging methods include neutron lifetime logging method, pulsed neutron density logging method, pulsed thermal neutron porosity logging method, earth element logging method and thermal neutron cross section logging method; The formation capture cross section is obtained based on the neutron lifetime logging method; The formation density is obtained based on the pulse neutron density logging method; The apparent hydrogen index is obtained based on the pulse thermal neutron porosity logging method; The formation element content is obtained based on the earth element logging method; The formation thermal neutron cross section is obtained based on the thermal neutron cross section logging method.

3. The method according to claim 1, characterized in that The porosity response equation is solved to obtain the porosity, including: The porosity response equation is solved based on the weighted least square method to obtain the porosity.

4. The method according to any one of claims 1 to 3, characterized in that The method further comprises: An error analysis is performed on the porosity based on the Monte Carlo method to obtain an error analysis result.

5. A device for calculating the porosity of a tight gas formation, characterized in that: include: an acquisition module configured to obtain first parameters of a tight gas formation based on a plurality of nuclear logging methods, the first parameters including a formation capture cross section, a formation density, an apparent hydrogen index, a formation element content, and a formation thermal neutron cross section; and to select parameters satisfying a linear volume physics model from the first parameters to obtain second parameters, the second parameters including at least one of the formation capture cross section, the formation density, the apparent hydrogen index, or the formation thermal neutron cross section; a processing module configured to construct a porosity response equation based on the second parameter and a shale content parameter of the tight gas formation, wherein the shale content parameter is determined based on formation components of the tight gas formation; and solve the porosity response equation to obtain porosity, wherein the porosity response equation is represented by the following formula: in, is the porosity, s g is the gas saturation, V ma 、V sh 、V w and V g are the volume of stratum skeleton, mud, water in porosity and gas in pores, Σ ma ,Σ sh ,Σ w and Σ g are the macroscopic capture cross sections of the formation skeleton, the mud, the water in the porosity, and the gas in the pores, respectively; ρ ma , ρ sh , ρ w and ρ g are the volume densities of the stratum skeleton, the argillaceous material, the water in the porosity, and the gas in the pores, respectively; HI ma , HI sh , HI w and HI g are the hydrogen indexes of the stratum skeleton, the mud, the water in the porosity, and the gas in the pores, TNXS ma 、TNXS sh 、TNXS w and TNXS g are the thermal neutron cross sections of the formation skeleton, the mud, the water in the porosity, and the gas in the pores, HI a ,Σ,ρ b and TNXS are the apparent hydrogen index, the formation capture cross section, the formation density and the formation thermal neutron cross section, respectively.

6. The device according to claim 5, characterized in that The processing module is further configured to: An error analysis is performed on the porosity based on the Monte Carlo method to obtain an error analysis result.

7. A device for calculating the porosity of a tight gas formation, characterized in that: include: A processor is coupled to a memory, wherein the memory is used to store a computer program, and when the processor calls the computer program, the device is caused to execute the method according to any one of claims 1 to 4.

8. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is run on a computer, the computer is caused to execute the method according to any one of claims 1 to 4.

Images