A method, device, system and medium for calculating shale oil saturation

Abstract

The present invention provides a method, device, system, and medium for calculating shale oil saturation. The method uses interval porosity from nuclear magnetic resonance (NMR) logging data as a basis to determine the correlation between porosity after determining the interval porosity cutoff value and S1. The quality of the correlation indicates the amount of oil-bearing reservoir space. This method can serve as an indicator of shale oil content. This method addresses the unsuitability of conventional reservoir oil content evaluation methods for shale reservoirs, such as closed coring for saturation determination, logging saturation interpretation models based on rock physics experiments, and calculation of original oil saturation using capillary pressure curves. Accurately calculating the oil and gas saturation of shale reservoirs aids well logging evaluation of reservoirs and oilfield exploration and development. This method offers unparalleled advantages over other saturation models for calculating shale reservoir oil content, demonstrates significant practical application results, and is highly valuable for promotion.

Description

Technical Field

[0001] The present invention belongs to the technical field of a method for evaluating oil and gas saturation by well logging calculation related to oil and natural gas exploration and development, and specifically relates to a method, equipment, system and medium for calculating the oil saturation of shale oil. Background Art

[0002] Shale oil has become a key area of oil and gas replacement in the exploration and development of the Daqing Oilfield. This type of reservoir has a high clay content and low effective porosity. Conventional reservoir oil assessment methods, such as sealed coring to determine saturation, logging saturation interpretation models based on rock physics experiments, and calculation of initial oil saturation using capillary pressure curves, are not applicable to shale oil. Shale oil is stored as free hydrocarbons in inorganic and organic pores within large sections of organic-rich shale, as well as adsorbed hydrocarbons on organic matter and rock particle surfaces. Nuclear magnetic resonance logging measures the resonant relaxation properties of hydrogen nuclei in the formation.

[0003] Therefore, it can reflect the physical properties of the reservoir and the properties of the fluids therein. NMR logging can detect liquid hydrocarbons stored in inorganic and organic pores in shale, but it is still uncertain how much of the detected hydrocarbons are free hydrocarbons.

[0004] In the existing technology, there is no physical model to determine the oil saturation of shale oil based on pyrolysis S1 and interval porosity based on nuclear magnetic resonance logging data. This also makes it impossible to detect the shale oil content and to accurately control the shale oil content, resulting in a relatively passive on-site mining process. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present invention provides a method, equipment, system and medium for calculating the oil saturation of shale oil, which can determine the oil saturation of shale oil based on a saturation physical model.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for calculating shale oil saturation, characterized by comprising the following steps:

[0008] A1: Based on the corresponding relationship between the NMR logging signal intensity and the hydrogen nucleus content in the pore fluid, the total formation porosity is determined, and then the porosity in different relaxation time intervals of the NMR logging is extracted;

[0009] A2: Based on the porosity of different relaxation time intervals extracted from NMR logging, correlation analysis is performed with the pyrolysis hydrocarbon content S1 in the rock, and the relaxation time at which the correlation becomes better is obtained;

[0010] A3: Based on the relaxation time at which the correlation improves, the shale oil saturation calculation formula is obtained and the shale oil saturation calculation is completed.

[0011] Furthermore, in step A1, the interval porosity of the nuclear magnetic resonance logging data is extracted, the porosity is observed and decomposed into porosity in different relaxation time intervals, and multiple BIN porosity distributions are obtained for P-type nuclear magnetic resonance, and the corresponding P-type relaxation time and CMR nuclear magnetic relaxation time are obtained respectively.

[0012] Furthermore, the data interval porosity calculation step in step A1 is as follows:

[0013]

[0014] in, and E (0) are porosity, P i is the pore distribution at relaxation time i.

[0015] Furthermore, the porosity distributions of 13 BINs obtained in step A1 include P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11, P12 and P13.

[0016] The corresponding P-type relaxation times are 0.5ms, 1ms, 2ms, 4ms, 8ms, 16ms, 32ms, 64ms, 128ms, 256ms, 512ms, 1024ms, and 2048ms respectively;

[0017] The corresponding CMR relaxation times are 0.5ms, 1ms, 2ms, 4ms, 8ms, 16ms, 32ms, and greater than 64ms respectively.

[0018] Furthermore, the step of comparing the correlation in step A2 is:

[0019] By comparing the correlations between the total porosity of nuclear magnetic resonance logging, the porosity in the interval greater than 4ms, the porosity in the interval greater than 8ms, the porosity in the interval greater than 16ms, the porosity in the interval greater than 32ms, and the porosity in the interval greater than 64ms and S1, it was found that the porosity with T2 greater than 8ms has a better correlation with S1 than the porosity with T2 greater than 4ms, and the pore space with T2 relaxation time greater than 8ms has a good correlation with S1.

[0020] Furthermore, the shale oil saturation calculation step in step S3 is as follows:

[0021] According to the calculation formula of effective pore volume in shale and the calculation formula of oil and gas volume in shale, the oil and gas saturation in shale is obtained as:

[0022]

[0023] Where, φ ＞8ms is the porosity of the interval after NMR logging is greater than 8ms, φ e is the effective porosity of the reservoir.

[0024] Furthermore, the effective pore volume in the shale is:

[0025] V e =φ e *V;

[0026] The volume of oil and gas in shale is:

[0027] V ＞8ms =φ ＞8ms *V;

[0028] Where, φ ＞8ms is the porosity of the interval after NMR logging is greater than 8ms, φ e is the effective porosity of the reservoir.

[0029] A system for calculating shale oil saturation, characterized in that according to a method for calculating shale oil saturation, the system comprises the following steps:

[0030] Extract interval porosity units from NMR logging data to observe the corresponding relationship between signal intensity and hydrogen nucleus content in pore fluid, and extract interval porosity from NMR logging data;

[0031] The correlation module comparing the interval porosity of NMR logging data and S1 is used to compare the extracted interval porosity of NMR logging data with S1 to obtain its correlation and obtain the relaxation time with good correlation;

[0032] The shale oil saturation calculation module is used to obtain the shale oil saturation calculation formula based on the relaxation time with good correlation and complete the shale oil saturation calculation.

[0033] A computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for calculating the oil saturation of shale oil when executing the computer program.

[0034] A computer-readable storage medium stores a computer program, wherein the computer program, when executed by a processor, implements the steps of the above-mentioned method for calculating the oil saturation of shale oil.

[0035] Compared with the prior art, the present invention has the following beneficial technical effects:

[0036] The present invention provides a method, device, system, and medium for calculating shale oil saturation. The method uses interval porosity from nuclear magnetic resonance (NMR) logging data as a basis to determine the correlation between porosity after determining the interval porosity cutoff value and S1. The quality of the correlation indicates the amount of oil-bearing reservoir space. This method can serve as an indicator of shale oil content. It can address the problem that conventional reservoir oil content evaluation methods, such as closed coring to determine saturation, logging saturation interpretation models based on rock physics experiments, and calculation of original oil saturation using capillary pressure curves, are not applicable to shale oil reservoirs. Accurately calculating the oil and gas saturation of shale reservoirs aids well logging evaluation of reservoirs and oilfield exploration and development. This method offers unparalleled advantages over other saturation models for calculating shale reservoir oil saturation, demonstrates significant practical application results, and is highly valuable for promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart of a method for calculating shale oil saturation in a specific embodiment of the present invention;

[0038] Figure 2 This is a comparison chart of the correlation between porosity in various intervals and S1 in a specific embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the actual well data processing effect in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0041] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0042] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0043] The present invention provides a method for calculating the oil saturation of shale oil, such as Figure 1 As shown, the following steps are included:

[0044] A1: Based on the corresponding relationship between the NMR logging signal intensity and the hydrogen nucleus content in the pore fluid, the total formation porosity is determined, and then the porosity in different relaxation time intervals of the NMR logging is extracted;

[0045] A2: Based on the porosity of different relaxation time intervals extracted from NMR logging, correlation analysis is performed with the pyrolysis hydrocarbon content S1 in the rock, and the relaxation time at which the correlation becomes better is obtained;

[0046] A3: Based on the relaxation time at which the correlation improves, the shale oil saturation calculation formula is obtained and the shale oil saturation calculation is completed.

[0047] Specifically, the porosity of the intervals in the NMR logging data and the porosity after each cutoff value are first extracted. The correlation between free hydrocarbon S1 and the porosity after each cutoff value is compared to identify the porosity interval with the best correlation. Based on the interval porosity in the NMR logging data, the correlation between the porosity after the interval porosity cutoff value and S1 is determined. The quality of the correlation represents the amount of oil-bearing reservoir space. Based on the saturation physical model, a mathematical formula for shale oil and gas saturation is established; this can serve as an indicator of the oil content of the shale.

[0048] A preferred embodiment provided by the present invention is that in step A1, the porosity data of the nuclear magnetic resonance logging interval is extracted, the total porosity is observed and decomposed into the porosity of different relaxation time intervals, and multiple BIN porosity distributions are obtained for P-type and CMR nuclear magnetic logging, and the corresponding P-type relaxation time and CMR nuclear magnetic relaxation time are obtained respectively.

[0049] Furthermore, the basis for determining formation porosity using nuclear magnetic resonance logging is the corresponding relationship between the observed signal intensity and the hydrogen nucleus content in the pore fluid; its value at time zero is proportional to the total hydrogen content in the formation pores. Therefore, after appropriate calibration, the signal intensity at time zero can be calibrated as the total porosity of the rock formation. The steps for calculating the data interval porosity in step A1 are as follows:

[0050]

[0051] in, and E (0) are porosity, P i is the pore distribution at relaxation time i.

[0052] Specifically, the porosity distributions of 13 BINs obtained in step A1 include P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11, P12 and P13.

[0053] The corresponding P-type relaxation times are 0.5ms, 1ms, 2ms, 4ms, 8ms, 16ms, 32ms, 64ms, 128ms, 256ms, 512ms, 1024ms, and 2048ms respectively;

[0054] The corresponding CMR relaxation times are 0.5ms, 1ms, 2ms, 4ms, 8ms, 16ms, 32ms, and greater than 64ms respectively.

[0055] Another preferred embodiment provided by the present invention is as follows: Figure 2 As shown, the steps of comparing the correlation in step A2 are:

[0056] By comparing the correlations between the total porosity of nuclear magnetic resonance logging, the porosity in the interval greater than 4ms, the porosity in the interval greater than 8ms, the porosity in the interval greater than 16ms, the porosity in the interval greater than 32ms, and the porosity in the interval greater than 64ms and S1, it was found that the correlation between the porosity with T2 greater than 8ms and S1 is much better than the porosity with T2 greater than 4ms, indicating that the pore space with T2 relaxation time greater than 8ms has a good correlation with S1.

[0057] Specifically, the oil-bearing volume of shale is primarily composed of free hydrocarbons in pores, organic matter, and hydrocarbons adsorbed on clay surfaces. Free hydrocarbons are related to S0 and S1 in pyrolysis data, while adsorbed hydrocarbons are related to S2. Because NMR logging detects fluids and hydrogen nuclei within the formation, the calibrated pore intervals are inevitably correlated with S1. Pore intervals with a good correlation with S1 are likely to have high oil content.

[0058] By comparison, the T2 relaxation time is positively correlated with the pore radius. By comparing the correlation between the total porosity of nuclear magnetic resonance logging, the porosity in the interval greater than 4ms, the porosity in the interval greater than 8ms, the porosity in the interval greater than 16ms, the porosity in the interval greater than 32ms, and the porosity in the interval greater than 64ms and S1, it is found that the correlation between the porosity with T2 greater than 8ms and S1 is much better than the porosity with T2 greater than 4ms, indicating that the pore space with T2 relaxation time greater than 8ms has the best correlation with S1.

[0059] Another preferred embodiment provided by the present invention is that the step of calculating the shale oil saturation in step A3 is:

[0060] The effective pore volume in shale is:

[0061] V e =φ e *V;

[0062] The volume of oil and gas in shale is:

[0063] V ＞8ms =φ ＞8ms *V;

[0064] The oil and gas saturation in shale is obtained as:

[0065]

[0066] Where, φ ＞8ms is the porosity of the interval after NMR logging is greater than 8ms, φ e is the effective porosity of the reservoir.

[0067] Specifically, based on the shale rock volume physical model, it is believed that the shale oil volume is mainly composed of free hydrocarbons in the pores, organic matter, and hydrocarbons adsorbed on the clay surface. Free hydrocarbons are related to S0 and S1 in the pyrolysis data, and adsorbed hydrocarbons are related to S2. Nuclear magnetic resonance logging detects fluids in the formation. The porosity in the interval after nuclear magnetic resonance logging is greater than 8ms has the best correlation with S1, which can directly indicate the oil content of shale oil. The shale oil saturation calculation equation can be established directly based on the saturation formula.

[0068] Another preferred embodiment provided by the present invention is a method for verifying the calculation of shale oil saturation, wherein the shale oil saturation is calculated using the following formula:

[0069]

[0070] In order to verify the applicability of the shale oil and gas saturation model, the shale reservoir well data in the study area were processed. Figure 3To process the result map, tracks 1 and 2 are geological stratification tracks, track 3 is a lithologic logging track, including natural gamma, natural potential, and wellbore curves, track 4 is a depth track, track 6 is deep, medium, and shallow resistivity, track 7 is a three-porosity logging track, including compensated density, compensated neutron, and acoustic time difference curves, track 8 is an interval porosity track from nuclear magnetic resonance logging, and track 9 is a comparison between core analysis S1 and the porosity in the interval greater than 8ms from nuclear magnetic resonance logging. The two also have good consistency. Track 9 is a comparison between the oil saturation calculated based on the porosity in the interval greater than 8ms from nuclear magnetic resonance logging and the one-dimensional nuclear magnetic saturation from field core analysis. The comparison results are generally in good agreement. In the lower 2360-2376 m interval, the calculated results of the highly mature layered shale section are higher than the experimental results, which may be due to the volatilization of the S0 and S1 components, resulting in lower experimental values. The results analysis proves the correctness of the method proposed in this paper and its adaptability to shale reservoirs.

[0071] In another embodiment of the present invention, a computer device is provided, comprising a processor and a memory, wherein the memory is configured to store a computer program, wherein the computer program includes program instructions, and the processor is configured to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may be another general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions, specifically for loading and executing one or more instructions in the computer storage medium to implement a corresponding method flow or corresponding function. The processor described in this embodiment of the present invention can be used in an operation of a method for calculating shale oil saturation.

[0072] In another embodiment of the present invention, a storage medium is provided, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in a computer device, used to store programs and data. It is understood that the computer-readable storage medium herein may include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides storage space, which stores the terminal's operating system. Furthermore, the storage space also stores one or more instructions suitable for being loaded and executed by a processor. These instructions may be one or more computer programs (including program code). It should be noted that the computer-readable storage medium herein may be high-speed RAM memory or non-volatile memory, such as at least one disk drive. The processor may load and execute the one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the method for calculating shale oil saturation described in the above-mentioned embodiment.

[0073] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0074] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0075] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0076] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating shale oil saturation, characterized in that: The following steps are involved: A1: Based on the corresponding relationship between the NMR logging signal intensity and the hydrogen nucleus content in the pore fluid, the total porosity of the formation is determined, and then the porosity in different relaxation time intervals of the NMR logging is extracted; Extract the total porosity of the formation from the NMR logging data, observe the porosity and decompose it into porosity in different relaxation time intervals. For P-type NMR, multiple BIN porosity distributions are obtained, and the corresponding P-type relaxation time and CMR relaxation time are obtained respectively. A2: Based on the porosity of different relaxation time intervals extracted from NMR logging, correlation analysis is performed with the pyrolysis hydrocarbon content S1 in the rock, and the relaxation time at which the correlation becomes better is obtained; A3: Based on the relaxation time with improved correlation, the shale oil saturation calculation formula is obtained and the shale oil saturation calculation is completed; The steps for calculating the shale oil saturation are as follows: According to the calculation formula of effective pore volume in shale and the calculation formula of oil and gas volume in shale, the oil and gas saturation in shale is obtained as: Where, φ ＞8ms is the porosity of the interval after NMR logging is greater than 8ms, φ e is the effective porosity of the reservoir.

2. A method for calculating shale oil saturation according to claim 1, characterized in that: The steps for calculating the total porosity of the formation in step A1 are: in, and E (0) are porosity, P i is the pore distribution at relaxation time i.

3. The method for calculating shale oil saturation according to claim 1, characterized in that: The porosity distributions of 13 BINs are obtained in step A1, including P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11, P12 and P13. The corresponding P-type relaxation times are 0.5ms, 1ms, 2ms, 4ms, 8ms, 16ms, 32ms, 64ms, 128ms, 256ms, 512ms, 1024ms, and 2048ms respectively; The corresponding CMR relaxation times are 0.5ms, 1ms, 2ms, 4ms, 8ms, 16ms, 32ms, and greater than 64ms respectively.

4. The method for calculating shale oil saturation according to claim 1, characterized in that: The steps of comparing the correlation in step A2 are: By comparing the correlations between the total porosity of nuclear magnetic resonance logging, the porosity in the interval greater than 4ms, the porosity in the interval greater than 8ms, the porosity in the interval greater than 16ms, the porosity in the interval greater than 32ms, and the porosity in the interval greater than 64ms and S1, it was found that the porosity with T2 greater than 8ms has a better correlation with S1 than the porosity with T2 greater than 4ms, and the pore space with T2 relaxation time greater than 8ms has a good correlation with S1.

5. The method for calculating shale oil saturation according to claim 1, characterized in that: The effective pore volume in the shale is: V e =φ e *V; The volume of oil and gas in shale is: V ＞8ms =φ ＞8ms *V; Where, φ ＞8ms is the porosity of the interval after NMR logging is greater than 8ms, φ e is the effective porosity of the reservoir.

6. A system for calculating shale oil saturation according to any one of claims 1 to 5, characterized in that: include: Extract interval porosity units from NMR logging data to observe the corresponding relationship between signal intensity and hydrogen nucleus content in pore fluid, and extract interval porosity from NMR logging data; The correlation module comparing the interval porosity of NMR logging data and S1 is used to compare the extracted interval porosity of NMR logging data with S1 to obtain its correlation and obtain the relaxation time with good correlation; The shale oil saturation calculation module is used to obtain the shale oil saturation calculation formula based on the well-correlated relaxation time and complete the shale oil saturation calculation; The steps for calculating the shale oil saturation are as follows: According to the calculation formula of effective pore volume in shale and the calculation formula of oil and gas volume in shale, the oil and gas saturation in shale is obtained as: Where, φ ＞8ms is the porosity of the interval after NMR logging is greater than 8ms, φ e is the effective porosity of the reservoir.

7. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method for calculating the oil saturation of shale oil as described in any one of claims 1 to 5 are implemented.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of a method for calculating shale oil saturation as described in any one of claims 1 to 5 are implemented.

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