Method for evaluating oil-bearing property of shale oil and related equipment

Abstract

The present application provides a shale oil oiliness evaluation method and related equipment, which extracts nuclear magnetic interval porosity value through nuclear magnetic resonance logging result data, and then obtains interval porosity after cutoff value, simultaneously obtains formation pressure coefficient by using equivalent depth method, and calculates envelope size of nuclear magnetic T2 cutoff interval porosity and pressure coefficient in actual well, and the envelope size of nuclear magnetic interval porosity and pressure coefficient can directly evaluate shale oil oiliness. The present application can solve the problem that conventional reservoir oiliness evaluation method is not applicable to shale oil reservoir, such as sealed coring for determining saturation, logging saturation interpretation model based on rock physical experiment, and calculating original oil saturation by using capillary pressure curve. The present application directly evaluates shale oil oiliness through nuclear magnetic interval porosity and pressure coefficient envelope size, and has remarkable practical application effect, so it has great popularization value. There is no similar method in the present published literature and commercial application software.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration, specifically a method and related equipment for evaluating the oil-bearing properties of shale oil. Background Technology

[0002] In current oilfield exploration and development, shale oil and gas has gradually become an important area for oil and gas replacement. Free hydrocarbons (S1) are hydrocarbons that have been formed in the rock but still remain in the rock in a free state. Their size directly affects the reservoir's production and is an important indicator for directly evaluating oil production capacity.

[0003] Conventional methods for evaluating the oil content of sandstone mainly include closed-loop coring to determine saturation, well logging saturation interpretation models based on rock physics experiments, and calculation of oil saturation using capillary pressure curves. However, due to the difficulty in sampling shale, the difficulty in saturating oil and water, and the ease with which it can be broken by centrifugation, none of the above methods are suitable for evaluating the oil content of shale.

[0004] Most existing methods for testing oil content based on free hydrocarbons require testing shale samples. Currently, the main method for evaluating free hydrocarbons in shale oil is the organic geochemical analysis method based on rock pyrolysis. This method has advantages such as mature technology, high analytical accuracy, economy and speed, small sample volume, and convenient sample acquisition. However, it can only be used to analyze specific rock samples. For wells without rock samples, it is impossible to obtain free hydrocarbon S1. Therefore, this method is generally only used for systematic sampling and pyrolysis S1 measurement in key exploration wells. Summary of the Invention

[0005] This invention provides a method and related equipment for evaluating the oil-bearing properties of shale oil, in order to solve the problem that free hydrocarbons S1 cannot be obtained from wells without rock samples.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for evaluating the oil-bearing capacity of shale oil includes:

[0008] Extract porosity from nuclear magnetic resonance logging data intervals;

[0009] Based on the porosity values ​​of the interval in the nuclear magnetic resonance logging data, obtain the porosity of the interval after the cutoff value;

[0010] Obtain the formation pressure coefficient;

[0011] The envelope area of ​​porosity and formation pressure coefficient after calculating the cutoff value;

[0012] The oil-bearing capacity of shale oil is evaluated based on the size of the envelope.

[0013] Preferably, the porosity of the nuclear magnetic resonance logging data interval is extracted by means of the porosity of the nuclear magnetic resonance logging data interval being proportional to the total hydrogen content in the pores of the nuclear magnetic resonance logging data interval, and the porosity of the nuclear magnetic resonance logging data interval being extracted by means of the total hydrogen content.

[0014] Preferably, the cutoff value is the relaxation time that has the best correlation with pyrolysis S1.

[0015] Preferably, the relaxation times corresponding to the T2 spectra from nuclear magnetic resonance logging are arranged in ascending order.

[0016] Preferably, the formation pressure coefficient is obtained using the equivalent depth method.

[0017] Preferably, the envelope area of ​​the porosity and pressure coefficient after calculating the cutoff value is specifically as follows:

[0018] The envelope size of porosity and pressure coefficient after calculating the cutoff value is characterized using the same scale. The two curves are normalized separately, and then the envelope size is calculated.

[0019] Preferably, the evaluation of shale oil's oil content based on the envelope area specifically means that the larger the envelope, the better the shale oil's oil content and the higher its production capacity.

[0020] A shale oil oil content evaluation system, comprising:

[0021] Extraction module: Extracts porosity within a range of nuclear magnetic resonance logging data;

[0022] Interval porosity acquisition module: Based on the interval porosity of nuclear magnetic resonance logging data, acquire the interval porosity after the cutoff value;

[0023] Formation pressure acquisition module: Acquires formation pressure coefficient;

[0024] Calculation module: Calculates the envelope size of porosity and pressure coefficient within the interval after the cutoff value;

[0025] Evaluation module: Evaluates the oil-bearing capacity of shale oil based on the size of the envelope.

[0026] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method for evaluating the oil content of shale oil.

[0027] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method for evaluating the oil content of shale oil.

[0028] Compared with existing technologies, the present invention has the following beneficial effects: The present invention provides a method for evaluating the oil-bearing properties of shale oil. By extracting the porosity of the nuclear magnetic resonance logging data interval, the porosity of the interval after the cutoff value is obtained. At the same time, the formation pressure coefficient is obtained by using the equivalent depth method. The envelope size of porosity and pressure coefficient after the nuclear magnetic resonance T2 cutoff value is calculated in actual wells. The envelope size of porosity and pressure coefficient in the nuclear magnetic resonance interval directly evaluates the oil and gas-bearing properties of shale oil. It has high accuracy and significant practical application effects, and therefore has great promotional value.

[0029] Furthermore, the porosity of the nuclear magnetic resonance logging data range can be extracted by measuring the total hydrogen content, which yields high accuracy. Attached Figure Description

[0030] Figure 1 Correlation analysis of porosity and S1 in nuclear magnetic resonance logging intervals;

[0031] Figure 2 Correlation analysis between pressure coefficient and S1;

[0032] Figure 3 The envelope effect of porosity and pressure coefficient for NMR T2 greater than 8ms;

[0033] Figure 4 A fluid identification chart for full-diameter two-dimensional NMR T1-T2 spectra;

[0034] Figure 5 To calculate the correlation between the envelope value and the oil yield during the trial run;

[0035] Figure 6 This is a flowchart of a shale oil oil content evaluation method according to the present invention;

[0036] Figure 7 This is a block diagram of a shale oil oil content evaluation system according to the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0039] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0040] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0041] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0042] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0043] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0044] This invention is based on nuclear magnetic resonance (NMR) logging interval porosity, analyzing the correlation between NMR interval porosity (porosity after the T2 cutoff) and S1, clarifying the relationship between the spatial distribution of shale oil and gas reservoirs and their oil-bearing capacity. Simultaneously, it analyzes the correlation between pressure coefficient and S1; after organic matter hydrocarbon generation, the formation becomes overpressured, and the greater the overpressure, the higher the oil-bearing capacity. Therefore, NMR interval porosity and pressure coefficient are key parameters indicating the oil-bearing capacity of shale oil reservoirs; the larger the envelope (anti-crossing) size, the better the oil-bearing capacity. By normalizing the interval porosity and pressure coefficient and calculating the envelope size of interval porosity and pressure coefficient, the oil-bearing capacity of shale reservoirs can be quantitatively characterized. Furthermore, no similar method has been proposed or applied in currently published literature or commercial application software. This invention enables the identification of shale oil sweet spots using logging data, providing a new method for horizontal well target selection and shale production capacity evaluation.

[0045] In nuclear magnetic resonance logging, the horizontal axis of the T2 spectrum represents T2 (ms), and the vertical axis represents the interval porosity, reflecting the contribution of different T2 components to the measured porosity. The entire T2 distribution area represents the total formation porosity, and the interval porosity represents the porosity after a certain T2 time (greater than 8ms means the porosity after 8ms).

[0046] Rock pyrolysis analysis is a method for quantitatively determining the content of thermally vaporizable and pyrolytic hydrocarbons in rock samples using the principle of programmed temperature rise. The main parameters detected are S0, S1, and S2. S0 represents the mass fraction of gaseous hydrocarbons (C1-C7) at 90℃, existing as dissolved gas in liquid hydrocarbons within pure oil reservoirs. S1 represents the mass fraction of light and medium-quality liquid hydrocarbons (C8-C29) at 300℃. S2 represents the mass fraction of heavy crude oil, resins, and asphaltenes (greater than C29) at 300–600℃.

[0047] like Figure 6 As shown, the present invention provides a method for evaluating the oil content of shale oil, comprising:

[0048] S101 extracts porosity within the range of nuclear magnetic resonance logging data;

[0049] S102 obtains the porosity of the interval after the cutoff value based on the porosity of the nuclear magnetic logging data interval;

[0050] S103 obtains the formation pressure coefficient;

[0051] S104 calculates the envelope area of ​​porosity and pressure coefficient after the cutoff value;

[0052] S105 evaluates the oil-bearing properties of shale oil based on the envelope area.

[0053] The porosity extraction of nuclear magnetic resonance logging data intervals specifically involves the following: the porosity of the nuclear magnetic resonance logging data interval is proportional to the total hydrogen content in the pores of the nuclear magnetic resonance logging data interval. The porosity of the nuclear magnetic resonance logging data interval is extracted by the total hydrogen content. The contribution of different T2 components obtained by multi-exponential fitting of the raw data acquired by nuclear magnetic resonance logging to the measured porosity is also considered.

[0054] The cutoff value is the relaxation time when the correlation with free hydrocarbon S1 is best.

[0055] The relaxation times for shale reservoirs in nuclear magnetic resonance logging are 0.5ms, 1ms, 2ms, 4ms, 8ms, 16ms, 32ms, and 64ms.

[0056] The formation pressure coefficient is obtained using the equivalent depth method.

[0057] The specific envelope area of ​​the porosity and pressure coefficient after calculating the cutoff value is as follows:

[0058] The envelope areas of porosity and pressure coefficient after the cutoff value are calculated separately. The same scale is used to characterize the envelope size. The two curves are normalized separately, and then the envelope size is calculated.

[0059] The evaluation of shale oil's oil content based on the envelope area is as follows: the larger the envelope area, the better the shale oil's oil content.

[0060] This invention addresses the limitations of conventional methods for evaluating the oil-bearing potential of shale reservoirs, such as closed-loop coring for saturation determination, well logging saturation interpretation models based on rock physics experiments, and calculations of original oil saturation using capillary pressure curves. It directly evaluates the hydrocarbon potential of shale oil by measuring porosity and pressure coefficient envelopes within the NMR spectrum, demonstrating significant practical effectiveness and thus possessing considerable potential for widespread application. No similar methods have been proposed or applied in currently published literature or commercial software.

[0061] Example:

[0062] 1) Extract porosity from nuclear magnetic resonance logging data intervals:

[0063] Nuclear magnetic resonance (NMR) logging determines formation porosity based on the correlation between the observed signal intensity and the hydrogen nucleus content in the pore fluid. Its value at time zero is directly proportional to the total hydrogen content in the formation pores. Therefore, with proper calibration, the signal intensity at time zero can be calibrated as the total porosity of the rock formation.

[0064] That is, φ=E(0)=(i=1,2,3,...n) (Formula 1)

[0065] The observed porosity can be decomposed into porosity with different relaxation time intervals. The corresponding relaxation times for NMR are 0.5ms, 1ms, 2ms, 4ms, 8ms, 16ms, 32ms, and greater than 64ms.

[0066] 2) Correlation analysis between the porosity of the interval after the extracted cutoff value and free hydrocarbon S1

[0067] The oil-bearing volume of shale mainly consists of free hydrocarbons in the pores, organic matter, and adsorbed hydrocarbons on the clay surface. Free hydrocarbons are related to S0 and S1 in pyrolysis data, while adsorbed hydrocarbons are related to S2. Since nuclear magnetic resonance logging detects fluids in the formation and hydrogen nuclei in the formation, the pore regions determined by calibration will definitely have a correlation with S1. Pore regions with a good correlation with S1 indicate that these pore regions have good oil-bearing properties.

[0068] Analysis revealed that pore spaces with a T2 relaxation time greater than 8 ms showed the strongest correlation with S1. (See attached image) Figure 1As shown.

[0069] 3) Determine the correlation between the pressure coefficient and S1.

[0070] The formation pressure coefficient was determined using the equivalent depth method. The relationship between the pressure coefficient and core sample S1 was statistically analyzed for wells with different burial depths and maturity levels. The statistical analysis showed that the S1 value increases with increasing pressure coefficient (see...). Figure 2 ).

[0071] 4) Calculate the envelope area of ​​porosity and pressure coefficient greater than 8ms on NMR.

[0072] For different wells, the porosity and pressure coefficients of nuclear magnetic resonance logging greater than 8ms were characterized by the same scale to determine the envelope size. The two curves were normalized and the envelope size was calculated. The method was edited into a program and run for batch calculation in the study well area.

[0073] The T1-T2 spectra and cluster analysis results from two-dimensional nuclear magnetic resonance logging show that the shale in this area contains abundant movable oil signals and virtually no movable water. Therefore, the size of the envelope area can be used to evaluate the oil-bearing potential. Figure 4 ).

[0074] 5) Effect Verification

[0075] Data from shale reservoir wells in the study area were processed. Figure 3 To process the results, the first track is the lithology logging curve track, including natural gamma and caliper curves; the second track is the depth track; the third track is the deep and shallow resistivity track; the fourth track is the three-porosity logging curve track, including compensated density, compensated neutron, and sonic transit time curves; the fifth track is the porosity track for the nuclear magnetic resonance (NMR) logging interval; the sixth track is the envelope of porosity and pressure coefficient for the NMR logging interval greater than 8 ms; and the seventh track is the normalized envelope size. The envelope size can be used to determine if the sweet spot formation is the Q8, Q9, or Q1-Q3 oil-bearing layer group. Analysis of oil testing results at the same stratigraphic level shows that a larger envelope size indicates higher oil production capacity. Figure 5 The results analysis proved the correctness of the proposed method and its adaptability in shale reservoirs.

[0076] like Figure 7 The present invention provides a shale oil oil content evaluation system, comprising:

[0077] Extraction module: Extracts porosity from nuclear magnetic resonance logging data intervals;

[0078] Interval porosity acquisition module: Based on the porosity of the nuclear magnetic resonance logging data interval, acquire the interval porosity after the cutoff value;

[0079] Formation pressure acquisition module: Acquires formation pressure coefficient;

[0080] Calculation module: Calculates the envelope area of ​​porosity and pressure coefficient within the interval after the cutoff value;

[0081] Evaluation module: Evaluate the oil content of shale oil based on the envelope area.

[0082] An embodiment of the present invention provides a terminal device. This terminal device includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps in the various method embodiments described above. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the various device embodiments described above.

[0083] The computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention.

[0084] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0085] The processor may be a central processing unit (CPU), or 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.

[0086] The memory can be used to store the computer program and / or module. The processor implements various functions of the terminal device by running or executing the computer program and / or module stored in the memory and calling the data stored in the memory.

[0087] If the modules / units integrated into the terminal device are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0088] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art, guided by the specification, can make many other modifications without departing from the scope of the claims of the present invention, and all of these modifications are within the scope of protection of the present invention.

Claims

1. A method for evaluating oil content of shale oil, characterized by, The method comprises the following steps: extracting interval porosity of NMR logging data; obtaining interval porosity after a cutoff value according to the interval porosity of NMR logging data; obtaining formation pressure coefficient; calculating envelope area of interval porosity after the cutoff value and the formation pressure coefficient; evaluating oil-bearing property of shale oil according to the envelope size; the cutoff value is the relaxation time with the best correlation with pyrolysis S1; the envelope area of interval porosity after the cutoff value and the pressure coefficient is specifically calculated as follows: the envelope size of porosity after the cutoff value and the pressure coefficient is calculated, the same scale is used to represent the envelope size, and normalization is performed on the two curves respectively, and then the envelope size is calculated.

2. The method for evaluating oil content of shale oil according to claim 1, characterized in that, the interval porosity of NMR logging data is specifically extracted, the interval porosity of NMR logging data is proportional to the total hydrogen content in the interval porosity of NMR logging data, and the interval porosity of NMR logging data is extracted through the total hydrogen content.

3. The method for evaluating oil content of shale oil according to claim 1, characterized in that, the relaxation time corresponding to the NMR logging T2 spectrum is arranged in ascending order.

4. The method for evaluating oil content of shale oil according to claim 1, characterized in that, the formation pressure coefficient is obtained according to the equivalent depth method.

5. The method for evaluating oil content of shale oil according to claim 1, characterized in that, the evaluation of oil-bearing property of shale oil according to the envelope area is specifically that the larger the envelope is, the better the oil-bearing property of shale oil is, and the higher the productivity is.

6. A system for evaluating oil content of shale oil, characterized by, The method comprises the following steps: an extraction module: extracting interval porosity of NMR logging data; an interval porosity obtaining module: obtaining interval porosity after a cutoff value according to the interval porosity of NMR logging data; a formation pressure obtaining module: obtaining formation pressure coefficient; a calculation module: calculating envelope size of interval porosity after the cutoff value and the pressure coefficient; an evaluation module: evaluating oil-bearing property of shale oil according to the envelope size; the cutoff value is the relaxation time with the best correlation with pyrolysis S1; the envelope area of interval porosity after the cutoff value and the pressure coefficient is specifically calculated as follows: the envelope size of porosity after the cutoff value and the pressure coefficient is calculated, the same scale is used to represent the envelope size, and normalization is performed on the two curves respectively, and then the envelope size is calculated.

7. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, The processor executes the computer program to realize the steps of the shale oil oil-bearing property evaluation method according to any one of claims 1 to 5.

8. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 7. The computer program is executed by the processor to realize the steps of the shale oil oil-bearing property evaluation method according to any one of claims 1 to 5.

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