Elemental analysis-based shale brittleness evaluation method and device

Abstract

The invention relates to the technical field of element logging, in particular to a shale brittleness evaluation method and device based on element analysis, and the method comprises the following steps: researching the relationship between minerals and element contents, finding out sensitive elements of different minerals, establishing a conversion model of the elements and the minerals, solving a brittleness index, and classifying according to a shale gas reservoir brittleness classification standard. According to the relation between the mineral content and the element content, sensitive elements of different minerals are found out, and the element-mineral conversion model is established, so that the brittleness evaluation method is established, and powerful technical guarantee is provided for shale gas development evaluation.

Description

Technical Field

[0001] The invention relates to the technical field of element logging, and is a shale brittleness evaluation method and device based on element analysis. Background Art

[0002] Brittleness is one of the most important mechanical properties of rock and plays an important role in the development of shale gas. The particularity of shale gas reservoirs, the occurrence state of natural gas in shale, and the continuous accumulation of shale gas determine that its evaluation ideas and methods are quite different from those of conventional reservoirs, and the corresponding evaluation content is also different from that of conventional reservoirs.

[0003] In addition to the reservoir petrological and physical properties that are the same as those of conventional reservoirs, rock brittleness evaluation should also be considered. The brittleness index currently used to evaluate shale compressibility is mostly limited to the mechanical properties before or after the peak, and the calculated brittleness index does not conform to the objective law that brittleness decreases monotonically with increasing confining pressure.

[0004] Therefore, a shale brittleness evaluation method is needed to solve the above problems. Summary of the invention

[0005] The present invention provides a shale brittleness evaluation method and device based on element analysis, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problem that the brittleness index used to evaluate the compressibility of shale is mostly limited to the mechanical properties before or after the peak, and the calculated brittleness index does not conform to the objective law that the brittleness decreases monotonically with the increase of confining pressure.

[0006] One of the technical solutions of the present invention is achieved by the following measures: A shale brittleness evaluation method based on element analysis comprises the following steps:

[0007] Study the relationship between mineral and element content, find out the sensitive elements of different minerals, establish the conversion model between elements and minerals, obtain the brittleness index, and classify according to the brittleness classification standard of shale gas reservoirs.

[0008] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions:

[0009] The above-mentioned brittleness classification standards may include high brittleness, medium brittleness and low brittleness.

[0010] The above-mentioned brittleness index > 0.6 can be evaluated as high brittleness, the brittleness index between 0.4 and 0.6 can be evaluated as medium brittleness, and the brittleness index less than 0.4 can be evaluated as low brittleness.

[0011] The calculation formula of the above brittleness index can be:

[0012]

[0013] Wherein, W is the brittleness index, A is the quartz content, B is the feldspar content, C is the calcite content, D is the dolomite content, E is the pyrite content, and F is the clay content.

[0014] The second technical solution of the present invention is achieved through the following measures: a shale brittleness evaluation device based on elemental analysis, including a memory and a processor, the memory stores a program that can be run on the processor, and the processor implements the above-mentioned shale brittleness evaluation method based on elemental analysis when executing the program.

[0015] The present invention finds out the sensitive elements of different minerals through the relationship between mineral and element content, establishes an element-mineral conversion model, and thus establishes a brittleness evaluation method, providing a strong technical guarantee for shale gas development evaluation.

[0016]

[0017] Attached Figure 1 Schematic diagram of the regression of quartz-Si according to an embodiment of the present invention.

[0018] Attached Figure 2 Schematic diagram of regression of potassium feldspar-K according to an embodiment of the present invention.

[0019] Attached Figure 3 Schematic diagram of the regression of plagioclase-Ca according to an embodiment of the present invention.

[0020] Attached Figure 4 Schematic diagram of the regression of calcite-Ca according to an embodiment of the present invention.

[0021] Attached Figure 5 Schematic diagram of the regression of dolomite-Mg according to an embodiment of the present invention.

[0022] Attached Figure 6 Schematic diagram of the regression of pyrite-S according to an embodiment of the present invention.

[0023] Attached Figure 7 Schematic diagram of the regression of clay mineral-clay index according to an embodiment of the present invention.

[0024] Attached Figure 8 Schematic diagram of the regression of the relative content of carbonate minerals in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0026] In the present invention, for the convenience of description, the description of the relative position relationship of each component is described according to the layout of the drawings in the specification, such as: the position relationship of front, back, up, down, left, right, etc. is determined according to the layout direction of the drawings in the specification.

[0027] The present invention will be further described below in conjunction with embodiments and drawings:

[0028] Embodiment 1: As attached Figure 1 To Attachment Figure 8 As shown, the shale brittleness evaluation method based on elemental analysis includes the following steps: studying the relationship between minerals and element content, finding out the sensitive elements of different minerals, establishing a conversion model between elements and minerals, obtaining a brittleness index, and classifying according to the brittleness classification standard of shale gas reservoirs. In an embodiment of the present invention, the brittleness classification standard includes high brittleness, medium brittleness and low brittleness. Among them, a brittleness index of >0.6 is evaluated as high brittleness, a brittleness index of 0.4-0.6 is evaluated as medium brittleness, and a brittleness index of less than 0.4 is evaluated as low brittleness. In an embodiment of the present invention, "sensitive elements" refer to elements that contain a lot of minerals in rocks and have good characteristic performance.

[0029] As the content of quartz and carbonate minerals increases, the brittleness of the rock increases, and cracks are easily formed under the action of external forces. Therefore, quartz, calcite, and dolomite are often used as brittle minerals in shale gas reservoirs. However, in addition to felsic and carbonate minerals, the brittle minerals in the southwestern shale gas reservoir are also related to the content of pyrite. Therefore, in the embodiment of the present invention, the calculation formula of the reservoir brittleness index is:

[0030]

[0031] Wherein, W is the brittleness index, A is the quartz content, B is the feldspar content, C is the calcite content, D is the dolomite content, E is the pyrite content, and F is the clay content.

[0032] Attached Figure 1 To Attachment Figure 8 The following is a regression diagram of an embodiment of the present invention, i.e., a diagram of the relationship between minerals and sensitive elements. In the embodiment of the present invention, the conversion model between elements and minerals is established as follows: (1) Quartz-Si conversion model: Through the intersection of quartz and Si, it is found that quartz and Si elements have a linear relationship (see Figure 1 ), the regression equation is shown in Table 1. (2) Potassium feldspar-K conversion model: Through the intersection of potassium feldspar and K, it is found that potassium feldspar and K element have a linear relationship (see Figure 2 ), the regression equation is shown in Table 1. (3) Plagioclase-Ca conversion model: Through the intersection of plagioclase and Ca, it is found that plagioclase and Ca have a linear relationship (see Figure 3), the regression equation is shown in Table 1. (4) Calcite-Ca conversion model: Through the intersection of calcite and Ca, it is found that calcite and Ca elements have a linear relationship (see Figure 4 ), the regression equation is shown in Table 1. (5) Dolomite-Mg conversion model: Through the intersection of dolomite and Mg, it is found that dolomite and Mg have a linear relationship (see Figure 5 ), the regression equation is shown in Table 1. (6) Pyrite-S conversion model: Through the intersection of pyrite and S, it is found that pyrite and S elements have a linear relationship (see Figure 6 ), the regression equation is shown in Table 1. (7) Clay mineral-clay index conversion model: By intersecting clay minerals with clay index (100-SiO2-CaCO3-MgCO3-1.99Fe), it was found that clay minerals and clay index were linearly related (see Figure 7 ), the regression equation is shown in Table 1. (8) Carbonate mineral-(Ca+1.455Mg) conversion model: By intersecting carbonate minerals with Ca+1.455Mg, it is found that carbonate minerals have a linear relationship with Ca+1.455Mg elements (see Figure 8 ), the regression equation is shown in Table 1. In the embodiment of the present invention, "intersection" refers to intersection or correlation, which is represented by the correlation between a point and a line in the accompanying drawings.

[0033] Table 1 Element-mineral conversion model

[0034]

[0035] The embodiment of the present invention finds out the sensitive elements of different minerals through the relationship between mineral and element content, establishes an element-mineral conversion model, and thus establishes a brittleness evaluation method, which overcomes the shortcomings of existing calculation methods and provides a strong technical guarantee for shale gas development evaluation.

[0036] Example 2: An embodiment of the present invention provides a shale brittleness evaluation device based on elemental analysis, which includes a memory, a processor, a communication interface and a communication bus. A program that can be run on the processor is stored in the memory, and when the processor executes the program, the shale brittleness evaluation method based on elemental analysis described in the above embodiment is implemented.

[0037] The processor may be a central processing unit, or other general-purpose processors, digital signal processors, application-specific integrated circuits, field programmable gate arrays or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, or a combination of the above chips.

[0038] The memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs, non-transitory computer executable programs and units, such as the corresponding program units in the above method embodiments of the present invention. The processor executes various functional applications of the processor and works data processing by running the non-transitory software programs, instructions and modules stored in the memory, that is, realizing the shale brittleness evaluation method based on elemental analysis described in the above embodiment.

[0039] The memory may include a program storage area and a data storage area, wherein the program storage area may store an operating system and application programs required for at least one function; the data storage area may store data created by the processor, etc. In addition, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage devices. The memory may optionally include a memory remotely disposed relative to the processor, and these remote memories may be connected to the processor via a network. The one or more programs are stored in the memory, and when executed by the processor, the shale brittleness evaluation method based on elemental analysis described in the above embodiment is executed.

[0040] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A shale brittleness evaluation method based on elemental analysis, characterized in that The following steps are involved: Study the relationship between mineral and element content, find out the sensitive elements of different minerals, establish the conversion model between elements and minerals, obtain the brittleness index, and classify according to the brittleness classification standard of shale gas reservoirs.

2. The shale brittleness evaluation method based on elemental analysis according to claim 1 is characterized in that The brittleness classification standards include high brittleness, medium brittleness and low brittleness.

3. The shale brittleness evaluation method based on elemental analysis according to claim 2 is characterized in that A brittleness index of >0.6 is evaluated as high brittleness, a brittleness index between 0.4 and 0.6 is evaluated as medium brittleness, and a brittleness index of less than 0.4 is evaluated as low brittleness.

4. The shale brittleness evaluation method based on elemental analysis according to claim 1, 2 or 3, characterized in that The calculation formula of brittleness index is: Wherein, W is the brittleness index, A is the quartz content, B is the feldspar content, C is the calcite content, D is the dolomite content, E is the pyrite content, and F is the clay content.

5. A shale brittleness evaluation device based on elemental analysis, comprising a memory and a processor, wherein the memory stores a program that can be run on the processor, characterized in that: When the processor executes the program, the shale brittleness evaluation method based on elemental analysis as described in any one of claims 1 to 4 is implemented.

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