A method of sampling a shale plug

Abstract

The present application relates to the technical field of petroleum and natural gas geophysical exploration, and discloses a shale plug sampling method.The shale plug sampling method comprises the following steps: S1, determining a core processing position in a well; S2, performing multidirectional sample processing to obtain a plurality of sample plugs; S3, judging whether the sedimentary characteristics of the plurality of sample plugs are consistent; if the sedimentary characteristics are inconsistent, returning to step S2; if the sedimentary characteristics are consistent, proceeding to the next step; S4, judging whether the physical characteristics of the plurality of sample plugs are consistent; if the physical characteristics are inconsistent, returning to step S2; if the physical characteristics are consistent, obtaining a target shale plug.The shale plug sampling method is suitable for remote and simple sampling environments, does not require laboratory precision measurement, and can obtain a plug sample with good consistency through simple operation, thereby ensuring that the multidirectional shale plug samples come from the same position in a core.

Description

Technical Field

[0001] This invention relates to the technical field of geophysical exploration of oil and gas, and particularly to a shale plunger sampling method. Background Technology

[0002] Shale reservoirs often exhibit characteristics such as heterogeneity, anisotropy, high clay content, brittleness, and associated sedimentary rhythms. When conducting fundamental seismic petrophysical studies of shale reservoirs, it is necessary to process well core samples into plunger samples that meet laboratory testing requirements. Furthermore, studying the anisotropy of shale requires processing multi-directional plunger samples.

[0003] When processing well core samples into multi-directional plunger samples, it is difficult to guarantee that the processed samples come from the "same" location, and it is also impossible to guarantee that the seismic rock physical parameters measured later belong to the "same" core. Summary of the Invention

[0004] This invention addresses the technical problem of ensuring sample consistency in the processing of multi-directional plunger samples using existing technologies, by providing a shale plunger sampling method. This shale plunger sampling method is suitable for remote and rudimentary sampling environments, requires no precision laboratory measurements, and yields highly consistent plunger samples through simple operations, ensuring that multi-directional shale plunger samples originate from the same location in the well core.

[0005] The purpose of this invention is to provide a sampling method for shale plungers, including...

[0006] S1. Determine the location for core processing in the well;

[0007] S2. Perform multi-directional sample processing to obtain multiple sample plungers;

[0008] S3. Determine whether the deposition characteristics of multiple sample plungers are consistent; if the deposition characteristics are inconsistent, return to step S2; if the deposition characteristics are consistent, proceed to the next step.

[0009] S4. Determine whether the physical properties of multiple sample plungers are consistent; if the physical properties are inconsistent, return to step S2; if the physical properties are consistent, the target shale plunger is obtained.

[0010] This invention separates the testing and screening of sedimentary characteristics and physical properties into two steps: first, sedimentary characteristics are screened, followed by physical properties. Relevant data and parameters of sedimentary characteristics can be obtained more quickly and intuitively. Physical properties are then screened only after the relevant conditions for sedimentary characteristics are met. This makes the entire process more efficient, enabling the acquisition of multi-directional shale plunger samples from the same location in the well core at the lowest possible production cost.

[0011] According to a preferred embodiment of the present invention, in step S1, the processing location is determined by lithology, bedding, grain size, and / or sorting characteristics. Lithology, bedding, grain size, and sorting are all technical terms specific to the art.

[0012] According to a preferred embodiment of the present invention, in step S2, the multi-direction includes a first direction and a second direction, corresponding to a first-direction sample plunger and a second-direction sample plunger; the multi-direction of the present invention refers to at least two directions.

[0013] Preferably, the first direction is perpendicular to the second direction or forms an angle of 10° to 80°. More preferably, the first direction is perpendicular to the second direction. For example, the direction parallel to the bedding planes (first direction) refers to the height of the plunger sample being at 0° to the shale bedding planes, and the direction perpendicular to the bedding planes (second direction) refers to the height of the plunger sample being at 90° to the shale bedding planes.

[0014] According to a preferred embodiment of the present invention, in step S3, the deposition feature includes at least one of color, layering structure, and roughness. Preferably, the deposition feature includes all three: color, layering structure, and roughness.

[0015] According to a preferred embodiment of the present invention, in step S4, the physical property includes density.

[0016] According to a preferred embodiment of the present invention, in step S3, when the deposition characteristics are inconsistent, the color inconsistency refers to the different areas occupied by the same color on the sample plunger surface (plunger surface and / or end face);

[0017] And / or, the inconsistency in bedding structure refers to different numbers of bedding layers and / or different bedding thicknesses;

[0018] And / or, the roughness inconsistency refers to different grain sizes of the bedding.

[0019] In contrast, consistent depositional characteristics mean that the area of ​​the same color in samples from multiple directions is basically the same, the number and thickness of bedding planes are basically the same, and the roughness, i.e. the grain size of the same bedding plane, is basically the same.

[0020] According to a preferred embodiment of the present invention, in step S3, the maximum value of the density difference among the plurality of sample plungers does not exceed 0.5 g / cm³. 3 That is, the physical properties are consistent.

[0021] According to a preferred embodiment of the present invention, in step S2, the sample processing is performed using a wire cutting instrument; preferably, the rotational speed ratio of the wire cutting instrument is 30-50.

[0022] According to a preferred embodiment of the present invention, in step S2, the plunger sample has a diameter of 20-30 mm and a length of 38-55 mm.

[0023] This invention utilizes selected processing instruments and parameters to process multi-directional shale plunger samples at determined processing locations. The processing instruments are chosen based on the characteristics of the shale reservoir. These characteristics generally include the following two aspects: Shale reservoirs typically have high clay content and are highly susceptible to water absorption and swelling; therefore, water-drilling instruments are usually not considered for processing, and non-water-drilling instruments are more commonly used. Shale reservoirs generally have microfractures, well-developed bedding, and are brittle; therefore, the vibration intensity generated by the instrument during operation must be low to ensure that the shale sample does not break during processing.

[0024] The processing rate is determined based on parameters such as sample hardness and brittleness. According to operator experience, samples with high hardness and brittleness are suitable for slower processing rates, while samples with low hardness and low brittleness are suitable for faster processing rates, ensuring sample integrity, smooth cut surfaces, and processing efficiency. The diameter of the plunger sample is determined based on the requirements of the subsequent testing instruments. The length of the plunger sample is determined based on the length requirements of the subsequent testing instruments and the diameter-to-length ratio requirements of the subsequent tests. The flatness and parallelism of the end faces of the obtained shale plunger samples should meet the requirements of subsequent testing items.

[0025] According to a preferred embodiment of the present invention, in step S3, in addition to consistent deposition characteristics, when the first direction is perpendicular to the second direction, the cylindrical surface of the sample plunger in the first direction is tangent to the end face of the sample plunger in the second direction. That is, the number of sample plunger overlap positions is maximized.

[0026] The beneficial effects of the present invention are as follows: the shale plunger sampling method of the present invention is suitable for remote and simple sampling environments, does not require laboratory precision measurement, and can obtain plunger samples with good consistency simply by controlling the consistency of multi-directional shale plunger samples according to sedimentary characteristics and physical property characteristics, thus ensuring that multi-directional shale plunger samples come from the same location in the well core.

[0027] The sampling method of this invention can effectively control the processing quality of multi-directional shale plunger samples by combining sedimentary characteristics and physical properties. It is also simple to operate and has a strong prospect for widespread application. Attached Figure Description

[0028] Figure 1 This is a flowchart of the shale plunger sampling method of the present invention;

[0029] Figure 2 This is a schematic diagram of the processing position determined on the well core in step S1 of the embodiment.

[0030] Figure 3 This is an example diagram illustrating quality control using deposition features in step S3 of the embodiment.

[0031] Figure 4 This is an example diagram illustrating the use of physical property characteristics for quality control in step S4 of the embodiment. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0033]

Example

[0034] Taking a shale production area in China as an example, the sampling method for multi-directional shale plungers is based on the following steps:

[0035] like Figure 1 As shown, step S1: Determine the processing location on the core sample in the well based on lithology, bedding, grain size, and / or sorting characteristics. In this embodiment, multiple directions are required to process the core sample in both the parallel and perpendicular bedding directions.

[0036] Step S2: Perform multi-directional sample processing. Using the selected processing instrument and parameters, perform multi-directional shale plunger sample processing according to the determined processing location. Based on the characteristics of the shale reservoir in this embodiment, such as high clay content, microfractures, well-developed bedding, and high brittleness, a wire cutting instrument is selected for plunger sample processing.

[0037] Through experiments, the rotational speed ratio of the wire EDM instrument in this embodiment is 40, the plunger sample diameter is 25mm, and the length is 38-55mm. According to these parameters, it takes 10 hours to process a plunger sample in one direction. Figure 2 This is an example diagram showing the processing location determined on a core sample from a certain well in this embodiment.

[0038] Step S3: Determine whether the sedimentary characteristics of the multi-directional shale plunger samples are consistent. If consistent, proceed to step S4. If inconsistent, return to step S2, or return to step S1.

[0039] The consistency of characteristics is determined by observing and comparing the sedimentary features of shale samples from multiple directions. The main criteria for judgment are whether the color, bedding development, and roughness of the shale plunger samples from multiple directions are consistent. Samples from multiple directions are considered consistent if the area of ​​the same color is basically the same, the number and thickness of bedding planes are basically the same, and the roughness, i.e., the grain size of the same bedding plane, is basically consistent.

[0040] Figure 3 This is an example diagram illustrating quality control using deposition features in an embodiment of the present invention. Figure 3 The deposition characteristics of the cylindrical surface of the sample perpendicular to the bedding direction are consistent with those of the end face of the sample parallel to the bedding direction.

[0041] Step S4: Determine if the physical properties of the multi-directional shale plunger samples are consistent. If inconsistent, return to step S2. If consistent, a multi-directional shale plunger sample from the same location is obtained. The physical property is density. For density, in this embodiment, the density difference of the multi-directional shale plunger samples is required to be no more than 0.5 g / cc (i.e., 0.5 g / cm³). 3 ).

[0042] Density is calculated by dividing weight by volume. Weight is determined using an electronic balance. Volume is calculated using diameter and length, which are read using vernier calipers.

[0043] Figure 4 This is an example diagram (cross-plot) illustrating the use of physical property characteristics for quality control in an embodiment of the present invention. Figure 4 Each point in the diagram represents a pair (two) samples. If the point is on the 45-degree line, it indicates that the density characteristics are consistent. The further away the point is from the line, the greater the difference.

[0044] Step 5: Obtain multi-directional shale plunger samples.

[0045] This invention provides a method for effectively controlling the processing quality of multi-directional shale plunger samples by integrating sedimentary and physical property characteristics. It is simple to operate and has strong potential for widespread application. This invention selects density as the primary control parameter for physical properties. For standard cylindrical plunger samples, density is the easiest physical property parameter to obtain compared to porosity. Density testing only requires an electronic balance and vernier calipers, making it low-cost and fast. However, porosity requires expensive specialized instruments for measurement and conversion based on density. Therefore, density is the simplest, fastest, and cheapest physical property control parameter.

[0046] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or a value such as a proportion, diameter, length, etc., is stated as 20-30, in this specification it means specifically listing values ​​such as 21-29, 22-28, ..., and 25. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0047] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method of sampling a shale plug, comprising: include S1. Determine the location for core processing in the well; S2. Perform multi-directional sample processing to obtain multiple sample plungers; S3. Determine whether the deposition characteristics of multiple sample plungers are consistent; If the depositional characteristics are inconsistent, return to step S2; If the sedimentary characteristics are consistent, proceed to the next step; S4. Determine whether the physical properties of multiple sample plungers are consistent; If the physical properties are inconsistent, return to step S2; If the physical properties are consistent, the target shale plunger is obtained.

2. The sampling method of claim 1, wherein, In step S1, the processing location is determined by lithology, bedding, grain size and / or sorting characteristics.

3. The sampling method according to claim 1 or 2, characterized in that, In step S2, the multiple directions include a first direction and a second direction; Preferably, the first direction is perpendicular to the second direction or forms an angle of 10° to 80°.

4. The sampling method according to claim 1 or 2, characterized in that, In step S3, the deposition features include at least one of color, layering structure, and roughness.

5. The sampling method of claim 1 or 2, wherein, In step S4, the physical property characteristics include density.

6. The sampling method of claim 4, wherein, In step S3, when the deposition characteristics are inconsistent, the inconsistency in color refers to the different areas occupied by the same color in the sample plunger; And / or, the inconsistency in bedding structure refers to different numbers of bedding layers, and / or different bedding thicknesses; And / or, the roughness inconsistency refers to different grain sizes of the bedding.

7. The sampling method of claim 5, wherein, In step S3, when the physical property characteristics are consistent, the maximum value of the density difference of the plurality of sample plungers does not exceed 0.5 g / cm 3 .

8. The sampling method of claim 1 or 2, wherein, In step S2, the sample processing is performed using a wire cutting instrument; preferably, the rotation speed ratio of the wire cutting instrument is 30-50.

9. The sampling method of claim 1 or 2, wherein, In step S2, the plunger sample has a diameter of 20-30 mm and a length of 38-55 mm.

10. The sampling method of claim 3, wherein, In step S3, in addition to the consistent deposition characteristics, when the first direction is perpendicular to the second direction, the cylindrical surface of the sample plunger in the first direction is tangent to the end face of the sample plunger in the second direction.

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