Dolomite reservoir space comprehensive quantitative characterization method

Abstract

The present application relates to a dolomite reservoir space full-size comprehensive quantitative characterization method, comprising the following steps: S1. Taking dolomite core or outcrop sample to make columnar sample, and cutting and grinding the two ends of the columnar sample; S2. Scanning the columnar sample by industrial CT to obtain dolomite pore three-dimensional data body, and using analysis software to distinguish rock matrix components and pores based on density difference through gray scale, and analyzing macropore and cave distribution with a diameter greater than 400 mu m; S3. Detecting the columnar sample by nuclear magnetic resonance to obtain a pore characterization range distribution diagram of dolomite sample with a diameter less than 1000 mu m; S4. Data fusion of macropore and cave distribution data with a diameter greater than 400 mu m in step S2 and pore characterization range distribution diagram with a diameter less than 1000 mu m in step S3 to obtain dolomite pore and cave content and distribution. The present application can comprehensively and quantitatively characterize the pore type content and distribution characteristics of deep dolomite reservoirs.

Description

Technical Field

[0001] This invention relates to the field of carbonate reservoir characterization, and in particular to a comprehensive quantitative characterization method for the full-scale storage space of dolomite reservoirs. Background Technology

[0002] As oil and gas exploration continues to advance into deeper and ultra-deep layers, the development of large-scale, high-quality reservoirs suitable for commercial exploitation in the deep subsurface (>6000m) has become a key risk factor. Current exploration practices indicate that dolomite is an important deep carbonate reservoir and a preferred target. Therefore, quantitative characterization of the spatial types, pore sizes, contents, and distribution of ultra-deep dolomite reservoirs has become a key focus and challenge in research.

[0003] Dolomite reservoirs exhibit a rich variety of spatial types, classified into primary and secondary porosity according to their genetic origin. Secondary porosity includes vugs, mold pores, and intragranular pores. The diameter of dolomite reservoir spaces varies considerably, ranging from meters to micrometers to nanometers. Holes larger than 2 mm are classified as cavities, while those smaller than 2 mm are classified as pores. Pores are further subdivided based on diameter into cryptopores (<10 μm), micropores (10 μm–100 μm), small pores (100 μm–250 μm), mesopores (250 μm–500 μm), macropores (500 μm–1000 μm), and giant pores (1000 μm–2000 μm).

[0004] Currently, there are few studies on the full-size characterization of dolomite reservoir space by scholars at home and abroad. They mainly use methods such as mercury intrusion porosimetry and nuclear magnetic resonance to quantitatively measure and evaluate the pore volume in the reservoir. The pores characterized are mainly concentrated in the micrometer range, with little characterization of pores at the nanometer and centimeter levels. They cannot fully characterize the size, content and distribution of reservoir space, and they do not consider the pore type and origin.

[0005] Therefore, those skilled in the art are dedicated to developing a comprehensive quantitative characterization method for the full-scale dolomite reservoir space, which can comprehensively and quantitatively characterize the content and distribution characteristics of pore types in deep dolomite reservoirs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a comprehensive quantitative characterization method for the full-size dolomite reservoir space, which can comprehensively and quantitatively characterize the content and distribution characteristics of pore types in deep dolomite reservoirs.

[0007] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A comprehensive quantitative characterization method for the full-size dolomite reservoir space, comprising the following steps:

[0008] S1. Take a dolomite core or outcrop sample and prepare it into a columnar sample, then cut and grind both ends of the columnar sample.

[0009] S2. By scanning columnar samples with industrial CT, three-dimensional data volume of dolomite pores was obtained. Based on density differences, analysis software was used to distinguish rock matrix components and pores by grayscale, and the distribution of macropores and karst caves with diameters greater than 400 μm was analyzed.

[0010] S3. By detecting columnar samples using nuclear magnetic resonance, a distribution map of the porosity range of dolomite samples with a diameter of less than 1000 μm was obtained.

[0011] S4. The distribution data of macropores and cavities with a diameter greater than 400 μm in step S2 are fused with the distribution map of pores with a diameter less than 1000 μm in step S3 to obtain the content and distribution of pores and cavities in dolomite.

[0012] The beneficial effects of this invention are: it integrates the advantages of nuclear magnetic resonance (NMR) in quantitatively characterizing the distribution of micropores and macropores in dolomite with the advantages of industrial CT scanning in quantitatively characterizing macropores, giant pores, and cavities, making full-scale quantitative characterization of dolomite reservoir space possible and overcoming the limitations of single testing techniques. The overlap between the two detection methods in the 400μm to 1000μm range can be used to check the quality of data fusion, and the method of this invention has self-verification capabilities through discrimination and comparison.

[0013] Based on the above technical solution, the present invention can be further improved as follows.

[0014] Furthermore, step S1 also includes characterizing the pore type and occurrence of the dolomite:

[0015] The cut sample was made into a cast thin section, and the cast thin section was scanned by a polarizing microscope to obtain the type and distribution map of macroscopic pores;

[0016] By scanning the thin sections of the casting with a scanning electron microscope, the types and distribution maps of micropores were obtained. The types and distribution maps of macropores were then fused with the types and distribution maps of micropores to obtain the pore types and occurrence of dolomite.

[0017] The beneficial effect of adopting the above-mentioned further scheme is that by observing the cast thin section under polarized light and scanning electron microscopy, the information on the origin of pores can be integrated into the pore size distribution characteristics, which is conducive to the study of the origin mechanism of pores.

[0018] Furthermore, in step S1, the diameter of the columnar sample is 25 mm and the length is 40 mm to 80 mm.

[0019] The advantage of adopting the above-mentioned further scheme is that the diameter of the columnar sample is 25 mm and the length is 40 mm to 80 mm, which is beneficial for subsequent industrial CT scanning and nuclear magnetic resonance detection.

[0020] Furthermore, in step S2, the rock matrix components include calcite and dolomite.

[0021] The advantage of adopting the above-mentioned further scheme is that it facilitates the analysis software to analyze the rock matrix components through grayscale analysis.

[0022] Furthermore, in step S4, the pore distribution data from industrial CT scanning and nuclear magnetic resonance are fused to obtain the pore volume corresponding to each pore size segment of the dolomite, and the total porosity of the dolomite sample is calculated.

[0023] Compare the total porosity with the total porosity measured by helium. If the error between the two is large, repeat steps S1 to S4 to finally obtain the content and distribution of pores and vugs in the dolomite.

[0024] The beneficial effect of adopting the above-mentioned further scheme is that the two test methods can be applied to check the quality of data fusion in the overlapping part of 400μm-1000μm and the determination of total porosity of helium. Through discrimination and comparison, the method of the present invention has self-verification. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the steps of a specific embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a sample structure according to a specific embodiment of the present invention;

[0027] Figure 3 This is a diagram showing the main reservoir space types of dolomite in Embodiment 1 of the present invention;

[0028] Figure 4 This is a schematic diagram of an industrial CT three-dimensional scan according to Embodiment 1 of the present invention;

[0029] Figure 5 This is a schematic diagram of nuclear magnetic resonance detection in Embodiment 1 of the present invention;

[0030] Figure 6 This is a schematic diagram of the full-size comprehensive quantitative characterization of the storage space in Embodiment 1 of the present invention. Detailed Implementation

[0031] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0032] In the description of this invention, it should be understood that the terms "center," "length," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "inner," "outer," "circumferential," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the system or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0034] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] like Figure 1 , Figure 2 As shown, a comprehensive quantitative characterization method for the full-size dolomite reservoir space includes the following steps:

[0036] S1. Take a dolomite core or outcrop sample and prepare it into a columnar sample. Then cut and grind both ends of the columnar sample. Specifically, after cutting and grinding both ends of the dolomite core or outcrop sample, the prepared columnar sample should have a diameter of 25 mm and a length of 40 mm to 80 mm, which is beneficial for subsequent industrial CT scanning and nuclear magnetic resonance detection.

[0037] This also includes characterizing the pore type and occurrence of dolomite. Specifically, thin sections of the sample, cut from both ends, are prepared to facilitate subsequent observation and statistical analysis of reservoir space type, occurrence, and content. The thin sections are then scanned using a polarizing microscope to obtain macroscopic pore types and distribution maps.

[0038] By scanning thin sections of the cast body using a scanning electron microscope, the types and distribution maps of micropores are obtained. The macropore types and distribution maps are then fused with the micropore types and distribution maps to determine the pore type and occurrence of the dolomite. This sampling method ensures, as far as possible, that the pore characteristics of the two-dimensional thin sections are similar to and comparable to those of the three-dimensional plunger samples. The cast thin sections can be used to determine the main types of reservoir porosity in dolomite.

[0039] S2. By scanning columnar samples with industrial CT, three-dimensional data volume of dolomite pores was obtained. Based on density differences, analysis software was used to distinguish rock matrix components and pores by grayscale, and the distribution of macropores and cavities with diameters greater than 400 μm was analyzed. Rock matrix components include calcite and dolomite.

[0040] S3. By detecting columnar samples with nuclear magnetic resonance, a distribution map of the pore size range of dolomite samples with a diameter of less than 1000 μm was obtained.

[0041] Specifically, industrial CT scanning can quantitatively characterize medium-to-large-scale pores and cavities with diameters greater than 400 μm in large samples. A plunger sample with both ends ground flat is placed into an industrial CT scanner for scanning to obtain three-dimensional data of dolomite pores. Based on density differences, Avizo software can be used to distinguish rock matrix components (calcite, dolomite, etc.) and pore-fracture zones using grayscale, and analyze the distribution characteristics of macropores and fractures larger than 400 μm.

[0042] S4. The distribution data of macropores and cavities with a diameter greater than 400 μm in step S2 are fused with the distribution map of pores with a diameter less than 1000 μm in step S3 to obtain the content and distribution of pores and cavities in dolomite.

[0043] Furthermore, due to limitations in analytical testing equipment and environment, the range of pore diameters that can be characterized within dolomite varies significantly among different testing methods. Industrial CT scans can only identify pores and cavities with diameters greater than 400 micrometers, lacking information on the distribution of pores with diameters less than 400 micrometers. In contrast, nuclear magnetic resonance (NMR) has better quantitative characterization capabilities for pores with diameters less than 1000 micrometers. There is overlap in the pore characterization range of the two methods from 400 micrometers to 1000 micrometers. Therefore, data fusion based on the pore volume content of the overlapping portion obtained from the two methods is necessary to achieve a full-scale characterization of the pore and cavity content and distribution in dolomite.

[0044] By fusing pore distribution data from industrial CT scans and nuclear magnetic resonance (NMR) measurements, the pore volume corresponding to each pore size segment of the dolomite is obtained, and the total porosity of the dolomite sample is calculated. The total porosity is compared with the total porosity measured by helium gas. If the error is large, steps S1 to S4 are repeated to finally obtain the pore and cavity content and distribution of the dolomite. If the error is small, the full-size pore-cavity distribution law of dolomite characterized by this invention using different experimental methods is considered reasonable.

[0045] Example 1

[0046] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6As shown, this invention uses dolomite from the Xiaoerbulake Formation in the Shutan 1 well of the Tarim Basin for testing, and includes the following steps:

[0047] S1. Take a dolomite core sample and make it into a columnar sample. Cut and grind both ends of the columnar sample. The diameter of the columnar sample is 25 mm and the length is 60 mm.

[0048] The cut samples were made into thin sections, and the macroscopic pore types and distribution maps were obtained by scanning the thin sections with a polarizing microscope. The microscopic pore types and distribution maps were obtained by scanning an electron microscope. The macroscopic and microscopic pore types and distribution maps were fused to obtain the pore types and occurrences of dolomite. By observing the thin sections with polarizing light and scanning electron microscope, the information on the pore formation type can be integrated into the pore size distribution characteristics, which is beneficial to the study of the pore formation mechanism.

[0049] S2. By scanning columnar samples with industrial CT, three-dimensional data volume of dolomite pores was obtained. Based on density differences, Avizo software can be used to distinguish rock matrix components (calcite, dolomite, etc.) and pores-fractures by grayscale, and analyze the distribution characteristics of macropores and fractures larger than 400 μm.

[0050] S3. By detecting columnar samples using nuclear magnetic resonance, a distribution map of the porosity range of dolomite samples with a diameter of less than 1000 μm was obtained.

[0051] S4. The distribution data of macropores and cavities with a diameter greater than 400 μm in step S2 are fused with the distribution map of pores with a diameter less than 1000 μm in step S3 to obtain the content and distribution of pores and cavities in dolomite.

[0052] By fusing the pore distribution data from industrial CT scans and nuclear magnetic resonance (NMR) data, the pore volume corresponding to each pore size segment of the dolomite was obtained, and the total porosity of the dolomite sample was calculated. Since the error between the two is small, the full-size pore-cavity distribution law of the dolomite characterized by combining different experimental methods in this embodiment is considered reasonable.

[0053] like Figure 6 As shown, the data distribution of macropores and karst caves in step S2 of this embodiment and the porosity characterization range distribution map in step S3 are fused to obtain the following information on the content and distribution of pores and caves in dolomite:

[0054] Pore ​​diameters less than 10 μm account for 5.7% of the total pore volume; pore diameters between 10 μm and 200 μm account for 4.5%; pore diameters between 20 μm and 40 μm account for 8.1%; pore diameters between 40 μm and 60 μm account for 5.1%; pore diameters between 60 μm and 100 μm account for 0%; pore diameters between 100 μm and 250 μm account for 25.6%; and pore diameters of 2... Pore ​​diameters of 50 μm to 500 μm account for 13.2% of the total pore volume; pore diameters of 500 μm to 800 μm account for 10.3% of the total pore volume; pore diameters of 800 μm to 1000 μm account for 8% of the total pore volume; pore diameters of 1000 μm to 2000 μm account for 13.4% of the total pore volume; pore diameters of 2000 μm to 3000 μm account for 4.1% of the total pore volume; and pore diameters greater than 3000 μm account for 2% of the total pore volume.

[0055] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A comprehensive quantitative characterization method for the full-size dolomite reservoir space, characterized in that, Includes the following steps: S1. Take a dolomite core or outcrop sample and prepare it into a columnar sample, then cut and grind both ends of the columnar sample. S2. By scanning columnar samples with industrial CT, three-dimensional data volume of dolomite pores was obtained. Based on density differences, analysis software was used to distinguish rock matrix components and pores by grayscale, and the distribution of macropores and karst caves with diameters greater than 400 μm was analyzed. S3. By detecting columnar samples using nuclear magnetic resonance, a distribution map of the porosity range of dolomite samples with a diameter of less than 1000 μm was obtained. S4. The distribution data of macropores and cavities with a diameter greater than 400 μm in step S2 are fused with the distribution map of pores with a diameter less than 1000 μm in step S3 to obtain the content and distribution of pores and cavities in dolomite.

2. The comprehensive quantitative characterization method for the full-size dolomite reservoir space according to claim 1, characterized in that, Step S1 also includes characterizing the pore type and occurrence of dolomite: The cut sample was made into a cast thin section, and the cast thin section was scanned by a polarizing microscope to obtain the type and distribution map of macroscopic pores; By scanning the thin sections of the casting with a scanning electron microscope, the types and distribution maps of micropores were obtained. The types and distribution maps of macropores were then fused with the types and distribution maps of micropores to obtain the pore types and occurrence of dolomite.

3. The comprehensive quantitative characterization method for the full-size dolomite reservoir space according to claim 1, characterized in that: In step S1, the diameter of the cylindrical sample is 25 mm and the length is 40 mm to 80 mm.

4. The comprehensive quantitative characterization method for the full-size dolomite reservoir space according to claim 1, characterized in that: In step S2, the rock matrix components include calcite and dolomite.

5. The comprehensive quantitative characterization method for the full-size dolomite reservoir space according to claim 1, characterized in that: In step S4, the pore distribution data from industrial CT scans and nuclear magnetic resonance are fused to obtain the pore volume corresponding to each pore size segment of the dolomite, and the total porosity of the dolomite sample is calculated. Compare the total porosity with the total porosity measured by helium. If the error between the two is large, repeat steps S1 to S4 to finally obtain the content and distribution of pores and voids in the dolomite.

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