Shaft sand return type identification method

Abstract

The invention discloses a shaft return sand type identification method, which belongs to the technical field of oil-gas exploration and development, and comprises the following steps: collecting an original fracturing sand sample and a shaft return sand sample which are subjected to sand fracturing, drying the original fracturing sand sample and the shaft return sand sample which are subjected to sand fracturing, and grinding until the granularity is less than 200 meshes; through X-ray fluorescence spectrum analysis, macroscopic element composition analysis of the sample is realized, and through X-ray diffraction analysis, macroscopic component analysis and microscopic crystal structure analysis of the sample are realized. Wherein the crystallinity and unit cell parameter analysis is mainly used for analyzing the whole component structure of the fracturing sand and the shaft return sand, so that the macroscopic component structure analysis of the sample is realized; and finally determining the identification of the sand return type of the shaft.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas exploration and development, and particularly relates to a method for identifying wellbore sand return types. Background Art

[0002] The Jurassic Shaximiao Formation in the Sichuan Basin is rich in oil and gas resources and possesses the geological conditions for the formation of large and medium-sized gas fields. However, the unique lithology, physical properties, and sensitivity of the reservoirs in this region introduce a degree of potential for reservoir damage, making it highly susceptible to reservoir damage during drilling and reservoir stimulation.

[0003] By using fracturing sand in the sand-added fracturing process of the Shaximiao Formation reservoir and adopting "multi-scale high-density" and other fracturing technologies during the backflow of the fracturing fluid, the reservoir damage caused by the impact of sand particles can be avoided to a certain extent. However, it was found in the actual production site that some production wells still have serious wellbore sand return problems, which greatly restricts the gas well production capacity, affects the normal operation of the ground gathering and transportation process, and increases the difficulty of efficient development of gas wells. Therefore, it is urgent to take corresponding solutions according to the type of wellbore sand return.

[0004] Wellbore sand return type identification technology has important applications in oil and gas exploration and development. It provides important evidence and guidance for identifying reservoir characteristics, determining fluid properties, analyzing geological structures, studying paleontology and stratigraphic chronology, and engineering applications. Furthermore, this technology has a positive impact on analyzing wellbore stability and wellbore quality, promoting oil and gas fluid flow, and improving oil and gas recovery.

[0005] Wellbore sand return refers to the return of sand from the wellbore to the ground during the gas well production process. This phenomenon usually occurs in the middle and late stages of gas well production. Understanding the type of wellbore sand return and optimizing the production system based on it is the key to improving gas well productivity.

[0006] However, existing technical methods are immature and often rely on single-factor identification, lacking a systematic identification method that combines macro and micro factors. As a result, the identification of wellbore sand return types is still unclear, hindering the normal implementation of a series of tasks such as oil and gas well productivity evaluation, wellbore stability analysis, and surface and wellbore process optimization. Therefore, it is necessary to establish a wellbore sand return type identification method to solve this problem. Summary of the Invention

[0007] This invention addresses the existing lack of a systematic method for identifying wellbore sand return types at both macro and micro scales. This method utilizes a wellbore sand return type identification method that uses X-ray fluorescence spectroscopy to analyze the sample's macroscopic elemental composition, and X-ray diffraction analysis to analyze both the sample's macroscopic components and microscopic crystal structure. Crystallinity analysis primarily analyzes the overall compositional structure of fracturing sand and wellbore sand return, thereby enabling macroscopic compositional analysis of the sample and ultimately confirming the wellbore sand return type.

[0008] The purpose of the present invention is achieved through the following technical solutions: A method for identifying the type of sand return in a wellbore comprises the following steps: Step S1, collecting the original fracturing sand sample and the wellbore return sand sample for sand fracturing, drying the original fracturing sand sample and the wellbore return sand sample for sand fracturing, and grinding them to a particle size of less than 200 mesh; Step S2: selecting the original fracturing sand sample that has been dried and ground in step S1 and subjected to sand fracturing, and performing X-ray diffraction analysis to obtain an X-ray diffraction spectrum of the original fracturing sand sample; Step S3: Select a portion of the wellbore sand sample after drying and grinding in step S1, perform X-ray diffraction analysis, and obtain an X-ray diffraction spectrum of the wellbore sand sample; Step S4: Compare the X-ray diffraction spectra of the original fracturing sand sample and the wellbore return sand sample, and determine whether there are new mineral species, changes in mineral content, and changes in crystallinity in the wellbore return sand sample based on the number, intensity, and overall changes of diffraction peaks; Step S5: Analyze the X-ray diffraction spectra of the original fracturing sand sample and the wellbore return sand sample using the X-ray diffraction full spectrum fitting method to confirm whether the mineral unit cell parameters have changed; Step S6: Confirm the wellbore sand return type based on the comparison results in step S4 and step S5.

[0009] Furthermore, the X-ray diffraction analysis in step S2 and step S3 must comply with the relevant requirements of SY / T 5163-2018: X-ray diffraction analysis method of clay minerals and common non-clay minerals in sedimentary rocks.

[0010] Furthermore, in step S4, an increase in the number of diffraction peaks indicates that new minerals are generated; changes in the intensity and half-peak width of the diffraction peaks indicate that the mineral content has changed; and an increase or decrease in the overall intensity of the diffraction curve indicates that the mineral crystallinity has changed.

[0011] Furthermore, in step S5, the X-ray diffraction full spectrum fitting method must meet the quality requirements of the X-ray diffraction Rietveld pattern full spectrum fitting correction.

[0012] Furthermore, the wellbore sand return type includes formation sand return wellbore sand return type A, formation sand return-fracture sand wellbore sand return type A, and fracturing sand return wellbore sand return type A.

[0013] Furthermore, the return formation sand wellbore sand type A refers to changes in the four parameters of mineral type, mineral content, crystallinity and unit cell parameters; the return formation sand-fracture sand wellbore sand type A refers to changes in at least one of the four parameters of mineral type, mineral content, crystallinity and unit cell parameters; the return fracturing sand wellbore sand type A refers to no changes in the four parameters of mineral type, mineral content, crystallinity and unit cell parameters.

[0014] Furthermore, the method further includes step S7, selecting a portion of the original fracturing sand sample that has been dried and ground in step S1 and subjected to sand fracturing, and performing X-ray fluorescence spectrometry analysis to obtain the element types and contents of the original fracturing sand sample; Step S8: Select a portion of the wellbore sand sample dried and ground in step S1, and perform X-ray fluorescence spectrometry analysis to obtain the element types and contents of the wellbore sand sample; Step S9: Compare the element types and contents of the original fracturing sand sample and the wellbore return sand sample to determine whether there are new element types and whether the element contents have changed; Step S10: Confirm the wellbore sand return type based on the comparison results in step S4, step S5 and step S9.

[0015] Furthermore, the X-ray fluorescence spectrometry analysis in step S7 and step S8 must comply with the relevant requirements of JB / T 11145-2017: X-ray fluorescence spectrometer.

[0016] Furthermore, the wellbore sand return type includes formation sand return wellbore sand return type B, formation sand return-fracture sand wellbore sand return type B, and fracturing sand return wellbore sand return type B.

[0017] Furthermore, the return formation sand wellbore sand type B refers to changes in at least 5 of the 6 parameters, namely, element type, element content, mineral type, mineral content, crystallinity and unit cell parameters; the return formation sand-fracture sand wellbore sand type B refers to changes in 2-4 of the 6 parameters, namely, element type, element content, mineral type, mineral content, crystallinity and unit cell parameters; the return fracturing sand wellbore sand type B refers to changes in at most 1 of the 6 parameters, namely, element type, element content, mineral type, mineral content, crystallinity and unit cell parameters.

[0018] The beneficial effects of this technical solution are as follows: 1. The present invention provides a method for identifying the type of sand return in wellbore. By integrating X-ray fluorescence spectroscopy and X-ray diffraction techniques and applying the viewpoints of elemental geochemistry and crystallography, it achieves a systematic identification of samples from both microscopic elements and macroscopic components, avoiding the cognitive errors caused by the uncertainty of a single identification method, and can meet the needs of analyzing the type of sand return in wellbore of various oil and gas wells.

[0019] 2. The present invention provides a method for identifying the type of sand return in a wellbore, establishes a comprehensive and systematic identification index, uses statistical identification viewpoints, selects identification conditions from six identification items, and determines the type of sand return in a wellbore, thereby avoiding human errors that may occur due to insufficient identification basis. The identification index covers both microscopic and macroscopic aspects, and can meet the comprehensive analysis of different types of sand return in a wellbore.

[0020] 3. The present invention provides a method for identifying the type of sand return from a wellbore, which mainly relies on two technologies: X-ray fluorescence spectroscopy and X-ray diffraction. The test object only requires a powder sample, and has the advantages of fast analysis and testing speed, no damage to the sample, and accurate identification. It is particularly suitable for analyzing sand return samples from oil and gas wellbores.

[0021] Fourth, the present invention provides a method for identifying the type of wellbore sand. This method uses X-ray fluorescence spectroscopy to analyze the macroscopic elemental composition of the sample, and X-ray diffraction analysis to analyze both the macroscopic component and microscopic crystal structure of the sample. Crystallinity analysis primarily analyzes the overall composition and structure of fracturing sand and wellbore sand, thereby enabling macroscopic compositional analysis of the sample.

[0022] 5. The present invention provides a method for identifying the type of sand returned from a wellbore. With the help of X-ray diffraction full spectrum fitting and refinement, it can more accurately determine the crystallinity and unit cell parameter values ​​of the sample. It integrates the element and crystal structure identification methods and can reasonably identify the type of sand returned from the wellbore from both the macroscopic composition structure and microscopic crystal structure of the sample. It plays an important supporting role in the evaluation of sand fracturing transformation of the reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is an X-ray diffraction spectrum of type A of the back-sand wellbore of the formation sand in the present invention; FIG2 is an X-ray diffraction spectrum of the formation sand-fracture sand wellbore reverse sand type A in the present invention; Figure 3 This is the X-ray diffraction spectrum of the back-fracture sand wellbore type A in the present invention; DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0025] Example 1 A method for identifying the type of sand return in a wellbore comprises the following steps: Step S1, collecting the original fracturing sand sample and the wellbore return sand sample for sand fracturing, drying the original fracturing sand sample and the wellbore return sand sample for sand fracturing, and grinding them to a particle size of less than 200 mesh; Step S2: selecting the original fracturing sand sample that has been dried and ground in step S1 and subjected to sand fracturing, and performing X-ray diffraction analysis to obtain an X-ray diffraction spectrum of the original fracturing sand sample; Step S3: Select a portion of the wellbore sand sample after drying and grinding in step S1, perform X-ray diffraction analysis, and obtain an X-ray diffraction spectrum of the wellbore sand sample; Step S4: Compare the X-ray diffraction spectra of the original fracturing sand sample and the wellbore return sand sample, and determine whether there are new mineral species, changes in mineral content, and changes in crystallinity in the wellbore return sand sample based on the number, intensity, and overall changes of diffraction peaks; Step S5: Analyze the X-ray diffraction spectra of the original fracturing sand sample and the wellbore return sand sample using the X-ray diffraction full spectrum fitting method to confirm whether the mineral unit cell parameters have changed; The X-ray diffraction full spectrum fitting method is an existing technology (which has been published in the Modern Physics Basics Series Collector's Edition "Determination of Crystal Structure by Powder Diffraction" edited by Liang Jingkui), which includes obtaining experimental diffraction spectra, determining the initial crystal structure and constructing theoretical diffraction spectra.

[0026] Obtain experimental diffraction spectrum: Perform X-ray diffraction pattern test on the sample to obtain the experimental spectrum. The test conditions are shown in 5.2.1.

[0027] Determine the initial crystal structure: Based on the mineral types and element information identified by rock thin section identification, scanning electron microscopy and energy spectrum, use ICSD or ICDD (crystal structure database) to design the initial crystal structure model of the mineral.

[0028] Construct a theoretical diffraction spectrum: Use the Pseudo-Voigt function as the peak shape function to fit the X-ray diffraction peak shape and preliminarily construct a theoretical diffraction spectrum; repeatedly compare the theoretical diffraction spectrum with the experimental spectrum, and use the least squares principle to repeatedly refine the crystal structure parameters such as space group, lattice constant, atomic coordinates, and peak shape function parameters such as diffraction angle, half-width, and preferred orientation until the constructed theoretical diffraction spectrum is as consistent as possible with the experimental spectrum.

[0029] Step S6: Confirm the wellbore sand return type based on the comparison results in step S4 and step S5.

[0030] Furthermore, the X-ray diffraction analysis in step S2 and step S3 must comply with the relevant requirements of SY / T5163-2018: X-ray diffraction analysis method of clay minerals and common non-clay minerals in sedimentary rocks.

[0031] Furthermore, in step S4, an increase in the number of diffraction peaks indicates that new minerals are generated; changes in the intensity and half-peak width of the diffraction peaks indicate that the mineral content has changed; and an increase or decrease in the overall intensity of the diffraction curve indicates that the mineral crystallinity has changed.

[0032] Furthermore, in step S5, the X-ray diffraction full spectrum fitting method must meet the X-ray diffraction Rietveld pattern full spectrum fitting correction quality requirements. The fitting convergence value requires the weighted pattern residual variance factor Rwp < 10 and the goodness of fit factor GoƒF between 1.0 and 1.5.

[0033] Furthermore, the wellbore sand return type includes the formation sand return wellbore sand return type A (such as Figure 1 As shown), return formation sand-fracture sand wellbore back sand type A (as shown Figure 2 ) and back-fracture sand wellbore reverse sand type A (as shown Figure 3 shown).

[0034] Furthermore, the return formation sand wellbore sand type A refers to changes in the four parameters of mineral type, mineral content, crystallinity and unit cell parameters; the return formation sand-fracture sand wellbore sand type A refers to changes in at least one of the four parameters of mineral type, mineral content, crystallinity and unit cell parameters; the return fracturing sand wellbore sand type A refers to no changes in the four parameters of mineral type, mineral content, crystallinity and unit cell parameters.

[0035] Example 2 This embodiment adopts a method for identifying the type of sand return in a wellbore according to embodiment 1, including the following steps: Step S1, collecting the original fracturing sand sample and the wellbore return sand sample for sand fracturing, drying the original fracturing sand sample and the wellbore return sand sample for sand fracturing, and grinding them to a particle size of less than 200 mesh; Step S2: selecting the original fracturing sand sample that has been dried and ground in step S1 and subjected to sand fracturing, and performing X-ray diffraction analysis to obtain an X-ray diffraction spectrum of the original fracturing sand sample; Step S3: Select a portion of the wellbore sand sample after drying and grinding in step S1, perform X-ray diffraction analysis, and obtain an X-ray diffraction spectrum of the wellbore sand sample; Step S4: Compare the X-ray diffraction spectra of the original fracturing sand sample and the wellbore return sand sample, and determine whether there are new mineral species, changes in mineral content, and changes in crystallinity in the wellbore return sand sample based on the number, intensity, and overall changes of diffraction peaks; Step S5: Analyze the X-ray diffraction spectra of the original fracturing sand sample and the wellbore return sand sample using the X-ray diffraction full spectrum fitting method to confirm whether the mineral unit cell parameters have changed; Step S7: Select the original fracturing sand sample that has been dried and ground in step S1 and then subjected to sand fracturing, and perform X-ray fluorescence spectrometry analysis to obtain the element types and contents of the original fracturing sand sample; Step S8: Select a portion of the wellbore sand sample dried and ground in step S1, and perform X-ray fluorescence spectrometry analysis to obtain the element types and contents of the wellbore sand sample; Step S9: Compare the element types and contents of the original fracturing sand sample and the wellbore return sand sample to determine whether there are new element types and whether the element contents have changed; Step S10: Confirm the wellbore sand return type based on the comparison results in step S4, step S5 and step S9.

[0036] Furthermore, the X-ray diffraction analysis in step S2 and step S3 must comply with the relevant requirements of SY / T 5163-2018: X-ray diffraction analysis method of clay minerals and common non-clay minerals in sedimentary rocks.

[0037] Furthermore, in step S4, an increase in the number of diffraction peaks indicates that new minerals are generated; changes in the intensity and half-peak width of the diffraction peaks indicate that the mineral content has changed; and an increase or decrease in the overall intensity of the diffraction curve indicates that the mineral crystallinity has changed.

[0038] Furthermore, in step S5, the X-ray diffraction full spectrum fitting method must meet the quality requirements of the X-ray diffraction Rietveld pattern full spectrum fitting correction.

[0039] Furthermore, the X-ray fluorescence spectrometry analysis in step S7 and step S8 must comply with the relevant requirements of JB / T 11145-2017: X-ray fluorescence spectrometer.

[0040] Furthermore, the wellbore sand return type includes formation sand return wellbore sand return type B, formation sand return-fracture sand wellbore sand return type B, and fracturing sand return wellbore sand return type B.

[0041] Furthermore, the return formation sand wellbore sand type B refers to changes in at least 5 of the 6 parameters, namely, element type, element content, mineral type, mineral content, crystallinity and unit cell parameters; the return formation sand-fracture sand wellbore sand type B refers to changes in 2-4 of the 6 parameters, namely, element type, element content, mineral type, mineral content, crystallinity and unit cell parameters; the return fracturing sand wellbore sand type B refers to changes in at most 1 of the 6 parameters, namely, element type, element content, mineral type, mineral content, crystallinity and unit cell parameters.

[0042] Compared with the wellbore return sand type A of formation sand, the wellbore return sand type A of formation sand and fracturing sand, and the wellbore return sand type A of fracturing sand, the wellbore return sand type B of formation sand, the wellbore return sand type B of formation sand and fracturing sand, and the wellbore return sand type B of fracturing sand are more accurately identified.

[0043] The beneficial effects of this technical solution are as follows: 1. The present invention provides a method for identifying the type of sand return in wellbore. By integrating X-ray fluorescence spectroscopy and X-ray diffraction techniques and applying the viewpoints of elemental geochemistry and crystallography, it achieves a systematic identification of samples from both microscopic elements and macroscopic components, avoiding the cognitive errors caused by the uncertainty of a single identification method, and can meet the needs of analyzing the type of sand return in wellbore of various oil and gas wells.

[0044] 2. The present invention provides a method for identifying the type of sand return in a wellbore, establishes a comprehensive and systematic identification index, uses statistical identification viewpoints, selects identification conditions from six identification items, and determines the type of sand return in a wellbore, thereby avoiding human errors that may occur due to insufficient identification basis. The identification index covers both microscopic and macroscopic aspects, and can meet the comprehensive analysis of different types of sand return in a wellbore.

[0045] 3. The present invention provides a method for identifying the type of sand return from a wellbore, which mainly relies on two technologies: X-ray fluorescence spectroscopy and X-ray diffraction. The test object only requires a powder sample, and has the advantages of fast analysis and testing speed, no damage to the sample, and accurate identification. It is particularly suitable for analyzing sand return samples from oil and gas wellbores.

[0046] Fourth, the present invention provides a method for identifying the type of wellbore sand. This method uses X-ray fluorescence spectroscopy to analyze the macroscopic elemental composition of the sample, and X-ray diffraction analysis to analyze both the macroscopic component and microscopic crystal structure of the sample. Crystallinity analysis primarily analyzes the overall composition and structure of fracturing sand and wellbore sand, thereby enabling macroscopic compositional analysis of the sample.

[0047] 5. The present invention provides a method for identifying the type of sand returned from a wellbore. With the help of X-ray diffraction full spectrum fitting and refinement, it can more accurately determine the crystallinity and unit cell parameter values ​​of the sample. It integrates the element and crystal structure identification methods and can reasonably identify the type of sand returned from the wellbore from both the macroscopic composition structure and microscopic crystal structure of the sample. It plays an important supporting role in the evaluation of sand fracturing transformation of the reservoir.

[0048] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for identifying the type of sand return in a wellbore, characterized in that: The following steps are involved: Step S1, collecting the original fracturing sand sample and the wellbore return sand sample for sand fracturing, drying the original fracturing sand sample and the wellbore return sand sample for sand fracturing, and grinding them to a particle size of less than 200 mesh respectively; Step S2: selecting the original fracturing sand sample that has been dried and ground in step S1 and subjected to sand fracturing, and performing X-ray diffraction analysis to obtain an X-ray diffraction spectrum of the original fracturing sand sample; Step S3: Select a portion of the wellbore sand sample after drying and grinding in step S1, perform X-ray diffraction analysis, and obtain an X-ray diffraction spectrum of the wellbore sand sample; Step S4: Compare the X-ray diffraction spectra of the original fracturing sand sample and the wellbore return sand sample, and determine whether there are new mineral species, changes in mineral content, and changes in crystallinity in the wellbore return sand sample based on the number, intensity, and overall changes of diffraction peaks; Step S5: Analyze the X-ray diffraction spectra of the original fracturing sand sample and the wellbore return sand sample using the X-ray diffraction full spectrum fitting method to confirm whether the mineral unit cell parameters have changed; Step S6: Confirm the wellbore sand return type based on the comparison results in step S4 and step S5.

2. A method for identifying the type of sand return in a wellbore according to claim 1, characterized in that: The X-ray diffraction analysis in step S2 and step S3 must comply with the relevant requirements of SY / T 5163-2018: X-ray diffraction analysis method for clay minerals and common non-clay minerals in sedimentary rocks.

3. A method for identifying the type of sand return in a wellbore according to claim 1, characterized in that: In step S4, an increase in the number of diffraction peaks indicates the generation of new minerals; changes in the intensity and half-peak width of the diffraction peaks indicate changes in the mineral content; and an increase or decrease in the overall intensity of the diffraction curve indicates a change in the mineral crystallinity.

4. A method for identifying the type of sand return in a wellbore according to claim 1, characterized in that: In step S5, the X-ray diffraction full spectrum fitting method must meet the quality requirements of the X-ray diffraction Rietveld pattern full spectrum fitting correction.

5. The method for identifying the type of sand return in a wellbore according to claim 1, wherein: The wellbore sand return types include formation sand return wellbore sand return type A, formation sand return-fracture sand wellbore sand return type A, and fracturing sand return wellbore sand return type A.

6. A method for identifying the type of sand return in a wellbore according to claim 5, characterized in that: The return sand type A of the formation sand wellbore refers to changes in the four parameters of mineral type, mineral content, crystallinity and unit cell parameters; the return sand type A of the formation sand-fracture sand wellbore refers to changes in at least one of the four parameters of mineral type, mineral content, crystallinity and unit cell parameters; the return sand type A of the fracturing sand wellbore refers to no changes in the four parameters of mineral type, mineral content, crystallinity and unit cell parameters.

7. A method for identifying the type of sand return in a wellbore according to claim 1, characterized in that: The method further includes step S7, selecting a portion of the original fracturing sand sample that has been dried and ground in step S1 and subjected to sand fracturing, and performing X-ray fluorescence spectrometry analysis to obtain the element types and contents of the original fracturing sand sample; Step S8: Select a portion of the wellbore sand sample dried and ground in step S1, and perform X-ray fluorescence spectrometry analysis to obtain the element types and contents of the wellbore sand sample; Step S9: Compare the element types and contents of the original fracturing sand sample and the wellbore return sand sample to determine whether there are new element types and whether the element contents have changed; Step S10: Confirm the wellbore sand return type based on the comparison results in step S4, step S5 and step S9.

8. A method for identifying the type of sand return in a wellbore according to claim 7, characterized in that: The X-ray fluorescence spectrometry analysis in step S7 and step S8 must comply with the relevant requirements of JB / T 11145-2017: X-ray fluorescence spectrometer.

9. A method for identifying the type of sand return in a wellbore according to claim 8, characterized in that: The wellbore sand return types include formation sand return wellbore sand return type B, formation sand return-fracture sand wellbore sand return type B, and fracturing sand return wellbore sand return type B.

10. A method for identifying the type of sand return in a wellbore according to claim 1, characterized in that: The return sand type B of the formation sand wellbore refers to changes in at least 5 of the 6 parameters: element type, element content, mineral type, mineral content, crystallinity and unit cell parameters; the return sand type B of the formation sand-fracture sand wellbore refers to changes in 2-4 of the 6 parameters: element type, element content, mineral type, mineral content, crystallinity and unit cell parameters; the return sand type B of the fracturing sand wellbore refers to changes in at most 1 of the 6 parameters: element type, element content, mineral type, mineral content, crystallinity and unit cell parameters.

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