Experimental method for identifying fluid in rock core by using CT (Computed Tomography) scanning

Abstract

The invention discloses an experimental method for identifying fluid in a rock core by using CT (Computed Tomography) scanning, which comprises the following steps of: filling target fluid into a gap between a target rock core and a heat-shrinkable sleeve through the heat-shrinkable sleeve which is prepared in advance and is provided with an annular gap, and scanning and identifying a target fluid area by using CT scanning equipment according to the target fluid area; and the target fluid is substituted into the body three-dimensional data volume of the target rock core, so that the target fluid can be easily identified. According to the method, the gray value range of the target fluid is obtained by filling the target fluid at the fixed part around the rock core according to the fact that different substances present different gray values under CT scanning, and the gray value range is substituted into the rock core, so that the distribution condition of the target fluid in the rock core can be accurately judged, and the accuracy of the target fluid distribution is improved. Therefore, the technical problem that the microscopic occurrence condition of the fluid in the rock core cannot be visually obtained in the prior art is effectively solved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas geological exploration, and in particular relates to an experimental method for fluid identification in rock cores by using CT scanning. Background Art

[0002] Rocks in nature are porous media with single or multiple spatial structures such as pores, holes, and cracks. In oil and gas reservoirs, the pore space of formation rocks contains fluids such as oil, gas, and formation water. For the oil and gas geological exploration industry, the identification of fluids in formation rocks is a basic link in the industry. Accurate identification of fluids not only reflects the geological environment during the formation deposition process, but also is an important basis for judging the damage of working fluids to reservoirs during drilling and development.

[0003] At present, in the research of core fluid identification, conventional methods for the identification of formation fluids include seismic and well logging, which mainly achieve the purpose of identifying fluids in the formation through the inversion of seismic waves and the interpretation of well logging data. However, the interpretation of seismic and well logging is extremely dependent on the interpretation model, that is, the accuracy of the interpretation model determines the accuracy of the fluid identification results. However, since the interpretation model involves a lot of data and is prone to errors, it is easy to lead to inaccurate identification results. In addition, conventional identification methods such as seismic and well logging cannot intuitively characterize the distribution of fluids in the core. Therefore, in practical applications, there are still technical problems such as difficulty in accurate fluid identification and difficulty in displaying the fluid distribution during the fluid identification process.

[0004] Furthermore, the patent document with the publication number CN114706124A discloses a fluid identification method and system based on the combination of electromagnetic and seismic. The fluid identification method includes the following steps: obtaining seismic data of the area to be identified, and establishing a geological structure model based on the seismic data; performing finite element division on the geological structure model; obtaining the resistivity parameters of each physical stratum in the area to be identified, and establishing a geological electrical model based on the resistivity parameters and the geological structure model; performing electromagnetic inversion on the geological electrical model as a division constraint to obtain inverted resistivity profile data; extracting the fluid resistivity distribution data of the reservoir from the inversion results of each stratum, and combining it with the resistivity interpretation template for fluid identification. This method forms a survey method that is sensitive to both stratum structure and reservoir fluid by combining electro-seismic methods, which can improve the accuracy of reservoir fluid identification, determine the law of oil and gas distribution, provide a basis for delineating favorable areas of oil reservoirs, and improve the level of oilfield development. However, in practical applications, this method still has the following technical problems: 1. This method requires statistics of a large amount of resistivity data and weighting to obtain the corresponding resistivity empirical values ​​for dividing underground oil, gas and water layers. The process is relatively complicated, and under normal circumstances, oil and gas are not conductive, so it is difficult to distinguish oil layers and gas layers based on resistivity values.

[0005] 2. This method is only for the general identification and classification of reservoir fluids at larger formation sizes (meter level), and it is difficult to effectively identify the fluids.

[0006] In addition, in laboratory core experimental analysis, nuclear magnetic resonance technology is usually used to identify fluids in cores. This technology is mainly based on the different nuclear magnetic resonance relaxation characteristics of different fluids in the reservoir for qualitative identification and quantitative calculation. There are two specific methods. One is to use the different observation mode signals of one-dimensional nuclear magnetic resonance logging to process and analyze the fluids, and the other is to use two-dimensional or even multi-dimensional nuclear magnetic resonance technology to directly identify the fluids. However, there are two difficulties in using nuclear magnetic resonance for fluid identification. One is that it is necessary to construct a corresponding fluid identification map based on a series of core nuclear magnetic resonance experiments. However, due to the differences in geological backgrounds such as sedimentation, diagenesis, and structure in different basins, the fluid boundaries in the map divided based on the experimental results of limited samples are not universal. Second, nuclear magnetic resonance cannot intuitively show the microscopic occurrence of fluids in porous media.

[0007] At present, CT scanning technology has been widely used in solid mineral and pore structure identification, but CT scanning has not yet been applied in fluid identification. With the introduction of new experimental analysis methods, it is possible to use CT scanning to identify fluids and characterize the fluid distribution in rock cores. CT scanning is non-destructive to rock samples and is convenient and fast. Therefore, an experimental method for fluid identification in rock cores can be established based on CT scanning technology. Summary of the invention

[0008] The purpose of the present invention is to overcome the above technical problems existing in the prior art, and to provide an experimental method for fluid identification in rock cores using CT scanning. The experimental method is based on the principle that different substances present different grayscale values ​​under CT scanning. By filling the target fluid (the fluid to be identified in the rock sample) at a fixed position around the rock core, the grayscale value range of the target fluid is obtained, and the grayscale value range is substituted into the rock core, thereby accurately determining the distribution of the target fluid in the rock core, thereby effectively solving the technical difficulty that the original technology cannot intuitively obtain the microscopic occurrence of the fluid in the rock core.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows: An experimental method for fluid identification in rock cores using CT scanning comprises the following steps: Step 1: using a transparent material to prepare a heat shrinkable tube that matches the target core, wherein the heat shrinkable tube is provided with an annular gap protruding from the inside to the outside; Step 2: seal one end of the heat shrink tube, install the target core into the heat shrink tube, and make the annular gap located in the middle of the target core; Step 3: Obtain the target fluid and inject the target fluid into the gap between the target core and the heat shrink tubing from the unblocked end of the heat shrink tubing until the target fluid fills the annular gap of the heat shrink tubing and the liquid level of the target fluid is below the end port; Step 4: placing the heat shrink tubing containing the target core after the treatment in step 3 in a CT scanning device for scanning, and obtaining a three-dimensional data volume after scanning; Step 5: Analyze the obtained three-dimensional data volume, identify the target fluid area according to the annular gap, and divide the gray value range of the target fluid area; Step 6: Obtain the three-dimensional data volume of the target core, substitute the grayscale value range of the target fluid area into the three-dimensional data volume, and the corresponding area with the grayscale value range in the target core is the position occupied by the target fluid in the pores of the target core, thereby completing the identification of the fluid in the core.

[0010] The preparation method of the heat shrinkable sleeve is as follows: Step S1: preparing a heat shrinkable tube forming mold, the forming mold comprising an end mold and a middle mold; wherein the end mold comprises a base and a convex column integrally formed on the base, the convex column is provided with an annular boss for forming an annular gap in the heat shrinkable tube, and the middle mold is a cylindrical structure of the same size as the convex column; Step S2: placing the middle mold on the convex column of the end mold and wrapping it with a transparent heat shrink sleeve; Step S3: using hot air equipment to blow the heat shrink sleeve to shrink the heat shrink sleeve and wrap the molding mold tightly; Step S4: Pull the heat shrink sleeve out of the molding die to obtain a heat shrink sleeve including an annular gap.

[0011] The end mold is made of stainless steel, and the middle mold is made of a core sample.

[0012] The end of the heat shrinkable sleeve is sealed by a middle mold.

[0013] The hot air equipment is a hot air blower, wherein when the hot air blower blows the heat shrink sleeve corresponding to the end mold, the blowing time is less than 1 minute; when the hot air blower blows the heat shrink sleeve corresponding to the middle mold, the blowing time is greater than 3 minutes.

[0014] The target fluid includes formation water, crude oil and drilling mud.

[0015] The annular gap is an annular structure or a square structure.

[0016] The raised height of the annular gap is 2-4 mm, and the raised width is 3-6 mm.

[0017] When the target fluid is filled into the gap between the target core and the heat shrinkable tube, the distance between the liquid surface of the target fluid and the port of the heat shrinkable tube is greater than 3 cm.

[0018] The parameters of the CT scanning device during scanning are: Scanning sample size restrictions: diameter less than 260mm, height less than 420mm, weight less than 20kg; X-ray source resolution: minimum focus size ≤ 3μm, detail resolution ≤ 2μm; Number of photos: 2000, exposure time: 500ms, voltage: 150KV, current: 130mA.

[0019] The advantages of adopting the present invention are: 1. The experimental method of the present invention uses a pre-prepared heat shrink tubing with an annular gap to fill the target fluid into the gap between the target core and the heat shrink tubing, and then uses a CT scanning device to scan, so that the target fluid can be identified. The present invention uses the different grayscale values ​​of different substances under CT scanning to fill the target fluid that can be identified by shape around the core, and then divides the grayscale value range of the target fluid according to the grayscale value, and substitutes the grayscale value range into the target core, thereby more accurately judging the distribution of the target fluid in the target core. Compared with the prior art, the present invention effectively solves the technical problem that the microscopic occurrence of fluids in the formation cannot be intuitively obtained.

[0020] 2. The present invention uses a heat shrink sleeve plus mold blow molding to construct a space that can accommodate the target core and the target fluid, and the middle mold can be used to block the heat shrink sleeve. This structure has three advantages: first, the close fit between the heat shrink sleeve and the middle mold prevents the target fluid from penetrating downward; second, the heat shrink sleeve has a certain elasticity, which is convenient for filling the target fluid; third, the mold, heat shrink sleeve and target core are of uniform size, and the three sizes are compatible, so there is no need to specially modify the shape of the target core, which is conducive to comparing the experimental results with other experimental test results of the core, such as porosity, permeability and saturation.

[0021] 3. The present invention utilizes the CT scanning method to identify the target fluid without damaging the target core. The identified target core can also be used for other experiments, thereby improving the utilization rate of the target core.

[0022] 4. The present invention is applicable to the identification of various fluids, including formation water, crude oil, drilling mud, etc., and has a wide range of applications.

[0023] 5. The present invention places the target core and the target fluid in a heat shrink tube at the same time, so that the target fluid and the target core can be scanned at the same time, avoiding the gray value changes caused by environmental influences, and thus facilitating a more accurate determination of the fluid distribution in the target core. Compared with the prior art, the present invention does not require steps such as model establishment and model substitution, and is the most direct fluid identification method with higher accuracy.

[0024] 6. The fluid identification result obtained by the present invention can intuitively display the three-dimensional spatial distribution of the fluid in the target core, and can also calculate the corresponding saturation, and has strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flow chart of the present invention; Figure 2 It is a schematic diagram of the overall structure after the target core is loaded; Figure 3 It is a schematic diagram of the overall structure after being filled with target fluid; Figure 4 This is the overall scan image obtained after CT scanning; Figure 5 for Figure 4 Scanning image of a portion of the area captured in ; Figure 6 It is a structural schematic diagram of the forming mold; Figure 7 It is a schematic diagram of the overall structure of the end mold, the middle mold and the heat shrink sleeve during blow molding; Figure 8 It is a schematic diagram of the structure in which an annular gap is formed by the heat shrink tubing after the end mold is pulled out.

[0026] The markings in the figure are: 1. heat shrink tubing, 2. annular gap, 3. end mold, 4. middle mold, 5. base, 6. boss, 7. annular boss, 8. target core. DETAILED DESCRIPTION

[0027] Example 1 This embodiment provides an experimental method for fluid identification in rock cores using CT scanning. Figure 1 As shown, it includes the following steps: Step 1: Use transparent material to prepare a heat shrink tube 1 that matches the target core 8. The heat shrink tube 1 is a hollow structure, and its shape and size match the shape and size of the target core 8 to be tested. The tube body is provided with an annular gap 2 protruding from the inside to the outside.

[0028] It should be noted that this step does not limit the preparation process of the heat shrinkable tube 1, and any conventional preparation method can be used.

[0029] Step 2: Since the heat shrink tube 1 is a hollow structure, a plug can be used to seal one end of the heat shrink tube 1 to prevent leakage when the target fluid is subsequently injected into the heat shrink tube 1. Figure 2 As shown, after the plugging is completed, the target core 8 is loaded into the heat shrinkable sleeve 1, and the annular gap 2 is located in the middle of the target core 8, so that the subject required for the experiment can be scanned in the subsequent CT scan.

[0030] It should be noted that in this step, the heat shrink tube 1 is preferably sealed first, and then the target core 8 is loaded into the heat shrink tube 1, but it is not actually limited to this preferred method. During the test, the target core 8 can also be first loaded into the heat shrink tube 1 and then the heat shrink tube 1 is sealed.

[0031] Step 3: Obtain the target fluid. Generally, the target fluid is obtained by sampling at the well site. If conditions are limited, the target fluid can also be prepared experimentally, but the prepared target fluid must be no less than 100 mL. Among them, the target fluid includes formation water, crude oil and drilling mud. That is, according to different needs, formation water, crude oil or drilling mud can be used as the target fluid.

[0032] like Figure 3 As shown, after obtaining the target fluid, the target fluid is filled into the gap between the target core 8 and the heat shrinkable tube 1 from the other unblocked end of the heat shrinkable tube 1 until the target fluid fills the annular gap 2 of the heat shrinkable tube 1 and the liquid level of the target fluid is below the end port.

[0033] To prevent the target fluid from overflowing during the scanning process, when the target fluid is filled into the gap between the target core 8 and the heat shrink tube 1 in this step, it is preferred that the distance between the liquid surface of the target fluid and the port of the heat shrink tube 1 is greater than 3 cm.

[0034] Step 4: Place the heat shrink tube 1 with the target core 8 after the treatment in step 3 in a CT scanning device for scanning. After the scanning is completed, the following is obtained: Figure 4 The three-dimensional data body shown includes a heat shrink tube 1, a target core 8 and a target fluid. Figure 5 The three views of a cube are shown. Figure 4 The area captured in the overall scan image shown has two functions: one is to eliminate artifact interference (CT scanning will form artifacts at the edge, so the cube is located in a more central position), and the other is to reduce the calculation area to meet the limitations of computing power and reservoir capacity, thereby achieving the effect of improving recognition accuracy and efficiency.

[0035] Among them, the parameters of the CT scanning device during scanning are: Scanning sample size restrictions: diameter less than 260mm, height less than 420mm, weight less than 20kg; X-ray source resolution: minimum focus size ≤ 3μm, detail resolution ≤ 2μm; Number of photos: 2000, exposure time: 500ms, voltage: 150KV, current: 130mA.

[0036] Step 5: Analyze the obtained three-dimensional data volume, identify the target fluid area according to the annular gap 2, and divide the gray value range of the target fluid area.

[0037] Step 6: Obtain the main body three-dimensional data volume of the target core 8, substitute the grayscale value range of the target fluid area into the main body three-dimensional data volume, and the corresponding area with the grayscale value range in the target core 8 is the position occupied by the target fluid in the pores of the target core 8, thereby completing the identification of the fluid in the core.

[0038] In summary, this method utilizes the principle that different substances have different grayscale values ​​under CT scanning. Fluid that can be identified by shape is filled around the core, and the grayscale value range of the fluid is divided according to the grayscale value. The grayscale value range is substituted into the core, and the distribution of the target fluid in the core can be judged more accurately.

[0039] Example 2 This embodiment provides an experimental method for fluid identification in rock cores using CT scanning based on embodiment 1. Figure 1 As shown, it includes the following steps: Step 1: Use transparent material to prepare a heat shrink tube 1 that matches the target core 8. The heat shrink tube 1 is a hollow structure, and its shape and size match the shape and size of the target core 8 to be tested. The tube body is provided with an annular gap 2 protruding from the inside to the outside.

[0040] The structure of the annular gap 2 in this step is varied, but the annular gap 2 is preferably set to an annular structure or a square structure. It should be noted that the annular gap 2 is an annular structure, which means that the annular gap 2 is an annular structure as a whole, and its cross section is an arc structure, specifically, the inner wall of the tube body of the heat shrinkable tube 1 protrudes outward in an arc structure. The annular gap 2 is a square structure, which means that the annular gap 2 is a square structure as a whole, and its cross section is a semi-square structure, specifically, the inner wall of the tube body of the heat shrinkable tube 1 protrudes outward in a square structure.

[0041] Step 2: Since the heat shrink tube 1 is a hollow structure, a plug can be used to seal one end of the heat shrink tube 1 to prevent leakage when the target fluid is subsequently injected into the heat shrink tube 1. Figure 2As shown, after the plugging is completed, the target core 8 is loaded into the heat shrinkable sleeve 1, and the annular gap 2 is located in the middle of the target core 8, so that the subject required for the experiment can be scanned in the subsequent CT scan.

[0042] Step 3: If Figure 3 As shown, after obtaining the target fluid, the target fluid is injected into the gap between the target core 8 and the heat shrinkable tube 1 from the other unblocked end of the heat shrinkable tube 1 until the target fluid fills the annular gap 2 of the heat shrinkable tube 1 and the liquid level of the target fluid is below the end port.

[0043] Step 4: Place the heat shrink tube 1 with the target core 8 after the treatment in step 3 in a CT scanning device for scanning. After the scanning is completed, the following is obtained: Figure 4 The three-dimensional data volume shown includes the heat shrink tube 1, the target core 8 and the target fluid.

[0044] Step 5: Analyze the obtained three-dimensional data volume, identify the target fluid area according to the annular gap 2, and divide the gray value range of the target fluid area.

[0045] Step 6: Obtain the main body three-dimensional data volume of the target core 8, substitute the grayscale value range of the target fluid area into the main body three-dimensional data volume, and the corresponding area with the grayscale value range in the target core 8 is the position occupied by the target fluid in the pores of the target core 8, thereby completing the identification of the fluid in the core.

[0046] In summary, this method utilizes the principle that different substances have different grayscale values ​​under CT scanning. Fluid that can be identified by shape is filled around the core, and the grayscale value range of the fluid is divided according to the grayscale value. The grayscale value range is substituted into the core, and the distribution of the target fluid in the core can be judged more accurately.

[0047] Example 3 This embodiment further defines the structure of the annular gap 2 on the basis of Embodiment 2. Specifically, in order to better reflect the distribution of the target fluid in the core, this embodiment sets the convex height of the annular gap 2 to 2-4 mm and the convex width of the annular gap 2 to 3-6 mm.

[0048] Further preferably, the protruding height of the annular gap 2 is 3 mm, and the protruding width of the annular gap 2 is 4 mm.

[0049] Example 4 This embodiment provides an experimental method for fluid identification in rock cores using CT scanning based on any one of the embodiments 1-3. Figure 1 As shown, it includes the following steps: Step 1: Use transparent material to prepare a heat shrink tube 1 that matches the target core 8. The heat shrink tube 1 is a hollow structure, and its shape and size match the shape and size of the target core 8 to be tested. The tube body is provided with an annular gap 2 protruding from the inside to the outside.

[0050] Step 2: Since the heat shrink tube 1 is a hollow structure, a plug can be used to seal one end of the heat shrink tube 1 to prevent leakage when the target fluid is subsequently injected into the heat shrink tube 1. Figure 2 As shown, after the plugging is completed, the target core 8 is loaded into the heat shrinkable sleeve 1, and the annular gap 2 is located in the middle of the target core 8, so that the subject required for the experiment can be scanned in the subsequent CT scan.

[0051] Step 3: If Figure 3 As shown, after obtaining the target fluid, the target fluid is injected into the gap between the target core 8 and the heat shrinkable tube 1 from the other unblocked end of the heat shrinkable tube 1 until the target fluid fills the annular gap 2 of the heat shrinkable tube 1 and the liquid level of the target fluid is below the end port.

[0052] Step 4: Place the heat shrink tube 1 with the target core 8 after the treatment in step 3 in a CT scanning device for scanning. After the scanning is completed, the following is obtained: Figure 4 The three-dimensional data volume shown includes the heat shrink tube 1, the target core 8 and the target fluid.

[0053] Step 5: Analyze the obtained three-dimensional data volume, identify the target fluid area according to the annular gap 2, and divide the gray value range of the target fluid area.

[0054] Step 6: Obtain the main body three-dimensional data volume of the target core 8, substitute the grayscale value range of the target fluid area into the main body three-dimensional data volume, and the corresponding area with the grayscale value range in the target core 8 is the position occupied by the target fluid in the pores of the target core 8, thereby completing the identification of the fluid in the core.

[0055] The preparation method of the heat shrinkable sleeve 1 in this embodiment is as follows: Step S1: Prepare a heat shrinkable tube 1 forming mold, the forming mold includes: Figure 6 The end mold 3 and the middle mold 4 are shown. The end mold 3 can be directly made of stainless steel material, and the middle mold 4 can be made of core samples.

[0056] Furthermore, the end mold 3 includes a base 5 and a boss 6 integrally formed on the base 5 , the boss 6 is provided with an annular boss 7 for forming an annular gap 2 on the heat shrinkable sleeve 1 , and the middle mold 4 is a cylindrical structure of the same size as the boss 6 .

[0057] It should be noted that the diameter of the protrusion 6 in the end mold 3 can be 2.5 cm, and the protrusion height of the annular boss 7 is not less than 2 mm, but preferably 2-4 mm. The protrusion width of the annular boss 7 is not less than 3 mm, but preferably 3-6 mm. The center position of the annular boss 7 is not less than 5 cm from the two ends of the protrusion 6. The diameter of the middle mold 4 is the same as the diameter of the protrusion 6, which is also 2.5 cm.

[0058] Step S2: placing the middle mold 4 on the convex column 6 of the end mold 3 so that the end faces of the two are closely fitted, and wrapping the middle mold 4 and the convex column 6 with a transparent heat shrink sleeve at the same time.

[0059] Step S3: Figure 7 As shown, a hot air device such as a hot air blower is used to blow the heat shrink sleeve, so that the heat shrink sleeve shrinks and tightly wraps the convex column 6 and the middle mold 4 of the molding mold.

[0060] It should be noted that, since this solution involves plugging the heat shrink sleeve 1, in order to reduce the plugging process, when preparing the heat shrink sleeve 1, the middle mold 4 can be directly used as a plug to plug the heat shrink sleeve 1. Specifically, when using a hot air blower to blow the heat shrink sleeve corresponding to the middle mold 4, the blow molding time should be greater than 3 minutes, so that the heat shrink sleeve and the middle mold 4 fit tightly, so that the middle mold 4 can play a plugging role. When using a hot air blower to blow the heat shrink sleeve corresponding to the end mold 3, the blow molding time should be less than 1 minute, so that the convex column 6 of the end mold 3 can be pulled out of the heat shrink sleeve.

[0061] Step S4: After the blow molding is completed, the heat shrink sleeve is pulled out from the molding mold to obtain Figure 8 The heat shrink sleeve 1 includes an annular gap 2. Since the heat shrink sleeve corresponding to the middle mold 4 is blown for a longer time, the middle mold 4 can play a role in plugging the heat shrink sleeve 1, thereby reducing additional plugging processes.

[0062] Example 5 This example uses the dense sandstone core of the Shaximiao Formation in the QL area of ​​the Sichuan Basin to conduct experiments as follows: Before the experiment, the porosity and permeability tests were first conducted to determine that the porosity of the target core was 15.65% and the permeability was 3.43 mD.

[0063] Step S1: preparing a heat shrink tubing that matches the target core.

[0064] Step S2: placing the target core in the heat shrinkable sleeve, and making the annular gap located in the middle of the target core, so as to facilitate the subsequent CT scanning to scan the core body.

[0065] Step S3: Obtain the target fluid and inject the target fluid into the gap between the target core and the heat shrink tubing from the port at the other unblocked end of the heat shrink tubing until the target fluid fills the annular gap of the heat shrink tubing and the liquid level of the target fluid is below the port at the end.

[0066] Step S4: Place the heat shrink tubing containing the target core after the treatment in step 3 in a CT scanning device for scanning, with 2000 photos, 500ms exposure time, 150KV voltage and 130mA current.

[0067] Step S5: Analyze the obtained three-dimensional data volume, identify the target fluid area according to the annular gap, and divide the grayscale value range of the target fluid area. The grayscale value range of the annular fluid in this sample is 8000~12000.

[0068] Step S6: Substitute the grayscale value range of 8000-12000 of the target fluid area into the three-dimensional data volume of the target core, obtain the corresponding grayscale value area in the target core, and then identify the position of the target fluid in the pores of the target core according to the obtained corresponding grayscale value area. And the applicant has verified by using existing conventional technical means that its recognition accuracy can reach 90%, which proves that this technology has a relatively accurate recognition effect.

[0069] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. An experimental method for fluid identification in rock cores using CT scanning, comprising the following steps: Step 1: using a transparent material to prepare a heat shrinkable tube that matches the target core, wherein the heat shrinkable tube is provided with an annular gap protruding from the inside to the outside; Step 2: seal one end of the heat shrink tube, install the target core into the heat shrink tube, and make the annular gap located in the middle of the target core; Step 3: Obtain the target fluid and inject the target fluid into the gap between the target core and the heat shrink tubing from the unblocked end of the heat shrink tubing until the target fluid fills the annular gap of the heat shrink tubing and the liquid level of the target fluid is below the end port; Step 4: placing the heat shrink tubing containing the target core after the treatment in step 3 in a CT scanning device for scanning, and obtaining a three-dimensional data volume after scanning; Step 5: Analyze the obtained three-dimensional data volume, identify the target fluid area according to the annular gap, and divide the gray value range of the target fluid area; Step 6: Obtain the three-dimensional data volume of the target core, substitute the grayscale value range of the target fluid area into the three-dimensional data volume, and the corresponding area with the grayscale value range in the target core is the position occupied by the target fluid in the pores of the target core, thereby completing the identification of the fluid in the core.

2. The experimental method for fluid identification in rock cores using CT scanning according to claim 1, characterized in that: The preparation method of the heat shrinkable sleeve is as follows: Step S1: preparing a heat shrinkable tube forming mold, the forming mold comprising an end mold and a middle mold; wherein the end mold comprises a base and a convex column integrally formed on the base, the convex column is provided with an annular boss for forming an annular gap in the heat shrinkable tube, and the middle mold is a cylindrical structure of the same size as the convex column; Step S2: placing the middle mold on the convex column of the end mold and wrapping it with a transparent heat shrink sleeve; Step S3: using hot air equipment to blow the heat shrink sleeve to shrink the heat shrink sleeve and wrap the molding mold tightly; Step S4: Pull the heat shrink sleeve out of the molding die to obtain a heat shrink sleeve including an annular gap.

3. The experimental method for fluid identification in rock cores using CT scanning according to claim 2, characterized in that: The end mold is made of stainless steel, and the middle mold is made of a core sample.

4. The experimental method for fluid identification in rock cores using CT scanning according to claim 3, characterized in that: The end of the heat shrinkable sleeve is sealed by a middle mold.

5. The experimental method for fluid identification in rock cores using CT scanning according to claim 4, characterized in that: The hot air equipment is a hot air blower, wherein when the hot air blower blows the heat shrink sleeve corresponding to the end mold, the blowing time is less than 1 minute; when the hot air blower blows the heat shrink sleeve corresponding to the middle mold, the blowing time is greater than 3 minutes.

6. The experimental method for fluid identification in rock cores using CT scanning according to claim 1, characterized in that: The target fluid includes formation water, crude oil and drilling mud.

7. The experimental method for fluid identification in rock cores using CT scanning according to claim 1, characterized in that: The annular gap is an annular structure or a square structure.

8. The experimental method for fluid identification in rock cores using CT scanning according to claim 1, characterized in that: The raised height of the annular gap is 2-4 mm, and the raised width is 3-6 mm.

9. The experimental method for fluid identification in rock cores using CT scanning according to claim 1, characterized in that: When the target fluid is filled into the gap between the target core and the heat shrinkable tube, the distance between the liquid surface of the target fluid and the port of the heat shrinkable tube is greater than 3 cm.

10. An experimental method for fluid identification in rock cores using CT scanning according to any one of claims 1 to 9, characterized in that: The parameters of the CT scanning device during scanning are: Scanning sample size restrictions: diameter less than 260mm, height less than 420mm, weight less than 20kg; X-ray source resolution: minimum focus size ≤ 3μm, detail resolution ≤ 2μm; Number of photos: 2000, exposure time: 500ms, voltage: 150KV, current: 130mA.

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