A porosity testing method for special-shaped shale based on 3D printing technology

Abstract

The invention discloses a method for testing the porosity of shaped shale based on 3D printing technology, comprising obtaining a three-dimensional model of a target shaped shale sample and a three-dimensional model of a sample chamber in a helium porosimeter for placing the target shaped shale sample; comparing and combining the three-dimensional model of the shaped shale sample and the three-dimensional model of the sample chamber, picking up characteristic surfaces of the three-dimensional model of the shaped shale sample, and obtaining a three-dimensional model of a residual void volume; obtaining a non-porous solid part of the three-dimensional model of the residual void volume according to specific parameters of the three-dimensional model of the residual void volume by 3D printing; combining the shaped shale sample and the solid part of the three-dimensional model of the residual void volume and placing them in the sample chamber of the helium porosimeter, and measuring the skeleton volume of the shaped shale sample; and calculating the porosity of the shaped shale sample according to the apparent volume of the shaped shale sample, the specific parameters of the three-dimensional model of the residual void volume, and the skeleton volume of the shaped shale sample.

Description

Technical Field

[0001] The present invention relates to the field of geological survey technology, and in particular to a porosity testing method for special-shaped shale based on 3D printing technology. Background Art

[0002] Porosity is an important technical parameter for shale gas reservoir evaluation. There are many methods for testing shale porosity, mainly including gas testing, liquid testing and nuclear magnetic resonance. Among them, the gas testing method mainly determines the shale skeleton volume by recording the pressure before and after equilibrium after the gas expands into the pores of the sample, and then calculates the porosity. The gas testing method has become a widely used porosity testing method in the exploration field because the test process does not require the destruction of the internal structure of the sample and the test results are highly accurate under ideal test conditions.

[0003] The current gas testing method for shale porosity requires drilling cylindrical rock samples according to the size of the sample chamber, ensuring that the two end faces of the cylinder are parallel and perpendicular to its axis (GB / T 29172-2012) so that the cylindrical rock sample is tightly combined with the core holder. The gas testing method has the following main problems in actual operation:

[0004] First, the gas testing method can only test cylindrical samples, and cannot test irregular shaped samples;

[0005] Second, due to the well-developed stratification, brittleness and fragility of shale, it is difficult to prepare cylindrical rock samples. After the rock sample is placed in the sample chamber, the empty volume is difficult to eliminate. After the empty volume is filled with helium, the influence of ambient temperature and pressure will seriously affect the test accuracy.

[0006] Third, during the multi-method combined testing process, it is difficult for cylindrical shale samples to remain intact for a long time, and once they break, the porosity cannot be tested any further.

[0007] Therefore, how to eliminate the influence of the empty volume of the sample chamber on the porosity test results to the greatest extent possible and establish a porosity test method for irregular shale that is not limited to cylindrical shapes has become a technical problem that urgently needs to be solved in the existing technology. Summary of the invention

[0008] The purpose of the present invention is to provide a method for testing the porosity of irregular shale based on 3D printing technology, so as to solve the technical problems in the prior art that the irregular shale has a large sample chamber empty volume in the existing gas testing method, the helium is greatly affected by the ambient temperature and pressure, and the integrity cannot be guaranteed during the multi-method combined testing process, resulting in the inability to test and poor measurement accuracy.

[0009] In order to solve the above technical problems, the present invention specifically provides the following technical solutions:

[0010] A method for testing the porosity of irregular shale based on 3D printing technology, comprising the following steps:

[0011] Step 100, obtaining a three-dimensional model of a target irregular shale sample and a three-dimensional model of a sample chamber in a helium porosity tester for placing the target irregular shale sample;

[0012] Step 200, by comparing and combining the three-dimensional model of the irregular shale sample and the three-dimensional model of the sample chamber, picking up the characteristic surface of the three-dimensional model of the irregular shale sample, and obtaining the three-dimensional model of the remaining empty volume after the sample chamber is loaded with the irregular shale sample through difference Boolean operation;

[0013] Step 300: According to the specific parameters of the remaining empty volume three-dimensional model, a non-porous solid part of the remaining empty volume three-dimensional model is obtained by 3D printing;

[0014] Step 400: Place the irregular shale sample and the solid part of the remaining empty volume three-dimensional model into the sample chamber of the helium porosity tester to measure the skeleton volume of the irregular shale sample;

[0015] Step 500: Calculate the porosity of the shaped shale sample by using the apparent volume of the shaped shale sample, the specific parameters of the remaining empty volume three-dimensional model, and the skeleton volume of the shaped shale sample. , and its calculation formula includes:

[0016] ;

[0017] in, represents the apparent volume of the shaped shale sample; Represents the skeleton volume of the heteromorphic shale sample.

[0018] As a preferred solution of the present invention, the specific method for measuring the skeleton volume of the irregular shale sample in step 400 includes:

[0019] The shaped shale sample and the solid part are combined and placed in the sample chamber of the helium porosity tester, and the reference chamber of the helium porosity tester is filled with helium of a predetermined pressure;

[0020] Opening the valve between the reference chamber and the sample chamber to allow helium to diffuse into the sample chamber and the pores of the irregular shale sample until a balanced pressure is reached;

[0021] Based on the equilibrium pressure, the skeleton volume of the irregular shale sample is calculated using Boyle's law.

[0022] As a preferred solution of the present invention, based on the equilibrium pressure, the specific formula for calculating the skeleton volume of the irregular shale sample using Boyle's law includes:

[0023] ;

[0024] ;

[0025] in, is the skeleton volume, ; is the volume of the sample chamber, ; is the volume of the reference chamber, ; is the module volume, ; is the pressure of the reference chamber before the valve is opened, MPa; p2 is the equilibrium pressure, MPa; for The compressibility factor of a gas under pressure conditions; for The compressibility factor of a gas under pressure conditions.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The 3D printing-based porosity testing method for irregular shale provided by the present invention solves the problem that the empty volume of the sample chamber after the rock sample is loaded affects the test accuracy; and solves the problem that the existing testing equipment cannot accurately test the porosity of irregular shaped shale samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0029] Figure 1 It is a schematic diagram of the process of the porosity testing method of special-shaped shale based on 3D printing technology according to an embodiment of the present invention;

[0030] Figure 2 This is a comparison chart of the test results of the porosity of irregular shale in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] like Figure 1 As shown, the present invention provides a method for testing the porosity of special-shaped shale based on 3D printing technology, comprising the steps of:

[0033] Step 100, obtaining a three-dimensional model of a target irregular shale sample and a three-dimensional model of a sample chamber in a helium porosity tester in which the target irregular shale sample is placed;

[0034] Step 200, by comparing and combining the three-dimensional model of the irregular shale sample and the three-dimensional model of the sample chamber, picking up the characteristic surface of the three-dimensional model of the irregular shale sample, and obtaining the three-dimensional model of the remaining empty volume after the sample chamber is loaded with the irregular shale sample through difference Boolean operation;

[0035] Step 300: According to the specific parameters of the remaining empty volume three-dimensional model, a non-porous solid part of the remaining empty volume three-dimensional model is obtained by 3D printing;

[0036] Step 400: Place the irregular shale sample and the solid part of the remaining empty volume three-dimensional model into the sample chamber of the helium porosity tester to measure the skeleton volume of the irregular shale sample;

[0037] Step 500: Calculate the porosity of the shaped shale sample by using the apparent volume of the shaped shale sample, the specific parameters of the remaining empty volume three-dimensional model, and the skeleton volume of the shaped shale sample. , and its calculation formula includes:

[0038] ;

[0039] in, represents the apparent volume of the shaped shale sample; Represents the skeleton volume of the heteromorphic shale sample.

[0040] Boolean operation of three-dimensional models is a relatively common technology, which is mainly divided into union, intersection and subtraction. Subtraction calculation is applied in the present invention.

[0041] The specific method for measuring the skeleton volume of the irregular shale sample in step 400 includes:

[0042] The shaped shale sample and the solid part are combined and placed in the sample chamber of the helium porosity tester, and the reference chamber of the helium porosity tester is filled with helium of a predetermined pressure;

[0043] Opening the valve between the reference chamber and the sample chamber to allow helium to diffuse into the sample chamber and the pores of the irregular shale sample until a balanced pressure is reached;

[0044] Based on the equilibrium pressure, the skeleton volume of the irregular shale sample is calculated using Boyle's law.

[0045] Based on the equilibrium pressure, the specific formula for calculating the skeleton volume of the irregular shale sample using Boyle's law includes:

[0046] ;

[0047] ;

[0048] in, is the skeleton volume, ; is the volume of the sample chamber, ; is the volume of the reference chamber, ; is the module volume, ; is the pressure of the reference chamber before the valve is opened, MPa; p2 is the equilibrium pressure, MPa; for The compressibility factor of a gas under pressure conditions; for The compressibility factor of a gas under pressure conditions.

[0049] It is further explained that due to the accuracy and error of scanners and 3D printers, tiny gaps will be generated in actual operations. However, even in the test of ideal cylindrical samples, such gaps exist to facilitate the insertion and removal of samples.

[0050] Therefore, the gap is generally larger than the gap caused by the error in combining the solid part and the irregular shale through 3D scanning and printing in the present invention, so the impact of the volume of the gap caused by this in the production environment can be ignored.

[0051] In order to further verify the above technical effects, the following experimental data are provided:

[0052] Five irregular shale samples were taken and their porosity was repeatedly tested comparatively using the above method and the traditional method.

[0053] The test environment temperature is 24.0℃ in a constant temperature box, and the temperature changes by ±0.2℃ during repeated tests. The environmental pressure is affected by the weather and cannot be controlled.

[0054] The test results are shown in the table below. The comparison chart shows that the porosity of the shaped sample measured by this method under laboratory conditions is more accurate and stable. Repeated experimental comparisons show that the test results of this method have a smaller error than the traditional method. Figure 2 As shown:

[0055]

[0056] The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present application within the essence and protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present application.

Claims

1. A method for testing the porosity of special-shaped shale based on 3D printing technology, characterized in that: Includes steps: Step 100, obtaining a three-dimensional model of a target irregular shale sample and a three-dimensional model of a sample chamber in a helium porosity tester for placing the target irregular shale sample; Step 200, by comparing and combining the three-dimensional model of the irregular shale sample and the three-dimensional model of the sample chamber, picking up the characteristic surface of the three-dimensional model of the irregular shale sample, and obtaining the three-dimensional model of the remaining empty volume after the sample chamber is loaded with the irregular shale sample through difference Boolean operation; Step 300: According to the specific parameters of the remaining empty volume three-dimensional model, a non-porous solid part of the remaining empty volume three-dimensional model is obtained by 3D printing; Step 400: Place the irregular shale sample and the solid part of the remaining empty volume three-dimensional model into the sample chamber of the helium porosity tester to measure the skeleton volume of the irregular shale sample; Step 500: Calculate the porosity of the irregular shale sample by using the apparent volume of the irregular shale sample, the specific parameters of the remaining empty volume three-dimensional model and the skeleton volume of the irregular shale sample. The calculation formula includes: ； in, represents the apparent volume of the shaped shale sample; It represents the skeleton volume of the heteromorphic shale sample; The specific method for measuring the skeleton volume of the irregular shale sample in step 400 includes: The shaped shale sample and the solid part are combined and placed in the sample chamber of the helium porosity tester, and the reference chamber of the helium porosity tester is filled with helium of a predetermined pressure; Opening the valve between the reference chamber and the sample chamber to allow helium to diffuse into the sample chamber and the pores of the irregular shale sample until a balanced pressure is reached; Based on the equilibrium pressure, the skeleton volume of the irregular shale sample is calculated using Boyle's law.

2. According to claim 1, a method for testing the porosity of special-shaped shale based on 3D printing technology is characterized in that: Based on the equilibrium pressure, the specific formula for calculating the skeleton volume of the irregular shale sample using Boyle's law includes: ； ； in, is the skeleton volume, ; is the volume of the sample chamber, ; is the volume of the reference chamber, ; is the volume of the solid object, ; is the pressure of the reference chamber before the valve is opened, MPa; p2 is the equilibrium pressure, MPa; for The compressibility factor of a gas under pressure conditions; for The compressibility factor of a gas under pressure conditions.

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