Laminate shale bedded fracture porosity measurement method

Abstract

The present application provides a kind of laminated shale bedding seam porosity determination method, the laminated shale bedding seam porosity determination method includes: step 1, selects the laminated shale rock sample of a certain research block, carries out helium hole method porosity determination experiment, obtains the pore volume and porosity of the shale sample as a whole;Step 2, obtain the curve of porosity and permeability with net overburden pressure;Step 3, obtain pore compression coefficient and permeability sensitivity coefficient;Step 4, according to pore compression coefficient and permeability sensitivity coefficient, obtain the pore permeability power index;Step 5, obtain the maximum pore radius value and average pore radius value;Step 6, according to the calculation formula of pore permeability power index, calculate the laminated shale bedding seam porosity value.The laminated shale bedding seam porosity determination method has strong reliability and accuracy, provides effective technical support for laminated shale oilfield resource quantity evaluation and development scheme.

Description

Technical Field

[0001] The present invention relates to the technical field of shale oil exploration and development, and in particular to a method for measuring the porosity of laminar shale bedding fractures. Background Art

[0002] With advances in shale oil and gas exploration and development technology, shale oil is becoming increasingly important in the petroleum resource landscape. Laminated shale is a key component of shale. Within laminated shale reservoirs, argillaceous and limy laminae are abundantly developed, and the interlaminar fractures between laminae play a key role in the fluidity and reservoir properties of shale oil. Establishing a method for measuring the porosity of bedding fractures in laminated shale, and clarifying the pore volume of bedding fractures, will provide a more accurate assessment of the effective recovery of shale oil and better guide the elastic development of laminated shale.

[0003] Chinese patent application CN 111650108 A discloses a method and apparatus for measuring the effective porosity of shale rock, relating to the field of experimental testing for oil and gas exploration and development. The method comprises: obtaining the total volume of the shale rock being measured, the skeleton volume of the shale rock being measured, and the volume of particles and / or dust within the shale rock being measured; determining the volume of a moisture-absorbing medium; correcting the skeleton volume using the volume of the moisture-absorbing medium to obtain a skeleton-corrected volume; and determining the effective porosity of the shale rock being measured based on the total volume, the skeleton-corrected volume, and the volume of particles and / or dust. This method addresses the problem of inaccurate effective porosity measurements of shale rock.

[0004] Chinese patent application CN 108956941 A discloses a method for identifying shale bedding, comprising: determining the structure and texture of an outcrop of a target layer; obtaining a rock sample that vertically penetrates the target layer, and producing a plurality of longitudinally continuous first-size cores and a plurality of longitudinally continuous second-size cores from the rock sample; determining the structure and texture of each layer in the first-size cores, and determining the composition, structure, and texture of each lamina in the second-size cores; and combining the structure and texture of the outcrop of the target layer, the structure and texture of each layer in the first-size cores, and the composition, structure, and texture of each lamina in the second-size cores to obtain a bedding identification result for the target layer. This embodiment of the application can improve the accuracy of shale bedding identification.

[0005] Chinese patent application CN102252948A discloses a method for measuring the porosity of mudstone, which includes: selecting a whole mudstone sample to be tested, measuring the mass MO, measuring the total volume VO of the block, calculating the block density ρb of the mudstone, crushing the sample, and taking a certain amount M1, M1≤MO; distilling and extracting the sample until the water production remains stable, and recording the volume Vw of the extracted water; removing the distilled and extracted sample, drying it until the mass is stable, and recording the sample mass M2; removing the dried sample, measuring the particle volume Vg; and calculating the sample porosity Φ.

[0006] Currently, research on shale reservoir porosity is mainly based on traditional porosity determination methods such as fluid saturation method and helium porosimetry. These methods cannot distinguish the pore volume occupied by bedding fractures in laminated shales. At the same time, there are few systematic studies and mature methods for analyzing the porosity of bedding fractures in laminated shales.

[0007] The above existing technologies are all significantly different from the present invention and fail to solve the technical problem we want to solve. Therefore, we have invented a new method for measuring the porosity of laminar shale bedding fractures. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for measuring the porosity of bedding fractures in laminated shale, which can accurately measure the porosity of bedding fractures in laminated shale and has strong reliability and accuracy.

[0009] The object of the present invention can be achieved by the following technical measures: a method for measuring the porosity of laminar shale bedding fractures, the method comprising:

[0010] Step 1: Select a laminar shale sample from a certain study area and conduct a helium porosimetry porosity measurement experiment to obtain the overall pore volume and porosity of the shale sample;

[0011] Step 2, obtaining the curves of porosity and permeability changing with net overburden pressure;

[0012] Step 3, obtaining the pore compressibility coefficient and permeability sensitivity coefficient;

[0013] Step 4, obtaining the pore permeability power index according to the pore compressibility coefficient and the permeability sensitivity coefficient;

[0014] Step 5, obtaining the maximum pore radius value and the average pore radius value;

[0015] Step 6: Calculate the porosity value of the laminar shale bedding fractures according to the calculation formula of the porosity and permeability power index.

[0016] The purpose of the present invention can also be achieved by the following technical measures:

[0017] In step 1, a laminar shale sample from a certain research area is selected and the sample volume V is obtained by measurement. b , the volume V of the rock sample particles is obtained using the helium porosity method g , the pore volume V of the rock sample is obtained by subtracting the particle volume from the rock sample volume p ; Use a balance to weigh the rock sample mass m.

[0018] In step 1, the shale lithologic porosity Φ is calculated as:

[0019]

[0020] In step 2, an overburden pressure porosity and permeability test is conducted on the shale sample to obtain a curve of porosity and permeability changing with net overburden pressure;

[0021] In step 3, the porosity and permeability curves varying with the net overburden pressure are exponentially fitted to obtain the pore compressibility coefficients C and C of the laminated shale. φ and permeability sensitivity coefficient C k .

[0022] In step 4, the porosity and permeability power index α of the shale sample is calculated based on the pore compressibility coefficient and permeability sensitivity coefficient of the laminated shale:

[0023]

[0024] Where C φ is the pore compression coefficient; C k is the permeability sensitivity coefficient.

[0025] In step 5, a high-pressure mercury injection test is performed on the laminar shale sample to obtain the maximum pore radius R of the shale sample. max and the average pore radius R ave .

[0026] In step 6, according to the calculation formula of the porosity and permeability power index of laminated shale, matrix porosity + dense laminae porosity = sample porosity are combined to obtain the calculation formula of the porosity of dense laminae in laminated shale.

[0027] In step 6, the porosity of the tight laminae in the laminar shale is f The calculation formula is:

[0028]

[0029]

[0030] φ=φ p +φ f (5)

[0031]

[0032] Where R max is the maximum pore radius;

[0033] R ave is the average pore radius;

[0034] Φ is the porosity of shale core;

[0035] α is the porosity and permeability power index of the shale sample;

[0036] Φp is the porosity remaining after removing the dense laminae in shale.

[0037] The method for measuring the porosity of bedding fractures in laminated shale in the present invention divides the pore volume of the laminated shale sample into the matrix pore volume and the bedding fracture pore volume when measuring the porosity of the bedding fractures in laminated shale. Combined with the changes in the permeability and porosity of the shale sample with the net overburden pressure, and the high-pressure mercury injection experimental technology to obtain the average pore throat radius and the maximum pore throat radius, the porosity of the bedding fractures in laminated shale is accurately measured, overcoming the shortcomings of the existing technology.

[0038] The method of the present invention obtains the overall pore volume and porosity of the shale sample through a helium porosimetry experiment; obtains a curve showing the variation of porosity and permeability with net overburden pressure by performing an overburden pressure porosity and permeability experiment on the shale sample; performs exponential fitting on the porosity and permeability variation curves to obtain a pore compression coefficient and a permeability sensitivity coefficient; obtains a porosity and permeability power index based on the pore compression coefficient and the permeability sensitivity coefficient; performs a high-pressure mercury injection experiment on the shale sample to obtain a maximum pore radius value and an average pore radius value; and calculates the porosity value of the laminar shale bedding fractures based on a calculation formula for the porosity and permeability power index.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] When calculating the porosity of dense laminae in laminated shale, this method divides the pore volume of the laminated shale sample into the matrix pore volume and the bedding fracture pore volume. Combined with the changes in the permeability and porosity of the shale sample with the net overburden pressure, and the average pore throat radius and maximum pore throat radius obtained by high-pressure mercury injection experimental technology, the bedding fracture porosity in the laminated shale is accurately measured with high reliability and accuracy. The method of the present invention provides effective technical support for the resource evaluation of laminated shale oil fields and the formulation of development plans. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a flow chart of a specific embodiment of the method for measuring the porosity of laminar shale bedding fractures of the present invention;

[0042] Figure 2This is a graph showing changes in shale porosity with net overburden pressure in a specific embodiment of the present invention;

[0043] Figure 3 This is a graph showing the change of shale permeability with net overburden pressure in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0044] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0045] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations and / or combinations thereof.

[0046] The method for measuring the porosity of laminar shale bedding fractures of the present invention comprises the following steps:

[0047] Step 1: Select a laminar shale sample from a certain study area and conduct a helium porosimetry porosity measurement experiment to obtain the overall pore volume and porosity of the shale sample;

[0048] Select a laminar shale sample from a certain research area and use the measurement method to obtain the sample volume V b , the volume V of the rock sample particles is obtained using the helium porosity method g , the pore volume V of the rock sample is obtained by subtracting the particle volume from the rock sample volume p ; Use a balance to weigh the rock sample mass m, and the shale lithologic porosity calculation formula is:

[0049]

[0050] Step 2: Conduct an overburden pressure porosity and permeability test on the shale sample to obtain a curve showing changes in porosity and permeability with net overburden pressure;

[0051] Step 3: Perform exponential fitting on the porosity and permeability change curves to obtain the pore compression coefficient and permeability sensitivity coefficient;

[0052] The porosity and permeability curves varying with the net overburden pressure were exponentially fitted to obtain the pore compression coefficients C and C of the laminated shale. φ and permeability sensitivity coefficient C k .

[0053] Step 4, obtaining the pore permeability power index according to the pore compressibility coefficient and the permeability sensitivity coefficient;

[0054] According to the pore compressibility coefficient and permeability sensitivity coefficient of the laminated shale, the porosity and permeability power index α of the shale sample is calculated:

[0055]

[0056] Step 5: Perform a high-pressure mercury injection test on the shale sample to obtain a maximum pore radius value and an average pore radius value;

[0057] The high-pressure mercury injection experiment was conducted on the laminar shale sample to obtain the maximum pore radius R of the shale sample. max and the average pore radius R ave .

[0058] Step 6: Calculate the porosity value of the laminar shale bedding fractures according to the calculation formula of the porosity and permeability power index.

[0059] According to the calculation formula of the porosity and permeability power index of laminated shale, the matrix porosity + dense laminae porosity = sample porosity are combined to obtain the calculation formula of the porosity of dense laminae in laminated shale.

[0060]

[0061]

[0062] φ=φ p +φ f (5)

[0063]

[0064] Formula (6) is the calculation formula for the porosity of bedding fractures in laminated shale.

[0065] The following are several specific embodiments of the present invention.

[0066] Example 1

[0067] like Figure 1 As shown, the method for determining the porosity of dense laminae in laminar shale comprises the following steps:

[0068] Step 101: Obtain the rock sample volume V using a measurement method. b , the rock sample particle volume V is obtained using the helium porosity method g , the pore volume V of the rock sample is obtained by subtracting the particle volume from the rock sample volume p ; Use a balance to weigh the rock sample mass m, and the porosity calculation formula of shale rock sample is:

[0069]

[0070] The porosity value of the sample in this example is 5.84.

[0071] Step 201: Perform an overburden pressure porosity and permeability test on the shale sample to obtain a curve showing the variation of porosity and permeability of the shale sample with the net overburden pressure, such as Figure 2 and Figure 3 .

[0072] Step 301: perform exponential fitting on the curves of porosity and permeability changing with net overburden pressure, such as Figure 2 and Figure 3 The pore compression coefficient C of the laminated shale is obtained respectively φ and permeability sensitivity coefficient C k , in this example C φ =0.0199, C k =0.185.

[0073] Step 401: Calculate the porosity and permeability power index α of the shale sample based on the pore compressibility coefficient and permeability sensitivity coefficient of the laminated shale:

[0074]

[0075] The porosity and permeability index of the shale sample was calculated to be 9.25.

[0076] Step 501: Perform a high-pressure mercury injection test on the laminar shale sample to obtain the maximum pore radius R of the shale sample. max =11.229 μm and average pore radius R ave =0.686μm.

[0077] Step 601 : According to the porosity and permeability power index calculation formula of laminated shale, matrix porosity + bedding fracture porosity = sample porosity are combined to obtain a calculation formula for bedding fracture porosity in laminated shale.

[0078]

[0079]

[0080] φ=φ p +φ f (5)

[0081]

[0082] Formula (6) is the calculation formula for the porosity of bedding fractures in laminated shale. The calculated porosity of bedding fractures in laminated shale is 1.87.

[0083] In this embodiment, the total porosity of a certain laminar shale sample is 5.84, the bedding fracture porosity is 1.87, and the pore volume of the bedding fractures accounts for 32% of the total pore volume of the shale.

[0084] Example 2

[0085] like Figure 1 As shown, the method for determining the porosity of dense laminae in laminar shale comprises the following steps:

[0086] Step 101: Obtain the rock sample volume V using a measurement method. b , the volume V of the rock sample particles is obtained using the helium porosity method g , the pore volume V of the rock sample is obtained by subtracting the particle volume from the rock sample volume p ; Use a balance to weigh the rock sample mass m, and the porosity calculation formula of shale rock sample is:

[0087]

[0088] The porosity value of the sample in this example is 4.28.

[0089] Step 201: Perform an overburden pressure porosity and permeability test on the shale sample to obtain a curve showing the variation of porosity and permeability of the shale sample with the net overburden pressure, such as Figure 2 and Figure 3 .

[0090] Step 301: perform exponential fitting on the curves of porosity and permeability changing with net overburden pressure, such as Figure 2 and Figure 3 The pore compression coefficient C of the laminated shale is obtained respectively φ and permeability sensitivity coefficient C k , in this example C φ =0.0104, C k =0.102.

[0091] Step 401: Calculate the porosity and permeability power index α of the shale sample based on the pore compressibility coefficient and permeability sensitivity coefficient of the laminated shale:

[0092]

[0093] The porosity and permeability index of the shale sample was calculated to be 18.86.

[0094] Step 501: Perform a high-pressure mercury injection test on the laminar shale sample to obtain the maximum pore radius R of the shale sample. max =4.752 and average pore radius R ave =0.252.

[0095] Step 601, according to the porosity and permeability power index calculation formula of the laminated shale, the calculation formula of the laminated shale joint porosity is obtained by combining the matrix porosity + joint porosity = sample porosity.

[0096]

[0097]

[0098] φ = φ p + φ f (5)

[0099]

[0100] The formula (6) is the calculation formula of the laminated shale joint porosity, and the laminated shale joint porosity is 1.25 obtained by calculation.

[0101] The total porosity of a certain laminated shale sample in this example is 4.28, the joint porosity is 1.25, and the joint porosity volume accounts for 29% of the total porosity volume of the shale.

[0102] Example 3

[0103] As shown in Figure 1 , the laminated shale tight laminated porosity determination method comprises the following steps:

[0104] Step 101, the volume V b of the rock sample is obtained by using the measuring method, the particle volume V g of the rock sample is obtained by using the helium hole method, and the pore volume V p of the rock sample is obtained by subtracting the particle volume from the rock sample volume; the mass m of the rock sample is weighed by using the balance, and the shale rock sample porosity calculation formula is:

[0105]

[0106] The sample porosity value in this example is 3.11.

[0107] Step 201, the pore and permeability experiment of the shale sample under the overburden pressure is carried out, and the change curves of the shale sample porosity and permeability with the net overburden pressure are obtained, as shown in Figure 2 and Figure 3 .

[0108] Step 301, the change curves of the porosity and permeability with the net overburden pressure are fitted by the exponential function, as shown in Figure 2 and Figure 3 respectively, the porosity compression coefficient C φ and the permeability sensitivity coefficient C k of the laminated shale are obtained, and in this example, C φ = 0.0042, C k=0.054.

[0109] Step 401: Calculate the porosity and permeability power index α of the shale sample based on the pore compressibility coefficient and permeability sensitivity coefficient of the laminated shale:

[0110]

[0111] The porosity and permeability index of the shale sample was calculated to be 14.41.

[0112] Step 501: Perform a high-pressure mercury injection test on the laminar shale sample to obtain the maximum pore radius R of the shale sample. max =1.254 and average pore radius R ave =0.087.

[0113] Step 601 : According to the porosity and permeability power index calculation formula of laminated shale, matrix porosity + bedding fracture porosity = sample porosity are combined to obtain a calculation formula for bedding fracture porosity in laminated shale.

[0114]

[0115]

[0116] φ=φ p +φ f (5)

[0117]

[0118] Formula (6) is the calculation formula for the porosity of bedding fractures in laminated shale. The calculated porosity of bedding fractures in laminated shale is 0.71.

[0119] In this embodiment, the total porosity of a certain laminar shale sample is 4.28, the bedding fracture porosity is 1.25, and the bedding fracture pore volume accounts for 23% of the total pore volume of the shale.

[0120] The method comprises the following steps: selecting a lamellar shale sample of a certain research block, performing a helium pore experiment to obtain the pore volume and porosity of the whole shale sample; then performing a confining pressure porosity-permeability experiment on the sample to obtain the variation curve of the porosity and permeability of the shale sample with the net overburden pressure; performing exponential fitting on the variation curve of the porosity and permeability to obtain the pore compression coefficient and permeability sensitivity coefficient respectively, and the pore-permeability power index of the shale sample; performing a high-pressure mercury injection experiment on the shale sample to obtain the maximum pore radius value and average pore radius value of the shale sample; and calculating the bedding seam porosity value in the lamellar shale according to the pore-permeability power index calculation formula. The method accurately describes the bedding seam porosity in the lamellar shale, has strong reliability and accuracy, and provides effective technical support for the elastic development of lamellar shale oilfields and the formulation of development plans.

[0121] Finally, it should be noted that: the above only for the preferred embodiments of the present application, and not for limiting the present application, although the foregoing detailed description of the present application is made with reference to the foregoing embodiments, for those skilled in the art, it still can be modified, or part of the technical features of the equivalent replacement. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0122] In addition to the technical features described in the specification, they are known to those skilled in the art.

Claims

1. A method for determining the porosity of laminar shale bedding fractures, characterized in that: The laminar shale bedding fracture porosity determination method includes: Step 1: Select a laminar shale sample from a certain study area and conduct a helium porosimetry porosity measurement experiment to obtain the overall pore volume and porosity of the shale sample; Step 2, obtaining the curves of porosity and permeability changing with net overburden pressure; Step 3, obtaining the pore compressibility coefficient and permeability sensitivity coefficient; Step 4, obtaining the pore permeability power index according to the pore compressibility coefficient and the permeability sensitivity coefficient; Step 5, obtaining the maximum pore radius value and the average pore radius value; Step 6, calculating the porosity value of the laminar shale bedding fractures according to the calculation formula of the porosity and permeability power index; In step 6, according to the calculation formula of the porosity and permeability power index of laminated shale, the matrix porosity + dense laminae porosity = sample porosity are combined to obtain the calculation formula of the porosity of the dense laminae in laminated shale; the porosity of the dense laminae in laminated shale Φ f The calculation formula is: Where R max is the maximum pore radius; R ave is the average pore radius; Φ is the porosity of shale core; α is the porosity and permeability power index of the shale sample; Φp is the porosity remaining after removing the dense laminae in shale.

2. The method for measuring the porosity of laminar shale bedding fractures according to claim 1, characterized in that: In step 1, a laminar shale sample from a certain research area is selected and the sample volume V is obtained by measurement. b , the volume V of the rock sample particles is obtained using the helium porosity method g , the pore volume V of the rock sample is obtained by subtracting the particle volume from the rock sample volume p ; Use a balance to weigh the rock sample mass m.

3. The method for measuring the porosity of laminar shale bedding fractures according to claim 2, characterized in that: In step 1, the shale lithologic porosity Φ is calculated as:

4. The method for measuring the porosity of laminar shale bedding fractures according to claim 1, characterized in that: In step 2, an overburden pressure porosity and permeability test is conducted on the shale sample to obtain a curve of porosity and permeability changing with net overburden pressure.

5. The method for measuring the porosity of laminar shale bedding fractures according to claim 1, characterized in that: In step 3, the porosity and permeability curves varying with the net overburden pressure are exponentially fitted to obtain the pore compressibility coefficients C and C of the laminated shale. φ and permeability sensitivity coefficient C k .

6. The method for measuring the porosity of laminar shale bedding fractures according to claim 1, characterized in that: In step 4, the porosity and permeability power index α of the shale sample is calculated based on the pore compressibility coefficient and permeability sensitivity coefficient of the laminated shale: Where C φ is the pore compression coefficient; C k is the permeability sensitivity coefficient.

7. The method for measuring the porosity of laminar shale bedding fractures according to claim 1, characterized in that: In step 5, a high-pressure mercury injection test is performed on the laminar shale sample to obtain the maximum pore radius R of the shale sample. max and the average pore radius R ave .

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