Capillary pressure curve construction method based on microresistivity imaging logging and medium

Abstract

The present invention discloses a method and medium for constructing a capillary pressure curve based on microresistivity imaging logging. The construction method comprises the following steps: obtaining the electrical conductivity, fluid resistivity and pore throat length measured by each electrode plate; calculating the capillary pressure value of the electrode plate according to the electrical conductivity, fluid resistivity and pore throat length measured by the corresponding electrode plate; and constructing a corresponding capillary pressure curve according to the capillary pressure values of multiple electrode plates. The specific steps are as follows: based on a capillary model, arbitrarily intercepting a rock with a pore structure to obtain the intercepted side length of the intercepted rock and the fluid resistance in the pore structure; calculating the electrical conductivity measured by the electrode plate according to the intercepted side length of the intercepted rock and the fluid resistance in the pore structure; obtaining the pore throat length according to the intercepted side length of the intercepted rock and the pore throat tortuosity of the intercepted rock; calculating the pore throat radius according to the electrical conductivity, fluid resistivity and pore throat length measured by the electrode plate; and calculating the capillary pressure value of the electrode plate according to the pore throat radius.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum exploration, and in particular to a method for constructing a capillary pressure curve based on micro-resistivity imaging logging. Background Art

[0002] In the petroleum industry, capillary pressure is the most direct parameter reflecting the pore structure of rocks.

[0003] Currently, capillary pressure curves are commonly obtained using core experiments and microresistivity imaging logging. However, capillary pressure curves obtained based on core experiments are difficult to continuously characterize reservoirs. Capillary pressure curves established based on microresistivity imaging logging require a large number of core capillary pressure test calibrations, which is a complex and tedious process and costly. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a more streamlined method for constructing a capillary pressure curve. The purpose is to provide a method and medium for constructing a capillary pressure curve based on microresistivity imaging logging, which solves the problem that the capillary pressure curve established by microresistivity imaging logging requires a large number of core capillary pressure experimental scales.

[0005] The present invention is achieved through the following technical solutions:

[0006] A first aspect provides a method for constructing a capillary pressure curve based on microresistivity imaging logging, comprising the following steps:

[0007] Obtain the conductivity, fluid resistivity and pore throat length measured by each plate;

[0008] Calculating the capillary pressure value of the electrode plate according to the conductivity, fluid resistivity and pore throat length measured corresponding to the electrode plate;

[0009] According to the capillary pressure values of the plurality of electrode plates, a corresponding capillary pressure curve is constructed.

[0010] The capillary pressure values are calculated based on the conductivity, fluid resistivity, and pore throat length measured by the electrode plates. This eliminates the need for core capillary pressure experiments to obtain the capillary pressure values. This streamlines the capillary pressure curve construction method, simplifies the construction process, and reduces costs.

[0011] Furthermore, the method for obtaining the conductivity measured by the plate includes the following steps:

[0012] Based on the capillary model, a rock with a pore structure is randomly cut to obtain the cut side length of the cut rock and the fluid resistance in the pore structure;

[0013] The electrical conductivity measured by the electrode plate is calculated based on the intercepted side length of the intercepted rock and the fluid resistance in the pore structure.

[0014] After the capillary model is determined, the window length of the rock is uniquely determined, and the rock is divided into multiple sections of intercepted rock. The intercepted side length of the intercepted rock and the fluid resistance within the pore structure of the intercepted rock are collected through the electrode plates corresponding to the intercepted rock, and the conductivity of the intercepted rock, i.e., the conductivity measured by the above-mentioned electrode plates, is calculated. The intercepted rocks are continuous, and each section of the intercepted rock has a corresponding electrode plate for measuring the conductivity of the intercepted rock. Using the conductivity of microresistivity imaging logging, the corresponding capillary pressure curve constructed from the capillary pressure values of multiple electrode plates is made continuous.

[0015] Furthermore, the formula for calculating the conductivity measured by the above plate is as follows:

[0016]

[0017] Among them, C i represents the conductivity measured by the ith plate, R represents the fluid resistance of the pore structure, and L h Indicates the length of the intercepted side of the rock.

[0018] Using the above formula, the intercepted side length of the intercepted rock and the fluid resistance in the pore structure of the intercepted rock are collected through the electrode plate corresponding to the intercepted rock, and the conductivity of the intercepted rock is calculated. The conductivity of the microresistivity imaging logging is used to solve the discontinuity problem of the capillary pressure curve.

[0019] Furthermore, the pore throat length is obtained according to the intercepted side length of the intercepted rock and the pore throat tortuosity of the intercepted rock.

[0020] Calculating the capillary pressure value of the intercepted rock using the pore throat length is more accurate than directly calculating the capillary pressure value of the intercepted rock using the intercept length of the intercepted rock, thereby improving the accuracy of the calculation.

[0021] Furthermore, the calculation formula for the pore throat length is as follows:

[0022] L=L h T,

[0023] Where L represents the pore throat length and T represents the pore throat tortuosity.

[0024] Furthermore, the specific steps for calculating the capillary pressure value of the plate are as follows:

[0025] Calculate the pore throat radius based on the conductivity, fluid resistivity and pore throat length measured by the above-mentioned electrode plates;

[0026] According to the pore throat radius, the capillary pressure value of the electrode plate is calculated.

[0027] The average pore throat radius of the intercepted rock is calculated based on the corresponding electrical conductivity of the intercepted rock, the fluid resistance in the pore structure, and the pore throat length, so that the corresponding capillary pressure curve constructed by the capillary pressure values of multiple plates is continuous.

[0028] Furthermore, the formula for calculating the pore throat radius is as follows:

[0029]

[0030] Where r represents the pore throat radius, R mf Represents the fluid resistivity.

[0031] The above formula utilizes the electrical conductivity corresponding to the intercepted rock, the fluid resistance of the pore structure of the intercepted rock, the intercepted side length of the intercepted rock, and the pore throat length of the intercepted rock. The calculation is simple and the construction process of the capillary pressure curve is simplified.

[0032] Furthermore, based on the pore throat radius, the formula for calculating the capillary pressure value of the electrode plate is as follows:

[0033]

[0034] Among them, P ci represents the capillary pressure value of the i-th plate, and σ represents the fluid interfacial tension; represents the wetting contact angle.

[0035] Furthermore, the electrode plates are used to measure the electrical conductivity of the cut rock. The rock with the porous structure is divided into multiple sections of cut rock, and the multiple electrode plates are used to measure the electrical conductivity of each section of cut rock.

[0036] A second aspect provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and the computer program enables a computer to execute the capillary pressure curve construction method.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] The present invention calculates the capillary pressure value corresponding to each electrode plate through the conductivity, fluid resistivity and pore throat length measured by the electrode plates, obtains the capillary pressure values calculated by all electrode plates used in the capillary model to measure conductivity, and obtains the corresponding capillary pressure curve. The present invention provides a capillary pressure curve construction method with simpler parameters, does not require core capillary pressure experiments, has wider applicability, and overcomes the limitation of the existing technology that capillary pressure curves established based on microresistivity imaging logging require a large number of core capillary pressure experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0040] Figure 1 A schematic diagram of the capillary model structure for cutting rock provided in Example 1;

[0041] Figure 2 Equivalent resistivity diagram of the rock capillary model provided for Example 2. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0043] Example 1

[0044] This embodiment 1 provides a method for constructing a capillary pressure curve based on microresistivity imaging logging, comprising the following steps:

[0045] Obtain the conductivity, fluid resistivity and pore throat length measured by each plate;

[0046] Calculating the capillary pressure value of the electrode plate according to the conductivity, fluid resistivity and pore throat length measured corresponding to the electrode plate;

[0047] According to the capillary pressure values of the plurality of electrode plates, a corresponding capillary pressure curve is constructed.

[0048] The capillary pressure value is calculated based on the conductivity, fluid resistivity and pore throat length measured by the electrode plate. The capillary pressure value is obtained without the need for core capillary pressure experiments. This simplifies the method for constructing a capillary pressure curve and eliminates the need for core capillary pressure experiments. It has wider applicability and overcomes the limitation of the existing technology that capillary pressure curves established based on microresistivity imaging logging require a large number of core capillary pressure experiments to obtain the capillary pressure curve. This simplifies the construction process and reduces costs.

[0049] In a specific embodiment, the method for obtaining the conductivity measured by the electrode plate includes the following steps:

[0050] Based on the capillary model, any rock with pore structure is cut, such as Figure 1 As shown, the intercepted side length of the intercepted rock and the fluid resistance in the pore structure are obtained;

[0051] The electrical conductivity measured by the electrode plate is calculated based on the intercepted side length of the intercepted rock and the fluid resistance in the pore structure.

[0052] After the capillary model is determined, the window length of the rock is uniquely determined, and the rock is divided into multiple sections of intercepted rock. The intercepted side length of the intercepted rock and the fluid resistance within the pore structure of the intercepted rock are collected through the electrode plates corresponding to the intercepted rock, and the conductivity of the intercepted rock, i.e., the conductivity measured by the above-mentioned electrode plates, is calculated. The intercepted rocks are continuous, and each section of the intercepted rock has a corresponding electrode plate for measuring the conductivity of the intercepted rock. Using the conductivity of microresistivity imaging logging, the corresponding capillary pressure curve constructed from the capillary pressure values of multiple electrode plates is made continuous.

[0053] In a specific embodiment, the formula for calculating the conductivity measured by the above-mentioned plate is as follows:

[0054]

[0055] Among them, C i represents the conductivity measured by the ith plate, R represents the fluid resistance of the pore structure, and L h Indicates the length of the intercepted side of the rock.

[0056] Using the above formula, the intercepted side length of the intercepted rock and the fluid resistance in the pore structure of the intercepted rock are collected through the electrode plate corresponding to the intercepted rock, and the conductivity of the intercepted rock is calculated. The conductivity of the microresistivity imaging logging is used to solve the discontinuity problem of the capillary pressure curve.

[0057] In a specific embodiment, the pore throat length is obtained according to the intercepted side length of the intercepted rock and the pore throat tortuosity of the intercepted rock.

[0058] Calculating the capillary pressure value of the intercepted rock using the pore throat length is more accurate than directly calculating the capillary pressure value of the intercepted rock using the intercept length of the intercepted rock, thereby improving the accuracy of the calculation.

[0059] In a specific embodiment, the calculation formula of the pore throat length is as follows:

[0060] L=L h T,

[0061] Where L represents the pore throat length and T represents the pore throat tortuosity.

[0062] In a specific embodiment, the specific steps for calculating the capillary pressure value of the electrode plate are as follows:

[0063] Calculate the pore throat radius based on the conductivity, fluid resistivity and pore throat length measured by the above-mentioned electrode plates;

[0064] According to the pore throat radius, the capillary pressure value of the electrode plate is calculated.

[0065] The average pore throat radius of the intercepted rock is calculated based on the corresponding electrical conductivity of the intercepted rock, the fluid resistance in the pore structure, and the pore throat length, so that the corresponding capillary pressure curve constructed by the capillary pressure values of multiple plates is continuous.

[0066] In a specific embodiment, the formula for calculating the pore throat radius is as follows:

[0067]

[0068] Where r represents the pore throat radius, R mf Represents the fluid resistivity.

[0069] The above formula utilizes the electrical conductivity corresponding to the intercepted rock, the fluid resistance of the pore structure of the intercepted rock, the intercepted side length of the intercepted rock, and the pore throat length of the intercepted rock. The calculation is simple and the construction process of the capillary pressure curve is simplified.

[0070] In a specific embodiment, based on the pore throat radius, the formula for calculating the capillary pressure value of the electrode plate is as follows:

[0071]

[0072] Among them, P ci represents the capillary pressure value of the i-th plate, σ represents the fluid interfacial tension, represents the wetting contact angle.

[0073] In a specific embodiment, the electrode plates are used to measure the electrical conductivity of the cut rock. The rock with the porous structure is divided into multiple sections of cut rock, and the multiple electrode plates are used to measure the electrical conductivity of each section of the cut rock.

[0074] Example 2

[0075] Based on the capillary model, the parameters of the rock skeleton and pore throat are input into the capillary model to construct a rock capillary model. The rock capillary model is divided into multiple intercepted rocks. The i-th electrode measures the conductivity of the i-th intercepted rock. The fluid in the pore throat of the rock flushing zone is mud filtrate, which does not contain residual oil and gas. The rock skeleton is non-conductive and there is no mud-added conductivity.

[0076] According to the rock capillary model and Ohm's law, the resistance of the mud filtrate in the rock pore throat of the i-th section is calculated as follows:

[0077]

[0078] The above-mentioned resistivity of the mud filtrate is obtained by analyzing and processing the collected well site water analysis data.

[0079] The total rock resistance includes the mud filtrate resistance and the skeleton resistance in parallel. The conductivity measured by the i-th plate of microresistivity imaging logging is calculated based on the total rock resistance. The formula is as follows:

[0080]

[0081] According to formula (2), the pore throat radius can be obtained as follows:

[0082]

[0083] The pore throat radius is the average pore throat radius of the intercepted rock.

[0084] The capillary pressure value is calculated based on the relationship between the capillary pressure value and the pore throat radius.

[0085]

[0086]

[0087] Under unit volume, the intercepted side length L of the rock is h =1, we get

[0088]

[0089] Among them, P ci is the capillary pressure value of the ith plate of microresistivity imaging logging, in MPa; C i is the conductivity measured by the i-th plate of microresistivity imaging logging; σ is the fluid interfacial tension, in N / m; is the wetting contact angle, in degrees.

[0090] In the rock capillary pressure experiment, the injected fluid is mercury, 2σ The value is 0.735; T is the pore throat tortuosity, which can be obtained through core experiments or theoretical values. Where Φ is the porosity interpreted by conventional logging or microresistivity imaging logging, and m is the porosity index, which can be obtained through rock electrical experiments.

[0091] The rock capillary model determines the window length of microresistivity imaging logging, obtains the capillary pressure values calculated by all pads of microresistivity imaging logging within the window length, and outputs the corresponding capillary pressure curve.

[0092] The result image of the capillary pressure curve with depth continuity constructed based on micro-resistivity imaging logging data is as follows: Figure 2 As shown, Figure 2The figure includes the depth of the first track; the microresistivity log of the second track; the pore throat radius distribution of the third track; and the capillary pressure curve of the fourth track. The horizontal axis represents the cumulative capillary pressure frequency component, which corresponds to the mercury saturation in the core mercury injection experiment; the vertical axis represents the capillary pressure value calculated at each depth point, which corresponds to the capillary pressure value measured in the core experiment; the shape of the capillary pressure curve corresponds to the capillary pressure curve obtained in the core mercury injection experiment.

[0093] Compared with the existing technology, the capillary pressure curve obtained by the method provided by the present invention has higher resolution and is continuous, does not require core capillary pressure experiments, and has wider applicability.

[0094] Example 3

[0095] This embodiment 3 provides a computer-readable storage medium, which stores a computer program. The computer program enables a computer to execute the capillary pressure curve construction method.

[0096] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for constructing a capillary pressure curve based on microresistivity imaging logging, characterized in that: The following steps are involved: Use microresistivity imaging logging to collect data and process the collected data to obtain the conductivity, fluid resistivity and pore throat length measured by each plate; Calculating the capillary pressure value of the electrode plate according to the conductivity, fluid resistivity and pore throat length measured corresponding to the electrode plate; constructing a corresponding capillary pressure curve according to the capillary pressure values of the plurality of electrode plates; The method for obtaining the conductivity measured by the electrode plate comprises the following steps: based on a capillary model, arbitrarily cutting a rock with a pore structure to obtain a cut side length of the cut rock and a fluid resistance in the pore structure; and calculating the conductivity measured by the electrode plate based on the cut side length of the cut rock and the fluid resistance in the pore structure. The pore throat length is obtained according to the intercepted side length of the intercepted rock and the pore throat tortuosity of the intercepted rock; The specific steps of calculating the capillary pressure value of the electrode plate are as follows: calculating the pore throat radius based on the conductivity, fluid resistivity and pore throat length measured by the electrode plate; calculating the capillary pressure value of the electrode plate based on the pore throat radius; The electrode plates are used to measure the electrical conductivity of the intercepted rock. The rock with a porous structure is divided into multiple sections of intercepted rock, and multiple electrode plates are used to measure the electrical conductivity of each section of intercepted rock.

2. The method for constructing a capillary pressure curve based on microresistivity imaging logging according to claim 1, characterized in that: The formula for calculating the conductivity measured by the plate is as follows: ， in, represents the conductivity measured by the i-th plate, represents the fluid resistance of the pore structure, Indicates the length of the intercepted side of the rock.

3. The method for constructing a capillary pressure curve based on microresistivity imaging logging according to claim 1, characterized in that: The calculation formula of the pore throat length is as follows: ， in, represents the pore throat length, represents the pore throat tortuosity, Indicates the length of the intercepted side of the rock.

4. The method for constructing a capillary pressure curve based on microresistivity imaging logging according to claim 1, characterized in that: The formula for calculating the pore throat radius is as follows: ， in, represents the pore throat radius, represents the fluid resistivity, represents the conductivity measured by the i-th plate, represents the length of the intercepted side of the rock, Indicates the pore throat length.

5. The method for constructing a capillary pressure curve based on microresistivity imaging logging according to claim 4, characterized in that: According to the pore throat radius, the formula for calculating the capillary pressure value of the electrode plate is as follows: ， in, represents the capillary pressure value of the i-th plate, represents the fluid interfacial tension; represents the wetting contact angle.

6. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and the computer program enables a computer to execute the capillary pressure curve construction method according to any one of claims 1 to 5.

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