A method for predicting fracture conductivity based on a multi-particle size proppant pack

Abstract

The present application relates to a kind of fracture conductivity prediction method based on multi-particle size proppant accumulation body, comprising: step one, obtain the composition of multi-particle size proppant accumulation body, the composition includes proppant particle size composition and number;Step two, the equivalent particle size of multi-particle size proppant accumulation body is calculated;Step three, obtain the permeability of multi-particle size proppant accumulation body;Step four, fracture conductivity prediction is carried out.The method provided by the present application realizes the fracture conductivity prediction of multi-particle size proppant accumulation body, overcomes the technical problems of error in prior art using average method, and is more in line with actual result.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas field development, in particular to a fracture conductivity prediction method based on a multi-particle-size proppant pack. BACKGROUND

[0002] In the process of hydraulic fracturing, in order to keep the fracture open, sand-carrying fluid with proppants is continuously injected into the hydraulic fracture. In order to improve the fracture conductivity, the injected proppants may be of different sizes, forming a multi-particle-size proppant pack composed of proppants of various sizes. Since proppants of different sizes may affect the fracture conductivity, and in the process of predicting the fracture conductivity, permeability is a key parameter, the average particle size or the weighted average particle size is often used to replace the real particle size in the previous prediction, which has a certain error compared with the real result. Therefore, how to provide a more reasonable permeability calculation method to obtain a more realistic result is a technical problem to be solved in predicting the fracture conductivity. SUMMARY

[0003] The present application aims to provide a fracture conductivity prediction method based on a multi-particle-size proppant pack to solve the technical problem of error in predicting the proppant permeability by using the average method in the prior art.

[0004] To achieve the above-mentioned purpose, the present application provides the following solutions.

[0005] A fracture conductivity prediction method based on a multi-particle-size proppant pack, comprising the following steps:

[0006] Step 1: obtaining the composition of the multi-particle-size proppant pack, which includes the particle size composition and the number of proppants;

[0007] Step 2: calculating the equivalent particle size of the multi-particle-size proppant pack;

[0008] Step 3: obtaining the permeability of the multi-particle-size proppant pack;

[0009] Step 4: predicting the fracture conductivity.

[0010] Preferably, the step 2 of calculating the equivalent particle size of the multi-particle-size proppant pack comprises:

[0011]

[0012] wherein D mn is the equivalent particle size, i is the serial number, n is the number of the ith proppant, and D i is the particle size of the ith proppant.

[0013] Preferably, the method for obtaining the permeability of the multi-size proppant stack in step three is as follows:

[0014]

[0015] k is the permeability of the multi-size proppant stack. For porosity, C k This is a correction factor.

[0016] Preferably, the predicted fracture conductivity in step four is as follows:

[0017] D f =k*w f

[0018] In the formula, D f For fracture conductivity, w f The width of the seam.

[0019] Preferably, step five further includes: establishing a numerical model of the multi-size proppant stack and verifying it using the numerical model.

[0020] Based on the same inventive concept, this invention provides a crack conductivity prediction system based on multi-size proppant packs, comprising:

[0021] The module for acquiring the composition of proppant stacks with multiple particle sizes is used to acquire the composition of proppant stacks, including the particle size composition and number of proppant particles.

[0022] An equivalent particle size acquisition module is used to calculate the equivalent particle size of multi-size proppant packs.

[0023] A permeability determination module is used to obtain the permeability of multi-size proppant packs;

[0024] A flow conductivity prediction module is used to predict the flow conductivity of cracks.

[0025] Preferably, the equivalent particle size acquisition module uses the following formula to obtain the equivalent particle size:

[0026]

[0027] Among them, D mn Where i is the equivalent particle size, n is the number of the i-th type of proppant, and D is the equivalent particle size. i Let be the particle size of the i-th type of proppant.

[0028] Preferably, the method for obtaining the permeability in the permeability determination module is as follows:

[0029]

[0030] k is the permeability of the multi-size proppant stack. For porosity, C k This is a correction factor.

[0031] Preferably, the flow guidance capacity prediction method in the flow guidance capacity prediction module is as follows:

[0032] D f =k*w f

[0033] In the formula, D f For fracture conductivity, w f The width of the seam.

[0034] On the other hand, the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, when the processor executes the computer program, it implements the steps of the method for predicting the crack conductivity based on multi-size proppant packs as described above.

[0035] On the other hand, the present invention provides a computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements the steps of the method for predicting the crack conductivity based on multi-size proppant packs as described above.

[0036] According to specific embodiments provided by the present invention, the present invention has the following technical effects: the method provided by the present invention realizes the prediction of the crack conductivity of multi-size proppant packs, overcomes the technical problem of errors in the average method used in the prior art, and provides results that are more consistent with reality. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 A flowchart of a method for predicting the crack conductivity based on multi-size proppant packs provided by the present invention;

[0039] Figure 2 This is a numerical model of a three-particle-size packing material according to an embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of the permeability solution result of a numerical model according to an embodiment of the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] The purpose of this invention is to provide a method for predicting the flow capacity of cracks based on multi-size proppant packs, thereby solving the technical problem of errors in the averaging method used in the prior art when predicting proppant permeability.

[0043] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Hydraulic fracturing involves using a high-pressure pump on the surface to inject a high-viscosity fracturing fluid into the oil reservoir through the wellbore. When the injection rate of the fracturing fluid exceeds the reservoir's absorption capacity, a very high pressure is created at the bottom of the well. When this pressure exceeds the fracturing pressure of the rock in the nearby reservoir, the reservoir is forced open, creating fractures. Continuing to inject fracturing fluid further propagates the fractures into the reservoir. To keep the fractures open, a proppant-carrying fluid is injected. This proppant-carrying fluid, once inside the fractures, both allows them to extend further and supports the already opened fractures, preventing them from closing. Simultaneously, the proppant significantly increases the permeability of the fractures, thereby enhancing production.

[0045] To evaluate fracturing effectiveness, predict oil and gas well productivity, and further optimize hydraulic fracturing design for better economic benefits, conductivity prediction is crucial. In conductivity prediction, permeability is a critical parameter. Permeability can be calculated from proppant particle size. However, in hydraulic fracturing, the proppant filling the fracture is not composed of particles of uniform size, but rather particles within a certain range of screen sizes. Since different proppant sizes affect the permeability of the supported fracture, previous studies generally used average particle size or weighted average particle size instead of the actual particle size for permeability prediction, resulting in errors compared to the actual results. Therefore, reducing the errors in existing permeability prediction methods and providing a more accurate and realistic method for predicting fracture conductivity using multi-size proppant packs is of great significance for optimizing hydraulic fracturing operations.

[0046] Figure 1 The flowchart illustrates a method for predicting the crack conductivity of a multi-size proppant stack, as provided by this invention.

[0047] like Figure 1 As shown in this embodiment, a method for predicting the crack conductivity based on multi-size proppant packs includes:

[0048] Step 1: Obtain the composition of the multi-size proppant pack, including the proppant particle size composition and number;

[0049] When designing proppant combinations or after hydraulic fractures are subjected to pressure, proppants typically have a diverse particle size composition. When designing proppant combinations, those skilled in the art can obtain the composition details through specific proportions. In one embodiment, those skilled in the art can also obtain the particle size composition and number of the combined proppants using image analysis methods.

[0050] Specifically, the proppant is evenly spread within a designated area, ensuring the proppant particles are evenly distributed. An image of the proppant is then captured using a camera. After acquiring the image, it is converted to grayscale, binarized, and a threshold is selected. The proppant particle size distribution is then statistically analyzed. By extracting sample images from the processed proppant, data such as the number of proppant particles and their area are obtained. This allows for the analysis of particle size distribution information, filtering out particles with excessively small areas and removing outliers. The diameter of each particle is calculated based on the statistical data, and the results are then compiled to create a particle size distribution curve.

[0051] The above processing yields a multi-size proppant aggregate composed of n single-size groups, specifically (d0-d1, d1-d2, ... d...). n-1 -d n ).

[0052] Step 2: Calculate the equivalent particle size of the multi-size proppant pack;

[0053]

[0054] Among them, D mn Where i is the equivalent particle size, n is the number of the i-th type of proppant, and D is the equivalent particle size. i Let be the particle size of the i-th type of proppant.

[0055] For proppant aggregates composed of two particle sizes, the inventors established a method for calculating the equivalent particle size using analytical derivation, and verified the calculation method in step two.

[0056] Assume the core is of length L and cross-sectional area A, and there are N dissolution tubes in the rock, each with a cross-sectional radius r. Now, a fluid of viscosity μ is passed through the core with a pressure difference of ΔP.

[0057] According to a single dissolution hole, Poiseuille's law applies:

[0058]

[0059] In the formula, q is the volumetric flow rate; r is the radius of the pore; ΔP is the pressure difference; μ is the fluid viscosity; and l is the pore length.

[0060] Substituting Darcy's formula into the equation, we get:

[0061]

[0062] In the formula, k is the permeability; A is the cross-sectional area of ​​the seepage; L is the apparent length of the seepage channel; and l is the length of the solution pore.

[0063] Introducing the definition of tortuosity, which is the ratio of the actual path traveled by a fluid particle to the apparent length of the rock, we have:

[0064]

[0065] available

[0066]

[0067] Since there are N solution channels, the porosity of the entire rock is:

[0068]

[0069] The overall specific surface area is:

[0070]

[0071]

[0072] Substituting the specific surface area formula into the permeability calculation formula yields the KC equation considering capillary action, i.e.:

[0073]

[0074] Suppose there are n particles distributed within a rock core, each with a diameter of D. Then the specific surface area of ​​the rock core is:

[0075]

[0076] This yields the KC equation based on the packing of equal-sized particles:

[0077]

[0078] Based on this, assuming there are n particles with diameter D1 and m particles with diameter D2, forming a porosity of... An accumulation of material.

[0079]

[0080] Where D m Defined as equivalent particle size, the expression is written as:

[0081]

[0082] The equivalent particle size of the proppant composed of the two particle sizes can be obtained by degenerating the equivalent particle size calculation formula of the multi-particle-size proppant pack in step two. Therefore, it can be seen that the equivalent particle size proposed in this application is reliable.

[0083] Step 3: Obtain the permeability of the multi-size proppant stack;

[0084]

[0085] k is the permeability of the multi-size proppant stack. For porosity, C k This is a correction factor;

[0086] A permeability prediction model for multi-size proppant sand piles was established using numerical simulation software, and its prediction results were compared with the permeability prediction results proposed in this application.

[0087] like Figure 2 As shown, taking a composite packing of three types of particles as an example, a numerical model of a three-particle-size packing was established, and the permeability was solved. Figure 3 This is a schematic diagram of the permeability solution obtained from the numerical model. Table 1 shows a comparison between the numerical simulation results and the prediction method proposed in this application. As can be seen from the results in Table 1, the Darcy permeability obtained from the numerical simulation is almost equal to the equivalent permeability obtained by the method in this application, with an error of 0.85%. Therefore, the prediction method proposed in this application has strong applicability.

[0088] Table 1 Comparison of Simulation Parameters and Results

[0089]

[0090] Step 4: Predict the conductivity of the fracture;

[0091] D f =k*w f

[0092] In the formula, D f For fracture conductivity, w f The width of the seam.

[0093] On the other hand, the present invention provides a crack conductivity prediction system based on multi-size proppant packs, comprising:

[0094] The module for acquiring the composition of proppant stacks with multiple particle sizes is used to acquire the composition of proppant stacks, including the particle size composition and number of proppant particles.

[0095] An equivalent particle size acquisition module is used to calculate the equivalent particle size of multi-size proppant packs.

[0096] A permeability determination module is used to obtain the permeability of multi-size proppant packs;

[0097] A flow conductivity prediction module is used to predict the flow conductivity of cracks.

[0098] The specific functions and effects implemented by the electronic device in this embodiment can be explained by comparison with other embodiments, and will not be repeated here.

[0099] On the other hand, the present invention provides a computer-readable storage medium storing instructions for causing a machine to execute the crack conductivity prediction method based on multi-size proppant packs described in this application.

[0100] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for predicting the crack conductivity based on multi-size proppant packs, characterized in that, Includes the following steps: Step 1: Obtain the composition of the multi-size proppant pack using image analysis methods. The composition includes the proppant particle size distribution and number. Specifically, this includes: evenly spreading the proppant within a designated area and evenly distributing the proppant particles, and acquiring image information of the proppant using a camera device; After obtaining the proppant image information, the proppant image is converted into a grayscale image by a computer, the grayscale image is binarized, the corresponding threshold is selected, the proppant particle information in the image is statistically analyzed, the proppant particle size distribution is obtained, and a particle size distribution curve is plotted. Based on the proppant particle size distribution information, the number of particles with too small an area is filtered out, and outlier data is eliminated; Step 2: Based on Poiseuille's law and Darcy's formula, establish the KC equation considering the capillary, where the KC equation is: Where k is the penetration rate, Where τ is porosity, S is specific surface area, and τ is tortuosity. Assuming the proppant particles are distributed within the core, the specific surface area of ​​the core is: Where D is the particle size of the proppant; Furthermore, the KC equation for multi-size proppant packs was obtained. Substituting the specific surface area of ​​the multi-size proppant pack into the KC equation, a method for calculating the equivalent particle size of the multi-size proppant pack is obtained. The specific surface area of ​​multi-size proppant packs is calculated as follows: The method for calculating the equivalent particle size of multi-size proppant packs is as follows: Among them, D mn Where i is the equivalent particle size and n is the index. i D represents the number of the i-th type of proppant. i Let be the particle size of the i-th type of proppant; Step 3: Obtain the permeability of the multi-size proppant stack; The method for obtaining the permeability of the multi-size proppant pack in step three is as follows: k is the permeability of the multi-size proppant stack. For porosity, C k This is a correction factor; Step 4: Predict the conductivity of the fracture. D f =k*w f In the formula, D f For fracture conductivity, w f The width of the seam.

2. The method for predicting the crack conductivity based on multi-size proppant packs according to claim 1 further includes: A numerical model of multi-size proppant packings was established and validated using the numerical model.

3. A fracture conductivity prediction system based on multi-size proppant deposits, to implement the fracture conductivity prediction method based on multi-size proppant deposits as described in any one of claims 1-2, characterized in that, include: The module for acquiring the composition of the proppant mass is used to acquire the composition of the multi-size proppant mass through image analysis methods. The composition includes the proppant particle size composition and the number of particles. Specifically, this includes: evenly spreading the proppant within a designated area and evenly distributing the proppant particles, and acquiring image information of the proppant using a camera device; After obtaining the proppant image information, the proppant image is converted into a grayscale image by a computer, the grayscale image is binarized, the corresponding threshold is selected, the proppant particle information in the image is statistically analyzed, the proppant particle size distribution is obtained, and a particle size distribution curve is plotted. Based on the proppant particle size distribution information, the number of particles with too small an area is filtered out, and outlier data is eliminated; An equivalent particle size acquisition module is used to calculate the equivalent particle size of multi-size proppant packs. Based on Poiseuille's law and Darcy's formula, the KC equation considering capillary tubes is established, where the KC equation is: Where k is the penetration rate, Where τ is porosity, S is specific surface area, and τ is tortuosity. Assuming the proppant particles are distributed within the core, the specific surface area of ​​the core is: Where D is the particle size of the proppant; The KC equation for the proppant-supported mass was further obtained. Substituting the specific surface area of ​​the multi-size proppant pack into the KC equation, a method for calculating the equivalent particle size of the multi-size proppant pack is obtained. The specific surface area of ​​multi-size proppant packs is calculated as follows: The method for calculating the equivalent particle size of multi-size proppant packs is as follows: Among them, D mn Where i is the equivalent particle size and n is the index. i D represents the number of the i-th type of proppant. i Let be the particle size of the i-th type of proppant; A permeability determination module is used to obtain the permeability of multi-size proppant packs; The method for obtaining the permeability in the permeability determination module is as follows: k is the permeability of the multi-size proppant stack. For porosity, C k This is a correction factor; A flow conductivity prediction module is used to predict the flow conductivity of cracks.

4. A computer device, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for predicting the crack conductivity based on multi-size proppant packs as described in any one of claims 1-2.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for predicting the crack conductivity based on multi-size proppant packs as described in any one of claims 1-2.

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