Method for predicting maximum erosion rate of shale gas well deflecting section

Abstract

The invention discloses a method for predicting the maximum erosion rate of a shale gas well deflecting section, and the method specifically comprises the following steps: S1, building a shale gas well deflecting section erosion analysis original model by using Fluent software according to the operation characteristics of a shale gas well; s2, correcting the shale gas well deflecting section erosion analysis original model to obtain a shale gas well deflecting section erosion analysis correction model; s3, shale gas well deflecting sections of different structures are drawn and imported into the shale gas well deflecting section erosion analysis correction model, and then meshing is carried out to obtain a shale gas well deflecting section erosion analysis grid model; s4, determining a plurality of groups of simulation schemes, and solving the shale gas well deflecting section erosion analysis grid model by adopting a second-order windward difference scheme and an SIMPLE algorithm to obtain a corresponding simulated erosion rate; and S5, determining a prediction model of the maximum erosion rate of the shale gas deflecting section according to the simulated erosion rate corresponding to each group of simulation schemes.

Description

Technical Field

[0001] The invention relates to the technical field of shale gas well safety, and in particular to a method for predicting the maximum erosion rate of a shale gas well deflection section. Background Art

[0002] In recent years, as the contradiction between the increasing domestic demand for resources and the decreasing conventional oil and gas resources on land has intensified, my country has gradually increased its efforts in the research and development of shale gas. Due to the unique reservoir characteristics of shale gas, in actual on-site production, the method of fracturing first and then mining is generally adopted, which causes some sand particles in the formation to enter the wellbore during mining, causing significant erosion effect on the wellbore. Among them, the erosion of the deflection section in the wellbore is the most serious. Determining the maximum erosion rate of the deflection section is of great significance to ensuring the safe operation of shale gas wells.

[0003] In order to reduce the wear of production equipment by erosion, increase the service life of equipment, and reduce the property loss caused by erosion and wear, researchers at home and abroad have carried out a lot of theoretical and experimental research as early as the mid-nineteenth century. After decades of development, researchers have proposed a variety of wear theories and calculation formulas related to wear amount (rate) in the study of erosion and wear. These calculation formulas have been verified by experiments and found that the formulas themselves have a certain range of applicable conditions.

[0004] At present, the research on wellbore erosion mainly focuses on the analysis of the influence of fluid characteristic parameters on the erosion of the pipe wall. However, in the actual field, the operating parameters of shale gas are different at different stages of production, and the diameter of the wellbore and the curvature of the deflection elbow will also vary according to engineering needs. At present, the accuracy of predicting the maximum erosion rate of the deflection section when different operating parameters are coupled with different structural parameters is low. Summary of the invention

[0005] In view of the technical problem in the prior art that the maximum erosion rate of the deflection section when different operating parameters are coupled with different structural parameters has low accuracy, the present invention discloses a method for predicting the maximum erosion rate of the deflection section of a shale gas well, which can improve the prediction accuracy of the maximum erosion rate of the deflection section of shale gas wells with different structures under different working conditions, and provide a basis for the operation and management of shale gas wells.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for predicting the maximum erosion rate of a shale gas well deflection section specifically comprises the following steps:

[0008] S1: Based on the operating characteristics of shale gas wells, the original model for erosion analysis of the deflection section of shale gas wells was established using Fluent software;

[0009] S2: The original model of erosion analysis of the deflection section of a shale gas well is modified to obtain a modified model of erosion analysis of the deflection section of a shale gas well;

[0010] S3: drawing the shale gas well deflection sections with different structures, importing the erosion analysis correction model of the shale gas well deflection section, and then performing gridding to obtain the erosion analysis grid model of the shale gas well deflection section;

[0011] S4: Determine multiple simulation schemes, use the second-order upwind difference format and SIMPLE algorithm to solve the erosion analysis grid model of the shale gas well deflection section to obtain the corresponding simulated erosion rate;

[0012] S5: According to the simulated erosion rates corresponding to each group of simulation schemes, a prediction model for the maximum erosion rate of the shale gas deflection section is determined, and the maximum erosion rate of the shale gas well deflection section is output.

[0013] Preferably, in S1, the operating characteristics of the shale gas well include physical parameters, structural parameters and operating parameters; wherein the physical parameters include particle size d and particle concentration C; the structural parameters include curvature radius R and wellbore inner diameter D; and the operating parameters include gas flow velocity u.

[0014] Preferably, in S1, the expression of the original model for erosion analysis of the deflection section of a shale gas well is:

[0015]

[0016] In formula (1), E R represents the mass loss per unit area per unit time; n represents the number of particles; N p Indicates the total number of particles; A f Represents the unit surface area on the wall of the shale gas well deflection section; m pn represents the mass flow rate of particles; c(d pn ) represents the function of particle diameter; f(a) represents the function of impact angle a; represents the relative velocity of the particles; b(v pn ) represents the function of the relative velocity of the particles.

[0017] Preferably, in S2, the corrected expression is:

[0018]

[0019] In formula (2), c′ represents the correction parameter; E R represents the mass loss per unit area per unit time; n represents the number of particles; N p Indicates the total number of particles; A f Represents the unit surface area on the wall of the shale gas well deflection section; m pn represents the mass flow rate of particles; c(dpn ) represents the function of particle diameter; f(a) represents the function of impact angle a; represents the relative velocity of the particles; b(v pn ) represents the function of the relative velocity of the particles.

[0020] Preferably, in S3, a structured grid is used to divide the grid of the erosion analysis correction model of the shale gas well deflection section, and the grid of the boundary layer is encrypted.

[0021] Preferably, in S4, before determining the simulation scheme, the boundary conditions of the model should be set:

[0022] Set the boundary condition of the inlet to velocity inlet, the boundary condition of the outlet to outflow, the boundary condition of the pipe wall to "rebound", and both the inlet and outlet are set to "escape".

[0023] Preferably, in S4, the simulation scheme includes:

[0024] (1) The particle size is set as a variable, and the particle concentration, curvature radius, wellbore inner diameter, and gas flow velocity are set as quantitative;

[0025] (2) setting particle concentration as a variable, and setting particle size, curvature radius, wellbore inner diameter, and gas flow velocity as quantitative;

[0026] (3) The radius of curvature is set as a variable, and the particle size, particle concentration, wellbore inner diameter, and gas flow velocity are set as quantitative;

[0027] (4) The inner diameter of the wellbore is set as a variable, and the particle size, particle concentration, curvature radius, and air flow velocity are set as quantitative;

[0028] (5) The air flow velocity is set as a variable, and the particle size, particle concentration, curvature radius, and wellbore inner diameter are set as quantitative.

[0029] Preferably, in S5, the prediction model expression of the maximum erosion rate of the shale gas deflection section is:

[0030] ln(y)=α 1 +α 2 ln(u)+α 3 ln(d)+α 4 ln(R)+α 5 ln(D)+α 6 ln(C) (3)

[0031] In formula (3), y represents the maximum erosion rate of the shale gas deflection section; α 1 , α 2 , α 3 , α 4 , α5 , α 6 They represent the simulation coefficients respectively; u represents the air flow velocity; d represents the particle size; R represents the curvature radius of the deflection section; D represents the inner diameter of the wellbore of the deflection section; and C represents the particle concentration.

[0032] In summary, due to the adoption of the above technical solution, compared with the prior art, the present invention has at least the following beneficial effects:

[0033] The present invention is based on the analysis of the operating characteristics of shale gas wells, and uses Fluent to perform numerical simulation on the deflection section of shale gas wells under different physical parameters, operating parameters and structural parameters; based on the simulation data, a maximum erosion rate prediction model for the deflection section of shale gas wells is established to predict the maximum erosion rate of the deflection section of shale gas wells with different structures under different working conditions, thereby improving the accuracy of the prediction of the maximum erosion rate of the deflection section and providing a basis for the operation and management of shale gas wells. Description of the drawings:

[0034] Figure 1 It is a schematic diagram of a method for predicting the maximum erosion rate of a shale gas well deflection section according to an exemplary embodiment of the present invention.

[0035] Figure 2 Schematic diagram of analyzing the effect of particle size on simulated erosion rate according to an exemplary embodiment of the present invention.

[0036] Figure 3 Schematic diagram of analyzing the effect of particle concentration on simulated erosion rate according to an exemplary embodiment of the present invention.

[0037] Figure 4 Schematic diagram of analyzing the effect of the curvature radius on the simulated erosion rate according to an exemplary embodiment of the present invention.

[0038] Figure 5 Schematic diagram of analysis of the effect of the inner diameter of the wellbore on the simulated erosion rate according to an exemplary embodiment of the present invention.

[0039] Figure 6 Schematic diagram of analyzing the effect of gas flow velocity on simulated erosion rate according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the examples and specific implementation methods. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0041] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0042] like Figure 1 As shown, the present invention provides a method for predicting the maximum erosion rate of the deflection section of a shale gas well, which specifically includes the following steps:

[0043] S1: According to the operating characteristics of shale gas wells, the original model for erosion analysis of the deflection section of shale gas wells was established using Fluent software.

[0044] In this embodiment, the operating characteristics of the shale gas well include physical parameters, structural parameters and operating parameters; the physical parameters include particle size d and particle concentration C; the structural parameters include curvature radius R and wellbore inner diameter D; and the operating parameters include inlet velocity u.

[0045] In this embodiment, the expression of the original model for erosion analysis of the deflection section of a shale gas well is:

[0046]

[0047] In formula (1), E R represents the mass loss per unit area per unit time; n represents the number of particles; N p Indicates the total number of particles; A f Represents the unit surface area on the wall of the shale gas well deflection section; m pn represents the mass flow rate of particles; c(d pn ) represents the function of particle diameter; f(a) represents the function of impact angle a; represents the relative velocity of the particles; b(v pn ) represents the function of the relative velocity of the particles (converted from physical parameters, structural parameters and operating parameters).

[0048] S2: In this embodiment, in order to improve the accuracy of calculation, a correction coefficient c′ is introduced to correct the original model of erosion analysis of the deflection section of shale gas wells to obtain a corrected model of erosion analysis of the deflection section of shale gas wells. The corrected expression is:

[0049]

[0050] In formula (2), c′ represents the correction parameter, which can be 1.06; E Rrepresents the mass loss per unit area per unit time; n represents the number of particles; N p Indicates the total number of particles; A f Represents the unit surface area on the wall of the shale gas well deflection section; m pn represents the mass flow rate of particles; c(d pn ) represents the function of particle diameter; f(a) represents the function of impact angle a; represents the relative velocity of the particles; b(v pn ) represents the function of the relative velocity of the particles.

[0051] S3: Use CAD\PROE to draw the shale gas well deflection section with different structures, import the erosion analysis correction model of the shale gas well deflection section, and then grid it to obtain the erosion analysis grid model of the shale gas well deflection section.

[0052] In this embodiment, structured grids are used for grid division, and the grids of the boundary layer are encrypted to improve the accuracy of the simulation.

[0053] S4: In the erosion analysis grid model of the shale gas well beveling section, the boundary condition of the inlet is set as the velocity inlet, the boundary condition of the outlet is set as outflow, the boundary condition of the pipe wall is set as "rebound", and both the inlet and outlet are set as "escape". Multiple groups of simulation schemes are determined, and the second-order upwind difference format (QUICK format) of the convection term and the pressure prediction-correction method (SIMPLE algorithm) are used to solve the erosion analysis grid model of the shale gas well beveling section to obtain the corresponding simulated erosion rate.

[0054] In this embodiment, the obtained simulated erosion rate is compared with the actual result, and based on the comparison result, the parameters of the erosion analysis grid model of the shale gas well build-up section (i.e., the operating characteristics of the shale gas well) are optimized until the relative deviation of the modified model is less than 10%.

[0055] In this embodiment, it is necessary to set parameters to determine multiple groups of simulation schemes, and then when solving the model separately, any parameter is set as a variable and the other parameters are set as quantitative:

[0056] (1) Set the particle size as a variable, and set the particle concentration, curvature radius, wellbore inner diameter, and gas flow velocity as quantitative, and obtain an analysis chart of the effect of particle size on the simulated erosion rate, as shown in Figure 2 As shown in Figure 2, with the increase of particle size, the simulated erosion rate gradually decreases;

[0057] (2) Set the particle concentration as a variable, and the particle size, curvature radius, wellbore inner diameter, and gas flow velocity as quantitative factors to obtain an analysis chart of the effect of particle concentration on the simulated erosion rate, as shown in Figure 3 As shown in Figure 2, with the increase of particle concentration, the simulated erosion rate gradually increases;

[0058] (3) The curvature radius is set as a variable, and the particle size, particle concentration, wellbore inner diameter, and gas flow velocity are set as quantitative, and an analysis diagram of the effect of the curvature radius on the simulated erosion rate is obtained, as shown in Figure 4 As shown in Figure 2, with the increase of curvature radius, the simulated erosion rate gradually decreases;

[0059] (4) The inner diameter of the wellbore is set as a variable, and the particle size, particle concentration, curvature radius, and air flow velocity are set as quantitative factors to obtain an analysis diagram of the effect of the inner diameter of the wellbore on the simulated erosion rate, as shown in Figure 5 As shown in the figure, as the inner diameter of the wellbore increases, the simulated erosion rate gradually decreases;

[0060] (5) The air flow velocity is set as a variable, and the particle size, particle concentration, curvature radius, and wellbore inner diameter are set as quantitative factors to obtain an analysis diagram of the effect of air flow velocity on the simulated erosion rate, such as Figure 6 As shown in Figure 2, with the increase of air flow velocity, the simulated erosion rate gradually increases.

[0061] S5: According to the simulated erosion rates corresponding to each group of simulation schemes, the prediction model of the maximum erosion rate of the shale gas deflection section is determined, and the maximum erosion rate of the shale gas well deflection section is output:

[0062] ln(y)=α 1 +α 2 ln(u)+α 3 ln(d)+α 4 ln(R)+α 5 ln(D)+α 6 ln(C) (3)

[0063] In formula (3), y represents the maximum erosion rate of the shale gas deflection section; α 1 , α 2 , α 3 , α 4 , α 5 , α 6 They represent the simulation coefficients respectively; u represents the air flow velocity; d represents the particle size; R represents the curvature radius of the deflection section; D represents the inner diameter of the wellbore of the deflection section; and C represents the particle concentration.

[0064] For example, in this embodiment, in order to improve the accuracy of the results, the operating characteristics of three shale gas wells are designed, as shown in Table 1.

[0065] Table 1 Operation characteristics of shale gas wells

[0066]

[0067] According to the operating characteristics of the three shale gas wells in Table 1, multiple simulation schemes can be determined to calculate the erosion rate. The simulation results are shown in Table 2.

[0068] Table 2. Simulation results of erosion rate in the deflection section of shale gas wells

[0069]

[0070]

[0071] In this embodiment, according to the simulation results in Table 2, the simulation coefficient α can be obtained: 1 , α 2 , α 3 , α 4 , α 5 , α 6 The value of , formula (3) is specifically expressed as:

[0072] ln(y)=1.555+0.2401ln(u)-0.071ln(d)-0.569ln(R)-0.3271ln(D)+0.7971ln(C)(3).

[0073] The variance analysis evaluation of the maximum erosion rate prediction model of the shale gas deflection section is shown in Table 3, and the regression coefficient of the prediction model is shown in Table 4.

[0074] Table 3. Analysis of the maximum erosion rate prediction model equation in the deflection section of shale gas wells

[0075] df SS MS F-Ratio P-Value Regression 5 9.094644 1.818929 42510022 2.3E-133 Residual error 40 1.71E-06 4.28E-08 Total 45 9.094646

[0076] Table 4. Regression coefficient analysis of the maximum erosion rate prediction model in the deflection section of shale gas wells

[0077]

[0078] As shown in Table 3, the model F value is 42510022, indicating that the maximum erosion rate prediction model is significant. The p value < 0.0001 indicates that the probability of the maximum F value is only 0.01%. If the P value is less than 0.05, it indicates that it is a significant item. As shown in Table 4, the multiples of R, R2 and Adj-R2 are greater than 0.9, and the standard error is relatively low. The results show that the model is in good agreement with the simulation value and can be used to analyze the maximum erosion rate of the deflection section of shale gas wells.

[0079] Those skilled in the art will appreciate that the above-mentioned embodiments are specific examples for implementing the present invention, and in actual applications, various changes may be made thereto in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A method for predicting the maximum erosion rate of the deflection section of a shale gas well. It is characterized in that The specific steps include: S1: Based on the operating characteristics of shale gas wells, the original model for erosion analysis of the deflection section of shale gas wells was established using Fluent software; S2: The original model of erosion analysis of the deflection section of a shale gas well is modified to obtain a modified model of erosion analysis of the deflection section of a shale gas well; S3: drawing the shale gas well deflection sections with different structures, importing the erosion analysis correction model of the shale gas well deflection section, and then performing gridding to obtain the erosion analysis grid model of the shale gas well deflection section; S4: Determine multiple groups of simulation schemes, use the second-order upwind difference format and SIMPLE algorithm to solve the erosion analysis grid model of the shale gas well deflection section to obtain the corresponding simulated erosion rate; S5: According to the simulated erosion rates corresponding to each group of simulation schemes, a prediction model for the maximum erosion rate of the shale gas deflection section is determined, and the maximum erosion rate of the shale gas well deflection section is output.

2. A method for predicting the maximum erosion rate of a shale gas well deflection section according to claim 1, It is characterized in that In S1, the operating characteristics of the shale gas well include physical parameters, structural parameters and operating parameters; the physical parameters include particle size d and particle concentration C; the structural parameters include curvature radius R and wellbore inner diameter D; and the operating parameters include gas flow velocity u.

3. A method for predicting the maximum erosion rate of a shale gas well deflection section according to claim 1, It is characterized in that In S1, the expression of the original model for erosion analysis of the deflection section of a shale gas well is: In formula (1), E R represents the mass loss per unit area per unit time; n represents the number of particles; N p Indicates the total number of particles; A f Represents the unit surface area on the wall of the shale gas well deflection section; m pn represents the mass flow rate of particles; c(d pn ) represents the function of particle diameter; f(a) represents the function of impact angle a; represents the relative velocity of the particles; b(v pn ) represents the function of the relative velocity of the particles.

4. A method for predicting the maximum erosion rate of a shale gas well deflection section according to claim 1, It is characterized in that In S2, the corrected expression is: In formula (2), c ′ represents the correction parameter; E R represents the mass loss per unit area per unit time; n represents the number of particles; N p Indicates the total number of particles; A f Represents the unit surface area on the wall of the shale gas well deflection section; m pn represents the mass flow rate of particles; c(d pn ) represents the function of particle diameter; f(a) represents the function of impact angle a; represents the relative velocity of the particles; b(v pn ) represents the function of the relative velocity of the particles.

5. A method for predicting the maximum erosion rate of a shale gas well deflection section according to claim 1, It is characterized in that In S3, a structured grid is used to divide the grid of the erosion analysis correction model of the shale gas well deflection section, and the grid of the boundary layer is encrypted.

6. A method for predicting the maximum erosion rate of a shale gas well deflection section according to claim 1, It is characterized in that In S4, before determining the simulation scheme, the boundary conditions of the model should be set: Set the boundary condition of the inlet to velocity inlet, the boundary condition of the outlet to outflow, the boundary condition of the pipe wall to "bounce", and both the inlet and outlet to "escape".

7. A method for predicting the maximum erosion rate of a shale gas well deflection section according to claim 1, It is characterized in that In S4, the simulation scheme includes: (1) The particle size is set as a variable, and the particle concentration, curvature radius, wellbore inner diameter, and gas flow velocity are set as quantitative; (2) setting particle concentration as a variable, and setting particle size, curvature radius, wellbore inner diameter, and gas flow velocity as quantitative; (3) The radius of curvature is set as a variable, and the particle size, particle concentration, wellbore inner diameter, and gas flow velocity are set as quantitative; (4) The inner diameter of the wellbore is set as a variable, and the particle size, particle concentration, curvature radius, and air flow velocity are set as quantitative; (5) The air flow velocity is set as a variable, and the particle size, particle concentration, curvature radius, and wellbore inner diameter are set as quantitative.

8. A method for predicting the maximum erosion rate of a shale gas well deflection section according to claim 1, It is characterized in that In S5, the prediction model expression of the maximum erosion rate of the shale gas deflection section is: ln(y)=α 1 +a 2 ln(u)+α 3 ln(d)+α 4 ln(R)+α 5 ln(D)+α 6 ln(C) (3) In formula (3), y represents the maximum erosion rate of the shale gas deflection section; α 1 , α 2 , α 3 , α 4 , α 5 , α 6 They represent the simulation coefficients respectively; u represents the air flow velocity; d represents the particle size; R represents the curvature radius of the deflection section; D represents the inner diameter of the wellbore of the deflection section; and C represents the particle concentration.

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