A downhole string erosion risk assessment method based on gas field production parameters

Abstract

The application discloses a kind of well down pipe string erosion risk assessment method based on gas field production parameters, comprising the following steps, step 1, based on the relationship between the deformation wear amount, cutting wear amount and particle impact load of parent material, the production situation is established;Step 2, based on the production pipe string structure, the gas-solid erosion prediction model of production pipe string is established, and the grid-independent solution is obtained;Step 3, according to the relationship between the deformation wear amount, cutting wear amount and particle impact load in step 1, the gas-solid erosion prediction model is optimized to the error within 5% range;Step 4, based on the direct relationship between the optimized gas-solid erosion prediction model and production parameters, determine the production parameters corresponding to the erosion degree;Step 5, establish three-dimensional critical production parameter chart containing yield, pressure, sand production, according to the production parameters in step 4, erosion risk assessment is carried out on production pipe string of different materials.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas extraction operations, specifically to a method for assessing downhole tubing erosion risk based on gas field production parameters. Background Technology

[0002] Downhole tubing is a crucial medium transport channel in oil and gas extraction operations. During production in gas storage facilities or high-yield gas fields, acid fracturing operations can easily cause proppant backflow or formation sand production, leading to erosion of the downhole production casing or tubing. This reduces the tubing's pressure resistance, tensile strength, and crush resistance, and in severe cases, can even cause leakage. This has become one of the main reasons affecting the safe production of downhole tubing in gas storage facilities or high-yield gas fields.

[0003] Due to the complex and harsh service environment of downhole tubing in gas storage facilities or gas fields, there is a lack of monitoring methods for the degree of tubing erosion, making it difficult to grasp the erosion status of the tubing. Removing the production casing or tubing for inspection or replacement not only leads to well shutdowns but also significantly increases the operating costs of the gas field. Furthermore, the corrosion resistance of production tubing made of different materials varies significantly, and the critical erosion velocity commonly used in oil and gas fields is mostly based on the API RP 14E standard, which does not consider the actual mechanical properties of the tubing material or individual differences in sand production and production conditions of the gas well, thus failing to provide reasonable guidance for actual production operations. Therefore, it is essential to develop a method that can consider key mechanical parameters affecting erosion resistance, such as the elastic modulus, hardness, and yield strength of the production casing, while also being able to assess the erosion of production tubing based on readily available field production parameters such as gas production rate, gas production pressure, and sand production rate, providing technical support for the safe production of high-yield gas wells or gas storage facilities.

[0004] Existing erosion prediction methods can be divided into two categories: empirical models and mechanistic models. Empirical models are mostly established by foreign universities or research institutions based on experimental results, such as the DNV model and the E / CRC model. However, due to the limitations of the experimental materials and working conditions, they are difficult to extend to different materials and production conditions in the field. Mechanistic models, such as the Finnie model, the Bitter model, and the Oka model, are more mature in their development for erosion prediction models of elasto-plastic materials such as downhole tubing than for brittle materials. However, no single model can fully explain the entire erosion process. Moreover, most of these mechanistic models only consider the properties of particles and lack quantification of key parameters affecting erosion, such as the hardness, elastic modulus, and yield strength of the matrix material. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for assessing the erosion risk of downhole tubing based on gas field production parameters. This method couples production parameters with the mechanical properties of the actual tubing, such as elastic modulus, hardness, and yield strength, to quantitatively assess the degree of erosion of the production tubing.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for assessing downhole tubing erosion risk based on gas field production parameters includes the following steps:

[0008] Step 1: Based on the on-site production conditions, establish the relationship between the deformation and wear of the base material, the cutting wear, and the particle impact load;

[0009] Step 2: Establish a gas-solid erosion prediction model for the production tubing based on the production tubing structure, and obtain a mesh-independent solution;

[0010] Step 3: Optimize the gas-solid erosion prediction model based on the relationship between deformation wear, cutting wear and particle impact load in Step 1 until the error is within 5%.

[0011] Step 4: Based on the optimized gas-solid erosion prediction model, establish the direct relationship between erosion rate and production parameters, and determine the production parameters corresponding to the degree of erosion.

[0012] Step 5: Establish a three-dimensional critical production parameter chart including output, pressure, and sand output, and conduct erosion risk assessment on production tubing of different materials based on the production parameters in Step 4.

[0013] Preferably, in step 1, an explicit dynamic analysis method is used to establish the relationship between the deformation and wear of the parent material, the cutting wear, and the particle impact load.

[0014] Preferably, step 1 specifically includes the following steps:

[0015] Step 11: Input the elastic modulus, hardness, and yield strength of the production tubing material into the single-particle erosion model;

[0016] Step 12: The single-particle erosion model establishes the relationship between deformation wear, cutting wear, and impact load based on different particle diameters, speeds, impact angles, and shapes.

[0017] The constitutive relationships between deformation wear, cutting wear, and impact load were obtained through nonlinear fitting.

[0018] Deformation wear refers to the amount of deformation parallel to the impact direction caused by impact load under a large impact angle of particles.

[0019] Cutting wear refers to the amount of deformation perpendicular to the impact direction caused by the impact of particles at a small impact angle under load, as well as the protruding lip that is higher than the surface of the base material.

[0020] Preferably, step 2 specifically includes the following steps:

[0021] Step 21: Establish a geometric model based on the wellbore trajectory;

[0022] Step 22, Obtaining the Mesh-Independent Solution: The optimal number of meshes is determined by refining the mesh, using the maximum erosion rate and the maximum erosion location as indicators.

[0023] Step 23: If the number of grids is too large and exceeds the computing capacity, an empirical trajectory at different well depths can be extracted to establish a geometric model and solve it in segments.

[0024] Preferably, step 3 specifically includes the following steps:

[0025] Step 31: Optimize the gas-solid erosion prediction model using the constitutive relationship between deformation wear, cutting wear, and particle impact load;

[0026] Step 32: Optimize the gas-solid erosion model based on existing erosion mechanism models or by extracting flow parameters from single particles.

[0027] Furthermore, in step 3, based on the existing erosion model optimization, the Bitter model is selected:

[0028]

[0029]

[0030] In the formula, V d V represents the erosion rate caused by deformation and wear. c Let z be the erosion rate caused by cutting wear, where z is the amount of deformation wear and q is the amount of cutting wear.

[0031] Furthermore, in step 3, optimization is performed based on the flow parameters of a single particle, selecting the particle cumulative erosion model from Fluent software:

[0032]

[0033] In the formula, f v (q p Let f be the deformation and wear amount expressed as a particle impact load function. t (q p ) represents the amount of cutting wear as a function of particle impact load.

[0034] Preferably, in step 4, the erosion risk level is determined based on the uniform or localized corrosion index of the NACE SP0775 standard.

[0035] Preferably, in step 5, the critical erosion rate for low and medium risk is 0.025 mm / a; the critical erosion rate for medium and high risk is 0.125 mm / a; and the critical erosion rate for high and severe risk is 0.25 mm / a.

[0036] Preferably, in step 5, the critical production parameter chart includes three coordinate values: production output, production pressure, and sand output, along with their corresponding erosion risk levels.

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

[0038] This invention provides a method for assessing downhole tubing erosion risk based on gas field production parameters. Addressing the current lack of erosion monitoring and risk assessment methods in gas storage facilities and high-yield gas fields, this method correlates the actual mechanical properties of the production tubing with an erosion prediction model, establishing a direct relationship between erosion risk and production parameters. This enables quantitative assessment of production tubing made of different materials based on production parameters. It considers the mechanical properties of specific tubing materials and allows for assessment of tubing erosion risk based on readily available field production parameters, quantitatively predicting the degree of erosion. This not only reasonably guides the inspection cycle of downhole tubing in gas storage facilities or high-yield gas fields but also effectively improves the production safety of production tubing and reduces production costs. Attached Figure Description

[0039] Figure 1 This is a flowchart of a downhole tubing erosion risk assessment method based on gas field production parameters.

[0040] Figure 2 This is a schematic diagram of a single-particle erosion model.

[0041] Figure 3 This refers to the deformation and wear caused by particles of different sizes.

[0042] Figure 4 For the production of tubular structures.

[0043] Figure 5 This relates the erosion rate to production and pressure.

[0044] Figure 6 This shows the relationship between erosion rate and sand output and pressure.

[0045] Figure 7 The output is 102.6 × 10 4 Sm 3 The relationship between erosion risk and pressure at / d.

[0046] Figure 8 This is a diagram showing the critical production parameters for N80 material. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0048] like Figure 1 As shown, the present invention provides a method for assessing downhole tubing erosion risk based on gas field production parameters, comprising the following steps:

[0049] Step 1: Based on the material of the production tubing, sand discharge conditions and production conditions on site, an explicit dynamic analysis method is used to establish single-particle erosion models with different shapes, sizes, angles and velocities, and to clarify the variation law of the deformation and wear of the parent material and the cutting wear with the particle impact load.

[0050] Step 2: Based on the production tubing structure, a gas-solid erosion prediction model for the production tubing is established using multiphase flow analysis software such as OpenFOAM and Fluent, and a mesh-independent solution is obtained.

[0051] Step 3: Couple the constitutive equations of deformation wear, cutting wear and particle impact load in Step 1 with the gas-solid erosion prediction model in Step 2) and solve them. Compare the model with the field erosion data or indoor simulated erosion test data, and optimize the model until the error is within 5%.

[0052] Step 4: Calculate the degree of erosion of the tubing under different gas production conditions using the modified erosion model in Step 3. Then, based on the discrimination index of local corrosion risk level proposed in NACE SP0775 standard, determine the gas production conditions corresponding to different erosion risk levels of the tubing material in the field.

[0053] Step 5: Based on the correspondence between the degree of erosion and the gas production conditions in Step 4, establish a critical production parameter chart for the tubing material under different erosion risk levels, and realize erosion risk assessment based on production parameters.

[0054] The evaluation method specifically includes, in step 1 above:

[0055] The elastic modulus, hardness, and yield strength parameters of the production tubing material can be obtained from testing or the supplier's test report;

[0056] The particle shape and particle size distribution in the single-particle erosion model are obtained based on the particle size analysis results of the sand produced on site.

[0057] The impact velocity of the particles can be determined by calculating the fluid velocity from data such as on-site production and pressure.

[0058] Deformation wear refers to the amount of deformation parallel to the impact direction caused by impact load under a large impact angle of particles.

[0059] Cutting wear refers to the amount of deformation perpendicular to the impact direction caused by the impact of particles at small impact angles under load, as well as the possible protruding lip above the surface of the base material.

[0060] The constitutive relationship between deformation wear, cutting wear, and impact load can be obtained through nonlinear fitting.

[0061] In the aforementioned evaluation method, step 2 specifically includes:

[0062] Step 21: The geometric model in OpenFOAM or Fluent software is determined by the field wellbore trajectory;

[0063] Step 22, Obtaining the Mesh-Independent Solution: The optimal number of meshes is determined by refining the mesh, using the maximum erosion rate and the maximum erosion location as indicators.

[0064] Step 23: If the number of grids is too large and exceeds the computing capacity, an empirical trajectory at different well depths can be extracted to establish a geometric model and solve it in segments.

[0065] In the aforementioned evaluation method, step 3 specifically includes:

[0066] Step 31: The constitutive equation of deformation wear, cutting wear and particle impact load is used to optimize the erosion model. This optimization can be based on the existing erosion model or by extracting the flow parameters of a single particle.

[0067] Step 32, based on the existing erosion model optimization, the Bitter model can be selected:

[0068]

[0069]

[0070] In the formula, V d V represents the erosion rate caused by deformation and wear. c Let z be the erosion rate caused by cutting wear, where z is the amount of deformation wear and q is the amount of cutting wear.

[0071] Step 33: Optimize based on the flow parameters of a single particle. The particle cumulative erosion model in Fluent software can be selected:

[0072]

[0073] In the formula, f v (q pLet f be the deformation and wear amount expressed as a particle impact load function. t (q p ) represents the amount of cutting wear as a function of particle impact load.

[0074] In the aforementioned evaluation method, step 4 specifically includes:

[0075] Step 41: By changing parameters such as output, pressure, and temperature, simulate the erosion rate under different working conditions to understand the relationship between the maximum erosion rate and erosion location and the production conditions.

[0076] Step 42: Referring to the corrosion risk level discrimination index in the NACE SP0775 standard, determine the corresponding gas production conditions under different erosion risks. The risk level discrimination index is as follows:

[0077] Critical erosion rate for low and medium risk: 0.025 mm / a; Critical erosion rate for medium and high risk: 0.125 mm / a; Critical erosion rate for high and severe risk: 0.25 mm / a.

[0078] In the aforementioned assessment method, step 5 specifically includes: the critical production parameter chart should include three coordinate values: production output, production pressure, and sand output, as well as their corresponding erosion risk levels.

[0079] Example

[0080] The example illustrates a method for assessing the erosion risk of an N80 production casing in a gas storage facility based on production parameters. The specific steps are as follows:

[0081] Based on the N80 material, sand output, and production conditions, the basic data required for the single-particle model were determined. For example, the N80 material has a hardness of 6.37 GPa, a yield strength of 652 MPa, and an elastic modulus of 311 GPa. The average particle size of the sand output is 0.59 mm, with a particle size distribution ranging from 0.425 mm to 1.19 mm. The fluid velocity is between 5.54 m / s and 12.61 m / s (with the same particle impact velocity). The corresponding production output range is 45.1 × 10⁻⁶. 4 Sm 3 / d~102.6×10 4 Sm 3 / d.

[0082] A single-particle erosion model was established based on the LS-DYNA explicit dynamic analysis method, such as... Figure 2 As shown, impact process simulations were performed under different impact loads to determine the relationship between the deformation of the parent material and the impact load on the particles. Figure 3 As shown.

[0083] A gas-solid erosion model was established based on the on-site production conditions, and the on-site production tubing structure was as follows: Figure 4 As shown. The inlet uses a velocity boundary, and the outlet uses a pressure boundary. The inlet velocity is determined by the production output, ranging from 5.54 m / s to 12.61 m / s; the outlet pressure is determined by the production conditions, ranging from 14.4 MPa to 27.7 MPa.

[0084] Using the relationship between deformation wear, cutting wear, and impact load from step 1, the gas-solid erosion model was corrected to within 5% error. Simulations were then conducted under different production conditions to understand the relationship between erosion rate and output, pressure, and sand production. Figures 5-6 As shown.

[0085] Referring to the corrosion risk assessment index in the NACE SP0775 standard, the relationship between different erosion risk levels and pressure at a specific production level was determined, such as... Figure 7 As shown.

[0086] Simulations were conducted at different production rates, and a three-dimensional critical production parameter chart based on production rate, pressure, and sand output was generated, such as... Figure 8 As shown, this enables erosion risk assessment based on production parameters.

[0087] Of course, the above description is only an embodiment of the present invention. The present invention is not limited to the above embodiments. It should be noted that any equivalent substitutions or obvious modifications made by those skilled in the art under the guidance of this specification fall within the scope of this specification and should be protected by the present invention.

Claims

1. A method for assessing downhole tubing erosion risk based on gas field production parameters, characterized in that, Includes the following steps, Step 1: Based on the on-site production conditions, establish the relationship between the deformation and wear of the base material, the cutting wear, and the particle impact load; Step 2: Establish a gas-solid erosion prediction model for the production tubing based on the production tubing structure, and obtain a mesh-independent solution; Step 3: Optimize the gas-solid erosion prediction model based on the relationship between deformation wear, cutting wear and particle impact load in Step 1 until the error is within 5%. Step 4: Based on the optimized gas-solid erosion prediction model, establish the direct relationship between erosion rate and production parameters, and determine the production parameters corresponding to the degree of erosion. Step 5: Establish a three-dimensional critical production parameter chart including output, pressure, and sand output, and conduct erosion risk assessment on production tubing of different materials based on the production parameters in Step 4.

2. The method for assessing downhole tubing erosion risk based on gas field production parameters according to claim 1, characterized in that, In step 1, an explicit dynamic analysis method is used to establish the relationship between the deformation and wear of the parent material, the cutting wear, and the particle impact load.

3. The method for assessing downhole tubing erosion risk based on gas field production parameters according to claim 1, characterized in that, Step 1 specifically includes the following steps: Step 11: Input the elastic modulus, hardness, and yield strength of the production tubing material into the single-particle erosion model; Step 12: The single-particle erosion model establishes the relationship between deformation wear, cutting wear, and impact load based on different particle diameters, speeds, impact angles, and shapes. The constitutive relationships between deformation wear, cutting wear, and impact load were obtained through nonlinear fitting. Deformation wear refers to the amount of deformation parallel to the impact direction caused by impact load under a large impact angle of particles. Cutting wear refers to the amount of deformation perpendicular to the impact direction caused by the impact of particles at a small impact angle under load, as well as the protruding lip that is higher than the surface of the base material.

4. The method for assessing downhole tubing erosion risk based on gas field production parameters according to claim 1, characterized in that, Step 2 specifically includes the following steps: Step 21: Establish a geometric model based on the wellbore trajectory; Step 22, Obtaining the Mesh-Independent Solution: The optimal number of meshes is determined by refining the mesh, using the maximum erosion rate and the maximum erosion location as indicators. Step 23: If the number of grids is too large and exceeds the computing capacity, an empirical trajectory at different well depths can be extracted to establish a geometric model and solve it in segments.

5. The method for assessing downhole tubing erosion risk based on gas field production parameters according to claim 1, characterized in that, Step 3 specifically includes the following steps: Step 31: Optimize the gas-solid erosion prediction model using the constitutive relationship between deformation wear, cutting wear, and particle impact load; Step 32: Optimize the gas-solid erosion model based on existing erosion mechanism models or by extracting flow parameters from single particles.

6. The method for assessing downhole tubing erosion risk based on gas field production parameters according to claim 5, characterized in that, In step 3, based on the existing erosion model optimization, the Bitter model is selected: In the formula, V d V represents the erosion rate caused by deformation and wear. c Let z be the erosion rate caused by cutting wear, where z is the amount of deformation wear and q is the amount of cutting wear.

7. The method for assessing downhole tubing erosion risk based on gas field production parameters according to claim 5, characterized in that, In step 3, optimization is performed based on the flow parameters of a single particle, and the particle cumulative erosion model in Fluent software is selected: In the formula, f v (q p Let f be the deformation and wear amount expressed as a particle impact load function. t (q p ) represents the amount of cutting wear as a function of particle impact load.

8. The method for assessing downhole tubing erosion risk based on gas field production parameters according to claim 1, characterized in that, In step 4, the erosion risk level is determined based on the uniform or localized corrosion index of the NACE SP0775 standard.

9. The method for assessing downhole tubing erosion risk based on gas field production parameters according to claim 1, characterized in that, In step 5, the critical erosion rate for low and medium risk is 0.025 mm / a; the critical erosion rate for medium and high risk is 0.125 mm / a; and the critical erosion rate for high and severe risk is 0.25 mm / a.

10. The method for assessing downhole tubing erosion risk based on gas field production parameters according to claim 1, characterized in that, In step 5, the critical production parameter chart includes three coordinate values: production output, production pressure, and sand output, along with their corresponding erosion risk levels.

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