A prediction method for the liquid-solid erosion-corrosion initiation mechanism of oil well tubing based on micro-potential testing

Abstract

A prediction method for the liquid-solid erosion-corrosion initiation mechanism of oil well tubing based on micro-potential testing, characterized by using the correlation between fluid hydrodynamics and the mechanical properties of the corrosion product film, based on fracture mechanics and fluid dynamics theories, combining micro-potential technology, wavelet analysis method and fluid dynamics theory to test and characterize hydrodynamic parameters such as wall shear stress, diffusion current density, current noise, freak wave energy density and flow intensity of the liquid-solid two-phase flow of oil well tubing, using acoustic emission technology, nano-indentation technology, piston suction method and fracture mechanics theory to test and characterize the mechanical properties such as fracture strength, film-substrate bonding strength and elastic modulus of typical corrosion product films, comprehensively analyzing the magnitude relationship between the maximum flow intensity and wall shear stress and the fracture strength and film-substrate bonding strength of the corrosion product film, and judging the liquid-solid two-phase flow erosion-corrosion initiation mechanism. The present invention is applicable to the technical field of oil and gas drilling and production engineering.

Description

Technical Field

[0001] This patent relates to the technical field of oil and gas drilling and production engineering, and specifically to a prediction method for the liquid-solid erosion-corrosion initiation mechanism of oil well tubing based on micro-potential testing. Background Art

[0002] In the oil and gas industry, liquid-solid two-phase flow erosion-corrosion widely exists and is a relatively harmful form of local corrosion. During oil and gas production and transportation, the liquid phase medium flow velocities in various oil equipment (such as drilling blowout preventers, choke manifolds, and choke valves, as well as Christmas trees, flow nozzles, and oil casing pipes in oil and gas production) and pipelines are generally relatively high and most are corrosive. At the same time, the presence of solid-phase particles will cause the flow-through components to suffer from erosion-corrosion, leading to more serious damage. The phenomenon of the wall thickness of oil and gas pipeline materials thinning due to erosion-corrosion is becoming increasingly prominent. If not protected, it will seriously reduce production efficiency and increase the likelihood of accidents.

[0003] According to statistics, the losses caused by corrosion in the oil industry are particularly serious, accounting for about 6% of the gross national product, and up to 9% of corrosion failures are caused by erosion-corrosion. Currently, the most effective way to eliminate or reduce erosion-corrosion is to use corrosion-resistant alloys and optimize material selection and design. However, due to the high cost of corrosion-resistant alloys and unreasonable material selection, erosion-corrosion will still be triggered.

[0004] Current evaluation methods for erosion-corrosion mainly focus on laboratory experiments and numerical simulations. Among them, most laboratory experiments only study the critical conditions for corrosion generation and the effects of various conditions after corrosion on material corrosion. Numerical simulations, on the other hand, study full-scale models, mostly some regular studies, and rarely quantitatively judge and scientifically predict the liquid-solid erosion-corrosion initiation mechanism of oil well tubing. It should be noted that erosion-corrosion initiation refers to whether and when the integrity failure of oil well tubing caused by erosion-corrosion starts.

[0005] Therefore, the present invention overcomes the deficiencies of the prior art and provides a prediction method for the liquid-solid erosion-corrosion initiation mechanism of oil well tubing based on micro-potential testing. This method can optimize material selection and design under liquid-solid two-phase erosion-corrosion environments, minimize or reduce the erosion-corrosion of oil well pipe materials to the greatest extent, and use advanced experimental devices and micro-potential testing methods to conduct research on liquid-solid two-phase flow erosion-corrosion, further clarify the erosion-corrosion mechanism, and form a method for predicting the initiation / start of erosion-corrosion. This method can quantitatively judge whether the liquid-solid erosion-corrosion of oil well tubing starts and the failure mechanism, realize scientific prediction of the integrity failure of oil well pipes caused by erosion-corrosion under extreme service conditions, diagnose in advance the possible failure symptoms of oil well pipes, and provide technical support for solving the safety problems brought by erosion-corrosion and on-site production. Summary of the Invention

[0006] The object of the present invention is to provide a prediction method for the liquid-solid erosion-corrosion initiation mechanism of oil well pipes based on micro-potential testing, so as to clarify the erosion-corrosion mechanism of liquid-solid two-phase flow on oil pipes. This method is simple and feasible, can systematically reflect the erosion-corrosion mechanism, and can quickly judge whether erosion-corrosion starts, when it starts, and the failure mechanism.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A prediction method for the liquid-solid erosion-corrosion initiation mechanism of oil well pipes based on micro-potential testing, the method mainly includes the following steps:

[0009] Step 1: Obtain the actual service conditions of oil and gas well pipes on site, the attribute parameters of the casing, and the on-site working condition parameters;

[0010] Step 2: According to the actual production parameters of the oil and gas well, calculate and determine the flow velocity range and solid phase content range, and carry out the liquid-solid two-phase flow experiment of the oil well pipe under simulated temperature, pressure and different flow velocities to prepare for the determination of the key hydrodynamic parameters of the flowing fluid;

[0011] Step 3: According to the GB / T2423.51-2012 standard, carry out a static corrosion experiment on the oil well pipe coupon specimens under the temperature, pressure and corrosive medium in Step 2 to obtain the oil well pipe coupon specimens covered with sufficient corrosion product films, and prepare for the determination of the key mechanical properties of the corrosion product films of the oil well pipes;

[0012] Step 4: Use the micro-potential technology to measure the diffusion current density, current noise, and freak wave energy density of freak waves in the liquid-solid two-phase flow;

[0013] Step 5: Based on the diffusion current density, current noise, and freak wave energy density obtained in Step 4, use the Levéque equation and wavelet analysis method to calculate and obtain the wall shear stress τ w and the average flow intensity I turb and the maximum flow intensity

[0014]

[0015] Step 6: Take the wall shear stress τ w and the average flow intensity I turb and the maximum flow intensity obtained in Step 5 as the key hydrodynamic parameters of the flowing fluid;

[0016] Step 7: Use nano-indentation technology to measure the elastic modulus E of the corrosion product film;

[0017] Step 8: Use the four-point bending method and acoustic emission technology to jointly measure the fracture strain of the corrosion product film, and calculate the fracture strength σ of the corrosion product film based on the elastic modulus E obtained in Step 7 Br ;

[0018] Step 9: Use the piston suction method to measure the film-substrate bonding strength of the corrosion product film

[0019] Step 10: Take the fracture strength σ Br and the film-substrate bonding strength obtained in Step 8 and Step 9 as the key parameters of the mechanical properties of the corrosion product film on the oil well pipe;

[0020] Step 11: Compare the wall shear stress τ w , the maximum flow intensity of the hydrodynamic parameters of the flowing fluid with the film-substrate bonding strength and the fracture strength σ Br of the mechanical properties parameters of the corrosion product film, and judge whether erosion-corrosion occurs / starts: If or , then erosion-corrosion starts. On the contrary, if and , then erosion-corrosion does not start.

[0021] The service conditions of the on-site oil well pipe materials and the liquid-solid two-phase flow conditions in the pipeline in Step 1 include the attribute parameters of the casing, the on-site working conditions parameters, and the liquid-solid two-phase flow parameters; the attribute parameters of the casing include the casing size and the steel grade of the steel; the on-site working conditions parameters include the service temperature, pressure, and corrosive medium; the liquid-solid two-phase flow parameters include the fluid flow characteristics and the solid-phase particle characteristics.

[0022] The present invention has the following advantages:

[0023] By combining fracture mechanics and fluid dynamics theories, the present invention establishes the relationship between the hydrodynamic force acting on the corrosion product film and its mechanical properties, proposes a method for evaluating whether erosion-corrosion starts / germinates based on hydrodynamic parameters and the mechanical properties of the corrosion product film, obtains the critical flow intensity or wall shear stress for the germination / initiation of erosion-corrosion and the corresponding critical flow velocity, clarifies the germination mechanism of erosion-corrosion, and enables the oilfield to control or mitigate the erosion-corrosion of oil well pipe materials according to its specific working conditions. At the same time, the present invention can provide a practical and feasible new method and new technology for evaluating the initiation mechanism of liquid-solid erosion-corrosion of oil well pipe materials. Description of the Drawings

[0024] Figure 1 is the technical roadmap of the present invention. Detailed Embodiments

[0025] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the following provides a detailed description of the technical solution of the present invention, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0026] The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

[0027] Referring to the accompanying drawings, the present invention proposes a method for predicting the liquid-solid erosion-corrosion initiation mechanism of oil well tubing based on micro-potential testing. The method mainly includes the following steps:

[0028] Step 1: Use P110 tubing in a certain oilfield in the western part of China, with an outer diameter of 73 mm, a wall thickness of 5.5 mm, a service temperature of 60 °C, a pressure of 20 MPa, a CO2 partial pressure of 0.25 MPa, a formation water type of CaCl2, and a salinity of up to 24209 mg / L;

[0029] Step 2: Calculate the flow velocity of the liquid-solid two-phase flow in the pipeline to be 18 m / s. The solid phase uses Al2O3 particles with a particle size of 20 - 80 μm, an average of 50 μm, and a particle mass flow rate of 10 g / min. Conduct an experimental study on the liquid-solid two-phase flow in the oil well pipe at a simulated temperature of 60 °C, a CO2 partial pressure (0.25 MPa), and a flow velocity of 18 m / s to prepare for the determination of the key hydrodynamic parameters of the flowing fluid;

[0030] Step 3: According to the GB / T 2423.51-2012 standard, use P110 tubing coupon specimens to conduct static corrosion experiments under the temperature, pressure, and corrosive medium in Step 2 to obtain P110 tubing coupon specimens covered with sufficient corrosion product films to prepare for the determination of the key mechanical properties of the corrosion product films of P110 tubing;

[0031] Step 4: Use the micro-potential technique to measure the diffusion current density, current noise, and deformed wave energy density of the deformed waves in the liquid-solid two-phase flow;

[0032] Step 5: Based on the diffusion current density, current noise, and deformed wave energy density obtained in Step 4, use the Levéque equation and wavelet analysis method to calculate the wall shear stress τ w = 762 Pa and the average flow intensity I turb = 47.6 MPa and the maximum flow intensity

[0033] Step 6: Take the wall shear stress τ w and the flow intensity I turb and the maximum flow intensity as the key hydrodynamic parameters of the flowing fluid;

[0034] Step 7: Use nanoindentation technology to measure the elastic modulus of the corrosion product film E = 2.2 GPa;

[0035] Step 8: Use the four-point bending method and acoustic emission technology to jointly measure the fracture strain of the corrosion product film, and calculate the fracture strength σ of the corrosion product film based on the elastic modulus E obtained in Step 7 Br = 55.6 MPa;

[0036] Step 9: Use the piston suction method to measure the film-substrate bonding strength of the corrosion product film

[0037] Step 10: Take the fracture strength σ obtained in Step 8 and Step 9 Br and the film-substrate bonding strength as the key parameters of the mechanical properties of the corrosion product film of the oil well pipe;

[0038] Step 11: Compare the wall shear stress τ of the hydrodynamic parameters of the flowing fluid w , the maximum flow intensity with the mechanical property parameters of the corrosion product film, the film-substrate bonding strength and the fracture strength σ Br to judge whether erosion-corrosion occurs / starts. The results show that: However When surface erosion-corrosion starts, P110 steel pipes will undergo erosion-corrosion failure under such service conditions.

[0039] As mentioned above, it is not any form of limitation to the present invention. Although the present invention has been disclosed by the above embodiments, it is not intended to limit the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, can make some changes or modifications to the above-disclosed technical content to form equivalent embodiments with equivalent changes. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A prediction method for the liquid-solid erosion-corrosion initiation mechanism of oil well tubing based on micro-potential testing, characterized in that, The method includes the following steps: Step 1: Obtain the actual service conditions of the oil and gas well tubing on site, the attribute parameters of the casing, and the on-site working condition parameters; Step 2: According to the actual production parameters of the oil and gas well, calculate and determine the flow velocity range and solid content range, and conduct experiments on the liquid-solid two-phase flow of the oil well pipe under simulated temperature, pressure, and different flow velocities to prepare for the determination of the key hydrodynamic parameters of the flowing fluid; Step 3: According to the GB / T2423.51-2012 standard, conduct static corrosion experiments on the temperature, pressure, and corrosion medium in Step 2 using the coupon specimens of the oil well pipe to obtain the coupon specimens of the oil well pipe covered with sufficient corrosion product films to prepare for the determination of the key mechanical properties of the corrosion product films of the oil well tubing; Step 4: Use the micro-potential technique to measure the diffusion current density, current noise, and freak wave energy density of the freak waves in the liquid-solid two-phase flow; Step Five: Based on the diffusion current density, current noise, and freak wave energy density obtained in Step Four, use the equation and wavelet analysis method to calculate the wall shear stress τ w and the average flow intensity I turb as well as the maximum flow intensity Step Six: Take the wall shear stress τ w and the average flow strength I turb as well as the maximum flow strength as the hydrodynamic key parameters of the flowing fluid; Step 7: Use the nano-indentation technique to measure the elastic modulus E of the corrosion product film; Step 8: Jointly measure the fracture strain of the corrosion product film by the four-point bending method and acoustic emission technology, and calculate the fracture strength σ of the corrosion product film based on the elastic modulus E obtained in Step 8 Br ; Step 9: Measure the film-substrate bonding strength of the corrosion product film by the piston suction method Step Ten: Take the fracture strength σ Br and the film-substrate bonding strength as the key parameters of the mechanical properties of the corrosion product film on the oil well pipe; Step Eleven: Compare the wall shear stress τ of the hydrodynamic parameters of the flowing fluid w , the maximum flow intensity with the film-substrate bonding strength of the mechanical property parameters of the corrosion product film and the fracture strength σ Br to judge whether erosion-corrosion occurs / starts: If there is or , then erosion-corrosion starts; on the contrary, if and , then erosion-corrosion does not start.

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