Selection Method of Long-life Production Tubing String for Oil and Water Wells

Abstract

The present invention provides a method for selecting a long-life production tubing for oil and water wells, comprising: step 1, conducting corrosion and wear performance experiments of different types of oil pipes under different working conditions; step 2, conducting strength evaluation of eccentrically worn oil pipes, corroded oil pipes, and eccentrically worn and corroded oil pipes; step 3, establishing a prediction model for eccentric wear, corrosion, and eccentric wear and corrosion of oil pipes based on the results of the above experiments and strength evaluations; step 4, calculating the service life of different types of oil pipes in oil and water wells based on the above life prediction model, and selecting usable oil pipes based on long life requirements; step 5, selecting suitable oil pipes based on long life production requirements and considering economic benefits. The method for selecting a long-life production tubing for oil and water wells solves the problem of how to select oil pipes for oil and water wells with eccentric wear and corrosion, ensures that oil and water wells achieve long-life production, and improves production and development benefits.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield development, and in particular to a method for selecting a long-life production pipe string for an oil and water well. Background Art

[0002] During the development of oil fields, the production of oil and water wells is affected by factors such as temperature, mineralization, pressure, flow rate, and water content, and there are problems of corrosion and eccentric wear; especially after the oil field enters the middle and late stages of development, the corrosion and eccentric wear of oil pipes are becoming increasingly prominent. Therefore, various types of anti-corrosion and wear-resistant oil pipe products are used in the production of oil and water wells. Various oil pipes have different processing technologies, performance indicators, and costs, and their production life under different production conditions is also different. At present, there is no effective method to guide oil and water wells under different working conditions to select the appropriate type of oil pipe that can meet the long life requirements and improve the economic benefits of oil and water wells.

[0003] There is currently a method for predicting the life of an oil tubing string, with patent application number: 201310094925.2, which specifically includes calculating the maximum stress of a new oil tubing string; calculating the maximum stress of the oil tubing string at a certain time; calculating the tensile safety factor of the new oil tubing string; calculating the tensile safety factor of the oil tubing string at a certain time based on the tensile safety factor of the new oil tubing string calculated above; when the tensile safety factor of the oil tubing string at the certain time is equal to a preset safety factor threshold, the decreasing time of the tensile safety factor of the oil tubing string is the tensile safety life of the oil tubing string.

[0004] This application still has the following defects: the calculation process is too simplified, and physical model experiments are not carried out to obtain corresponding data based on the detailed working conditions of specific oil and water wells. Therefore, the maximum stress of the oil pipe cannot be accurately calculated, which will affect the accuracy of the life prediction. In addition, this method does not consider the influence of eccentric wear of the oil pipe, so it can only be used to predict the life of the oil pipe string of water injection wells and electric submersible pump wells, but cannot predict the life of the oil pipe string of the pumping well, and cannot guide the selection of oil pipe types for pumping wells.

[0005] A two-stage tubing string life prediction method, patent application number: 201310094742.0, mainly includes respectively calculating the initial maximum stress of the large-sized and small-sized tubing strings of the two-stage tubing strings, the maximum stress of the tubing strings at a certain time, and the tensile safety factor of the tubing strings, and calculating the tensile safety factor of the tubing strings at a certain time based on the tensile safety factor of the tubing strings calculated above. When the tensile safety factor of the tubing strings at a certain time is equal to a preset safety factor threshold, the decreasing time of the tensile safety factor of the tubing strings is the tensile safety life of the tubing strings.

[0006] This application still has the following defects: the calculation of the maximum stress of the oil pipe is too simplified, and the maximum stress of the oil pipe cannot be accurately calculated, which affects the accuracy of the prediction of the life of the oil pipe string. In addition, this method does not take into account the influence of eccentric wear of the oil pipe, so it can only be used to predict the life of the oil pipe string in water injection wells and electric submersible pump wells, but cannot predict the life of the oil pipe string in pumping wells, and cannot guide the selection of oil pipe types for pumping wells.

[0007] "Model and Software Development for Prediction of Wear Life of Rod and Tube in Vertical Wells", Master's thesis of Yanshan University in 2014: Mainly based on the static equilibrium method, the helical buckling configuration of the rod column and the calculation method of the rod-tube contact pressure were established; the mechanical model and mathematical model of the rod column buckling under the influence of normal force were established; the calculation model of the rod-tube contact pressure under the influence of normal force after the rod column was bent was established; based on the wear energy theory, a calculation model for the wear of the rod and tubing was established; using ANSYS finite element software, the maximum equivalent stress of the worn rod column and tubing was analyzed respectively, and a regression model of the maximum wear depth and stress concentration coefficient was established; based on the fatigue damage theory, a life prediction model for the rod column and tubing was established.

[0008] This article still has the following defects: in the process of establishing the tubing string life prediction model, physical simulation experiments were not carried out to obtain corresponding data based on the specific working conditions of the oil and water wells; only the influence of tubing eccentric wear was considered, but tubing corrosion was not considered, which affected the accuracy of tubing string life prediction. In addition, this method cannot be applied to the life prediction of tubing in water injection wells and submersible pump wells, and cannot guide the selection of tubing types for water injection wells and submersible pump wells.

[0009] "Research on the Prediction Method of Eccentric Wear Life of Rod and Tube in Polymer Drive Pumping Wells", 2016, Master's thesis of Yanshan University: Mainly based on the energy wear theory, considering the change of wear depth, a calculation model of rod and tube wear is established; based on the static strength theory, a life prediction model of rod and tube string is established; using ANSYS finite element analysis software, the maximum equivalent stress of the damaged rod and tube string is analyzed as the change law of the maximum wear depth, and then the relationship between the stress concentration factor of the damaged part of the rod and tube and the maximum wear depth is solved; based on the fatigue damage theory, taking the rod and tube string as the research object, a mathematical model for predicting its service life is established.

[0010] This article still has the following defects: in the process of establishing the tubing string life prediction model, only the influence of tubing eccentric wear is considered, while tubing corrosion is not considered, which affects the accuracy of tubing string life prediction. In addition, this method cannot be applied to the life prediction of tubing in water injection wells and submersible pump wells, and cannot guide the selection of tubing types for water injection wells and submersible pump wells.

[0011] At present, there are many methods to predict the life of tubing strings to guide the selection of tubing types, but the following two problems are common: first, physical model experiments are not conducted based on the specific working conditions of oil and water wells to obtain corresponding data, so the prediction accuracy is low; second, the scope of application is small, only a single factor is considered, and the tensile strength and internal pressure resistance are not comprehensively considered; the combined influencing factors of corrosion and eccentric wear are not comprehensively considered, and the life prediction accuracy is low, which still needs to be improved.

[0012] To this end, we have invented a new method for selecting long-life production tubing for oil and water wells, which solves the above technical problems. Summary of the invention

[0013] The purpose of the present invention is to provide a method for selecting a long-life production pipe string for oil and water wells, which can ensure the long-life production of oil and water wells and improve the production and development benefits.

[0014] The purpose of the present invention can be achieved through the following technical measures: a method for selecting a long-life production tubing for oil and water wells, the method comprising: step 1, conducting corrosion and wear performance experiments on different types of oil pipes under different working conditions; step 2, conducting strength evaluation on eccentrically worn oil pipes, corroded oil pipes and eccentrically worn and corroded oil pipes; step 3, establishing a life prediction model for eccentric wear, corrosion and eccentric wear and corrosion of oil pipes based on the results obtained from the above experiments and strength evaluations; step 4, calculating the service life of different types of oil pipes in oil and water wells based on the above life prediction model, and selecting usable oil pipes based on long life requirements; step 5, selecting suitable oil pipes based on long life production requirements and taking economic benefits into consideration.

[0015] The purpose of the present invention can also be achieved by the following technical measures:

[0016] In step 1, for the corrosion experiment, according to the working conditions in the electric submersible pump well, the pumping well and the water injection well, corrosion experiments are carried out on different types of oil pipes under different temperatures, pressures, flow rates and salinities, and the corrosion rates of various types of oil pipes are calculated.

[0017] In step 1, for the wear test, according to the working conditions of the pumping well, wear tests are carried out on different types of oil pipes at different temperatures, pressures, mineralization degrees, and flow rates, and the wear rates of various types of oil pipes are calculated.

[0018] In step 2, for electric submersible pump wells or water injection wells, only the corrosion factor is considered, the strength of the corroded tubing is evaluated, and the maximum corrosion depth h is calculated. f .

[0019] In step 2, for the pumping well, when the corrosion is judged to be light according to the working conditions, only the eccentric wear factor is considered, the eccentric wear oil pipe strength evaluation is carried out, and the maximum eccentric wear depth h is calculated. p .

[0020] In step 2, when the corrosion is serious, it is necessary to consider both eccentric wear and corrosion factors, evaluate the strength of the eccentric wear corrosion oil pipe, and calculate the maximum eccentric wear corrosion depth h pf .

[0021] In step 3, for the submersible pump well or water injection well, the corrosion rate formula is fitted according to the results obtained from the above experiment:

[0022] v f =β1k 2 +β2t 2 +β3v 2 +β4p 2 +β5kt+β6kv+β7kp+β8tv+

[0023] β9tp+β 10 vp+β 11 k+β 12 t+β 13 v+β 14 p+β 15 ,

[0024] Where β1,β2...β 15 is the unknown coefficient, k is the mineralization, t is the temperature, v is the flow rate, p is the pressure, v f is the corrosion rate;

[0025] The unknown coefficient is calculated by the following formula: T Xβ=X T Y, where

[0026]

[0027] Y=[y1 y2 … y m ] T , where the numbers in the lower right corners of the parameters in X and Y represent the corresponding experimental numbers of a certain working condition, β=[β1 β2 … β 15 ] T ;

[0028] The maximum corrosion depth h calculated based on the above strength f , the service life of the oil pipe under this condition is calculated as: This is the prediction model of oil pipe corrosion life, where l f Corrosion life of the oil pipe.

[0029] In step 3, for the pumping well, when the corrosion is light, only the eccentric wear is considered. According to the results of the above experiment, the wear evaluation factor of the corresponding working condition is calculated as follows: Where f is the wear evaluation factor, V 试验 is the volume of the sample worn away by the wear test, P 试验is the experimental pressure, L 试验 For experimental trip;

[0030] According to the above calculation, the eccentric wear depth is: h(s)=fPL(s), where h(s) is the eccentric wear depth changing with time, s is time, P is pressure, and L(s) is the friction stroke;

[0031] The maximum eccentric wear depth h calculated based on the above strength p According to the following formula, the eccentric wear life of the oil pipe can be calculated: h p =h(s), the time s is the eccentric wear life of the oil pipe l p , this is the prediction model of oil pipe eccentric wear life.

[0032] In step 3, when the corrosion is serious, it is necessary to consider the eccentric wear and corrosion. According to the above calculation, the eccentric wear corrosion depth is: h2(s) = h(s) + v f ·s, where h2(s) is the eccentric wear corrosion depth varying with time, h(s) is the eccentric wear depth varying with time, and v f is the corrosion rate; the maximum eccentric wear corrosion depth h calculated according to the above strength pf ;

[0033] The eccentric wear corrosion life of the oil pipe is calculated according to the following formula:

[0034] h pf =h2(s), the time s is the eccentric wear corrosion life of the oil pipe l pf This is the prediction model of oil pipe eccentric wear corrosion life.

[0035] In step 4, for electric submersible pump wells or water injection wells, there are multiple types of tubing to choose from, but according to the long life requirement, the service life of the tubing must be greater than a set value. The operating conditions of this well are brought into the above tubing corrosion life prediction model to calculate the service life of all types of tubing. Only tubing with a service life greater than the set value can be selected for use.

[0036] In step 4, for the pumping well, there are multiple types of tubing to choose from, but according to the long life requirement, the service life of the tubing must be greater than a set value. If the corrosion is light according to the working conditions, the working conditions are brought into the above-mentioned tubing eccentric wear life prediction model to calculate the service life of all types of tubing. Only tubing with a service life greater than the set value can be selected for use.

[0037] In step 4, if the corrosion is serious, the operating conditions are brought into the above-mentioned oil pipe eccentric wear corrosion life prediction model to calculate the service life of all types of oil pipes. Only the oil pipes with a service life greater than the set value can be selected for use.

[0038] In step 5, the average daily operating cost is calculated, and the oil pipe with low average daily operating cost is preferably used; average daily operating cost = (investment in a certain type of oil pipe + investment in other operating materials + investment in operating labor) / predicted life of a certain type of oil pipe.

[0039] The method for selecting a long-life production tubing string for oil and water wells in the present invention solves the problem of how to select tubing for oil and water wells with eccentric wear and corrosion, ensures that the oil and water wells can achieve long-life production, and improves production and development benefits. Based on corrosion and wear experiments, tubing strength analysis and eccentric wear, corrosion, and eccentric wear and corrosion life predictions are carried out, and tubing is preferably used according to long life requirements and economic benefits, providing a basis for the reasonable selection of long-life production tubing strings, helping to reduce production costs and improve development benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 The present invention is a flow chart of a specific embodiment of the method for selecting a long-life production tubing string for oil and water wells. DETAILED DESCRIPTION

[0041] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0042] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0043] The method for selecting a long-life production tubing string for oil and water wells of the present invention comprises the following steps:

[0044] In step 1, corrosion and wear performance experiments of different types of oil pipes under different working conditions are carried out;

[0045] For corrosion experiments, according to the working conditions in electric submersible pump wells, oil pumping wells and water injection wells, corrosion experiments were carried out on different types of oil pipes at different temperatures, pressures, flow rates and salinity, and the corrosion rates of various types of oil pipes were calculated; for wear experiments, according to the working conditions of oil pumping wells, wear experiments were carried out on different types of oil pipes at different temperatures, pressures, salinity and flow rates, and the wear rates of various types of oil pipes were calculated;

[0046] In step 2, the strength of the eccentrically worn oil pipe, the corroded oil pipe and the eccentrically worn and corroded oil pipe is evaluated.

[0047] For electric submersible pump wells or water injection wells, only the corrosion factor needs to be considered, the strength of the corroded tubing needs to be evaluated, and the maximum corrosion depth h needs to be calculated. f For pumping wells, when the corrosion is judged to be light according to the working conditions, only the eccentric wear factor is considered, and the strength of the eccentric wear oil pipe is evaluated to calculate the maximum eccentric wear depth h. p When the corrosion is serious, it is necessary to consider both eccentric wear and corrosion factors, evaluate the strength of the eccentric wear corrosion oil pipe, and calculate the maximum eccentric wear corrosion depth h pf .

[0048] In step 3, a prediction model for the eccentric wear, corrosion and eccentric wear-corrosion life of the oil pipe is established based on the results obtained from the above experiments and strength evaluation.

[0049] For electric submersible pump wells or water injection wells, the corrosion rate formula can be fitted based on the results obtained from the above experiments:

[0050] v f =β1k 2 +β2t 2 +β3v 2 +β4p 2 +β5kt+β6kv+β7kp+β8tv+

[0051] β9tp+β 10 vp+β 11 k+β 12 t+β 13 v+β 14 p+β 15 ,

[0052] Where β1,β2...β 15 is the unknown coefficient, k is the mineralization, t is the temperature, v is the flow rate, p is the pressure, v f is the corrosion rate.

[0053] The unknown coefficient can be calculated by the following formula: T Xβ=X T Y, where

[0054]

[0055] Y=[y1 y2 … y m ] T , where the numbers in the lower right corners of the parameters in X and Y represent the corresponding experimental numbers of a certain working condition, β=[β1 β2 … β 15 ] T .

[0056] The maximum corrosion depth h calculated based on the above strength f , the service life of the oil pipe under this condition is calculated as: This is the prediction model of oil pipe corrosion life, where l f Corrosion life of the oil pipe.

[0057] For pumping wells, when the corrosion is relatively light, only eccentric wear can be considered. According to the results of the above experiments, the wear evaluation factor of the corresponding working condition is calculated as follows: Where f is the wear evaluation factor, V 试验 is the volume of the sample worn away by the wear test, P 试验 is the experimental pressure, L 试验 According to the above calculation, the eccentric wear depth is: h(s) = fPL(s), where h(s) is the eccentric wear depth that changes with time, s is time, P is pressure, and L(s) is the friction stroke; the maximum eccentric wear depth h obtained by the above strength calculation is p According to the following formula, the eccentric wear life of the oil pipe can be calculated: h p =h(s), the time s is the eccentric wear life of the oil pipe l p , this is the prediction model of oil pipe eccentric wear life.

[0058] When the corrosion is serious, it is necessary to consider the eccentric wear and corrosion. According to the above calculation, the eccentric wear corrosion depth is: h2(s) = h(s) + v f ·s, where h2(s) is the eccentric wear corrosion depth varying with time, and the maximum eccentric wear corrosion depth h calculated based on the above strength is pf ; Calculate the eccentric wear corrosion life of the oil pipe according to the following formula:

[0059] h pf =h2(s), the time s is the eccentric wear corrosion life of the oil pipe l pf This is the prediction model of oil pipe eccentric wear corrosion life.

[0060] In step 4, the service life of different types of tubing in the oil and water wells is calculated according to the above-mentioned service life prediction model, and the usable tubing is selected according to the long service life requirement.

[0061] In one embodiment, for example, for a certain submersible pump well or water injection well, there are multiple types of tubing to choose from, but according to the long life requirement, the service life of the tubing must be greater than a set value. The operating conditions of this well are brought into the above-mentioned tubing corrosion life prediction model to calculate the service life of all types of tubing, and only tubing with a service life greater than the set value can be selected for use.

[0062] In another embodiment, for example, for a certain oil pumping well, there are multiple types of oil pipes to choose from, but according to the long life requirement, the service life of the oil pipe must be greater than a set value. If the corrosion is relatively light according to the working condition, the working condition is brought into the above-mentioned oil pipe eccentric wear life prediction model to calculate the service life of all types of oil pipes, and only the oil pipes with a service life greater than the set value can be selected for use. If the corrosion is relatively serious, the working condition is brought into the above-mentioned oil pipe eccentric wear corrosion life prediction model to calculate the service life of all types of oil pipes, and only the oil pipes with a service life greater than the set value can be selected for use.

[0063] In step 5, a suitable oil pipe is selected based on the long-life production requirement and taking economic benefits into consideration.

[0064] The specific algorithm is to calculate the average daily operating cost, and preferably use the oil pipe with low average daily operating cost. Average daily operating cost = (investment in a certain type of oil pipe + investment in other operating materials + investment in operating labor) / predicted life of a certain type of oil pipe.

[0065] In a specific embodiment of the present invention, Figure 1 As shown, Figure 1 The flowchart of the method for selecting a long-life production string for oil and water wells of the present invention comprises the following steps:

[0066] Step 101, conduct corrosion and wear performance tests of different types of oil pipes under different working conditions. For corrosion tests, according to the working conditions in electric submersible pump wells, oil pumping wells and water injection wells, corrosion tests are conducted on different types of oil pipes at different temperatures, pressures, flow rates and salinities, and the corrosion rates of various types of oil pipes are calculated; for wear tests, according to the working conditions in oil pumping wells, wear tests are conducted on different types of oil pipes at different temperatures, pressures, salinities and flow rates, and the wear rates of various types of oil pipes are calculated;

[0067] Step 102: Perform strength evaluation on the eccentrically worn tubing, corroded tubing, and eccentrically worn corroded tubing. For electric submersible pump wells or water injection wells, only the corrosion factor needs to be considered to perform strength evaluation on the corroded tubing and calculate the maximum corrosion depth h. f For pumping wells, when the corrosion is judged to be light according to the working conditions, only the eccentric wear factor is considered, and the strength of the eccentric wear oil pipe is evaluated to calculate the maximum eccentric wear depth h. p When the corrosion is serious, it is necessary to consider both eccentric wear and corrosion factors, evaluate the strength of the eccentric wear corrosion oil pipe, and calculate the maximum eccentric wear corrosion depth h pf .

[0068] Step 103: Establish a prediction model for eccentric wear, corrosion and eccentric wear-corrosion life of the oil pipe based on the results of the above experiments and strength evaluation.

[0069] For electric submersible pump wells or water injection wells, the corrosion rate formula can be fitted based on the results obtained from the above experiments:

[0070] v f =β1k 2 +β2t 2 +β3v 2 +β4p 2 +β5kt+β6kv+β7kp+β8tv+

[0071] β9tp+β 10 vp+β 11 k+β 12 t+β 13 v+β 14 p+β 15 ,

[0072] Where β1,β2...β 15 is the unknown coefficient, k is the mineralization, t is the temperature, v is the flow rate, p is the pressure, v f is the corrosion rate.

[0073] The unknown coefficient can be calculated by the following formula: T Xβ=X T Y, where

[0074]

[0075] Y=[y1 y2 … y m ] T , where the numbers in the lower right corners of the parameters in X and Y represent the corresponding experimental numbers of a certain working condition, β=[β1 β2 … β 15 ] T .

[0076] The maximum corrosion depth h calculated based on the above strength f , the service life of the oil pipe under this condition is calculated as: This is the prediction model of oil pipe corrosion life, where l f Corrosion life of the oil pipe.

[0077] For pumping wells, when the corrosion is relatively light, only eccentric wear can be considered. According to the results of the above experiments, the wear evaluation factor of the corresponding working condition is calculated as follows: Where f is the wear evaluation factor, V 试验 is the volume of the sample worn away by the wear test, P 试验 is the experimental pressure, L 试验According to the above calculation, the eccentric wear depth is: h(s) = fPL(s), where h(s) is the eccentric wear depth that changes with time, s is time, P is pressure, and L(s) is the friction stroke; the maximum eccentric wear depth h obtained by the above strength calculation is p According to the following formula, the eccentric wear life of the oil pipe can be calculated: h p =h(s), the time s is the eccentric wear life of the oil pipe l p , this is the prediction model of oil pipe eccentric wear life.

[0078] When the corrosion is serious, it is necessary to consider the eccentric wear and corrosion. According to the above calculation, the eccentric wear corrosion depth is: h2(s) = h(s) + v f ·s, where h2(s) is the eccentric wear corrosion depth varying with time, and the maximum eccentric wear corrosion depth h calculated based on the above strength is pf The eccentric wear corrosion life of the oil pipe is calculated according to the following formula:

[0079] h pf =h2(s), the time s is the eccentric wear corrosion life of the oil pipe l pf This is the prediction model of oil pipe eccentric wear corrosion life.

[0080] Step 104, calculate the service life of different types of tubing in the oil and water wells according to the above-mentioned life prediction model, and select the available tubing according to the long life requirement. For example, for a certain submersible pump well or water injection well, there are multiple types of tubing to choose from, but according to the long life requirement, the service life of the tubing needs to be greater than 1500 days. The working conditions of this well are brought into the above-mentioned tubing corrosion life prediction model to calculate the service life of all types of tubing, and only tubing with a service life greater than 1500 days can be selected for use. For another example, for a certain pumping well, there are multiple types of tubing to choose from, but according to the long life requirement, the service life of the tubing needs to be greater than 1500 days. According to the working conditions, if the corrosion is relatively light, the working conditions are brought into the above-mentioned tubing eccentric wear life prediction model to calculate the service life of all types of tubing, and only tubing with a service life greater than 1500 days can be selected for use. If the corrosion is relatively serious, the working conditions are brought into the above-mentioned tubing eccentric wear corrosion life prediction model to calculate the service life of all types of tubing, and only tubing with a service life greater than 1500 days can be selected for use.

[0081] Step 105: Based on the long-life production requirements and considering economic benefits, select the appropriate oil pipe. The specific algorithm is to calculate the average daily operating cost, and preferably use the oil pipe with low average daily operating cost. Average daily operating cost = (investment in a certain type of oil pipe + investment in other operating materials + investment in operating labor) / predicted life of a certain type of oil pipe.

[0082] The present invention aims at electric submersible pump wells, oil pumping wells and water injection wells. Through corrosion and wear experiments, as well as eccentric wear, corrosion and eccentric wear corrosion oil pipe strength analysis, the present invention establishes an eccentric wear, corrosion and eccentric wear corrosion life prediction model for oil pipes, calculates the service life of different types of oil pipes under different well conditions, and then selects the oil pipes that can be used under these well conditions according to the long life requirements, providing guidance for the selection of oil pipes for different oil and water wells, and ensuring the reliability and economy of oil field development.

[0083] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0084] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. A method for selecting a long-life production string for oil and water wells, characterized in that: The method for selecting a long-life production string for oil and water wells includes: Step 1, conducting corrosion and wear performance tests on different types of oil pipes under different working conditions; Step 2, performing strength evaluation on the eccentrically worn oil pipe, the corroded oil pipe and the eccentrically worn and corroded oil pipe; Step 3, based on the results of the above experiments and strength evaluation, establish a prediction model for eccentric wear, corrosion and eccentric wear and corrosion life of the oil pipe; Step 4, calculating the service life of different types of tubing in oil and water wells according to the above-mentioned service life prediction model, and selecting the usable tubing according to the long service life requirement; Step 5: Select appropriate tubing based on long-life production requirements and economic benefits; In step 2, for electric submersible pump wells or water injection wells, only the corrosion factor needs to be considered, the strength of the corroded tubing is evaluated, and the maximum corrosion depth h is calculated. f ; For pumping wells, when the corrosion is judged to be light according to the working conditions, only the eccentric wear factor is considered, and the strength of the eccentric wear oil pipe is evaluated to calculate the maximum eccentric wear depth h p When the corrosion is serious, it is necessary to consider both eccentric wear and corrosion factors, evaluate the strength of the eccentric wear corrosion oil pipe, and calculate the maximum eccentric wear corrosion depth h pf ; In step 3, for the pumping well, when the corrosion is light, only the eccentric wear is considered. According to the results of the above experiment, the wear evaluation factor of the corresponding working condition is calculated as follows: Where f is the wear evaluation factor, V 试验 is the volume of the sample worn away by the wear test, P 试验 is the experimental pressure, L 试验 For experimental trip; The eccentric wear depth varying with time is calculated as h(s)=fPL(s), where h(s) is the eccentric wear depth varying with time, P is the pressure, and L(s) is the friction stroke; Calculate the eccentric wear life of the oil pipe according to the following formula: h p =h(s), the time s is the eccentric wear life of the oil pipe l p , this is the prediction model of oil pipe eccentric wear life; In step 3, when the corrosion is severe, it is necessary to consider the eccentric wear and corrosion, and calculate the eccentric wear corrosion depth h2(s) = h(s) + v f ·s, where h2(s) is the eccentric wear corrosion depth varying with time, h(s) is the eccentric wear depth varying with time, and v f is the corrosion rate; The eccentric wear and corrosion life of the oil pipe can be calculated according to the following formula: h pf =h2(s), the time s is the eccentric wear corrosion life of the oil pipe l pf This is the prediction model of oil pipe eccentric wear corrosion life.

2. The method for selecting a long-life production tubing string for oil and water wells according to claim 1, characterized in that: In step 1, for the corrosion experiment, according to the working conditions in the electric submersible pump well, the pumping well and the water injection well, corrosion experiments are carried out on different types of oil pipes under different temperatures, pressures, flow rates and salinities, and the corrosion rates of various types of oil pipes are calculated.

3. The method for selecting a long-life production tubing string for oil and water wells according to claim 1, characterized in that: In step 1, for the wear test, according to the working conditions of the pumping well, wear tests are carried out on different types of oil pipes at different temperatures, pressures, mineralization degrees, and flow rates, and the wear rates of various types of oil pipes are calculated.

4. The method for selecting a long-life production tubing string for oil and water wells according to claim 1, characterized in that: In step 3, for the submersible pump well or water injection well, the corrosion rate formula is fitted according to the results obtained from the above experiment: v f =β1k 2 +β2t 2 +β3v 2 +β4p 2 +β5kt+β6kv+β7kp+β8tv+ β9tp+β 10 vp+b 11 k+b 12 t+b 13 v+b 14 p+β 15 , Where β1,β2...β 15 is the unknown coefficient, k is the mineralization, t is the temperature, v is the flow rate, p is the pressure, v f is the corrosion rate; The unknown coefficient is calculated by the following formula: T Xβ=X T Y, where Y=[y1 y2…y m ] T , where the numbers in the lower right corners of the parameters in X and Y represent the corresponding experimental numbers, β = [β1β2…β 15 ] T ; The maximum corrosion depth h calculated based on the above strength f , the service life of the oil pipe under this condition is calculated as: This is the prediction model of oil pipe corrosion life, where l f Corrosion life of the oil pipe.

5. The method for selecting a long-life production tubing string for oil and water wells according to claim 1, characterized in that: In step 4, for electric submersible pump wells or water injection wells, there are multiple types of tubing to choose from, but according to the long life requirement, the service life of the tubing must be greater than a set value. The operating conditions of this well are brought into the above tubing corrosion life prediction model to calculate the service life of all types of tubing. Only tubing with a service life greater than the set value can be selected for use.

6. The method for selecting a long-life production tubing string for oil and water wells according to claim 1, characterized in that: In step 4, for the pumping well, there are multiple types of tubing to choose from, but according to the long life requirement, the service life of the tubing must be greater than a set value. If the corrosion is light according to the working conditions, the working conditions are brought into the above-mentioned tubing eccentric wear life prediction model to calculate the service life of all types of tubing. Only tubing with a service life greater than the set value can be selected for use.

7. The method for selecting a long-life production tubing string for oil and water wells according to claim 6, characterized in that: In step 4, if the corrosion is serious, the operating conditions are brought into the above-mentioned oil pipe eccentric wear corrosion life prediction model to calculate the service life of all types of oil pipes. Only the oil pipes with a service life greater than the set value can be selected for use.

8. The method for selecting a long-life production tubing string for oil and water wells according to claim 1, characterized in that: In step 5, the average daily operating cost is calculated, and the oil pipe with the lowest average daily operating cost is used; average daily operating cost = (investment in a certain type of oil pipe + investment in other operating materials + investment in operating labor) / predicted life of a certain type of oil pipe.

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