Method and system for evaluating failure risk of test tubular column

Abstract

The invention discloses a method and system for evaluating the failure risk of a test tubular column. The method comprises the steps that shaft environment temperature and pressure information about the to-be-evaluated test tubular column is obtained; based on the temperature and pressure information of the shaft environment, determining the external load of the test tubular column and the corresponding tubular column strength, and based on the external load, respectively carrying out corresponding uncertainty analysis; according to the uncertainty analysis result of the external load and the strength, coupling characteristic analysis of the external load and the strength is carried out, and therefore the failure risk value of the test tubular column is obtained according to the external load characteristic and the strength characteristic. Aiming at deepwater high-temperature and high-pressure well completion test operation, the failure risk evaluation method of the well completion test tubular column is established, corresponding risk control measures are formulated according to the failure risk value of the high-temperature and high-pressure well completion test tubular column, and reliable theoretical guarantee and technical guidance are provided for smooth well completion test operation.

Description

Technical Field

[0001] The present invention relates to the technical field of deepwater gas well completion testing, and in particular to a method and system for evaluating the failure risk of a test string. Background Art

[0002] With the increase in energy demand, oil and gas exploration and development are gradually moving towards areas with more complex environments and richer reserves. The difficulty and risk of completion testing under deepwater high temperature and high pressure conditions far exceed those on land and shallow water. In the completion test of deepwater high temperature and high pressure gas wells, the completion test string is an important tool for this operation. It is a string system composed of oil pipes and test tools attached to the oil pipes. As the only flow channel for formation production fluid, the reliability of the completion test string is related to the success or failure of the completion test operation. In the actual completion test operation, the completion test string is affected by technical factors and environmental factors, and the various parameters in the string have certain uncertainties. In terms of string strength, there are uncertainties in elastic modulus, yield strength, etc. due to the influence of manufacturing process and environmental factors; in terms of string external load, there are also certain uncertainties in the density of produced fluid and test fluid, annular temperature and pressure distribution, etc. Therefore, it is necessary to evaluate the uncertainty of the completion test string, and then clarify the failure risk status of the string at the current stage.

[0003] At present, most of the research on completion test strings at home and abroad is aimed at the axial force of the test string, or judging the reliability of the packer on it based on the axial force of the string. This type of research takes into account the influence of environmental factors such as high temperature and high pressure. The axial force of the test string is mainly affected by the piston effect, swelling effect, temperature effect, spiral bending effect, and mechanical force effect. Axial mechanical and geometric changes occur in the wellbore, which leads to the risk of the packer losing its seal. In the prior art, there are few studies on the risk assessment of failure of high-temperature and high-pressure completion test strings. Basically, they are a judgment on mechanical failure, and no special quantitative risk assessment method has been formed. In the field of oil and gas drilling and completion, risk assessment methods related to uncertainty are all aimed at evaluating the integrity of the wellbore, rather than the completion test string.

[0004] In addition, the existing technology mainly uses the safety factor method for casing strength design and verification, that is, the casing strength should not be lower than the product of the external load and a certain safety factor. The current safety factor value range given in my country's petroleum industry standards is: anti-external squeeze safety factor 1.00-1.125, anti-internal pressure safety factor 1.05-1.15, and tensile safety factor 1.60-2.00. The safety factor is derived on the basis of a large number of design practices and reflects certain statistical characteristics. For different wells and casings, the value of this factor varies greatly. However, this method regards various parameters as fixed values, which results in its greater subjective arbitrariness. Moreover, during the drilling and production process, due to the occurrence of wear, corrosion and other phenomena, the actual value of the safety factor cannot clearly indicate the true safety level.

[0005] It can be seen that for the risk assessment of failure of high-temperature and high-pressure completion test strings, the existing technology needs to establish a solution that can simultaneously carry out stress risk and risk quantitative analysis of the test string. Summary of the invention

[0006] The present invention aims to provide a solution for evaluating the failure risk of a test string, so as to fully consider the uncertainty of various parameters of the test string during the actual completion test process, perform reliability evaluation on the parameters, and clarify the failure risk of the test string.

[0007] In order to solve the above technical problems, an embodiment of the present invention provides a method for evaluating the failure risk of a test string, comprising: obtaining wellbore environmental temperature and pressure information about the test string to be evaluated; based on the wellbore environmental temperature and pressure information, determining the external load of the test string and its corresponding string strength, and based on this, conducting corresponding uncertainty analysis respectively; according to the uncertainty analysis results of the external load and strength, performing coupling characteristic analysis of the external load and strength, so as to obtain the failure risk value of the test string according to the external load characteristics and the strength characteristics.

[0008] Preferably, the wellbore environmental temperature and pressure information includes but is not limited to: temperature distribution data in the test string, pressure distribution data in the test string, casing annulus temperature distribution data, casing annulus pressure distribution data, wellbore surrounding environment temperature distribution data and wellbore pressure and temperature distribution data.

[0009] Preferably, the process of determining the external load includes: calculating the external squeezing force and internal pressure of the test string at the depth to be evaluated; determining the external load by comparing the external squeezing force and internal pressure at the same depth, wherein if the external squeezing force is less than or equal to the internal pressure, the effective internal pressure at the current depth is used as the external load, and if the external squeezing force is greater than the internal pressure, the current effective external squeezing force is used as the external load.

[0010] Preferably, the process of determining the strength of the tubular string includes: determining the corresponding tubular string strength according to the form of the external load, wherein if the form of the external load is effective internal pressure, the internal pressure resistance of the currently tested tubular string is used as the tubular string strength; if the form of the external load is effective external extrusion force, the external extrusion resistance of the currently tested tubular string is used as the tubular string strength.

[0011] Preferably, in the process of carrying out uncertainty analysis of external load and strength respectively, it includes: determining the uncertainty of external load through simulation analysis according to the external load of the test string at different depths, and obtaining the normal distribution probability density curve of external load at the corresponding depth; determining the uncertainty of strength through simulation analysis according to the strength of the test string at different depths, and obtaining the normal distribution probability density curve of strength at the corresponding depth.

[0012] Preferably, in the process of obtaining the coupling characteristic analysis of the external load and the strength, it includes: drawing a probability density curve graph of the normal distribution of the external load and a probability density curve graph of the normal distribution of the strength respectively; integrating the probability density curve graph of the external load and the probability density curve graph of the strength into the same coordinate system and carrying out probability density interference state analysis, so as to determine the coupling characteristics.

[0013] Preferably, in the process of calculating the failure risk value of the test string, the following steps are included: if the external load probability density curve and the strength probability density curve have no overlapping interference area, and each strength distribution value in the curve under the current same coordinate system is greater than or equal to the external load data, then the risk value of the current test string at the current depth is determined to be 0%; if the external load probability density curve and the strength probability density curve have no overlapping interference area, and each strength distribution value in the curve under the current same coordinate system is less than the external load data, then the risk value of the current test string at the current depth is determined to be 100%; if the external load probability density curve and the strength probability density curve have overlapping interference areas, then the difference between the external load and the strength at different depths is used as a coupling characteristic value, so as to quantitatively calculate the failure risk value of the test string by using the coupling characteristic values ​​at different depths, wherein the test string risk value is quantitatively calculated by using the following expression:

[0014]

[0015]

[0016] μ z =μ S -μ L

[0017] Among them, F represents the failure risk probability, Z represents the coupling characteristic value, σ z represents the standard deviation of the coupling eigenvalue, σ L represents the standard deviation of the external load, σ S Indicates the standard deviation of intensity, μz represents the mean of the coupled eigenvalues, μ S represents the mean intensity, μ L Represents the mean external load.

[0018] Preferably, the embodiment of the present invention also provides a corresponding control scheme according to the failure risk value of the test string at different depths, combined with preset risk control rules and wellbore environmental temperature and pressure information.

[0019] Preferably, the risk control rules include but are not limited to: well control means aimed at changing gas production, using insulated oil pipes and well control means aimed at adjusting the casing annulus pressure. In the process of providing the control plan, the casing annulus pressure data at the well depth where the failure risk value exceeds the preset threshold is collected in real time. If the annulus pressure exceeds the preset pressure value, the corresponding well control means are used to adjust the gas production.

[0020] In addition, an embodiment of the present invention further provides a system for evaluating the failure risk of a test string, comprising: a data acquisition module, configured to obtain wellbore environmental temperature and pressure information about the test string to be evaluated; an uncertainty analysis module, configured to determine the external load of the test string and its corresponding string strength based on the wellbore environmental temperature and pressure information, thereby carrying out corresponding uncertainty analyses respectively; a risk assessment module, configured to perform a coupling characteristic analysis of the external load and strength based on the uncertainty analysis results of the external load and strength, thereby obtaining a test string failure risk value based on the external load characteristics and the strength characteristics.

[0021] Compared with the prior art, one or more embodiments of the above scheme may have the following advantages or beneficial effects:

[0022] The present invention proposes a method and system for evaluating the failure risk of a test string. The present invention fully considers the uncertainty of the external load of the test string and its corresponding string strength during the completion test in a deepwater, high-temperature, and high-pressure environment, conducts uncertainty analysis, and determines the failure risk value of the test string based on the coupling characteristics of the external load and strength. The present invention can clarify the failure risk status of the string at the current stage, and can also sort out the risk status that the string will face from the design stage. The application of the present invention can find out the failure risk points, and formulate corresponding risk control measures in a targeted manner, which can guide the design of high-temperature and high-pressure completion test operations, engineering risk monitoring and avoidance, reduce production costs, and provide reliable theoretical guarantees and technical guidance for the smooth progress of completion test operations.

[0023] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0025] Figure 1 Schematic diagram of the steps of a method for evaluating the failure risk of a test string according to an embodiment of the present application.

[0026] Figure 2 This is a schematic diagram of a specific process of a method for evaluating the failure risk of a test string according to an embodiment of the present application.

[0027] Figure 3 This is an example diagram of a wellbore structure in a scenario where the method for evaluating the risk of test string failure according to an embodiment of the present application is applied.

[0028] Figure 4 This is an example diagram of the wellbore environment temperature and pressure in the method for evaluating the failure risk of a test string in an embodiment of the present application.

[0029] Figure 5 This is an example diagram of the normal distribution probability density interference of external loads and corresponding strengths at different depths in the method for evaluating the failure risk of a test string according to an embodiment of the present application.

[0030] Figure 6 This is an example diagram of the first failure risk before regulation in the method for evaluating the failure risk of a test string in an embodiment of the present application.

[0031] Figure 7 This is an example diagram of the second failure risk before regulation in the method for evaluating the failure risk of a test string according to an embodiment of the present application.

[0032] Figure 8 This is an example diagram of failure risk after adjustment in the method for evaluating failure risk of a test string according to an embodiment of the present application.

[0033] Fig. 9 Schematic diagram of the structure of a system for evaluating the failure risk of a test string according to an embodiment of the present application. DETAILED DESCRIPTION

[0034] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other, and the technical solutions formed are all within the protection scope of the present invention.

[0035] In addition, the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions. Also, although a logical sequence is shown in the flowchart, in some cases, the steps shown or described can be performed in a sequence different from that here.

[0036] The terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms "one", "one" and "item" used herein are also intended to include plural numbers. It should also be understood that the terms "include" and / or "comprise" used herein specify the existence of stated features, integers, steps, operations, units and / or components, without excluding the existence or addition of one or more other features, integers, steps, operations, units, components and / or combinations thereof.

[0037] In order to solve one or more technical problems in the above-mentioned background technology, the present invention proposes a method and system for evaluating the failure risk of a test string. The present invention first performs a stress analysis on the test string, and then, on this basis, fully considers the uncertainty of the external load of the test string and its corresponding string strength during the completion test in a deepwater, high temperature and high pressure environment, conducts uncertainty analysis, and based on the coupling characteristics of the external load and strength, clarifies the quantitative failure risk value of the test string at the current stage, thereby providing reliable theoretical guarantee and technical guidance for the smooth progress of the completion test operation.

[0038] Embodiment 1

[0039] Figure 1 A schematic diagram of the steps of a method for evaluating the failure risk of a test string according to an embodiment of the present application. Figure 2 This is a schematic diagram of a specific process of the method for evaluating the failure risk of a test string according to an embodiment of the present application. Figure 1 and Figure 2 The method of this embodiment is described in detail.

[0040] Step S110: Obtaining wellbore environmental temperature and pressure information about the test string to be evaluated.

[0041] In one embodiment, the wellbore environmental temperature and pressure information includes but is not limited to: temperature distribution data of the test string, pressure distribution data in the test string, casing annulus temperature data, casing annulus pressure distribution data, wellbore ambient temperature distribution data and wellbore pressure and temperature distribution data.

[0042] Figure 3 This is an example diagram of a wellbore structure in the application scenario of the method for evaluating the failure risk of a test string in the embodiment of the present application. It should be noted that the test string failure risk evaluation method described in the embodiment of the present invention is applied to the high-temperature and high-pressure completion test string scenario of a deepwater gas well. Figure 3 As shown in the figure, the turntable surface is at sea level, the mud line is on the seabed, and the pipe string at the center of the part below the mud line is the test pipe string. The oil layer casing, technical casing and surface casing are wrapped from the inside to the outside with the test pipe string as the center. The packer is set between the test pipe string and the oil layer casing. The cement ring is located between the oil layer casing and the technical casing, and between the technical casing and the surface casing.

[0043] In a specific embodiment, the water depth of the deepwater high-temperature and high-pressure gas well is 1153.2 meters, and the conduit is lowered to 180 meters by jetting. Figure 3 As shown, the diameter of the surface casing is 20 inches and the depth is 1550 meters; the diameter of the technical casing is 13 3 / 8 inches, 2600 meters deep; the diameter of the oil layer casing is 9 5 / 8 The casing and test string have physical properties as shown in Table 1.

[0044] Table 1 Physical properties of casing and test string

[0045]

[0046] Figure 4 This is an example diagram of the wellbore environment temperature and pressure in the method for evaluating the failure risk of the test string in the embodiment of the present application. In the embodiment of the present invention, the sea surface temperature is 24.7°C, and the formation temperature gradient of the block is 0.039°C·m -1 The bottom hole pressure is 80.37MPa. The well is currently undergoing a three-day completion test with a gas production of 500,000 cubic meters. The wellbore temperature distribution from the mudline wellhead to the packer is as follows: Figure 4 As shown, the temperature and pressure in the test string at the packer are 145.74℃ and 79.42MPa, and the temperature and pressure in the casing annulus at the packer are 143.51℃ and 75.65MPa. The cross section of the string at a depth of 3100 meters was selected to observe the mechanical state. The temperature and pressure in the test string at this location are 143.3℃ and 78.1MPa, and the temperature and pressure in the casing annulus are 137.7℃ and 71.3MPa.

[0047] Step S120: Based on the wellbore environmental temperature and pressure information, determine the external load of the test string and its corresponding string strength, and based on this, carry out corresponding uncertainty analysis.

[0048] In an embodiment of calculating the external load of a test string, it is necessary to first calculate the (effective) external squeeze force and (effective) internal pressure of the test string at the current depth to be evaluated; then, by comparing the external squeeze force and internal pressure at the same depth, the external load of the test string is determined. Among them, if the external squeeze force is less than or equal to the internal pressure, the effective internal pressure at the current depth is used as the external load of the test string (that is, the external load of the test string at the current depth is in the form of the effective internal pressure); if the external squeeze force is greater than the internal pressure, the current effective external squeeze force is used as the external load of the test string (that is, the external load of the test string at the current depth is in the form of the effective external squeeze force). It should be noted that the external load data is the difference between the external squeeze force and the internal pressure.

[0049] In actual application, the completion test string is affected by high temperature and high pressure, and is subjected to internal pressure and external squeeze force. The internal pressure and external squeeze force at different depths will also change. Therefore, it is necessary to determine the effective external load form and the effective external load form at the corresponding depth to evaluate the uncertainty of the test string.

[0050] Therefore, the embodiment of the present invention also determines the strength of the pipe string at a corresponding depth according to the form of the external load of the test pipe string. Specifically, the external squeeze force and internal pressure borne by the test pipe string at the same depth are compared to determine the strength of the pipe string.

[0051] In one embodiment, if the external load at the current depth to be evaluated is in the form of effective internal pressure, the internal pressure resistance of the current test string is used as the string strength. In another embodiment, if the external load at the current depth to be evaluated is in the form of effective external squeezing force, the external squeezing resistance of the current test string is used as the string strength.

[0052] In this embodiment, the internal pressure resistance and external extrusion resistance of the test string in Table 1 are obtained, and the selection of string strength is determined according to the external load form. Among them, if the external load form borne by the test string at the current depth is effective internal pressure, the internal pressure resistance is selected as the string strength; if the external load form borne by the test string at the current depth is effective external extrusion force, the external extrusion resistance is selected as the string strength. Then, the embodiment of the present invention will also carry out uncertainty analysis of external load and string strength at corresponding depths according to the external load and string strength at different depths to be evaluated.

[0053] In one embodiment, the process of conducting uncertainty analysis of external load includes: determining the uncertainty of the external load through simulation analysis according to the external load of the test string at different depths, and obtaining a normal distribution probability density curve of the external load at the corresponding depth.

[0054] In another embodiment, the process of conducting the strength uncertainty analysis includes: determining the strength uncertainty through simulation analysis according to the strength of the test string at different depths, and obtaining a normal distribution probability density curve of the strength at the corresponding depth.

[0055] In this embodiment, based on the Monte Carlo simulation method, random sampling is used to simulate the well completion test experiment process, and the ANSYS simulation analysis software is used to perform uncertainty analysis on the external load and strength of the test string, thereby obtaining the probability distribution of the external load and the probability distribution of the strength of the test string. Among them, the string strength is analyzed and adjusted according to the error range of the size and other parameters provided by the manufacturer, thereby obtaining the normal distribution probability density curve of the external load and the normal distribution probability density curve of the strength at the current depth.

[0056] Step S130: According to the uncertainty analysis results of the external load and strength obtained in step S120, coupling characteristic analysis of the external load and strength is performed respectively, so as to obtain the failure risk value of the test string according to the external load characteristics and the strength characteristics.

[0057] In one embodiment, the process of obtaining the coupling characteristics of external load and strength includes: firstly drawing a probability density curve diagram of the normal distribution of external load and a probability density curve diagram of the normal distribution of strength respectively; then integrating the probability density curve diagram of the external load and the probability density curve diagram of the strength into the same coordinate system, and performing probability density interference state analysis on the current integrated coordinate system diagram, so as to determine the coupling characteristics of the external load and strength, and use the current coupling characteristics to perform quantitative value analysis of the test tube failure risk.

[0058] In the first embodiment of quantitatively analyzing the failure risk value of the test pipe string according to the coupling characteristics, if there is no overlapping interference area between the external load probability density curve and the strength probability density curve (that is, there is no overlapping interference area), and each strength distribution value in the curve diagram under the current same coordinate system is greater than or equal to the external load data, then it is determined that the risk value of the current test pipe string at the current depth is 0%.

[0059] In the second embodiment of quantitatively analyzing the failure risk value of the test pipe string according to the coupling characteristics, if there is no overlapping interference area between the external load probability density curve and the strength probability density curve (that is, there is no overlapping interference area), and each strength distribution value in the curve diagram under the current same coordinate system is less than the external load data, then it is determined that the risk value of the current test pipe string at the current depth is 100%.

[0060] In the third embodiment of quantitatively analyzing the risk value of test pipe failure based on coupling characteristics, if there is an overlapping interference area between the external load probability density curve and the strength probability density curve, the difference between the external load and the strength at different depths is used as the coupling characteristic value, so as to quantitatively calculate the risk value of test pipe failure using the coupling characteristic values ​​at different depths. The risk value of the test pipe string is quantitatively calculated using the following expression:

[0061]

[0062]

[0063] μ z =μ S -μ L (3)

[0064] Among them, F represents the failure risk probability, Z represents the coupling characteristic value, σ z represents the standard deviation of the coupling eigenvalue, σ L represents the standard deviation of the external load, σ S Indicates the standard deviation of intensity, μ z represents the mean of the coupled eigenvalues, μ S represents the mean intensity, μ L Represents the mean external load.

[0065] Figure 5 This is an example diagram of the normal distribution probability density interference of external loads and corresponding strengths at different depths in the method for evaluating the failure risk of a test string according to an embodiment of the present application. Figure 5 (a)-(d) show example graphs of the normal distribution probability density interference of external load under different depth conditions and the corresponding example graphs of the normal distribution probability density interference of intensity. Figure 5 (a) is an example diagram of the normal distribution probability density interference between the external load and strength of the test string at a well depth of 0 meters. Figure 5 (b) is an example diagram of the normal distribution probability density interference between the external load and strength of the test string at a depth of 500 meters. Figure 5 (c) is an example diagram of the normal distribution probability density interference between the external load and strength of the test string at a well depth of 1000 meters. Figure 5 (d) is an example of the interference between the external load and the normal distribution probability density of the strength of the test string at a depth of 2000 meters. Figure 5 As shown in (a)-(d), with the increase of well depth, the overlapping interference area between the external load probability density interference map and the intensity probability density interference map gradually decreases, and the distance between the interference areas gradually increases.

[0066] Figure 6 This is an example diagram of the first failure risk before regulation in the method for evaluating the failure risk of a test string in an embodiment of the present application. Figure 6 The quantitative failure risk value distribution diagram calculated according to the test string failure risk assessment method described in the embodiment of the present invention is shown. From the analysis, it can be seen that the risk position of the test string failure against internal pressure is from the wellhead to the well depth range of 1110 meters underground. At the wellhead, the test string failure risk is the highest, reaching 0.30%. As the well depth increases, the failure risk gradually decreases. Below 1110 meters in depth, the failure risk is less than 0.003%, and the failure risk can be ignored at this time.

[0067] In addition, the test string failure risk assessment method described in the embodiment of the present invention will also provide a corresponding control plan based on the failure risk value of the test string at different depths, combined with preset risk control rules and wellbore environmental temperature and pressure information.

[0068] In the embodiment of the present invention, the risk control rules include but are not limited to: well control means aimed at changing gas production, using insulated oil pipes and well control means aimed at adjusting the casing annulus pressure.

[0069] In one embodiment, the casing annulus pressure data at the well depth where the failure risk value exceeds the preset threshold is collected in real time. If the annulus pressure exceeds the preset pressure value in the screened casing annulus pressure data, the corresponding well control means are used to adjust the gas production.

[0070] In an example of a deepwater high-temperature and high-pressure gas well completion test process, the well water depth is 1476.5 meters, the actual drilling is 3810 meters, and the well depth structure is as follows Figure 3 As shown, the depth below the rotary table is 0 meters; the depth below the mudline is 1480 meters; the surface casing has a diameter of 20 inches, a wall thickness of 12.7 mm, and a depth of 2780 meters; the diameter of the technical casing is 13 3 / 8 inches, wall thickness 13.055 mm, depth 3580 meters; the diameter of the oil layer casing is 9 5 / 8 Inch, wall thickness 11.05 mm, depth 5290 m; packer setting depth 5110 m. Wellbore structure data are shown in Table 2, and the thermodynamic parameters of each structure in the well are shown in Table 3.

[0071] Table 2 Wellbore structure data

[0072]

[0073] Table 3 Thermodynamic parameters of various structures in the well

[0074]

[0075] During the operation, the area where the current well is located is in spring, the sea level ambient temperature is 25°C, the mud line wellhead ambient temperature is 2.9°C, and the geothermal gradient is 0.0434°C·m -1 The test string is equipped with a telescopic short section, with a maximum telescopic allowable length of 2 meters. A 48-hour completion test operation was performed with a gas production of 300,000 cubic meters. During the test, the bottom hole temperature was 168.33°C and the bottom hole pressure reached 73.86MPa. The failure risk value of the current test string at different depths is calculated by the method for evaluating the failure risk of the test string in this embodiment. Figure 7 .

[0076] like Figure 7 As shown in the figure, the failure risk value at the wellhead is the highest, at 3.49%. During the actual test, the test string showed signs of blockage, and during the cementing quality inspection at the end of the test, it was found that the cement ring seal failed, which further verified the accuracy of the risk assessment.

[0077] Furthermore, according to the failure risk value of the test string at the wellhead, combined with the pressure stabilization information of the wellbore environment and the preset risk control rules, the method of changing the gas production volume is selected to control the failure risk of the string. When the gas production volume is increased to 500,000 cubic meters, the annular pressure of the oil casing increases significantly, reaching 35.61MPa at the wellhead. Figure 8 This is an example diagram of the failure risk after adjustment in the method for evaluating the failure risk of a test string in an embodiment of the present application. Figure 8 As shown, the highest risk at the wellhead after regulation is less than 0.01%. It can be seen that the regulation effect of the method for evaluating the failure risk of the test string in this embodiment is significant.

[0078] Furthermore, the increase in gas production must not affect the engineering purpose of the completion test operation, and it is necessary to conduct appropriate regulation within the feasible range. In the process of providing the regulation plan, the oil casing annulus pressure data at the well depth position where the failure risk value exceeds the preset threshold is collected in real time. If the annulus pressure exceeds the preset pressure value, the corresponding well control means are used to adjust the gas production. Well control means include but are not limited to: changing the gas production, using insulated oil pipes, and adjusting the oil casing annulus pressure.

[0079] Embodiment 2

[0080] Based on the method for evaluating the failure risk of a test string described in the first embodiment, the present invention further provides a system for evaluating the failure risk of a test string. The system is used to implement the method for evaluating the failure risk of a test string described in the first embodiment.

[0081] Fig. 9 Schematic diagram of the structure of the system for evaluating the failure risk of the test string according to the embodiment of the present application. Fig. 9 As shown, the system described in the embodiment of the present invention includes: a data acquisition module 901, an uncertainty analysis module 902 and a risk assessment module 903.

[0082] Specifically, the data acquisition module 901 is implemented according to the method described in the above step S110, and is configured to obtain the wellbore environmental temperature and pressure information about the test string to be evaluated; the uncertainty analysis module 902 is implemented according to the method described in the above step S120, and is configured to determine the external load of the test string and its corresponding string strength based on the wellbore environmental temperature and pressure information, so as to carry out corresponding uncertainty analysis respectively; the risk assessment module 903 is implemented according to the method described in the above step S130, and is configured to perform a coupling characteristic analysis of the external load and strength according to the uncertainty analysis results of the external load and strength, so as to obtain the failure risk value of the test string according to the external load characteristics and strength characteristics.

[0083] The present invention proposes a method and system for evaluating the failure risk of a test string. The present invention fully considers the uncertainty of the external load of the test string and its corresponding string strength during the completion test in a deepwater, high-temperature and high-pressure environment, conducts uncertainty analysis, and determines the failure risk value of the test string based on the coupling characteristics of the external load and strength. The present invention can clarify the failure risk status of the string at the current stage, and can also sort out the risk status that the string will face from the design stage. The application of the present invention can find out the failure risk points, and formulate corresponding risk control measures in a targeted manner, which can guide the design of high-temperature and high-pressure completion test operations, engineering risk monitoring and avoidance, reduce production costs, and provide reliable theoretical guarantees and technical guidance for the smooth progress of completion test operations.

[0084] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person familiar with the technology within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

[0085] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0086] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0087] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should be extended to equivalent substitutions of these features understood by ordinary technicians in the relevant field. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments and are not meant to be limiting.

[0088] The "one embodiment" or "embodiment" mentioned in the specification means that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment.

[0089] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for evaluating the risk of failure of a test string, It is characterized in that include: Obtaining wellbore environmental temperature and pressure information about the test string to be evaluated; Based on the wellbore environmental temperature and pressure information, the external load of the test string and its corresponding string strength are determined, and based on this, corresponding uncertainty analysis is carried out respectively; According to the uncertainty analysis results of external load and strength, the coupling characteristic analysis of external load and strength is carried out, so as to obtain the failure risk value of the test string according to the external load characteristics and strength characteristics.

2. The method according to claim 1, It is characterized in that The wellbore environmental temperature and pressure information includes but is not limited to: temperature distribution data in the test string, pressure distribution data in the test string, casing annulus temperature distribution data, casing annulus pressure distribution data, wellbore surrounding environment temperature distribution data and wellbore pressure and temperature distribution data.

3. The method according to claim 1 or 2, It is characterized in that In the process of determining the external load, including: Calculate the external squeeze force and internal pressure of the test string at the depth to be evaluated; The external load is determined by comparing the external extrusion force and the internal pressure at the same depth. If the external extrusion force is less than or equal to the internal pressure, the effective internal pressure at the current depth is used as the external load. If the external extrusion force is greater than the internal pressure, the current effective external extrusion force is used as the external load.

4. The method according to claim 3, It is characterized in that The process of determining the strength of the pipe string includes: The corresponding pipe string strength is determined according to the form of the external load, wherein if the external load is in the form of effective internal pressure, the internal pressure resistance of the current tested pipe string is used as the pipe string strength; if the external load is in the form of effective external extrusion force, the external extrusion resistance of the current tested pipe string is used as the pipe string strength.

5. The method according to any one of claims 1 to 4, It is characterized in that The uncertainty analysis of external load and strength is carried out separately, including: According to the external load of the test string at different depths, the uncertainty of the external load is determined through simulation analysis, and a normal distribution probability density curve of the external load at the corresponding depth is obtained; According to the strength of the test string at different depths, the uncertainty of the strength is determined through simulation analysis, and a normal distribution probability density curve of the strength at the corresponding depth is obtained.

6. The method according to claim 5, It is characterized in that In the process of obtaining the coupled characteristic analysis of external load and strength, it includes: Draw a normal distribution probability density curve graph about the external load and a normal distribution probability density curve graph about the intensity respectively; The external load probability density curve and the intensity probability density curve are integrated into the same coordinate system and a probability density interference state analysis is performed to determine the coupling characteristics.

7. The method according to claim 6, It is characterized in that The process of calculating the failure risk value of the test string includes: If the external load probability density curve graph and the strength probability density curve graph have no overlapping interference area, and each strength distribution value in the curve graph under the current same coordinate system is greater than or equal to the external load data, it is determined that the risk value of the current test string at the current depth is 0%; If the external load probability density curve graph and the strength probability density curve graph have no overlapping interference area, and each strength distribution value in the curve graph under the current same coordinate system is smaller than the external load data, then the risk value of the current test string at the current depth is determined to be 100%; If there is an overlapping interference area between the external load probability density curve and the strength probability density curve, the difference between the external load and the strength at different depths is used as the coupling characteristic value, so as to quantitatively calculate the test pipe failure risk value by using the coupling characteristic values ​​at different depths, wherein the test pipe string risk value is quantitatively calculated by using the following expression: m z =μ S -m L Among them, F represents the failure risk probability, Z represents the coupling characteristic value, σ z represents the standard deviation of the coupling eigenvalue, σ L represents the standard deviation of the external load, σ S Indicates the standard deviation of intensity, μ z represents the mean of the coupled eigenvalues, μ S represents the mean intensity, μ L Represents the mean external load.

8. The method according to any one of claims 1 to 7, It is characterized in that The method further comprises: According to the failure risk values ​​of the test string at different depths, combined with the preset risk control rules and the wellbore environmental temperature and pressure information, a corresponding control plan is provided.

9. The method according to claim 8, It is characterized in that The risk control rules include but are not limited to: Well control means aimed at changing gas production, using insulated oil pipes and adjusting the casing annulus pressure. In the process of providing the control plan, the casing annulus pressure data at the well depth where the failure risk value exceeds the preset threshold is collected in real time. If the annulus pressure exceeds the preset pressure value, the corresponding well control means are used to adjust the gas production.

10. A system for evaluating the risk of failure of a test string, It is characterized in that include: A data acquisition module configured to acquire wellbore environmental temperature and pressure information about the test string to be evaluated; An uncertainty analysis module, configured to determine the external load of the test string and its corresponding string strength based on the wellbore environmental temperature and pressure information, thereby performing corresponding uncertainty analysis respectively; The risk assessment module is configured to perform coupling characteristic analysis of external load and strength according to the uncertainty analysis results of external load and strength, so as to obtain the failure risk value of the test string according to the external load characteristics and strength characteristics.

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