Risk evaluation method and system based on deepwater high-temperature and high-pressure well completion test

Abstract

The invention discloses a risk evaluation method and system based on deepwater high-temperature and high-pressure well completion testing. The method comprises the steps that shaft environment information is collected in real time, and shaft temperature and pressure distribution calculation is conducted on the shaft environment information; according to the shaft temperature and pressure distribution calculation result, feature calculation and risk prediction analysis are carried out for multi-dimensional risks of the shaft system, and the multi-dimensional risks include the hydrate generation risk, the test pipe column failure risk, the packer failure risk and the casing and cement sheath failure risk. Theoretical support and technical support can be provided for operation design, engineering risk monitoring and avoiding of deepwater high-temperature and high-pressure well completion testing.

Description

Technical Field

[0001] The present invention relates to the technical field of deepwater gas well completion testing, and in particular to a risk assessment method and system based on deepwater high-temperature and high-pressure completion testing. 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. Deepwater high-temperature and high-pressure completion testing technology is one of the key links in the development of deepwater high-temperature and high-pressure gas reservoirs. Due to its special temperature and pressure environment, it has far more difficulty, cost and risk than land and shallow water completion testing. In deepwater high-temperature and high-pressure completion testing operations, high-temperature and high-pressure produced gas flows upward along the completion test string, which will cause intense radial heat transfer, resulting in significant changes in the temperature and pressure distribution of the wellbore, especially in the unsealed annulus of the wellbore. There will be a higher annular accumulation pressure. When the produced gas flows up to the seawater section, the radial heat transfer is more intense due to the low temperature of the seabed. In addition, the flowing pressure of the produced gas is reduced, and the overall high-pressure distribution in the string is maintained, thus forming a relatively "low-temperature and high-pressure state", promoting the formation of hydrates, and thus increasing the risk of clogging the completion test string. Once the above-mentioned risk accidents occur during the operation, the completion test process will be affected at the least, resulting in the failure of the operation, and at the worst, it will cause significant casualties, environmental damage and economic losses.

[0003] At present, most of the related technologies at home and abroad are qualitative analysis of the risks of completion test operations, and there is no relevant research on quantitative evaluation. In addition, the work on risk control is also based on the pipeline perspective, and then reasonable suggestions are put forward. Existing technical research can only provide theoretical reference for field operations, but cannot provide an operational technical support.

[0004] It can be seen from this that the existing technology needs to establish a set of deepwater high-temperature and high-pressure completion test risk assessment methods to provide theoretical and technical support for the operation design, engineering risk monitoring and avoidance of deepwater high-temperature and high-pressure completion tests. Summary of the invention

[0005] The present invention aims to provide a risk assessment scheme based on deepwater high temperature and high pressure completion testing, so as to provide reliable theoretical guarantee and technical guidance for the smooth implementation of deepwater high temperature and high pressure completion testing operations.

[0006] In order to solve the above technical problems, an embodiment of the present invention provides a risk assessment method based on deepwater high-temperature and high-pressure completion testing, including: real-time collection of wellbore environmental information, and calculation of the wellbore temperature and pressure distribution of the wellbore environmental information; based on the calculation results of the wellbore temperature and pressure distribution, characteristic calculation and risk prediction analysis are carried out for the multi-dimensional risks of the wellbore system, and the multi-dimensional risks include: hydrate formation risk, test string failure risk, packer failure risk, and casing and cement ring failure risk.

[0007] Preferably, in the step of collecting wellbore environmental information in real time and calculating the wellbore temperature and pressure distribution of the wellbore environmental information, it includes: calculating the temperature and pressure distribution of the wellbore system according to the wellbore environmental information, based on which, respectively calculating the temperature and pressure distribution in the completion test string of the seawater section, the temperature and pressure distribution in the annulus of the formation section, and the temperature and pressure distribution in the completion test string of the formation section, the wellbore environmental information includes but is not limited to: seawater temperature, water depth, wellbore structure data, elastic-plastic mechanical parameters and thermodynamic parameters of the string and cement ring, the flow state of the liquid in the well, the properties and thermodynamic parameters of the liquid in the well, the formation temperature data, and the reservoir temperature and pressure data.

[0008] Preferably, the process of carrying out characteristic calculation for the risk of hydrate formation includes: constructing a hydrate phase equilibrium temperature curve representing the critical temperature of hydrate formation at different depths according to the temperature and pressure distribution in the completion test string of the seawater well section and the temperature and pressure distribution in the annulus of the formation well section; and predicting the hydrate formation area based on the hydrate phase equilibrium temperature curve, wherein if the temperature in the test string is lower than the phase equilibrium temperature, there is a risk of hydrate formation in the depth area.

[0009] Preferably, in the process of carrying out characteristic calculation for the risk of test string failure, it includes: calculating the first external load information characterizing the stress condition of the test string based on the temperature and pressure distribution in the annulus of the formation section and the temperature and pressure distribution in the completion test string of the formation section, and then drawing a first curve graph of the normal distribution probability density characterizing the external load and strength of the string in combination with the strength of the test string.

[0010] Preferably, in the process of carrying out characteristic calculation for the risk of failure of the packer, it includes: calculating the axial force of the completion test string borne by the packer based on the length of the tubing above the packer in the formation well section, the elastic-plastic mechanical parameters of the tubing, the thermodynamic parameters of the tubing, the reservoir temperature and pressure data, and the formation temperature and pressure data; calculating the pressure borne by the lower surface of the packer based on the axial force of the completion test string borne by the packer, combined with the temperature and pressure distribution in the tubing in the formation well section, and calculating the pressure exerted by the annulus liquid on the upper surface of the packer in combination with the annulus temperature and pressure distribution in the formation well section; determining the difference between the pressure borne by the lower surface of the packer and the pressure exerted by the annulus liquid on the upper surface of the packer as the packer annulus pressure difference.

[0011] Preferably, in the process of carrying out characteristic calculation for the failure risk of casing and cement sheath, it includes: calculating the second external load information and corresponding strength information characterizing the stress condition of the casing according to the wellbore structure data, the elastoplastic mechanical parameters and thermodynamic parameters of the casing and cement sheath, the flow state of the liquid in the well, the properties and thermodynamic parameters of the liquid in the well, the formation temperature data and the reservoir temperature and pressure data, based on which, drawing a second curve graph of the normal distribution probability density characterizing the external load and strength of the casing, and calculating the third external load information and corresponding strength information characterizing the stress condition of the cement sheath, based on which, drawing a third curve graph of the normal distribution probability density characterizing the external load and strength of the cement sheath.

[0012] Preferably, in the process of conducting risk analysis on hydrate formation risk, the process includes: based on the predicted hydrate formation area, in combination with the string temperature distribution and the hydrate phase equilibrium temperature, determining the hydrate formation range and calculating the dimensionless undercooling coefficient characterizing the hydrate formation risk degree, thereby applying the dimensionless undercooling coefficient to determine the hydrate formation risk distribution within the current hydrate formation range, wherein the dimensionless undercooling coefficient is calculated using the following expression:

[0013]

[0014] Among them, F R Represents dimensionless undercooling coefficient, dimensionless; C d represents the degree of supercooling, in °C; T represents the phase equilibrium temperature, in °C; T i It indicates the actual temperature in the column, in °C; z indicates the hydrate depth, in m.

[0015] Preferably, the process of conducting risk analysis on the test string failure risk includes: applying generalized stress intensity interference theory to perform interference analysis on the first curve graph to quantitatively evaluate the completion test string failure risk value.

[0016] Preferably, in the process of conducting risk analysis on the risk of packer failure, it includes: judging whether the current packer has a risk of failure based on the axial force of the completion test string borne by the packer and the annulus pressure difference of the packer using a preset packer envelope curve, wherein if the coupling position point between the axial force of the completion test string borne by the packer and the annulus pressure difference of the packer is within the range of the packer envelope curve, then the current packer does not have a risk of failure, and the packer envelope curve is a safe closed-loop boundary curve formed by coupling the safe range of the axial force of the tubing borne by the packer and the safe range of the annulus pressure difference.

[0017] Preferably, in the process of conducting risk analysis on the risks of casing and cement sheath failure, it includes: applying the generalized stress intensity interference theory to perform interference analysis on the second curve graph to quantitatively evaluate the casing failure risk value; applying the generalized stress intensity interference theory to perform interference analysis on the third curve graph to quantitatively evaluate the cement sheath failure risk value.

[0018] Preferably, the failure risk assessment method further includes: integrating the risk prediction analysis results of multi-dimensional risks, conducting analysis of the main influencing factors of failure risk, and providing corresponding risk control solutions for the main influencing factors of risk.

[0019] In addition, an embodiment of the present invention also provides a system for risk assessment based on deepwater high-temperature and high-pressure completion testing, including: a data acquisition and parameter analysis module, which is configured to acquire wellbore environmental information in real time and calculate the wellbore temperature and pressure distribution of the wellbore environmental information; a risk feature calculation and evaluation module, which is configured to perform feature calculation and risk prediction analysis for multi-dimensional risks of the wellbore system based on the wellbore temperature and pressure distribution calculation results, and the multi-dimensional risks include: hydrate formation risk, test string failure risk, packer failure risk, and casing and cement ring failure risk.

[0020] Compared with the prior art, one or more embodiments of the above scheme may have the following advantages or beneficial effects:

[0021] The present invention proposes a risk assessment method and system based on deepwater high-temperature and high-pressure completion testing. The present invention fully considers the multi-dimensional failure risks of the wellbore system caused by different wellbore environments during the completion testing process in a deepwater high-temperature and high-pressure environment, and studies the hydrate formation risk, the test string failure risk, the packer failure risk, the casing reliability failure risk, and the cement ring sealing integrity failure risk to evaluate the risk status of deepwater high-temperature and high-pressure completion testing operations. On this basis, high-risk points are found according to the evaluation results to formulate corresponding risk influencing factor control plans, and the control effects are calculated and analyzed. The present invention can effectively prevent accidents and reduce losses, and provide reliable theoretical guarantees and technical guidance for the smooth progress of completion testing operations.

[0022] In addition, the present invention can clarify the current risk status of deepwater high-temperature and high-pressure completion and testing operations, and can also sort out the risk status that the operation will face from the design stage. The application of the present invention can find out the main risk points and formulate corresponding risk control measures in a targeted manner, which can guide the design of deepwater high-temperature and high-pressure completion and testing operations, engineering risk monitoring and avoidance, reduce production costs, and provide reliable theoretical guarantees and technical guidance for the smooth progress of deepwater high-temperature and high-pressure completion and testing 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 This is a schematic diagram of the steps of a risk assessment method based on deepwater high-temperature and high-pressure completion testing according to an embodiment of the present application.

[0026] Figure 2 This is a schematic diagram of a specific process of a risk assessment method based on deepwater high-temperature and high-pressure completion testing according to an embodiment of the present application.

[0027] Figure 3 This is an example diagram of the wellbore structure in the application scenario of the risk assessment method based on deepwater high temperature and high pressure completion testing in an embodiment of the present application.

[0028] Figure 4 This is an example diagram of the analysis and evaluation of the hydrate formation risk before regulation of the risk assessment method based on deepwater high temperature and high pressure completion testing in an embodiment of the present application.

[0029] Figure 5 This is an example diagram of the analysis and evaluation of the risk of packer failure based on the risk assessment method for deepwater high-temperature and high-pressure completion testing in an embodiment of the present application.

[0030] Figure 6 This is an example diagram of the analysis and evaluation of the failure risk of the test string before adjustment based on the risk assessment method for deepwater high-temperature and high-pressure completion testing in an embodiment of the present application.

[0031] Figure 7 This is an example diagram of the analysis and evaluation of the failure risk of the oil layer casing based on the risk assessment method of deepwater high temperature and high pressure completion testing in an embodiment of the present application.

[0032] Figure 8 This is an example diagram of the analysis and evaluation of failure risks of cement sheath before and after improvement based on the risk assessment method for deepwater high temperature and high pressure completion testing in an embodiment of the present application.

[0033] Fig. 9 This is an example diagram of the analysis and evaluation of the hydrate formation risk after regulation according to the risk assessment method based on deepwater high temperature and high pressure completion testing in an embodiment of the present application.

[0034] Fig.10This is an example diagram of the analysis and evaluation of the failure risk after the test string is adjusted according to the risk assessment method based on deepwater high temperature and high pressure completion testing in an embodiment of the present application.

[0035] Fig.11 This is a schematic diagram of the structure of a risk assessment system based on deepwater high-temperature and high-pressure completion testing according to an embodiment of the present application. DETAILED DESCRIPTION

[0036] 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.

[0037] 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.

[0038] 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.

[0039] Deepwater high-temperature and high-pressure completion testing technology is one of the key links in the development of deepwater high-temperature and high-pressure gas reservoirs. Due to its special temperature and pressure environment, it has far more difficulty, cost and risk than onshore and shallow water completion testing. In deepwater high-temperature and high-pressure completion testing operations, high-temperature and high-pressure produced gas will undergo intense radial heat transfer when flowing upward along the completion test string, resulting in significant changes in the temperature and pressure distribution of the wellbore, especially in the unsealed annulus of the wellbore, where a higher annulus accumulation pressure will occur. When the produced gas flows up to the seawater well section, the radial heat transfer becomes more intense due to the low temperature on the seabed. In addition, the flowing pressure of the produced gas decreases, and the overall high-pressure distribution in the string is maintained, thus forming a relatively "low-temperature and high-pressure state", promoting the formation of hydrates, and thus increasing the risk of clogging the completion test string. Once the above-mentioned risk accidents occur during the operation, the completion test process will be affected at the least, resulting in the failure of the operation, and at the worst, it will cause significant casualties, environmental damage and economic losses.

[0040] In order to solve the above problems, the present invention proposes a risk assessment method and system based on deepwater high-temperature and high-pressure completion testing. The present invention studies the risk of hydrate formation, the risk of test string failure, the risk of packer failure, the risk of casing reliability failure, and the risk of cement ring sealing integrity failure, and evaluates the risk status of deepwater high-temperature and high-pressure completion testing operations. On this basis, according to the evaluation results, high-risk points are found to formulate corresponding risk influencing factor control plans, and the control effects are calculated and analyzed, thereby providing reliable theoretical guarantees and technical guidance for the smooth progress of completion testing operations.

[0041] Embodiment 1

[0042] Figure 1 This is a schematic diagram of the steps of a risk assessment method based on deepwater high-temperature and high-pressure completion testing according to an embodiment of the present application. Figure 2 This is a specific flow chart of the risk assessment method based on deepwater high temperature and high pressure completion testing in the embodiment of the present application. Figure 1 and Figure 2 The method of this embodiment is described in detail.

[0043] Step S110, collecting wellbore environmental information in real time, and calculating the wellbore temperature and pressure distribution of the wellbore environmental information.

[0044] In one embodiment, the temperature and pressure distribution of the wellbore system must first be calculated based on the wellbore environmental information; then, based on the obtained temperature distribution and pressure distribution characteristics of the wellbore system, the temperature and pressure distribution in the seawater well section completion test string, the temperature and pressure distribution in the formation well section annulus, and the temperature and pressure distribution in the formation well section completion test string are calculated respectively.

[0045] In an embodiment of the present invention, the wellbore environmental information includes but is not limited to: seawater temperature, water depth, wellbore structure data, elastic-plastic mechanical parameters and thermodynamic parameters of the tubing and cement ring, well liquid flow state, well liquid properties and thermodynamic parameters, formation temperature data and reservoir temperature and pressure data, etc.

[0046] Figure 3 This is an example diagram of the wellbore structure in the application scenario of the risk assessment method based on deepwater high-temperature and high-pressure completion testing in the embodiment of the present application. It should be noted that the risk assessment method described in the embodiment of the present invention is applied to the high-temperature and high-pressure completion testing scenario of deepwater gas wells. 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.

[0047] In a specific embodiment A, the gas well is located in deep water, the water depth of the deep water high temperature and high pressure gas well is 1476.5 meters, the actual drilling is 3810 meters, the wellbore structure and characteristic parameters are as follows Figure 3 As shown in Table 1. The diameter of the surface casing is 20 inches, the wall thickness is 12.7 mm, and the depth is 2780 meters; the diameter of the technical casing is 13 3 / 8 inches, wall thickness 13.055 mm, down to 3580 meters; the diameter of the oil layer casing is 9 5 / 8 inches, with a wall thickness of 11.05 mm and a depth of 5290 meters; the packer is sealed at a depth of 5110 meters below the mud line.

[0048] Table 1 Wellbore structural characteristic parameters

[0049] structure Inner diameter / m Outer diameter / m structure Inner diameter / m Outer diameter / m Test string 0.1257 0.1397 Riser 0.4826 0.5334 Surface casing 0.4826 0.508 One cement ring 0.508 0.6604 Technical casing 0.31361 0.33972 Two-open cement ring 0.3397 0.4758 Oil layer casing 0.22238 0.24448 Three-open cement ring 0.245 0.315

[0050] During the completion test, the gas well was located in the spring, with a sea level of 25°C, a seabed mudline wellhead of 2.9°C, and a geothermal gradient of 0.0434°C·m -1 The elastic-plastic mechanical and thermodynamic parameters of each wellbore structure are shown in Tables 2 and 3.

[0051] Table 2 Elastic-plastic mechanical parameters of various wellbore structures

[0052] structure Numeric structure Numeric Casing elastic modulus / GPa 206 Casing Poisson's ratio 0.3 Completion test string elastic modulus / GPa 206 Completion test string Poisson's ratio 0.3 Cement sheath elastic modulus / GPa 6 Poisson's ratio of cement sheath 0.22 Formation elastic modulus / GPa 45 Formation Poisson's ratio 0.3 Cement sheath compressive strength / MPa 57.14 Cement sheath tensile strength / MPa 8.72

[0053] Table 3 Thermodynamic parameters of various wellbore structures

[0054]

[0055]

[0056] Furthermore, a telescopic short joint is installed on the current well test string, and the maximum telescopic allowance is 2 meters. According to the above wellbore environmental information, the bottom hole temperature is calculated to be 168.33℃, and the bottom hole pressure reaches 73.86MPa. Based on this, the temperature and pressure distribution in the completion test string of the seawater section, the temperature and pressure distribution in the annulus of the formation section, and the temperature and pressure distribution in the completion test string of the formation section are calculated respectively.

[0057] Step S120: Based on the calculation results of the wellbore temperature and pressure distribution, characteristic calculation and risk prediction analysis are performed for the multi-dimensional risks of the wellbore system. In the embodiment of the present invention, the multi-dimensional risks include but are not limited to: hydrate formation risk, test string failure risk, packer failure risk, and casing and cement sheath failure risk.

[0058] In an embodiment of characteristic calculation for predicting the risk of hydrate formation, first, a hydrate phase equilibrium temperature curve is constructed based on the temperature and pressure distribution in the completion test string of the seawater section and the temperature and pressure distribution in the annulus of the formation section. The hydrate phase equilibrium temperature curve is used to characterize the critical temperature of hydrate formation at different depths. Then, based on the constructed hydrate phase equilibrium temperature curve and the temperature distribution characteristics in the test string, the hydrate formation area is predicted. Among them, if the temperature in the test string is lower than the phase equilibrium temperature at the corresponding depth, there is a risk of hydrate formation in the depth area.

[0059] Further, in an embodiment of risk analysis and evaluation for predicting hydrate formation risk, based on the predicted hydrate formation area, combined with the temperature distribution characteristics of the pipe string and the hydrate phase equilibrium temperature distribution characteristics (i.e., the hydrate phase equilibrium temperature curve), the hydrate formation range is determined, and the dimensionless supercooling coefficient characterizing the degree of hydrate formation risk is calculated, so as to determine the hydrate formation risk distribution within the current hydrate formation range using the current dimensionless supercooling coefficient. The dimensionless supercooling coefficient is calculated using the following expression:

[0060]

[0061] Among them, F R Represents dimensionless undercooling coefficient, dimensionless; C d represents the degree of supercooling, in °C; T represents the phase equilibrium temperature, in °C; T i It indicates the actual temperature in the column, in °C; z indicates the hydrate depth, in m.

[0062] Figure 4 This is an example diagram of the analysis and evaluation of the hydrate formation risk before regulation of the risk assessment method based on deepwater high temperature and high pressure completion testing in an embodiment of the present application. Figure 4 The hydrate formation risk distribution diagram obtained by the risk analysis and evaluation carried out according to the risk evaluation method described in the embodiment of the present invention is shown. In this embodiment, the hydrate phase equilibrium curve is constructed based on the temperature and pressure distribution in the completion test string of the seawater section and the temperature and pressure distribution in the annulus of the formation section. Combined with the temperature distribution in the completion test string, the hydrate formation range is determined. Figure 4 As shown, in the above-mentioned embodiment A, within the well depth range from the wellhead to 1000 meters underground, the temperature in the completion test string is lower than the hydrate phase equilibrium temperature. Therefore, there is a risk of hydrate formation in this depth area.

[0063] Further, the hydrate formation risk distribution within the current hydrate formation range is determined. In the above embodiment A, the dimensionless supercooling coefficient is calculated by formula (1) to further determine the hydrate formation risk degree. The hydrate formation risk distribution diagram is shown in FIG. Figure 4As shown in the figure, the hydrate formation area is from the wellhead to the depth of 1,000 meters underground. The hydrate formation risk is highest at 300 meters from the wellhead, reaching 82.14%. During the actual test, the test string showed signs of blockage, which further verified the accuracy of the risk assessment.

[0064] In an embodiment of characteristic calculation for the risk of failure of a packer, first, the axial force of the completion test string borne by the packer is calculated based on the length of the tubing above the packer in the formation well section, the elastic-plastic mechanical parameters of the tubing, the thermodynamic parameters of the tubing, the reservoir temperature and pressure data, and the formation temperature and pressure data; then, based on the axial force of the completion test string borne by the packer, combined with the temperature and pressure distribution in the tubing of the formation well section, the pressure borne by the lower surface of the packer is calculated; at the same time, based on the axial force of the completion test string borne by the packer, combined with the temperature and pressure distribution in the annulus of the formation well section, the pressure exerted by the annulus liquid on the upper surface of the packer is calculated; finally, the difference between the pressure borne by the lower surface of the packer and the pressure exerted by the annulus liquid on the upper surface of the packer is determined as the packer annulus pressure difference, so that the current packer annulus pressure difference is used as the characteristic calculation result of the risk of failure of the packer.

[0065] In actual application, the packer is used as a separation tool to separate the test layer from the drilling fluid and other layers, and prevent the interference of interlayer fluid and pressure. During the completion test, the packer is subjected to various forces, including: the contact position between the packer and the test string is subjected to the axial force of the completion test string; the upper surface of the packer is subjected to the pressure exerted by the annular fluid; the lower surface of the packer is subjected to the pressure exerted by the formation well section string. Among them, the difference between the pressure exerted on the lower surface of the packer and the pressure exerted by the annular fluid on the upper surface of the packer is taken as the packer annular pressure difference.

[0066] Furthermore, in an embodiment of risk analysis and evaluation for the risk of packer failure, it is determined whether the current packer has a risk of failure based on the axial force of the completion test string borne by the packer and the annular pressure difference of the packer, combined with the preset packer envelope curve. Among them, if the coupling position point between the axial force of the completion test string borne by the packer and the annular pressure difference of the packer is within the range of the packer envelope curve, then the current packer does not have a risk of failure. In the embodiment of the present invention, the packer envelope curve is a safety closed-loop boundary curve formed by coupling the safety range of the axial force of the string borne by the packer and the safety range of the annular pressure difference.

[0067] In this embodiment, the packer envelope curve is a fixed parameter of the packer, which is used to characterize the ultimate bearing boundary that the packer can withstand under the combined influence of the axial force of the tubing string and the annular pressure difference. The packer envelope curve is provided by the manufacturer and accurately describes the safe operating area of ​​the packer by comprehensively utilizing computer simulation models, finite element analysis, numerical simulation, laboratory experiments, oil field field experiments and other technologies and parameters. The reliability of the packer can be effectively evaluated based on the envelope curve.

[0068] Figure 5 This is an example diagram of the analysis and evaluation of the risk of failure of the packer based on the risk assessment method of deepwater high temperature and high pressure completion test in the embodiment of the present application. In this embodiment, according to the risk assessment method based on deepwater high temperature and high pressure completion test described in the embodiment of the present invention, the calculated upward annular pressure difference of the packer in Example A is 11.96MPa, and the axial force of the string is 0MPa. Figure 5 As shown, the coupling position point where the packer withstands the axial force of the completion test string and the packer annulus pressure difference is located within the range of the packer envelope curve. Therefore, for Example A, there is no risk of failure of the packer under the current environment.

[0069] In an embodiment for performing characteristic calculation for the risk of test string failure, first external load information characterizing the stress condition of the test string is calculated based on the temperature and pressure distribution in the annulus of the formation section and the temperature and pressure distribution in the test string of the formation section completion. Then, based on the first external load information and in combination with the strength of the test string, a first curve graph characterizing the normal distribution probability density of the string external load and strength is drawn, so that the current first curve graph is used as the characteristic calculation result of the risk of test string failure.

[0070] In the actual application process, the test string is subjected to the effects of internal pressure and external squeezing force at the same time. It is necessary to first calculate the (effective) external squeezing force and (effective) internal pressure of the test string at the current depth to be evaluated; then, by comparing the external squeezing force and internal pressure at the same depth, the external load of the test string is determined. Among them, 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 of the test string (that is, the external load form of the test string at the current depth is internal pressure); if the external squeezing force is greater than the internal pressure, the current effective external squeezing force is used as the external load of the test string (that is, the external load form of the test string at the current depth is external squeezing force). It should be noted that the first external load information is the difference between the external squeezing force and the internal pressure. Then, according to the form of the external load of the test string, the strength of the string at the corresponding depth is determined. If the external load form at the current depth to be evaluated is internal pressure, the internal pressure resistance strength of the current test string is used as the string strength. If the external load form at the current depth to be evaluated is external squeezing force, the external squeezing resistance strength of the current test string is used as the string strength. Furthermore, in combination with the first external load information and strength of the test string, a first curve graph of normal distribution probability density characterizing the external load and strength of the string is drawn.

[0071] In this embodiment, based on the Monte Carlo simulation method, a random sampling method is used to simulate the well logging and completion test experimental process, and the ANSYS simulation analysis software is used to perform uncertainty analysis on the external load and strength of the test string, and the external load probability density interference diagram and the strength probability density interference diagram of the test string are drawn respectively. Then, the external load probability density interference diagram and the strength probability density interference diagram are integrated into the same coordinate system to draw the first curve diagram of the normal distribution probability density representing the external load and strength of the string.

[0072] Furthermore, in a process of conducting risk analysis and evaluation on the failure risk of the test string, the generalized stress intensity interference theory is applied to perform interference analysis on the first curve, thereby quantitatively evaluating the failure risk value of the completion test string.

[0073] In this embodiment, a coupling characteristic analysis is performed on the external load and strength of the test string in the first curve based on the generalized stress intensity interference theory, and then a quantitative analysis is performed on the failure risk value of the test string.

[0074] In the first embodiment of quantitatively analyzing the failure risk value of the test pipe string based on the coupling characteristics, if there is no overlapping interference area between the external load probability density interference diagram and the intensity probability density interference diagram (that is, there is no overlapping interference area), and each intensity distribution value in the interference diagram is greater than or equal to the external load data, then the risk value of the current test pipe string at the current depth is determined to be 0.

[0075] In the second embodiment of quantitatively analyzing the failure risk value of the test pipe string based on the coupling characteristics, if there is no overlapping interference area between the external load probability density interference diagram and the intensity probability density interference diagram (i.e., there is no overlapping interference area), and each intensity distribution value in the interference diagram is smaller than the external load data, then it is determined that the risk value of the current test pipe string at the current depth is full marks.

[0076] In the third embodiment of quantitatively analyzing the test string failure risk value based on the coupling characteristics, if there is an overlapping interference area between the external load probability density interference diagram and the strength probability density interference diagram, 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 string failure risk value using the coupling characteristic values ​​at different depths. The test string risk value is quantitatively calculated using the following expression:

[0077]

[0078]

[0079] μ z =μ S -μ L (4)

[0080] Where F represents the failure risk probability of the test tube, Z represents the coupling characteristic value in the first curve, σ z represents the standard deviation of the coupling eigenvalues ​​in the first curve, σ L represents the standard deviation of the external load in the first curve, σ S represents the standard deviation of the intensity in the first curve, μ z represents the mean of the coupling eigenvalues ​​in the first curve, μ S represents the mean intensity in the first curve, μ L represents the mean external load in the first curve.

[0081] Figure 6 This is an example diagram of the analysis and evaluation of the failure risk of the test string before adjustment based on the risk assessment method for deepwater high-temperature and high-pressure completion testing in an embodiment of the present application. Figure 6 The distribution diagram of the quantitative failure risk value of the test string obtained by the risk analysis and evaluation carried out according to the risk evaluation method described in the embodiment of the present invention is shown. It can be seen from the analysis that during the completion test, the test string has the risk of failure due to internal pressure resistance, and the highest risk position is at the wellhead, where the pressure inside the string and the casing annulus pressure are 65.81MPa and 26.75MPa respectively, and the risk value reaches 3.49%. In actual operation, the completion test string at the wellhead has slight deformation, which further verifies the accuracy of the risk assessment.

[0082] In an embodiment of conducting risk analysis and evaluation for the risk of casing and cement sheath failure, second external load information and corresponding strength information characterizing the stress condition of the casing are calculated based on wellbore structure data, elastic-plastic mechanical parameters and thermodynamic parameters of the casing and cement sheath, the flow state of the liquid in the well, the properties and thermodynamic parameters of the liquid in the well, formation temperature data and reservoir temperature and pressure data, and a second curve graph of the normal distribution probability density characterizing the external load and strength of the casing is drawn based on the second external load information and the corresponding strength information; at the same time, third external load information and corresponding strength information characterizing the stress condition of the cement sheath are calculated, and a third curve graph of the normal distribution probability density characterizing the external load and strength of the cement sheath is drawn based on the third external load information and the corresponding strength information.

[0083] Furthermore, in the process of conducting risk analysis and evaluation on the failure risks of casing and cement sheath, the generalized stress intensity interference theory is applied to perform interference analysis on the second curve and the third curve respectively, and the failure risk values ​​of casing and cement sheath are quantitatively evaluated.

[0084] In an embodiment of the present invention, the characteristic calculation process and risk analysis and evaluation process for calculating the casing failure risk are similar to the characteristic calculation process and risk analysis and evaluation process for the test string failure risk. Similarly, the characteristic calculation process and risk analysis and evaluation process for the cement sheath failure risk are also similar to the characteristic calculation process and risk analysis and evaluation process for the test string failure risk, so they will not be repeated here.

[0085] Figure 7 This is an example diagram of the analysis and evaluation of the failure risk of the oil layer casing based on the risk assessment method of deepwater high temperature and high pressure completion testing in an embodiment of the present application. Figure 7 The distribution diagram of the quantitative failure risk value of the oil layer casing obtained by the risk analysis and evaluation carried out according to the risk evaluation method described in the embodiment of the present invention is shown. It can be seen from the analysis that during the completion test, based on the above embodiment A, the oil layer casing is subjected to external squeezing force within the well depth range of 0 to 2100 meters, and is subjected to internal pressure below 2100 meters. Figure 7 As shown, there is no risk of failure of the oil layer casing during the completion test.

[0086] Figure 8 This is an example diagram of the analysis and evaluation of failure risks of cement sheath before and after improvement based on the risk assessment method for deepwater high temperature and high pressure completion testing in an embodiment of the present application. Figure 8 The distribution diagram of the quantitative failure risk value of cement sheath obtained by the risk analysis and evaluation carried out according to the risk evaluation method described in the embodiment of the present invention is shown. It can be seen from the analysis that based on the above-mentioned embodiment A, the external load of the cement sheath is in the form of pressure and tension. In the current completion test process, the cement sheath has a tensile failure risk in the well section of 2100 meters to 3630 meters, and the tensile failure risk value range is 72.27% to 99.98%. In the actual test process, the cement sheath body undergoes tensile failure and then produces radial cracks, which further verifies the accuracy of the risk assessment of this embodiment.

[0087] In addition, the failure risk assessment method described in the embodiment of the present invention will also integrate the risk prediction analysis results of multiple dimensions (for example, the above four risk dimensions), conduct analysis on the main influencing factors of failure risk, and provide corresponding risk control solutions for the main influencing factors of risk.

[0088] In the embodiment of the hydrate formation risk dimension in the above embodiment A, the hydrate formation risk is high in the well depth range from the mudline to 1000 meters underground. Based on the multi-dimensional risk prediction analysis results, the insulated oil pipe technology is selected for risk control, and the thermal conductivity of the oil pipe is less than 0.15W·m -1 ℃ -1 . Fig. 9 This is an example diagram of the analysis and evaluation of the hydrate formation risk after regulation according to the risk assessment method based on deepwater high temperature and high pressure completion testing in an embodiment of the present application. Fig. 9 The risk distribution diagram of hydrate formation after adjustment obtained by risk analysis and evaluation according to the risk evaluation method described in the embodiment of the present invention is shown. From the analysis, it can be seen that in Example A, the adjusted hydrate formation risk can be ignored. It can be seen that the risk evaluation method based on deepwater high temperature and high pressure completion test in this embodiment has a significant control effect.

[0089] In the embodiment of the test string failure risk dimension in the above embodiment A, the test string has the risk of failure against internal pressure at the wellhead, and the risk value reaches 3.49%. Based on the multi-dimensional risk prediction analysis results, the target well is regulated by changing the well control means of gas production, and the gas production is increased to 500,000 cubic meters. Fig.10 This is an example diagram of the analysis and evaluation of the failure risk after the test string is adjusted according to the risk assessment method based on deepwater high temperature and high pressure completion testing in an embodiment of the present application. Fig.10 The risk distribution diagram of the test string obtained by the risk analysis and evaluation carried out according to the risk evaluation method described in the embodiment of the present invention is shown. From the analysis, it can be seen that in Example A, the annular pressure of the oil casing rises significantly, reaching 35.61MPa at the wellhead. At this time, the failure risk of the test string at the wellhead is less than 0.01%, and the control effect is very significant.

[0090] In the embodiment of the cement sheath failure risk dimension in the above-mentioned embodiment A, there is a risk of tensile failure of the cement sheath, and the risk value distribution in the well section of 2100 meters to 3630 meters is 72.27% to 99.98%. Based on the multi-dimensional risk prediction analysis results, in embodiment A, the risk of tensile failure of the cement sheath is reduced by enhancing the toughness of the cement sheath and reducing the elastic modulus and Poisson's ratio. The elastic modulus and Poisson's ratio of the cement sheath are reduced to 2GPa and 0.18 respectively. At this time, the failure risk status of the cement sheath is as follows: Figure 8 As shown, the risks have been greatly reduced and the regulatory effects are very significant.

[0091] Embodiment 2

[0092] Based on the risk assessment method based on deepwater high temperature and high pressure completion test described in the first embodiment, the present invention also provides a risk assessment system based on deepwater high temperature and high pressure completion test. The system is used to implement the risk assessment method based on deepwater high temperature and high pressure completion test described in the first embodiment.

[0093] Fig.11 Schematic diagram of the structure of the risk assessment system based on deepwater high temperature and high pressure completion testing in the embodiment of the present application. Fig.11 As shown, the system described in the embodiment of the present invention includes: a data collection and parameter analysis module 1101 and a risk feature calculation and evaluation module 1102.

[0094] Specifically, the data acquisition and parameter analysis module 1101 is implemented according to the method described in step S110 above, and is configured to collect wellbore environmental information in real time and calculate the wellbore temperature and pressure distribution of the wellbore environmental information; the risk feature calculation and evaluation module 1102 is implemented according to the method described in step S120 above, and is configured to perform feature calculation and risk prediction analysis for the multi-dimensional risks of the wellbore system based on the calculation results of the wellbore temperature and pressure distribution. In an embodiment of the present invention, the multi-dimensional risks include: hydrate formation risk, test string failure risk, packer failure risk, and casing and cement sheath failure risk.

[0095] The present invention proposes a risk assessment method and system based on deepwater high-temperature and high-pressure completion testing. The present invention fully considers the multi-dimensional failure risks of the wellbore system caused by different wellbore environments during the completion testing process in a deepwater high-temperature and high-pressure environment. By studying the risk of hydrate formation, the risk of test string failure, the risk of packer failure, the risk of casing reliability failure, and the risk of cement ring sealing integrity failure, the risk status of deepwater high-temperature and high-pressure completion testing operations is evaluated. On this basis, high-risk points are found according to the evaluation results to formulate corresponding risk influencing factor control plans, and the control effects are calculated and analyzed. The present invention can effectively prevent accidents and reduce losses, and provide reliable theoretical guarantees and technical guidance for the smooth progress of completion testing operations.

[0096] In addition, the present invention can clarify the current risk status of deepwater high-temperature and high-pressure completion and testing operations, and can also sort out the risk status that the operation will face from the design stage. The application of the present invention can find out the main risk points and formulate corresponding risk control measures in a targeted manner, which can guide the design of deepwater high-temperature and high-pressure completion and testing operations, engineering risk monitoring and avoidance, reduce production costs, and provide reliable theoretical guarantees and technical guidance for the smooth progress of deepwater high-temperature and high-pressure completion and testing operations.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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 risk assessment method based on deepwater high temperature and high pressure completion testing. It is characterized in that include: Collect wellbore environmental information in real time, and calculate wellbore temperature and pressure distribution based on the wellbore environmental information; Based on the calculation results of the wellbore temperature and pressure distribution, characteristic calculation and risk prediction analysis are carried out for the multi-dimensional risks of the wellbore system, which include: hydrate formation risk, test string failure risk, packer failure risk, and casing and cement sheath failure risk.

2. The failure risk assessment method according to claim 1, It is characterized in that The step of collecting wellbore environmental information in real time and calculating the wellbore temperature and pressure distribution of the wellbore environmental information includes: According to the wellbore environmental information, the temperature and pressure distribution of the wellbore system is calculated, and based on this, the temperature and pressure distribution in the seawater section completion test string, the temperature and pressure distribution in the formation section annulus, and the temperature and pressure distribution in the formation section completion test string are calculated respectively. The wellbore environmental information includes but is not limited to: seawater temperature, water depth, wellbore structure data, elastic-plastic mechanical parameters and thermodynamic parameters of the string and cement ring, liquid flow state in the well, liquid properties and thermodynamic parameters in the well, formation temperature data, and reservoir temperature and pressure data.

3. The failure risk assessment method according to claim 2, It is characterized in that The process of characterizing the risk of hydrate formation includes: Based on the temperature and pressure distribution in the completion test string of the seawater section and the temperature and pressure distribution in the annulus of the formation section, a hydrate phase equilibrium temperature curve is constructed to characterize the critical temperature of hydrate formation at different depths; Based on the hydrate phase equilibrium temperature curve, the hydrate formation area is predicted, wherein if the temperature in the test string is lower than the phase equilibrium temperature, there is a risk of hydrate formation in the depth area.

4. The failure risk assessment method according to claim 2 or 3, It is characterized in that The process of characterizing the failure risk of the test string includes: According to the temperature and pressure distribution in the annulus of the formation well section and the temperature and pressure distribution in the completion test string of the formation well section, the first external load information characterizing the stress condition of the test string is calculated, and then combined with the strength of the test string, a first curve chart of the normal distribution probability density characterizing the external load and strength of the string is drawn.

5. The failure risk assessment method according to any one of claims 2 to 4, It is characterized in that The process of characterizing the risk of packer failure includes: Based on the length of the tubing above the packer in the formation well section, the elastic-plastic mechanical parameters of the tubing, the thermodynamic parameters of the tubing, the reservoir temperature and pressure data, and the formation temperature and pressure data, the axial force of the completion test tubing string borne by the packer is calculated; Based on the axial force of the completion test string borne by the packer, combined with the temperature and pressure distribution in the string of the formation well section, the pressure borne by the lower surface of the packer is calculated, and combined with the temperature and pressure distribution of the annulus in the formation well section, the pressure exerted by the annulus liquid on the upper surface of the packer is calculated; The difference between the pressure on the lower surface of the packer and the pressure exerted by the annular space liquid on the upper surface of the packer is determined as the packer annular space pressure difference.

6. The failure risk assessment method according to any one of claims 2 to 5, It is characterized in that The process of characterizing the risk of casing and cement sheath failure includes: According to the wellbore structure data, the elastic-plastic mechanical parameters and thermodynamic parameters of the casing and cement sheath, the flow state of the liquid in the well, the properties and thermodynamic parameters of the liquid in the well, the formation temperature data and the reservoir temperature and pressure data, the second external load information and the corresponding strength information characterizing the stress condition of the casing are calculated, based on which, a second curve graph of the normal distribution probability density characterizing the external load and strength of the casing is drawn, and the third external load information and the corresponding strength information characterizing the stress condition of the cement sheath are calculated, based on which, a third curve graph of the normal distribution probability density characterizing the external load and strength of the cement sheath is drawn.

7. The failure risk assessment method according to claim 3, It is characterized in that The risk analysis process for hydrate formation risk includes: Based on the predicted hydrate formation area, combined with the string temperature distribution and the hydrate phase equilibrium temperature, the hydrate formation range is determined and the dimensionless undercooling coefficient characterizing the hydrate formation risk degree is calculated, so as to determine the hydrate formation risk distribution within the current hydrate formation range by applying the dimensionless undercooling coefficient, wherein the dimensionless undercooling coefficient is calculated using the following expression: Among them, F R Represents dimensionless undercooling coefficient, dimensionless; C d represents the degree of supercooling, in °C; T represents the phase equilibrium temperature, in °C; T i It indicates the actual temperature in the column, in °C; z indicates the hydrate depth, in m.

8. The failure risk assessment method according to claim 4, It is characterized in that The process of conducting risk analysis on the risk of test string failure includes: The generalized stress intensity interference theory is applied to perform interference analysis on the first curve diagram to quantitatively evaluate the failure risk value of the completion test string.

9. The failure risk assessment method according to claim 5, It is characterized in that The process of conducting risk analysis for packer failure risk includes: According to the axial force of the completion test string borne by the packer and the annulus pressure difference of the packer, a preset packer envelope curve is used to determine whether the current packer has a risk of failure, wherein if the coupling position point between the axial force of the completion test string borne by the packer and the annulus pressure difference of the packer is within the range of the packer envelope curve, then the current packer has no risk of failure. The packer envelope curve is a safety closed-loop boundary curve formed by coupling the safety range of the axial force of the tubing borne by the packer and the safety range of the annulus pressure difference.

10. The failure risk assessment method according to claim 6, It is characterized in that The risk analysis process for casing and cement sheath failure includes: Applying generalized stress intensity interference theory to perform interference analysis on the second curve graph, quantitatively evaluating the casing failure risk value; The generalized stress intensity interference theory is applied to perform interference analysis on the third curve diagram to quantitatively evaluate the risk value of cement sheath failure.

11. The failure risk assessment method according to any one of claims 1 to 10, It is characterized in that The failure risk assessment method also includes: integrating the risk prediction analysis results of multi-dimensional risks, conducting analysis of major influencing factors of failure risks, and providing corresponding risk control plans for the major influencing factors of risks.

12. A risk assessment system based on deepwater high temperature and high pressure completion testing. It is characterized in that include: A data acquisition and parameter analysis module, which is configured to acquire wellbore environmental information in real time and calculate wellbore temperature and pressure distribution of the wellbore environmental information; The risk characteristic calculation and evaluation module is configured to perform characteristic calculation and risk prediction analysis for the multi-dimensional risks of the wellbore system based on the calculation results of the wellbore temperature and pressure distribution. The multi-dimensional risks include: hydrate formation risk, test string failure risk, packer failure risk, and casing and cement sheath failure risk.

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