Method and device for predicting ring-closed loop empty parameters of double packers of fractured well

Abstract

The embodiment of the invention discloses a method and device for predicting ring closed-loop empty parameters of double packers of a fractured well, and the method comprises the steps: constructing a first mapping relation corresponding to the total volume change of ring closed-loop air fluid according to a mapping relation between the volume change of the ring closed-loop air fluid caused by the action of key factors and a first parameter; according to the mapping relation between the closed loop air volume change caused by well structure deformation and a second parameter, a second mapping relation corresponding to the closed loop air fluid total volume change is constructed; combining the first mapping relational expression and the second mapping relational expression, and constructing a target relational expression about the closed loop empty parameters; and according to the parameter value of at least one parameter in the circle closed-loop null parameters and the target relational expression, calculating predicted values of other parameters in the circle closed-loop null parameters. By means of the mode, an implementation mode for predicting the loop-closed loop empty parameters in the fracturing construction period is provided, and the loop-closed loop empty parameters in the fracturing construction period can be efficiently and accurately predicted.

Description

Technical Field

[0001] This application relates to the field of hydraulic fracturing technology for oil and gas reservoirs, specifically to a method and apparatus for predicting the closed annulus parameters of a dual packer in a fracturing well. Background Technology

[0002] In offshore drilling and completion operations, fracturing operations are characterized by high pressure, high risk, and high difficulty. Many accidents in both offshore and onshore fracturing operations are caused by tubing string failure. Based on the well control requirements and tubing string strength requirements for offshore operations, fracturing completion operations may involve tubing strings with double packers and a closed space between them.

[0003] During fracturing operations, cryogenic fracturing fluid continuously enters the formation at high flow rates and pressures, causing the temperature of various parts of the casing and tubing in the well to gradually decrease. As the downhole temperature continues to decrease, the annular pressure and fluid volume between the two packers change. Under the combined effect of temperature and annular pressure changes, the near-wellbore formation, cement sheath, and casing deform. Under the combined effect of annular pressure and tubing pressure, the tubing deforms, ultimately causing drastic changes in the annular pressure, which endangers wellbore integrity and increases operational risks. Therefore, there is an urgent need for a method to predict the parameters of the annular loops inside the two packers in advance during fracturing. Summary of the Invention

[0004] In view of the above problems, this application is made in order to provide a method, apparatus, computing device, computer storage medium and computer program product for predicting the closed annulus parameters of a dual packer in a fracturing well to overcome or at least partially solve the above problems.

[0005] According to one aspect of the embodiments of this application, a method for predicting the closed-loop air parameters of a dual packer in a fracturing well is provided, comprising: Based on the mapping relationship between the volume change of the closed-loop air fluid caused by the action of key factors and the first parameter, a first mapping relationship corresponding to the total volume change of the closed-loop air fluid is constructed. Based on the mapping relationship between the change in the volume of the closed annulus caused by well structure deformation and the second parameter, a second mapping relationship corresponding to the change in the total fluid volume of the closed annulus is constructed; wherein, both the first parameter and the second parameter include at least one parameter among the closed annulus parameters; By combining the first mapping relation and the second mapping relation, a target relation is constructed regarding the closed loop space parameter of the loop. Based on the parameter value of at least one parameter in the closed loop empty parameters and the target relation, calculate the predicted values ​​of the other parameters in the closed loop empty parameters.

[0006] Optionally, the closed-loop parameters include: closed-loop temperature change and closed-loop pressure change.

[0007] Optionally, the method further includes: Based on the fluid thermal expansion calculation method, a mapping relationship is constructed between the volume change of a closed-loop air fluid caused by the action of key factors and the first parameter; Based on the calculation method of the thermal deformation effect of the pipe body, a mapping relationship between the change in the closed annulus volume caused by the deformation of the well structure and the second parameter is constructed.

[0008] Optionally, the key factors include temperature and pressure; the step of constructing a first mapping relationship corresponding to the total volume change of the closed-loop air fluid based on the mapping relationship between the volume change of the closed-loop air fluid caused by the key factors and the first parameter further includes: Based on the fact that the total volume change of the closed-loop air fluid is equal to the difference between the volume change of the closed-loop air fluid due to temperature and the volume change of the closed-loop air fluid due to pressure, a first mapping relationship corresponding to the total volume change of the closed-loop air fluid is constructed.

[0009] Optionally, the well structure includes tubing and other structures, wherein the other structures include casing, cement sheath, and formation; the step of constructing a second mapping relationship corresponding to the change in the total fluid volume of the closed annulus based on the mapping relationship between the change in the closed annulus volume caused by well structure deformation and the second parameter further includes: Based on the fact that the total volume change of the closed-loop fluid is equal to the sum of the volume change of the closed-loop fluid caused by the tubing deformation and the volume change of the closed-loop fluid caused by the other structures, a second mapping relationship is constructed corresponding to the total volume change of the closed-loop fluid.

[0010] Optionally, the volume change of the closed annular fluid due to temperature is related to the temperature change of the closed annular fluid, and the volume change of the closed annular fluid due to pressure is related to the pressure change of the closed annular fluid; the volume change of the closed annular fluid caused by tubing deformation is related to the temperature change and pressure change of the closed annular fluid, and the volume change of the closed annular fluid caused by other structures is related to the temperature change of the closed annular fluid.

[0011] According to another aspect of the embodiments of this application, a device for predicting the closed-loop annulus parameters of a fracturing well dual packer is provided, comprising: The first construction module is adapted to construct a first mapping relationship formula corresponding to the total volume change of the closed annular fluid based on the mapping relationship between the volume change of the closed annular fluid caused by the action of key factors and a first parameter; and to construct a second mapping relationship formula corresponding to the total volume change of the closed annular fluid based on the mapping relationship between the volume change of the closed annular fluid caused by well structure deformation and a second parameter; wherein the first parameter and the second parameter both include at least one parameter among the closed annular parameters; The second construction module is adapted to combine the first mapping relation and the second mapping relation to construct a target relation about the closed loop space parameter; The prediction module is adapted to calculate the predicted values ​​of other parameters in the closed loop empty parameters based on the parameter values ​​of at least one parameter in the closed loop empty parameters and the target relation.

[0012] Optionally, the closed-loop parameters include: closed-loop temperature change and closed-loop pressure change.

[0013] Optionally, the first building module is further adapted to: Based on the fluid thermal expansion calculation method, a mapping relationship is constructed between the volume change of a closed-loop air fluid caused by the action of key factors and the first parameter; Based on the calculation method of the thermal deformation effect of the pipe body, a mapping relationship between the change in the closed annulus volume caused by the deformation of the well structure and the second parameter is constructed.

[0014] Optionally, the key factors include temperature and pressure; the first building block is further adapted to: Based on the fact that the total volume change of the closed-loop air fluid is equal to the difference between the volume change of the closed-loop air fluid due to temperature and the volume change of the closed-loop air fluid due to pressure, a first mapping relationship corresponding to the total volume change of the closed-loop air fluid is constructed.

[0015] Optionally, the well structure includes tubing and other structures, the other structures including casing, cement sheath, and formation; the first building module is further adapted to: Based on the fact that the total volume change of the closed-loop fluid is equal to the sum of the volume change of the closed-loop fluid caused by the tubing deformation and the volume change of the closed-loop fluid caused by the other structures, a second mapping relationship is constructed corresponding to the total volume change of the closed-loop fluid.

[0016] Optionally, the volume change of the closed annular fluid due to temperature is related to the temperature change of the closed annular fluid, and the volume change of the closed annular fluid due to pressure is related to the pressure change of the closed annular fluid; the volume change of the closed annular fluid caused by tubing deformation is related to the temperature change and pressure change of the closed annular fluid, and the volume change of the closed annular fluid caused by other structures is related to the temperature change of the closed annular fluid.

[0017] According to another aspect of the embodiments of this application, a computing device is provided, including: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus; The memory is used to store at least one executable instruction, which causes the processor to perform the operation corresponding to the above-mentioned method for predicting the closed loop air parameters of the dual packer in a fractured well.

[0018] According to another aspect of the embodiments of this application, a computer storage medium is provided, wherein at least one executable instruction is stored in the storage medium, the executable instruction causing a processor to perform an operation corresponding to the above-described method for predicting the closed annulus parameters of a fracturing well dual packer.

[0019] According to another aspect of the embodiments of this application, a computer program product is provided, including at least one executable instruction, which causes a processor to perform operations corresponding to the above-described method for predicting the closed-loop annulus parameters of a fracturing well dual packer.

[0020] According to the method and apparatus for predicting the closed annular space parameters of a fracturing well dual packer provided in this application, a first mapping relationship is constructed based on the mapping relationship between the volume change of the closed annular space fluid caused by key factors and a first parameter; a second mapping relationship is constructed based on the mapping relationship between the volume change of the closed annular space fluid caused by well structure deformation and a second parameter; wherein, both the first parameter and the second parameter include at least one parameter among the closed annular space parameters; by combining the first mapping relationship and the second mapping relationship, a target relationship for the closed annular space parameters is constructed; and based on the parameter value of at least one parameter among the closed annular space parameters and the target relationship, the predicted values ​​of other parameters among the closed annular space parameters are calculated. The above method provides a way to predict the closed annulus parameters during fracturing operations, which can effectively solve the problem of the difficulty in predicting the closed annulus parameters of dual packers in high-temperature and high-pressure fracturing wells. It can efficiently and accurately predict the closed annulus parameters during fracturing operations and can be applied to the strength verification analysis of dual packers and tubing during fracturing, which helps to judge construction risks in advance and improve the safety of tubing during fracturing operations.

[0021] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of the embodiments of this application are described below. Attached Figure Description

[0022] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A flowchart illustrating a method for predicting the closed-loop air parameters of a dual packer in a fracturing well according to an embodiment of this application is shown. Figure 2 A flowchart illustrating a method for predicting the closed-loop parameters of a dual packer in a fracturing well according to another embodiment of this application is shown. Figure 3 A schematic diagram of reservoir temperature at different vertical depths under different construction measures in working condition 1 is shown. Figure 4 A schematic diagram is shown showing the changes in closed-loop pressure caused by different closed-loop temperature changes predicted using the method of the embodiments of this application; Figure 5 A schematic diagram of reservoir temperature at different vertical depths under different construction measures in working condition 2 is shown; Figure 6 A structural block diagram of a closed-loop air parameter prediction device for a fracturing well dual packer according to an embodiment of this application is shown; Figure 7 A schematic diagram of the structure of a computing device according to an embodiment of this application is shown. Detailed Implementation

[0023] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0024] Figure 1 A flowchart illustrating a method for predicting the closed-loop air parameters of a dual packer in a fracturing well according to an embodiment of this application is shown, as follows: Figure 1 As shown, the method includes the following steps: Step S110: Based on the mapping relationship between the volume change of the closed-loop air fluid caused by the key factors and the first parameter, construct the first mapping relationship corresponding to the total volume change of the closed-loop air fluid.

[0025] The volume change of fluid in the closed annulus due to the action of key factors is related to at least one parameter of the closed annulus parameters (i.e., the first parameter) and several fracturing operation parameters. By obtaining the parameter values ​​of the fracturing operation parameters of the target fracturing well as known data, the mapping relationship between the volume change of fluid in the closed annulus due to the action of key factors and the first parameter can be obtained.

[0026] The change in the total volume of the closed-loop air fluid is related to the change in volume of the closed-loop air fluid caused by the action of key factors. Therefore, by utilizing the mapping relationship between the change in volume of the closed-loop air fluid caused by the action of key factors and at least one parameter of the closed-loop air parameters, and the relationship between the change in the total volume of the closed-loop air fluid and the change in volume of the closed-loop air fluid caused by the action of key factors, an expression (i.e., the first mapping relationship) is constructed to characterize the mapping relationship between the change in the total volume of the closed-loop air fluid and at least one parameter of the closed-loop air parameters.

[0027] Step S120: Based on the mapping relationship between the change in the volume of the closed annulus caused by the deformation of the well structure and the second parameter, construct the second mapping relationship corresponding to the change in the total volume of fluid in the closed annulus.

[0028] The change in the volume of the closed annulus caused by well structure deformation is related to at least one parameter (i.e., the second parameter) of the closed annulus parameters and several fracturing operation parameters. By obtaining the parameter values ​​of the fracturing operation parameters of the target fracturing well as known data, the mapping relationship between the change in the volume of the closed annulus caused by well structure deformation and the second parameter can be obtained.

[0029] The change in the total volume of fluid in the closed annulus is related to the change in the volume of the closed annulus caused by well structure deformation. Therefore, by utilizing the mapping relationship between the change in the volume of the closed annulus caused by well structure deformation and at least one parameter of the closed annulus parameters, and the relationship between the change in the total volume of fluid in the closed annulus and the change in the volume of the closed annulus caused by well structure deformation, an expression (i.e., the second mapping relationship) is constructed to characterize the mapping relationship between the change in the total volume of fluid in the closed annulus and at least one parameter of the closed annulus parameters.

[0030] Step S130: Combine the first mapping relation and the second mapping relation to construct the target relation for the closed loop empty parameters.

[0031] By combining the first and second mapping relations, we obtain the objective relation where all parameters in the closed loop empty parameter are unknowns.

[0032] Step S140: Calculate the predicted values ​​of other parameters in the closed-loop empty parameters based on the parameter values ​​of at least one parameter in the closed-loop empty parameters and the target relation.

[0033] In actual fracturing operations, it is necessary to predict the closed loop parameters in order to optimize fracturing measures and conduct double packer string verification. By setting the parameter value of at least one parameter in the closed loop parameters and substituting it into the above target relationship, the predicted values ​​of other parameters can be obtained, thus completing the prediction of the closed loop parameters.

[0034] According to the method for predicting the annular parameters of a dual packer in a fracturing well provided in this application, a first mapping relationship is constructed based on the mapping relationship between the volume change of the annular fluid caused by key factors and a first parameter, corresponding to the total volume change of the annular fluid. A second mapping relationship is constructed based on the mapping relationship between the volume change of the annular fluid caused by well structure deformation and a second parameter, corresponding to the total volume change of the annular fluid. The first and second mapping relationships are combined to construct a target relationship for the annular parameters. Based on the parameter value of at least one parameter in the annular parameters and the target relationship, the predicted values ​​of other parameters in the annular parameters are calculated. This method provides a way to predict the annular parameters during fracturing operations, effectively solving the problem of difficult prediction of the annular parameters of dual packers in high-temperature and high-pressure fracturing wells. It can efficiently and accurately predict the annular parameters during fracturing operations and can be applied to the strength verification analysis of dual packers and tubing during fracturing, helping to predict construction risks in advance and improve the safety of the tubing during fracturing operations.

[0035] Figure 2 A flowchart illustrating a method for predicting the closed-loop air parameters of a dual packer in a fracturing well according to another embodiment of this application is shown, as follows: Figure 2 As shown, the method includes the following steps: Step S210: Based on the fluid thermal expansion calculation method, construct the mapping relationship between the volume change of the closed-loop fluid caused by the action of key factors and the first parameter.

[0036] Key specific factors include temperature and pressure, with the closed-loop air parameters specifically including the temperature change of the closed-loop air. and closed-loop air pressure changes The first parameter includes at least one parameter from the closed-loop empty parameters.

[0037] Specifically, the volume change of fluid in the closed annulus due to temperature is related to the temperature change of the closed annulus. Based on the fluid thermal expansion calculation method, the calculation method for the volume change of fluid in the closed annulus due to temperature is as follows: (1) In formula (1), This represents the volume change of a closed-loop fluid medium after free expansion due to temperature effects, i.e., the volume change of a closed-loop fluid due to temperature. The unit is m. 3 ; This indicates the inner diameter of the casing, in meters (m). This indicates the outer diameter of the oil pipe, in meters (m). Indicates the spacing between the double packers, in meters (m). This represents the coefficient of thermal expansion of the annular fluid, with units of °C. -1 ; This represents the temperature change in the closed-loop air, expressed in °C.

[0038] By obtaining the parameter values ​​of all parameters in formula (1) for the target fractured well, except for the annular temperature change, and substituting them into formula (1), we can obtain an expression characterizing the mapping relationship between the volume change of the fluid in the annular space due to temperature and the annular temperature change. That is, when the key factor is temperature, the first parameter is specifically the annular temperature change.

[0039] Specifically, the volume change of fluid in the closed annulus due to pressure is related to the pressure change in the closed annulus. Based on the fluid thermal expansion calculation method, the calculation method for the volume change of fluid in the closed annulus due to pressure can be determined as follows: (2) In formula (2), This represents the volume change of a closed-loop air fluid due to pressure, expressed in cubic meters (m³). 3 ; This indicates the change in closed-loop air pressure, in MPa. This represents the closed loop volume in its original state, in meters (m). 3 E represents the fluid elastic modulus, with units of MPa.

[0040] By obtaining the parameter values ​​of all parameters in formula (2) for the target fractured well, except for the change in annular pressure, and substituting them into formula (2), we can obtain an expression characterizing the mapping relationship between the volume change of fluid in the annular space due to pressure and the change in annular pressure. That is, when the key factor is pressure, the first parameter is specifically the change in annular pressure.

[0041] Step S220: Based on the calculation method of the thermal deformation effect of the pipe body, construct the mapping relationship between the change in the closed annulus volume caused by the deformation of the well structure and the second parameter.

[0042] Specifically, the well structure includes tubing and other structures, including casing, cement sheath, and formation. That is, the change in annular volume caused by well structure deformation includes changes in annular volume caused by tubing deformation and changes in annular volume caused by casing, cement sheath, and formation deformation. The second parameter includes at least one of the annular parameters.

[0043] Specifically, the change in the volume of the closed annulus caused by tubing deformation is related to the changes in the temperature and pressure of the closed annulus. Based on the calculation method of the thermal deformation effect of the tubing, when the tubing inside the double packer closed system is considered similar to a free section of the tubing string, the calculation method for the change in the volume of the closed annulus caused by tubing deformation can be determined as follows: (3) (4) In formula (3), This represents the change in the volume of the closed annulus caused by tubing deformation under the influence of temperature and pressure, expressed in meters (m). 3 ; Indicates the spacing between the double packers, in meters (m). This indicates the outer diameter of the oil pipe, in meters (m). This indicates the radial displacement of the tubing under the influence of temperature and pressure, expressed in meters (m).

[0044] In formula (4), This indicates the radial displacement of the tubing under the influence of temperature and pressure, and the unit is meters (m). This represents the Poisson's ratio of the oil pipeline, which is dimensionless. This represents the coefficient of thermal expansion of the oil pipe, in °C. -1 ; This represents the temperature change in the closed-loop air, in °C. This indicates the inner radius of the oil pipe, in meters (m). This indicates the outer diameter of the oil pipe, in meters (m). This indicates the elastic modulus of the tubing, expressed in GPa. This indicates the change in closed-loop air pressure, in MPa. This indicates the pressure change inside the oil pipe, expressed in MPa.

[0045] By obtaining the parameter values ​​of all parameters except for the annular temperature and pressure changes in the traps in formulas (3) and (4) for the target fracturing well, and substituting them into formulas (3) and (4), an expression representing the mapping relationship between the annular volume change caused by tubing deformation and the annular temperature and pressure changes can be obtained. That is, when the well structure is tubing, the second parameter specifically includes the annular temperature and pressure changes.

[0046] Specifically, the changes in the volume of the closed annulus caused by other structures (i.e., the changes in the volume of the closed annulus caused by casing, cement sheath, and formation deformation) are related to the changes in the temperature of the closed annulus. Based on the calculation method of the thermal deformation effect of the casing, the calculation method of the changes in the volume of the closed annulus caused by casing, cement sheath, and formation deformation under the influence of temperature and pressure is as follows: (5) In formula (5), This represents the volume change of the closed annulus caused by casing, cement sheath, and formation deformation, in meters (m). 3 ; Indicates the spacing between the double packers, in meters (m). This indicates the inner diameter of the casing, in meters (m). This represents the displacement of the inner wall of the casing, in meters (m). The value is taken as the displacement of the inner wall of the casing when the inner diameter of the casing is approximately equal to the outer diameter of the casing.

[0047] Displacement of the inner wall of the casing The specific calculation method is as follows: (6) In formula (6), This indicates the outer diameter of the casing, in meters (m). and These are used to calculate intermediate quantities.

[0048] The specific calculation methods for intermediate quantities are as follows: (7) (8) in, This represents the Poisson's ratio of the casing, which is dimensionless. This indicates the inner diameter of the casing, in meters (m). This indicates the closed-loop air pressure of the casing, in MPa. This indicates the pressure exerted by the cement ring on the casing, expressed in MPa. This indicates the outer diameter of the casing, in meters (m). This represents the elastic modulus of the casing, expressed in GPa. This represents the coefficient of thermal expansion of the casing, in °C. -1 .

[0049] By obtaining the parameter values ​​of all parameters except for the annular temperature change in the formulas (5)-(8) for the target fracturing well, and substituting them into formulas (5)-(8), we can obtain an expression representing the mapping relationship between the annular volume change and the annular temperature change caused by casing, cement sheath, and formation deformation. That is, when the well structure consists of casing, cement sheath, and formation, the second parameter specifically includes the annular temperature change.

[0050] Step S230: Based on the fact that the total volume change of the closed-loop air fluid is equal to the difference between the volume change of the closed-loop air fluid due to temperature and the volume change of the closed-loop air fluid due to pressure, a first mapping relationship corresponding to the total volume change of the closed-loop air fluid is constructed.

[0051] Specifically, without considering tubing and casing couplings, the total volume change of the fluid medium in the closed annulus due to the combined effects of temperature and pressure (i.e., the total volume change of the fluid in the closed annulus) is calculated as follows: (9) In formula (9), This represents the change in the total volume of the closed-loop airflow, in cubic meters (m³). 3 ; This represents the volume change of a closed-loop air fluid due to temperature changes, expressed in cubic meters (m³). 3 ; This represents the volume change of a closed-loop air fluid due to pressure, expressed in cubic meters (m³). 3 .

[0052] Through the aforementioned steps, we obtained: an expression representing the mapping relationship between the volume change of the closed-loop air fluid due to temperature and the temperature change of the closed-loop air, and an expression representing the mapping relationship between the volume change of the closed-loop air fluid due to pressure and the pressure change of the closed-loop air. According to the calculation method shown in formula (9), we obtained the first mapping relationship representing the mapping relationship between the pressure change of the closed-loop air, the temperature change of the closed-loop air, and the total volume change of the closed-loop air fluid.

[0053] Step S240: Based on the fact that the total volume change of the closed-loop fluid is equal to the sum of the volume change of the closed-loop fluid caused by the tubing deformation and the volume change of the closed-loop fluid caused by other structures, a second mapping relationship corresponding to the total volume change of the closed-loop fluid is constructed.

[0054] Without considering liquid loss, to satisfy the principle of volume compatibility, the calculation method for the total volume change of the fluid in the closed annulus is as follows: (10) In formula (10), This represents the change in the total volume of the closed-loop airflow, in cubic meters (m³).3 ; This represents the change in the volume of the closed annulus caused by tubing deformation, expressed in meters (m). 3 ; This indicates the volume change of the closed annulus caused by casing, cement sheath, and formation deformation.

[0055] Through the aforementioned steps, we obtained: an expression characterizing the mapping relationship between the change in the volume of the closed annulus caused by tubing deformation and the changes in the temperature and pressure of the closed annulus; and an expression characterizing the mapping relationship between the change in the volume of the closed annulus caused by the deformation of the casing, cement sheath, and formation under the influence of temperature and pressure and the changes in the temperature of the closed annulus. According to the calculation method of formula (10), we can obtain the second mapping relationship characterizing the mapping relationship between the change in the total volume of fluid in the closed annulus and the changes in the temperature and pressure of the closed annulus.

[0056] Step S250: Combine the first mapping relation and the second mapping relation to construct the target relation for the closed loop empty parameters.

[0057] The first mapping relationship is as follows: (11) The second mapping relationship is as follows: (12) By combining the two expressions above, we can construct the objective relation for the closed-loop empty parameters, as shown below: (13) Transforming expression (13), we obtain the change in closed-loop air pressure. The independent variable is the temperature change of the closed loop. The objective relationship for the dependent variable is, or, to obtain the temperature change in the closed loop. The independent variable is the change in closed-loop air pressure. The objective relation for the dependent variable is denoted as .

[0058] Step S260: Calculate the predicted values ​​of other parameters in the closed-loop empty parameters based on the parameter value of at least one parameter in the closed-loop empty parameters and the target relation.

[0059] The parameter value of one parameter is set according to the construction operation requirements, and the predicted value of another parameter is calculated based on the constructed relationship.

[0060] Specifically, by setting the parameter value for the change in closed annular temperature and substituting it into the above target relationship, the predicted value of the change in closed annular pressure is calculated. In this way, the decrease in closed annular temperature can be estimated using fracturing parameters, and then the allowable change in closed annular pressure can be calculated using the decrease in closed annular temperature.

[0061] Specifically, by setting the parameter value for the change in closed-loop annular pressure and substituting it into the above-mentioned relationship, the predicted value of the change in closed-loop annular temperature is calculated. During fracturing operations, the low-temperature fluid at the surface continuously flows into the formation at high flow rate and high pressure, causing the temperature at various points in the well casing to gradually decrease. This leads to the contraction and depressurization of the fluid in the closed-loop annular space inside the double packer. This results in the packer experiencing a higher pressure differential, the casing experiencing a higher external pressure differential, and the tubing experiencing a higher internal pressure differential. This method allows for the prediction of the closed-loop annular pressure of the double packer during fracturing, and thus, the appropriate strength of the tubing string can be selected for fracturing operations based on the annular pressure changes.

[0062] Predicting the annular pressure of dual packers in fracturing wells has significant practical applications. Specifically, during fracturing operations, as cryogenic fluid is continuously injected into the wellbore, failure to monitor the annular pressure of the dual packers can increase the risk of casing, tubing, and packer failure due to annular pressure changes caused by temperature variations. Fracturing operations involve high-volume, cryogenic fluid continuously flowing into the formation, which simultaneously leads to a gradual decrease in wellbore temperature, resulting in a reduction in annular pressure. This reduction in annular pressure increases the pressure differential experienced by the packers, the internal pressure differential of the tubing string, and the external pressure differential of the casing. Therefore, predicting the annular pressure of dual packers is a crucial aspect of fracturing operations, enhancing safety, efficiency, and effectiveness, and is of great importance to the effective development of oil and gas resources. The method for predicting the closed annular pressure of a dual packer in a fracturing well provided in this application embodiment can be better applied to the strength verification analysis of the dual packer and tubing during fracturing operations, so as to solve the construction safety problem caused by the change in annular pressure due to the decrease in annular temperature when pumping low-temperature fracturing fluid at high flow rates.

[0063] In summary, the method for predicting the closed annulus parameters of a dual packer in a fracturing well according to the embodiments of this application firstly establishes a mapping relationship between the volume change of the closed annulus fluid caused by key factors and the closed annulus parameters, and also establishes a mapping relationship between the volume change of the closed annulus caused by well structure deformation and the closed annulus parameters; secondly, based on two different calculation methods for the total volume change of the closed annulus fluid, a target relationship for the closed annulus parameters is constructed; finally, parameter values ​​are set for the changes in closed annulus temperature or pressure, and substituting them into the target relationship yields the predicted values ​​for the changes in closed annulus pressure or temperature. The embodiments of this application provide a method for predicting the closed annulus parameters during fracturing operations, effectively solving the problem of the difficulty in predicting the closed annulus parameters of dual packers in high-temperature and high-pressure fracturing wells. It can efficiently and accurately predict the closed annulus parameters during fracturing operations and can be applied to the strength verification analysis of dual packers and tubing during fracturing, helping to predict construction risks in advance and improve the safety of the tubing during fracturing operations.

[0064] The application of the method in the embodiments of this application is illustrated below using actual working conditions as an example.

[0065] Working Condition 1: Construction Discharge Volume 4m 3 / min, construction time 120min, fracturing fluid temperature 26℃, formation depth 3580m, formation temperature 125℃, fracturing pressure gradient 0.020MPa / m, annular fluid column pressure gradient 0.0098MPa / m.

[0066] The tubing and casing specifications are as follows: ① 4-1 / 2" tubing: outer diameter 114.3 mm, inner diameter 88.9 mm, steel grade L80, pressure rating 21.5 lbf / ft, external extrusion strength 108.94 MPa, internal pressure strength 107.28 MPa; ② 7" tubing: outer diameter 177.8 mm, inner diameter 157.1 mm, steel grade N80, pressure rating 29.0 lbf / ft, external extrusion strength 48.47 MPa, internal pressure strength 56.26 MPa; ③ Packer differential pressure resistance 69 MPa.

[0067] Other calculation parameters are: annular fluid expansion coefficient 0.00045℃. -1 The coefficient of thermal expansion of the oil and casing is 0.000483℃. -1 The elastic modulus of the oil and casing is 210 GPa, and the Poisson's ratio of the oil and casing is 0.3.

[0068] For the verification of the dual packer tubing under operating condition 1, the steps for predicting the change in closed-loop annular air pressure using the method of the embodiments of this application, and the corresponding optimization measures, are as follows: (1) The vertical depth of the reservoir is 3580m, the calculated reservoir pressure is about 35.8MPa, and the pressure inside the tubing is 71.6MPa.

[0069] (2) Based on the internal pressure resistance of the tubing, the external extrusion resistance of the casing, the pressure resistance of the packer, and the safety factor required by the system (the internal pressure resistance safety factor is greater than 1.1 and the external extrusion resistance safety factor is greater than 1.125), when the closed annular pressure is as low as -7.3MPa, the tubing strength just meets the safety requirements, that is, the closed annular pressure is reduced by a maximum of 43.1MPa.

[0070] (3) According to the method of the embodiment of this application, the predicted value of the change in the closed annular air temperature is calculated using the allowable reduction range of the closed annular air pressure in (2) as 53.8°C, that is, the closed annular air temperature is allowed to decrease by a maximum of 53.8°C during fracturing.

[0071] (4) Based on simulation calculations, the wellbore should first be circulated with cryogenic fluid until the reservoir temperature drops to 93°C. During the fracturing operation, the downhole temperature will decrease by approximately 53°C (temperature changes are as follows). Figure 3 (As shown), only then can the strength requirements be met. Figure 3 The diagram shows the reservoir temperature at different vertical depths under different construction measures in Condition 1. The Undisturbed-1 curve corresponds to the reservoir temperature at different vertical depths calculated according to the low temperature gradient when no construction measures are taken. The Operation #1-1 curve corresponds to the reservoir temperature at different vertical depths after circulating low temperature fluid in the wellbore before fracturing operations. The FRAC-4M3 / MIN-1 curve corresponds to the reservoir temperature at different vertical depths calculated when fracturing fluid is directly pumped in without prior circulation of low temperature fluid in the wellbore before fracturing operations.

[0072] Operating Condition 2: The tubing and casing specifications are as follows: ① 4-1 / 2" tubing: outer diameter 114.3mm, inner diameter 88.9mm; ② 7" tubing: outer diameter 177.8mm, inner diameter 157.1mm.

[0073] Other calculation parameters are: annular fluid expansion coefficient 0.00045℃. -1 The coefficient of thermal expansion of the oil and casing is 0.000483℃. -1 The elastic modulus of the oil and casing is 210 GPa, and the Poisson's ratio of the oil and casing is 0.3.

[0074] For the prediction of closed annular pressure of double packers under working condition 2, without considering the strength verification of the tubing under specific fracturing operation conditions, only the change of closed annular pressure caused by the change of closed annular temperature under the preset tubing structure is calculated, in order to obtain the influence law of closed annular temperature change on closed annular pressure.

[0075] Specifically, when the temperature gradient of the closed-loop air (in °C) is 0, -10, -20, -30, -40, -50, -60, -70, -80, -90, -100, under the action of this temperature difference, the decrease in the closed-loop air pressure (in MPa) predicted by the method of the embodiments of this application is 0, -6.3, -14.6, -23.1, -31.4, -40.1, -48.2, -56.7, -64.9, -73.4, -82.1. Figure 4 A schematic diagram is shown showing the changes in closed-loop annulus pressure caused by different closed-loop annulus temperature variations predicted using the method of the embodiments of this application.

[0076] Based on the above predictions, to ensure the strength requirements of the tubing string, the following measures can be taken before fracturing: Measure 1: After running the tubing string, circulate cryogenic fluid to lower the wellbore temperature, and then set the tubing string. Measure 2: Perforate a small number of holes in the casing at the double packer to release the closed state of this section.

[0077] Using the method of this application embodiment to predict the closed annular pressure during construction can help identify construction risks in advance and take corresponding measures to improve the safety of the tubing during fracturing operations. By predicting the closed annular pressure, it can help on-site construction personnel predict complex situations that may occur during fracturing operations, or change the wellbore temperature conditions before fracturing operations, to ensure that fracturing operations are carried out safely according to the predetermined plan.

[0078] In contrast, for condition one, the method of the embodiments of this application is not used for prediction; instead, fracturing operations are carried out directly. The specific process and related data are as follows: (1) Under fracturing conditions, with a depth of 4m 3 Injecting fracturing fluid at a rate of / min at 26℃ for 2 hours, the temperature at a depth of 3580m decreased from 125℃ to 46.2℃. (Temperature change is as follows) Figure 5 As shown in the figure, the temperature difference reached 78.8℃. Figure 5 The diagram shows the reservoir temperature at different vertical depths under different construction measures in working condition 2. The Undisturbed-2 curve corresponds to the reservoir temperature at different vertical depths calculated according to the low temperature gradient when no construction measures are taken. The FRAC-4M3 / MIN-2 curve corresponds to the reservoir temperature at different vertical depths calculated when fracturing fluid is directly pumped in without pre-circulating the low temperature fluid in the wellbore before fracturing operation.

[0079] (2) Under the effect of this temperature difference, the closed-loop annular pressure is reduced by about 64 MPa according to the method of the embodiment of this application.

[0080] (3) The vertical depth of the reservoir is 3580m. The calculated reservoir pressure is about 35.8MPa. The pressure inside the tubing is 71.6MPa. At this time, the closed annular pressure is -28.2MPa. At this time, the tubing is subjected to an internal pressure difference of 99.8MPa, the casing is subjected to an external pressure difference of 64MPa, and the lower packer is subjected to a pressure difference of 99.8MPa.

[0081] (4) Calculate the internal pressure resistance safety factor of the tubing to 1.07, the external extrusion resistance safety factor of the casing to 0.76, and the differential pressure resistance safety factor of the packer to 0.69. To ensure construction safety, the following must be met: the internal pressure resistance safety factor is greater than 1.1 and the external extrusion resistance safety factor is greater than 1.125.

[0082] Calculations show that if the closed-loop annular pressure is not predicted using the method described in this application, and fracturing operations are carried out directly, there is a risk of tubing rupture, casing crushing, and packer puncture.

[0083] Figure 6 A structural block diagram of a closed-loop air parameter prediction device for a fracturing well dual packer according to an embodiment of this application is shown, as follows: Figure 6 As shown, the device includes: The first construction module 610 is adapted to construct a first mapping relationship formula corresponding to the total volume change of the closed annular fluid based on the mapping relationship between the volume change of the closed annular fluid caused by the action of key factors and a first parameter; and to construct a second mapping relationship formula corresponding to the total volume change of the closed annular fluid based on the mapping relationship between the volume change of the closed annular fluid caused by well structure deformation and a second parameter; wherein the first parameter and the second parameter both include at least one parameter among the closed annular parameters; The second construction module 620 is adapted to combine the first mapping relation and the second mapping relation to construct a target relation about the closed loop space parameter; The prediction module 630 is adapted to calculate the predicted values ​​of other parameters in the closed loop empty parameters based on the parameter value of at least one parameter in the closed loop empty parameters and the target relation.

[0084] In one alternative approach, the closed-loop parameters include: closed-loop temperature variation and closed-loop pressure variation.

[0085] In an alternative embodiment, the first building module 610 is further adapted to: Based on the fluid thermal expansion calculation method, a mapping relationship is constructed between the volume change of a closed-loop air fluid caused by the action of key factors and the first parameter; Based on the calculation method of the thermal deformation effect of the pipe body, a mapping relationship between the change in the closed annulus volume caused by the deformation of the well structure and the second parameter is constructed.

[0086] In an alternative approach, the key factors include temperature and pressure; the first building block 610 is further adapted to: Based on the fact that the total volume change of the closed-loop air fluid is equal to the difference between the volume change of the closed-loop air fluid due to temperature and the volume change of the closed-loop air fluid due to pressure, a first mapping relationship corresponding to the total volume change of the closed-loop air fluid is constructed.

[0087] In one alternative embodiment, the well structure includes tubing and other structures, said other structures including casing, cement sheath, and formation; the first building module 610 is further adapted to: Based on the fact that the total volume change of the closed-loop fluid is equal to the sum of the volume change of the closed-loop fluid caused by the tubing deformation and the volume change of the closed-loop fluid caused by the other structures, a second mapping relationship is constructed corresponding to the total volume change of the closed-loop fluid.

[0088] In one alternative approach, the volume change of the closed annular fluid due to temperature is related to the temperature change of the closed annular fluid, and the volume change of the closed annular fluid due to pressure is related to the pressure change of the closed annular fluid; the volume change of the closed annular fluid caused by tubing deformation is related to the temperature change and pressure change of the closed annular fluid, and the volume change of the closed annular fluid caused by other structures is related to the temperature change of the closed annular fluid.

[0089] The descriptions of the above modules refer to the corresponding descriptions in the method embodiments, and will not be repeated here.

[0090] According to the embodiment of this application, the device for predicting the closed annulus parameters of a dual packer in a fracturing well is as follows: Based on the mapping relationship between the volume change of the closed annulus fluid caused by key factors and a first parameter, a first mapping relationship is constructed corresponding to the total volume change of the closed annulus fluid; based on the mapping relationship between the volume change of the closed annulus fluid caused by well structure deformation and a second parameter, a second mapping relationship is constructed corresponding to the total volume change of the closed annulus fluid; combining the first and second mapping relationships, a target relationship for the closed annulus parameters is constructed; based on the parameter value of at least one parameter in the closed annulus parameters and the target relationship, the predicted values ​​of other parameters in the closed annulus parameters are calculated. This method provides a way to predict the closed annulus parameters during fracturing operations, effectively solving the problem of difficulty in predicting the closed annulus parameters of dual packers in high-temperature and high-pressure fracturing wells. It can efficiently and accurately predict the closed annulus parameters during fracturing operations and can be applied to the strength verification analysis of dual packers and tubing during fracturing, helping to predict construction risks in advance and improve the safety of the tubing during fracturing operations.

[0091] This application provides a non-volatile computer storage medium storing at least one executable instruction or computer program that enables a processor to perform the operation corresponding to the trap annulus parameter prediction method for the fracturing well dual packer in any of the above method embodiments.

[0092] This application provides a computer program product, which includes at least one executable instruction or computer program that enables a processor to perform the operation corresponding to the trap annulus parameter prediction method for the fracturing well dual packer in any of the above method embodiments.

[0093] Figure 7 The diagram shows a structural schematic of an embodiment of the computing device of this application. The specific embodiments of this application do not limit the specific implementation of the computing device.

[0094] like Figure 7 As shown, the computing device may include: a processor 702, a communications interface 704, a memory 706, and a communications bus 708.

[0095] The processor 702, communication interface 704, and memory 706 communicate with each other via communication bus 708. Communication interface 704 is used to communicate with other network elements, such as clients or other servers. Processor 702 executes program 710, specifically performing the relevant steps in the embodiment of the method for predicting the closed loop space parameters of a fracturing well dual packer used for calculating equipment.

[0096] Specifically, program 710 may include program code that includes computer operation instructions.

[0097] The processor 702 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application. The computing device includes one or more processors, which may be processors of the same type, such as one or more CPUs; or processors of different types, such as one or more CPUs and one or more ASICs.

[0098] Memory 706 is used to store program 710. Memory 706 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.

[0099] Specifically, program 710 can be used to cause processor 702 to execute the closed loop void parameter prediction method for the fracturing well dual packer in any of the above method embodiments. The specific implementation of each step in program 710 can be found in the corresponding steps and units described in the above embodiments of the fracturing well dual packer closed loop void parameter prediction, and will not be repeated here. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the above-described equipment and modules can be referred to the corresponding process descriptions in the foregoing method embodiments, and will not be repeated here.

[0100] The algorithms and displays provided herein are not inherently related to any particular computer, virtual system, or other device. Various general-purpose systems can also be used in conjunction with the teachings herein. The required structure for constructing such systems is apparent from the above description. Furthermore, the embodiments of this application are not directed to any particular programming language. It should be understood that the contents of the embodiments of this application described herein can be implemented using various programming languages, and the above description of specific languages ​​is for the purpose of disclosing the best implementation of the embodiments of this application.

[0101] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0102] Similarly, it should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various inventive aspects, in the foregoing description of exemplary embodiments of the present application, various features of the present application embodiments are sometimes grouped together into a single embodiment, figure, or description thereof. However, this approach to disclosure should not be construed as reflecting an intention that the claimed embodiments of the present application require more features than expressly recited in each claim. Rather, as reflected in the following claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the present application.

[0103] Those skilled in the art will understand that modules in the device of the embodiments can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiments can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components. Except where at least some of such features and / or processes or units are mutually exclusive, any combination can be used to combine all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or units of any method or device so disclosed. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose.

[0104] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are meant to be within the scope of the embodiments of this application and form different embodiments. For example, in the following claims, any one of the claimed embodiments can be used in any combination.

[0105] The various component embodiments of this application can be implemented in hardware, or as software modules running on one or more processors, or a combination thereof. Those skilled in the art will understand that microprocessors or digital signal processors (DSPs) can be used in practice to implement some or all of the functions of some or all of the components according to the embodiments of this application. The embodiments of this application can also be implemented as device or apparatus programs (e.g., computer programs and computer program products) for performing part or all of the methods described herein. Such programs implementing the embodiments of this application can be stored on a computer-readable medium, or can be in the form of one or more signals. Such signals can be downloaded from an Internet website, provided on a carrier signal, or provided in any other form.

[0106] It should be noted that the above embodiments are illustrative of the embodiments of this application and not limiting of the embodiments of this application, and those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. Embodiments of this application can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

Claims

1. A method for predicting the closed-loop air parameters of a dual packer in a fracturing well, characterized in that, include: Based on the mapping relationship between the volume change of the closed-loop air fluid caused by the action of key factors and the first parameter, a first mapping relationship corresponding to the total volume change of the closed-loop air fluid is constructed. Based on the mapping relationship between the change in the volume of the closed annulus caused by well structure deformation and the second parameter, a second mapping relationship corresponding to the change in the total fluid volume of the closed annulus is constructed; wherein, both the first parameter and the second parameter include at least one parameter among the closed annulus parameters; By combining the first mapping relation and the second mapping relation, a target relation is constructed regarding the closed loop space parameter of the loop. Based on the parameter value of at least one parameter in the closed loop empty parameters and the target relation, calculate the predicted values ​​of the other parameters in the closed loop empty parameters.

2. The method for predicting the closed-loop annulus parameters of a dual packer in a fracturing well according to claim 1, characterized in that, The closed-loop parameters include: closed-loop temperature change and closed-loop pressure change.

3. The method for predicting the closed-loop annulus parameters of a dual packer in a fracturing well according to claim 2, characterized in that, The method further includes: Based on the fluid thermal expansion calculation method, a mapping relationship is constructed between the volume change of a closed-loop air fluid caused by the action of key factors and the first parameter; Based on the calculation method of the thermal deformation effect of the pipe body, a mapping relationship between the change in the closed annulus volume caused by the deformation of the well structure and the second parameter is constructed.

4. The method for predicting the closed-loop annulus parameters of a dual packer in a fracturing well according to claim 1, characterized in that, The key factors include temperature and pressure; the construction of the first mapping relationship corresponding to the total volume change of the closed-loop air fluid based on the mapping relationship between the volume change of the closed-loop air fluid caused by the key factors and the first parameter further includes: Based on the fact that the total volume change of the closed-loop air fluid is equal to the difference between the volume change of the closed-loop air fluid due to temperature and the volume change of the closed-loop air fluid due to pressure, a first mapping relationship corresponding to the total volume change of the closed-loop air fluid is constructed.

5. The method for predicting the closed-loop annulus parameters of a dual packer in a fracturing well according to claim 1, characterized in that, The well structure includes tubing and other structures, including casing, cement sheath, and formation; the construction of the second mapping relationship corresponding to the change in the total fluid volume of the closed annulus due to well structure deformation and the second parameter further includes: Based on the fact that the total volume change of the closed-loop fluid is equal to the sum of the volume change of the closed-loop fluid caused by the tubing deformation and the volume change of the closed-loop fluid caused by the other structures, a second mapping relationship is constructed corresponding to the total volume change of the closed-loop fluid.

6. The method for predicting the closed-loop annulus parameters of a dual packer in a fracturing well according to claim 2, characterized in that, The volume change of the closed annular fluid due to temperature is related to the temperature change of the closed annular fluid, and the volume change of the closed annular fluid due to pressure is related to the pressure change of the closed annular fluid. The volume change of the closed annular fluid caused by tubing deformation is related to the temperature change and pressure change of the closed annular fluid. The volume change of the closed annular fluid caused by other structures is related to the temperature change of the closed annular fluid.

7. A device for predicting the closed-loop air parameters of a dual packer in a fracturing well, characterized in that, include: The first construction module is adapted to construct a first mapping relationship formula corresponding to the total volume change of the closed annular fluid based on the mapping relationship between the volume change of the closed annular fluid caused by the action of key factors and a first parameter; and to construct a second mapping relationship formula corresponding to the total volume change of the closed annular fluid based on the mapping relationship between the volume change of the closed annular fluid caused by well structure deformation and a second parameter; wherein the first parameter and the second parameter both include at least one parameter among the closed annular parameters; The second construction module is adapted to combine the first mapping relation and the second mapping relation to construct a target relation about the closed loop space parameter; The prediction module is adapted to calculate the predicted values ​​of other parameters in the closed loop empty parameters based on the parameter values ​​of at least one parameter in the closed loop empty parameters and the target relation.

8. A computing device, characterized in that, include: The processor, memory, communication interface, and communication bus are provided, wherein the processor, memory, and communication interface communicate with each other via the communication bus. The memory is used to store at least one executable instruction, which causes the processor to perform the operation corresponding to the method for predicting the closed annulus parameters of a fracturing well dual packer as described in any one of claims 1-6.

9. A computer storage medium, characterized in that, The storage medium stores at least one executable instruction that causes the processor to perform the operation corresponding to the method for predicting the closed annulus parameters of a fracturing well dual packer as described in any one of claims 1-6.

10. A computer program product, characterized in that, It includes at least one executable instruction that causes the processor to perform the operation corresponding to the trap annulus parameter prediction method for the dual packer of a fractured well as described in any one of claims 1-6.

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