Method for evaluating packing capacity of carbon dioxide injection well cement sheath after fracturing

Abstract

The invention relates to the field of petroleum, in particular to a method for evaluating the packing capacity of a fractured carbon dioxide injection well cement sheath. The invention discloses a method for evaluating the packing capacity of a fractured carbon dioxide injection well cement sheath. The method comprises the following steps: preparing cylindrical set cement samples with the same number as fracturing construction sections, and carrying out pre-damage treatment; the packing pressure of each cylindrical set cement sample is tested, then the packing capacity of the cement sheath of each fracturing construction section of the injection well is calculated through a formula, and the minimum value is the packing capacity of the cement sheath of the injection well. According to the method, the problem of evaluating the packing capacity of the well cementation cement sheath of the carbon dioxide injection well after on-site fracturing is solved into equivalent evaluation of underground working condition reproduction through an indoor experiment mode, and compared with other technologies in the prior art, more well conditions can be considered, the operability is higher, and the method is closer to on-site reality.

Description

Technical Field

[0001] The invention relates to the field of petroleum, and in particular to a method for evaluating the sealing capacity of cement sheath of a carbon dioxide injection well after fracturing. Background Art

[0002] With the global emphasis on environmental protection and sustainable energy development, carbon dioxide flooding and storage technology (CCUS-EOR) has attracted widespread attention as an advanced technology that can both improve oil recovery and reduce carbon dioxide emissions. It has been widely implemented in my country. However, in the actual application of this technology, the sealing ability of the cement sheath is one of the key factors, which is directly related to the flooding effect and storage safety of carbon dioxide. Its technical logic is that carbon dioxide flooding and storage technology is to inject carbon dioxide into the oil layer along the injection well, improve the oil recovery rate of the oil field through its physical and chemical effects, and realize the geological storage of carbon dioxide. In this process, the failure of the wellbore integrity of the injection well is the direct cause of carbon dioxide leakage, and the in-situ damage and mechanical failure of the annular cementing cement sheath are the most fundamental cause and main threat to the long-term integrity of the carbon dioxide storage well. Therefore, evaluating the sealing ability of the cement sheath of the injection well is the key to ensuring technical safety and effectiveness. When evaluating the sealing ability of cement ring, for conventional wells, there are currently some test devices or evaluation methods, such as the patent "Method and system for determining the sealing ability of corroded cement ring of layered gas injection wells" with publication number CN119102602 A, and the patent "Dynamic sealing evaluation method of annular sealing system of CO2 injection wells" with publication number CN117849319B. However, at present, in some low-permeability areas (such as the Ordos Basin), when the CO2 flooding and storage project is implemented, it is necessary to convert old wells (oil wells or water injection wells) into CO2 injection wells. These old wells were all subjected to large-scale volume fracturing reservoir transformation at the beginning of production, and the cement stone has certain damage to varying degrees. For the evaluation of the sealing ability of cement rings of such wells, there are currently no simple, easy-to-use, effective solutions and reference methods. In particular, the gas channeling problem in the lower layers will seriously affect the regional CO2 flooding and storage effect, and will cause the normal production of other layer production wells, resulting in leakage risks of wells outside the monitoring range, affecting the safe operation of the overall CCUS-EOR project. Summary of the invention

[0003] The present invention aims to solve the above problems and proposes a method for evaluating the sealing capacity of cement sheath in carbon dioxide injection wells after fracturing.

[0004] The technical solution of the present invention is:

[0005] A method for evaluating the sealing capacity of cement sheath of a carbon dioxide injection well after fracturing, the method is as follows: Prepare cylindrical cement stone samples with the same number of fracturing sections as the injection well and perform pre-damage treatment; The specific process of pre-injury treatment is as follows: The upper and lower surfaces of a cylindrical cement stone sample are loaded with longitudinal force, and the two linear contact surfaces on the side are loaded with lateral force. After loading, unloading is completed, and loading and unloading are repeated. Second-rate, ; The longitudinal force and lateral force of each loading are calculated by the following formula: (1) in, is the number of fracturing stages of the injection well, dimensionless; is the number of loads, value ; dimensionless; For the The longitudinal force of the secondary load, KN; is the casing Poisson’s ratio; is the Poisson’s ratio of the cement ring on site; is the formation Poisson’s ratio; is the inner diameter of the casing, mm; is the inner diameter of the cement ring on site, mm; is the outer diameter of the on-site cement ring, mm; is the Young's modulus of the casing, GPa; is the Young’s modulus of the cement ring in situ, GPa; is the formation Young's modulus, GPa; For injection well Maximum construction pressure during fracturing in the fracturing construction section, MPa; For injection well Formation pressure around the wellbore during the fracturing construction period, MPa; (2) Where: For the Secondary loading lateral force, KN; Test The isolation pressure of a cylindrical cement stone sample; (3) Where: For injection well The sealing capacity of cement sheath in the fracturing construction section, MPa; For the The sealing pressure of a cylindrical cement stone sample, MPa; For injection well Wellbore length corresponding to the fracturing construction section, m; by The minimum value is the isolation capacity of the cement sheath of the injection well.

[0006] The invention also includes subjecting the pre-damaged cylindrical cement stone sample to corrosion test according to the temperature, pressure, fluid property and corrosion time of the carbon dioxide injection well, so as to obtain the corrosion time of the injection well after the injection of carbon dioxide. The sealing capacity of the cement sheath in the fracturing construction section is taken as the sealing capacity of the cement sheath in the injection well.

[0007] The cylindrical cement stone sample has a diameter of 2.5 cm and a height of 5 cm.

[0008] The specific preparation process of the cylindrical cement stone sample is as follows: cement slurry is prepared according to the cement slurry formula used in the construction of the injection well, and after the cement slurry is cured for 28 days, the primary cement stone is taken out to make a cylindrical cement stone sample with a diameter of 2.5 cm and a height of 5 cm.

[0009] The corrosion experiment was carried out in a carbon dioxide high temperature and high pressure curing kettle.

[0010] During the repeated loading and unloading, The number of loading times for a cylindrical cement stone sample is Second-rate, ; The longitudinal force, lateral force and loading time are different for each loading; Specifically: The loading parameters for the first loading are , and , the loading parameters for the second loading are , and ; until The loading parameters for each load are , and ;in, For injection well The time the maximum construction pressure is maintained during fracturing in the fracturing construction section.

[0011] The pre-damage treatment is performed by loading longitudinal force and lateral force through a triaxial pressure testing machine.

[0012] The said The sealing pressure of a cylindrical cement stone sample was obtained by porosimeter test. The test medium was carbon dioxide and the confining pressure was Formation pressure around the wellbore during fracturing operation .

[0013] The technical effects of the present invention are: (1) The difficulty of evaluating the sealing capacity of the cement sheath of the CO2 injection well after on-site fracturing has been resolved by conducting an equivalent evaluation by reproducing the downhole working conditions through indoor experiments. Compared with other existing technologies, more well conditions can be considered, the operability is stronger, and it is closer to the actual situation on site; (2) The method provided by the present invention fully considers the mechanical damage of fracturing to the cement sheath and the influence of such damage on CO2 isolation, and is more accurate and more applicable for the evaluation of injection wells that have been subjected to fracturing transformation in the early stage; (3) The present invention provides a method for specifically evaluating the CO2 isolation capacity of each fracturing construction section, especially for multi-stage volume fracturing wells with repeated loading and unloading, and can evaluate the CO2 crossflow potential between various layers, providing support for inter-well anti-crossflow research and targeted measures deployment for different wells in the region. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a top view of the cylindrical cement stone sample of the present invention when loaded.

[0015] Figure 2 It is a front view of the cylindrical cement stone sample of the present invention when loaded. DETAILED DESCRIPTION

[0016] Specific Example 1 - Evaluation of the original sealing capacity of the cement sheath of a carbon dioxide injection well after fracturing

[0017] A method for evaluating the sealing capacity of cement sheath of a carbon dioxide injection well after fracturing, the method is as follows:

[0018] Step 1: Based on the basic data of the injection well and the fracturing data, substitute into formula (1) to calculate the longitudinal force , calculate the lateral force according to formula (2) .

[0019] Step 2: Prepare cement slurry according to the cement slurry formula used in the injection well construction. After curing the cement slurry for 28 days, take out the primary cement stone and make cylindrical cement stone samples with a diameter of 2.5 cm and a height of 5 cm. The number of cylindrical cement stone samples is the same as the number of injection well fracturing construction sections. The cylindrical cement stone sample corresponds to the injection well Fracturing construction section.

[0020] Step 3: Pre-injury treatment: Using a triaxial compression testing machine, longitudinal forces were applied along the upper and lower surfaces of the first cylindrical cement stone sample. , and load the lateral force along the two linear contact surfaces on the side , maintenance time , unload after loading is completed; Using a triaxial compression testing machine, longitudinal forces were applied along the upper and lower surfaces of the second cylindrical cement stone sample. , and load the lateral force along the two linear contact surfaces on the side , maintenance time , unloading after loading; the second time the longitudinal force is loaded along the upper and lower surfaces of the second cylindrical cement stone sample , and load the lateral force along the two linear contact surfaces on the side , maintenance time , unload after loading is completed; Similarly, using a triaxial compression testing machine, The upper and lower surfaces of a cylindrical cement stone sample are loaded with longitudinal force. , and load the lateral force along the two linear contact surfaces on the side , maintenance time , unload after loading; the second time along the The upper and lower surfaces of a cylindrical cement stone sample are loaded with longitudinal force. , and load the lateral force along the two linear contact surfaces on the side , maintenance time , unload after loading; repeat loading and unloading until the Next along the The upper and lower surfaces of a cylindrical cement stone sample are loaded with longitudinal force. , and load the lateral force along the two linear contact surfaces on the side , maintenance time , unload after loading is complete.

[0021] Step 4: Use FYYC-1 type permeameter to test the The sealing pressure of a cylindrical cement stone sample The test medium is carbon dioxide, and the confining pressure is the injection well Formation pressure around the wellbore during fracturing operation .

[0022] Step 5: Calculate the injection well number using formula (3). Sealing capacity of cement sheath in fracturing construction section ,by The minimum value is the isolation capacity of the cement sheath of the injection well, and the isolation capacity at this time is the original isolation capacity of the cement sheath of the injection well.

[0023] Specific Example 2 - Evaluation of the sealing capacity of the cement sheath after a period of CO2 injection in a post-fracture CO2 injection well

[0024] A method for evaluating the sealing capacity of cement sheath of a carbon dioxide injection well after fracturing, the method is as follows:

[0025] Step 1 to step 3 are the same as in specific embodiment 1.

[0026] Step 4: Place all pre-damaged cylindrical cement stone samples into a carbon dioxide high-temperature and high-pressure curing kettle, and conduct corrosion tests according to the temperature, pressure, fluid properties and corrosion time of the carbon dioxide injection well.

[0027] Step 5: Use FYYC-1 type permeameter to test the The sealing pressure of a cylindrical cement stone sample The test medium is carbon dioxide, and the confining pressure is the injection well Formation pressure around the wellbore during fracturing operation .

[0028] Step 6: Calculate the injection well number using formula (3). Sealing capacity of cement sheath in fracturing construction section ,by The minimum value is the isolation capacity of the cement sheath of the injection well.

[0029] Specific application case 1--WX29 well

[0030] The original isolation capacity of the cement sheath of a well in the operation scope of a CCUS-EOR project in China was evaluated. The well is WX29. The Young's modulus of the cement sheath in the well is The Poisson's ratio of the cement ring is 12GPa. 0.25, the inner diameter of the casing The inner diameter of the cement ring is 124.3 mm. 139.7mm, Young's modulus of the casing is 210GPa, the Poisson's ratio of the casing is 0.30, the formation Poisson's ratio is 0.23, the Young's modulus of the formation The injection well was divided into 4 sections for volume fracturing during fracturing construction. The relevant fracturing parameters are shown in Table 1: Table 1 Fracturing related parameters .

[0031] A method for evaluating the sealing capacity of cement sheath of a carbon dioxide injection well after fracturing, the method is as follows:

[0032] Step 1: Based on the basic data and fracturing data of Well WX29, substitute into formula (1) to calculate the longitudinal force , calculate the lateral force according to formula (2) ; The results are shown in Table 2: Table 2 Longitudinal force and lateral force Calculation results .

[0033] Step 2: Prepare cement slurry according to the cement slurry formula used in the construction of Well WX29. After curing the cement slurry for 28 days, take out the primary cement stone and make 4 cylindrical cement stone samples with a diameter of 2.5 cm and a height of 5 cm.

[0034] Step 3: Pre-injury treatment: A TCYJ triaxial compression testing machine was used to apply a longitudinal force of 3.90 KN ( ), and at the same time, a lateral force of 1.52KN is applied along the two linear contact surfaces on the side ( ), and maintain for 2 minutes ( ), unload after loading is completed; A TCYJ triaxial compression testing machine was used to apply a longitudinal force of 3.90 KN ( ), and at the same time, a lateral force of 1.52KN is applied along the two linear contact surfaces on the side ( ), and maintain for 2 minutes ( ), unloading after loading; the second time, a longitudinal force of 3.56KN was loaded along the upper and lower surfaces of the second cylindrical cement stone sample ( ), and at the same time, a lateral force of 1.17KN is applied along the two linear contact surfaces on the side ( ), and maintain for 5min ( ), unload after loading is completed; A TCYJ triaxial compression testing machine was used to apply a longitudinal force of 3.90 KN ( ), and at the same time, a lateral force of 1.52KN is applied along the two linear contact surfaces on the side ( ), and maintain for 2 minutes ( ), unloading after loading; the second time, a longitudinal force of 3.56KN was loaded along the upper and lower surfaces of the third cylindrical cement stone sample ( ), and at the same time, a lateral force of 1.17KN is applied along the two linear contact surfaces on the side ( ), and maintain for 5min ( ), unloading after loading; the third time, a longitudinal force of 3.64KN was loaded along the upper and lower surfaces of the third cylindrical cement stone sample ( ), and at the same time, a lateral force of 2.02KN is applied along the two linear contact surfaces on the side ( ), and maintain for 3min ( ), unload after loading is completed; A TCYJ triaxial compression testing machine was used to apply a longitudinal force of 3.90 KN ( ), and at the same time, a lateral force of 1.52KN is applied along the two linear contact surfaces on the side ( ), and maintain for 2 minutes ( ), unloading after loading; the second time, a longitudinal force of 3.56KN was loaded along the upper and lower surfaces of the fourth cylindrical cement stone sample ( ), and at the same time, a lateral force of 1.17KN is applied along the two linear contact surfaces on the side ( ), and maintain for 5min ( ), unloading after loading; the third time, a longitudinal force of 3.64KN was loaded along the upper and lower surfaces of the fourth cylindrical cement stone sample ( ), and at the same time, a lateral force of 2.02KN is applied along the two linear contact surfaces on the side ( ), and maintain for 3min ( ), unloading after loading; the fourth time, a longitudinal force of 3.28KN was loaded along the upper and lower surfaces of the fourth cylindrical cement stone sample ( ), and at the same time, a lateral force of 1.88KN is applied along the two linear contact surfaces on the side ( ), and maintain for 7min ( ), unload after loading is complete.

[0035] Step 4: Use FYYC-1 type permeameter to test the sealing pressure of 4 cylindrical cement stone samples The test medium is carbon dioxide, and the confining pressures are , the results are shown in Table 3: Table 3 Sealing pressure of cylindrical cement stone samples .

[0036] Step 5: Calculate the injection well number using formula (3). Sealing capacity of cement sheath in fracturing construction section The calculation results are shown in Table 4. The minimum value of is the isolation capacity of the cement sheath of the injection well, and the isolation capacity at this time is the original isolation capacity of the cement sheath of the injection well; Table 4 Packing capacity ; by , , and The minimum value in (27.47MPa) is the sealing capacity of the cement sheath of the injection well. At this time, the sealing capacity is the original sealing capacity of the cement sheath of the injection well.

[0037] From the above results, it can be seen that if this well is selected as an injection well for carbon dioxide injection, the maximum pressure should not exceed 27.47MPa, otherwise it may cause carbon dioxide to break through the layer of the fracturing construction section and then flow to other layers, causing oil recovery failure. The channeling pressures of the third, second and first sections of the fracturing are 27.65MPa, 28.48MPa and 39.36MPa respectively. This pressure value should be paid attention to during the later injection process.

[0038] Specific application case 2--ZL-3 well

[0039] A method for evaluating the sealing capacity of cement sheath in a post-fracture carbon dioxide injection well is provided. The sealing capacity of cement sheath in a post-fracture carbon dioxide injection well is evaluated after carbon dioxide injection has been carried out for a period of time. The specific steps are as follows.

[0040] The cement sheath isolation capacity of a well that was converted to CO2 injection after fracturing was evaluated within the operating scope of a CCUS-EOR project in China 90 days after gas injection. The well is ZL-3 well. The Young's modulus of the cement sheath at the site of the well is The Poisson's ratio of the cement sheath is 11 GPa. 0.23, the inner diameter of the casing The inner diameter of the cement ring is 124.3 mm. 139.7mm, Young's modulus of the casing is 210GPa, the Poisson's ratio of the casing is 0.30, the formation Poisson's ratio is 0.21, the Young's modulus of the formation The injection temperature of the injection well is 60°C, the maximum injection pressure is 16MPa, and the injection time is 90 days. Before the injection well is injected with carbon dioxide, the fracturing construction is divided into 3 sections for volume fracturing. The relevant fracturing parameters are shown in Table 5: Table 5 Fracturing related parameters .

[0041] A method for evaluating the sealing capacity of cement sheath of a carbon dioxide injection well after fracturing, the method is as follows:

[0042] Step 1: Based on the basic data and fracturing data of Well ZL-3, substitute into formula (1) to calculate the longitudinal force , calculate the lateral force according to formula (2) ; The results are shown in Table 6: Table 6 Longitudinal force and lateral force Calculation results .

[0043] Step 2: Prepare cement slurry according to the cement slurry formula used in the construction of ZL-3 well. After curing the cement slurry for 28 days, take out the primary cement stone and make three cylindrical cement stone samples with a diameter of 2.5 cm and a height of 5 cm.

[0044] Step 3: Pre-injury treatment: A TCYJ triaxial compression testing machine was used to apply a longitudinal force of 4.88KN ( ), and at the same time, a lateral force of 4.02KN is applied along the two linear contact surfaces on the side ( ), and maintain for 6 minutes ( ), unload after loading is completed; A TCYJ triaxial pressure testing machine was used to apply a longitudinal force of 4.88KN ( ), and at the same time, a lateral force of 4.02KN is applied along the two linear contact surfaces on the side ( ), and maintain for 6 minutes ( ), unloading after loading; the second time, a longitudinal force of 4.55KN was loaded along the upper and lower surfaces of the second cylindrical cement stone sample ( ), and at the same time, a lateral force of 3.31KN is applied along the two linear contact surfaces on the side ( ), and maintain for 4 minutes ( ), unload after loading is completed; A TCYJ triaxial compression testing machine was used to apply a longitudinal force of 4.88KN ( ), and at the same time, a lateral force of 4.02KN is applied along the two linear contact surfaces on the side ( ), and maintain for 6 minutes ( ), unloading after loading; the second time, a longitudinal force of 4.55KN was loaded along the upper and lower surfaces of the third cylindrical cement stone sample ( ), and at the same time, a lateral force of 3.31KN is applied along the two linear contact surfaces on the side ( ), and maintain for 4 minutes ( ), unloading after loading; the third time, a longitudinal force of 4.20KN was loaded along the upper and lower surfaces of the third cylindrical cement stone sample ( ), and at the same time, a lateral force of 2.85KN is applied along the two linear contact surfaces on the side ( ), and maintain for 8min ( ), unload after loading is complete.

[0045] Step 4: Place the three cylindrical cement stone samples after pre-damage treatment in a carbon dioxide high-temperature and high-pressure curing kettle, and conduct corrosion experiments according to the temperature (60°C), pressure (16MPa), fluid properties (CO2) and corrosion time (90 days) of the carbon dioxide injection well;

[0046] Step 5: Take out the three corroded cylindrical cement stone samples from the carbon dioxide high temperature and high pressure curing kettle, and use the FYYC-1 type pore permeability meter to test the sealing pressure of the three cylindrical cement stone samples. The test medium is carbon dioxide, and the confining pressures are , the results are shown in Table 7: Table 7 Sealing pressure of cylindrical cement stone samples .

[0047] Step 6: Calculate the injection well number using formula (3). Sealing capacity of cement sheath in fracturing construction section The calculation results are shown in Table 8. The minimum value of is the isolation capacity of the cement sheath of the injection well, and the results are shown in Table 8; Table 8 Packing capacity ; by , and The minimum value in (25.31 MPa) is the sealing capacity of the cement sheath in the injection well.

[0048] Through the above test, it can be seen that the injection pressure of the well is less than the calculated isolation pressure of each section, indicating that under the current operation mode, the lower layers of the well will not cause interlayer crossflow and will not adversely affect the exploitation of other layers. This is consistent with the situation found by monitoring the adjacent wells of the well, indicating that the calculation method of the present invention is accurate and practical. At the same time, the result can also provide technical support for the next step of safe operation. The maximum limit pressure of the gas injection in the well should be 25.31MPa.

Claims

1. A method for evaluating the sealing capacity of cement sheath of carbon dioxide injection well after fracturing, characterized in that: Here is how: Prepare cylindrical cement stone samples with the same number of fracturing sections as the injection well and perform pre-damage treatment; The specific process of pre-injury treatment is as follows: The upper and lower surfaces of a cylindrical cement stone sample are loaded with longitudinal force, and the two linear contact surfaces on the side are loaded with lateral force. After loading, unloading is completed, and loading and unloading are repeated. Second-rate, ; The longitudinal force and lateral force of each loading are calculated by the following formula: （1） in, is the number of fracturing construction stages of the injection well, dimensionless; is the number of loads, value ; dimensionless; For the The longitudinal force of the secondary load, KN; is the casing Poisson’s ratio; is the Poisson’s ratio of the cement ring on site; is the formation Poisson’s ratio; is the inner diameter of the casing, mm; is the inner diameter of the cement ring on site, mm; is the outer diameter of the on-site cement ring, mm; is the Young's modulus of the casing, GPa; is the Young’s modulus of the cement ring in situ, GPa; is the formation Young's modulus, GPa; For injection well Maximum construction pressure during fracturing in the fracturing construction section, MPa; For injection well Formation pressure around the wellbore during the fracturing construction period, MPa; （2） Where: For the Secondary loading lateral force, KN; Test The isolation pressure of a cylindrical cement stone sample; （3） Where: For injection well The sealing capacity of cement sheath in the fracturing construction section, MPa; For the The sealing pressure of a cylindrical cement stone sample, MPa; For injection well Wellbore length corresponding to the fracturing construction section, m; by The minimum value is the isolation capacity of the cement sheath of the injection well.

2. The method for evaluating the sealing capacity of cement sheath of carbon dioxide injection well after fracturing according to claim 1, characterized in that: The invention also includes subjecting the pre-damaged cylindrical cement stone sample to corrosion test according to the temperature, pressure, fluid property and corrosion time of the carbon dioxide injection well, so as to obtain the corrosion time of the injection well after the injection of carbon dioxide. The sealing capacity of the cement sheath in the fracturing construction section is taken as the sealing capacity of the cement sheath in the injection well.

3. The method for evaluating the sealing capacity of cement sheath of carbon dioxide injection well after fracturing according to claim 1 or 2, characterized in that: The cylindrical cement stone sample has a diameter of 2.5 cm and a height of 5 cm.

4. The method for evaluating the sealing capacity of cement sheath of carbon dioxide injection well after fracturing according to claim 3, characterized in that: The specific preparation process of the cylindrical cement stone sample is as follows: cement slurry is prepared according to the cement slurry formula used in the construction of the injection well, and after the cement slurry is cured for 28 days, the primary cement stone is taken out to make a cylindrical cement stone sample with a diameter of 2.5 cm and a height of 5 cm.

5. The method for evaluating the sealing capacity of cement sheath of carbon dioxide injection well after fracturing according to claim 2, characterized in that: The corrosion experiment was carried out in a carbon dioxide high temperature and high pressure curing kettle.

6. The method for evaluating the sealing capacity of cement sheath of carbon dioxide injection well after fracturing according to claim 1, characterized in that: During the repeated loading and unloading, The number of loading times for a cylindrical cement stone sample is Second-rate, ; The longitudinal force, lateral force and loading time are different for each loading; Specifically: The loading parameters for the first loading are , and , the loading parameters for the second loading are , and ; until The loading parameters for each load are , and ;in, For injection well The time the maximum construction pressure is maintained during fracturing in the fracturing construction section.

7. The method for evaluating the sealing capacity of cement sheath of carbon dioxide injection well after fracturing according to claim 1, characterized in that: The pre-damage treatment is performed by loading longitudinal force and lateral force through a triaxial pressure testing machine.

8. The method for evaluating the sealing capacity of cement sheath of carbon dioxide injection well after fracturing according to claim 1, characterized in that: The said The sealing pressure of a cylindrical cement stone sample was obtained by porosimeter test. The test medium was carbon dioxide and the confining pressure was Formation pressure around the wellbore during fracturing operation .

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