Casing pipe running-in method based on casing pipe thread safety and effect evaluation method

Abstract

The invention relates to the technical field of oil and gas well drilling and completion engineering construction design, in particular to a casing tripping-in method and effect evaluation method based on casing thread safety, which comprises the following steps: predicting the maximum friction resistance of casing tripping-in, the bending position of a casing and the bending degree of the casing, and determining the hanging load of a wellhead casing; determining the relation between the bending degree of the wellhead casing and the applied axial force; determining the maximum impulse value generated by rapid tripping-in of the wellhead casing in case of resistance; the maximum safe speed value of casing running is determined; the well mouth casing pipe descends at the speed not larger than the safety maximum speed value until the well mouth casing pipe meets resistance and cannot continue to descend; the casing pipe is lifted by 20 m from a well mouth, and the casing pipe is lowered by 3-5 m at the speed not larger than the safety maximum speed value v; a pump is started on the ground, and high-pressure circulating drilling fluid enters the casing pipe to move The well mouth sleeve column pipe continues to run at the speed not larger than the maximum safe speed value v till running is conducted for 8-10 m, and the pump is stopped on the ground; and the wellhead sleeve continues to move downwards. Through the tripping-in method and the effect evaluation method, the safety of tripping-in of the casing pipe is ensured.

Description

Technical Field

[0001] This invention relates to the field of construction design technology for oil and gas well drilling and completion engineering, and in particular to a casing running method and effect evaluation method based on casing thread safety. Background Technology

[0002] With the development of drilling technology for complex well structures, the complex variations in well inclination and azimuth angles with well depth have made conventional casing installation methods difficult. Rotary casing installation technology can effectively solve the problem of casing installation. The engineering difficulty during rotary casing installation is related to the frictional resistance, which is related to the surface roughness of the casing, the roughness of the wellbore, the curvature within the well, changes in the wellbore trajectory, and the casing installation speed. In existing horizontal wells, the horizontal section is often long, resulting in high frictional resistance during casing installation and posing safety hazards. Currently, floating casing installation technology is used. During casing installation at the wellhead, two special joints are connected between the casing strings in the horizontal section. The casing between these joints is not filled with mud, but only with air. Because the horizontal section of the casing is empty of mud and only contains air, its weight is reduced, frictional resistance is decreased, and casing installation becomes easier. However, the floating casing technology is expensive, and during use, it has been found that due to the continuous accumulation of sand beds in the horizontal section of the wellbore, the friction increases, necessitating the opening of the floating coupling for circulation. As air is expelled from the casing, the horizontal section loses its floating effect, and the friction of continuing to run the casing increases significantly, making further running more difficult. Moreover, the floating coupling short section often cannot be opened in the field, affecting production.

[0003] Regarding the safe installation of casing on site, firstly, the complex geological structure and large variations in formation occurrence in the area lead to complex wellbore trajectories, large water-to-vertical ratios, and poor wellbore cleanliness, posing significant technical challenges to the efficient installation of production casing in ultra-long horizontal well sections.

[0004] Secondly, in order to analyze the impact of factors such as wellbore trajectory changes, wellbore cleaning control, wellbore stability, and centralizers on the safe running of ultra-deep and long horizontal well casing, a real-time downhole friction monitoring model was established by combining comprehensive logging data.

[0005] Third, based on the measured data from the field of horizontal well casing installation in the shale gas block, and by comprehensively utilizing the modified three-dimensional soft rod tubing friction calculation model and data statistical analysis method, key factors such as centralizer, wellbore curvature, well inclination, well diameter, and friction coefficient are analyzed.

[0006] The research results show that: ① Cumulative wellbore curvature can more intuitively reflect the degree of influence of casing running friction than wellbore curvature. When the cumulative wellbore curvature is greater than 3.7° / 30m, the casing running friction begins to increase rapidly. Therefore, for horizontal wells with large wellbore curvature, it is necessary to avoid frequent adjustments to the wellbore trajectory and reduce the difficulty of casing running. ② The wellbore diameter variation coefficient can accurately describe the variation range of the wellbore diameter along the horizontal wellbore direction. For horizontal wells with complex geological conditions and severe wellbore diameter reduction and collapse, statistical analysis of the wellbore diameter variation coefficient to assess the influence of casing running friction can effectively improve the prediction accuracy. When the wellbore diameter variation coefficient is less than 2%, the influence of casing running friction is small. When the wellbore diameter variation coefficient is greater than or equal to 2%, the influence of casing running friction is large.

[0007] Fourth, based on the actual stress on the curved section of the casing, a calculation model for the maximum allowable wellbore curvature under various tensile conditions was derived. Various operating conditions during casing installation were analyzed, and the analysis concluded that lifting the casing was the most dangerous condition. The maximum wellbore curvature under this condition is the maximum wellbore curvature required to ensure safe casing installation in a specific curved section. This resulted in a new maximum wellbore curvature calculation model applicable to any tensile condition.

[0008] Fifth, since the advent of extended reach horizontal wells, ensuring the safe installation of casing has always been a technical challenge. The high frictional resistance of casing in extended reach horizontal wells makes it easy for the casing to stick and fail to be installed smoothly, which brings difficulties to cementing operations. Based on extensive research and experiments, experts at home and abroad believe that floating casing technology is one of the most effective methods to solve the difficulties of casing installation.

[0009] The above information addresses the issue of safe casing installation in large well groups, mainly proposing methods and measures from aspects such as field measures, tool selection, well trajectory optimization, wellbore cleaning, theoretical calculations, and well trajectory control. However, it does not systematically analyze the optimal casing installation measures for well sections with high friction. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention proposes a casing insertion method and an effect evaluation method based on casing thread safety, ensuring the safety of casing insertion.

[0011] This invention is achieved by adopting the following technical solution:

[0012] A casing insertion method based on casing thread safety includes the following steps:

[0013] S1. By collecting field data, predict the maximum frictional resistance during casing installation, the location of casing bending, and the corresponding degree of casing bending, and determine the casing suspension weight m at the wellhead.

[0014] S2. Select the appropriate wellhead casing and conduct a simulation test of fatigue failure of the bent thread seal in a horizontal well environment to determine the relationship between the degree of bending of the wellhead casing and the applied axial force.

[0015] S3. Determine the applied axial force F based on the predicted casing bending degree, and determine the maximum impulse value E that can be generated when the wellhead casing is rapidly lowered into the ground when it encounters resistance.

[0016] S4. Determine the maximum safe speed value v for casing insertion:

[0017]

[0018] S5. Apply the casing thread sealant as required, and thread the casing at the wellhead with the required torque; lower the wellhead casing at a speed not exceeding the maximum safe speed value v until the wellhead casing encounters resistance and cannot be lowered further.

[0019] S6. Raise the casing 20m from the wellhead and lower the casing 3-5m at a speed not exceeding the maximum safe speed value v;

[0020] S7. The surface pump is started, and the high-pressure circulating drilling fluid enters the casing and descends;

[0021] S8. Continue to lower the wellhead casing at a speed not exceeding the maximum safe speed value v until the wellhead casing has been lowered 8-10m, then stop the pump at the surface.

[0022] S9. The circulating hydraulic pressure disappears, and the wellhead casing continues to descend;

[0023] S 10 If the casing at the wellhead encounters obstruction and cannot be lowered further, repeat steps S7 to S9 until the entire casing is lowered.

[0024] The method for determining the maximum impulse value E is as follows:

[0025] E = F * α

[0026] In the formula, F is the applied axial force, and α is the scaling factor.

[0027] The casing is lowered at a speed of 0.5-0.6 m / s.

[0028] The suspended weight m of the wellhead casing is greater than the predicted maximum frictional resistance during casing installation.

[0029] In step S1, the maximum frictional resistance during casing installation, the location of casing bending, and the degree of casing bending are predicted through finite element analysis.

[0030] The field data in step S1 includes the actual drilling trajectory of the wellbore, the formation encountered during drilling, the reduced diameter well section, the wellbore enlargement rate, and the distribution of well sections where well progress is obstructed.

[0031] Step S2 is also used to determine the maximum number of bends in the casing; during the lowering process, the number of times the casing is lifted and lowered at the same position is controlled to be less than the maximum number of bends in the casing.

[0032] The scaling factor α is set to 85%.

[0033] An evaluation method for the effectiveness of a casing installation method based on casing thread safety is proposed. Cementing pressure test is conducted, and if the pressure drop is less than the rated value within 30 minutes, it proves that the casing thread seal is qualified.

[0034] If the cementing test pressure is 35 MPa, then the rated value is 0.5 MPa.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. This method can pass through relatively narrow wellbores by repeatedly changing the curvature of the downhole casing, ensuring smooth casing installation, high sealing safety of the casing threads, reducing the probability of casing thread seal failure in shale oil horizontal wells, guaranteeing a high overall drilling speed, and providing technical support for on-site construction.

[0037] Specifically, during the casing run-down process when encountering resistance at the wellhead, the casing's bending at the resistance point will vary due to differences in running speed, load changes, and pump activation timing. This invention predicts the maximum frictional resistance during casing run-down in advance, selects a suitable casing, and then controls the running speed based on the predicted bending location and degree of bending. After lifting the casing, the running speed is controlled in multiple stages, and the pump activation timing is comprehensively judged. Better pump activation timing allows for better control of the casing's bending degree, improving the safe running of horizontal well casing.

[0038] 2. This invention combines finite element analysis and simulation experiments, enabling the casing installation to be tailored to the actual scenario, making casing installation safer.

[0039] 3. In the process of casing installation, this invention comprehensively considers the performance of the casing itself and the actual installation environment, and comprehensively considers the maximum impulse value, the number of lifting and lowering operations, the casing installation speed, the pump start-up timing, the casing installation method and speed control to ensure the safety of casing installation.

[0040] 4. The effect evaluation method of the present invention is simple and efficient. Attached Figure Description

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, wherein:

[0042] Figure 1 This is a schematic diagram showing the complete transformation of the sleeve in this invention. Detailed Implementation

[0043] Example 1

[0044] As a basic embodiment of the present invention, the present invention includes a casing insertion method based on casing thread safety, comprising the following steps:

[0045] Step S1. By collecting field data, predict the maximum frictional resistance during casing installation, the location of casing bending, and the corresponding degree of casing bending. Based on the predicted maximum frictional resistance during casing installation, determine the casing suspension weight (m) at the wellhead.

[0046] Step S2. Select the appropriate wellhead casing and conduct a simulation test of fatigue failure of the bent thread seal in a horizontal well environment to determine the relationship between the degree of bending of the wellhead casing and the applied axial force.

[0047] Step S3. Determine the applied axial force F based on the predicted casing bending degree, and determine the maximum impulse value E that can be generated when the wellhead casing is rapidly lowered into the ground if it encounters resistance.

[0048] Step S4. Determine the maximum safe speed value v for casing insertion:

[0049]

[0050] Step S5. Apply the casing thread sealant as required, and thread the casing at the wellhead with the required torque. Run the casing at the wellhead at a speed not exceeding the maximum safe speed value v until the casing encounters resistance and cannot be run further.

[0051] Step S6. Raise the casing 20m from the wellhead and lower the casing at a speed not exceeding the maximum safe speed value v for 3-5m.

[0052] Step S7. Start the pump on the ground and the high-pressure circulating drilling fluid enters the casing and descends.

[0053] Step S8. Continue to run the wellhead casing at a speed not exceeding the maximum safe speed value v until the wellhead casing has been run for 8-10m, then stop the pump at the surface.

[0054] Step S9. The circulating hydraulic pressure disappears, and the wellhead casing continues to descend.

[0055] Step S 10 If the casing at the wellhead encounters obstruction and cannot be lowered further, repeat steps S7 to S9 until the entire casing is lowered.

[0056] Example 2

[0057] As a preferred embodiment of the present invention, the present invention includes a casing insertion method based on casing thread safety, comprising the following steps:

[0058] Step S1. By collecting field data, predict the maximum frictional resistance during casing installation, the location of casing bending, and the corresponding degree of casing bending. Based on the predicted maximum frictional resistance during casing installation, determine the casing suspension weight (m) at the wellhead.

[0059] Step S2. Select the appropriate wellhead casing and conduct a simulation test of fatigue failure of the bent thread seal in a horizontal well environment to determine the relationship between the degree of bending of the wellhead casing and the applied axial force.

[0060] Step S3. Determine the applied axial force F based on the predicted casing bending degree, and determine the maximum impulse value E that can be generated when the wellhead casing is rapidly lowered due to resistance:

[0061] E = F * α

[0062] In the formula, α is the scaling factor.

[0063] Step S4. Determine the maximum safe speed value v for casing insertion:

[0064]

[0065] Step S5. Apply the casing thread sealant as required, and thread the casing at the wellhead with the required torque. Run the casing at the wellhead at a speed not exceeding the maximum safe speed value v until the casing encounters resistance and cannot be run further.

[0066] Step S6. Raise the casing 20m from the wellhead and lower the casing at a speed of 0.5-0.6m / s for 3-5m.

[0067] Step S7. Start the pump on the ground and the high-pressure circulating drilling fluid enters the casing and descends.

[0068] Step S8. Continue to run the wellhead casing at a speed of 0.5-0.6 m / s until the wellhead casing has been run 8-10 m, then stop the pump at the surface.

[0069] Step S9. The circulating hydraulic pressure disappears, and the wellhead casing continues to descend.

[0070] Step S 10 If the casing at the wellhead encounters obstruction and cannot be lowered further, repeat steps S7 to S9 until the entire casing is lowered.

[0071] Example 3

[0072] In another preferred embodiment of the present invention, the present invention includes a casing insertion method based on casing thread safety, comprising the following steps:

[0073] Step S1. By collecting field data, predict the maximum frictional resistance during casing installation, the location of casing bends, and the corresponding degree of bends using finite element analysis. The field data includes the actual drilling trajectory, encountered formations, reduced-diameter sections, wellbore enlargement rate, and distribution of obstructed sections during well cleaning. Based on the predicted maximum frictional resistance during casing installation, determine the casing suspension weight *m* at the wellhead. The casing suspension weight *m* at the wellhead is greater than the predicted maximum frictional resistance during casing installation.

[0074] Step S2. Select the appropriate wellhead casing and conduct a simulation test of fatigue failure of the bent thread seal in a horizontal well environment to determine the relationship between the degree of wellhead casing bending and the applied axial force, as well as the maximum number of bending cycles of the casing.

[0075] Step S3. Determine the applied axial force F based on the predicted casing bending degree, and determine the maximum impulse value E that can be generated when the wellhead casing is rapidly lowered into the ground if it encounters resistance.

[0076] Step S4. Determine the maximum safe speed value v for casing insertion:

[0077]

[0078] Step S5. Apply the casing thread sealant as required, and thread the casing at the wellhead with the required torque. Run the casing at the wellhead at a speed not exceeding the maximum safe speed value v until the casing encounters resistance and cannot be run further.

[0079] Step S6. Raise the casing 20m from the wellhead and lower the casing at a speed not exceeding the maximum safe speed value v for 3-5m.

[0080] Step S7. Start the pump on the ground and the high-pressure circulating drilling fluid enters the casing and descends.

[0081] Step S8. Continue to run the wellhead casing at a speed not exceeding the maximum safe speed value v until the wellhead casing has been run for 8-10m, then stop the pump at the surface.

[0082] Step S9. The circulating hydraulic pressure disappears, and the wellhead casing continues to descend.

[0083] Step S 10 If the wellhead casing encounters obstruction and cannot be lowered further, repeat steps S7 to S9 until the entire casing is lowered. During the lowering process, the number of times the casing is pulled up and lowered should be less than the maximum number of bends the casing can withstand.

[0084] Example 4

[0085] As the preferred embodiment of the present invention, the present invention includes a casing insertion method based on casing thread safety, comprising the following steps:

[0086] Step S1. By collecting field data, the finite element method is used to predict the maximum frictional resistance during casing installation, the location of casing bending, and the corresponding degree of casing bending. The field data includes the actual drilling trajectory, encountered formations, reduced-diameter sections, wellbore enlargement rate, and distribution of obstructed sections during well cleaning. Specifically, the horizontal well with casing installed has a vertical depth of 2000m, a build-up point of 550-650m, an offset distance of 500-700m, and a maximum wellbore curvature of 5.5 degrees / 30m, preparing for the analysis of casing thread failure due to obstruction during casing installation.

[0087] Based on the predicted maximum frictional resistance during casing installation, the suspended weight (m) of the wellhead casing is determined. Specifically, the suspended weight (m) of the wellhead casing is greater than the predicted maximum frictional resistance during casing installation. The predicted maximum frictional resistance during casing installation could be 30 tons, and the suspended weight of the wellhead casing could be 50 tons. Considering the site conditions, the casing can be a special threaded casing with an outer diameter of 139.7 mm, a wall thickness of 7.72 mm, and a steel grade of P110.

[0088] The predicted wellbore bend locations are within 200m above and below the build-up point and in the wellbore enlargement section; the degree of bend in the casing is equal to the degree of wellbore enlargement.

[0089] Step S2. Select the appropriate wellhead casing and conduct a simulation test of fatigue failure of the bent thread seal in a horizontal well environment to determine the relationship between the degree of wellhead casing bending and the applied axial force, as well as the maximum number of bending cycles of the casing.

[0090] This experiment demonstrates that a special casing with an outer diameter of 139.7 mm, a wall thickness of 7.72 mm, and a steel grade of P110, exhibits reliable thread sealing after undergoing 70 tons of axial compression and a radial bend of 12 mm, repeated 50 times. The impulse generated during rapid lowering of the casing into the wellhead when encountering resistance is less than 85% of the axial force applied in the laboratory experiment.

[0091] Step S3. Determine the applied axial force F based on the predicted casing bending degree, and determine the maximum impulse value E that can be generated when the wellhead casing is rapidly lowered due to resistance:

[0092] E = F * α

[0093] In the formula, F is the applied axial force, and α is the scaling factor. In this embodiment, the value of α is 85%.

[0094] Step S4. Determine the maximum safe speed value v for casing insertion:

[0095]

[0096] Step S5. Apply the required sealing grease to the casing threads, and then thread the casing at the wellhead to the required torque. To ensure safe casing thread sealing during the casing running process, the impulse generated when the casing encounters resistance during running must be less than 85% of the 70-ton axial force applied in the laboratory experiment. The casing should be run at a speed not exceeding the maximum safe speed value v until it encounters resistance and cannot be continued. Specifically, a speed of 0.5-0.6 m / s is acceptable.

[0097] Step S6. Raise the casing 20m from the wellhead and lower the casing at a speed of 0.5-0.6m / s for 3-5m.

[0098] Step S7. Refer to the instruction manual appendix. Figure 1 The pump is started on the surface, and high-pressure circulating drilling fluid enters the casing and descends. The circulating hydraulic force acts on the descending, curved casing, forcing the curved section of the casing to change its curvature.

[0099] Step S8. Continue to run the wellhead casing at a speed of 0.5-0.6 m / s. The guide shoe at the bottom of the downhole casing can easily pass through the obstructed section of the well until the wellhead casing is run 8-10 m. Stop pumping at the surface.

[0100] Step S9. The circulating hydraulic force disappears, and the "rigidity" of the casing in the obstructed section decreases; the bending shape changes slightly, and the wellhead casing continues to descend.

[0101] Step S 10 If the casing encounters obstruction at the wellhead and cannot be lowered further, repeat steps S7 to S9 until the entire casing is lowered. During the lowering process, it is also necessary to control the number of times the casing is pulled up and lowered at the same location to be less than the maximum number of bends the casing can withstand.

[0102] Because the casing runs at different speeds, loads, and pump activation times during the casing run-down process when encountering obstruction, the bending of the casing at the obstruction point will vary. Therefore, this embodiment considers both the obstruction issue during casing run-down and the timing of surface pump activation. The timing of surface pump activation can be determined based on a combination of finite element analysis and simulation experiments to improve the safe running of horizontal well casing.

[0103] This invention also includes a method for evaluating the effectiveness of casing installation based on casing thread safety. After the above steps are completed and the casing is installed, a cementing pressure test is performed. If the pressure drop is less than the rated value within 30 minutes, it proves that the casing thread seal is qualified and the well can be successfully handed over. The cementing pressure test can be 35 MPa, while the rated value is 0.5 MPa.

[0104] In summary, any other corresponding modifications made by those skilled in the art after reading this invention document, without requiring creative mental effort, based on the technical solutions and concepts of this invention, are all within the scope of protection of this invention.

Claims

1. A casing insertion method based on casing thread safety, characterized in that: Includes the following steps: S1. By collecting field data, predict the maximum frictional resistance during casing installation, the location of casing bending, and the corresponding degree of casing bending, and determine the casing suspension weight m at the wellhead. S2. Select the appropriate wellhead casing and conduct a simulation test of fatigue failure of the bent thread seal in a horizontal well environment to determine the relationship between the degree of bending of the wellhead casing and the applied axial force. S3. Determine the applied axial force F based on the predicted casing bending degree, and determine the maximum impulse value E that can be generated when the wellhead casing is rapidly lowered into the ground when it encounters resistance. S4. Determine the maximum safe speed value v for casing insertion: S5. Apply the casing thread sealant as required, and thread the casing at the wellhead with the required torque; lower the wellhead casing at a speed not exceeding the maximum safe speed value v until it encounters resistance and cannot be lowered further; S6. Raise the casing 20m from the wellhead, and lower the casing 3-5m at a speed not exceeding the maximum safe speed value v. S7. The surface pump is started, and the high-pressure circulating drilling fluid enters the casing and descends; S8. Continue to lower the wellhead casing at a speed not exceeding the maximum safe speed value v until the wellhead casing has been lowered 8-10m, then stop the pump at the surface. S9. The circulating hydraulic pressure disappears, and the wellhead casing continues to descend; S 10 If the casing at the wellhead encounters obstruction and cannot be lowered further, repeat steps S7 to S9 until the entire casing is lowered.

2. The casing insertion method based on casing thread safety according to claim 1, characterized in that: The method for determining the maximum impulse value E is as follows: E = F * α In the formula, F is the applied axial force, and α is the scaling factor.

3. The casing insertion method based on casing thread safety according to claim 2, characterized in that: The casing is lowered at a speed of 0.5-0.6 m / s.

4. The casing insertion method based on casing thread safety according to claim 3, characterized in that: The suspended weight m of the wellhead casing is greater than the predicted maximum frictional resistance during casing installation.

5. A casing insertion method based on casing thread safety according to claim 3, characterized in that: In step S1, the maximum frictional resistance during casing installation, the location of casing bending, and the degree of casing bending are predicted through finite element analysis.

6. The casing insertion method based on casing thread safety according to claim 3, characterized in that: The field data in step S1 includes the actual drilling trajectory of the wellbore, the formation encountered during drilling, the reduced diameter well section, the wellbore enlargement rate, and the distribution of well sections where well progress is obstructed.

7. The casing insertion method based on casing thread safety according to claim 3, characterized in that: Step S2 is also used to determine the maximum number of bends in the casing; during the lowering process, the number of times the casing is lifted and lowered at the same position is controlled to be less than the maximum number of bends in the casing.

8. The casing insertion method based on casing thread safety according to claim 2, characterized in that: The scaling factor α is set to 85%.

9. The method for evaluating the effectiveness of a casing insertion method based on casing thread safety according to any one of claims 1 to 8, characterized in that: If the pressure drop is less than the rated value within 30 minutes during a cementing pressure test, it proves that the casing thread seal is qualified.

10. The method for evaluating the effectiveness of a casing insertion method based on casing thread safety according to claim 9, characterized in that: If the cementing test pressure is 35 MPa, then the rated value is 0.5 MPa.

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