Pressure control method for well cementation operation, sealing device and application of sealing device

Abstract

The invention relates to the technical field of oil and gas well drilling and completion, in particular to a pressure control method for well cementation operation, a sealing device and application of the sealing device, and the pressure control method comprises the steps that in the well cementation operation process, whether overflow occurs or not is judged; if yes, the shut-in casing pressure is calculated; the equivalent mud density or the equivalent completion fluid density for balancing the formation pressure is calculated according to the shut-in casing pressure, and the needed equivalent wellhead return pressure is calculated; annular sealing of the wellhead is kept, and the equivalent wellhead return pressure obtained through calculation in the above step is maintained at the wellhead by controlling the opening degree of a throttling valve; and the slurry density or the well completion fluid density is gradually increased, the opening degree of the throttling valve is correspondingly controlled, and the well cementation operation process continues. By means of the pressure control method, the sealing device and the application of the pressure control method, the sealing device and the sealing device, the annulus pressure profile of a shaft can be controlled in the well cementation operation, manual intervention on downhole pressure abnormity in multiple links such as casing running and well cementation can be achieved, the well control risk of the well cementation operation is greatly improved, and the well cementation operation quality is improved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well drilling and completion technology, and in particular to a pressure control method, sealing device and its application for cementing operations. Background Technology

[0002] Currently, domestic standards and technical specifications for the oil extraction industry clearly stipulate that before running casing, the gate blowout preventer should be replaced with a gate that matches the size of the casing to be run and pressure tested.

[0003] The purpose of replacing the gate blowout preventer (BOP) is to quickly control the annulus in case of overflow during casing running, minimizing the entry of formation fluids into the annulus and preventing well control accidents. The use of gate blowout preventers and their associated processes has a long history, but these methods have the following drawbacks:

[0004] 1. Disassemble the original single-gate blowout preventer gate core, replace it with a gate core that matches the casing size, and then conduct a pressure test. Only after the pressure test is successful can the casing be installed. The above process is time-consuming and labor-intensive, and the long wait for the open well increases the well control risk. The average time for replacing the valve core is more than 4 hours.

[0005] 2. In the event of formation overflow, the existing process can only control pressure through a choke manifold and perform weighted circulation well control. The existing choke manifold design is only an emergency device and does not meet the special requirements of long-term, high-volume circulation.

[0006] 3. In recent years, with the large-scale development of exploration wells, narrow safety density windows such as overflow, leakage and overflow in the same layer are often encountered in areas with abnormal formation pressure. The polygonality and complexity of formations are becoming increasingly complex, and the existing casing gate blowout preventers cannot meet the increasingly complex working conditions.

[0007] 4. With the increasing demand for oil and gas resources, the scale of deep and ultra-deep well exploration is also expanding, creating an urgent need for the technology of single-pass backflow of cement slurry in cementing operations. This necessitates the use of low-density and ultra-low-density cement slurry technology to balance formation pressure, thus creating a pressing need for pressure-controlled cementing technology. However, current equipment and technology cannot meet the requirements of pressure-controlled cementing.

[0008] In the prior art, a Chinese invention patent document with publication number CN115324483A and publication date November 11, 2022, is disclosed. The technical solution disclosed in this patent document is as follows: a method for fully sealed and pressure-controlled casing installation, including designing a sealing device at the wellhead, the sealing device including a pipe section connected to the wellhead, an upper sealing structure and a lower sealing structure disposed within the pipe section; when installing casing with a centralizer, the upper sealing structure is opened, and the lower sealing structure is used to close the annulus, and the casing is installed normally; when the casing centralizer is installed into the cavity between the upper and lower sealing structures, the upper sealing structure is closed; when the upper sealing structure completes the cavity closure, the lower sealing structure is opened, and the casing installation continues; after the casing centralizer is installed as a whole into the wellbore, the lower sealing structure is closed again; and a pressure relief valve is used to release the pressurized drilling fluid in the cavity.

[0009] The above technical solution will have the following problems in actual use: it is impossible to control the annular pressure profile during cementing operations. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention proposes a pressure control method, sealing device, and their application for cementing operations. This method enables control of the annular pressure profile during cementing operations and allows for human intervention in downhole pressure anomalies at multiple stages, including casing installation and cementing. This significantly improves well control risk management and enhances the quality of cementing operations.

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

[0012] A pressure control method for cementing operations includes the following steps:

[0013] S1. During cementing operations, determine whether an overflow has occurred; if so, proceed to step S2.

[0014] S2. Calculate the shut-in casing pressure;

[0015] S3. Calculate the equivalent mud density or equivalent completion fluid density to balance the formation pressure based on the shut-in casing pressure:

[0016]

[0017] In the formula, ρ 当 P is the equivalent mud density or equivalent completion fluid density. 耗 For the annular cycle pressure loss, P 关井 Where is the shut-in casing pressure, g is the acceleration due to gravity, and H is the vertical depth of the well.

[0018] S4. Calculate the required equivalent wellhead back pressure P 回 :

[0019] P_return = (ρ_when - ρ_actual)·g·H + P_consumption

[0020] In the formula, ρ 实 This refers to the actual mud density or the actual completion fluid density.

[0021] S5. Maintain the wellhead annulus seal by controlling the throttle valve opening to maintain the equivalent wellhead back pressure P calculated in step S4. 回 ;

[0022] S6. Gradually increase the density of the mud or completion fluid, and control the opening of the throttle valve accordingly to continue the cementing operation.

[0023] The cementing operation includes casing installation and cement slurry injection.

[0024] When the fixed operation process is casing installation, step S6 includes:

[0025] S 611 Continue the casing installation operation;

[0026] S 612 Increase the density of the completion fluid;

[0027] S 613 Replace the low-density completion fluid in the well by circulating it. During the replacement process, gradually open the throttle valve to the fully open position until the overflow is eliminated.

[0028] S 614 Continue the casing installation.

[0029] If obstruction is encountered during the casing installation, the obstruction can be cleared by circulating the pump, rotating the casing, and raising and lowering the casing.

[0030] When the fixed operation process is cement grouting, step S6 includes:

[0031] S 621 Gradually increase the density of the cement mud until it can balance the formation pressure. During this process, gradually open the throttle valve to reduce the wellhead back pressure.

[0032] S 622 Normal cement injection operation;

[0033] S 623 Maintain a tight seal in the wellhead annulus and allow it to set.

[0034] S 624 After Hou Ning finishes, the assignment is complete.

[0035] If step S 621If increasing the density of cement mud to the upper limit cannot balance the formation pressure, the wellhead back pressure value is maintained at the wellhead by controlling the opening of the throttle valve, and the wellhead is kept pressurized for solidification until the solidification ends.

[0036] When the wellhead is under pressure and the back pressure is set, record the back pressure value at the wellhead and adjust the back pressure in a timely manner according to the calculation method in step S4.

[0037] A sealing device for cementing operations, wherein the sealing device is used in the above-mentioned pressure control method to maintain a wellhead annular seal.

[0038] The sealing device includes a housing, a rotating assembly, and a casing string; the lower end of the housing is connected to the wellhead blowout preventer assembly; the casing string includes a casing and a centralizer fitted onto the casing, the centralizer including several spaced-apart centralizing blocks; the rotating assembly is disposed within the housing and is capable of relative rotational movement with the housing; the rotating assembly contains an upper rubber core and a lower rubber core for sealing the casing; the upper and lower rubber cores are arranged one above the other, and the distance between the upper and lower rubber cores is greater than the length of the centralizer.

[0039] An application of a sealing device for cementing operations, where obstruction is encountered during casing operations, and the obstruction is eliminated by starting a pump for circulation, rotating the casing, and lifting the casing.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. This pressure control method can control the annular pressure profile of the wellbore, enabling human intervention in downhole pressure anomalies at multiple stages such as casing running and cementing, significantly improving well control risk and quality during well completion operations.

[0042] 2. The pressure control method of the present invention is not only applicable to casing operation, but can also be used to control pressure during the cement injection stage, showing obvious advantages in terms of versatility and practicality.

[0043] 3. The sealing device in this invention ensures that the wellbore annulus remains sealed during lifting, lowering, or rotation, allowing control of the wellhead back pressure via the choke manifold to control the wellbore profile pressure. Furthermore, this sealing process eliminates the need for a switch control unit, simplifying operation and increasing efficiency.

[0044] 4. Currently, during on-site construction, if the casing is obstructed or jammed during the casing installation process, it is quite troublesome to rotate, lift, lower, and circulate the mud inside and outside the casing on-site. This sealing device can safely and conveniently achieve the above functions.

[0045] 5. When using a low-density or ultra-low-density single-stage backfill column design for deep or ultra-deep wells, if the cement slurry density is insufficient to balance the formation pressure, this sealing device and pressure control method can be used to provide back pressure to the wellhead in a timely manner to balance the formation pressure, ensure well control safety, reduce formation fluid intrusion into the wellbore, and improve cementing quality.

[0046] 6. When completing wells in narrow density safety window areas, if a sudden overflow occurs during casing running or cementing, this sealing device and pressure control method can be quickly used to provide back pressure to the wellhead, thereby balancing formation pressure, ensuring well control safety during casing running and cementing, and reducing well control risks. Attached Figure Description

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, wherein:

[0048] Figure 1 This is a schematic diagram of the sealing device in this invention;

[0049] Figure 2 This is a schematic diagram of the rotating assembly in this invention;

[0050] Figure 3 This is a schematic diagram of the sleeve string structure in this invention;

[0051] Marked in the image:

[0052] 1. Housing, 2. Rotating assembly, 3. Sleeve string, 4. Sleeve, 5. Centralizer, 6. Centralizer block, 7. Upper rubber core, 8. Lower rubber core. Detailed Implementation

[0053] Example 1

[0054] As a basic embodiment of the present invention, the present invention includes a pressure control method for cementing operations, comprising the following steps:

[0055] S1. During the cementing operation, determine whether an overflow has occurred; if so, proceed to step S2.

[0056] S2. Calculate the shut-in casing pressure.

[0057] S3. Calculate the equivalent mud density or equivalent completion fluid density to balance the formation pressure based on the shut-in casing pressure:

[0058]

[0059] In the formula, ρ 当 P is the equivalent mud density or equivalent completion fluid density. 耗 For the annular cycle pressure loss, P 关井 denoted as shut-in casing pressure, g as gravitational acceleration, and H as well depth.

[0060] S4. Calculate the required equivalent wellhead back pressure P 回 :

[0061] P_return = (ρ_when - ρ_actual)·g·H + P_consumption

[0062] In the formula, ρ 实 This refers to the actual mud density or the actual completion fluid density.

[0063] S5. Maintain the wellhead annulus seal by controlling the throttle valve opening to maintain the equivalent wellhead back pressure P calculated in step S4. 回 .

[0064] S6. Gradually increase the density of the mud or completion fluid, and control the opening of the throttle valve accordingly to continue the cementing operation.

[0065] Example 2

[0066] In a preferred embodiment of the present invention, the present invention includes a pressure control method for cementing operations, comprising the following steps:

[0067] S1. During the cementing operation, determine whether an overflow has occurred; if so, proceed to step S2. Specifically, the cementing operation may be a casing installation operation.

[0068] S2. Calculate the shut-in casing pressure.

[0069] S3. Calculate the equivalent completion fluid density based on the shut-in casing pressure to balance the formation pressure:

[0070]

[0071] In the formula, ρ_dang is the equivalent completion fluid density, P_consumption is the annular circulation pressure loss, P_shut-in is the shut-in casing pressure, g is the gravitational acceleration, and H is the vertical well depth.

[0072] S4. Calculate the required equivalent wellhead back pressure P 回 :

[0073] P_return = (ρ_when - ρ_actual)·g·H + P_consumption

[0074] In the formula, ρ 实 This represents the actual completion fluid density.

[0075] S5. Maintain the wellhead annulus seal by controlling the throttle valve opening to maintain the equivalent wellhead back pressure P calculated in step S4. 回 .

[0076] S6. Gradually increase the density of the completion fluid and correspondingly control the choke valve opening to continue the cementing operation. Specifically, this includes the following steps:

[0077] S611 Continue the casing installation.

[0078] S 612 Increase the density of the completion fluid.

[0079] S 613 Replace the low-density completion fluid in the well in a circulating manner. During the replacement process, gradually open the throttle valve to the fully open position until the overflow is eliminated.

[0080] S 614 Continue the casing installation.

[0081] Example 3

[0082] In another preferred embodiment of the present invention, the present invention includes a pressure control method for cementing operations, comprising the following steps:

[0083] S1. During the cementing operation, determine whether an overflow has occurred; if so, proceed to step S2. The cementing operation is a cement slurry injection operation.

[0084] S2. Calculate the shut-in casing pressure.

[0085] S3. Calculate the equivalent mud density to balance the formation pressure based on the shut-in casing pressure:

[0086]

[0087] In the formula, ρ_dang is the equivalent mud density, P_consumption is the annular circulation pressure loss, P_shut-in is the shut-in casing pressure, g is the gravitational acceleration, and H is the vertical well depth.

[0088] S4. Calculate the required equivalent wellhead back pressure P 回 :

[0089] P_return = (ρ_when - ρ_actual)·g·H + P_consumption

[0090] In the formula, ρ 实 This refers to the actual mud density;

[0091] S5. Maintain the wellhead annulus seal by controlling the throttle valve opening to maintain the equivalent wellhead back pressure P calculated in step S4. 回 .

[0092] S6. Gradually increase the mud density and correspondingly control the throttle valve opening to continue the cementing operation. Specifically, this includes the following steps:

[0093] S 621 Gradually increase the density of the cement mud, and in the process, gradually and simultaneously open the throttle valve to reduce the wellhead back pressure.

[0094] S 622 Normal cement injection operation.

[0095] S 623 Maintain a wellhead annulus seal and allow it to solidify.

[0096] S 624 After Hou Ning finishes, the assignment is complete.

[0097] Example 4

[0098] In another preferred embodiment of the present invention, the present invention includes a sealing device for cementing operations, the sealing device comprising a housing 1, a rotating assembly 2, and a casing string 3. The lower end of the housing 1 is connected to a blowout preventer assembly at the wellhead. The casing string 3 includes a casing 4 and a centralizer 5 fitted onto the casing 4, the centralizer 5 including a plurality of spaced-apart centralizing blocks 6. The rotating assembly 2 is disposed within the housing 1 and is capable of relative rotational movement with the housing 1. The rotating assembly 2 is provided with an upper rubber core 7 and a lower rubber core 8 for sealing the casing 4. The upper rubber core 7 and the lower rubber core 8 are arranged one above the other, and the distance between the upper rubber core 7 and the lower rubber core 8 is greater than the length of the centralizer 5.

[0099] Example 5

[0100] As the preferred embodiment of the present invention, the present invention includes a sealing device for cementing operations, as described in the appendix to the specification. Figure 1 ~Instruction manual attached Figure 3 The sealing device includes a housing 1, a rotating assembly 2, and a casing string 3. The lower end of the housing 1 is connected to the wellhead blowout preventer assembly. The casing string 3 includes a casing 4 and a centralizer 5 fitted onto the casing 4. The centralizer 5 includes a centralizer body and several centralizer blocks 6 spaced apart on the centralizer body. Each centralizer block 6 protrudes outward from the centralizer body, forming a channel between adjacent centralizer blocks 6. The rotating assembly 2 is housed within the housing 1 and can rotate relative to the housing 1. The rotating assembly 2 contains an upper rubber core 7 and a lower rubber core 8 for sealing the casing 4. The upper rubber core 7 and the lower rubber core 8 are arranged one above the other, and the distance between them is greater than the length of the centralizer 5.

[0101] When the lower sleeve 4 is in operation, the sleeve string 3 can freely pass through the rotating assembly 2. When the centralizer 5 is above the upper end of the rotating assembly 2, the upper rubber core 7 and the lower rubber core 8 simultaneously seal the sleeve 4. When the centralizer 5 is passing through the upper rubber core 7, the upper rubber core 7 loses its sealing effect, and the lower rubber core 8 seals the sleeve 4. When the centralizer 5 passes through the upper rubber core 7 and is between the upper rubber core 7 and the lower rubber core 8, both rubber cores simultaneously seal the sleeve 4. When the rubber core passes through the lower rubber core 8, the upper rubber core 7 seals the sleeve 4. When the centralizer 5 passes through the lower rubber core 8, both rubber cores simultaneously seal the sleeve 4.

[0102] In all four cases mentioned above, the annulus of the wellbore can be kept in a sealed state, and the back pressure at the wellhead can be controlled by the choke manifold to achieve the purpose of controlling the pressure in the wellbore profile.

[0103] Therefore, the aforementioned sealing device can be used in pressure control methods for cementing operations to ensure wellhead annular sealing. Specifically, this embodiment may include a pressure control method for cementing operations, wherein the cementing operation may include casing installation and cement slurry injection.

[0104] When cementing operations involve casing installation, a pressure control method for cementing operations specifically includes the following steps:

[0105] S1. Install the sealing device, debug and pressure test it to achieve normal operating conditions. During the lowering of the sleeve, determine whether overflow occurs; if so, proceed to step S2.

[0106] S2. Calculate the shut-in casing pressure P 关井 If the shut-in casing pressure exceeds the maximum pressure that the sealing device can withstand, the casing blowout preventer is shut off and the well kill procedure is initiated; if the shut-in casing pressure is less than the maximum pressure that the sealing device can withstand, the controlled pressure casing running process is initiated. The maximum pressure that can withstand is, for example, 9 MPa.

[0107] S3. Calculate the equivalent completion fluid density based on the shut-in casing pressure to balance the formation pressure:

[0108]

[0109] In the formula, ρ_dang is the equivalent completion fluid density, P_consumption is the annular circulation pressure loss, P_shut-in is the shut-in casing pressure, g is the gravitational acceleration, and H is the vertical well depth.

[0110] S4. Calculate the required equivalent wellhead back pressure P 回 :

[0111] P_return = (ρ_when - ρ_actual)·g·H + P_consumption

[0112] In the formula, ρ 实 This represents the actual completion fluid density.

[0113] S5. Open the sealing device to maintain the wellhead annulus seal. By controlling the opening of the throttle valve, maintain the equivalent wellhead back pressure P calculated in step S4 at the wellhead. 回 .

[0114] S6. Gradually increase the density of the completion fluid, and control the choke valve opening according to the calculation method in step S4 to continue the cementing operation. Specifically, this includes the following steps:

[0115] S 611 Continue the casing installation operation;

[0116] S 612 Increase the density of the completion fluid;

[0117] S 613 Circulate and replace the low-density completion fluid in the well. During the replacement process, according to the calculation method in step S4, gradually open the throttle valve to the fully open state until the overflow is eliminated.

[0118] S 614 Close the sealing device and continue the casing installation.

[0119] During the casing installation process, the sealing device helps to eliminate obstructions through pump circulation, rotation, lifting and lowering.

[0120] When cementing operations involve injecting cement slurry, a pressure control method for cementing operations specifically includes the following steps:

[0121] S1. Install the sealing device, debug and test the pressure to achieve normal operating conditions. During the cement grouting process, determine whether overflow occurs; if so, proceed to step S2 to start the throttling and pressure control process.

[0122] S2. Calculate the shut-in casing pressure P 关井 .

[0123] S3. Calculate the equivalent mud density to balance the formation pressure based on the shut-in casing pressure:

[0124]

[0125] In the formula, ρ_dang is the equivalent mud density, P_consumption is the annular circulation pressure loss, P_shut-in is the shut-in casing pressure, g is the gravitational acceleration, and H is the vertical well depth.

[0126] S4. Calculate the required equivalent wellhead back pressure P 回 :

[0127] P_return = (ρ_when - ρ_actual)·g·H + P_consumption

[0128] In the formula, ρ 实 This represents the actual mud density.

[0129] S5. Open the sealing device to maintain the wellhead annulus seal. By gradually controlling the opening of the throttle valve, maintain the equivalent wellhead back pressure P calculated in step S4 at the wellhead. 回 .

[0130] S6. Gradually increase the mud density and control the throttle valve opening according to the calculation method in step S4 to continue the cementing operation. Specifically, this includes the following steps:

[0131] S 621Gradually increase the mud density until it can balance the formation pressure. During this process, the throttle valve opening is gradually and synchronously opened according to the calculation method in step S4 to reduce the wellhead back pressure.

[0132] S 622 Normal cement injection operation.

[0133] S 623 Maintain a tight seal at the wellhead annulus and allow it to set.

[0134] S 624 After Hou Ning finishes, the assignment is complete.

[0135] When increasing the mud density to the upper limit fails to balance the formation pressure, the wellhead back pressure is maintained at a corresponding value by controlling the throttle valve opening, keeping the wellhead pressurized for solidification until solidification ends. During the pressurized solidification process, the wellhead back pressure value is recorded, and the back pressure is adjusted promptly according to the calculation method in step S4 to prevent downhole leakage and to avoid adjusting the back pressure value beyond the maximum allowable back pressure value.

[0136] 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 pressure control method for cementing operations, characterized in that: Includes the following steps: S1. During cementing operations, determine whether an overflow has occurred; if so, proceed to step S2. S2. Calculate the shut-in casing pressure; S3. Calculate the equivalent mud density or equivalent completion fluid density to balance the formation pressure based on the shut-in casing pressure: In the formula, ρ 当 P is the equivalent mud density or equivalent completion fluid density. 耗 For the annular cycle pressure loss, P 关井 Where is the shut-in casing pressure, g is the acceleration due to gravity, and H is the vertical depth of the well. S4. Calculate the required equivalent wellhead back pressure P 回 : P_return = (ρ_when - ρ_actual)·g·H + P_consumption In the formula, ρ 实 This refers to the actual mud density or the actual completion fluid density. S5. Maintain the wellhead annulus seal by controlling the throttle valve opening to maintain the equivalent wellhead back pressure P calculated in step S4. 回 ; S6. Gradually increase the density of the mud or completion fluid, and control the opening of the throttle valve accordingly to continue the cementing operation.

2. The pressure control method for cementing operations according to claim 1, characterized in that: The cementing operation includes casing installation and cement slurry injection.

3. The pressure control method for cementing operations according to claim 2, characterized in that: When the fixed operation process is casing installation, step S6 includes: S 611 Continue the casing installation; S 612 Increase the density of the completion fluid; S 613 Replace the low-density completion fluid in the well by circulating it. During the replacement process, gradually open the throttle valve to the fully open position until the overflow is eliminated. S 614 Continue the casing installation.

4. The pressure control method for cementing operations according to claim 3, characterized in that: If obstruction is encountered during the casing installation, the obstruction can be cleared by circulating the pump, rotating the casing, and raising and lowering the casing.

5. A pressure control method for cementing operations according to claim 2, characterized in that: When the fixed operation process is cement grouting, step S6 includes: S 621 Gradually increase the density of the cement mud until it can balance the formation pressure. During this process, gradually open the throttle valve to reduce the wellhead back pressure. S 622 Normal cement injection operation; S 623 Maintain a tight seal in the wellhead annulus and allow it to set. S 624 After Hou Ning finishes, the assignment is complete.

6. A pressure control method for cementing operations according to claim 5, characterized in that: If step S 621 If increasing the density of cement mud to the upper limit cannot balance the formation pressure, the wellhead back pressure value is maintained at the wellhead by controlling the opening of the throttle valve, and the wellhead is kept pressurized for solidification until the solidification ends.

7. A pressure control method for cementing operations according to claim 6, characterized in that: When the wellhead is under pressure and the back pressure is set, record the back pressure value at the wellhead and adjust the back pressure in a timely manner according to the calculation method in step S4.

8. A sealing device for cementing operations, characterized in that: The sealing device is used in the pressure control method according to any one of claims 1 to 7 above to maintain the wellhead annulus seal.

9. A sealing device for cementing operations according to claim 8, characterized in that: The sealing device includes a housing (1), a rotating assembly (2), and a casing string (3); the lower end of the housing (1) is connected to the wellhead blowout preventer assembly; the casing string (3) includes a casing (4) and a centralizer (5) fitted onto the casing (4), the centralizer (5) including a plurality of spaced centralizer blocks (6); the rotating assembly (2) is located inside the housing (1) and can rotate relative to the housing (1); the rotating assembly (2) is provided with an upper rubber core (7) and a lower rubber core (8) for sealing the casing (4); the upper rubber core (7) and the lower rubber core (8) are arranged one above the other, and the distance between the upper rubber core (7) and the lower rubber core (8) is greater than the length of the centralizer (5).

10. The application of a sealing device for cementing operations according to claim 9, characterized in that: If obstruction is encountered during casing operation, the obstruction can be eliminated by starting the pump for circulation, rotating the casing, and lifting the casing.

Images