Casing mud line suspension system and feeding method and using method thereof

Abstract

The invention discloses a casing mud line suspension system and a feeding method and a using method thereof. The system comprises at least two sets of casing sealing assemblies which are coaxially arranged. The casing pipe sealing assembly comprises a sealing joint and a casing pipe hanger connected to the outer side of the sealing joint in a sleeving mode, the sealing joint and the casing pipe hanger are both made of metal materials, and the sealing joint and the casing pipe hanger are in interference fit to form metal sealing; all the casing sealing assemblies are sequentially arranged in a sleeving mode from inside to outside and extend in the axial direction, and the inner diameters of the casing hangers arranged from inside to outside are gradually increased; the adjacent casing pipe hangers are connected in a sealed mode. The sealing connector and the casing hanger are both made of metal materials, the casing hanger is connected to the outer side of the sealing connector in a sleeving mode, and the sealing connector and the casing hanger are in interference fit to form metal sealing, so that the purpose of sealing the sealing connector and the casing hanger is achieved, and compared with an independent sealing device, the cost is saved, and the sealing efficiency is improved. And the procedure of independent tripping-in is reduced, and the working efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of offshore oil production equipment, and in particular relates to a casing mudline suspension system. Background Art

[0002] The casing mudline suspension system is an important wellhead equipment in offshore oil and gas exploration and development. At present, the companies that design and manufacture casing mudline hanger systems mainly include Plexus in the UK and GE-vetco Gray, Cameron and Dril-quip in the United States. Sealing technology is the key technology of the casing mudline suspension system. The quality of sealing performance directly affects and determines the safety and reliability of the casing mudline suspension system.

[0003] The existing casing hanger and the joint are sealed by sealing rings, expansion tube seals, etc., but these all require a separate sealing structure, and when performing subsequent well operations, a separate process needs to be added to perform the sealing work. Summary of the invention

[0004] The object of the present invention is to provide a casing mudline suspension system and a delivery method and a use method thereof, so as to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above-mentioned purpose, the present invention provides a casing mudline suspension system, comprising at least two groups of coaxially arranged casing sealing assemblies; the casing sealing assembly comprises a sealing joint and a casing hanger sleeved on the outside of the sealing joint, the sealing joint and the casing hanger are both made of metal, and the sealing joint and the casing hanger are interference fit to form a metal seal; all the casing sealing assemblies are sleeved in sequence from the inside to the outside and extend in the axial direction, and the inner diameter of the casing hangers arranged from the inside to the outside gradually increases; adjacent casing hangers are sealed and connected.

[0006] Optionally, the sealing joint has a stepped shaft on one side close to the casing hanger, and a stepped hole is provided on the side of the casing hanger close to the sealing joint. The stepped shaft end of the sealing joint and the stepped hole end of the casing hanger have an interference fit, and the outer circumference of the stepped shaft end of the sealing joint and the inner surface of the stepped hole end of the casing hanger are both sealing surfaces.

[0007] Optionally, an interference fit section and a clearance fit section are provided between the sealing surface of the sealing joint and the sealing surface of the casing hanger, the interference fit section and the clearance fit section are arranged at intervals, and at least two interference fit sections are provided in each group of the casing sealing assembly.

[0008] Optionally, a sealing groove pointing to the axis of the sealing joint is formed on the sealing surface of the sealing joint on the interference fit section.

[0009] Optionally, a landing ring is provided on the circumferential outer side of the outermost casing hanger, and the landing ring is axially opened with a clamping hole for clamping the casing hanger, the inner diameter of the clamping hole is smaller than the outer diameter of the clamping position of the casing hanger, and the landing ring is detachably connected to the well wall where the casing hanger is located.

[0010] Optionally, a first fixed sealing layer is provided on the circumferential outer side of the landing ring and the casing hanger.

[0011] Optionally, the adjacent casing hangers are clamped, and a limiting protrusion is provided on the inner wall of one of the outer sides of the adjacent casing hangers, the inner diameter of the limiting protrusion is smaller than the outer diameter of the casing hanger clamping position located on the inner side, and a second fixed sealing layer is provided between the adjacent casing hangers and the limiting protrusion.

[0012] A casing mudline suspension system delivery method, comprising: S1. Determine the number and size of the casing seal assemblies according to the construction requirements, and install the sealing joints and the casing hangers in each set of the casing seal assemblies by interference fit to form a metal seal, and arrange the casing hangers from large to small according to the inner diameter of the casing hangers, namely, the first casing seal assembly, the second casing seal assembly, ... the Nth casing seal assembly; S2. Drilling at a designated location to a designated depth to form a first wellbore, sending the first casing sealing assembly to a designated location of the first wellbore using a casing, and performing cementing; S3. Drilling to a specified depth at the bottom of the first well to form a second well, sending the second casing seal assembly to a specified position of the second well using a casing, and sealingly connecting the casing hanger in the first casing seal assembly and the casing hanger in the second casing seal assembly; S4. Drilling at the bottom of the second well to a specified depth to form a third well, ...; Repeat step S3 until the Nth casing sealing assembly is installed at the specified position and the cementing operation is completed.

[0013] Optionally, in step S2, a fixing material is poured in the gap between the first casing sealing assembly and the first drilling well to form a first fixing sealing layer, thereby completing the cementing operation; In step S3, a fixing material is poured into the gap between the first casing sealing assembly and the second casing sealing assembly to form a second fixing sealing layer, thereby completing the cementing operation.

[0014] A casing mudline suspension system tie-back method, comprising: S1. Determine the number and size of tieback joints according to the original casing hangers in the drilling well, and arrange the tieback joints from large to small according to their inner diameters as the first tieback joint, the second tieback joint, ... the Nth tieback joint, and arrange the casing hangers from large to small according to their inner diameters as the first casing hanger, the second casing hanger, ... the Nth casing hanger; S2. Recover the well cap on the first casing hanger, connect the first tieback joint to the tieback casing and send both into the well, sleeve the first tieback joint and the first casing hanger, and install them by forming a metal seal through an interference fit to form a casing seal assembly; S3. Recover the well cap on the second casing hanger and tie the second back joint with ...; Repeat step S2 until the Nth tieback joint and the Nth casing hanger are sleeved and installed by metal sealing to form a casing sealing assembly, thus completing the tieback work.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: The sealing joint and casing hanger in the present invention are both made of metal. The casing hanger is sleeved on the outside of the sealing joint, and the sealing joint and the casing hanger are interference fit to form a metal seal, thereby achieving the purpose of sealing both the sealing joint and the casing hanger. Compared with the use of a separate sealing device, it not only saves costs, but also reduces the process of separate lowering, thereby improving work efficiency. In addition, the present invention selects a suitable number of casing sealing components according to different well conditions. All casing sealing components are sleeved and arranged in sequence from the inside to the outside and extend in the axial direction, that is, they are extended from the wellhead to the bottom of the well. The present invention forms a metal seal between the sealing joint and the casing hanger through an interference fit, and the adjacent casing hangers are sealed and connected, ensuring that the casing sealing component can work together with the casing to support the well wall, ensuring the normal operation of the entire oil well during the drilling process and after completion. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a schematic diagram of the structure of the casing hanger of the present invention; Figure 2 It is a schematic diagram of the structure of the casing mudline suspension system in the present invention in the delivery working condition; Figure 3 It is a schematic diagram of the structure of the casing mudline suspension system tieback working condition of the present invention; Figure 4 for Figure 2 A partial enlarged view of middle A.

[0018] Among them, 11, a first delivery joint, 12, a first casing hanger, 13, a first tieback joint, 21, a second delivery joint, 22, a second casing hanger, 23, a second tieback joint, 31, a third delivery joint, 32, a third casing hanger, 33, a third tieback joint, 4, a landing ring, 5, a limiting protrusion, and 6, a sealing groove. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0020] like Figure 1-Figure 4 As shown, the present invention provides a casing mudline suspension system, comprising at least two groups of coaxially arranged casing sealing assemblies; the casing sealing assembly comprises a sealing joint and a casing hanger sleeved on the outside of the sealing joint, the sealing joint and the casing hanger are both made of metal, and the sealing joint and the casing hanger are interference fit to form a metal seal; all casing sealing assemblies are sleeved in sequence from the inside to the outside and extend in the axial direction, and the inner diameter of the casing hanger arranged from the inside to the outside gradually increases; adjacent casing hangers are sealed and connected.

[0021] The sealing joint and casing hanger in the present invention are both made of metal. The casing hanger is sleeved on the outside of the sealing joint, and the sealing joint and the casing hanger are interference fit to form a metal seal, thereby achieving the purpose of sealing both the sealing joint and the casing hanger. Compared with the use of a separate sealing device, it not only saves costs, but also reduces the process of separate lowering, and improves work efficiency. In addition, according to different well working conditions, the present invention selects a suitable number of casing sealing components, and all casing sealing components are sleeved and arranged in sequence from the inside to the outside and extend in the axial direction, that is, they are extended from the wellhead to the bottom of the well. The present invention forms a metal seal between the sealing joint and the casing hanger through an interference fit, and the adjacent casing hangers are sealed and connected, ensuring that the casing sealing component can work together with the casing to support the well wall, ensuring the normal operation of the entire oil well during the drilling process and after completion; it solves the sealing problem of the casing mudline suspension system in the process of offshore oil and natural gas exploration and drilling, and provides safety and reliability for the use of the casing mudline suspension system.

[0022] In this embodiment, sealing surfaces are provided on the opposite sides of the sealing joint and the casing hanger. When torque is applied to the sealing joint, the sealing surfaces of the sealing joint and the casing hanger abut against each other, and the sealing joint and the casing hanger achieve interference fit to form a metal seal. In the present invention, the sealing joint and the casing hanger have an interference fit, that is, before the two are installed, the outer diameter of the sealing joint at the corresponding point is larger than the inner diameter of the sealing joint at the corresponding point. When the sealing joint and the casing hanger are installed, the casing hanger is sleeved on the end of the sealing joint, and the casing hanger is fixed. When torque is applied to the sealing joint, the sealing joint is rotated so that the sealing surfaces of the sealing joint and the casing hanger completely abut against each other, thereby achieving an interference fit. The sealing joint and the casing hanger can be made of metal materials such as stainless steel and alloy steel; the sealing joint and the casing hanger form a metal seal to ensure the sealing between the two, that is, the sealing of the space formed by the casing, the sealing joint and the casing hanger.

[0023] Preferably, the side of the sealing joint close to the casing hanger is a stepped shaft, and the side of the casing hanger close to the sealing joint is provided with a stepped hole. The stepped shaft end of the sealing joint and the stepped hole end of the casing hanger are interference fit, and the outer circumference of the stepped shaft end of the sealing joint and the inner surface of the stepped hole end of the casing hanger are both sealing surfaces. The stepped shaft and the stepped hole cooperate to facilitate the positioning between the sealing joint and the casing hanger. The sealing surfaces of the two are preferably stepped cylindrical structures to ensure that torque can be applied to the sealing joint, so that the sealing joint can rotate relative to the pipe hanger, and the sealing surfaces of the sealing joint and the casing hanger are in contact.

[0024] The sealing joint and the opposite side of the casing hanger can be chosen to be completely fitted or partially completely fitted. When the sealing joint and the opposite side of the casing hanger are chosen to be completely fitted, that is, the sealing surface of the sealing joint and the sealing surface of the casing hanger are completely in contact, the sealing joint and the casing hanger are all in interference fit in the sealing surface area.

[0025] The sealing joint and the opposite side of the casing hanger in this embodiment can be selected to be partially fully fitted; that is, an interference fit section and a clearance fit section are provided between the sealing surface of the sealing joint and the sealing surface of the casing hanger, and the interference fit section and the clearance fit section are arranged at intervals, and at least two interference fit sections are provided in each set of casing sealing components. The interference fit section and the clearance fit section are arranged at intervals to ensure that even if one of the interference fit sections is damaged and the sealing performance deteriorates, there is still one or more interference fit sections to seal and ensure the sealing performance; while ensuring the sealing performance between the sealing joint and the casing hanger, the torque required to be applied when installing the sealing joint and the casing hanger is reduced.

[0026] To further optimize the solution, the sealing surface of the sealing joint is provided with a sealing groove 6 pointing to the axis of the sealing joint on the interference fit section. The design of the sealing groove 6 reduces the rigidity of the groove area of ​​the sealing joint, so that it can undergo rigid deformation to adapt to the shape of the inner hole of the casing hanger, ensuring that the sealing joint and the casing hanger can be interference fit, and a sealing cavity is formed between the sealing joint and the casing hanger after the interference fit, ensuring the sealing between the sealing joint and the casing hanger.

[0027] In a further optimized solution, a landing ring 4 is provided on the outer side of the outermost casing hanger in the circumferential direction, and a clamping hole for clamping the casing hanger is provided in the axial direction of the landing ring 4, and the inner diameter of the clamping hole is smaller than the outer diameter of the clamping position of the casing hanger, and the landing ring 4 is detachably connected to the well wall where the casing hanger is located. When the first stage of drilling work is completed, the present invention puts the landing ring 4 into the well and fixes it on the well wall of the well, connects the installed and sealed casing sealing assembly to the casing and puts it into the well, until the casing hanger is seated in the landing ring 4, and the landing ring 4 plays a role in positioning the outermost casing hanger.

[0028] Preferably, a first fixed sealing layer is provided on the circumferential outer side of the landing ring and the casing hanger, and a fixing material such as cement is poured in the space formed by the well wall, the landing ring 4 and the casing sealing assembly to form a fixed sealing layer, and the cementing operation is completed, so that the casing sealing assembly and the casing and other components become an integrated structure with the well wall, so that the force of the casing sealing assembly and the casing and their internal components is dispersed to the well wall rather than the working platform, thereby ensuring the stability of the casing sealing assembly and the casing and their internal components.

[0029] In the present invention, adjacent casing hangers can be connected by direct contact or indirect contact. When indirect contact is adopted, an annular support plate or a support ring is fixedly connected to the inner wall of one of the adjacent casing hangers on the outside, and a limiting protrusion 5 is provided on the casing hanger on the inside, or another support plate or a support ring is fixedly connected. Through the mutual support of the support plates or the support rings, the casing hanger on the inside is placed or clamped on the casing hanger on the outside, so as to realize the positioning and support of the casing hanger on the inside, so that a casting space is formed between the adjacent casing hangers and the support plate, and cement and other fixing materials are poured into the casting space to form a second fixed sealing layer to complete the cementing operation.

[0030] In this embodiment, the connection of adjacent casing hangers is realized by direct contact. The adjacent casing hangers are clamped. A limiting protrusion is set on the inner wall of one of the outer sides of the adjacent casing hangers. The inner diameter of the limiting protrusion is smaller than the outer diameter of the clamping position of the casing hanger located inside, and a second fixed sealing layer is set between the adjacent casing hanger and the limiting protrusion. In this embodiment, the limiting protrusion 5 and the casing hanger are an integral structure. Through the size limitation of the clamping position of the limiting protrusion 5 on the outer casing hanger and the inner casing hanger, the casing hanger located inside is placed or clamped on the casing hanger located outside to achieve positioning and support of the casing hanger inside, so that a casting space is formed between the adjacent casing hanger and the limiting protrusion 5, and cement and other fixing materials are poured into the casting space to form a second fixed sealing layer to complete the cementing operation. The second fixed sealing layer in this application realizes the relative fixation between the positions of the two by fixing the adjacent casing hangers, and the sealing between the adjacent casing hangers is realized by combining the second fixed sealing layer with the limiting protrusion 5.

[0031] The casing mudline suspension system of the present invention includes a sending-in condition and a tie-back condition. When the casing mudline suspension system is in the sending-in condition, the sealing joint is a sending-in joint. When the casing mudline suspension system is in the tie-back condition, the sealing joint is a tie-back joint. Sending-in condition: When the construction personnel perform drilling operations, each time a section of drilling work is completed, the corresponding casing and casing sealing assembly are sent into the well in real time. This condition is the sending-in condition. When the present invention is in the sending-in condition, the sealing joint is a sending-in joint. Tie-back condition: The drilling has been completed, and the casing hanger and other components have been arranged in the well. However, due to the completion of the test or other factors, the drilling is in a non-working state, and the casing hanger is connected to the well cap to prevent seawater from entering the well and affecting the subsequent use of the drilling. When the drilling needs to be reactivated, the tie-back joint, casing and other components need to be reinstalled on the casing hanger and reconnected to the platform.

[0032] A casing mudline suspension system delivery method, using the above casing mudline suspension system, comprising: S1. Determine the number and size of casing seal assemblies according to construction requirements, and install the sealing joints and casing hangers in each set of casing seal assemblies by interference fit to form a metal seal, and arrange the casing hangers from large to small in order of their inner diameters, namely, the first casing seal assembly, the second casing seal assembly, ... the Nth casing seal assembly; S2. Drilling a well to a specified depth at a specified location to form a first well, sending a first casing sealing assembly to a specified location of the first well using a casing, and performing cementing; S3. Drilling to a specified depth at the bottom of the first well to form a second well, sending the second casing seal assembly to a specified position of the second well using a casing, and sealingly connecting the casing hanger in the first casing seal assembly and the casing hanger in the second casing seal assembly; S4. Drilling at the bottom of the second well to a specified depth to form a third well, ...; Repeat step S3 until the Nth casing seal assembly is installed at the designated position and the cementing operation is completed. After each drilling operation is completed, the casing seal assembly is immediately sent to the designated position of the drilling, that is, the casing is gradually lowered during the drilling process, and the delivery joint and the casing hanger are sealed by forming a metal seal through interference fit, ensuring that the delivery joint, the third casing hanger and the casing form a sealed space, avoiding the leakage of oil and natural gas, and providing safety and reliability for offshore oil and natural gas exploration and drilling.

[0033] Further optimization scheme, in step S2, a fixing material is poured into the gap between the first casing sealing assembly and the first drilling well to form a first fixing sealing layer, and the cementing operation is completed; in step S3, a fixing material is poured into the gap between the first casing sealing assembly and the second casing sealing assembly to form a second fixing sealing layer, and the cementing operation is completed. Cement and other fixing materials are poured into the space formed by the well wall, the landing ring 4 and the casing sealing assembly to form a fixing sealing layer, and the cementing operation is completed, so that the casing sealing assembly and the casing and other components are integrated with the well wall, so that the forces of the casing sealing assembly and the casing and the internal components of the two are dispersed to the well wall, rather than the working platform, to ensure the stability of the casing sealing assembly and the casing and the internal components of the two. A pouring space is formed between the adjacent casing hangers and the limiting protrusions 5, and cement and other fixing materials are poured into the pouring space to form a second fixing sealing layer, and the adjacent casing sealing assemblies are connected, and the force of the internal casing sealing assembly is transmitted to the outer casing sealing assembly, and then to the well wall.

[0034] like Figure 2, a specific scheme is used for discussion: the casing mudline suspension system is in the delivery condition, and the casing sealing assembly is provided with three groups, namely the first casing sealing assembly, the second casing sealing assembly, and the third casing sealing assembly; the first casing sealing assembly includes the first delivery joint 11 and the first casing hanger 12; the second casing sealing assembly includes the second delivery joint 21 and the second casing hanger 22; the third casing sealing assembly includes the third delivery joint 31 and the third casing hanger 32. The initial size of the wellbore drilled by the well is 26 inches, the size of the landing ring 4 is 30 inches, the size of the first delivery joint 11 is 20 inches, the size of the first casing hanger 12 is 20 inches, the size of the second delivery joint 21 is 13-3 / 8 inches (thirteen and three eighths inches, the same below), the size of the second casing hanger 22 is 13-3 / 8 inches, the size of the third delivery joint 31 is 9-5 / 8 inches, and the size of the third casing hanger 32 is 9-5 / 8 inches.

[0035] Casing mudline suspension system delivery process: First, a 26-inch wellbore is drilled at a designated location to a designated depth to form a first wellbore, and the first running joint 11 and the first casing hanger 12 are sleeved together. By applying a torque of 5000 ft·lbs, the sealing end face of the first running joint 11 and the sealing end face of the first casing hanger 12 are matched to achieve interference, forming a metal seal, thereby achieving the purpose of sealing. The first running joint 11 and the first casing hanger 12 are lowered into place by using a casing, seated on the landing ring 4, and then cemented. In this way, the first running joint 11, the first casing hanger 12 and the casing form a 20-inch sealed space, thereby preventing leakage of oil and natural gas.

[0036] Secondly, a 17-1 / 2-inch wellbore is drilled to a specified depth through a 20-inch casing to form a second wellbore, and a second delivery joint 21 and a second casing hanger 22 are connected. By applying a torque of 5000 ft·lbs, the sealing bevel of the second delivery joint 21 is matched with the sealing bevel of the second casing hanger 22 to achieve interference, forming a metal seal, thereby achieving the purpose of sealing. The second casing hanger 22 is lowered into place using the casing and seated on the first casing hanger 12, and then cemented. In this way, the second delivery joint 21, the second casing hanger 22 and the casing form a 13-3 / 8-inch sealed space, thereby preventing leakage of oil and natural gas.

[0037] Again, through the space provided by the 13-3 / 8-inch casing, a 12-1 / 4-inch wellbore is drilled to a specified depth to form a third wellbore, and the third delivery joint 31 and the third casing hanger 32 are connected. By applying a torque of 5000 ft·lbs, the sealing bevel of the third delivery joint 31 is matched with the sealing bevel of the third casing hanger 32 to achieve interference, forming a metal seal, thereby achieving the purpose of sealing. The third delivery joint 31 and the third casing hanger 32 are lowered into place by using the casing, seated on the second casing hanger 22, and then cemented. In this way, the third delivery joint 31, the third casing hanger 32 and the casing form a 9-5 / 8-inch sealed space, thereby avoiding the leakage of oil and natural gas, and providing safety and reliability for offshore oil and natural gas exploration and drilling.

[0038] A casing mudline suspension system tie-back method, using the casing mudline suspension system, comprising: S1. Determine the number and size of tieback joints according to the original casing hangers in the drilling well, and arrange the tieback joints from large to small according to their inner diameters as the first tieback joint, the second tieback joint, ... the Nth tieback joint, and arrange the casing hangers from large to small according to their inner diameters as the first casing hanger, the second casing hanger, ... the Nth casing hanger; S2. Recover the well cap on the first casing hanger, connect the first tieback joint to the tieback casing and send both into the well, sleeve the first tieback joint and the first casing hanger, and install them by forming a metal seal through an interference fit to form a casing seal assembly; S3. Recover the well cap on the second casing hanger and connect the second tieback joint with ...; Repeat step S2 until the Nth tieback joint and the Nth casing hanger are connected and installed by metal sealing to form a casing sealing assembly, completing the tieback work. The tieback joint and the casing hanger are formed by interference fit to form a metal seal to achieve the purpose of sealing, thereby completing the task of reconnecting the wellhead that has been detached from the platform to the platform, greatly reducing production costs.

[0039] like Figure 3, a specific scheme is used for discussion: the casing mudline suspension system is in a tieback condition, and the casing sealing assembly is provided with three groups, namely the first casing sealing assembly, the second casing sealing assembly, and the third casing sealing assembly; the first casing sealing assembly includes the first tieback joint 13 and the first casing hanger 12; the second casing sealing assembly includes the second tieback joint 23 and the second casing hanger 22; the third casing sealing assembly includes the third tieback joint 33 and the third casing hanger 32. The size of the first tieback joint 13 is 20 inches, the size of the first casing hanger 12 is 20 inches, the size of the second tieback joint 23 is 13-3 / 8 inches (thirteen and three eighths inches, the same below), the size of the second casing hanger 22 is 13-3 / 8 inches, the size of the third tieback joint 33 is 9-5 / 8 inches, and the size of the third casing hanger 32 is 9-5 / 8 inches.

[0040] Casing mudline suspension system tieback process: First, the abandoned well cap connected to the first casing hanger 12 is recovered, the first tieback joint 13 is connected to the tieback casing, the first tieback joint 13 and the tieback casing are lowered, and the first tieback joint 13 is connected to the first casing hanger 12. By applying a torque of 5000 ft·lbs, the sealing end face of the first tieback joint 13 and the sealing end face of the first casing hanger 12 are interference fit to form a metal seal, thereby achieving the purpose of sealing and providing sealing conditions for the tieback of the next wellhead level.

[0041] Secondly, the abandoned well cap connected to the second tieback joint 23 is recovered, the second tieback joint 23 is connected to the tieback casing, the second tieback joint 23 and the tieback casing are lowered, and the second tieback joint 23 is connected to the second casing hanger 22. By applying a torque of 5000 ft·lbs, the sealing spherical surface of the second tieback joint 23 and the sealing inclined surface of the second casing hanger 22 are interference fit to form a metal seal, thereby achieving the purpose of sealing and providing sealing conditions for the tieback of the next wellhead level.

[0042] Next, the abandoned well cap connected to the third tieback joint 33 is recovered, the third tieback joint 33 is connected to the tieback casing, the third tieback joint 33 and the tieback casing are lowered, and the third tieback joint 33 is connected to the third casing hanger 32. By applying a torque of 5000 ft·lbs, the sealing bevel of the third tieback joint 33 and the sealing bevel of the third casing hanger 32 are interference fit to form a metal seal, thereby achieving the purpose of sealing, and further completing the task of reconnecting the wellhead detached from the platform to the platform, thereby greatly reducing the production cost.

[0043] The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for a person skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

[0044] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0045] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0046] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A casing mudline suspension system, characterized in that: It comprises at least two groups of coaxially arranged casing sealing assemblies; the casing sealing assembly comprises a sealing joint and a casing hanger sleeved on the outside of the sealing joint, the sealing joint and the casing hanger are both made of metal, and the sealing joint and the casing hanger are interference fit to form a metal seal; all the casing sealing assemblies are sleeved in sequence from the inside to the outside and extend in the axial direction, and the inner diameter of the casing hangers arranged from the inside to the outside gradually increases; adjacent casing hangers are sealed and connected.

2. The casing mudline suspension system according to claim 1, characterized in that: The side of the sealing joint close to the casing hanger is a stepped shaft, and the side of the casing hanger close to the sealing joint is provided with a stepped hole. The stepped shaft end of the sealing joint and the stepped hole end of the casing hanger are interference fit, and the outer circumference of the stepped shaft end of the sealing joint and the inner surface of the stepped hole end of the casing hanger are both sealing surfaces.

3. The casing mudline suspension system according to claim 2, characterized in that: An interference fit section and a clearance fit section are provided between the sealing surface of the sealing joint and the sealing surface of the casing hanger. The interference fit section and the clearance fit section are arranged at intervals, and at least two interference fit sections are provided in each group of the casing sealing assembly.

4. The casing mudline suspension system according to claim 3, characterized in that: The sealing surface of the sealing joint is provided with a sealing groove pointing to the axis of the sealing joint on the interference fit section.

5. The casing mudline suspension system according to claim 1, characterized in that: A landing ring is arranged on the circumferential outer side of the outermost casing hanger, and a clamping hole for clamping the casing hanger is opened axially in the landing ring, the inner diameter of the clamping hole is smaller than the outer diameter of the clamping position of the casing hanger, and the landing ring is detachably connected to the well wall where the casing hanger is located.

6. The casing mudline suspension system according to claim 5, characterized in that: A first fixed sealing layer is disposed on the circumferential outer sides of the landing ring and the casing hanger.

7. The casing mudline suspension system according to claim 1, characterized in that: The adjacent casing hangers are clamped, and a limiting protrusion is provided on the inner wall of one of the adjacent casing hangers located on the outside. The inner diameter of the limiting protrusion is smaller than the outer diameter of the casing hanger clamping position located on the inside, and a second fixed sealing layer is provided between the adjacent casing hanger and the limiting protrusion.

8. A method for running a casing mudline suspension system, using the casing mudline suspension system according to any one of claims 1 to 7, characterized in that: include: S1. Determine the number and size of the casing seal assemblies according to the construction requirements, and install the sealing joints and the casing hangers in each set of the casing seal assemblies by interference fit to form a metal seal, and arrange the casing hangers from large to small according to the inner diameter of the casing hangers, namely, the first casing seal assembly, the second casing seal assembly, ... the Nth casing seal assembly; S2. Drilling at a designated location to a designated depth to form a first wellbore, sending the first casing sealing assembly to a designated location of the first wellbore using a casing, and performing cementing; S3. Drilling to a specified depth at the bottom of the first well to form a second well, sending the second casing seal assembly to a specified position of the second well using a casing, and sealingly connecting the casing hanger in the first casing seal assembly and the casing hanger in the second casing seal assembly; S4. Drilling at the bottom of the second well to a specified depth to form a third well, ...; Repeat step S3 until the Nth casing sealing assembly is installed at the specified position and the cementing operation is completed.

9. A casing mudline suspension system delivery method according to claim 8, characterized in that: In step S2, a fixing material is poured into the gap between the first casing sealing assembly and the first drilling well to form a first fixing sealing layer, thereby completing the cementing operation; In step S3, a fixing material is poured into the gap between the first casing sealing assembly and the second casing sealing assembly to form a second fixing sealing layer, thereby completing the cementing operation.

10. A casing mudline suspension system tie-back method, using the casing mudline suspension system according to any one of claims 1 to 7, characterized in that: include: S1. Determine the number and size of tieback joints according to the original casing hangers in the drilling well, and arrange the tieback joints from large to small according to their inner diameters as the first tieback joint, the second tieback joint, ... the Nth tieback joint, and arrange the casing hangers from large to small according to their inner diameters as the first casing hanger, the second casing hanger, ... the Nth casing hanger; S2. Recover the well cap on the first casing hanger, connect the first tieback joint to the tieback casing and send both into the well, sleeve the first tieback joint and the first casing hanger, and install them by forming a metal seal through an interference fit to form a casing seal assembly; S3. Recover the well cap on the second casing hanger and tie the second back joint with ...; Repeat step S2 until the Nth tieback joint and the Nth casing hanger are sleeved and installed by metal sealing to form a casing sealing assembly, thus completing the tieback work.

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