A marine casing head and its usage method

Abstract

The present invention relates to the technical field of oil drilling equipment, and particularly relates to an offshore casing head and its usage method. The offshore casing head includes a casing head housing and a base. The base includes a cover body with an opening at the bottom. The upper end of the cover body is provided with a central hole, an operation port is provided below the side wall, and a ring is detachably connected to the lower end. The lower end of the ring is hermetically connected to a riser. A sealing plug is hermetically and slidably sleeved on the cover body, the side wall can block the operation port, and the lower end can be hermetically docked with the ring. The top of the cover body is hermetically docked with the casing head housing, and an inverted slip hanger is arranged inside. A threaded rod penetrates through the inverted slip hanger and the cover body, the upper end is screwed to a threaded groove on the lower end face of the casing head housing, and the lower end is screwed to a first nut. The present invention can completely isolate the inverted slip hanger and the surface casing from the external environment, with good anti-corrosion effect. The casing head housing, the base and the inverted slip hanger are all detachably connected, which is convenient for maintenance and repair.

Description

Technical Field

[0001] The present invention relates to the technical field of oil drilling equipment, and particularly relates to an offshore casing head and a using method thereof. Background Art

[0002] An offshore casing head refers to a casing head applicable to an offshore drilling platform. Due to the harsh marine climate conditions and strong corrosiveness to oil production equipment, anti-corrosion protection is required. The offshore casing head generally uses an inverted slip hanger to suspend the surface casing. The inverted slip hanger is installed at the bottom of the casing head housing and is directly exposed to the air like the surface casing, making it very easy to be corroded and causing potential safety hazards.

[0003] The patent with the authorization announcement number CN209892148U discloses an anti-corrosion structure for the inverted slips of an offshore casing head, which includes a casing head and a slip housing installed below the casing head. The casing head is connected to the slip housing through connecting bolts, the slip housing is connected to the slip teeth through connecting pins, the inner surface of the slip teeth is connected to the surface casing, and the slip housing and the slip teeth are connected through a lower inverted conical surface; an upper sealing device for sealing with the surface casing is provided on the inner surface of the casing head; a sealing groove is provided below the casing head, and an intermediate sealing device for sealing with the upper end surface of the slip housing is provided in the sealing groove; a lower sealing device is provided in the variable volume cavity below the slip teeth inside the slip housing; the upper sealing device, the intermediate sealing device, and the lower sealing device form a sealing space for sealing the inner surface of the slip teeth. Although the above structure can, to a certain extent, isolate the corrosion of the outside world on the slip teeth of the inverted slip hanger, it cannot isolate the entire inverted slip hanger and the surface casing from the outside world, and the anti-corrosion effect is limited. Summary of the Invention

[0004] To solve at least one of the above technical problems, the present invention provides an offshore casing head, including a casing head housing and a base. The base includes a cover body with an open bottom. A central hole is provided at the upper end of the cover body, an operation port is provided below the side wall, a ring is detachably connected to the lower end, a riser is hermetically connected to the lower end of the ring, a plugging ring is hermetically sleeved on the cover body in a sliding manner, the side wall can block the operation port, and the lower end can be hermetically docked with the ring. The top of the cover body is hermetically docked with the casing head housing, and an inverted slip hanger is provided inside. A threaded rod passes through the inverted slip hanger and the cover body, the upper end is screwed into a threaded groove on the lower end surface of the casing head housing, and the lower end is screwed with a first nut.

[0005] Preferably, a number of first axial holes for the threaded rod to pass through are equidistantly arranged in the circumferential direction of the inverted slip hanger, and a number of second axial holes for the threaded rod to pass through are equidistantly arranged in the circumferential direction of the cover body. A first sealing ring is provided between the casing head housing and the surface casing. A slip hanger for hanging the production casing is provided inside the casing head housing, and a setscrew for pressing the slip hanger is arranged radially. A second sealing ring for sealing the casing head housing and the production casing is provided above the slip hanger.

[0006] Preferably, a third sealing ring is provided between the cover body and the casing head housing, and the third sealing ring is arranged outside the threaded rod. A fourth sealing ring is provided between the circular ring and the plugging ring, and a fifth sealing ring is provided between the circular ring and the riser.

[0007] Preferably, the base further includes a support frame, and the support frame includes a cylinder and a support ring. The cylinder is fixed to the upper end of the circular ring, and its inner wall fits the surface casing. A number of sliding holes are equidistantly arranged in the circumferential direction along the axis. The lower end of the support ring is provided with sliding rods matching the sliding holes, a third axial hole for the threaded rod to pass through is arranged along the axis, an inverted slip hanger is provided at the upper end, and a first nut is provided at the lower end.

[0008] Preferably, the operation port extends upward from the lower end of the cover body. The lower end of the cover body extends radially outward to form a first flange. The plugging ring is vertically slidably arranged on the inner side wall of the cover body, and the lower end extends radially outward to form a second flange. A damping sealing ring is provided between the cover body and the plugging ring, and the damping sealing ring is arranged above the operation port.

[0009] Preferably, the upper end of the riser extends radially outward to form a third flange. The cover body, the plugging ring, the circular ring and the riser are connected and fixed by a clamp.

[0010] Preferably, the clamp includes two semi-circular clamps that can form a circular ring. The inner wall of the semi-circular clamp is provided with a circular slot for the first flange, the second flange, the circular ring and the third flange to be inserted. First connecting ears and a first slot are respectively provided at the circumferential two ends of one semi-circular clamp, and second connecting ears that can be inserted into the first slot and a second slot for the first connecting ears to be inserted are respectively provided at the circumferential two ends of the other semi-circular clamp. A first bolt passes through the first connecting ear and the second connecting ear and then connects to a second nut.

[0011] Preferably, the semi-circular clamp includes an upper clamp and a lower clamp. A second bolt passes through the centers of the upper clamp and the lower clamp and then connects to a third nut. A semi-circular limiting wall extending downward is provided on the outer side wall of the upper clamp, and the outer side wall of the lower clamp can slide up and down in contact with the inner side wall of the limiting wall. The circular slot includes an upper half slot located at the lower end of the upper clamp and a lower half slot located at the upper end of the lower clamp.

[0012] Preferably, the first connecting ear includes a first upper ear located at the upper end of the upper clamp and a first lower ear located at the lower end of the lower clamp, and the second connecting ear includes a second upper ear located at the lower end of the upper clamp and a second lower ear located at the upper end of the lower clamp.

[0013] The present invention provides a method for using a marine casing head, comprising the following steps:

[0014] Step S100: Drill a well to the target depth within the operation area, lower the riser and then cement the well. After the cementing is completed, continue to drill downward from inside the riser to the target depth, lower the surface casing and then cement the well, and install the marine casing head;

[0015] Step S200: Place the ring of the base on the upper end of the riser, and let the surface casing pass through the ring; place the slip hanger above the ring, then pass the threaded rod through the slip hanger and connect the first nut; cover the ring with the cover body, slide the sealing ring on the cover body, open the operation port, then place the casing head housing on the upper end of the cover body, and screw the first nut. The threaded rod is screwed into the thread groove of the casing head housing, and the slip hanger moves upward. When the slip jaws of the slip hanger grip the surface casing tightly, the slip seat of the slip hanger rises to the limit state and the first nut cannot be screwed further, completing the connection and fixation of the slip hanger, the cover body and the casing head housing; slide the sealing ring on the cover body to seal the operation port, connect and fix the cover body and the sealing ring to the ring, and at the same time connect and fix the ring and the riser;

[0016] Step S300: Continue to drill downward from inside the surface casing to the target depth, lower the production casing, and install a slip hanger inside the casing head housing to make the slip hanger grip the production casing tightly.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects:

[0018] 1. The present invention forms a closed space for protecting the slip hanger and the surface casing jointly by the casing head housing, the base and the riser, completely isolating the slip hanger and the surface casing from the external environment, avoiding the corrosion and attack of the marine climate environment on the slip hanger and the surface casing, and improving the service life and oil production safety of the oil production equipment;

[0019] 2. All connections between the casing head housing, the base and the slip hanger in the present invention are detachable, which is beneficial to later maintenance and repair;

[0020] 3. The base consists of a cover body, a sealing ring and a circular ring, which can seal and protect the reverse slip hanger and surface casing located inside the base. An operation opening is provided below the cover body, through which the reverse slip hanger inside the cover body can be installed. The sealing ring can slide to seal the operation opening, forming a sealed space inside the base. The lower end of the circular ring of the base is hermetically connected to the riser pipe, which can isolate and protect the surface casing located below the base;

[0021] 4. A support frame is provided inside the cover body of the base. The cylinder of the support frame fits the surface casing, which can play a role in straightening the surface casing. The support ring of the support frame is used to place the reverse slip hanger, so that there is a certain distance between the reverse slip hanger and the circular ring, which is convenient for screwing the threaded rod and the first nut, improving work efficiency and reducing the labor intensity of workers. The sliding rod at the lower end of the support ring can slide vertically in the sliding hole of the cylinder, so that the support ring can move upward with the slip seat of the reverse slip hanger, facilitating the slip teeth of the reverse slip hanger to hold the surface casing tightly;

[0022] 5. A damping sealing ring is provided between the cover body and the sealing ring. On the one hand, the damping sealing ring can seal the gap between the cover body and the sealing ring, and on the other hand, it can generate a damping force to prevent the sealing ring from slipping freely. A first flange is provided at the lower end of the cover body, which is beneficial to connecting and fixing the cover body and the circular ring. A second flange is provided at the lower end of the sealing ring, which is not only beneficial to connecting and fixing the sealing ring and the circular ring, but also beneficial to pushing the sealing ring to slide up and down;

[0023] 6. A clamp is used to connect and fix the cover body, the sealing ring, the circular ring and the riser pipe together, which is convenient and fast, can improve the connection stability and sealing stability between the cover body and the sealing ring and the circular ring. At the same time, the clamp is easy to disassemble, which is convenient for later maintenance and repair of the equipment;

[0024] 7. The two semi-circular clamps of the clamp are of a split structure, which can flexibly adjust the axial length of its annular slot, facilitating the insertion of the first flange of the cover body, the second flange of the sealing ring, the circular ring and the third flange of the riser pipe, and improving the connection effect;

[0025] In summary, the present invention can completely isolate the reverse slip hanger and the surface casing from the external environment, with good anti-corrosion effect. The casing head housing, the base and the reverse slip hanger are all detachably connected, which is convenient for maintenance and repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the right view of the present invention;

[0027] Figure 2 is Figure 1 the A-A sectional view of;

[0028] Figure 3 is the three-dimensional structure schematic diagram of the present invention;

[0029] Figure 4 for Figure 3 Exploded view of;

[0030] Figure 5 is a three-dimensional cross-sectional view of the base;

[0031] Figure 6 This is the exploded view of the clamp;

[0032] Figure 7 Exploded view of a semicircular hoop.

[0033] Explanation of reference numerals 1. casing head housing, 11. threaded groove, 12. first sealing ring, 13. top screw, 14. second sealing ring, 2. inverted cava hanger, 21. first axial hole, 3. base, 31. cover, 311. center hole, 312. operation port, 313. second axial hole, 314. third sealing ring, 315. damping sealing ring, 316. first flange, 32. blocking ring, 321. second flange, 33. circular ring, 331. fourth sealing ring, 332. fifth sealing ring, 34. threaded rod, 35. first nut, 36. support frame, 361. cylinder, 3611. sliding hole, 362. support Support ring, 3621, sliding rod, 3622, third axial hole, 4, surface casing, 5, watertight pipe, 51, third flange, 6, clamp, 61, semicircular hoop, 611, upper hoop, 6111, limiting wall, 612, lower hoop, 613, second bolt, 614, third nut, 62, annular slot, 621, upper half slot, 622, lower half slot, 63, first connecting ear, 631, first upper ear, 632, first lower ear, 64, first slot, 65, second connecting ear, 651, second upper ear, 652, second lower ear, 66, second slot, 67, first bolt, 68, second nut, 7, cava hanger. DETAILED DESCRIPTION

[0034] The specific implementation of the present invention is described below in conjunction with the accompanying drawings and embodiments:

[0035] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them, and are not used to limit the conditions under which the present invention can be implemented. Any structural modification, change in proportional relationship or adjustment of size should fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0036] Meanwhile, terms such as "upper", "lower", "left", "right", "middle", and "one" cited in this specification are only for the convenience of clear description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships shall also be regarded as the scope of implementation of the present invention without substantial changes in the technical content. Embodiment 1

[0037] Combined with the attached Figure 1-7 In this embodiment, a marine casing head is provided, which includes a casing head housing 1 and a base 3. The base 3 includes a cover body 31 with an open bottom. A central hole 311 is provided at the upper end of the cover body 31, an operation port 312 is provided below the side wall, and a ring 33 is detachably connected to the lower end. The lower end of the ring 33 is hermetically connected to a riser 5. A sealing plug 32 is hermetically sleeved on the cover body 31, the side wall can block the operation port 312, and the lower end can be hermetically docked with the ring 33. The top of the cover body 31 is hermetically docked with the casing head housing 1, and an inverted slip hanger 2 is provided inside. A threaded rod 34 passes through the inverted slip hanger 2 and the cover body 31, the upper end is screwed into a threaded groove 11 on the lower end face of the casing head housing 1, and the lower end is screwed with a first nut 35.

[0038] In the above technical solution, the reverse slip hanger 2 is a common device for hanging the surface casing 4 and is installed below the casing head housing 1. It includes a reverse slip seat and reverse slip teeth. The threaded rod 34 passes through the reverse slip hanger 2, which means it passes through the reverse slip seat of the reverse slip hanger 2. And to ensure the connection stability, a plurality of threaded rods 34 and first nuts 35 are arranged at equal circumferential intervals, which is a conventional structure setting in this field and will not be elaborated here; it should be noted that the top of the casing head housing 1 is connected to wellhead devices such as blowout preventers or Christmas trees according to different process stages. During use, the internal space of the casing head housing 1 is also a closed space completely isolated from the external environment; the central hole 311 on the cover body 31 allows the slip teeth of the reverse slip hanger 2 and the surface casing 4 to freely pass through the cover body 31. The operation port 312 on the cover body 31 is used to operate the equipment inside the cover body 31. When the operation port 312 on the cover body 31 is opened, the threaded rod 34 and the first nut 35 can be screwed to connect and fix the casing head housing 1, the cover body 31 and the reverse slip hanger 2. After the connection is completed, the sliding sealing ring 32 seals the operation port 312 to form a closed space inside the base 3 to isolate and protect the reverse slip hanger 2 and the surface casing 4 located inside the base 3. It should be noted that the sealing ring 32 can seal the operation port 312 by sliding up and down or by rotating and sliding. When using rotational sliding sealing, the cover body 31 and the sealing ring 32 need to be circular, and then through holes corresponding to the operation port 312 are opened on the sealing ring 32. During rotation, when the through hole on the sealing ring 32 coincides with the operation port 312, the operation port 312 is opened, and when it is staggered with the operation port 312, the operation port 312 is sealed; the inner diameter of the ring 33 is preferably the same as the outer diameter of the surface casing 4. The ring 33 and the riser 5 can be hermetically connected and fixed by welding or any suitable method. The ring 33 and the cover body 31 and the sealing ring 32 can be detachably connected by bolt-nut assemblies or by any suitable method; parts not mentioned in this embodiment are arranged in the conventional manner in the prior art.

[0039] In this embodiment, the casing head housing 1, the base 3 and the riser 5 jointly form a closed space to protect the reverse slip hanger 2 and the surface casing 4, completely isolating the reverse slip hanger 2 and the surface casing 4 from the external environment, avoiding the corrosion and attack of the marine climate environment on the reverse slip hanger 2 and the surface casing 4, and improving the service life and oil production safety of the oil production equipment; in the traditional one, the casing head housing 1 and the base 3 are fixedly connected by welding, while in this embodiment, the casing head housing 1, the base 3 and the reverse slip hanger 2 are all detachably connected, which is beneficial to later maintenance and repair.

[0040] In a specific technical solution, a number of first axial holes 21 for the threaded rod 34 to pass through are equidistantly arranged in the circumferential direction of the reverse slip hanger 2. A number of second axial holes 313 for the threaded rod 34 to pass through are equidistantly arranged in the circumferential direction of the cover body 31. A first sealing ring 12 is provided between the casing head housing 1 and the surface casing 4. A slip hanger 7 for hanging the oil layer casing (not shown in the figure) is provided inside the casing head housing 1. A setscrew 13 for pressing the slip hanger 7 is arranged radially. A second sealing ring 14 for sealing the casing head housing 1 and the oil layer casing is provided above the slip hanger 7.

[0041] In the above technical solution, the first axial hole 21 is opened on the reverse slip seat of the reverse slip hanger 2, which is common knowledge in the art and will not be elaborated here.

[0042] In a specific technical solution, a third sealing ring 314 is provided between the cover body 31 and the casing head housing 1. The third sealing ring 314 is arranged outside the threaded rod 34. A fourth sealing ring 331 is provided between the ring 33 and the plugging ring 32, and a fifth sealing ring 332 is provided between the ring 33 and the riser 5.

[0043] In the above technical solution, the third sealing ring 314 is arranged outside the threaded rod 34, which can also include the threaded rod 34 within the sealing range and provide sealing protection for the threaded rod 34.

[0044] In a specific technical solution, the base 3 further includes a support frame 36. The support frame 36 includes a cylinder 361 and a support ring 362. The cylinder 361 is fixed to the upper end of the ring 33, and its inner wall fits the surface casing 4. A number of sliding holes 3611 are equidistantly arranged in the circumferential direction along the axis. A sliding rod 3621 matching the sliding holes 3611 is provided at the lower end of the support ring 362. A third axial hole 3622 for the threaded rod 34 to pass through is arranged along the axis. The reverse slip hanger 2 is provided at the upper end, and a first nut 35 is provided at the lower end.

[0045] In the above technical solution, the cylinder 361 fits the surface casing 4, which can play a role in straightening the surface casing 4. The support ring 362 is used to place the reverse slip hanger 2, so that an automatic operation distance is spaced between the reverse slip hanger 2 and the ring 33. Without manual lifting of the reverse slip hanger 2 by the staff, the threaded rod 34 and the first nut 35 can be screwed, improving work efficiency and reducing labor intensity. The sliding rod 3621 at the lower end of the support ring 362 can vertically slide in the sliding holes 3611 of the cylinder 361, enabling the support ring 362 to move upward with the slip seat of the reverse slip hanger 2, so that the slip teeth of the reverse slip hanger 2 can hold the surface casing 4 tightly. The ring 33 and the cylinder 361 are preferably integrally formed.

[0046] In a specific technical solution, the operation port 312 extends upward from the lower end of the cover body 31. A first flange 316 extends radially outward from the lower end of the cover body 31. The plugging ring 32 is vertically slidably arranged on the inner side wall of the cover body 31, and a second flange 321 extends radially outward from the lower end. A damping sealing ring 315 is arranged between the cover body 31 and the plugging ring 32, and the damping sealing ring 315 is arranged above the operation port 312.

[0047] In the above technical solution, multiple operation ports 312 can be arranged at equal circumferential intervals. In this embodiment, two are arranged; the damping sealing ring 315 is preferably a rubber sealing ring. On the one hand, it can seal the gap between the cover body 31 and the plugging ring 32, and on the other hand, it can generate a damping force to prevent the plugging ring 32 from sliding freely; arranging the first flange 316 at the lower end of the cover body 31 is beneficial for connecting and fixing the cover body 31 and the circular ring 33. Arranging the second flange 321 at the lower end of the plugging ring 32 is not only beneficial for connecting and fixing the plugging ring 32 and the circular ring 33, but also convenient for pushing the plugging ring 32 to slide up and down. In this embodiment, the first flange 316 and the second flange 321 can be spliced into a circle; during use, the plugging ring 32 is pushed up through the second flange 321 to open the operation port 312. At this time, the first nut 35 can be screwed to connect and fix the support ring 362, the inverted slip hanger 2, the cover body 31, and the casing head housing 1. After completion of the fixation, the plugging ring 32 is pushed down through the second flange 321 until it seals and abuts against the circular ring 33 to plug the operation port 312 and form a sealed space. At this time, the first flange 316 and the second flange 321 can be fixed on the circular ring 33 through any suitable connecting member (including but not limited to a screw-nut assembly).

[0048] In a specific technical solution, a third flange 51 extends radially outward from the upper end of the riser 5. The cover body 31, the plugging ring 32, the circular ring 33, and the riser 5 are connected and fixed by a clamp 6.

[0049] In the above technical solution, as a commonly used device in offshore drilling, in order to facilitate hoisting and transfer, a circular third flange 51 is usually provided at the top of the riser 5. Using a clamp 6 to connect and fix the cover body 31, the plugging ring 32, the circular ring 33, and the riser 5 together is convenient and fast, which can improve the connection stability and sealing stability between the cover body 31 and the plugging ring 32 and the circular ring 33. At the same time, the clamp 6 is a detachable connecting member, which is convenient for later maintenance and repair of the equipment.

[0050] In a specific technical solution, the clamp 6 includes two semi-circular clamps 61 that can form a circular ring. An annular slot 62 for inserting the first flange 316, the second flange 321, the ring 33, and the third flange 51 is provided on the inner wall of the semi-circular clamp 61. First connecting ears 63 and a first slot 64 are respectively provided at the circumferential two ends of one semi-circular clamp 61. Second connecting ears 65 that can be inserted into the first slot 64 and a second slot 66 for inserting the first connecting ears 63 are respectively provided at the circumferential two ends of the other semi-circular clamp 61. A first bolt 67 passes through the first connecting ear 63 and the second connecting ear 65 and then connects to a second nut 68.

[0051] In the above technical solution, the first connecting ear 63 and the second connecting ear 65 are preferably integrally formed with the semi-circular clamp 61, and connecting holes for the first bolt 67 to pass through are respectively provided on the first connecting ear 63 and the second connecting ear 65. During use, the two semi-circular clamps 61 are butted, and the first flange 316 of the cover body 31, the second flange 321 of the sealing ring 32, the ring 33, and the third flange 51 of the riser 5 are inserted into the annular slot 62 of the two semi-circular clamps 61. At this time, the first connecting ear 63 of one semi-circular clamp 61 is inserted into the second slot 66 of the other semi-circular clamp 61. At the same time, the second connecting ear 65 of the other semi-circular clamp 61 is inserted into the first slot 64 of this semi-circular clamp 61. The two semi-circular clamps 61 enter a stable plug-in state. Finally, the first connecting ear 63 and the second connecting ear 65 are locked by the cooperation of the first bolt 67 and the second nut 68, realizing the locking of the two semi-circular clamps 61. At this time, the entire clamp 6 is in a circular ring shape, without radial protrusions, and has high use safety.

[0052] In a specific technical solution, the semi-circular clamp 61 includes an upper clamp 611 and a lower clamp 612. A second bolt 613 passes through the centers of the upper clamp 611 and the lower clamp 612 and then connects to a third nut 614. A semi-circular limiting wall 6111 extending downward is provided on the outer side wall of the upper clamp 611. The outer side wall of the lower clamp 612 can slide up and down in contact with the inner side wall of the limiting wall 6111. The annular slot 62 includes an upper half slot 621 located at the lower end of the upper clamp 611 and a lower half slot 622 located at the upper end of the lower clamp 612.

[0053] In the above technical solution, the center of the upper hoop 611 and the lower hoop 612 refers to the center of the crown positions of the upper hoop 611 and the lower hoop 612. The second bolt 613 is connected from the center, which can improve the connection stability. The semi-circular hoop 61 adopts an upper and lower split structure, which can flexibly adjust the axial length of the annular slot 62, facilitating the insertion of the first flange 316, the second flange 321, the ring 33, and the third flange 51. This is because the annular slot 62 needs to lock the first flange 316, the second flange 321, the ring 33, and the third flange 51, and its diameter should be the same as that of the first flange 316, the second flange 321, the ring 33, and the third flange 51 (in this embodiment, the diameters of the first flange 316, the second flange 321, the ring 33, and the third flange 51 are the same. If the diameters are different, the annular slot 62 will have multiple different diameters accordingly, presenting a stepped shape). At the same time, the axial length of the annular slot 62 should be the same as the sum of the axial lengths of the first flange 316, the second flange 321, the ring 33, and the third flange 51. However, to ensure the sealing effect, a fourth sealing ring 331 and a fifth sealing ring 332 are provided between the plugging ring 32, the ring 33, and the third flange 51. The fourth sealing ring 331 and the fifth sealing ring 332 have a certain axial length themselves. When the axial length of the annular slot 62 is fixed, a relatively large force is required to complete the insertion of the first flange 316, the second flange 321, the ring 33, and the third flange 51. In this embodiment, the annular slot 62 is split. During insertion, only need to loosen the third nut 614 to release the axial lock on the upper hoop 611 and the lower hoop 612, and move the lower hoop 612 downward, then the axial length of the annular slot 62 can be increased, and the first flange 316, the second flange 321, the ring 33, and the third flange 51 can be easily inserted into the annular slot 62. After the insertion is completed, just tighten the third nut 614 to re-implement the axial lock on the upper hoop 611 and the lower hoop 612.

[0054] In a specific technical solution, the first connecting ear 63 includes a first upper ear 631 located at the upper end of the upper hoop 611 and a first lower ear 632 located at the lower end of the lower hoop 612. The second connecting ear 65 includes a second upper ear 651 located at the lower end of the upper hoop 611 and a second lower ear 652 located at the upper end of the lower hoop 612.

[0055] In the above technical solution, the second upper ear 651 and the second lower ear 652 can be inserted between the first upper ear 631 and the first lower ear 632, further improving the insertion stability.

[0056] The working principle and process of this embodiment are as follows: Drill a well to the target depth within the operation area. After lowering the riser 5, cement the well. After cementing, continue to drill downward from inside the riser 5 to the target depth. After lowering the surface casing 4, cement the well. To improve work efficiency, a marine casing head is usually installed at the beginning of cementing; Place the ring 33 of the base 3 and the support frame 36 on the upper end of the riser 5. The surface casing 4 passes through the ring 33 and the cylinder 361 of the support frame 36; Place the slip hanger 2 on the support ring 362 of the support frame 36, and then sequentially pass the threaded rod 34 through the slip hanger 2 and the support ring 362 and connect the first nut 35; Cover the cover body 31 on the ring 33, slide the sealing ring 32 on the cover body 31, open the operation port 312, and then place the casing head housing 1 on the upper end of the cover body 31. Tighten the first nut 35, and the threaded rod 34 is screwed into the thread groove 11 of the casing head housing 1. The support ring 362 and the slip hanger 2 move upward. When the slip jaws of the slip hanger 2 grip the surface casing 4, the slip seat of the slip hanger 2 and the support ring 362 rise to the limit state. At this time, the first nut 35 tightly abuts against the lower end of the support ring 362 and cannot be tightened further, completing the connection and fixation of the slip hanger 2, the cover body 31, and the casing head housing 1; Slide the sealing ring 32 on the cover body 31 to seal the operation port 312, and use the clamp 6 to lock the cover body 31, the sealing ring 32, the ring 33, and the riser 5; Continue to drill downward from inside the surface casing 4 to the target depth, lower the production casing, and install a slip hanger 7 inside the casing head housing 1 to make the slip hanger 7 grip the production casing. Embodiment 2

[0057] This embodiment provides a method for using a marine casing head, including the following steps:

[0058] Step S100, Drill a well to the target depth within the operation area. After lowering the riser 5, cement the well. After cementing, continue to drill downward from inside the riser 5 to the target depth. After lowering the surface casing 4, cement the well, and install a marine casing head;

[0059] Step S200: Place the ring 33 of the base 3 on the upper end of the riser 5, and pass the surface casing 4 through the ring 33; place the slip hanger 2 above the ring 33, then pass the threaded rod 34 through the slip hanger 2 and connect the first nut 35; cover the cover body 31 on the ring 33, slide the sealing ring 32 on the cover body 31, open the operation port 312, then place the casing head housing 1 on the upper end of the cover body 31, and screw the first nut 35. The threaded rod 34 is screwed into the thread groove 11 of the casing head housing 1, and the slip hanger 2 moves upward. When the slip teeth of the slip hanger 2 hold the surface casing 4 tightly, the slip seat of the slip hanger 2 rises to the limit state, and the first nut 35 cannot be screwed further, completing the connection and fixation of the slip hanger 2, the cover body 31 and the casing head housing 1; slide the sealing ring 32 on the cover body 31 to seal the operation port 312, and connect and fix the cover body 31 and the sealing ring 32 to the ring 33, and at the same time connect and fix the ring 33 and the riser 5.

[0060] Step S300: Continue to drill down inside the surface casing 4 to the target depth, lower the production casing, and install a slip hanger 7 inside the casing head housing 1 to make the slip hanger 7 hold the production casing tightly.

[0061] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A marine casing head, comprising a casing head housing (1) and a base (3), characterized in that, The base (3) includes a housing (31) with an open bottom. The upper end of the housing (31) is provided with a central hole (311), and an operation port (312) is provided below the side wall. The lower end is detachably connected to a ring (33). The lower end of the ring (33) is hermetically connected to a riser pipe (5). A sealing ring (32) is hermetically sleeved on the housing (31) and can slide. Its side wall can block the operation port (312), and its lower end can hermetically dock with the ring (33). The top of the housing (31) is hermetically docked with a casing head housing (1), and an inverted slip hanger (2) is arranged inside. A threaded rod (34) passes through the inverted slip hanger (2) and the housing (31), and its upper end is screwed into a threaded groove (11) on the lower end face of the casing head housing (1), and its lower end is screwed with a first nut (35).

2. The marine casing head according to claim 1, characterized in that, A number of first axial holes (21) for the threaded rod (34) to pass through are equidistantly arranged in the circumferential direction of the inverted slip hanger (2). A number of second axial holes (313) for the threaded rod (34) to pass through are equidistantly arranged in the circumferential direction of the housing (31). A first sealing ring (12) is arranged between the casing head housing (1) and the surface casing (4). A slip hanger (7) for hanging the oil layer casing is arranged inside the casing head housing (1), and a setscrew (13) for pressing the slip hanger (7) is arranged radially. A second sealing ring (14) for sealing the casing head housing (1) and the oil layer casing is arranged above the slip hanger (7).

3. The marine casing head according to claim 2, characterized in that, A third sealing ring (314) is arranged between the housing (31) and the casing head housing (1), and the third sealing ring (314) is arranged outside the threaded rod (34). A fourth sealing ring (331) is arranged between the ring (33) and the sealing ring (32), and a fifth sealing ring (332) is arranged between the ring (33) and the riser pipe (5).

4. A marine casing head according to claim 3, characterized in that, The base (3) further includes a support frame (36). The support frame (36) includes a cylinder (361) and a support ring (362). The cylinder (361) is fixed to the upper end of the ring (33), and its inner wall fits the surface casing (4). A number of sliding holes (3611) are equidistantly arranged in the axial circumferential direction. The lower end of the support ring (362) is provided with a sliding rod (3621) matching the sliding holes (3611). A third axial hole (3622) for the threaded rod (34) to pass through is arranged axially. The upper end is provided with an inverted slip hanger (2), and the lower end is provided with a first nut (35).

5. The marine casing head according to claim 4, characterized in that, The operation port (312) extends upward from the lower end of the housing (31). The lower end of the housing (31) extends radially outward to form a first flange (316). The sealing ring (32) slides vertically on the inner side wall of the housing (31), and the lower end extends radially outward to form a second flange (321). A damping sealing ring (315) is arranged between the housing (31) and the sealing ring (32), and the damping sealing ring (315) is arranged above the operation port (312).

6. The marine casing head according to claim 5, characterized in that, The upper end of the riser pipe (5) extends radially outward to form a third flange (51). The housing (31), the sealing ring (32), the ring (33) and the riser pipe (5) are connected and fixed by a clamp (6).

7. The marine casing head according to claim 6, characterized in that, The clamp (6) includes two semi-circular clamps (61) that can form a circular ring. The inner wall of the semi-circular clamp (61) is provided with an annular slot (62) for inserting the first flange (316), the second flange (321), the ring (33), and the third flange (51). At the circumferential two ends of one semi-circular clamp (61), a first connecting ear (63) and a first slot (64) are respectively provided. At the circumferential two ends of the other semi-circular clamp (61), a second connecting ear (65) that can be inserted into the first slot (64) and a second slot (66) for inserting the first connecting ear (63) are respectively provided. A first bolt (67) passes through the first connecting ear (63) and the second connecting ear (65) and then connects to a second nut (68).

8. The marine casing head according to claim 7, characterized in that, The semi-circular clamp (61) includes an upper clamp (611) and a lower clamp (612). A second bolt (613) passes through the centers of the upper clamp (611) and the lower clamp (612) and then connects to a third nut (614). The outer wall of the upper clamp (611) is provided with a semi-circular limiting wall (6111) extending downward. The outer wall of the lower clamp (612) can slide up and down in contact with the inner wall of the limiting wall (6111). The annular slot (62) includes an upper half-slot (621) located at the lower end of the upper clamp (611) and a lower half-slot (622) located at the upper end of the lower clamp (612).

9. The marine casing head according to claim 8, wherein, The first connecting ear (63) includes a first upper ear (631) located at the upper end of the upper clamp (611) and a first lower ear (632) located at the lower end of the lower clamp (612). The second connecting ear (65) includes a second upper ear (651) located at the lower end of the upper clamp (611) and a second lower ear (652) located at the upper end of the lower clamp (612).

10. A method for using a marine casing head, characterized in that, Using the marine casing head according to any one of claims 2-9, includes the following steps: Step S100, drill to the target depth in the operation area, lower the riser (5) and then cement the well. After cementing, continue to drill downward from the inside of the riser (5) to the target depth, lower the surface casing (4) and then cement the well, and install the marine casing head; Step S200: Place the ring (33) of the base (3) on the upper end of the riser (5), and pass the surface casing (4) through the ring (33); place the slip hanger (2) above the ring (33), then pass the threaded rod (34) through the slip hanger (2) and connect the first nut (35); place the cover body (31) over the ring (33), slide the sealing ring (32) on the cover body (31), open the operation port (312), then place the casing head housing (1) on the upper end of the cover body (31), and screw the first nut (35). The threaded rod (34) is screwed into the thread groove (11) of the casing head housing (1), and the slip hanger (2) moves upward. When the slip teeth of the slip hanger (2) grip the surface casing (4), the slip seat of the slip hanger (2) rises to the limit state, and the first nut (35) cannot be screwed further, thus completing the connection and fixation of the slip hanger (2), the cover body (31), and the casing head housing (1); slide the sealing ring (32) on the cover body (31) to seal the operation port (312), and connect and fix the cover body (31) and the sealing ring (32) to the ring (33), while connecting and fixing the ring (33) and the riser (5). Step S300: Continue to drill downward from the inside of the surface casing (4) to the target depth, lower the production casing, and install a slip hanger (7) inside the casing head housing (1) to make the slip hanger (7) grip the production casing.

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