BACKGROUND

Field of the Disclosure

[0001] Embodiments of this disclosure generally relate to a swivel for use in wellbore drilling and completion operations.

Description of the Related Art

[0002] In wellbore drilling and completion operations, a swivel is used to direct a pressurized fluid, such as drilling mud or cement, into a work string, while transmitting rotation to the work string. The work string can include one or more tubular members, such as drill pipe or casing, which are coupled together below the swivel and extend into a wellbore. A top drive provides the rotation that is transmitted to the work string by the swivel.

[0003] One or more seals contain the pressurized fluid within the swivel while the swivel transmits rotation to the work string. The seals are exposed to atmospheric pressure on one side and are exposed to the pressurized fluid on the opposite side, which creates a pressure differential across the seals. The seals will fail and leak when the pressure differential exceeds a predetermined amount. Thus, the pressure at which the pressurized fluid can be supplied is limited by the seals.

[0004] There is a need, therefore, for a swivel that can accommodate pressurized fluids at high pressures while minimizing the risk of seal failure.

SUMMARY

[0005] A swivel comprising an inner mandrel disposed through an outer housing; a plurality of seals disposed between the inner mandrel and the outer housing; and a pressure reducing assembly configured to control a pressure differential across the plurality of seals.

[0006] A swivel comprising an outer housing; an inner mandrel disposed through and rotatable relative to the outer housing; a first seal disposed between the inner mandrel and the outer housing, wherein a first sealed area and a second sealed area are formed on opposite sides of the first seal and are filled with hydraulic fluid; and a piston disposed within a body coupled to the outer housing, wherein a lower surface of the piston is in fluid communication with the first sealed area, wherein an upper surface of the piston is in fluid communication with the second sealed area, and wherein the lower surface of the piston has a surface area that is less that a surface area of the upper surface of the piston.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] So that the manner in which the above recited features can be understood in detail, a more particular description of the embodiments briefly summarized above may be had by reference to the embodiments below, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments and are therefore not to be considered limiting of its scope, for the embodiments may admit to other equally effective embodiments.

[0008] Figure 1 illustrates a swivel, according to one embodiment disclosed herein.

[0009] Figure 2 illustrates a sectional view of the swivel, according to one embodiment disclosed herein.

[0010] Figure 3 illustrates an enlarged sectional view of an upper portion of the swivel, according to one embodiment disclosed herein.

DETAILED DESCRIPTION

[0011] Figure 1 illustrates a swivel 100, according to one embodiment disclosed herein. The swivel 100 includes an inner mandrel 10 disposed through and rotatable relative to an upper housing 20, an intermediate housing 30, and a lower housing 40. According to one example, the inner mandrel 10 transmits rotation from a top drive to a work string; the top drive being coupled to an upper end of the inner mandrel 10 and the work string being coupled to a lower end of the inner mandrel 10. The work string can include one or more tubular members, such as drill pipe or casing, which are coupled together below the swivel 100 and extend into a wellbore. [0012] The upper housing 20 is coupled to an upper end of the intermediate housing 30, such as by a welded, bolted, and/or threaded connection. The lower housing 40 is coupled to a lower end of the intermediate housing 30, such as by a welded, bolted, and/or threaded connection. A fluid inlet 50 is coupled to the intermediate housing 30, such as by a welded, bolted, and/or threaded connection, and directs pressurized fluid into the interior of the intermediate housing 30.

[0013] A first pressure reducing assembly 60A is coupled to the upper housing 20. A second pressure reducing assembly 60B is coupled to the lower housing 40. The pressure reducing assemblies 60A, 60B are configured to reduce the pressure differential formed across one or more seals disposed within the upper and lower housings 20, 40, respectively, as further described below with respect to Figure 3.

[0014] Figure 2 illustrates a sectional view of the swivel 100, according to one embodiment disclosed herein. A flow bore 15 disposed along the longitudinal length of the inner mandrel 10, and one or more openings 17 are disposed through the sidewall of the inner mandrel 10. The openings 17 provide fluid communication between the interior of the intermediate housing 30 and the flow bore 15 of the inner mandrel 10. An opening 35 is disposed through the sidewall of the intermediate housing 30 and is in fluid communication with a flow bore 55 of the fluid inlet 50.

[0015] A pressurized fluid (identified by reference arrow "A"), such as drilling mud or cement, is supplied through the flow bore 55 of the fluid inlet 50, into the interior of the intermediate housing 30 via the opening 35, and into the flow bore 15 of the inner mandrel 10 via the openings 17. A first floating seal assembly 70A is supported within the lower end of the upper housing 20 and within the upper end of the intermediate housing 30 to separate the pressurized fluid supplied into the interior of the intermediate housing 30 from hydraulic oil contained within the upper housing 20. Similarly, a second floating seal assembly 70B is supported within the upper end of the lower housing 40 and within the lower end of the intermediate housing 30 to separate the pressurized fluid supplied into the interior of the intermediate housing 30 from hydraulic oil contained within the lower housing 40.

[0016] The first pressure reducing assembly 60A is configured to reduce the pressure differential across a first plurality of seals 80A disposed within the upper housing 20 and around the outer surface of the inner mandrel 10 as further described herein with respect to Figure 3. Similarly, the second pressure reducing assembly 60B is configured to reduce the pressure differential across a second plurality of seals 80B disposed within the lower housing 40 and around the outer surface of the inner mandrel 10. An upper bearing assembly 90A, such as a bushing or ball/roller bearing, is supported within the upper housing 20, and a lower bearing assembly 90B, such as a bushing or ball/roller bearing, is supported within the lower housing 40 to minimize friction against the inner mandrel 10 when rotating relative to the upper and lower housings 20, 40.

[0017] Figure 3 illustrates an enlarged sectional view of an upper portion of the swivel 100, according to one embodiment disclosed herein. The description of the operation of the first pressure reducing assembly 60A, the first floating seal assembly 70A, and the first plurality of seals 80A in Figure 3 similarly applies the operation of the second pressure reducing assembly 60B, the second floating seal assembly 70B, and the second plurality of seals 80B shown in Figure 2. The embodiments of the first pressure reducing assembly 60A, the first floating seal assembly 70A, and the first plurality of seals 80A are equally applicable to the second pressure reducing assembly 60B, the second floating seal assembly 70B, and the second plurality of seals 80B shown in Figure 2

[0018] As illustrated in Figure 3, the first floating seal assembly 70A includes a floating seal 71 and a floating seal carrier 72 disposed between the outer surface of the inner mandrel 10 and the inner surfaces of the upper housing 20 and the intermediate housing 30. An additional seal may be positioned between the seal carrier 72 and the upper housing 20 and/or intermediate housing 30. The first floating seal assembly 70A forms a seal between and is movable axially relative to the inner mandrel 10, the upper housing 20, and the intermediate housing 30. The first floating seal assembly 70A prevents the flow of pressurized fluid (identified by reference arrow "A") supplied into the intermediate housing 30 via the fluid inlet 50 from flowing up across the first floating seal assembly 70 further into the interior of the upper housing 20 and potentially leaking out of the upper housing 20.

[0019] The first plurality of seals 80A includes a first seal 81 supported by a first seal carrier 82, a second seal 83 supported by a second seal carrier 84, a third seal 85 supported by a third seal carrier 86, and a fourth seal 87 supported by the upper housing 20. Additional seals may be positioned between the seal carriers 82, 84, 86 and the upper housing 20. When forced in an upward direction by pressurized fluid, the seal carriers 82, 84, 86 may engage one or more inner shoulders of the upper housing 20 to prevent further upward movement of the seal carriers. The first plurality of seals 80A are disposed and form a seal between the outer surface of the inner mandrel 10 and the inner surface of the upper housing 20. Although the plurality of seals 80 is illustrated with only four seals as shown in Figure 3, any number of seals can be used with the embodiments described herein.

[0020] A sealed area 21 formed between the floating seal 71 , the first seal 81 , the outer surface of the inner mandrel 10, and the inner surface of the upper housing 20 is filled with fluid and is in fluid communication with a fluid path 25 disposed through the sidewall of the upper housing 20. A sealed area 22A formed between the first seal 81 , the second seal 83, the outer surface of the inner mandrel 10, and the inner surface of the upper housing 20 is filled with fluid and is in fluid communication with a fluid path 26A disposed through the sidewall of the upper housing 20. A sealed area 22B formed between the second seal 83, the third seal 85, the outer surface of the inner mandrel 10, and the inner surface of the upper housing 20 is filled with fluid and is in fluid communication with a fluid path 26B disposed through the sidewall of the upper housing 20. Finally, a sealed area 22C formed between the third seal 85, the fourth seal 87, the outer surface of the inner mandrel 10, and the inner surface of the upper housing 20 is filled with fluid and is in fluid communication with a fluid path 26C disposed through the sidewall of the upper housing 20. [0021] The first pressure reducing assembly 60A includes a body 61 coupled to the exterior of the upper housing 20, and a first piston 62A, a second piston 62B, and a third piston 62C disposed within the body 61 . The first, second, and third pistons 62A, 62B, 62C each have a lower surface 63A, 63B, 63C that has a surface area that is less than a surface area of an upper surface 64A, 64B, 64C, respectively. Although each of the lower surfaces 63A, 63B, 63C are illustrated as having the same lower surface area, the lower surfaces 63A, 63B, 63C may have different lower surface areas. Although each of the upper surfaces 64A, 64B, 64C are illustrated as having the same upper surface area, the upper surfaces 64A, 64B, 64C may have different upper surface areas. In one embodiment, each of the pistons 62A, 62B, 62C may include at least two seals (one seal across the larger upper diameter and one seal across the smaller lower diameter) positioned between the inner surface of the body 61 and the outer surfaces of the pistons 62A, 62B, 62C. In one embodiment, a reservoir may be included to supply hydraulic fluid into the areas between the at least two seals when the pistons 62A, 62B, 62C move upward, to prevent a vacuum from being formed between the at least two seals.

[0022] A fluid path 67 disposed in the body 61 communicates fluid between an area above the upper surface 64A of the first piston 62A and an area below the lower surface 63B of the second piston 62B. A fluid path 68 disposed in the body 61 communicates fluid between an area above the upper surface 64B of the second piston 62B and an area below the lower surface 63C of the third piston 62C. Although the first pressure reducing assembly 60A is illustrated with only three pistons as shown in Figure 3, any number of pistons can be used with the embodiments described herein. In one embodiment, any one of the first, second, and third pistons 62A, 62B, 62C may be biased by a biasing member, such as a spring, in the downward direction.

[0023] The body 61 includes fluid paths 66A, 66B, 66C that are in fluid communication with fluid paths 26A, 26B, 26C, respectively, of the upper housing 20 to communicate fluid between the sealed areas 22A, 22B, 22C and the upper surfaces 64A, 64B, 64C of the first, second, and third pistons 62A, 62B, 62C, respectively. The body further includes a fluid path 65 that is in fluid communication with the fluid path 25 of the upper housing 20 to communicate fluid between the sealed area 21 and the lower surface 63A of the first piston 62A. One or more seals can be positioned between the body 61 and the upper housing

20. To prevent leakage between the various fluid paths, one or more seals can be positioned in the spaces between the fluid paths 25, 65 and the fluid paths 26A, 66A, between the fluid paths 26A, 66A and the fluid paths 26B, 66B, and the fluid paths 26B, 66B and the fluid paths 26C, 66C.

[0024] In one embodiment, the areas above and below the first, second, and third pistons 62A, 62B, 62C, the fluid paths 65, 67, 68, 66A, 66B, 66C disposed in and through the body 61 , the fluid paths 25, 26A, 26B, 26C disposed through the sidewall of the upper housing 20, and the sealed areas 21 , 22A, 22B, 22C can be sized and filled enough hydraulic fluid, such as oil, to accommodate for any leakage experienced across any of the seals during operation of the swivel 100. According to one example, when the inner mandrel 10 is rotating, the first, second, third, and fourth seals 81 , 83, 85, 87 are designed to allow a small amount of hydraulic fluid to seep across the seals 81 , 83, 85, 87 such that a thin lubricating film is formed between the seals 81 , 83, 85, 87 and the outer surface of the inner mandrel 10. The thin lubricating film minimizes friction and prevents wear of the first, second, third, and fourth seals 81 , 83, 85, 87.

[0025] The areas above and below the first, second, and third pistons 62A, 62B, 62C, the fluid paths 65, 67, 68, 66A, 66B, 66C disposed in and through the body 61 , the fluid paths 25, 26A, 26B, 26C disposed through the sidewall of the upper housing 20, and the sealed areas 21 , 22A, 22B, 22C are filled with a hydraulic fluid, such as oil, to form a staged pressure reducing system arranged to manage the pressure differential across the first, second, third, and fourth seals 81 , 83, 85, 87 when pressurized fluid (identified by reference arrow "A") supplied into the intermediate housing 30 is applied to the floating seal assembly 70A. Specifically, the pressurized fluid applies a force to the floating seal assembly 70A, which applies a force to the hydraulic fluid disposed within the sealed area

21 . The hydraulic fluid in the sealed area 21 and the fluid paths 25, 65 is forced against the lower surface 63A of the first piston 62A to move the first piston 62A upward. However, since the areas above the first, second, and third pistons 62A, 62B, 62C, the fluid paths 67, 68, 66A, 66B, 66C, 26A, 26B, 26C, and the sealed areas 22A, 22B, 22C are filled with hydraulic fluid, which is substantially incompressible, the first piston 62A (as well as the second and third pistons 62B, 62C via fluid paths 67, 68) may not move or may move upward only a limited amount before being hydraulically locked against further upward movement.

[0026] When the first, second, and third pistons 62A, 62B, 62C are prevented from moving upward, the pressure in the sealed area 21 above the first floating seal assembly 70A may substantially equalize to the pressure of the pressurized fluid (identified by reference arrow "A") applied to the opposite side of the first floating seal assembly 70A. Since the pressure above the floating seal 71 is substantially equal to the pressure below the floating seal 71 , then there is substantially no pressure differential across the floating seal 71 that can potentially cause the floating seal 71 to fail. The floating seal 71 prevents the pressurized fluid from flowing up across the floating seal assembly 70A and mixing with the hydraulic fluid in the sealed area 21 . In one embodiment, the floating seal assembly 70A may comprise a plurality of seals positioned between the seal carrier 72 and the inner mandrel 10 to accommodate for rotation of the inner mandrel 10, as well as to prevent the pressurized fluid from flowing up across the floating seal assembly 70A and mixing with the hydraulic fluid in the sealed area 21 . In one embodiment, the floating seal assembly 70A may comprise a plurality of seals positioned between the seal carrier 72 and the upper housing 20 and/or the intermediate housing 30 to prevent the pressurized fluid from flowing up across the floating seal assembly 70A and mixing with the hydraulic fluid in the sealed area 21 . In one embodiment, the floating seal assembly 70A may comprise a plurality of seals forming a first seal area across the seal carrier 71 that is less than and positioned above another seal area formed across the seal carrier 71 to generate a pressure within the sealed area 21 that is greater than the pressure below the floating seal assembly 70A when pressurized fluid is supplied into the swivel 100.

[0027] The first piston 62A controls the pressure differential across the first seal 81 in the following way. The first piston 62A will experience an upward force when pressure builds in the sealed area 21 , as described above, and is exerted on the lower surface 63A of the first piston 62A. This upward force causes the first piston 62A to move upwards until the upward force is balanced by an equal and opposite downward force caused by the compression of the fluid occupying the space above the first piston 62A, the fluid paths 67, 66A, 26A, and the sealed area 22A. This downward force results from the compression of this fluid causing the pressure of the fluid to rise, and this pressure is exerted on the upper surface 64A of the first piston 62A. When the upward and downward forces acting on the first piston 62A are balanced, the pressure of the fluid in the space above the first piston 62A, the fluid paths 67, 66A, 26A, and the sealed area 22A is equal to the pressure of the fluid in the space below the first piston 62A, the fluid paths 65, 25, and the sealed area 21 multiplied by the ratio of surface areas of the lower surface 63A to the upper surface 64A. Since in the illustrated embodiment the lower surface 63A has a smaller area than the upper surface 64A, the pressure of the fluid in the space above the first piston 62A, the fluid paths 67, 66A, 26A, and the sealed area 22A will be lower than the pressure of the fluid in the space below the first piston 62A, the fluid paths 65, 25, and the sealed area 21 . By designing appropriate areas for the lower surface 63A and upper surface 64A of first piston 62A, the ratio of the pressure in the sealed area 21 to the pressure in the sealed area 22A, and hence the pressure differential experienced by first seal 81 may be controlled.

[0028] In one embodiment it may be desirable to limit the maximum pressure differential experienced by any one of seals 81 , 83, 85 and 87. As noted above, the actual pressures experienced in sealed areas 22A, 22B and 22C are derived from the ratios of lower to upper piston surface areas (63A:64A, 63B:64B, 63C:64C) multiplied by the respective pressures in the sealed areas 21 , 22A and 22B. As an example, consider the pressure within the sealed area 21 to be designated P1 , the pressure within the sealed area 22A to be designated P2, the surface area of the lower surface 63A of the first piston 62A to be designated A1 , and the surface area of upper surface 64A of the first piston 62A to be designated A2.

[0029] The pressure P2 may be calculated as follows: [0030] P2 = P1 x (A1/A2) [Equation 1 ]

[0031] Furthermore, the pressure differential (designated ΔΡ and equal to P1 - P2) experienced by the seal 81 is given as follows:

[0032] ΔΡ = P1 - P2 = P1 x (1 - (A1/A2)) [Equation 2]

[0033] Therefore, the pressure differential is proportional to the value of the pressure within the sealed area 21 (P1 ). In one embodiment, it is advantageous to specify a maximum pressure differential (designated APmax) to be experienced by the seal 81 , and a maximum value for pressure P1 in space 21 . As an example, this maximum value (designated P1 max) may be specified to be a value equal to or greater than the maximum working or test pressure for swivel 100.

[0034] From Equation 2, it follows that:

[0035] APmax = P1 max x (1 - (A1/A2)) [Equation 3]

[0036] Since both APmax and P1 max are both specified quantities, it is possible to rearrange Equation 3 to solve for the desired ratio of lower:upper surface areas for first piston 62A, thus:

[0037] A1/A2 = 1 - (APmax/P1 max) [Equation 4]

[0038] If there is any known size constraint for either the lower surface area A1 or the upper surface area A2, then the appropriate value of the other surface area can be determined accordingly.

[0039] Having configured the sizes of the upper and lower surface areas (A2, A1 ) of first piston 62A, the sizes of the other pistons (62B, 62C) may be configured in a similar way. In one embodiment, one or more piston may be configured to have upper and lower surface areas sized differently from corresponding areas of another piston. In this way, when a maximum pressure inside the swivel 100 is reached, each seal 81 , 83, 85 and 87 may be subject to differential pressures equal to or less than their prescribed maxima.

[0040] Similarly, the lower surface 63B and the upper surface 64B of the second piston 62B can be sized to control the amount of pressure reduction from the sealed area 22A to the sealed area 22B, thereby controlling the pressure differential across the second seal 83. The lower surface 63C and the upper surface 64C of the third piston 62C also can be sized to control the amount of pressure reduction from the sealed area 22B to the sealed area 22C, thereby controlling the pressure differential across the third seal 85. The pressure differential across the fourth seal 87 will be the difference between the pressure in the sealed area 22C and the pressure external to the entire swivel 100 (usually atmospheric pressure).

[0041] The first and second pressure reducing assemblies 60A, 60B can be used to selectively stage a pressure reduction across the first and second plurality of seals 80A, 80B from the pressure at which the pressurized fluid (identified by reference arrow "A") is supplied into the intermediate housing 30 out to the pressure external to the entire swivel 100 (usually atmospheric pressure). The pressure differential across any of the first and second plurality of seals 80A, 80B is controlled to prevent failure of the first and second plurality of seals 80A, 80B. The first and second plurality of seals 80A, 80B can include any number of seals, and the first and second pressure reducing assemblies 60A, 60B can include any number of pistons arranged to selectively reduce the pressure within the swivel 100 as described above.

[0042] While the foregoing is directed to certain embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.