Wireline sealing assembly

Abstract

A wireline sealing assembly adapted to seal a line such as wireline or slickline deployed in an oil or gas well has a body to receive a line and a seal adapted to be actuated into sealing engagement with the line to contain wellbore pressure within the well below the actuated seal. The seal comprises first and second seal members, each seal member comprising at least one sealing element, wherein the first and second seal members are formed of different materials. The second seal member may have a greater hardness rating or lower degree of resilience that the first seal member. The first and second seal members may radially deform against the line when the seal is actuated, and the first seal member may radially deform more than the second seal member. The seal may also comprise a third seal member comprising at least one sealing element, wherein the third seal member is formed of a different material to the first and second seal members.

Claims

1. A wireline sealing assembly comprising a body configured to receive a line for deployment in a well, and a seal adapted to be actuated into sealing engagement with the line in the body to contain wellbore pressure within the well below the actuated seal, wherein the seal comprises first, second, and third seal members, the first seal member comprising at least one first sealing element, and the second seal member comprising at least two second sealing elements arranged on opposite sides of the first seal member, and wherein the first and second seal members are formed of different materials, wherein the third sealing member comprises at least two third sealing elements, the third sealing elements being formed of a different material to at least one of the first and second seal members, and the third sealing elements being arranged in a stack of sealing elements in alignment with and abutting outer faces of the second sealing elements of the second seal member, wherein each of the first, second and third seal members has an aperture to accommodate the line, and wherein the aperture of the second seal member is smaller than the apertures of the first and third seal members.

2. The wireline sealing assembly as claimed in claim 1, wherein the first sealing element and the second sealing element are resilient.

3. The wireline sealing assembly as claimed in claim 1, wherein the second sealing element of the second seal member has a greater hardness rating than the first sealing element of the first seal member.

4. The wireline sealing assembly as claimed in claim 1, wherein when the seal is subjected to actuating pressure, both of the first and second seal members are adapted to deform in a radial direction against the line, and wherein the first sealing element of the first seal member is adapted to deform in a radial direction more than the second sealing element of the second seal member.

5. The wireline sealing assembly as claimed in claim 1, wherein the third seal member has a greater hardness rating than the first or second seal members.

6. The wireline sealing assembly as claimed in claim 1, wherein the first seal member comprises a plurality of at least two first sealing elements, and wherein each of said first sealing elements are elastomeric.

7. The wireline sealing assembly as claimed in claim 6, wherein the first sealing elements are arranged in a stack where at least two of the plurality of first sealing elements are adjacent to each other and contiguous within the stack, and wherein the first sealing elements are aligned within the stack.

8. The wireline sealing assembly as claimed in claim 1, wherein at least one first sealing element of the first seal member is disposed in a central portion of the seal, at least one third sealing element of the third seal member is disposed on at least one outer portion of the seal, and the second sealing element of the second seal member is disposed between the first seal member and the third seal member.

9. The wireline sealing assembly as claimed in claim 1, wherein the first and second sealing elements are arranged in a stack which has axial symmetry along an axis of a path of the line.

10. The wireline sealing assembly as claimed in claim 1, wherein the second seal member is contiguous with the first seal member.

11. The wireline sealing assembly as claimed in claim 1, wherein a coefficient of friction of the material of the second seal member is lower than a coefficient of friction of the material of the first seal member.

12. The wireline sealing assembly as claimed in claim 1, wherein each of the first and second seal members has an aperture to accommodate the line, and wherein the aperture of the second seal member is smaller than the aperture of the first seal member.

13. The wireline sealing assembly as claimed in claim 1, wherein an inner surface of the aperture of the second seal member engages and wears against an outer surface of the line.

14. A wireline sealing assembly comprising a body configured to receive a line for deployment in a well and a seal adapted to be actuated into sealing engagement with the line in the body to contain wellbore pressure within the well below the actuated seal, wherein the seal comprises first, second, and third seal members, the first seal member comprising at least one first sealing element, and the second seal member comprising at least two second sealing elements arranged on opposite sides of the first seal member, and wherein the first and second seal members are formed of different materials, wherein the third seal member comprises at least two third sealing elements, the third sealing elements being formed of different material to one of the first and second seal members, and the third sealing elements being arranged in a stack of sealing elements in alignment with and abutting outer faces of the second sealing elements of the second seal member, wherein the third sealing elements of the third seal member are formed of a metal alloy which deforms less than the second and first seal members in response to the same actuation force.

15. A method of deploying a wireline in a well, the method comprising passing the wireline through a wireline sealing assembly comprising a body configured to receive a line for deployment in a well, and a seal adapted to be actuated into sealing engagement with the line in the body to contain wellbore pressure within the well below the actuated seal, and actuating the seal to contain wellbore pressures within the well while permitting movement of the wireline relative to the seal, wherein the seal comprises first second, and third seal members, the first seal member comprising at least one elastomeric sealing element, and the second seal member comprising at least two second sealing elements arranged on opposite sides of the first seal member, and wherein the first and second seal members are formed of different materials, wherein the third seal member comprises at least two third sealing elements, the third sealing elements being formed of a different material to one of the first and second seal members, and the third sealing elements being arranged in a stack of sealing elements in alignment with and abutting outer faces of the second sealing elements of the second seal member, wherein each of the first, second and third seal members has an aperture to accommodate the line, and wherein the aperture of the second seal member is smaller than the apertures of the first and third seal members.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the accompanying drawings:

(2) FIG. 1 shows a side sectional view of a sealing assembly;

(3) FIG. 2 shows a side sectional view similar to FIG. 1 with a slickline cable deployed through the sealing assembly into a well;

(4) FIG. 3 shows a close up view of FIG. 1 showing a stack of sealing elements;

(5) FIG. 4 shows a plan view of a first sealing element; and

(6) FIG. 5 shows a plan view of a second sealing element.

DETAILED DESCRIPTION

(7) Referring now to the drawings, one example of a sealing assembly shown in FIG. 1 comprises a body having an upper body 1U and a lower body 1L having a central longitudinal axis and connected by a piston arranged in an upper piston 10U and lower piston 10L which is adapted to slide axially with respect to the body 1. The body 1 has a central axial bore 1B, which receives a line such as a wireline or slickline S adapted to be deployed in the well. The central bore 1B extends through both upper and lower parts of the body 1 and through the piston 10 guiding the line S along a straight pathway through the sealing assembly, as shown in FIG. 2.

(8) The sealing assembly has a pair of seals 50U, 50L which seal the annulus between the inner surface of the body 1 and the outer surface of the line S. In this example, each seal 50U, 50L comprises a stack of sealing elements, and in this example, each seal 50U, 50L is substantially the same. Hence only the lower seal 50L will be described in detail.

(9) Referring to FIG. 3, the lower seal 50L comprises an axial stack of sealing elements, in a symmetrical arrangement along the axis of the central bore 1B. The stack has an upper end and a lower end, and a central portion. The central portion of the stack comprises the first seal member, which in this case comprises three contiguous elastomeric sealing elements 51 arranged in contact with one another in the stack. The elastomeric sealing elements 51 are circular and have a central aperture 51A aligned with the bore 1B and a scarf cut 51S between their radially outer surfaces and inner surfaces. The sealing elements 51 are formed from elastomeric material such as rubber, which is resilient and is adapted to expand resiliently into the aperture 51A upon axial compression of the sealing element 51 along the axis of the path of the line S (i.e. along the bore 1B). The scarf cuts 51S are provided to permit replacement of the sealing elements 51 without removing the other parts of the sealing assembly, and are optionally staggered out of phase with one another in the stack to reduce the extent of leakage through the scarf cuts when the seal 50L is actuated.

(10) Referring to FIG. 4, the central aperture 51A of the sealing elements 51 has a nominal diameter creating an annulus (optionally of around 8-12% of line diameter in this example) between the inner surface of the sealing elements 51 and the outer surface of the line S when the line S is received in the sealing assembly. In this example, the clearance between the line and the inner surface of the sealing elements 51 is sufficient to permit the sealing elements 51 to resiliently recover back to their pre-energised states when the actuating force is removed.

(11) The sealing elements 51 are sandwiched between a pair of second sealing elements 52U, 52L forming a second seal member, with one second sealing element 52U above the sealing elements 51, and one 52L below. The second sealing elements 52U, 52L are formed of a different material to the elastomeric sealing elements 51, and in this case are formed from PTFE. The second sealing elements 52U, 52L above and below the stack of first sealing elements 51 have a similar shape to the first elements 51, but do not in this example have a scarf cut, as they are less frequently replaced.

(12) The PTFE material of the second sealing elements is able to resiliently deform and recover to its original shape when subjected to actuation force, but the degree of resilience of the second sealing elements 52U, 52L is lower in the second sealing element than in the first, and the second sealing element is harder than the first sealing element, so under the same deforming force applied to both, the first elastomeric sealing elements 51 deform radially inwards into the bore 1B more than the second sealing elements 52U, 52L.

(13) Referring to FIG. 5, the apertures 52A of the second sealing elements 52U, 52L are typically narrower than the apertures 51A of the first sealing elements 51, and have a closer tolerance to the outer diameter of the line S (optionally around 1-3% in this example) so that upon axial compression of the seal 50L, both the first and second sealing elements deform resiliently, but the first elements 51 deform more than the second elements 52U, 52L. Under the deforming force, the apertures 52A of the second elements 52U, 52L reduce in diameter, and advantageously compresses around the entire circumference of the line S, rubbing against it around the whole outer circumference, therefore closing the available gap for extrusion of the first sealing elements under the actuating force to a small gap approaching zero, and optionally closing the cap completely. The material of the second sealing elements 52U, 52L typically has a low coefficient of friction, typically lower than the material of the first sealing elements 51, but optionally each of the sealing elements 51, 52U, 52L can comprise a low friction material. Hence, the line S can typically slide easily against the material of the second sealing elements 52U, 52L, which typically wear sacrificially as a result of rubbing against the line S around its circumference.

(14) On the outer surfaces of the second sealing elements 52U, 52L, there is a pair of third sealing elements 53U, 53L, formed of another different material, in this case, from an alloy such as Aluminium Bronze. The third sealing elements do not substantially deform in response to applied force during actuation.

(15) The upper and lower seals 50U, 50L are typically energised by axial compression by a hydraulic piston although other methods are possible. Each seal 50U, 50L is optionally energised by the same hydraulic force, although each could be under the control of a separate hydraulic circuit. When the hydraulic piston is actuated, optionally by control from the surface, the piston is driven axially in the body to compress the seals 50U, 50L and cause each of the first and second sealing elements 51, 52U, 52L to deform radially inwards against the line S to seal the annulus between the line S and the body 1. This contains the wellbore pressure.

(16) Because the sealing elements 51, 52U, 52L are made of different materials, each deforms to a different extent, and this enables the apertures 52A in the second sealing elements 52U, 52L to be closely toleranced to the line S, while the apertures 51A in the first elements 51 generally have to expand a larger distance to contact the line. Thus, upon deformation of both of the first and second sealing elements 51, 52U, 52L, the inner array of first sealing elements 51 absorbs a large amount of energy during the compression, and this enables the resilient recovery of the first sealing elements 51 back into their pre-energised configurations upon the removal of actuating force. However, the second sealing elements 52U, 52L are less resilient and optionally harder, and deform less in response to the same force, and so in response to the actuating force, the second sealing elements 52U, 52L deform to a lesser extent than the first sealing elements 51 but still close the annulus. Since the second sealing elements 52U, 52L are less resilient than the first sealing elements 51, they contain the first sealing elements and resist extrusion of them through the annular gap. Upon removal of the force actuating the seals 50U, 50L, both the first and second sealing elements resiliently recover to withdraw radially from the outer surface of the line S.

(17) The third sealing elements 53U, 53L do not substantially react to the actuation force by deforming, and the apertures therein remain unchanged, resulting in a very small amount of extrusion of the PTFE material of the second sealing elements 52U, 52L into the apertures of the third sealing elements 53 during actuation. This helps to contain the wellbore pressure within the well.

(18) Because of the different materials in the sealing elements 51, 52U, 52L (and optionally 53U, 53L) the surface pressures on the outer surface of the line S can be controlled to the minimum required to seal and contain the wellbore pressure, which reduces damage on the line S and the sealing elements 51, 52U, 52L, and reduces the force needed to pull the line S through the sealed assembly when running in the hole. As well as reducing general wear on the sealing elements 51, 52U, 52L pressed against the line S, the combination of features reduces the likelihood of extrusion damage to the sealing elements 51, 52U, 52L.

(19) Furthermore, the combination of features allows the construction of sealing assemblies which are easier to control, as the first sealing elements 51 can be constructed to have a larger rebound force reducing the risk of wellbore pressure prematurely activating the seal in the absence of a deliberate actuation force. In some examples, the seals 51 can be constructed with a large annular clearance between the line S and the sealing element 51 so that they need to be radially compressed by some distance and at some force in order to make the seal. This means that the un-energised sealing elements 51 are less susceptible to being inadvertently initiated by well bore pressure applied below the seal, and allows better control over actuation, since the well bore pressure cannot easily over-ride the deliberate hydraulic control, and thus wellbore pressure has less effect on how hard the sealing elements are pressed against the line S. The fact that the sealing elements are less susceptible to inadvertent actuation also minimises wear on the line S and sealing elements 51, 52U, 52L, since the sealing elements 51, 52U, 52L are only activated in response to deliberate actuation.