Patent Application
20190301263
The present invention belongs to the field of oil and gas wells drilling and production of oil and gas from wells drilled on the earth. More particularly it relates to the field of zonal isolation wherein different sections of an oil or gas well are sealingly isolated from other well sections to avoid cross-contamination with fluids such as water, undesired pressure transmission between sections or for other reasons.
In the oil and gas exploration and extraction industries it is often desirable to be able to modulate downhole pressure when required. For example, it may be desirable to isolate a section of well bore to create sections of differential pressure within the bore. A sealing device may be used to create a seal within the bore, such that fluid pressure on one side of the seal increases relative to fluid pressure on the other side. Further, a temporary decrease in well pressure can be used to initiate flow from the reservoir in a process known as ‘swabbing’. One means of doing this is to make use of a swab cup, which is a cup-shaped resilient member which is lowered on a mandrel into the well. As a pressure differential develops across the cup, the walls of the cup are pushed into contact with the well tubing or bore wall, thereby sealing a portion of the well. Thus, the pressure below the cup may decrease, while the pressure above may increase.
Similarly constructed pressure cups are also used in a wide variety of other sealing and fluid lifting applications. For example, variations in pressure may also be used to actuate or to control other downhole tools and instruments which rely on fluid pressure for their operation. Such cups may be constructed with an outer diameter slightly less than the bore diameter, such than an initial inflation is required before a seal is created, or may have an outer diameter slightly larger than that of the bore, such that a seal is present even when the cup is not inflated.
Alternatively, a pressure differential may be achieved by means of a packer. The sealing element on a packer is compressed and activated via a setting load caused by mechanical or hydraulic or other forces. These are used to isolate different parts of the well for numerous downhole operations, such as well testing or completions.
Conventional pressure seals suffer from a number of disadvantages. The seals are usually made from rubber or other elastomer, which must be made relatively thick in order to resist the pressures downhole. This means that such seals may be unsuitable for use at relatively low pressures, since they will not seal the well effectively under these conditions. The relatively thick elastomer can also suffer from slow recovery times after pressure has been removed. Seals may be reinforced in order to resist higher pressures with metal or wire hoops or rings embedded within the elastomer; however, this can lead to shear failure of the elastomer, with the reinforcing wire cutting through the elastomer.
In addition, conventional seals may only operate over a restricted range of pressures and temperatures, and with a small gap between the seal and the bore wall. If the gap between the seal and the bore is increased, the pressure that the seal will hold drops considerably.
Further, elastomers under pressure can flow or extrude in certain conditions. This may arise in seals or packers, and will reduce the effectiveness of such seals or packers, because elastomer flows or extrudes while the seal is under pressure. Any tendency to flow or extrude is also exacerbated at higher temperatures.
According to a first aspect of the present invention, there is provided a pressure control device for mounting on a mandrel, the device comprising:
a flexible sealing element;
a first support member; and
a second support member comprising a composite,
wherein the pressure control device is adapted to move from a run in position to an expanded position when exposed to a source of pressure, the flexible sealing element is adapted to form a seal against a bore wall in the expanded position, the first and second support members being adapted, in the expanded position, to resist extrusion of the flexible sealing element, in use, along the bore wall away from the source of pressure, the second support member being further adapted to resist extrusion into the first support member.
In at least one embodiment of the present invention an apparatus as described above is able to sealingly isolate two sections of an oil or gas well and at the same time maintain its integrity under wellbore pressure differentials, thus preventing extrusion and deformation of the flexible sealing element and of the second support member and therefore maintaining the seal leak-free. This invention is particularly suitable to achieve effective zonal isolation under extreme pressures and temperatures, such as those encountered in high pressure, high temperature wells (HPHT wells).
Furthermore, by provision of a second support member in the form of a composite, extrusion into the first support member of flexible sealing element material or second support member material is resisted, allowing for greater recovery of the first support member, when the source of pressure is released, towards the run in position.
The pressure control device may be a cup seal or a swab cup.
Alternatively, the pressure control device may be a packer or any suitable pressure control device comprising a flexible sealing element.
A portion of the flexible sealing element, the first support member and/or the second support member may be arranged concentrically.
The first support member may further comprise a circumferential spring.
The circumferential spring may be biased to the run-in position.
The first support member may be located at an outer portion of the flexible sealing element. Such an arrangement assists in recovery of the flexible sealing element from the expanded position to the run in position, when source of pressure is reduced or eliminated.
In certain embodiments of the invention, the first support member may also be urged outwardly against the bore wall, in use, to help to create the seal.
In at least one embodiment of the present invention the spring is a helical spring.
In other embodiments the spring may be a garter spring.
In some embodiments the spring may comprise a first spring with a second spring in its interior. The second spring may be mounted within the first spring such that the helix of one spring is wound in the opposite direction to the spiral of the other spring in order to resist canting of the first support member under high pressure. In some embodiments this arrangement of the springs also confers benefits for reducing the extrusion of the second support member into the first support member.
Alternative spring forms and/or arrangements may be used without departing from the principles of the invention.
The first support member may alternatively or additionally comprise a petal arrangement.
The petals may be overlapping. In moving from the run-in position to the expanded position, the petals open up but still form a continuous surface to resist extrusion of the flexible seal element along the bore wall away from the source of pressure.
The first support member may be located so as to abut the second support member. Such an arrangement restricts movement of the first support member to some degree when the device is pressurised, and may be used to direct movement of the first support member to improve formation of a seal.
The pressure control device may comprise a rigid body adapted for mounting on a mandrel or the like.
The rigid body may comprise an annular member.
The first support member may be mounted to the annular member.
The rigid body may comprise a cammed surface adapted to be engaged by the first support member.
The cammed surface may be arranged to direct the first support member radially outward when the device is under pressure. This may be achieved by the cammed surface being inclined axially downwardly from the centre of the device and radially outward. Such an arrangement also provides further integrity of sealing by ensuring the first support member has to overcome both the pressure within the pressure control device and the direction of the cammed surface to return to the run-in position.
Alternatively, the cammed surface may be inclined upwardly, or may be generally horizontal; these arrangements may be used to delay or restrain expansion of the first support member and/or flexible sealing element, which may be useful in certain applications.
The first support member may be bonded to the second support member.
In alternative embodiments the first support member may be located on or adjacent the second support member.
In at least one embodiment of the present invention the second support member comprises a composite of greater hardness than the flexible sealing element located at an outer portion of the flexible sealing element. When the composite portion is of greater hardness than the flexible sealing element itself, it will be less susceptible to flow or extrusion due to the pressure, so improving effectiveness of the device. This feature also allows the flexible sealing element to be made of somewhat thinner or less hard material than in previous devices.
The composite of the second support member may comprise a composite matrix and a reinforcing material.
The reinforcing material may be more rigid than the composite matrix material. In at least one embodiment of the present invention the reinforcing material adds rigidity to the second support member and improves its anti-extrusion properties at high pressures. This is of benefit because when in use, it will resist extrusion into the first support member and therefore it will not hamper the recovery of the cup or packer original size and shape upon removal or reduction of deforming pressure.
In at least one embodiment of the present invention the reinforcing material may comprise a plurality of separate members, particles or fibres.
In other embodiments the reinforcing material may comprise at least one aggregated member. In at least one embodiment of the present invention one or more aggregated members provide(s) enhanced anti-extrusion properties to the second support member and also helps resist better the extrusion of the flexible sealing element by providing better tensile strength.
The/each aggregated member may comprise a mesh.
The mesh may comprise metal wire. Other semi-rigid materials may be used for the mesh without departing from the principles of the invention. Metal wire meshes are easily available at affordable prices and provide the required mechanical and anti-extrusion properties to the second support member in conjunction with the composite matrix.
The mesh may be a diamond shape mesh.
Alternatively, the mesh may be a chicken-wire style mesh (hexagonal mesh).
Other mesh shapes may be used without departing from the principles of the present invention.
In some embodiments the second support member may also be urged outwardly against the bore wall, in use, to help create a seal.
Suitable materials for the various components include, but are not limited to elastomers such as nitrile, hydrogenated nitrile, fluoroelastomers, perfluoroelastomers, thermoplastic materials, EPDM, polyurethane, and the like for the flexible sealing element and/or the composite matrix; metals such as steel, brass, or the like, or polymeric materials such as PEEK, nylon, Kevlar and/or metal fabrics or the like for the first support member and/or the composite reinforcing material.
The second support member may be located adjacent the first support member at an outer portion of the flexible sealing element.
At least a portion of the second support member may extend radially inwards of the first support member.
The second support member may comprise a free end which is not bonded to the flexible sealing element.
The second support member may comprise a free end and a bonded end, which is bonded to the flexible sealing element. The free end allows movement and expansion of the flexible sealing element relative to the second support member, while the bonded end serves to both retain the second support member in place relative to the flexible sealing element, and further reduces the risk of flow and/or extrusion of the flexible sealing element.
The first support member may be located adjacent to the free end of the second support member. In at least one embodiment of the present invention this arrangement allows the combination of the first support member and the second support member to move relative to the flexible sealing element when under pressure.
Preferably, the flexible sealing element is selectively bonded to the body of the first and/or second support member.
A portion of the flexible sealing element may be bonded to a portion of the first support member and a further portion of the flexible sealing element may be bonded to a portion of the second support member.
Any suitable means may be used to bond the components of the device; for example, glue or other adhesive, welding, vulcanisation, heat treatment, mechanical fasteners, bonding agents, and the like.
An embodiment of the present invention will now be described with reference to the accompanying drawings in which:
Reference is first made to
The pressure control device 10 further comprises two first support members 30, 32 and two second support members 34, 36. The structure and operation of the first and second support members 30, 32, 34, 36 will be discussed in due course.
The pressure control device 10 further comprises an upper setting disc 38 and a lower setting disc 40, the discs 38, 40 being adapted to be moved towards each other and move the sealing element portions 20, 22, 24 from the run-in configuration shown in
Referring to
The first support member 32 comprises a circular helical spring 42. The helical spring 42 rests on a cammed surface 44 defined by the lower setting disc 40 and is embedded in the matrix 46 of a composite material 48 which makes up the second support member 36.
The matrix 46 of the composite material 48 is an elastomer such as nitrile butadiene rubber and is reinforced by a deformable reinforcing element 50.
As can be seen from
During manufacture of the second support member 36 the matrix material 46 is adapted to permeate into the reinforcing element voids 54 as the reinforcing element 50 is embedded in the second support member 36 as the second support member 36 is pressure formed around the reinforcing element 50.
The pressure control device 10 is moved from the run-in configuration to the set configuration by applying a force to the setting discs 38, 40 to move the setting discs towards each other, compressing the flexible sealing elements 20, 22, 24. Due to the presence of the mandrel 14, the sealing elements 20, 22, 24 can only expand radially outwardly and expand into engagement with a wellbore wall 56 (best seen in
In the set configuration, the flexible sealing portions 20, 22, 24 are engaged with the wellbore wall 56 and under pressure and temperature in the wellbore 16 would be inclined to extrude into the gap indicated by the letter “A” on
As can be seen from
Continuing to refer to
As previously stated, the first support member 32 is in the form of a helical spring 42. The spring 42 is biased to the run-in position and is in an expanded state in the set position. In the set position adjacent coils will, therefore, be separated with a gap between. The use of a harder elastomer for the matrix 46 of the second support member 36 and the presence of the reinforcing element 50 reduces seepage of the second support member 36 into the gaps between the separated coils. This allows the first support member 32 to recover to the run-in configuration when the setting pressure is removed.
Various modifications and improvements may be made to the above-described embodiments without departing from the scope of the invention. For example, in low-temperature environments, a mechanical force could be applied to move the seal element to the sealed position.
Although the support element is shown as being a conical multilayer mesh construction, other materials such as Kevlar could be used and other shapes such a cylindrical can be adopted.
Similarly, although the embodiments shown a packer type pressure control device, a further embodiment comprising a pressure control device comprising a flexible cup would also fall within the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1510285.8 | Jun 2015 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2016/051715 | 6/10/2016 | WO | 00 |
