NO346921B1

NO346921B1 - High pressure cable head connector

Info

Publication number: NO346921B1
Application number: NO20200327A
Authority: NO
Inventors: Sergiu Ariton
Original assignee: Roxar Flow Measurement As
Priority date: 2020-03-19
Filing date: 2020-03-19
Publication date: 2023-02-27
Also published as: WO2021185944A1; NO20200327A1

Description

HIGH PRESSURE CABLE HEAD CONNECTOR

The present invention relates to a high pressure cable head connector with two high pressure metal to metal barriers, acting simultaneously, e.g. for connecting downhole cable with gauge for use in downhole completion.

A cable head is part of the downhole gauge tool used for connecting a downhole cable to a gauge and need to ensure and protect connection of the downhole cable with the gauge with a double metal to metal gas tight pressure barrier.

Known solutions for high pressure environments have included complicated structures with a number of sealing rings. One example of the prior art is presented in figure 1 where two rings 01 are forced in the radial direction when the connector parts 02,03 are pushed in the longitudinal direction. This solution requires that the surface of the cable is smooth in order to give the sealing rings 01 sufficient contact with the cable surface, and the number of parts needed for providing two pressure barriers increases the risk of failure. Examples showing such solutions are well known within the field and may be found in US5823256, US3445128, US3985379 and US3325192.

It is an object of the present invention to provide a relatively inexpensive connector with high pressure integrity, which is easily assembled in offshore applications while reducing the required qualification of the users.

The objects of the invention is thus solved using a high pressure cable head connector as stated above and is characterized as presented in the accompanying claims.

The present invention thus relates to a system of at least one metal to metal compressed seal providing a double sealing barrier for each seal, simultaneously on the outer interface and on the inner interface and particularly to an elastic plastic deformation of a resilient metal bevel seal embedded between a cable head housing and a 1⁄4” downhole tubing encapsulated cable (TEC). According to a preferred embodiment two compressed seals are provided.

The bevel seal according to the invention thus creates a precise contact area based on elastic plastic deformation and compensate rough surface and less precise geometry and dimensions of the parts in contact. It also provides sealing proof capability for extremely high pressure and temperature and independently testable that is not dependent on the surface quality of the parts in contact and sealing barriers that work properly in a very corrosive environment given by well fluid properties.

This provides a double seal interface for sealing against up to 25000 psi well fluid pressure acting outside of downhole tubing encapsulated cable or against up to 25000 psi well fluid pressure acting inside of downhole tubing encapsulated cable of the well fluid in conditions of high temperature exceeding 200 degrees Celsius. This is provided by forcing the sealing ring both outward into the connector housing and inward to the cable surface, the cable surface being made from a metal or another material having similar characteristics. In a preferred embodiment two rings are used for redundancy.

The present invention utilizes ring shaped bevel springs that are compressed to a predetermined deflection, generating a sealing stress by the resilient bevel spring seal shape. This way a compact connector is provided using less parts and thus minimizing the risk of failure, and that is easy to assemble, thus reducing the time to rig a system. The components may be used as is without contact preparations of the cable. Such a solution is described in NO20181235, which was not published at the date of filing, but does not define nature of the bevel ring material necessary to provide a sufficient sealing effect.

The invention will be described more in detail with reference to the accompanying drawings, illustrating the invention by way of examples.

Fig. 1 illustrates the prior art.

Fig. 2 illustrates a longitudinal cross section of the preferred embodiment of the invention.

Fig. 3 illustrates the sealing mechanism of the invention.

Fig. 4 illustrates an alternative embodiment of the invention.

Fig. 5 illustrates another alternative embodiment of the invention.

As is illustrated in figure 2 the sealed connector according to the invention includes a first connector part 1 and a second connector part 5 adapted to be locked or screwed together applying an axial force towards each other. A cable 6, preferably a TEC or other cables with a hard outer surface, extends through the connector.

The shape and deformation of the seals ensure an axial reaction force in any moment bigger than the force from the pressure applied on the exposed surface of the seals. The resulting elastic deformation of the seal creates an elastic strain in the sealing area higher than the yield strength of the parts in contact and will compensate parts in contact thermal expansion. The contact stress will remain unchanged under the pressure applied on the exposed surface of the seal. This way the deformation and strain provides a high pressure seal both outward toward the first connector part and inward toward the cable, thus representing the double seal interface.

Figure 3 illustrates the function of the bevel ring 2. The bevel ring cross section is shown as a rounded essentially rectangular shape in two situations, the uncompressed position 7 and the compressed position 8. Before the compression the bevel ring 2 in the illustrated example 7 has an angle of 45° relative to the longitudinal axis corresponding to both the inner house surface of the first connector part 1 and the outer surface of the cable 6. After being subject to a longitudinal force toward the inner wall 1a of the first connector part by the front end 4 of the second connector part 5 the bevel ring is tilted, e.g. by 5° as illustrated in the compressed position 8, in which case the outer edge 2c of the bevel ring is forced in the radial direction into the inner surface of the first connector part 1 and the inner edge 2d toward the outer surface of the cable 6. This forces a close connection between the surfaces and the bevel ring and thus sealing the connection between the first connector part and the cable.

Thus, when the axial pressure is applied the bevel seals 2 are embedded into a housing 1 and compressed against a cable head housing 6 shoulder, preferably by a metallic threaded locker part until the flat surface of the bevel seals are mating with flat surface from cable head housing respective to the flat surface of the locker part.

As can be seen from the cross section of the bevel ring in figure 3 the rounded rectangular shape is preferably about 2:1 ratio between radial dimension and thickness, and may include a cut off edge 2a toward the front end of the second connector part, having an angle, e.g.25° in the case when the bevel ring is tilted by 45°, from the bevel seal surface. This is to receive the front end 4 of the second connector (not shown in figure 3), and, when a tilt of 5° has been applied the cutoff edge 2a is perpendicular to the longitudinal direction and thus parallel to the front end 4 of the second connector part 5. This will stop the tilting at 5 degrees, before amplitude point of rotation, thus protecting the cable 6 and housing 1. A similar cutoff edge may also be provided on the edge 2b interacting with the inner surface 1a of the first connector part. This will create a controlled contact stress to avoid the TEC to be deformed on the inner wall against cable.

As can be seen from the figure 4 two bevel rings 2 are positioned between the first and second parts in the axial direction providing a redundancy in the seal.

The front end of the second connector part 5 and the inner surface of the first connector part have radially plane section and the bevel rings 2 have a frustoconical shape defining an angle relative to the radial and axial directions. In figure 4 the bevel rings are tilted in opposite directions toward each other with a stopper ring 3 between them. The stopper ring limiting how much the shape of the bevel ring can change then the connector parts are pressed together, limiting the force toward, and deformation of, the outer part of the cable.

Preferably the front end of the second connector part 4 includes a low friction element surface 4a to be able to rotate relative to the bevel ring if screwed into the connector.

The stopper 3 illustrated in figure 4 may have the same function in providing a bed stopping for the tilt at a certain angle where the sealing is obtained without applying more stress or deforming the bevel seal, cable or housing more than an allowed degree.

Bevel seals will have an axial movement and in the same time a rotation with 20 degrees, stopping rotation with 5 degrees before amplitude of the movement between the bevel seal and housing and respective downhole cable. This way a spring back force is obtained as well as protection of the parts.

During the movement and after, a spring back force will exert uniform pressure on the sealing interface and keeps a preset load on the seal with an equal distribution outward to the housing 1 and inward to the cable pipe 6.

Compressed bevel seal system is capable to provide a pressure integrity mechanism which form a pressure seal on a tubular wall both outside and inside thus providing dual sealing. A locking mechanism may be used to avoid relaxing the bevel seals by unscrewing locking part.

The materials used for spring and connector parts will be chosen to provide elastic deformations when subject to a pressure and also maintain the inward and outward force when in place under high pressure and high temperature conditions, so as to maintain the force under varying pressure and temperature and thermal expansion. The elastic properties also makes it possible to compensate for uneven shape of the cable or the cylindrical channel in the first connector part, or a degree of surface roughness. The material for tubing encapsulating the cable may preferably be a nickel alloy 625 or nickel alloy 825 and the bevel seal rings are made from nickel alloy 718.

Figure 5 illustrates an alternative embodiment where two bevel rings 2 are used, also providing a redundancy in the sealing. In these figures the rectangular cross sections show cutoffs on both sides of the bevel rings, both on the inner surface 1a and the front surface 4.

The present invention thus relates to a high pressure cable head connector, e.g. for connecting downhole cable to a measurement device, e.g. a pressure sensor, for use in downhole completion. The sealing cable connection device is made for high pressure applications including a first connector part and a second connector part including an axial channel for allowing a cable to extend. The first connector part 1 having a cylindrical channel with a radially oriented inner surface 1a and the second connector part 5 being adapted to be introduced into said channel and having a corresponding shape in the radial direction, said second connector part having a radially oriented front end surface 4a. The cavity being coaxially oriented around the cable channel 6. The first and second connector parts include locking means being adapted to applying an axial force and lock the parts together after connecting.

The inner volume of said receiving cavity includes at least one bevel ring 2 having radial dimensions corresponding to the radial dimensions of the cavity between the cable and the outer walls of the cavity, the bevel rings preferably having an essentially frustoconical shape in the longitudinal direction. At the application of said axial force the outer parts of said bevel rings are elastically deformed being forced providing an elastic strain into said cavity wall as well as into a cable in said cable channel.

Preferably the cavity walls and bevel ring(s) are made from a metal and the cable is a tubing encapsuled cable with a hard or metal outer surface.

Preferably the material for tubing encapsulate cable is nickel alloy 625 or nickel alloy 825 and the bevel seal rings are made from nickel alloy 718. Other bevel ring shapes may also be contemplated as long as they provide a force in the radial direction when subject to an axial force

The first and second connector parts may be threaded so that the axial force is applied by screwing the parts together. and/or may be provided with other locking mechanisms.

Preferably the bevel rings are constituted by springs exerting high contact stress equal for contact between said outer wall of said cavity and the ring and outer surface of the cable. The bevel rings may be adapted to, when compressed, act like an energized spring who exerts high contact stress equal to compensate thermal expansion of the parts in contact.

The present invention thus provides a first seal barrier for sealing between a connector housing 1 and cable pipe 6 for protecting cable connection against well fluid. Preferably a second seal barrier is used to ensure redundancy of the primary seal. This is obtained using one or more bevel rings 2. Preferably two bevel rings are used being oriented back to back. Thus two bevel rings may provide a double bevel seal technology based on metal to metal sealing for HPHT (High Pressure, High Temperature) environment based on the shape of the seal, preferably being suitable for 25000 psi and 225 C degrees.

As the bevel rings preferably have frustoconical shapes, the at least one bevel rings are rotated around cross intersection of the shape diagonals, as shown and discussed in relation to figure 3 in the controlled manner to ensure maximum contact stress against tubing encapsulate cable and in the same time against outer wall of the cavity when subject to an axial force. The bevel ring or rings are preferably stopped all the time in the same, predetermined position as provided by the cut off edge 2a or by the limiter 3 in figure 2.

Using two bevel rings will have the advantage of providing two sealing barriers in the same time, preferably with the same leak proof capability of under HPHT (High Pressure High Temperature) conditions.

With a double sealing barrier for each seal the elastic stress in the sealing area is preferably higher than the yield strength of the parts in contact. Preferably the elastic of the seals creates an axial force bigger than the force from the pressure applied on the exposed surface of the seals. The contact area between the seals and connected parts has a limitation based on the shape of the seal in the contact area, e.g. by the radius and angle of the seal in the contact area, so that inaccuracies in the shape of the parts are compensated for by the combination of the force between the parts and the shape of the seal edge. This way a double sealing barrier for each seal may be achieved which is not dependent on the surface quality of the parts in contact or dependent on the dimensional and geometrical shape precision of the parts in contact.

Claims

1. Sealing cable connector device for high pressure applications including a first connector part (1) and a second connector part (5) including an axial channel (6) for allowing a cable to extend, the first connector part (1) having a cylindrical channel with a radially oriented inner surface (1a) and the second connector part (5) being adapted to be introduced into said channel and having a corresponding shape in the radial direction, said second connector part (5) having a radially oriented front end surface (4a), the cavity being coaxially oriented around the cable channel (6), the first and second connector parts including locking means being adapted to applying a axial force and lock the parts together after connecting,

wherein at least one elastically deformable bevel ring (2) is positioned at the inner surface (1a) in said cavity having radial dimensions corresponding to the radial dimensions of the cavity between the cable channel (6) and the outer walls of the cavity, and

where at the application of said axial force the outer parts (2c) of said bevel ring(s) (2) is/are elastically deformed in the radial direction thus providing an elastic strain into said cavity wall (1) and into the cable channel (6) the bevel ring (2) thus constituting a bevel seal,

characterised in that each bevel ring (2) is configured to have an elastic strain in the contact area being higher than the yield strength of the first connector part (1) and cable (6) in contact with the bevel ring (2) and thus compensating thermal expansion of the parts in contact.

2. Cable connector according to claim 1, wherein the cavity walls (1,6) and bevel rings (2) are made from a metal.

3. Cable connector according to claim 1, wherein the first and second parts (1,5) are threaded, the axial force being applied by screwing the parts together.

4. Cable connector according to claim 1, including two bevel rings (2), the bevel rings being positioned so as to have their radially outer parts (2b,2c) extending from each other.

5. Cable connector according to claim 4, wherein the bevel rings (2) are constituted by springs exerting high contact stress equal for contact between said outer wall (1) of said cavity and the ring and outer surface of the cable.

6. Cable connector according to claim 1, wherein the bevel ring(s) (2) is/are adapted to, when compressed, act like an energized spring exerting high contact stress to compensate thermal expansion of the parts (1,6).

7. Cable connector according to claim 1, wherein the outer surface of said cable (6) is made in metal.

8. Cable connector according to claim 7, wherein the material for tubing encapsulate cable (6) is nickel alloy 625 or nickel alloy 825 and the bevel seal ring(s) are made from nickel alloy 718.

9. Cable connector according to claim 1, wherein said at least one bevel ring (2) has an essentially frustoconical shape.

10. Cable connector according with claim 9, wherein said at least one bevel ring (2) is rotated around cross intersection of the shape diagonals in the controlled manner at the application of an axial force so as to ensure maximum contact stress against tubing encapsulate cable and in the same time against outer wall of the cavity.

11. Cable connector according with claim 10, wherein each of said at least one bevel rings (2) is stopped at a predetermined position.

12. Cable connector according with claim 1, including two bevel rings providing double sealing barriers for each seal, simultaneously on the outer interface (2c) and the inner interface (2d).

13. Cable connector according with claim 1, including two bevel rings (2) providing two sealing barriers with the same leak proof capability in the HPHT conditions.

14. Cable connector according with claim 1 or 4 where contact area (2a,2b,2c,2d) between the seals and connected parts (1,1a,4a,6) has a limitation based on the shape of the seal in the contact area.

15. Cable connector according with claim 1 or 4 where the elastic of the seals creates an axial force bigger than the force from the pressure applied on the exposed surface of the seals.