RU2398953C1 - Packing element of wellhead - Google Patents

Abstract

FIELD: gas-and-oil industry.

SUBSTANCE: invention refers to cylinder case with central through channel wherein there are installed packing element out of elastic material and hydraulic compensator. The packing element is composed with two circular cylinder components - an external and replaceable internal one arranged coaxially. Also the replaceable component interacts with a centraliser and a cover pressure tight closing the cavity of the case. The hydraulic compensator consists of a working chamber in form of a circular cavity positioned outside the packing element and filled with working fluid; the cavity is communicated with an external source of hydraulic feed via the channel; further, the compensator consists of a cavity hydraulically connected with the wellhead and of a divider between the working chamber and this cavity. The divider corresponds to a cylinder shell out of elastic material with restricting rings out of rigid material outside. Pressure in the working chamber can be controlled due to improved system of hydraulic channels facilitating continuous pressure tightness at the wellhead; the divider compensates excessive loads on internal packing component through which a coupling passes.

EFFECT: increased reliable pressure tightness and wear resistance of disclosed facility.

3 dwg

Description

The invention relates to the oil industry, in particular to equipment for sealing the mouth during operations associated with the rotation or hoisting operations of the pipe string.

The well-known "Wellhead sealing head" (RF Patent RU No. 2068488, IPC ⁶ E21B 33/06), including

- housing with a central through channel for passing pipes with technological equipment,

- an elastic sealing element mounted on the upper and lower ring bushings mounted in the housing with the possibility of rotation, and forming with the latter a hydraulic working chamber;

- an annular piston mounted on the upper sleeve and forming with the upper part of the housing a hydraulic chamber for returning the elastic sealing element to its original state;

- moreover, on the inner surface of the elastic sealing element made labyrinth grooves,

- and the lower ring sleeve is provided with a thrust ball bearing of rotation.

A disadvantage of the known device is the increased complexity of repair and maintenance, due to the fact that to replace the sealing element when it is worn out, it is necessary to completely dismantle the device from the mouth and drain the working agent from both hydraulic working chambers. In addition, for the operation of the device, an additional energy source is needed in the form of a pumping unit or a pneumatic accumulator, which also increases the cost of its operation.

Known wellhead sealant (PM No. 46295, E21B 33/03), including

- a cylindrical body with a central through channel for passage of a string of pipes connected by couplings;

- in which the sealing element is made of elastic material, made in the form of two cylindrical elements located coaxially with the outer and interchangeable inner;

- a working chamber in the form of an annular cavity between the housing and the sealing element, filled with a working agent;

- a pressure limiter during the passage of the pipe string couplings through a sealing element containing a separator between the working chamber and the wellhead, made in the form of a hydraulic cylinder with a spring-loaded piston dividing the hydraulic cylinder into two cavities, the hydraulic cylinder cavity in which the spring is located is hydraulically connected to the wellhead, and the other cavity is connected by a hydraulic channel to the annular cavity;

- and a hydraulic power source, made in the form of a hydraulic cylinder with a manual drive, the rod cavity of which is hydraulically connected to the wellhead, and the piston cavity is connected by a hydraulic channel to the annular cavity.

A disadvantage of the known device is the low reliability of operation, due to the fact that the working chamber, together with a hydraulic power source and a pressure limiter, being a hydraulically closed system, has a well-defined irreplaceable volume of the working agent. Therefore, the leakage of the latter due to loss of tightness in this closed system can lead to the device not fulfilling its functional purpose, because a situation is possible when even the maximum movement of the piston of a hydraulic cylinder with a manual drive cannot compensate for the loss of the volume of the working agent, in connection with which it is necessary to interrupt the process of the device and to refuel the working chamber with the working agent to the required volume.

The decrease in the reliability of the known device at low temperatures can also be associated with a change in the phase state (turning into ice) of the flushing fluid located in the hydraulic channels and cavities connecting the supply hydraulic cylinder and pressure limiter to the wellhead, which will lead to the impossibility of deformation of the sealing element and to its possible destruction during the passage of the coupling.

The technical task of the invention is to increase the reliability of the well-known wellhead sealant.

To achieve this result in a well-known sealant wellhead, including

- a cylindrical body with a central through channel for passage of a pipe string connected by couplings;

- in which the sealing element is made of elastic material, made in the form of two annular cylindrical elements located coaxially with the outer and interchangeable inner;

- a lid and a centralizer, hermetically closing the body cavity and interacting with the sealing element;

- a hydraulic compensator containing a working chamber in the form of an annular cavity located outside the sealing element, filled with a working agent and connected by a channel to an external hydraulic power source,

- a cavity hydraulically connected to the wellhead,

- and a separator between the working chamber and this cavity,

ACCORDING TO THE INVENTION

- the separator of the hydraulic compensator is made in the form of a cylindrical shell of elastic material,

- outside of which restrictive rings of rigid material are installed;

- and the cavity of the hydraulic compensator, hydraulically connected to the wellhead, is located inside the body.

The invention is illustrated by drawings, where in Fig.1 shows a General view of the wellhead sealant, in Fig.2 is the same in the pipe passage position, in Fig.3 is the same in the coupling passage position.

The inventive wellhead sealant (hereinafter, the sealant) consists (Fig. 1) of a housing 1 having a passage 2 in the lower part for passing pipes 3 connected by couplings 4. In the housing 1, a sealing element 5 is made of elastic material made in the form of two coaxially arranged annular cylindrical elements - a removable inner element 6 and the outer element 7. For fixing in the housing 1, the inner element 6 is equipped with an upper 8 and lower 9 reinforcing rings of hard material. On top of the housing 1 is hermetically closed by the centralizer 10 and the cover 11, the figured end 12 of which hermetically interacts with the outer element 7. A similar configuration of the end 13, hermetically interacting with the outer element 7, is made in the bottom of the housing 1.

The inventive sealant is equipped with a hydraulic compensator 14 containing a separator 15 made in the form of a cylindrical shell made of elastic material, a cavity 16 located inside the housing 1 outside the separator 15 and hydraulically connected by a channel 17 to the wellhead (not shown), and a working chamber 18 in the form of an annular cavity located outside the sealing element 5, filled with a working agent and connected by a channel 19 to an external hydraulic power source (not shown).

To fix the separator 15 in the lid 11 and the housing 1, figured recesses 20 and 21 are made, and to limit its deformation, restrictive rings 22 made of hard material are installed outside.

The inventive sealant operates as follows (figure 1).

The sealant without a replaceable internal element 6 is mounted on the wellhead (not shown) and downhole equipment (not shown) is made through the passage 2 of the housing 1 (on the pipes 3 connected by couplings 4. After the downhole equipment is lowered into the specified interval, where it is supposed to work with the sealed with the mouth, a replaceable inner element 6 is installed in the sealant 3 corresponding to the diameter of the pipes 3 and fixed with a centralizer 10. Then, from the pump (not shown) through the channel 19, liquid is pumped under pressure into the working chamber EPA 18, as a result of which the sealing element 5 is deformed inward, fitting the pipe 3 and hermetically blocking the wellhead (FIG. 2). At the same time, the separator 15 will also deform outwardly into the cavity 16, but its deformation will be limited due to the use of rings 22 made of hard material. In this case, the inner element 6 will be kept from vertical displacement due to the reinforcing rings 8 and 9, and the outer element 7 and the separator 15 will be fixed thanks to the curly notches 12 and 20 in the cover 11 and the curly notches 13 and 21 in the housing 1.

With increasing pressure in the well, the fluid from the wellhead through the channel 17 will fill the cavity 16, thereby creating a backpressure of the possibility of the breakthrough of the well fluid through the contact zone of the internal element 6 with the pipe 3. This is due to the fact that the pressure from the cavity 16 will be transmitted to the separator 15, made from an elastic material, from it to the working chamber 18 and then to a sealing element 5 made of elastic material. Thus, the pressure at the wellhead acting on the sealing element 5 will be balanced by the same pressure from the side of the cavity 16, and the tightness margin in the contact zone of the internal element 6 with the pipe 3 will be determined by the pressure of the liquid pumped from the outside into the working chamber 18. Thus , compared with the prototype, where the volume of liquid in the working chamber is non-renewable and in case of leaks, depressurization of the mouth may occur, the inventive device has greater reliability due to the fact that the leakage is working of the agent can be replenished by the pump, therefore, the liquid pressure in the working chamber 18 will not decrease, which will ensure the tightness of the mouth.

When passing through the inventive sealing sleeve 4 (figure 3), the diameter of which exceeds the diameter of the pipe 3, the sealing element 5 will expand, which causes the automatic response of the elements included in the hydraulic compensator 14, in the following sequence: due to the elastic expansion of the outer element 7 pressure the liquid in the working chamber 18 will increase, acting on the separator 15, which will also expand, compensating for the increase in pressure in the working chamber 18. Due to this, the specific pressure in the contact of the coupling 4 with the inner element 6 will be constant and, therefore, the passage of the clutch 4 will not intensify the abrasive wear of the inner element 6, which increases its service life. In this case, the deformation of the separator 15 will be limited due to the use of rings 22 of rigid material.

Compared with the prototype, where the cavities communicating with the wellhead are located in the supply hydraulic cylinder and the limiter located outside the housing, and therefore it is possible to freeze the liquid in them at negative temperatures, which will lead to the inability to deform the sealing element and its possible destruction during the passage of the coupling , the inventive sealant has greater reliability. This is because both the cavity 16, communicating with the wellhead, and the channel 17 are located in the inventive sealant in the housing 1, which has a much greater mass and heat capacity in comparison with the supply hydraulic cylinder and the prototype limiter. In addition, the volume of fluid in the cavity 16 and its thermal contact with the housing 1 is also much larger in comparison with the similar parameters of the prototype.

Thus, the total effect of the distinctive features allows to increase the reliability of the inventive sealant in comparison with the prototype.

Claims (1)

The wellhead sealant, including a cylindrical body with a central through passage for passage of a pipe string connected by couplings, in which a sealing element of elastic material is placed, made in the form of two annular cylindrical elements located coaxially: an external and a removable internal one, a lid and a centralizer, hermetically closing the cavity housing and interacting with the sealing element, a hydraulic compensator containing a working chamber in the form of an annular cavity located outside the sealing an element filled with a working agent and connected by a channel to an external hydraulic power source, a cavity hydraulically connected to the wellhead, and a separator between the working chamber and this cavity, characterized in that the hydraulic compensator separator is made in the form of a cylindrical shell made of elastic material, on the outside of which restrictive rings of rigid material, and the cavity of the hydraulic compensator, hydraulically connected to the wellhead, is located inside the body.

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