RU2731483C1 - Metal sealing assembly for sealing annular space in well - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: invention relates to metal sealing assembly for sealing annular space in well. Metal sealing assembly for sealing annular space in the well comprises a metal sealing element which is made in the form of a hollow cylinder and consists of a base; inner tubular part and outer annular edge, case inducing, sealing ledges on sealing element, sealing surface of housing of casing string suspension is in form of truncated cone diverging to bottom of well, fixing ring. Metal sealing element and inducing housing includes upper and lower sections. Upper part of inner surface of annular edge of sealing element is made in form of combination of two truncated cones. Upper part of one cone is narrowed to the top of the well, the lower part of the other cone expands to the top of the well. Solution angle is selected within range of 0–10°. Upper part of the outer surface of the inducing housing is made in the form of a combination of two truncated cones, the upper and lower parts of which narrow to the bottom of the well. Upper cone solution angle is selected within 0–10°. Radius of circle, along which mating the upper and lower parts of surface of pressing housing, is equal to radius of cylinder formed by upper part of inner surface of outer edge of metal sealing element at stage of pre-sealing.

EFFECT: technical result is higher reliability of sealing of annular space.

1 cl, 5 dwg

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a device used in the operation of offshore and onshore wells, in particular to the design of an annular seal designed to seal the annular space between the casing suspension body and the casing head body of the conductor string. The proposed metal sealing unit can be widely used in the construction of both offshore and onshore wells in the chemical, oil, energy and other industries.

LEVEL OF TECHNOLOGY

To seal the annular space between the casing hanger body and the casing head body, seals of various types are used to prevent or reduce liquid or gas leakage through gaps between parts.

In the text of the present description, the initial state refers to the state of the metal seal assembly from the completion of the run into the annular space to the application of axial force during installation.

Pre-sealing is the process of installing a metal seal assembly that applies a force to the weight of the drill string. In this case, a contact pressure arises between the sealing element and the corresponding sealing surfaces of the casing head of the casing string and the casing of the casing string, sufficient for the hydraulic system of the tool for installing the seal to operate.

Activation is the process of transition of a metal seal assembly under the action of the tool force into a state in which a design contact pressure is created between the sealing element and the counter sealing surfaces of the casing head body of the conductor string and the casing hanger body. In this case, a rigid fixation of the metal sealing unit between the corresponding bodies must be ensured.

Known annular metal-to-metal seal for a system of subsea casing heads, selected as a prototype (US 5174376, published on December 29, 1992), including a metal sealing element, an indentation body, sealing protrusions of a sealing element, a sealing surface of a casing suspension housing having the shape of a truncated cone expanding to the bottom of the well.

The disadvantages of the technical solution are:

- for preliminary sealing with a large radial clearance between the metal sealing element and the sealing surface of the casing of the casing string head, a force is required that can exceed the weight force of the drill string;

- during the activation stage, excessive plastic deformation of the upper sealing lip of the sealing element occurs, which can lead to the destruction of this lip.

DISCLOSURE OF THE INVENTION

The technical result of the invention is to increase the reliability of sealing the annular space while ensuring, by means of a large radial clearance, protection of the sealing surface of the conductor string from contamination and mechanical damage during the installation of elements of the system of subsea column heads due to the reduced pre-sealing force and the absence of excessive deformation of the upper outer sealing lip of the sealing element ...

The technical result is achieved as follows. The metal seal assembly for sealing the annular space in the well includes:

a metal sealing element made in the form of a hollow cylinder and consisting of a base; inner tubular part and outer annular edge,

pressing body,

sealing lips on the sealing element,

the sealing surface of the casing hanger body has the shape of a truncated cone expanding towards the bottom of the well,

fixing ring,

according to the invention,

metal sealing element and pressing body include upper and lower sections,

the upper part of the inner surface of the annular edge of the sealing element is made in the form of a combination of two truncated cones,

the top of one cone tapers towards the top of the well,

the bottom of the other cone expands towards the top of the well,

in this case, the opening angle a is selected in the range 0 ° -10 °,

the upper part of the outer surface of the pressing body is made in the form of a combination of two truncated cones, the upper and lower parts of which taper towards the bottom of the well,

in this case, the opening angle β of the upper cone is selected in the range 0 ° -10 °,

the radius of the circle R, along which the upper and lower parts of the surface of the pressing body are mated, is equal to the radius of the cylinder formed by the upper part of the inner surface of the outer edge of the metal sealing element at the stage of preliminary sealing.

The length of the generatrix of the conical surface of the upper part of the inner surface of the annular edge of the metal sealing element is between the values of the distance from the upper end of the annular edge of the metal sealing element to the upper and lower outer sealing protrusions of the sealing element, respectively.

The retaining ring provides a mechanical connection between the metal sealing element and the pressing body.

The essence of the invention is illustrated by drawings, where:

in fig. 1 is a general view of a metal sealing unit for sealing the annular space in the well in the initial state (section);

in fig. 2 - shows a metal seal assembly for sealing the annular space in the well in a pre-activated state (section);

in fig. 3 - shows a metal seal assembly for sealing the annular space in the well in the activated state (section);

in fig. 4 - the sealing element is shown (section);

in fig. 5 - shows the lower part of the pressing body;

The drawings have the following designations:

1 - casing of the column head of the conductor column;

2 - metal sealing element;

3 - pressing body;

4 - casing suspension body;

5 - sealing surface of the casing suspension body;

6 - support shoulder of the casing suspension body;

7 - upper outer sealing lip of the sealing element;

8 - lower outer sealing lip of the sealing element;

9 - internal sealing protrusions of the sealing element;

10 - annular edge of the sealing element;

11 - upper part of the inner surface of the annular edge of the sealing element;

12 - the lower part of the inner surface of the annular edge of the sealing element;

13 - upper part of the outer surface of the pressing body;

14 - the lower part of the outer surface of the pressing body;

15 - fixing ring.

CARRYING OUT THE INVENTION

The metal seal assembly for sealing the annular space in the well includes:

metal sealing element 2, made in the form of a hollow cylinder and consisting of a base, an inner tubular part and an outer annular edge,

pressing body 3,

sealing lips on the sealing element,

the sealing surface 5 of the casing hanger body has the shape of a truncated cone expanding towards the bottom of the well,

fixing ring.

The metal sealing element 2 includes an upper 11 and a lower 12 portions.

Pressing body 3 includes upper 13 and lower 14 sections.

The upper part of the inner surface 11 of the annular edge of the sealing element is made in the form of a combination of two truncated cones,

the top of one cone 11 tapers towards the top of the well,

the lower part of the other cone 12 expands towards the top of the well,

in this case, the opening angle α is selected in the range 0 ° -10 °,

the upper part of the outer surface 13 of the pressure body is made in the form of a combination of two truncated cones, the upper 13 and lower 14 parts of which taper towards the bottom of the well,

in this case, the opening angle β of the upper cone is selected in the range 0 ° -10 °,

the radius of the circle R (Fig. 5), along which the upper and lower parts of the surface of the pressing body are mated, is equal to the radius of the cylinder (not shown in the figures) formed by the upper part of the inner surface of the outer annular edge 10 of the metal sealing element at the stage of preliminary sealing.

The length of the generatrix of the conical surface of the upper part of the inner surface 11 of the annular edge of the metal sealing element is between the values of the distance from the upper end of the annular edge 10 of the metal sealing element to the upper and lower outer sealing protrusions 7 of the sealing element, respectively.

The fixing ring 15 provides a mechanical connection between the metal sealing element 2 and the pressing body 3.

The installation of the metal seal assembly is carried out as follows. The metal seal assembly is lowered into a subsea well (Fig. 1). An axial load is applied to the pressing body 3.

At the stage of preliminary sealing (Fig. 2), the axial load is provided by the weight of the drill string, and at the stage of activation of the installation, it is created by the tool for installing the seal.

When the body of pressing 3 is introduced into the sealing element 2, its annular edge 10 is bent towards the body 1 of the column head of the conductor column.

Also, under the influence of the axial load, the sealing element 2 is pressed into the conical surface 5 of the casing suspension body.

At a certain value of the axial force (pre-sealing force), contact occurs between the upper outer sealing lip 7 of the sealing element and the surface of the casing 1 of the casing string head, and one or more sealing inner lips 9 of the sealing element and the conical surface 5 of the casing suspension body.

In this case, a preliminary sealing of the annular space occurs, which makes it possible to create hydraulic pressure in the space above the metal sealing unit, which is necessary for the operation of the tool during its installation.

Further, under the action of the axial force created by the tool, the pressing body 3 is introduced into the metal sealing element 2 and the metal sealing element 2 moves until it contacts the support shoulder 6 of the casing suspension body, which limits the axial movement of the metal sealing element 2. During this movement between the inner sealing lips 9 of the metal sealing element and the sealing surfaces of the casing 1 of the casing string head and the casing suspension casing 4, the design contact pressure is achieved and then the metal sealing assembly is fixed in the casing 1 of the casing string head and the casing 4 of the casing string using retaining ring 15. From this moment, the seal is considered activated (Fig. 3).

The fixing ring 15 in the annular space is similar to the prototype device (US patent 005174376).

The technical result is provided by the fact that in the process of preliminary sealing of the seal and the resulting deformation of the annular edge 10 of the sealing element, the area of force transfer from the pressing body 3 to the sealing element 2 (the contact area of the seal housing 3 and the sealing element 2) is retained in the upper part of the annular edge 10 sealing element due to the fact that the upper part of the inner surface of the annular edge 11 of the sealing element narrows towards the top of the well (has a "reverse slope") and by appropriately choosing the angle of inclination and length of this section depending on the value of the radial clearance between the sealing element 2 and the body 1 column head of conductor column. This slope is maintained until the pre-sealing stage is completed.

The transfer of force from the body of the pressing 3 to the annular edge 10 of the sealing element in its upper part provides the maximum possible shoulder of the force that creates a bending moment at the base of the annular edge 10 of the sealing element. This ensures a decrease in the pre-activation force in comparison with the prototype, since in its design the contact area of the casing of the pressing 3 and the annular edge 10 of the sealing element is displaced to the bottom of the well when the annular edge 10 of the sealing element is bent during the installation of the metal sealing unit.

After the preliminary sealing step, the contacting surfaces, namely the upper part of the outer surface 13 of the seal housing and the upper part of the inner surface of the annular edge 11 of the sealing element, become substantially parallel. During activation, when the body of the pressing 3 moves in the metal sealing element 2, no excessive deformation of the upper outer sealing lip 7 of the sealing element occurs.

Thus, the proposed metal sealing unit for sealing the annular space in the well improves the reliability of sealing the annular space in the presence of a large radial clearance between the metal packing unit and the casing of the casing string head, due to the reduced pre-sealing force and the absence of excessive deformation of the upper external sealing lip of the sealing element.

Modifications and improvements to the above described embodiments will be apparent to those skilled in the art. The above description is provided by way of example only and is not limiting.

Claims (16)

1. A metal seal assembly for sealing the annular space in the well, containing a metal sealing element made in the form of a hollow cylinder and consisting of a base; inner tubular part and outer annular edge, pressing body, sealing lips on the sealing element, the sealing surface of the casing hanger body has the shape of a truncated cone expanding towards the bottom of the well, fixing ring, characterized in that metal sealing element and pressing body include upper and lower sections, the upper part of the inner surface of the annular edge of the sealing element is made in the form of a combination of two truncated cones, the top of one cone tapers towards the top of the well, the bottom of the other cone expands towards the top of the well, in this case, the opening angle α is selected in the range 0 ° -10 °, the upper part of the outer surface of the pressing body is made in the form of a combination of two truncated cones, the upper and lower parts of which taper towards the bottom of the well, in this case, the opening angle β of the upper cone is selected in the range 0 ° -10 °, the radius of the circle along which the upper and lower parts of the surface of the pressing body are mated is equal to the radius of the cylinder formed by the upper part of the inner surface of the outer edge 10 of the metal sealing element at the stage of preliminary sealing. 2. A metal sealing unit according to claim 1, characterized in that the length of the generatrix of the conical surface of the upper part of the inner surface of the annular edge of the metal sealing element is between the values of the distance from the upper end of the annular edge of the metal sealing element to the upper and lower external sealing protrusions of the sealing element, respectively ...

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