GB2225601A - A liner hanger - Google Patents

Abstract

A device for positioning and hanging a liner beneath a larger diameter casing in a well bore comprises a top sub (14) having a lower tapered wall section (27), a ported mandrel (15) below the top sub (14) and the hydraulic chamber (21) containing a piston (22) which carries a series of slips (24). When hydraulic pressure within the mandrel (15) causes piston (22) to rise, slips (24) are forced upwardly along tapered wall section (27) to grip the inside wall of casing (11). The device is compact and is simple and inexpensive to install. <IMAGE>

Description

A LINER HANGER THIS INVENTION relates to a device for positioning and hanging a liner beneath a larger diameter casing in a well bore.

In the extraction of subterranean oil and gas a well bore drilled from the earth's surface to a position at which the oil or gas is accessible, must be lined for the passage of a drill string and for the controlled ducting of liquids or gases. In deep wells it is usual for the upper regions of the well bore to contain a large diameter casing below which is suspended a smaller diameter liner extending to the required depth. To suspend a liner from an existing casing, there is the need for an expendible device which may carry the liner down through the casing and attached it rigidly thereto.

This invention is particularly concerned with hydraulically set liner hangers into which a fluid substance is pumped under pressure to cause a plurality of external slips to move outwardly to grip the inner wall of the casing. Once set the liner hanger is usually cemented in place by pumping a settable material down and outwardly around a liner hanger to fill and set within the surrounding space inside the casing. Thus a rigid fixture is created below which the well bore liner is situated.

Hydraulically set hangers are known but they are of considerable length and are of complex construction.

Therefore the risk of failure is high as is the cost of manufacture and transportation.

An object of the present invention is to provide a hydraulically set liner hanger of simple and compact design providing adequate support for a well bore liner.

According to the present invention, there is provided a device for positioning and hanging a liner beneath a larger diameter casing in a well bore, comprising a top sub having a lower tapered wall section of frustoconical form, a ported mandrel below the top sub, an hydraulic chamber external to the ported mandrel, a piston within the chamber, at least one slip bar connected to the piston and having an outer toothed surface to grip the inner surface of a surrounding casing, and means at the lower end of the mandrel for attachment and suspension of the liner.

Embodiments of the invention will now be described, by way of examples only, with reference to the accompanying drawings, in which: Fig. 1 is a partly cross sectional vertical elevation of a liner hanger made in accordance with the invention; Fig. 2 illustrates such a device installed within a well bore; and Fig. 3 is a part cross sectional vertical elevation of a two-part device made in accordance with the invention.

Referring initially to Figs. 1 and 2, in a well bore 10 below an existing cylindrical casing 11 therein, there is suspended a tubular liner 12. A liner hanger generally indicated at 13 and made in accordance with the invention is incorporated to suspend the liner 12 beneath the casing 11 in the bore 10.

In vertical succession, the liner hanger 13 comprises a top sub 14, a ported mandrel 15 threadedly connected internally at 16 to the top sub 14, and an extension tube 17 connected to the bottom of mandrel 15 by means of a threaded collar 18 having around its external surface centralising lugs 19.

The outer surface of top sub 14 also carries circumferentially spaced centralising lugs 20.

Around ported mandrel 15 is a hydraulic chamber 21 in which is located an annular piston 22.

Circumferentially spaced ports 23 serve as communication between the interior of mandrel 15 and that of hydraulic chamber 21 below piston 22.

Attached to the upper region of piston 22 are a plurality of circumferentially spaced slips 24 which are formed with teeth 25 on their outer surfaces and are attached to the piston 23 by welded slip bars 26.

The outer surface of top sub 14 in its lower region is tapered in frusto-conical form as illustrated at 27. The inner surfaces of the slips 24 are adapted to slide upwardly along the tapered surface 27 during the setting process to be described.

The liner 12 is threadedly connected to the bottom end of extension tube 17 by means of threaded collar 18.

The inner diameters of the components of the device are equal to provide a smooth cylindrical surface.

In the upper region of top sub 14 there is an internal square section release thread 29 for the temporary attachment of a setting tool.

The remainder of the bore of top sub 14 has a polished surface, and there is a short external thread 30 at the upper extremity of the top sub.

Hydraulic chamber 21 and piston 22 are temporarily connected together by a series of brass shear pins 31 at spaced positions around the circumference.

In use, the components of the system are installed as illustrated in Fig. 2, a setting tool (not shown) being inserted into the liner hanger and secured by thread 29.

The setting tool includes means for supplying pressurised fluid within the bore of the liner hanger which passes through ports 23 into chamber 21 thus causing piston 22 to rise which in turn forces slips 24 upwardly and outwardly along conical surface 27 to grip the internal wall surface of the casing 11.

Subsequently, after removal of the setting tool a settable material such as cement is passed downwardly through the bore and outwardly around the liner and the liner hanger to form a rigid and permanent fixture thereof in the well bore.

Referring now to Fig. 3 there is illustrated a modified form of liner hanger in accordance with the invention. In this case, in addition to slips 24 at spaced circumferential positions around the device piston 22 also carries a further series of slips 40 at a different level.

Extension bars 41 carrying the additional slips 40 are housed within grooves 42 in the conical surface 43 upon which the slips 24 slide. A further conical surface 44 is formed on a modified top sub 45.

In this embodiment pressurised fluid causes simultaneous extension of slips 24 and 40 to provide a dual grip at different levels upon the internal wall surface of the existing casing.

Also illustrated in Fig. 3 is a tie-back extension 46 which is threadedly attached at 30.

As can be seen from the drawings, the slips 24 are partially covered by the hydraulic chamber 21 and are connected to the piston 22 by the welded slip bars forming a rigid and positive connection. The outer extremity of the slips before setting is within the diameter bound by the centralising lugs 19 and 20 thus avoiding the risk of the slips becoming prematurely pulled out or damaged during sinking of the device into the well bore.

Temporary attachment of the piston 22 to the hydraulic chamber 21 by shear pins- 31 ensures that a predetermined internal pressure must be achieved before the piston and slips may be moved. The setting pressure can be controlled by varying the size and/or quantity of the brass shear pins 31.

The liner/hanger assembly can be reciprocated within the well bore before setting to aid in cleaning the bore with circulating fluid provided that the fluid pressure does not exceed the setting pressure of the hanger.

In the event that the liner should become stuck in the well it will still be possible to set the liner hanger so that the liner may be held in tension and not fall to the bottom of the well after the setting tool has been released.

A hanger made in accordance with the invention is compact in design, there being only one threaded connection between the hydraulic chamber and the seals on the setting tool on the polished bore of the top sub.

The risk of leaks developing in the critical area are minimised, particularly since the hangers are pressure tested before use.

Again, a hanger made in accordance with the invention has a load carrying capacity in excess of the burst strength of the casing in which it is set. This is ensured since the circumferential extent of the slips is greater than 60 per cent of the conical surface of the top sub, the cone itself having an uninterrupted circumference both internally and externally, a feature of considerable value when compared with existing liner hangers incorporating narrow ramp surfaces welded onto an otherwise cylindrical outer surface. The polished bore within top sub 14 permits the use of high pressure packing on the setting tool which is designed to maintain pressure from above and below the liner hanger. The releasing thread 29 comprises a single start, four pitch, buttress type of parallel thread capable of supporting the weight of more liner than the casing itself would support.

The internal diameter of the hanger is at least as great throughout as that of the liner below thus ensuring ease of movement of the drill string during the subsequent drilling processes.

Claims (15)

1. A device for positioning and hanging a liner beneath a larger diameter casing in a well bore, comprising a top sub having a lower tapered wall section of frustoconical form, a ported mandrel below the top sub, an hydraulic chamber external to the ported mandrel, a piston within the chamber, at least one slip connected to the piston and having an outer toothed surface to grip the inner surface of a surrounding casing, and means at the lower end of the mandrel for attachment and suspension of a liner.

2. A device according to Claim 1, wherein the top sub has a polished bore.

3. A device according to Claim 1 or Claim 2, wherein said top sub has an internal square sectioned releasing thread for attachment of a setting tool.

4. A device according to any preceding claim, wherein said top sub has at its upper end an external thread for attachment of a tie back extension.

5. A device according to any preceding claim, wherein the lower tapered wall of the top sub presents a continuous uninterrupted frusto-conical surface around its circumference.

6. A device according to any preceding claim in which the hydraulic chamber and the piston therewithin are temporarily connected by one or more shear pins adapted to shear at the required hydraulic setting pressure.

7. A device according to any preceding claim, including four slips directly connected to the piston by slip bars and partially covered by the hydraulic chamber.

8. A device according to any preceding claim, including an extension tube connected to the bottom of the ported mandrel by a threaded collar, the outer surface of which carries a plurality of circumferentially spaced centralising lugs.

9. A device according to any preceding claim, wherein the outer surface of the top sub carries a plurality of circumferentially spaced centralising lugs.

10. A device according to any preceding claim, in which there is a single threaded connection between the hyraulic chamber and a polished bore of the top sub within which a setting tool is to be located.

11. A device according to any preceding claim, wherein the circumferential extent of a plurality of slips occupies at least 60 per cent of the circumference of the tapered wall section of the top sub.

12. A device according -to any preceding claim, wherein the lower tapered wall section of the top sub is integral with the remainder thereof.

13. A device according to any preceding claim, in which the top sub and at least the ported mandrel are made from 4140, 4145HT, N-80 or P110 grade steel.

14. A device according to any preceding claim, including at least one further slip located in a position vertically spaced from said at least one slip and cooperating with a further tapered wall section of frustoconical form such that upon upwards movement of the piston within the chamber, the casing is gripped simultaneously by at least two slips at different levels therein.

15. A device for positioning and hanging a liner beneath a larger diameter casing in a well bore, substantially as hereinbefore described with reference to and as illustrated in Figs. 1 and 2 or Fig. 3 of the accompanying drawings.