GB2298880A - Plug valve assembly - Google Patents

Abstract

A plug valve assembly comprises a housing having a main body part 1 and an upper part 3, and on which there is mounted externally a longitudinally displaceable valve sleeve 8 which can cover, and uncover flow ports providing communication between the interior of the tool and the exterior of the housing. A stepped diameter rod 6 and rod extension 4 are mounted internally of the housing and can be reciprocated by applying pressure cycles from above the assembly. This causes a ratchet mechanism 5 to move upwardly which eventually uncovers locking keys 9 allowing them to move inwardly and thus release the valve sleeve 8 for downward movement under the action of operating spring 13 to uncover the flow ports. The plug valve assembly is particularly suitable for use in a well bore, and, because the seals 222 have equal diameters, the sleeve is pressure balanced and the assembly is capable of operating in both overbalance and underbalance conditions.

Description

PLUG VALVE ASSEMBLY This invention relates to a plug valve assembly which is intended to be used in a well bore e.g for use in an oil, gas or water well.

In the oil and gas recovery industry, there are many operations which may be carried out on a well during its lifetime. All oil or gas wells have equipment associated therein which require regular maintenance. To carry out this maintenance, "plugs" have to be installed at various depths in the well by wireline operations to make the well safe.

Oil, gas and water wells are all equipped with "nipples" which are special profiles designed to house flow control and safety devices. A "lock mandrel" may be installed into one of these nipples with an additional device attached to the bottom to perform a desired function. A complete family of devices exist to close off flow and pressure from the well, these devices being known as plugs, pump open plugs, pressure cycle plugs, safety valves, and shut-in tools. These devices have many different methods of operation i.e. mechanical, hydraulic or electrical.

All plugs have to be designed to hold pressure differentials in both directions. Pressure from below is built-up due to well build-up pressure, and pressure from above due to the fact that equipment above the plug will be pressure tested by pressurising against the plug.

One example of a plug valve assembly is described and claimed in our GB 2281752 A, to which attention is drawn, to provide a background to the features of the invention disclosed herein.

According to the invention there is provided a plug valve assembly comprising a housing having a valve member which is retained in a closed position by virtue of a sleeve retained by a retaining means, an operating rod longitudinally displaceable within the housing, a ratchet mechanism in the form of spring loaded angled ball assemblies, flow ports in the housing providing communication between the interior of the housing and the exterior of the housing, said flow ports being controlled by relative longitudinal displacement of the valve sleeve, and means permitting the valve assembly to operate in overbalance and underbalance conditions.

A preferred embodiment of pressure cycle plug according to the invention will now be described in detail by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic illustration of a pressure cycle plug, with part of the housing removed to show the internal operating components; and Figures 2a and 2b show, respectively, the pressure cycle plug tool adjusted to operate, respectively, in a running position, and in a position taken up after opening.

A preferred embodiment of pressure cycle plug according to invention is an improvement to the plug valve assembly which is described and claimed in our GB patent application no 9418180.7, published under publication no GB 2281752A. The disclosure in GB 2281752A is intended to be incorporated herein by this reference, and to provide a background to the description of the preferred embodiment of the present invention.

Figure 1 illustrates the component part of the pressure cycle plug by reference numerals, and Figure 2a shows the operating position taken up by the plug tool when operating in a "running" position, whereas Figure 2b shows the position taken by the tool after "opening".

Referring in particular now to Figure 1 of the drawings, the plug valve assembly or "tool" of the invention comprises a main body 1, a nose cone 2 attached to the lower end of the body 1, and an upper body 3. A rod extension 4 is mounted within the upper body 3, and a main (stepped diameter) operating rod 6 extends longitudinally of the main body 1, and serves to operate a ratchet mechanism shown generally by reference 5.

A valve sleeve 8 is slideably mounted on the upper body 3 and an operating spring 13 reacts between the valve sleeve 8 and the upper body 3. Rod extension 4 is slidable relative to the upper body 3, against the action of rod spring 14, and a spacer 10 limits the extent of slidable movement of rod extension 4 relative to upper body 3.

A key 9 is carried by the main body 1, and projects laterally therefrom, to engage a lower extension of valve sleeve 8. Three lock pins 11 (only one shown in the drawings) project laterally from the rod 6, and are moveable longitudinally relative to the main body 1, as can be seen particularly from Figures 2a and 2b.

The ratchet mechanism comprises three ratchet springs 16, and six balls 17, and the operation of the ratchet mechanism to permit relative longitudinal displacement can be seen from Figure 1, and Figures 2a and 2b. Three grub screws 18 complete the assembly of the component parts of the ratchet mechanism.

At the upper end of the tool, a two part diaphragm seal is arranged comprising outer diaphragm ring 19 and inner diaphragm ring 20. Further sealing is provided by three 0rings 222 and one O-ring 108.

The preferred embodiment of unibalance pressure cycle plug disclosed herein is primarily intended for use by the oil and gas extraction industry, and a typical design of pressure cycle plug or tool may have the following detailed design parameters: Diameter 2.10" Made up length 10.6" Internal Flow Area through tool 1.024 Sq ins Flow area through ports 0.823 Sq ins Flow ports 4 x 13 mm Service Standard and H2S Working pressure 5,000 Psi Maximum differential pressure 5,000 Psi Minimum differential pressure per cycle 1,200 Psi Maximum overbalance 600 Psi Number of cycles 6 standard, others on request The pressure cycle plug has been designed for use in circumstances where a high test pressure will be utilised, but in which a low operating pressure is required.The pressure cycle plug can operate in both "overbalance" or "underbalance" circumstances within its specification.

The cycle plug is run below any standard lock mandrel and equalising device. When set in a nipple, repeated pressure cycles (lower pressure than tubing or tree test pressure) applied from above will cause the tool to open and give a large flow area through the lock and the plug. The tool may also be opened mechanically using a special prong.

In addition to all normal plugging operations the cycle plug has many advantages, some of which are listed below: 1. It is especially useful where sand or scale is expected to "fall out" onto the plug (which normally makes retrieval difficult). After opening the cycle plug, any fill is flowed or pumped away: 2. For suspending wells temporarily; 3. For rapid resumption of production following plugging for deviated drilling kick-off; 4. For equalising in highly deviated wells; 5. For ensuring that production may be resumed in the event of a plug being stuck.

The pressure cycle plug does not require tubing test pressures to be exceeded. The tool opens at the end of the bleed-off phase, so that complete control is available at all times. It is rugged with few components, allowing it to be "field dressed" in less than 10 minutes and no special training is required to operate the tool.

The mode of operation of the pressure cycle plug will now be described.

The pressure cycle plug operates on pressure cycles from above of 1200 psi or more. A pressure barrier is created by the two O-rings 222 and 108. In that O-ring 108 is attached to the rod extension 4, it is free to move downwards when exposed to a pressure from above. The stroke of the rod is regulated by the spacer 10 and operating pressure determined by the strength of spring 14 which also returns the rod to its original position. Well pressure below the tool will assist the return of the rod. Pressure cycles from above will cause the rod to reciprocate.

As can be seen in the drawing, the rod 6 has a stepped diameter, and during the first pressure cycle, the larger diameter on the rod bottom will pass the three lock pins 11 allowing them to collapse into the reduced rod diameter. The rod bottom will also engage the four ball/spring assemblies 16,17. When pressure is bled-off, the lock pins 11 will disengage the main body 1, and the ratchet mechanism 5 can move upwards with the rod as it is now gripped uni-directionally by the ball/spring assembly.

As the rod reciprocates with pressure cycles, the ratchet can only move upwards as the outer ball spring assemblies prevent downwards movement of the ratchet relative to the main body, and the inner spring assemblies prevent downwards movement relative to the rod.

When the ratchet component clears the three keys 9, the keys fall into the nose cone 2, and the valve sleeve 8 then becomes unsupported. The operating spring 13 is normally in compression, and forces the valve sleeve 8 downwards, breaking the pressure balanced seal normally provided by the O-rings 222, and thereby exposed the four flow ports.

When the tool is open, as shown in Figure 2B, the well may be flowed or the tool can be pumped through. In both cases, the elastomer diaphragm will be expended.

The preferred embodiment of plug valve assembly disclosed herein is therefore an improvement over existing designs, in that it has an ability to operate both "overbalance" or "underbalance". This is achieved by using a porting system which is pressure balanced. The flow ports are straddled by 2 0ring of the same diameter, and a compressed spring acts on the valve sleeve, allowing it to move to the open position when the locking keys are released.

The following advantages, inter-alia, are therefore achievable by the preferred embodiment of the invention: 1. A wire lying conveyed pressure cycle plug operable in overbalance and underbalance conditions: 2. A pressure balanced valve sleeve operable with a ratchet mechanism which is conveyed into a well bore: 3. A tool which is operable with pressure cycles applied from above.

Claims (5)

1. A plug valve assembly comprising a housing having a valve member which is retained in a closed position by virtue of a sleeve retained by a retaining means, an operating rod longitudinally displaceable within the housing, a ratchet mechanism in the form of spring loaded angled ball assemblies, flow ports in the housing providing communication between the interior of the housing and the exterior of the housing, said flow ports being controlled by relative longitudinal displacement of the valve sleeve, and means permitting the valve assembly to operate in overbalance and underbalance conditions.

2. A plug valve assembly according to Claim 1, in which the operating rod carries a lock pin which projects laterally therefrom to engage the inner surface of a main body forming a fixed part of the housing.

3. A plug valve assembly according to Claim 2, in which operating keys are mounted on said main body and project internally to be engageable with said ratchet mechanism and externally to engage slideably a lower end of an externally mounted valve sleeve.

4. A plug valve assembly according to any one Claims 1 to 3, in which the operating rod has an extension which is arranged to be free to move downwards when exposed to pressure from above, against the action of a control spring which controls the rod and the rod extension to the original position upon removal of the pressure, and also assisted in use by well pressure below the tool.

5. According to Claim 4, in which the operating rod has a stepped diameter, and said lock pins are moveable into engagement with a reduced diameter rod portion during a first pressure cycle, and the rod bottom is then engageable with said spring loaded ball assemblies such that, when pressure is bled off, the log pins disengage from said main body and the ratchet mechanism is then moveable upwardly with the operating rod and a uni-directional gripping action from said spring loaded ball assembly.