GB2285076A

GB2285076A - A valve for controlling fluid flow in an oil or gas well

Info

Publication number: GB2285076A
Application number: GB9425135A
Authority: GB
Inventors: Paul Lee
Original assignee: PBL Drilling Tools Ltd
Current assignee: PBL Drilling Tools Ltd
Priority date: 1993-12-14
Filing date: 1994-12-13
Publication date: 1995-06-28
Anticipated expiration: 2014-12-13
Also published as: GB9425135D0; GB2285076B; GB9325578D0

Abstract

The valve is suitable for controlling fluid flow in a drill string of an oil or gas well installation. The valve comprises a tubular casing 2 with a port 3 located in the casing 2; a sleeve 4 is slidable within the casing from a first position in which fluid flow through the port 3 is prevented, and a second position in which the port 3 is open. Tool activation means is provided for moving the sleeve 4 between its first and second positions. The tool activation means is operated by a change of direction of fluid flow through the valve. The valve can be activated any number of times without having to manually reset the valve or remove it from the drill string. <IMAGE>

Description

A VALVE FOR CONTROLLING FLUID FLOW IN AN OIL OR GAS WELL This invention relates to a valve for controlling fluid flow in an oil or gas well. The invention is suitable for use as a downhole tool for controlling the flow of well fluids in the drill string and annulus.

A number of problems can occur during drilling operations, examples include blowouts, differential sticking and mud circulation loss. These serious problems are often caused by differences in pressure in the rock formation being drilled and the surface or the fluid pressure in the drill string. Mud circulation loss can occur when the mud moves into a geological formation. To prevent further fluid loss a sealing fluid is pumped into the formation. The sealing fluid may comprise a mixture of mud and wood chips.

To solve these problems can be expensive and in many cases requires use of a separate tool which is inserted into the drill string. A known conventional tool or downhole valve for controlling the circulation of well fluids uses a slidable sleeve within the drill string to control opening and closing of ports between the drill string and the annulus. The tool is activated by opening the drill string at the surface and inserting a first ball into the drill string. The first ball is pumped down the drill string to the downhole valve where it engages a constriction in the slidable sleeve and opens the ports. Well fluids can then be pumped directly into the annulus. To deactivate the tool the drill string is once again opened and a second ball of a smaller diameter is inserted into the drill string.This ball blocks the opened port in the tool causing an increase of pressure within the drill string. At a predetermined pressure the first ball deforms and is forced through the sleeve followed by the second ball. The balls are held in a retaining device. In this way the tool can be activated a number of times without having to withdraw the drill string. The number of times the tool can be activated and deactivated is limited by the capacity of the ball retaining device which holds used balls. Eventually the device must be removed from the drill string and the balls emptied.

Although the known device is an improvement over the original techniques for solving these problems, it has the disadvantage that the drill string must be opened each time the tool is activated and deactivated. It also has a limited number of activation and deactivation operations due to the use of balls.

Furthermore, a stock of different size balls must be kept for operation of the tool. Activation of the tool is time consuming and very careful monitoring of the pressure is required to prevent the first ball being blown through the device as it is being pumped down the drill string.

The invention seeks to- overcome these problems by providing a valve for controlling the flow of well fluids in a an oil or gas well installation which does not require the use of externally supplied balls to activate and deactivate the tool.

According to the invention there is provided a valve for use when drilling an oil or gas well which comprises: a tubular casing with a port located in the casing; a sleeve slidable within the casing from a first position in which fluid flow through the port is prevented, and a second position in which the port is open; and tool activation means for moving the sleeve between its first and second positions, said tool activation means being operable by a change of direction of fluid flow through the valve.

The valve of the invention has the advantage that the drill string does not need to be opened and a ball pumped down the drill string to activate or deactivate the tool. Furthermore, the valve of the invention does not have a limited number of operations or cycles due to limited capacity of the device to hold a predetermined number of balls. The valve of the invention can be activated any number of times and can be activated without having to monitor pumping pressures carefully so as to avoid blowing a deformable ball through the valve.

Substantial savings in production time are achievable with the valve when compared with existing downhole tools.

The activation means may comprise a captive ball adapted to seat on a shoulder provided on the slidable sleeve wherein engagement of the ball and the shoulder causes the sleeve to move from its first position to its second position. The ball is not deformable and cannot be accidentally blown through the valve. It is not as susceptible to operator error or control as known constructions of valve.

The sleeve may be biased to its first position by a spring, and movement from its first position to its second position may be achieved by an increase in fluid pressure. The tool can be activated by pumping fluid through the valve to cause the ball to engage the sleeve. This momentarily seals the valve and causes an increase in pressure thereby forcing the sleeve into its second position and opening the port.

Preferably, R plurality of ports are provided in the casing, all of which are opened when the sleeve moves from its tirst position to its second position. Fluid flow through the valve and into the annulus is enhanced. Known devices were constrained to a single port because of the use of a second ball to close the port.

Preferably, ball retaining means is provided to retain the ball captive when the tool is in its deactivated condition.

The ball retaining means may comprise a cage which restrains movement of the ball but permits flow of well fluids through the valve. The cage does not restrict the flow of fluids through the valve.

Preferably, the ball retaining means comprises a track secured to the internal surface of the sleeve, the ball being slidably connected to the track. The ball can slide along the track and the range of movement of the ball is limited by the length of track. The ball slides along the track according to the flow of fluids within the valve.

Preferably, the cage comprises a plurality of fingers extending radially inwards from the casing.

Generally, the casing comprises a first section housing the slidable sleeve and a second section housing the ball retaining means. This enables the valve to be split at the surface to facilitate cleaning and maintenance of the valve.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side view of the valve with portions cut away to show the internal components of the valve in its deactivated position; Figure 2 is a cross-sectional view of the valve shown in Figure 1 but in the activated position; and, Figure 3 is a side view of a valve with portions cut away to show the internal components of the valve, in particular an alternative form of ball retaining means.

Referring to the drawings, Figure 1 shows a downhole valve according to the invention, generally indicated by reference numeral 1, which comprises a tubular casing 2 with a port 3 located in the casing 2; a sleeve 4 is slidable within the casing 2 from a first position in which fluid flow through the port is prevented (as shown in Figure 1), and a second position in which the port is open (as indicated in Figure 2). Tool activation means is provided for moving the sleeve between its first and second positions.

The tool activation means comprises a steel ball 5 and ball retaining means to prevent the ball 5 moving up through the drill string. The ball retaining means comprises a cage 9 which prevents the steel ball 5 rising up the drill string with upward fluid flow but permits relatively unconstricted flow of fluids. When activated the steel ball 5 engages and seats on the shoulder 6 provided on the sleeve 4.

The valve comprises two sections. A first section 7 houses the slidable sleeve 4 and a second section 8 houses the cage 9.

This split section construction facilitates access to the cage 9 and to the sleeve 4 for routine maintenance and cleaning.

The junction between the two sections 7, 8 also provides an abutment 10 which restricts upward movement of the slidable sleeve 4 within the casing 2.

Figure 3 shows a further embodiment of ball retaining means which comprises a track 30 fixed to the internal surface of the sleeve 31 via retaining ring 32. The ball 33 is connected to the track so that movement of the ball 33 is limited to sliding movement along the track. Stop 34 prevents the ball from sliding off the end of the track at end 35, and valve seat 36 prevents the ball sliding off the end 37 of the track. A seal 38 is provided in the ball 33 to prevent leakage of fluids through the valve when in the closed or activated position.

The valve is operated by a change of direction of fluid flow through the valve. In figure 1 the valve is shown in its deactivated position where fluid flows down the annulus and up the drill string (fluid flow shown by arrows). The upward flow of fluid moves the steel ball 5 into the cage 9 where further upward movement of the ball is restrained. The sleeve 4 is biased in its first position by a spring 12. The ports 3 and 11 are misaligned and fluid flow is prevented. To activate the valve fluid is pumped down the drill string. The downward flow of fluid causes the steel ball 5 to move down the valve and engage the seat 6 on the sleeve 4. Continued pumping causes a rise in pressure in the drill string forcing the sleeve 4 to its second position (as shown in Figure 2). In this position fluid can flow from the drill string and through the aligned ports 3, 11 in the sleeve and the casing and out into the annulus (fluid flow shown by arrows in figure 2). The valve shown in Figure 3 operates in a similar way but instead of the cage limiting movement of the ball, the ball is restricted to sliding along the track 30.

Claims

CLAIMS:

1. A valve for controlling fluid flow in an oil or gas well which comprises: a tubular casing with a port located in the casing; a sleeve slidable within the casing from a first position in which fluid flow through the port is prevented, and a second position in which the port is open; and tool activation means for moving the sleeve between its first and second positions, said tool activation means being operable by a change of direction of fluid flow through the valve.

2. A valve as claimed in claim 1, in which the activation means comprises a captive ball adapted to seat on a shoulder provided on the slidable sleeve wherein engagement of the ball and the shoulder causes the sleeve to move from its first position to its second position.

3. A valve as claimed in claim 2, in which the sleeve is biased to its first position by a spring and movement from its first position to its second position is caused by an increase in pressure.

4. A valve as claimed in any preceding claim, in which a plurality of ports are provided in the casing, all of which are opened when the sleeve moves from its first position to its second position.

5. A valve as claimed in any one of claims 2 to 4, in which ball retaining means is provided to retain the ball captive when the tool is in its deactivated condition.

6. A valve as claimed in claim 5, in which the ball retaining means comprises a cage which restrains movement of the ball but permits flow of well fluids through the valve.

7. A valve as claimed in claim 5, in which the ball retaining means comprises a track secured to the internal surface of the sleeve, the ball being slidably connected to the track.

8. A valve as claimed in claim 6, in which the cage comprises a plurality of fingers extending radially inwards from the casing.

9. A valve as claimed in any one of claims 5 to 8, in which the casing comprises a first section housing the slidable sleeve and a second section housing the ball retaining means.

10. A valve according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.