Pressure Barrier Apparatus

Abstract

A pressure barrier apparatus 2 for providing a removable pressure barrier in a borehole is described. The apparatus comprises a housing 6, 8 defining a central bore 10 having a first part 20 and a second part 22 separated by an erodeable pressure barrier member 18. The housing also defines a second fluid flow passage 12 for connecting the first part to the second part, and a plurality of conduits 24 for directing fluid onto the barrier member to cause erosion of the barrier member. A sleeve 30 has a first condition in which fluid communication between the first part 20 and the second fluid flow passage 12 is prevented, and a second condition in which fluid is permitted to flow from the first part to the second fluid flow passage to cause erosion of the barrier member.

Description

A preferred embodiment of the invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which:

FIG. 1A is a side cross sectional view of plug housing for a pressure barrier apparatus embodying the present invention;

FIG. 1B is a side view of the plug housing of FIG. 1A;

FIG. 2 is a cross sectional side view of a pressure barrier apparatus embodying the present invention, incorporated into a downhole tool and prior to actuation thereof;

FIG. 3 is a view corresponding to FIG. 2 immediately after actuation of the pressure barrier apparatus;

FIG. 4 is a view corresponding to FIG. 2 showing the apparatus of FIGS. 2 and 3 after complete erosion of the pressure barrier member; and

FIG. 5 is an enlarged cross sectional view of the pressure barrier member and plug housing of the apparatus of FIGS. 2 to 4 with flow established after actuation of the apparatus, but prior to any significant erosion of the barrier member.

Referring to FIG. 2, a pressure barrier apparatus 2 embodying the present invention has a housing 4 having screw threads (not shown) at its ends for enabling the apparatus 2 to be incorporated into a downhole tool. The housing 4 includes an inner housing part 6 and an outer housing part 8. The inner housing part 6 defines a first fluid flow passage in the form of a central bore 10 to enable hydrocarbons to be removed from a well (not shown) in an upward direction as shown in FIGS. 2 to 4.

The inner housing part 6 is located within the outer housing part 8 such that an annular second fluid flow passage 12 is defined between the inner 6 and outer 8 housing parts. A plug housing 14 is located inside the inner housing part 6 and defines a constriction 16 in which an erodeable pressure barrier member 18, formed from sand and a bonding agent, is securely located, such that the central bore 10 is divided into a first part 20 below the pressure barrier member 18 and a second part 22 above the pressure barrier member 18, such that flow from the first part 20 to the second part 22 is prevented by the barrier member 18.

The plug housing 14 is also provided with a series of conduits 24 which are inclined relative to the longitudinal axis 26 of the tool, such that when fluid flows upwards in the annular second fluid flow passage 12, some of the fluid enters the conduits 24 and is directed to the pressure barrier member 18, as a result of which erosion of the pressure barrier member 18 takes place.

The second fluid flow passage 12 is connected to the second part 22 of the central bore 10 by means of a series of apertures 28 in the inner housing part 6. An actuator mechanism includes a sleeve 30 axially slidably located within the inner housing part 6 and having seals 32, 34 located between the inner housing part 6 and the sleeve 30. The sleeve 30 is provided with apertures 36 through its wall, and the inner housing part 6 is provided with apertures 38 for fluid communication with the apertures 36 in the sleeve 30 when the apertures 36 in the sleeve 30 and the apertures 38 in the inner housing part 6 are aligned.

In the position shown in FIG. 2, the apertures 36 in the sleeve 30 and the apertures 38 in the inner housing part 6 are not aligned, and the seals 32, 34 therefore prevent passage of fluid from the first part 20 of the central bore 10 into the second fluid flow passage 12. As a result, fluid flow to the second part 22 of the central bore 10 is prevented by the pressure barrier member 18.

In order to actuate the apparatus, the sleeve 30 is moved upwardly relative to the inner housing part 6, by means of one or more methods which will be known to persons skilled in the art. For example, an on board electronic timer (not shown) is programmed prior to installation of the apparatus 2 in a wellbore. The delay time may be many weeks or months. The timer is controlled by a micro processor, is powered by batteries and has an electronic output which may actuate an electric motor or small explosive pyrotechnic actuator (not shown). The actuator will function following expiry of the programmed delay time and will allow well pressure to communicate to a piston surface of the sleeve 30. An air chamber on the back side of the piston surface will provide the sleeve 30 with a large imbalance when exposed to the well pressure. This force is used to push the pressure barrier sleeve 30 to the open position allowing a flow path to be established around the back of the erodable pressure barrier 18 and through the annular second fluid flow path 12.

When this occurs, the apertures 36 in the sleeve 30 become aligned with the apertures 38 in the inner housing part 6, as shown in FIG. 3. As a result, fluid can flow from the first part 20 of the central bore 10, via the annular second fluid flow passage 12, through the apertures 28 into the second part 22 of the central bore 10. At the same time, and as shown in greater detail in FIG. 5, fluid passing along the second fluid flow passage 12 enters the conduits 24 in the inner housing part 6 and is directed into contact with the barrier member 18. Turbulence in the fluid flowing into the conduits 2.4 and coming into contact with the pressure barrier member 18 causes rapid erosion of the barrier member 18, as a result of which the barrier member 18 eventually disappears, and fluid can flow directly along the central bore 10 from the first part 20 to the second part 22, in preference to being directed through the second fluid flow passage 12.

In the event of failure of fluid flow in the second fluid flow passage 12 to erode the barrier member 18, for example as a result of blockage of the conduits 24, the barrier member 18 can be eroded by means of fluid flow introduced into the second part 22 of the central bore 10, for example by means of a tube (not shown) introduced into the upper end of the apparatus 2.

It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims. For example, instead of causing fluid flow in a second fluid flow passage 12, static fluid can be present in the apparatus 2 when introduced into the borehole, and flow of the fluid can be subsequently caused, bringing flow of the fluid into contact with the barrier member 18 causing erosion and subsequent removal of the barrier member 18.

Claims

1. A pressure barrier apparatus for providing a removable pressure barrier in a borehole, the apparatus comprising: a housing defining a first flow passage having a first part and a second part separated in use by an erodeable pressure barrier member, a second fluid flow passage for connecting said first part to said second part, and at least one conduit for directing at least a portion of fluid flowing in said second fluid flow passage onto said barrier member to cause erosion thereof.

2. An apparatus according to claim 1, wherein the housing defines a constriction for receiving the barrier member.

3. An apparatus according to claim 1, wherein at least one said conduit is inclined relative to a longitudinal axis of the housing.

4. An apparatus according to claim 1, wherein at least one said conduit comprises a slot.

5. An apparatus according to claim 1, further comprising an actuator mechanism having a first condition in which fluid communication between said first part and said second fluid flow passage is prevented, and a second condition in which fluid is permitted to flow from said first part to said second fluid flow passage to cause erosion of said barrier member.

6. An apparatus according to claim 5, wherein the actuator mechanism comprises a sleeve having at least one aperture therethrough, wherein the sleeve is moveable between a first position in which fluid communication is established between the first part and the second fluid flow passage via at least one said aperture, and a second position in which fluid flow between the first part and the second fluid flow passage is prevented.

7. An apparatus according to claim 1, further comprising an erodeable barrier member for blocking the first fluid flow passage between said first part and said second part.

8. An apparatus according to claim 7, wherein an external profile of the barrier member matches an internal profile of said constriction.

9. An apparatus according to claim 7, wherein the barrier member comprises sand and a bonding agent.

10. An apparatus according to claim 7, further comprising a sealing membrane separating the barrier member from the first part.

11. An apparatus according to claim 7, further comprising a sealing membrane separating the barrier member from the second part.

12. A removable pressure barrier apparatus for location in a borehole, the apparatus comprising a housing defining a fluid flow path, and a pressure barrier member adapted to block fluid flow in said flow path and to be eroded by means of fluid flow to permit fluid flow in said flow path.