Field of the invention

The present invention relates to a metering device for discharging an amount of fluid and a method to supply a constant, discrete hydraulic volume.

Background of the invention

Balanced hydraulic pistons are the preferred actuation method for interval control valves (ICVs) that are used to allow or prevent flow from compartments of a subterranean reservoir completion. The balanced piston responds to differential pressure in one of two directions. Differential pressure is created by applying pressure from surface to one of two hydraulic conduits, called control lines, that connect to either side of the balanced piston. Due to the geometry of the hydraulic conduits, which can be very long and very small in diameter, it is impossible to control from the input side the volume that exits the downhole side of the conduit when pressure is applied and, as a result, the balanced piston will typically move the full length of travel available. The problem with full length travel is that it provides only two positions for the ICV, full open or full closed. In many applications, it has become desirable to have the ICV positioned somewhere between the full open and full closed positions; these incremental positions referred to as a percent (%) of the full open position, where the percent typically refers to the cross-sectional area of the ICV flow ports in the incremental position compared to that of the full open position. The present invention therefore addresses the problem of providing a discrete hydraulic volume output in response to a single pressure input cycle, regardless of the level of pressure and how much time that pressure input is applied, such that the ICV balanced piston does not receive enough volume to move the full travel available. The present invention allows multiple pressure input cycles, consisting of pressure applied to a minimum system functional threshold followed by relief of said applied pressure, to be provided in order to move the ICV balanced piston in multiple increments from the fully closed to fully open positions.

Disclosure of the state of art

US 2010/0051289 A1 discloses systems for operating one or more sliding sleeve valves in an incremental, step-type fashion between open and closed positions, permitting the valve or valves to be choked to progressively smaller flow areas. The systems also permit the valve or valves to be fully closed without having to progress through incremental steps.

WO 2010/019432 A1 discloses a hydraulic fluid metering control module in cooperation with a downhole component. The downhole component is shifted via hydraulic fluid delivered through first and/or second control lines to an actuator of the downhole component. The hydraulic fluid metering control module works in cooperation with the actuator and the control lines to enable shifting of the actuator according to a controlled, incremental process.

US6585051 B2 describes a hydraulically operated fluid metering apparatus provides discharge of a known volume of fluid to an actuator of a well tool.

US7510013B2 describes a method and system for operating a sliding sleeve valve or other downhole well tool that is axially shiftable among a finite number of increments between two extreme configurations such as open and closed configurations.

A disadvantage with found in the prior art is that the solutions and devices comprise a multitude of moving parts and that inherently increases the risk of failure.

Objects of the present invention

One object of the invention is to provide a simple and reliable fluid metering device.

Another objective is to provide a new design for a fluid metering device to be used to displace a precise volume of fluid each time the fluid metering device is actuated.

Yet another object is to provide a new design for a fluid metering device for activating down hole tools by displacing a precise volume of fluid every time the fluid metering device is actuated.

Yet another object is to provide a simple and reliable design for a fluid metering device with as few components as possible.

Yet another object is to provide a solution for operating an ICV in increments. Summary of the invention

At least some or all of the above mentioned objects are solved with a metering device for discharging an amount of fluid, said metering device comprises a discharge device comprising a discharge cylinder and a discharge piston, said discharge cylinder having a predefined fluid volume being displaced when fluid pressure is applied, and a metering biasing member acting with a biasing force on the discharge piston allowing resetting and refilling of the discharge device with fluid when the force from the fluid pressure is removed. The metering device further comprising a metering check valve preventing flow from the input chamber to the input line, and a recharge device with a recharge shuttle slidable between a first position closing of a fluid connection between an inlet chamber and an outlet chamber of the discharge device and a second position opening up said fluid connection. The recharge shuttle comprises a piston area in fluid connection with the input chamber and a piston area in fluid connection with an input line of the discharge device, and a recharge biasing member is acting with a force on the recharge shuttle in opposite direction of the force from the pressure in the input chamber.

The metering device can be connected to an ICV with an actuator.

The input line can be connected to a first side of the discharge device and an output line on a second side of the discharge device can be connected to an ICV actuator to open said ICV, wherein the input chamber is connected to said input line, and the output chamber is connected to said output line, wherein the discharge piston is separating said output chamber from said input chamber, and the metering biasing member is acting on said discharge piston with a force in the direction of the input chamber.

The metering device can comprise a bypass line with a bypass check valve allowing fluid flow from the output line to the input line.

The metering check may further be placed inside the discharge piston, in where the discharge piston can have a T-shape with a small piston area and a large piston area.

The invention also relates to a method to supply a constant, discrete hydraulic fluid volume using a metering device, wherein the method comprises the steps of: - applying fluid pressure above a predefined threshold to an input line,

- filling up an input chamber through a metering check valve on a first side of a discharge piston to move the discharge piston,

- pushing a predefined volume of fluid into an output line from an output chamber on a second side of the discharge piston,

- bleeding of pressure in the input line reliving a backpressure on a recharge shuttle,

- returning the discharge piston,

- moving the recharge shuttle against a recharge biasing member opening up a passage between the input chamber and the output chamber, and

- refilling the output chamber with fluid from the input chamber.

Fluid from the output line can be evacuated to the input line by bypassing the metering device through a bypass check valve.

The metering device may be connected to an ICV with an actuator, for operation of said ICV.

Description of the figures

Embodiments of the present invention will now be described, by way of example only, with reference to the following figures, wherein:

Figure 1 - 4 shows the operation of first embodiment of the invention in sequence.

Figure 5-8 shows the operational sequence of a second embodiment of the invention.

Reference numbers:

1 Metering device

2 Input line

3 Output line

4 Output chamber

5 Discharge piston

6 Metering biasing member

7 Metering check valve

8 Input chamber

9 Recharge shuttle

10 Recharge biasing member

11 Bypass check valve 12 Recharge device

13 Discharge device

14 Discharge cylinder

Description of preferred embodiments of the invention

Figure 1 shows a first possible embodiment of a metering device 1 according to the invention. The metering device comprises a single input line 2 and a single output line 3, between which lies the functional components of the metering device 1.

The output line 3 can be connected to a downhole tool such as an ICV (Inflow Control Valve) or any other downhole tool requiring hydraulic actuation, where fluid output from the output line 3 is discharged into a hydraulic actuator on an ICV or some other downhole tool. The metering device 1 and the method can also be used for several applications where there is a need to supply a dose of a fluid in response to an increase in pressure. Other applications in addition to downhole tools might be compression systems, chemical dosing systems, fluid sampling, combustion system and fluid dispenser for various applications.

The metering device 1 comprises a discharge device 13 with a discharge cylinder 14 and a discharge piston 5, said discharge cylinder 14 having a predefined fluid volume being displaced when fluid pressure is applied. In the discharge cylinder 14 a metering biasing member 6 is acting with a biasing force on the discharge piston 5 allowing resetting and refilling of the discharge device 13 with fluid when the force from the fluid pressure is removed.

When pressure is applied to the input line 2, a metering check valve 7 allows fluid to pass and the pressure acts against a piston area of a discharge piston 5. The discharge piston 5 moves in the direction of differential pressure and compresses a metering biasing member 6 until the discharge piston 5 bottoms out inside or at an output chamber 4 (Fig 2).

The amount of fluid discharged out of the output line 3 is equal to the change in volume of the output chamber 4.

When pressure is relieved from the input line 2, the metering check valve 7 closes due to higher pressure in the input chamber 8 compared to that of the input line 2. The input line 2 is connected to a recharge device 12 where it acts on a recharge shuttle 9 with a backpressure. When the pressure in the input line 2 is reduced sufficiently the differential pressure across the recharge shuttle 9 is increased so the pressure in the input chamber 8 can overcome the biasing force of a recharge biasing member 10. This will cause the recharge shuttle 9 to compress the recharge biasing member 10 such that the input chamber 8 is then connected to the output line 3 (Fig 3) and allows the metering biasing member 6 to return the discharge piston 5 to the starting position (Fig 4).

In other words, the output chamber 4 is refilled with fluid from the input chamber 8 as the discharge piston 5 is returned by the metering biasing member 6. The recharge device 12 connects the input chamber 8 to the output chamber 4 when pressure is relieved in the input line 2.

Hence, the recharge shuttle 9 of the recharge device 12 is slidable between a first position closing of a fluid connection between the inlet chamber 8 and the outlet chamber 4 of the discharge device 13 and a second position opening up said fluid connection. A first piston area of the recharge shuttle 9 is thus in fluid connection with the input chamber 8 and a second piston area is in fluid connection with the input line 2 of the discharge device 13. The recharge biasing member 10 is acting with a force on the recharge shuttle 9 in opposite direction of the force from the pressure in the input chamber 8.

An optional bypass line with an optional bypass check valve 11 can be included so that anytime pressure is applied from the output line 3, fluid can bypass the metering device 1 to evacuate into the input line 2.

Figure 5 -8 shows a second possible embodiment of the invention where the metering check 7 is placed inside the discharge piston 5. In this embodiment the discharge piston 5 can have a T-shape with a small piston area and a large piston area. The metering check valve 7 allows fluid to flow to the input chamber 8. This embodiment might have an advantage for packaging a compact design. The second embodiment works similar to the first embodiment disclosed in relation to fig. 1-4.

The discharge cylinder 14 and the recharge device 12 is not limited to a cylindrical shape, any design that can supply adequate fluid isolation towards a piston or a shuttle and serves the same purpose can be utilized. As an example, for some applications an annular shape can be utilized. The term cylinder is however used for simplicity in both the description and in the claims.

The term metering device is a broad term and can also imply a choke module or part of a choke module.