Device and a method for optional closing of a section of a well

Abstract

A device and method for optional closing of a section of a well formation (6) in which there is disposed a pipe (2), and where the pipe (2) is provided with at least two receivers (1) or pluggable openings (28), with receivers (1) or pluggable openings (28) in different sections of the well formation (6) having different dimensions and/or geometry, whereby the receivers (1) and the pluggable openings (28) are arranged so as allow optional closing of these through supplying the pipe (2) with a sealing body (4, 32) of a corresponding dimension and/or geometry.

Description

This invention regards a device for optional shut-off of the inflow from a section of a well. More specifically, it regards a device in which bodies having a specific geometry and dimension are placed in corresponding openings in a section of a well in order to be able to close the section permanently or for a period of time. The invention also includes a method of implementing the invention.

A well such as petroleum well is often lined with a casing, where the section of casing running through the well formation is perforated in order to allow the inflow of formation fluid. Due to the geological characteristics of the well formation and the extent of the well in question, and its positioning in the well formation, it may be desirable to close one or more sections of the well for a longer or shorter period of time. The aim may be to stimulate the inflow of well fluid from the other well sections or reduce the inflow or water or gas.

It is known to use surface operated inflow control valves. These are costly and often have a low operational reliability.

It is also known to lead bodies to a well section in order to plug perforations to stop inflow from the well through the perforations. Thus the publication GB 2167472A concerns a method of arranging spherical sealing bodies in perforations in the casing of a deviated well. The method entails placing the sealing bodies in perforations on the inside of the casing. The method is not suitable for shutting down fluid production, as the balls will fall out of the perforations when subjected to flow through the perforations in the opposite direction. The method is intended to limit fluid inflow into the formation, e.g. in the case of stimulation operations.

The object of the invention is to remedy the disadvantages of prior art.

The object is achieved in accordance with the invention by the characteristics stated in the description below and in the following claims.

In a tubular passage, hereinafter termed production tubing, there is disposed at least one receiver having a through opening in which the receiver is designed to sealingly capture and hold a sealing body that exhibits a geometry and dimension that correspond to that of the opening, the sealing body being preferably carried from the surface in a carrier fluid.

The receiver may, as an example, be disposed between well sections. Using several receivers in a well where each receiver is designed to be able only to capture a sealing body with a corresponding geometry and dimension, makes it possible to select which section of the well is to be closed.

If the well is to be closed, e.g. at the second receiver, counting from the surface, a sealing body is selected which can pass through the first receiver, and which is a complementary fit to the second receiver.

A receiver according to the invention is equipped with a barrier designed to prevent dislocation of the captured sealing body from the receiver after production from the well has been initiated.

In an alternative embodiment at least one flow chamber is provided between the well formation and the production tubing. The flow chamber communicates with the well formation via at least one chamber opening, possibly via a sand screen and/or other fluid flow-through devices. The flow chamber communicates with the production tubing via at least one pluggable opening and possibly via other fluid flow-through devices.

Through the construction of the pluggable opening, the flow chamber is designed only to be able to receive sealing bodies that have been given geometry and dimension corresponding to that of the pluggable opening, and also smaller sealing bodies. Other sealing bodies will not be able to pass into the flow chamber. Moreover, the shape of the pluggable opening may be such as to allow sealing bodies of a specific dimension or a specific dimensional range to only flow into the flow chamber, and not back through the pluggable opening.

By means of a sealing body flowing onwards, settling over and closing the chamber opening, any further inflow of sealing bodies and carrier fluid through the pluggable opening and into the flow chamber is prevented.

When sealing bodies are caused to flow into the production tubing from the surface, sealing bodies of a suitable geometry and a dimension smaller than or equal to that of the pluggable opening flow into the flow chamber. Sealing bodies that are unable to pass through the pluggable opening will be able to settle over and close the pluggable opening.

By providing flow chambers in different sections of the well with pluggable opening of different dimension and possibly is different geometry, it becomes possible, by introducing a specific type of sealing bodies into the well, to decide which flow chamber(s) sealing bodies are to be fed to.

When the inflow of sealing bodies to the well is stopped and well fluid is subsequently allowed to flow from the well formation and into the production tubing via the flow chamber, sealing bodies of a smaller dimension may flow back to the production tubing via the pluggable opening, while other sealing bodies located in the flow chamber remain and are able to plug the pluggable opening, thus preventing well fluid from flowing into the production tubing.

The sealing bodies may be made from a material, which dissolves over time as a result of e.g. corrosion or other chemical or thermal decomposition. It may be possible to dissolve the sealing bodies by use of certain fluids such as acids or bases, or they may be of a permanent type. Time-limited closure may be of interest e.g. when conducting tests to determine which flow chambers are to be closed.

The device is equally well suited for both lined and unlined wells.

The following describes a non-limiting example of a preferred embodiment and method illustrated in the accompanying drawings, in which:

FIG. 1 shows production tubing disposed in a well formation, which production tubing is equipped with two receivers, and where a sealing body is passing into the well;

FIG. 2 shows the same as FIG. 1, but here the sealing body has been captured in a receiver;

FIG. 3 shows production tubing equipped with two flow chambers and arranged in a well formation;

FIG. 4 shows the device of FIG. 3 on a larger scale, where a sealing body is entering the flow chamber;

FIG. 5 shows a sealing body that is too large to pass into the flow chamber; and

FIG. 6 shows a sealing body that is too large to pass out of the first opening of the flow chamber.

In the drawings, reference number 1 denotes a receiver that is placed in production tubing 2, and which is designed to capture a sealing body 4 of a corresponding geometry and dimension. The production tubing is located in a well formation 6, where sections of the well formation 6 can be separated by a packing 8 that has been set in the annulus 10 between the production tubing 2 and the well formation 6. The receiver 1 is formed with a shoulder 12 designed to prevent sealing bodies 4 with a corresponding geometry and dimension to that of the receiver 1 from passing through the receiver 1.

Advantageously, several receivers 1 are arranged along the production tubing 2 in a well formation. The receivers 1 are shaped so as to have a flow dimension, which decreases away from the surface, with the receiver 1 located closest to the surface having the largest flow dimension, and the receiver 1 located furthest away having the smallest flow dimension.

The receiver 1 is equipped with a barrier 14, which may be in the form of e.g. a flexible material or a spring mechanism of a type that is known per se. The barrier 14 is formed so as to allow a sealing body having a geometry and dimension corresponding to that of the receiver 1 in question to be moved through the barrier 14 in one direction, but not in the opposite direction. Smaller sealing bodies may pass through the barrier in both directions.

By passing a sealing body of a specific geometry and dimension into the well, it is possible to select which receiver is to be closed, see FIGS. 1 and 2.

When well fluid flows into the production tubing 2 the barrier 14 prevents the sealing body 4 from flowing back to the surface. Consequently, the receiver 1, the sealing body 4 and the barrier 14 will together form a sealing device in the production tubing 2.

In an alternative embodiment at least one flow chamber 20 is sealingly connected to the production tubing 2 and placed in the well formation 6, see FIG. 3. The sections of the well formation 6 may, as described above, be separated by a packing 8 that has been set in the annulus 10 between the production tubing 2 and the well formation 6.

The wall portion 22 of the flow chamber 20 is provided with a chamber opening 24 arranged to connect the cavity 26 of the flow chamber 20 with the well formation 6. A pluggable is opening 28 runs through the wall 30 of the production tubing 2, and is arranged to connect the cavity 26 with the production tubing 2.

By equipping a flow chamber 20 or groups of flow chambers 20 with a pluggable opening 28 of different geometry or dimensions, it becomes possible to select which flow chamber or flow chambers 20 is/are to be closed by supplying the flow chamber 20 in question with sealing bodies of a corresponding geometry and dimension.

The chamber opening 24 is dimensioned so that sealing bodies 32 of the dimension in question cannot pass through the chamber opening 24.

The pluggable opening 28 is equipped with a back flow stopper 34, where this may be constructed from a flexible material or as a spring mechanism that is known per se.

When a sealing body 32, here in the form of a ball, passes through the production tubing 2 together with a carrier fluid, the ball 32 will seek to follow the fluid out of the production tubing 2 via the pluggable opening 28, the cavity 26 and the chamber opening 24, to the well formation 6.

Balls 32 smaller than the diameter of the pluggable opening 28 will be able to flow in through the pluggable opening 28 and the back flow stopper 34 to the cavity 26, see FIG. 4, while larger balls 32 will be unable to enter the pluggable opening 28, see FIG. 5.

Upon flow from the cavity 26 to the production tubing 2, smaller balls 32 may pass back through the back flow stopper 34 and the pluggable opening 28. Balls 32 of a size that allows them into the cavity 26 through the pluggable opening 28 and the back flow stopper 34 will, due to the construction of the back flow stopper 34, upon return be stopped by the back flow stopper 34, thus sealing the pluggable opening 28, see FIG. 6.

Balls 32 present in the cavity 26 may during the inflow of carrier fluid from the production tubing 2 settle sealingly over the chamber opening 24, thus preventing further inflow of carrier fluid to the cavity 26.

By using dissolving sealing bodies 4, 32 the closing function of the sealing bodies 4, 32 may be timed or controlled through injection of liquid solvents. Thus the device of the invention makes it possible to control, which receivers 1 or flow chambers 20 are to be closed, and also how long they are to remain closed.

Claims

1. A device for optional closing of a section of a well formation (6) in which there is disposed a pipe (2), characterized in that the pipe (2) is provided with at least two receivers (1) or pluggable openings (28), with receivers (1) or pluggable openings (28) in different sections of the well formation (6) having different dimensions and/or geometry, whereby the receivers (1) and the pluggable openings (28) are arranged so as allow optional closing of these through supplying the pipe (2) with a sealing body (4, 32) of a corresponding dimension and/or geometry.

2. A device in accordance with claim 1, characterized in that the receiver (1) is provided with a barrier (14) arranged to prevent a sealing body (4) that corresponds to the receiver (1) from being displaced out of the receiver (1).

3. A device in accordance with claim 1, characterized in that a flow chamber (20) is arranged sealingly between the pipe (2) and the well formation (6), where the flow chamber (20) is communicatingly connected to the well formation (6) by means of a chamber opening (24) and to the pipe (2) by means of a pluggable opening (28), the flow chamber (20) being arranged to receive at least one sealing body (32), where the sealing body (32) is arranged to seal the chamber opening (24) and/or the pluggable opening (28).

4. A device in accordance with claim 2, characterized in that the pluggable opening (28) is equipped with a back flow stopper (34) arranged to allow the passage of a corresponding sealing body (32) in one direction but not in the opposite direction.

5. A device in accordance with one or more of the preceding claims, characterized in that the sealing body (32) is made from a dissolving material.

6. A method of optional closing of a section of a well formation (6) in which there is arranged a pipe (2), and which in addition is provided with a device in accordance with one or more of the preceding claims, characterized in that a sealing body (4, 32) of a dimension and/or geometry that corresponds to the barrier (14) or the pluggable opening (28) to be closed, is brought into the pipe (2).