WO2016036256A1

WO2016036256A1 - A tool and a method for aiding transport of a first well fluid

Info

Publication number: WO2016036256A1
Application number: PCT/NO2015/050152
Authority: WO
Inventors: Bernt Sigve AADNØY; Henning Hansen
Original assignee: Aadnøy Bernt Sigve
Priority date: 2014-09-05
Filing date: 2015-09-04
Publication date: 2016-03-10
Also published as: NO20170509A1

Abstract

A tool (1) and a method for aiding transport of a first well fluid (4) from a well (3) through a flow path (9) of the wellbore (1), and where the tool (1) includes a stirrer (26) that is in communication with the flow path (9) of the wellbore (1), and where the stirrer (26) is designed to break up the first well fluid (4) into droplets and reduce the size of first well fluid (4) droplets for commingling with at least one other well fluid (8).

Description

A TOOL AND A METHOD FOR AIDING TRANSPORT OF A FIRST WELL FLUID

There is provided a tool for aiding transport of a first well fluid from a well through a flow path of the well . The invention also includes a method for aiding transport of a first well fluid from a well and through a flow path of the well .

The present invention is particularly relevant to the field of improving fluid unloading in a gas producing well where fluids such as water typically prevents steady or any flow of gas due to downhole water build-up. Such water unloading is often referred to as gas well dewatering or gas well deliquification.

During production of oil and gas, water is normally produced simultaneously. In small fractions, this is not a problem. However, water fraction typically increases with production from gas wells, and eventually the well is producing only water and production will cease.

The production rate depends on the wellhead pressure. Gas has low density so the hydrostatic head of a gas column is low. When too much water enters a well where there is not sufficient reservoir pressure resulting in high gas flow rate to transport water to surface along with the gas, water will accumulate inside the production tubing wall followed by water flowing back to the bottom of the well, leading to increase in the hydrostatic pressure, ultimately preventing flow of gas from the reservoir. The same effect is present in oil wells too, but to a lesser extent. The prime factor is the density difference between gas, oil and water.

If a well is already filled up with water, and then not naturally flowing anymore, the well may be pumped empty of water until production of gas is re-established. Such water removal may be performed by pumping nitrogen into the reservoir from the surface, by deploying a temporarily installed downhole pump, by circulating gas through a coiled tubing deployed into the wellbore or other industry known methods. In highly deviated or horizontal wells, there is another flow restriction issue. Water fills the lower portions of the wells due to high density. Gas flows in the open space above the water. The result is an increased pressure drop because of narrower space. The water may also fill the entire cross section of the wellbore. There may not be sufficient energy in the gas to force the water out. Even if bubbles of gas come through, the water will again fill the bottom of the undulated well, and flow will eventually stop. The phenomena described above are termed "Watered out wells". It is well known that some wells just stop producing because water content becomes too high. To solve this problem, the water must be removed from the well. Artificial lift such as mechanical, hydraulic or electrical pumps and gas lift are common solutions. However, even with artificial lift the problem above can occur in deviated wells.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

The object is achieved through features, which are specified in the description below and in the claims that follow.

The invention describes a tool stirring up fluids in a wellbore, where this tool has a stirrer, the stirrer may also be referred to as a mixer or blender that breaks up fluid or fluid bubbles passing through the tool. Such a tool system may also be referred to as a mist generator. Using such a tool will improve the flow through a wellbore.

The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect the invention relates more particularly to a tool for aiding transport of a first well fluid from a well through a flow path of the well, wherein the tool includes a stirrer that is in communication with the flow path of the wellbore, and where the stirrer is designed to break up the first well fluid into droplets and reduce the size of first well fluid droplets for commingling with at least one other well fluid .

The fluid to be treated is termed "first well fluid" while another fluid that the first well fluid is commingled into, is termed "other well fluid".

Generally, the smaller the size of the first well fluid droplets, the more efficient is the transport with another well fluid or fluid bubbles to the surface. The stirrer may, as mentioned above, be a mixer or blender that breaks up fluid bubbles as they passes through the stirrer. The working principle of such a stirrer is well known from items such as a domestic mixer.

The first well fluid is most likely a liquid, but may in some cases be a gas.

The broken up first well fluid may, when commingled with at least one other well fluid, be flowable to the surface.

The first well fluid may be flowing through the flow path, or be substantially stagnant when stirred. The term "substantially stagnant" indicates that the first well fluid has the form of a liquid that is gathered in the lower portion(s) of the well. Due to nearby flow, some movements may still be present in the first well fluid.

The stirrer may receive its driving energy from a turbine that is positioned in the flow path of the well and driven by a fluid flowable through the flow path. In a preferred embodiment the stirrer and the turbine rotates on a common bearing supported shaft. The turbine is adapted to be suitable for the actual fluid flow. In some cases the turbine is termed a propeller.

The tool may thus be autonomous as the turbine at one end drives a stirrer at the other end of a shaft. The energy of the flowing fluids through the tool drives the turbine and stirrer.

The driving energy to the stirrer may be supplied from locally stored energy. The energy may for instance be electric or hydraulic and coming from a suitable accumulator. In this case, the stirrer is coupled to a motor. The energy may come from an external source, such as at the surface.

The tool may be installed as part of a well tubular such as a production tubing or a casing string. The tool is typically equipped with an anchor of known design that is capable of fixing the tool to the actual surroundings.

The tool may be designed to be replaceable by wellbore intervention for instance by wireline, coiled tubing or a similar technique.

In a second aspect the invention relates more particularly to a method for aiding transport of a first well fluid from a well and through a flow path of the well, wherein the method includes:

positioning a tool having a stirrer that is in communication with the flow path of the wellbore; - letting the stirrer break up the first well fluid into droplets and reduce the size of first well fluid droplets for commingling with at least one other well fluid; and

- transporting the commingled fluids to the surface.

The tool may be installed in wells that are flowing gas, as there is then the energy available to drive the turbine and the stirrer of the tool. The stirrer serves several functions such as: bringing heavier fluids into a flowing stream, breaking molecules to smaller sizes thereby improving transport up the well, breaking up gas bubbles so heavier molecules can be attached to the gas bubbles, and in general provide mixing between several different fluids or gases to improve transport efficiency.

Flowing heavy oil to the surface is also a common challenge, due to the viscosity of such oil. The flow may be improved by the tool as the stirring action may also reduce the viscosity of the fluids, thereby improving the flow of heavy oil.

The tool and method according to the invention disclose a much-simplified solution particularly to the long felt problem of water producing gas wells.

In the following is described examples of preferred embodiments and methods illustrated in the accompanying drawings, wherein :

Fig. 1 shows an undulated wellbore, where water is trapped in the lower portions of a so-called horizontal well ;

Fig. 2 shows the undulated wellbore of fig. 1, where increase in water produced from a reservoir is trapped and unable to flow freely towards the surface;

Fig. 3 illustrates a tool having a stirrer and installed in vertical section of a gas producing wellbore;

Fig. 4 shows a variation of fig. 3, where the stirrer is mounted in the lower end portion of the tool;

Fig. 5 shows an embodiment where a tool is installed at the lower portion of the well shown in figs. 1 and 2; and

Fig. 6 shows a wellbore that has several tools installed at various depths.

On the drawings, the reference number 1 denotes a wellbore in a formation 2. In figs. 1, 2 and 5 the wellbores 1 have the form of undulated so-called horizontal wells 3, while figs. 3, 4 and 6 show a wellbore 1 in the form of vertical wells 3. The well 3 is only shown in fig. 6.

In fig. 1, that shows a wellbore 1, a first well fluid 4 in the form of water is collecting at the lower portions 6 of the undulated, horizontal wellbore 1. Other well fluids 8 such as oil and gas will travel to surface not shown through a flow path 9 of the wellbore 1 above the first well fluid 4 surface 10.

Fig. 2 shows the same undulated, horizontal wellbore 1 as shown in fig. 1, but where increase of water in first well fluid 4 has filled the wellbore 1. The first well fluid 4 is trapped and unable to flow freely towards the surface, not shown, within the horizontal wellbore 1. Other well fluids 8, typical in the form of oil and gas flow will be greatly held back from flowing through the wellbore 1.

Fig. 3 illustrates a tool 12 that is installed in a vertical section of a well tubular 14 of the wellbore 1. The tool 12 includes a housing 16 having thoroughgoing fluid flow openings 18. The housing 16 is equipped with prior art anchors 20 for fixing the tool 12 to the well tubular 14. Such anchors 20 may be set and retrieved by known well intervention methods as for example wireline, wellbore tractors, coiled tubing and the like not shown.

A turbine 22 is in this embodiment positioned above the housing 16 and running on a common shaft 24 with a stirrer 26. The stirrer 26 is here positioned below the housing 16. The shaft 24 is passing through the housing 16 and running in a bearing 28.

Relatively large drops 30 of first well fluid 4, here water, is carried by the other well fluid 8, here in the form of gas. The droplets 30 are broken into smaller droplets when passing the stirrer 26 so that the first well fluid 4 more readily will follow the other well fluid 8 through the wellbore 1.

Fig. 4 shows a variation of the tool 12 in fig. 3, where the stirrer 26 is positioned at the upper portion of the tool 12.

Fig. 5 shows an embodiment where the tool 12 is placed in the undulated horizontal wellbore 1. The stirrer 26 is partly submerged in the first well fluid 4. The stirrer 6 rotates by torque transmitted through the shaft 24 from the turbine 22. The first well fluid 4 is broken up into droplets and transported through the wellbore 1 with the flow of another well fluid 8 that is also driving the turbine 22.

Thus, as the stirrer 26 is rotates, it throws up the first well fluid 4, here water, from the lower portion 6 of the wellbore 1 such that the first well fluid 4 may be transported away by the flowing other well fluid 8, here gas or oil. The stirring is also breaking the first well fluid 4 droplets into smaller droplets or mist, which makes the first well fluid 4 more suitable for transport. Some of the first well fluid 4 that is transported away may condensate and flow back to the lower portions 6. The process may then be re- peated.

Fig. 6 shows a wellbore 1 where several tools 12 are installed at various depths in a wellbore tubing 32 to ensure stable flow of first well fluid 4 (shown in figs. 1, 2 and 5) to the surface.

All illustrations of the drawings are for the purpose of describing selected versions of the present invention and are not intended to limit the scope of the present invention.

Claims

C l a i m s

1. A tool (1) for aiding transport of a first well fluid (4) from a well (3) through a flow path (9) of the wellbore (1), c h a r a c t e r i z e d i n that the tool (1) includes a stirrer (26) that is in communication with the flow path (9) of the wellbore (1), and where the stirrer (26) is designed to break up the first well fluid (4) into droplets and reduce the size of first well fluid (4) droplets for commingling with at least one other well fluid (8).

2. A tool (1) according to claim 1, c h a r a c t e r i z e d i n that the first well fluid (4) is a liquid.

3. A tool (1) according to claim 1, c h a r a c t e r i z e d i n that the first well fluid (4) is a gas.

4. A tool (1) according to claim one or more of the previous claims, c h a r a c t e r i z e d i n that broken up first well fluid (4) when commingled with at least one other well fluid (8) is flowable to the surface.

5. A tool (1) according to one or more of the previous claims, c h a r a c t e r i z e d i n that the first well fluid (4) is flowing through the flow path (9) when stirred.

6. A tool (1) according to one or more of the previous claims, c h a r a c t e r i z e d i n that the first well fluid (4) is substantially stagnant when stirred.

7. A tool (1) according to one or more of the previous claims, c h a r a c t e r i z e d i n that the tool (12) is autonomous.

8. A tool (1) according to one or more of the previous claims, c h a r a c t e r i z e d i n that the stirrer (26) receives its driving energy from a turbine (22) that is positioned in the flow path (9) of the wellbore (1) and driven by a fluid flowable through the flow path (9).

9. A tool (1) according to one or more of the previous claims, c h a r a c t e r i z e d i n that driving energy to the stirrer (26) is supplied from locally stored energy.

10. A tool (1) according to one or more of the previous claims, c h a r a c t e r i z e d i n that driving energy to the stirrer (26) is supplied from an external source.

11. A tool (1) according to one or more of the previous claims, c h a r a c t e r i z e d i n that the tool (12) is installed as part of a well tubular (14) such as a production tubing (32).

12. A tool (1) according to one or more of the previous claims, c h a r a c t e r i z e d i n that tool (12) is designed to be replaceable by wellbore intervention.

13. A method for aiding transport of a first well fluid (4) from a well (3) through a flow path (9) of a wellbore (1), c h a r a c t e r i z e d i n that the method includes:

- positioning a tool (12) having a stirrer (26) that is in communication with the flow path (9) of the wellbore (1);

- letting the stirrer (26) break up the first well fluid (4) into droplets and reduce the size of first well fluid (4) droplets for commingling with at least one other well fluid (8); and

- transporting the commingled fluids (4, 8) to the surface.