WO2009123464A1

WO2009123464A1 - A valve for a production tubing, and also a production tubing for recovery of oil and gas

Info

Publication number: WO2009123464A1
Application number: PCT/NO2009/000110
Authority: WO
Inventors: Eilif H. Johannesen
Original assignee: Ior Technology As
Priority date: 2008-04-02
Filing date: 2009-03-26
Publication date: 2009-10-08
Also published as: NO20081644L

Abstract

A valve (60) for a production tubing (12) is discussed in connection with production of oil and gas arranged for automatic shutoff of fluid flow into the production tubing (12) in case of water breakthrough, where the valve comprises at least one closable flow channel for said flowing fluid. In said at least one fluid channel (64) is provided a closing and trigger mechanism (62; 162) arranged to be maintained in a retracted position by a mechanical detent (72) made of a disintegrateable material reacting with water, whereby the valve (60) at release of the closing and trigger mechanism (62; 162) is arranged to block the flowing fluid from flowing into the production tubing (12) if said fluid contains water. A production tubing with a valve is also discussed.

Description

A VALVE FOR A PRODUCTION TUBING, AND ALSO A PRODUCTION TUBING FOR RECOVERY OF OIL AND GAS

The present invention relates to a valve for production tubing for use in connection with production of oil and gas, where the valve is provided for automatic shutdown of a fluid flow into the production tubing in case of water breakthrough, where the valve comprises at least a closable flow channel for said flowing fluid. The invention also relates to a production tubing for production of oil and gas comprising at least a surrounding sand screen and at least an adjacent, surrounding inflow device provided to control and lead the fluid flow into the production tubing.

When an oil company has completed a well, the desire is to produce the oil as homogeneous and clean as possible. Thin oil zones, normally down to 5 meter, often lies on top of a water surface and under a layer of gas. Both gas blowby (from above) and water breakthrough (from below) is unwanted because the desire is to first produce as much oil as possible and thereafter produce the gas .

Water breakthrough entails that a mixture of water and oil is brought to the surface. If the water breakthrough is extensive, it means that an extensive and very costly and energy demanding separation problem in the process plant is encountered. In some fields often 80% water and 20% oil is produced and comes to the surface as a compound fluid. This compound fluid will then have to be processed to separate it into oil/water so that the oil may be utilized. At the same time it is required that the water is cleaned to separate out so much of the oil that the excess water becomes sufficiently clean to be dumped. Some places the water is injected/reinjected.

The water being cleaned here is called "produce water" . Irrespective of cleaning method will some of the oil stay mixed in the water, and dumping taking place in the Norwegian sec- tor will require acceptance from the Norwegian Pollution Control Authority. As a consequence of this process, a continuous "controlled" contamination within allowable limits takes place, so that there will always appear larger or smaller traces on the surface of the sea showing this pollution. Pro- duced water consists of formation water naturally existing in the reservoirs and water being injected for use as pressure support to expel more oil. In the course of an oil field life, twice as much contaminated water as oil is readily pumped up. Most of this water is dumped in the sea without being cleaned of environmental poison. Dumping of produced water has multiplied in recent years, and an increase is still expected. In the year 2000 more than 106 million m³ was dumped in Norwegian sector, and more than twice as much in British sector. The prognosis up to the year 2010 shows more than twice as much produced water in the Norwegian sector compared to today. This is a result of the oil companies injecting more and more water to increase the oil production when the oil fields are being emptied.

Recent research results from the Norwegian Institute of ma- rine research shows that the dumping of alkyd phenol may influence the reproduction capability of cod. The male cod is being feminised and fertilising capacity is decreased, and the female cod generates roe later than normally. This invention has thus also an environmentally benign effect.

The object of an autonomous water shutoff valve is thus to prevent water from getting into the production tubing in those parts of the production tubing that are exposed to water breakthrough. Typically a water breakthrough happens after some time in production because the oil layer giving the pressure in a given zone is reduced and thereby lets the water force its way up from below.

A completion string consists of many production pipes, each having a length of 12 meters, being screwed together. On the production tubing is installed sand filters to prevent sand from entering into the oil/production. In various places are installed expansion packers sealing against the formation it- self. The purpose is to divide the production tubing into sections so that every section may be perceived as a separate production environment, i.e. prevent multi fluid liquid and gas from penetrating from one section to another without this happening through the production tubing.

By being able to keep up the production from every part of the production string which has not been the object for water breakthrough, this will save the oil companies from enormous costs and at the same time save the environment from a large negative influence.

It is therefore an object of the present invention to produce an autonomous valve to close at water breakthrough in a production tubing.

From the publication NO 2007 2639, belonging to the present applicant, a valve for a production tubing provided for auto- matic shutdown of the fluid flow into the production tubing is described, and also a production tubing device with a sand screen, multiple flow channels and three chambers. The valve device according to NO 2007 2639 is provided for automatic shutdown of the fluid flow into a production tubing at gas blowby, as the valve device is provided to react to various fluid densities.

From the publications US 7 290 606, US 6 786 285, US 6 622 974, NO 306 127, CA 2 559 111 and US 6 423 210 are known various types of flow control devices, but where the control is provided by other means than water sensitive valve closure devices based on calcium carbide.

The present valve is provided for closing exactly where the water breakthrough arises (e.g. each 12 meter production pipe) so that clean oil may be produced in the rest of the string and in any case in the whole section possibly being the object of water breakthrough. The water breakthrough is assumed to be of a different character to gas blowby, and also more transient - i.e. that there may be a temporary gas blowby thereby coming to the surface, but where oil also may be produced afterwards . A water breakthrough on the other hand is assumed to be a permanent change of the production environment and that the water cover rises gradually so that it possibly involves parts of the production string seen both horizontally and vertically. For this reason is there according to the invention provided a valve giving permanent shut- down after it has been subjected to water throughout a non- immaterial period. The dimensioning of a detent, for example made of calcium carbide, may control the time before the valve is closed.

The shutoff may be automatic, i.e. that the valve does not necessarily have to be controlled from the surface. By using Calcium carbide as detent, a warning will be received at the surface when one or more of the valves are exposed to water. This occurs by the formation of C₂H₂ - acetylene gas, which will accompany the oil to the surface in the period until the detent is consumed and dissolved. One does not get to know which valve is closing, but this may be achieved by including a tracer (radioactive) being unique for the relevant valve or section in the carbide. If a tracer is desired, it is relatively simple to build in, but it is assumed not to have such a great significance to know where the breakthrough is, as long as it can be stopped automatically.

The above mentioned object is achieved by a valve as stated in the independent claim 1, by in the said at least one flow channel is arranged a closing and trigger mechanism provided to be maintained in a retracted position by a mechanical detent formed in a disintegrateable material reacting with wa- ter, whereby the valve at release of the closure and trigger mechanism is arranged to close for the fluid flowing into the production tubing if said fluid contains water.

Alternative embodiments are stated in the dependent claims 2 - 8.

The mechanical detent is preferably made from calcium carbide.

The closing and trigger mechanism may comprise a ball released by disintegration of the mechanical detent, and the channel end of the flow channel may have a tapering diameter, whereby the ball is driven set in the channel end closing against further flow. The closing and trigger mechanism may further be connected to a detent which, when the closing and trigger mechanism is in the retracted position, closes a second flow channel.

The closing mechanism may alternatively be spring loaded and designed as a movable slide with an extending part which when influenced by said spring loading is arranged to be freed to be introduce into and close the at least one flow channel when the mechanical detent disintegrates. The slide may in addition to the extending part comprise a second part ar- ranged to close a second flow channel when the closing mechanism is in the retracted position.

When the closing and trigger mechanism closes the first flow channel, the fluid flow is lead to a second flow channel, wherein a movable ball may be released and moved in the chan- nel, for closing the channel adjacent a junction to the first flow channel and the second flow channel.

The channel end may comprise a seat for receiving the ball, or the channel end may be designed with a tapering diameter, for production of said closure.

The above object is achieved also with a production tubing for production of oil and gas as given in the independent claim 9, in that the inlet device comprises a number of chambers, where flow channels are running between the chambers, as a prechamber is arranged for receiving flowing fluid from the sand screen, an intermediate valve chamber is arranged for receiving flowing fluid from the prechamber and for automatic closing for water further into the production tubing in case of a water breakthrough, where the valve chamber comprises a number of water shutoff valves as stated above, and a post chamber arranged to receive flowing fluid from the valve chamber and to direct and lead fluid flow into the production tubing.

Alternative embodiments are characterised by the dependent claims 10 - 13. In a further particularly advantageous embodiment the valve chamber also comprises a number of gas closure valves connected in series with said water shutoff valves.

The valve chamber may comprise a number of support rings at- tached to the production tubing, where a number of said valves are provided spaced on the external side of the production tubing between said support rings and a surrounding sleeve .

The fluid flow enters through openings in the first support ring and thereafter through openings in a second support ring to the post chamber.

The prechamber may further comprise an acid plug provided to open for gas production after all the oil is produced.

The invention will now be described more detailed by means of the accompanying drawings, wherein:

Figure 1 shows a principle sketch of a completion string;

Figure 2 shows a production tubing according to the invention;

Figure 3 shows an inflow device to the production tubing;

Figure 4 shows parts of a production tubing with a number of water shutoff valves according to the invention;

Figures 5, 6 and 7 show principle sketches in section of a water shutoff valve according to the invention; and

Figures 8, 9 and 10 show principle sketches in section of a preferred water shutoff valve according to the invention. Figure 1 shows a completion string in a formation for production of oil, consisting of production pipes 12 screwed together. On the production pipes 12 are mounted sand filters 14 to prevent sand entering the oil. In certain places are installed expansion packers 15 which divides the drill string into sections such that each section is like a separate production environment, i.e. that gas and/or water shall not be able to penetrate from one section to the next unless this is done through the production tubing.

In figure 2 is shown a production tubing 12 with an inflow device 10. Adjacent the inflow device 10 is positioned a sand filter 14 around the production tubing. The inflow device 10 may comprise a so-called "ICD" (Inflow Control Device) of a per se known sort and one or more gas shutoff valves, water shutoff valves, kill filters or openings, acid plug 50 and also a check valve 52 to open for killing from the formation.

The inflow device 10 may, as shown in figure 3, be constructed with three chambers 20, 22, 24. Each of the chambers are separated by completely tight sections such that multi liquid flow basically only may take place through the flow channels 20a, 22a, 22b in the device 10. It might however be sufficient having tightness toward one of the support rings. The intention is only to ascertain that the flow must go through the valve to come to or from a chamber. The flow di- rection is from prechamber 20 to valve chamber 22 and to post chamber 24. The liquid enters the prechamber 20 from the underside of the sand screen 14 (see figure 2) and flows into the annulus between the sand screen 14 and the production tubing 12.

Subsequently the liquid flows through openings in a first support ring (not shown) and alternatively into a gas shutoff valve. The gas shutoff valve may be provided between the sup- port ring and an external sleeve. Subsequently the flow preferably flows out on the sides in some small intermediate chambers 26a, 26b and then through openings 22a, 22b in the second support ring and to the post chamber 24. In the post chamber 24 shall the fluid only be lead into the production tubing 12, for example through the kill filter. A standard channel-ICD may if desired be installed in front.

An acid plug 50 (see figure 2) allowing opening for gas production after all oil is produced may be placed in the pre- chamber 20. An acid pill may open this by running intervention in the production tubing. If an acid plug cannot be used due to restrictions in branch crossings or branch guide, a one-way valve 52 available in the market may be used. Alternatively a new plug, which is unhooked following a given overpressure from the inside of the production tubing, may be designed. None of the known solutions introduced have solved this problem. Several have also poor solutions to kill filter. It is necessary to be able to kill the well both against the inside of the production string and against the forma- tion. The present valve will allow both. The valve does allow liquid to flow both ways and should in theory make a check valve superfluous .

Referring to figure 4 a number of water shutoff valves 60 around the production tubing 12 may be utilised. The valve may be connected in series with a valve having an ICD-action or a traditional helix shaped ICD (existing technology) .

The figures 5, 6 and 7 show an alternative embodiment of a water shutdown valve 60 according to the invention. Basically the valve 60 comprises at least one flow channel 64 for the flowing liquid. Even if the expression liquid is used, it is to be understood that this also covers fluid which is a mixture of liquid and gas. In the at least one flow channel 64 is provided a closing mechanism 62, for example in the form of a spring-loaded slide. The closing mechanism 62 is maintained in the first place in a retracted position by means of a mechanical detent 72, for example provided in a recess in the flow channel 64. The detent 72 is preferably made of the material calcium carbide. This material does not react with oil, but reacts vigorously with water.

The chemical reaction is: CaC₂ (calcium carbide) + 2H₂O (water) = Ca(OH)₂ (slaked lime) + C₂H₂ (ccetylene) . Carbide is in shape and colour like a greyish stone and has thus a good supporting capacity making it suited for a mechanical detent. The melting point is also high. If the carbide is subjected to water over time, it will disintegrate by gradually being dissolved and finally be completely dissolved so that it no longer stops said slide 62, making it close the flow channel 64. This entails that the solution will be static and close permanently once it closes.

Use of carbide is known within the oil industry and is used as an additive to water based mud where one measures how long time it takes from the substance is added until acetylene gas is received on deck. Based on this time, one may measure the success of a cementing job. Carbide can on the other hand not be used with oil-based mud since it does not react with oil. This makes thus carbide the ideal material both as detent and signal transmitter for water penetration.

In a further embodiment the valve may have two flow channels, namely the first flow channel 64 and a second flow channel 66. The slide will during normal production block the secondary channel 66 and prevents at the same time a ball 68 pre- sent in the secondary channel 66 from moving in toward a valve seat 70. At water breakthrough the mechanical detent disintegrates and blocks the first channel 64, whereupon liq- uid will try to flow into the second flow channel 66. The movement of the slide 62 releases the ball 68, and the flow moves the ball 68 toward and to the valve seat 70 so that further liquid flow is rendered not possible. The advantage of this solution is that a permanent closure is achieved independently of the slide opening in the first channel 64 as the liquid pressure provides for the ball being forced against the valve seat 70 closing it against further flow of any liquid. '

Figures 8, 9 and 10 show as mentioned the principle for a preferred embodiment of a water shutoff valve. The valve is in many ways built in the same way as explained above, and it has at least one flow channel 64 with a closing and trigger mechanism 162. The closing and trigger mechanism 162 coin- prises in this case however a ball 168 being maintained in a retracted position in a recess in the channel 64 by an equivalent mechanical detent 72 made of calcium carbide as discussed above. When the detent 72 disintegrates on being exposed to water, the ball 168 is forced into the channel 64 by means of a spring mechanism 80 or an in other ways influ- enceable device, whereby the ball will follow the fluid flow into the channel 64. By forming the channel end 64a of the channel 64 with tapering diameter, the ball 168 will get stuck and block the fluid flow. Advantages in such a solution are among other things that one is not dependent on a movable slide. If the ball for some reason should experience wear, it will penetrate deeper into the tapering channel end 64a. If desired the ball may also be freed by means of a high backpressure .

The solution shown in figures 8, 9 and 10 may also comprise a secondary flow channel 66 as discussed above. A ball 68 may in a corresponding way be held on Che spot in the secondary channel 66 by a block 82, such as a spring loaded block, whereby the block 82 is released when the spring mechanism 80 is released, so that the ball in an equivalent manner is driven toward the channel end 66a. The channel end 66a may be provided with a valve seat 70 (see for example figure 7) as discussed above, or be designed with a tapering diameter so that the ball 68 gets stuck and blocks any further through flow of any liquid.

By "channel end" is meant such as shown in the figures, and not necessarily at termination of the channel.

As an alternative to a ball in the flow channel 66, the block may be replaced by a powerful jet built by a pressure drop being able to bring the water to freeze. Sometimes plugs come into being because one produces too fast so that the water freezes and blocks the screens. This is normally undesirable, but in case of a water breakthrough one may desire to make a dynamic shutoff being solved by the water freezing - thaws - freezes etc. in a cycle.

The flow channel 64 may be marginally larger than the flow channel 66. Both channels may as mentioned be preferably a little narrower at the outlet (taper) . It is presumably not necessary to make a valve where the channels are locked to the previous ring. They may only be open and take the flow wherever it comes from. The challenge is to avoid that the pipes/channels are blocked so that the ball cannot be able to move where it is supposed. There may therefore be a seat 74 at the inlet to the channel 66 so that the ball 68 seals and prevents something from entering and "cementing" the ball. On the other hand there might be sediments (from the branch crossing and towards the ball) and ideally it would be sealed until the ball was to go through. The water shutoff valve is basically only a through flow valve without any damping effect on the flow through it. The valve may thus have one or more flow channels in the open position. The channels are dimensioned according to desired ca- pacity and based on the dimension of the valve in front. The oil goes through a primary channel (production mode) , through a branch crossing and in through a seat before passing into the post chamber with kill filter.

The ball may be made either of a silicon-based material or it may be made of metal. The seat will be made either of metal or of metal with polymer cladding to ensure a good seal and durability. It is assumed that such a ball with the desired properties is already available in the market.

The present valve is characterised in that is in a fairly flat embodiment so that it may be placed exterior to the production tubing and thereby carry on a technology leading the oil along the production tubing before it is allowed unto the tubing through longitudinal slots - the so-called kill filter. The number of valves may be the same as for gas shutoff on the same production tubing. Without the gas shutoff valve there will likely be four valves evenly distributed around the tubing .

The water will therefore take another route or be under control. It may advance to another valve within the same zonally divided section so that this also closes.

Use of zone isolation (expanding packings) will prevent the water from flowing outside the section so that oil may be produced from all the valves that are exposed to oil only.

As one cannot know beforehand if a gas blowby, a water break- through or both are going to happen, a valve covering both conditions will be the ideal and complete solution. If one can achieve support for both, this will exclude all isolated solutions. One cannot know where on the production tubing one or the other may happen and thus distribute water or gas shutoff valves based on closing for gas or water (even if the probability varies somewhat in relation to the distance to gas/water, but also in relation to varying permeability of the sand in the length of the string) .

A combination of gas shutoff valves and water shutoff valves for example connected in series will solve both gas shutoff and water shutoff. The water shutoff valve may be positioned after the gas shutoff valve with ICD-action.

Summing up will such a combination solve the following:

An autonomic gas shutoff valve - closes dynamically at gas blowby.

A progressive ICD-effect - distributes the differential pressure evenly over the production tubing.

An autonomic water shutoff valve - closes permanently at prolonged water breakthrough.

The autonomic gas shutoff valve has a progressive ICD-action. It acts not only as a damper along the whole of the production tubing - it will choke mostly where there is largest local production such that this in itself takes part in counteracting blowby/breakthrough of both gas and water.

Claims

P a t e n t c l a i m s

1. A valve (60) for a production tubing (12) in connection with production of oil and gas, arranged for automatic shutoff of fluid flow into the production tubing (12) in case of water breakthrough, where the valve comprises at least one closable flow channel for said flowing fluid, c h a r a c t e r i s e d i n that in said at least one flow channel (64) is provided a closing and trigger mechanism (62; 162) ar- ranged to be maintained in retracted position by a mechanical detent (72) made of a disintegrate able material which reacts with water, whereby the valve (69) at release of the closing and trigger mechanism (62; 162) is arranged to block the flowing fluid in to the production tubing (12) if said fluid contains water.

2. A valve (60) in accordance with claim 1, c h a r a c t e r i s e d i n that the mechanical detent (72) is made of calcium carbide.

3. A valve (60) in accordance with claim 1 or 2 , c h a r a c t e r i s e d i n that the closing and trigger mechanism (162) comprises a ball (168) being released at disintegration of the mechanical detent (72) , and that the channel end (64a) of the flow chan- nel has tapering diameter, whereby the ball (168) is driven fixedly into the channel end (64a) and blocking further flow.

4. A valve (60) in accordance with claim 3, c h a r a c t e r i s e d i n that the closing and trigger mechanism (162) is connected to a detent (82) which, when the closing and trigger mechanism (162) is in the retracted position, closes a second flow channel (66) .

5. A valve (60) in accordance with claim 1 or 2 , c h a r a c t e r i s e d i n that the closing mecha- nism (61) is spring loaded and produced as a movable slide with an extending part (62a) which under influence of said spring load is arranged to be freed to be let into and block the at least one flow channel (64) , when the mechanical detent (72) disintegrates.

6. A valve (60) in accordance with claim 5, c h a r a c t e r i s e d i n that the slide in addition to the extending part (62a) comprises a second part (62b) arranged to close a second flow channel (66) when the closing mechanism (62) is in the retracted position.

7. A valve (60) in accordance with claim 4 or 6 , c h a r a c t e r i s e d i n that when the closing and trigger mechanism (62; 162) closes the first flow channel (64) , the fluid flow is lead to a second flow channel (66) , wherein a movable ball (68) is freed and moved in the channel (66) for shutting off the channel (66) adjacent a junction point with the first flow channel (64) and the second flow channel (66) .

8. A valve (60) in accordance with claim 7, c h a r a c t e r i s e d i n that the channel end (66a) com- prises a seat (70) for receiving the ball, or that the channel end (66a) is formed with tapering diameter, for generating said shut off.

9. A production tubing (12) for production of oil and gas, comprising at least a surrounding sand screen (14) and at least one adjacent surrounding inflow device (10) provided to control and lead a fluid flow into the production tubing, c h a r a c t e r i s e d i n that the inflow device (10) comprises a number of chambers (20, 22, 24), where flow channels (20a, 22a, 22b) run between the chambers, as a prechamber (20) is provided for receiving flowing fluid from the sand screen (14) , an intermediate chamber (22) is provided for receiving flowing fluid from the prechamber (20) and for automatic blocking of water further into the production tubing (12) in case of water breakthrough, where the intermediate chamber (22) comprises a number of water shutoff valves (60) as stated in one or more of the claims 1-8, and a post chamber (24) provided to receive flowing fluid from the valve chamber (22) and to control and lead fluid flow into the production tubing (12) .

10. A production tubing in accordance with claim 9, c h a r a c t e r i s e d i n that the valve chamber (22) further comprises a number of gas shutoff valves connected in series with said water shutoff valves (60) .

11. A production tubing in accordance with claim 10, c h a r a c t e r i s e d i n that the valve chamber (22) comprises a number of support rings attached to the production tubing, where a number of said valves (60) is arranged spaced apart on the external side of the production tubing (12) between said support rings and a surrounding sleeve.

12. A production tubing in accordance with claim 11, c h a r a c t e r i s e d i n that the flow enters through openings in the first support ring and thereafter through openings in the second support ring to the post chamber (24) .

13. A production tubing in accordance with claim 9, c h a r a c t e r i s e d i n that the prechamber comprises an acid plug (50) arranged to open for production of gas after all the oil is produced.