A GAS LIFT SYSTEM AND A GAS LIFT METHOD
The present invention relates to a gas lift system (1) arranged in a well (65) having a top (10) and comprising a well fluid (11), the gas lift system comprising a casing (61) arranged in the borehole defining a surrounding annulus (62), an opening (86) in the casing, and a pumping unit (12) for pumping gas (8) into the annulus, wherein the gas lift system further comprises a downhole tool (14) having a first end (15) nearest the top of the well and a second end (16), the down-hole tool comprising a pump section (2) comprising a housing (20) comprising a chamber (201) having an axial extension (17), a plunger (23) sliding in the chamber and dividing the chamber into a first compartment (203) and a second compartment (202), a plunger rod (26) connected with the plunger, a chamber inlet channel (27) and a chamber outlet channel (21), the inlet channel and the outlet channel being in fluid communication with the second compartment, a sealing element (29) for isolating a first part (66) of the casing from a second part (67) of the casing, the first part and the inlet channel being in fluid communication with the opening, a one-way valve (24) arranged in the inlet channel to allow fluid to flow into the chamber, and a one-way valve (22) arranged in the outlet channel to allow fluid to flow out of the chamber. The invention also relates to a gas lift method.
The present invention relates to a gas lift system arranged in a well having a top and comprising a well fluid, the gas lift system comprising a casing arranged in the borehole defining a surrounding annulus, an opening in the casing, and a pumping unit for pumping gas into the annulus. The invention also relates to a gas lift method.
BACKGROUND ARTGas lifting of the fluid column in a well to overcome a hydro-static pressure and drive hydrocarbons to surface is typically performed by means of side pockets arranged as part of the production casing. The annulus created between the production casing and the intermediate casing is pressurised with gas which, at certain pressures, is allowed to flow in through a certain side pocket gas lift valve. Pressurised gas is able to flow down the annulus until a certain point, at which point the last side pocket is normally arranged. At present, it is impossible to pressurise the gas to flow past this point.
SUMMARY OF THE INVENTIONIt is an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to provide an improved gas lift system which is able to provide gas lift further down the well beyond the point which can be reached by known systems having side pocket gas lift valves.
The above objects, together with numerous other objects, advantages and features, which will become evident from the below description, are accomplished by a solution in accordance with the present invention by a gas lift system arranged in a well having a top and comprising a well fluid, the gas lift system comprising:
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- a casing arranged in the borehole defining a surrounding annulus,
- an opening in the casing, and
- a pumping unit for pumping gas into the annulus,
wherein the gas lift system further comprises a downhole tool having a first end nearest the top of the well and a second end, the downhole tool comprising a pump section comprising: - a housing comprising a chamber having an axial extension,
- a plunger sliding in the chamber and dividing the chamber into a first compartment and a second compartment,
- a plunger rod connected with the plunger,
- a chamber inlet channel and a chamber outlet channel, the inlet channel and the outlet channel being in fluid communication with the second compartment,
- a sealing element for isolating a first part of the casing from a second part of the casing, the first part and the inlet channel being in fluid communication with the opening,
- a one-way valve arranged in the inlet channel to allow fluid to flow into the chamber, and
- a one-way valve arranged in the outlet channel to allow fluid to flow out of the chamber.
By having a suction tool within the casing, the gas can enter further down the well, and the system is thus capable of providing gas lift on more fluid than in the known systems. The present system is thus capable of providing gas lift of wells which cannot be gas lifted by the known systems.
Furthermore, the downhole system may also be submerged into deep water wells to decrease the pressure in these wells so that hydrate does not form in the well head or blowout preventer. Hydrate is formed when having low temperature and high pressure and a certain amount of water in the well fluid.
Also, at least part of the inlet channel may extend radially from an outer surface of the housing towards the chamber.
Moreover, the plunger may comprise a protrusion protruding from a first plunger face of the plunger facing the inlet channel and/or the outlet channel.
The protrusion may be arranged, extending from an end face of the chamber nearest the second end of the tool.
In addition, the sealing element may be an annular seal for sealing around the opening.
Furthermore, a one-way valve may be arranged in the opening to allow fluid to flow into the casing.
The sealing element may also circumferent the housing and may be adapted for sealing against the casing.
The gas lift system according to the invention may further comprise a second sealing element circumferenting the housing and adapted for sealing against the casing, thereby isolating a part of the first part of the casing opposite the opening.
Moreover, an inlet of the inlet channel may be arranged substantially opposite the opening along the axial extension.
Additionally, the inlet of the inlet channel may be arranged substantially opposite the opening along a circumference of the housing.
Further, an outlet of the outlet channel may be arranged closer to the first end of the tool than the inlet channel.
In addition, an outlet of the outlet channel may be arranged closer to the first end of the tool than the inlet.
The gas lift system according to any of the invention may further comprise a linear actuator for providing a reciprocating movement of the plunger.
The linear actuator described above may comprise:
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- a tubular stroker cylinder comprising one or more piston housings,
- one or more piston elements slidably disposed in the piston housing to divide the piston housing into a first chamber and a second chamber,
- a stroker shaft operably connected to the piston element for connecting with a plunger rod to provide reciprocation of the plunger,
- a pump for alternately supplying hydraulic fluid under pressure to the first chamber and the second chamber of the piston housing to reciprocate the piston element in the piston housing, and
- an electrical motor for driving the pump.
Furthermore, the sealing element may be a chevron seal.
Also, the first end of the tool may be connected with a wireline.
Moreover, the opening may comprise two successive one-way valves.
The casing may also comprise a plurality of openings spaced apart along the casing.
Additionally, the sealing element may be inflatable or expandable.
The tool may comprise a driving unit for propelling the tool forward in the well.
In addition, the tool may comprise a tool section comprising a drilling bit for drilling or milling an opening in the casing.
Further, the casing may comprise at least one side pocket, and the side pocket may be arranged closer to the top than the opening.
The casing may have a substantially vertical part and a substantially horizontal part and a toe part connecting the vertical part and the horizontal part, and the opening may be arranged in the toe part or the horizontal part.
A bore may extend from the second end of the tool to an equalising valve arranged in the outlet channel to connect the bore and part of the outlet channel.
The present invention also relates to a gas lift method comprising the following steps:
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- inserting the gas lift system according to any of the preceding claims into the borehole,
- arranging the inlet channel opposite the opening,
- isolating the first part of the casing from the second part of the casing by means of a sealing element, so that the first part is in fluid communication with the opening and the inlet channel is in fluid communication with the opening,
- activating the pump unit to pump gas into the annulus,
- moving the plunger rod in a reciprocating movement, and
- sucking fluid from the first part of the casing, so that the gas in the fluid in the annulus is sucked towards the opening and into the first part and further into the first compartment and out through the outlet channel.
The gas lift method described above may further comprise the step of isolating a part of the first part of the casing opposite the opening to create a suction area between the casing and the tool opposite the opening.
The method may further comprise the step of making the opening in the casing.
Further, the gas lift method may further comprise the step of drilling an opening in the casing.
Also, the method may comprise the step of releasing the tool from the casing.
Moreover, the method may comprise the step of making a second opening in the casing.
Additionally, the method may comprise the step of moving the tool further away from the top of the well to be opposite a second opening and engaging the casing by means of the sealing element.
Finally, the method may comprise the step of sucking fluid in through the second opening.
The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which for the purpose of illustration show some non-limiting embodiments and in which
All the figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested.
DETAILED DESCRIPTION OF THE INVENTIONWhen using the gas lift system shown in
Furthermore, the downhole system can also be submerged into deep water wells to decrease the pressure in these wells so that hydrate does not form in the well head or blowout preventer. Hydrate is formed when having low temperature and high pressure and a certain amount of water in the well fluid.
As shown in
Due to the fact that in known pumping systems, gas can only be pumped to a certain point down the annulus, gas lift can only be provided down to this point, which in some wells results in the well not being capable of producing again. By inserting a tool opposite the opening arranged further down the well than the certain point, the tool aids the gas-containing fluid in the annulus further down beyond the certain point by sucking fluid into the chamber just opposite the opening. It is thus possible to provide gas lift further beyond the certain point, which is needed when the known gas lift systems are not able to overcome the hydro-static pressure and drive the hydrocarbons to surface through side pocket gas lift mandrels. Furthermore, by inserting the tool into the casing opposite the opening, side pocket gas lift mandrels are no longer needed in order to provide gas lift. When having side pockets installed in the casing, the platform at the sea bed or surface has to be made sufficiently larger, because the cross-sectional diameter of the casing at the side pockets is substantially increased. The making of such platforms with side pockets is substantially more costly than casings without the side pockets. Therefore, the present gas lift system also results in wells no longer having to be made with side pockets initially, and thus the costs involved in completing a well are substantially reduced.
As shown in
The pump section shown in
The tool 14 further comprises a linear actuator 40 arranged in association with the housing 20, as shown in
Referring to the embodiment of a pump section 2 shown in
Details about the design of the linear actuator are shown in
In another embodiment, the linear actuator may comprise an electric linear motor 51 driving the stroker shaft as shown in
In order to increase the amount of gas sucked into the casing, the inlet 52 of the inlet channel is arranged substantially opposite the opening along the axial extension as shown in
As shown in
In
The sealing elements in
As can be seen in
The casing comprises a plurality of openings 86a, 86b, 86c spaced apart along the casing as shown in
As can be seen in
In
In
In
Further, as described above, the design of the pump section allows well fluid to flow from the inlet 52 towards the outlet 53 regardless of the position of the plunger 23. The tool 14 may thus be arranged in the well downhole permanently or for longer periods of time, operating based on the actual demand for boosting the flow in the well. If, for some reason, the flow in the well suddenly drops, the tool may be activated to boost the flow until the well is once again able to run by itself. The tool may be activated either automatically based on a measured pressure in the well or by a signal received from an operator through the wireline. The measured differential pressure across the set sealing element may thus be used to control the operation of the pumping action of the tool by continuously activating and deactivating the pumping action to boost the flow in the well by providing gas lift.
The tool 14 of the gas lift system 1 is thus lowered into the casing and arranged so that the inlet channel 27 is opposite the opening, then the first part 66 of the casing is isolated from the second part 67 of the casing by means of a sealing element 29, so that the first part and the inlet channel are in fluid communication with the opening. Subsequently, the pump unit is activated to pump gas into the annulus, and the plunger rod is moved in a reciprocating movement in order to suck fluid from the first part of the casing, so that the gas in the fluid in the annulus is sucked towards the opening and into the first part and further into the first compartment and out through the outlet channel.
When having two sealing elements 29, 35, a part of the first part of the casing opposite the opening can be isolated to create a suction area between the casing and the tool opposite the opening. The tool may further comprise means for making the opening in the casing downhole.
In the event that the gas lift provided through the first opening is not sufficient for well fluid to start flowing by the pressure present in the reservoir, the tool releases itself from the casing by deflating or unexpanding the sealing elements and subsequently moves further down the well and makes a second opening in the casing and initiates a sucking action opposite the second opening and provides gas lift further down the well from the first opening. Should the gas lift provided through the second opening not be sufficient, the process of deactivating the sealing elements and making an opening further down the well is repeated. Thus, the tool may comprise a tool section 94 comprising a drilling bit 97 for providing such opening in the casing as shown in
The linear actuator may be a stroking tool or stroker tool is a tool providing an axial force. The stroking tool comprises an electrical motor for driving a pump. The pump pumps fluid into a piston housing to move a piston acting therein. The piston is arranged on the stroker shaft. The pump may pump fluid into the piston housing on one side and simultaneously suck fluid out on the other side of the piston.
By fluid or well fluid is meant any kind of fluid that may be present in oil or gas wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc. By gas is meant any kind of gas composition present in a well, completion, or open hole, and by oil is meant any kind of oil composition, such as crude oil, an oil- containing fluid, etc. Gas, oil, and water fluids may thus all comprise other elements or substances than gas, oil, and/or water, respectively.
By a casing is meant any kind of pipe, tubing, tubular, liner, string etc. used downhole in relation to oil or natural gas production.
In the event that the tool is not submergible all the way into the casing, a downhole tractor can be used to push the tool all the way into position in the well. The downhole tractor may have projectable arms having wheels, wherein the wheels contact the inner surface of the casing for propelling the tractor and the tool forward in the casing. A downhole tractor is any kind of driving tool capable of pushing or pulling tools in a well downhole, such as a Well Tractor®.
Although the invention has been described in the above in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.
Claims
1. A gas lift system arranged in a well having a top and comprising a well fluid, the gas lift system comprising: wherein the gas lift system further comprises a downhole tool having a first end nearest the top of the well and a second end, the downhole tool comprising a pump section comprising:
- a casing arranged in the borehole defining a surrounding annulus,
- an opening in the casing, and
- a pumping unit for pumping gas into the annulus,
- a housing comprising a chamber having an axial extension,
- a plunger sliding in the chamber and dividing the chamber into a first compartment and a second compartment,
- a plunger rod connected with the plunger,
- a chamber inlet channel and a chamber outlet channel, the inlet channel and the outlet channel being in fluid communication with the second compartment,
- a sealing element for isolating a first part of the casing from a second part of the casing, the first part and the inlet channel being in fluid communication with the opening,
- a one-way valve arranged in the inlet channel to allow fluid to flow into the chamber, and
- a one-way valve arranged in the outlet channel to allow fluid to flow out of the chamber.
2. A gas lift system according to claim 1, wherein at least part of the inlet channel extends radially from an outer surface of the housing towards the chamber.
3. A gas lift system according to claim 1, wherein the plunger comprises a protrusion protruding from a first plunger face of the plunger facing the inlet channel and/or the outlet channel.
4. A gas lift system according to claim 1, wherein the sealing element is an annular seal for sealing around the opening.
5. A gas lift system according to claim 1, wherein a one-way valve is arranged in the opening to allow fluid to flow into the casing.
6. A gas lift system according to claim 1, wherein the sealing element circumferents the housing and is adapted for sealing against the casing.
7. A gas lift system according to claim 1, further comprising a second sealing element circumferenting the housing and adapted for sealing against the casing, thereby isolating a part of the first part of the casing opposite the opening.
8. A gas lift system according to any claim 1, wherein an inlet of the inlet channel is arranged substantially opposite the opening along the axial extension.
9. A gas lift system according to claim 1, wherein an outlet of the outlet channel is arranged closer to the first end of the tool than the inlet channel.
10. A gas lift system according to claim 1, further comprising a linear actuator for providing a reciprocating movement of the plunger.
11. A gas lift system according to claim 1, wherein the tool comprises a driving unit for propelling the tool forward in the well.
12. A gas lift system according to claim 1, wherein the tool comprises a tool section comprising a drilling bit for drilling or milling an opening in the casing.
13. A gas lift system according to claim 1, wherein the casing comprises at least one side pocket, and the side pocket is arranged closer to the top than the opening.
14. A gas lift method comprising the following steps:
- inserting the gas lift system according to claim 1 into the borehole,
- arranging the inlet channel opposite the opening,
- isolating the first part of the casing from the second part of the casing by means of the sealing element, so that the first part is in fluid communication with the opening and the inlet channel is in fluid communication with the opening,
- activating the pump unit to pump gas into the annulus,
- moving the plunger rod in a reciprocating movement, and
- sucking fluid from the first part of the casing, so that the gas in the fluid in the annulus is sucked towards the opening and into the first part and further into the first compartment and out through the outlet channel.
15. A gas lift method according to claim 14, further comprising the step of isolating a part of the first part of the casing opposite the opening to create a suction area between the casing and the tool opposite the opening.
16. A gas lift method according to claim 14, further comprising the step of drilling an opening in the casing.
Type: Application
Filed: Jun 25, 2014
Publication Date: Jun 2, 2016
Inventor: Ricardo Reves VASQUES (Allerød)
Application Number: 14/899,282