Ice Preventing System and Method for a Gas Well

Abstract

An ice preventing system for a flow passage of a well or pipe line includes a fluid tank holding an ice prohibiting fluid and a pressure inducer positioned in the flow passage. The fluid tank is fluidically connected to the flow passage at an upstream location from the pressure inducer by an inlet pressure line. And the fluid tank is fluidically connected to the flow passage at a downstream location from the pressure inducer by a fluid injection line. A normally closed valve is disposed across the fluid injection line that is opened by a pressure differential across the pressure induce by ice accumulation in the flow passage, thereby allowing injection of the ice prohibiting fluid into the flow passage from the tank. Once the pressure differential lowers by removing the ice accumulation, the valve once again closes, and fluid injection stops.

Description

FIELD OF THE INVENTION

[0001] The present invention relates generally to ice prevention in well and pipeline systems, and more particularly, relating to an ice preventing system that operates without electricity to selective inject an ice prohibiting fluid into a well or pipeline system.

BACKGROUND OF THE INVENTION

[0002] Ice hydrate formation in gas wells is problematic because it can damage the well and form a blockage that plugs the well, which can severely disrupt or even prevent fluid production entirely. It is common to inject liquid methanol into a well to lower the freezing point at which ice hydrate forms in order to prevent ice formation and to remove any ice accumulation from the well.

[0003] Drip-feed systems are conventionally used to inject liquid methanol into low pressure wells. Typically, a drip-feed system includes a large storage tank that is located near the wellhead. The storage tank contains a supply of liquid methanol and the tank is operatively connected to the wellhead to allow the methanol to continuously drip into the wellhead under the force of gravity. While the drip-feed system is capable of preventing ice formation and removing ice accumulation, it has several inherent problems. For one, the drip-feed system is primarily a passive system and once started, methanol is continuously injected into the well until an operator returns to the well to turn the system off. The problem with this is that methanol is injected regardless of whether the methanol it is need to prevent ice formation, resulting in significant and unnecessary waste and costs.

[0004] Forced liquid methanol injection systems are alternatives to drip-feed systems. But forced injection systems require expensive pumps and controls, and also require electricity to operate. Consequently, forced liquid injection systems are not always a desirable alternative to drip-feed systems.

[0005] Accordingly there is a desire for an alternative ice preventing system that overcomes the problems with existing drip-feed systems and that does not require expensive equipment and electricity to operate.

SUMMARY OF THE INVENTION

[0006] Embodiments of the present invention provide an ice preventing system for wells and methods of preventing ice in wells using the same. Broadly, the ice preventing system of the invention is a passive system that does not require electricity to operate and which operates to selectively inject an ice prohibiting liquid into a well or pipeline only during periods were injection is required.

[0007] In general, in one aspect, an ice preventing system for wells is provided. The ice preventing system includes a tank containing a quantity of ice prohibiting fluid that is fluidically connected to the well or pipeline by an inlet pressure line and a fluid injection line. The system operates to inject ice prohibiting fluid from the tank and into the flow passage when a pressure differential is established in the flow passage that is sufficiently high to open a one-way valve disposed on the fluid injection line.

[0008] In general, in one aspect, an ice preventing system for wells the ice preventing system includes tank a containing a quantity of ice prohibiting fluid and a pressure inducer disposed across a flow passage of a well. An inlet pressure line is connects the tank in fluid communication with the flow passage of the well at a position downhole of the pressure inducer. An injector line connects the tank in fluid communication with the flow passage of the well at a position uphole of the pressure inducer. And a check valve is disposed across the injector line and is normally biased to prevent the discharge of the ice prohibiting fluid from the injector line and into the flow passage.

[0009] There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated.

[0010] Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting.

[0011] As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

[0012] For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The following drawings illustrate by way of example and are included to provide further understanding of the invention for the purpose of illustrative discussion of the embodiments of the invention. No attempt is made to show structural details of the embodiments in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Identical reference numerals do not necessarily indicate an identical structure. Rather, the same reference numeral may be used to indicate a similar feature of a feature with similar functionality. In the drawings:

[0014] FIG. 1 is a diagrammatic view of an ice preventing system constructed in accordance with the principles of an embodiment of the present invention, and in use in connection with a well;

[0015] FIG. 2 is an ice preventing system constructed in accordance with the principles of an embodiment of the present invention, showing the system in a first operating state where ice prohibiting fluid is not injected to a well;

[0016] FIG. 3 is an ice preventing system constructed in accordance with the principles of an embodiment of the present invention, showing the system in a second operating state where ice prohibiting fluid is injected to a well; and

[0017] FIG. 4 is a schematic view of a one-way valve of an ice preventing system constructed in accordance with the principles of an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0018] With reference now to the drawings, FIGS. 1-4 schematically illustrates an ice preventing system 10 constructed in accordance with an embodiment of the present invention. System 10 is shown in use with a representatively illustrated well having a wellhead 12. While system 10 is shown in connection with the represented wellhead 12, the system is not limited to the particular configuration of the wellhead. It is also contemplated that system 10 could be used in connection with other well configurations as well as pipelines that have fluid flow passages that are prone to icing.

[0019] System 10 includes a pressure inducer 14 that is positioned within a fluid flow passage 16 of the wellhead 12. As representatively illustrated, pressure inducer 14 is a flat plate that is centrally disposed within flow passage 16 and extends horizontally across the flow passage. While the pressure inducer 14 is illustrated here as a flat plate, the pressure inducer should not be limited to such a configuration. The purpose of pressure inducer 14 is to create a pressure differential in the flow passage 16 when ice 18 accumulates along the walls of the flow passage. Accordingly, pressure inducer 14 could have many different configurations while maintaining this critical function of system 10.

[0020] System 10 further includes a fluid vessel or tank 20 that holds a quantity of an ice prohibiting liquid 22 for injection into the wellhead 12 by system 10. In a particular embodiment, the ice prohibiting liquid 22 is liquid methanol or a mixture containing liquid methanol as a constituent part. When tank 20 contains the ice prohibiting liquid 22 the tank includes an upper void space 24 containing air and a lower liquid space 26 containing the ice prohibiting liquid.

[0021] An inlet pressure line 24 is connected at one end to the tank 20 and is connected at its opposite end to the wellhead 12. More specifically, the inlet pressure line 24 establishes a fluidic communication between the void space 24 of the tank 20 and the flow passage 16 of the wellhead 12 at a position downhole (upstream the direction of fluid flow in the flow passage) from the pressure inducer 14.

[0022] An injector line 28 is connected at one end to the tank 20 and is connected at its opposite end to the wellhead 12 to deliver ice prohibiting liquid 22 from the tank to the flow passage. More specifically, the injector line 28 establishes a fluidic communication between the liquid space 26 of tank 20 and the flow passage 16 of the wellhead 12 at a position uphole (downstream) of the pressure inducer 14. While only a single injector line 28 is illustrated here, multiple injector lines could be employed in order to distribute the ice prohibiting liquid 22 in the flow passage as needed or desired.

[0023] A one-way valve 30 is connected to injector line 28 and operates to control the flow of ice prohibiting liquid 22 from tank 20 into flow passage 16 of the wellhead 12. The valve 30 is normally biased into a closed position so that ice prohibiting liquid 22 cannot flow through the injector line 28 from tank 20 and into the flow passage 16. In the illustrated embodiment, valve 30 is a spring-loaded ball check valve that is spring biased into the closed position. Valve 30 is operated from the biased, closed position to the open position when the pressure exerted on the valve by the ice prohibiting liquid 22 is sufficiently great to overcome the biasing force.

[0024] With particular reference to FIG. 2, system 10 is illustrated in connection with wellhead 12 with the system in a first operating state wherein the system is not injecting ice prohibiting liquid 22 in the flow passage 16. Particularly, as illustrated, flow passage 16 is free of ice accumulation and formation fluid 32 flows through flow passage without constraint. Importantly, in such a condition, there is a low pressure differential within the flow passage 16 across the pressure inducer 14. In such as condition, the system 10 does not operate to inject ice prohibiting fluid 22 into the flow passage.

[0025] Turning now to FIG. 3, system 10 is illustrated in connection with wellhead 12 with the system in a second operating state wherein the system injects ice prohibiting fluid 22 in the flow passage 16. As shown here, ice 18 has accumulated in flow passage 16 and the flow of formation fluid 32 across the pressure inducer 14 is constrained by the ice, which has a narrowed the flow passage approximate the pressure inducer. In this condition, there is a high pressure differential within the flow passage 16 across the pressure inducer 14. The pressure within the flow passage 16 downhole (upstream) the pressure inducer is much greater than the pressure of the flow passage uphole (downstream) the pressure inducer.

[0026] The pressure differential within the flow passage 16 across the pressure inducer 14 causes the static pressure of the void space 24 of the tank 20 to increase. The static pressure of the void space 24 continues to increase as more ice accumulates in the flow passage. Once the void space pressure becomes sufficiently high, the force exerted by the ice prohibiting fluid 22 on the valve 30 is great enough to overcome the bias force and open the valve, thereby allowing the flow of ice prohibiting fluid 22 from tank 20 and into flow passage 16. The valve 30 remains open and injection continues until a sufficient amount of ice 18 is removed from the flow passage 16, thereby lowering the pressure differential across the pressure inducer 14 and the static pressure of the void space. The system 10 operates to cycle between states of non-injection and injection automatically as needed when ice accumulates in the flow passage. The only limit to this system it the amount of ice prohibiting fluid that is stored in tank 20. However, the tank volume can be sufficiently large to permit operation of the system 10 through extend periods, thereby reducing servicing intervals.

[0027] A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. An ice preventing system for a well, the system comprising: a pressure inducer disposed across a flow passage of a well; a tank containing a quantity of ice prohibiting fluid; an inlet pressure line connected to said tank in fluid communication with the flow passage of the well at a position downhole of said pressure inducer; an injector line connected to said tank in fluid communication with the flow passage of the well at a position uphole of said pressure inducer; and a check valve disposed across said injector line and normally biased to prevent the discharge of said ice prohibiting fluid from said injector line and into the flow passage.

2. The ice preventing system of claim 1, wherein said inlet pressure line extends through said pressure inducer.

3. The ice preventing system of claim 2, wherein said pressure inducer is a horizontal plate having a diameter less than the diameter of the flow passage.

4. The ice preventing system of claim 1, wherein said pressure inducer is centrally disposed within the flow passage.

5. The ice preventing system of claim 1, wherein said ice prohibiting fluid is liquid methanol.

6. A method of removing ice accumulation in a flow passage of a well, the method comprising the steps of: providing an ice preventing system , the ice preventing system having: a pressure inducer disposed across a flow passage of a well; a tank containing a quantity of ice prohibiting fluid; an inlet pressure line connected to said tank in fluid communication with the flow passage of the well at a position downhole of said pressure inducer; an injector line connected to said tank in fluid communication with the flow passage of the well at a position uphole of said pressure inducer; and a check valve disposed across said injector line and normally biased closed to prevent the discharge of said ice prohibiting fluid from said injector line and into the flow passage; injecting said ice prohibiting fluid into the flow passage when a pressure differential across said inducer is sufficient to bias said check valve open; and ceasing injection of said ice prohibiting fluid into the flow passage when the pressure differential across said inducer is not sufficient to bias said check valve open.

7. The ice preventing system of claim 6, wherein said inlet pressure line extends through said pressure inducer.

8. The ice preventing system of claim 7, wherein said pressure inducer is a horizontal plate having a diameter less than the diameter of the flow passage.

9. The ice preventing system of claim 6, wherein said pressure inducer is centrally disposed within the flow passage.

10. The ice preventing system of claim 6, wherein said ice prohibiting fluid is liquid methanol.

11. An ice preventing system for a flow passage, the system comprising: a pressure inducer disposed across the flow passage; a tank containing a quantity of ice prohibiting fluid; an inlet pressure line connected to said tank in fluid communication with the flow passage at a position upstream of said pressure inducer; an injector line connected to said tank in fluid communication with the flow passage at a position downstream of said pressure inducer; and a check valve disposed across said injector line and normally biased to prevent the discharge of said ice prohibiting fluid from said injector line and into the flow passage.

12. The ice preventing system of claim 11, wherein said inlet pressure line extends through said pressure inducer.

13. The ice preventing system of claim 12, wherein said pressure inducer is a plate having a diameter less than the diameter of the flow passage.

14. The ice preventing system of claim 11, wherein said pressure inducer is centrally disposed within the flow passage.

15. The ice preventing system of claim 11, wherein said ice prohibiting fluid is liquid methanol.

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