ICE PREVENTING SYSTEM AND METHOD FOR A GAS WELL

SYSTEME DE PREVENTION DE LA FORMATION DE GLACE ET METHODE DESTINEE A UN PUITS DE GAZ

English 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.

French Abstract

Système de prévention de la formation de glace conçu pour un passage découlement dun puits ou dun pipeline comprenant un réservoir de fluides renfermant un fluide empêchant la formation de glace et un inducteur de pression positionné dans le passage découlement. Le réservoir de fluide est raccordé de façon fluide au passage découlement, à un emplacement en amont de linducteur de pression, par une conduite de pression dentrée. De plus, le réservoir de fluide est raccordé de façon fluide au passage découlement, à un emplacement en aval de linducteur de pression, par une conduite dinjection de fluide. Une vanne normalement fermée se trouve dans la conduite dinjection de fluide et est ouverte par une différence de pression exercée dans linducteur de pression, par une accumulation de glace dans le passage découlement, ce qui permet linjection du fluide empêchant la formation de glace dans le passage découlement, à partir du réservoir. Une fois la différence de pression diminuée, par le retrait de laccumulation de glace, la vanne se referme et linjection de fluide sarrête.

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;
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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.
11

Description

CA 02887821 2015-04-13
ICE PREVENTING SYSTEM AND METHOD FOR A GAS WELL
FIELD OF THE INVENTION
[001] 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
[002] 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.
[003] 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

CA 02887821 2015-04-13
methanol is injected regardless of whether the methanol it is need to prevent
ice
formation, resulting in significant and unnecessary waste and costs.
[004] 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.
[005] 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
[006] 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.
[007] 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
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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.
[008] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[009] In the drawings:
[010] Figure I 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;
[011] Figure 2 is a front view of an ice preventing system constructed in
accordance
with the principles of an embodiment of the present invention, showing the
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system in a first operating state where ice prohibiting fluid is not injected
to a
well;
[012] Figure 3 is a front view of 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
[013] Figure 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
[014] 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.
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[015] 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 fiat 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 plo-, 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.
[016] 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 ernbodhnent, 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.
[017] 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'
establiches 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.

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[018] 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.
[019] 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.
[020] 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
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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.
[021] 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.
[022] 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
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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.
8

Representative Drawing