Note: Descriptions are shown in the official language in which they were submitted.
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A METHOD AND A DEVICE FOR REGULATING A FLUID FLOW BETWEEN AN
OUTSIDE AND AN INSIDE OF A WELL PIPE
This invention regards a method of regulating a fluid flow
between the outside and the inside of a well pipe. More
particularly, it concerns a method in which a temperature
controlled valve placed between the inside and the outside of
a well pipe is influenced by the temperature of a fluid at
the valve. The method is particularly suited for use during
steam injection into a reservoir, and in cases where it is
desirable to prevent steam and any unwanted hydrocarbons from
flowing into the well pipe. The invention also comprises a
device for implementing the method.
In this context the term well pipe is taken to mean any form
of hollow body used to recover well fluid from a reservoir or
to inject fluid into the reservoir.
It is known to use water vapour, hereinafter termed steam, to
heat well fluid in a reservoir where the well fluid has a
relatively high viscosity. The purpose of such steam supply
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is to reduce the viscosity and with this increase the rate of
production from the reservoir.
In prior art steam is introduced into the reservoir in an
injection well through the bore of a pipe and may be
distributed from the bore via associated distributing means
such as nozzles.
The intention is that the steam from the distributing means
should, on the whole, distribute evenly throughout the
reservoir and heat the well fluid to make it flow more easily
to a well pipe (production well) located in the reservoir.
However, it has proven difficult to achieve a uniform
distribution for the flow of steam throughout the reservoir.
Typically, after a while, areas will form where the steam
flows relatively unhindered from the bore of the pipe and
into the production well. Such a flow of steam is undesirable
as it leads to a loss of valuable steam.
It is known to place inlet regulating valves in a production
well. Thus, GB Patent application 2 371 578 concerns a flow
control valve arranged to be controlled by an electrical
signal or by the well temperature. However, this valve is not
arranged to regulate the flow by use of different well fluid
temperatures.
The object of the invention is to remedy the disadvantages of
prior art.
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The object is achieved in accordance with the invention, by
the characteristics stated in the description below and in
the following claims.
A well pipe, typically a production tubing, provided with a
number of temperature controlled valves, hereinafter termed
valve, located in the reservoir along its longitudinal
extent, is placed in a production well. The valves are
arranged to open and close for fluid flow between the outside
and inside of the production tubing.
A number of annular packings are placed in an annulus defined
by the production tubing and the well wall, alternatively the
production tubing and the liner or sand screen in the well.
The annular packings, which are arranged to sealingly divide
the annulus into annulus sections, are distributed along the
production tubing in such a way that at least one valve is in
each annulus section.
The valve remains open as long as heated fluid flows in
through the valve from the adjacent annulus and into the
production tubing.
The valve will shut off the flow upon inflow of steam or high
temperature hydrocarbons into the annulus in question.
This will then prevent steam from flowing into the production
tubing to any appreciable extent. Consequently, the available
steam can be utilized to heat the well fluid flowing into the
production tubing via other well sections.
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In a preferred, relatively simple embodiment of the valve the
production tubing is provided with a through opening in the
pipe wall. A slide is displaced between an open position in
which the slide does not cover the through opening, and a
closed position in which the slide covers the opening.
The slide can be placed in the bore of the production tubing
or externally about the production tubing and be controlled
by a relatively long body that has a different coefficient of
expansion from that of the production tubing. The principle
of operation of the valve is explained in greater detail in
the specific part of the application.
If so desired, the valve can be a separate part connected to
the production tubing. If so desired, the valve can be
overridden by an electrical heating element at the long body.
If so desired, temperature controlled valves according to
prior art can be used for said purpose.
The method and device according to the invention are also
suitable for stopping incoming gas that as a result of a
pressure drop experiences a reduction in temperature; for
shutting off injected water that is somewhat colder than
formation fluids; and for regulating the inflow of injection
water in a water injector by throttling the relatively cold
injection water by means of a sensing device on the outside
of the well pipe.
The following describes a non-limiting example of a preferred
method and embodiment illustrated in the accompanying
drawings, in which:
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Figure 1 schematically shows a well formation in which a pipe
has been inserted for introduction of steam, and where a
production tubing is provided with a number of temperature
controlled valves, the annulus between the production tubing
and the well wall being divided up by means of annular
packings;
Figure 2 shows in a larger scale a sectional view of an open
temperature controlled valve; and
Figure 3 is a sectional view of the temperature controlled
valve of figure 2 in the closed position.
In the drawings reference number 1 denotes a reservoir in the
ground, containing a relatively viscous well fluid.
A pipe 2 for introducing steam into the reservoir 1 has been
inserted in the reservoir 1. A production well 4 is also
provided in the reservoir 1.
A well pipe 6 (production tubing) encircled by a number of
annular packings ~ distributed along the length of the
production tubing 6, is provided in the production well 4.
The annular packings ~ divide an annulus between the wall of
the production well 4 and the well pipe 6 into sections, of
which a first, a second and a third section marked 10, 12 and
14, respectively, are shown in figure 1.
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At each section 10, 12, 14 the well pipe 6 has been given
through openings 16 through which fluid from the reservoir 1
can flow into the well pipe 6.
Each opening 16 is provided with a temperature controlled
valve 18 arranged to open and close for fluid. flow between
the outside of the well pipe 6 and its bore.
The valve 18, see figure 2, comprises the opening 16 that
goes through the pipe wall of the well pipe 6. A slide 22 is
arranged to be displaceable and to seal against the through
opening 16. The slide 22 is arranged to be moved between an
open position in which the slide 22 does not cover the
through opening 16 and a closed position in which the slide
22 covers the opening 16.
The slide 22 is connected to one end portion of a relatively
long body 24, the opposite end portion of which is connected
to the well pipe 6. The material of the long body 24 has a
linear expansion coefficient that is greater than that of the
well pipe material. When the temperature increases, the long
body 24 expands more than the well pipe 6, whereby the slide
22 moves in the direction of its closed position covering the
opening 16.
A jacket 26 encloses the long body 24 and is arranged to
guide the fluid flow from the corresponding opening 16
towards the long body 24, thus to prevent the long body 24
from being affected to any significant degree by the
temperature in the rest of the fluid flowing in the well pipe
6.
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Steam passed from the bore 2 into the reservoir 1 condenses
after flowing a distance into the reservoir formation. The
dotted line 28 in figure 1 indicates where in the reservoir 1
the steam is condensed.
Steam flows through the reservoir and into the third section
14, from where the steam flows on into the well pipe 6. The
temperature controlled valve 18 corresponding to the third
section 14 is about to shut off the fluid flow from the third
section 14 into the well pipe 6.
The fluid flow from the other sections 10 and 12 is
substantially unaffected by the steam breakthrough into the
third section 14.
Known annular packings 8 may be used. It has proven
advantageous to use a swelling annular packing 8, where the
material of the annular packing 8 is caused to swell upon
contact e.g. with hydrocarbons.
In alternative embodiments (not shown) the temperature
controlled valves 18 may be electrically heated valves
according to prior art known per se.
