Note: Descriptions are shown in the official language in which they were submitted.
CA 02568212 2006-11-15
DESCRIPTION
After a certain time of gas production from gas reservoir, using the natural
reservoir
pressure drive, the reservoir pressure reduces to a level where this pressure
is lower than
the hydrostatic pressure of water in the well-casing. Under these conditions,
the water
does not allow the gas to flow to the surface by the reservoir pressure. In
the gas industry
this phenomena is called "watered-out gas-well" and it will be abandoned. By
conventional methods, for re-activating these wells, the water inside the well-
casing is
removed allowing the gas from the reservoir entering the well-casing and can
be
recovered. For removal of the water from the casing, different kinds of water-
pumps or
other methods are used. In this case, at the beginning and by startup, the
pump must have
a high capacity to be able to pump the water out of the well-casing and also
the water
coming from the reservoir. To maintain low water-level, the pump must be
continuously
active in order to pump the water out of the casing. This process is very slow
and costly.
The new invention:
By the new invention, the bottom part of the well-casing is divided into three
sections and
each section is separated by means of using inflatable packers. A long tubing
is placed
inside the casing with a submersible pump at its bottom end. The tubing
protrudes
through the three packers, and the top end is connected to the well-head. This
system is
used for pumping the water out of the well-casing. A short water-pipe
protrudes through
the same three packers to connect the upper part of the casing to the lower
section of the
divided lower part. This water-pipe is equipped with a non-return valve to
avoid water
and gas passing from the lower section at the bottom into the upper part of
the well-
casing. The upper packer is equipped with a modulating valve to keep the water
at a
suitable level. At the beginning of the process, all the three packers are
inflated,
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CA 02568212 2006-11-15
separating the three sections and avoiding leakages from one of the sections
into the
other. When the pump is activated, the water over the upper packer in the
casing will
flow through the water-pipe toward the bottom of the casing into the lower
section and is
pumped out through the water-tubing. This procedure continues until the water
over the
upper packer in the well-casing and also in the bottom section is pumped out.
At this
time, the middle and the lower packers will be deflated making the three
sections into one
section thereby allowing the gas and water, from the perforated section of the
casing, to
enter into the casing below the upper packer. At this stage, the water and gas
coming
from the reservoir fill the whole area below the upper packer. The gas flows
upward and
is collected under the upper packer pushing the water downward to a certain
level. This
level will be changed by pressure fluctuation and is controlled and maintained
by means
of available modulating valves and level-sensing devices. The modulating valve
is
placed on the upper packer and is equipped with a non-return feature which
allows the
gas to pass into the upper part of the casing. The pressure is then pre-
adjusted for
controlling the water-level. When the modulating-valve opens, the collected
gas passes
into the upper part of the casing. The recovered gas in the casing is then
passed through a
gas control-valve outside the casing, into a connected pipeline for further
processing.
Description of the drawings:
Fig. I is a front cross-sectional view of an active gas-well in operation
showing:
a) a well-casing (1) for collecting gas and prevention of gas leakage into the
well-walls, the casing is partly perforated (2) in the gas reservoir areas and
is
closed with a well-head (3) for preventing gas to flow out of the casing;
b) a well-tubing (4) for gas flowing to the surface; the tubing is held in the
well-
casing by means of numbers of tubing holders (24, 25) and is prepared with a
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CA 02568212 2006-11-15
gas-pipe system consisting of a gas-pipe (5) on top of the tubing which is
connected to a modulating-valve (6) at the end of the same pipe (5) for
controlling the gas pressure and gas-flow (7);
c) gas flow (8) coming from gas the reservoir;
d) gas flow (9) inside the casing (1) and inside the tubing (12);
e) water flow (10) and water-level (11).
Fig. 2 is a front cross-sectional view of a gas-well according to the Fig. 1
showing
additional equipment arrangement for watered-out wells conventional gas
recovery
method, including:
a) a water-pump (13) for pumping the water out (14);
b) water-level (15) before water is pumped out;
c) Water-level (16) after water is pumped out.
In this case, the gas-pipe system (5, 6, 7) is mounted on the side of the well-
tubing (4).
Fig. 3 is a front cross-sectional view of watered-out gas-well according to
Fig. 2 with
additional equipment arrangement according to the new invention including:
a) upper packer (17) separating the casing upper part (L1) and the lower part
(L2); the upper packer (17) is prepared with a control-valve (21) to control
the
reduced water to a low level (16) and maintain it within a suitable range;
b) middle packer (18) to avoid, by startup, gas (9) and water (10) coming from
gas reservoir (8) entering the upper section (U);
c) lower packer (19) to avoid the exchange of gas/water between middle section
(M) and bottom section (B);
d) a short water-pipe (20) protrudes through the three packers (17,18,19) and
is
prepared with a one-way valve (22) to allow the water flow (23) into the
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CA 02568212 2006-11-15
tubing (20) and entering the bottom section (B), but avoiding reverse flow of
the water.
Fig. 4 is a front cross-sectional view of watered-out gas-well according to
Fig. 3 after the
three inflatable packers (17, 18, 19) are deflated according to the new
invention.
The Operation Procedures:
A- The operation of the active gas-wells:
After drilling a gas-well, the casing (1), is placed into the well to
stabilize the well-walls
and by high gas pressure avoiding leakages of gas from inside the well into
the well-walls
reducing the amount of gas to be recovered. A part of the casing is perforated
(2) for gas
entering the casing (1). The gas (8) enters the casing (1) through perforation
part (2) of
the casing (1) and flows (9) toward surface until the well-casing (1) and the
tubing (4) are
filled with gas. By increasing gas pressure inside the well-casing (1) and
opening the
gas-valve (6), the gas (9) inside the well-casing (1) passes (12) the tubing
(4), the gas-
pipe (5), control-valve (6) and thereafter, flows (7) out of the system into a
pipeline for
further processing and use.
B- The conventional operation after the gas-well is watered-out:
After a certain time of gas production, the amount of produced water increases
and the
water-level (Fig. 1, # 11) in the casing.(1) goes higher to a level (Fig. 2,
#15) and the
water hydrostatic pressure does not allow the gas (8) from the reservoir to
pass the
perforation (2) and enter into the well-casing (1). To reduce the water
hydrostatic
pressure, the water-level (15) must be lowered to a level (16) by removing
water from the
casing (1). The pump (13) mounted on the bottom of the tubing (4) pumped the
water
(10) into the tubing (4) and from there the water (12) flows to the surface
(14) and out of
the well-casing (1). The gas (9) flows upward through the reduced water
column, passes
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the water-level and is collected in the casing (1) above the water-level.
After opening the
valve (6), the gas passes through the pipe (5) and out of the system into a
pipeline for
further processing and use.
C- The operation after a gas-well is watered-out using the New Invention
Method:
For reactivating a watered-out gas-well, three inflatable packers (17, 18, 19)
are placed at
the bottom of the well-casing (1) with a certain distance from each other for
dividing the
bottom part (L2) of the well-casing (1) in three sections: upper (U), middle
(M) and
bottom (B). The long well-tubing (4) placed inside the well-casing (1),
equipped with the
water-pump (13) at its bottom for pumping the collected water from the casing
(1). The
said tubing is supported by means of numbers of tubing holders (24) along the
well-
casing (1) and protrudes the three packers (17, 18, 19). The short water-pipe
(20)
supported by a few pipe and tubing holders (25), equipped with the one-way
valve (22),
protrudes also through the three packers (17, 18, 19) connecting the upper
part (L 1) of the
well-casing (1) with the bottom section (B) of the lower part (L2) of the
casing. The one-
way valve (22), mounted on the water-pipe (20), prevents water from the bottom
section
(B) entering the upper part (L 2) of the well-casing (1). The modulating-valve
(21)
mounted on the upper packer (17) controls the water level (16) by means of gas
pressure
and/or a water-level control device. By startup, all three packers (Fig. 3, #
17, 18, 19) are
inflated, the pump (13) is activated and pumps the water (23) from upper part
(L 1) of the
casing (1) out through the one-way valve (22), the water-pipe (20) and the
bottom
section (B). After the water from the upper part (L1) of the casing (1) is
pumped out and
the water-level (15) is lowered down to the upper packer (17), the pump (13)
is shut
down, the middle packer (Fig. 4, #18) and lower packer (Fig. 4, #19) are then
deflated
turning the three sections (U, M, B) into one large section as the lower part
(Fig. 4, L2) of
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the casing (1). The gases (8) from the reservoir enter the casing (1) through
perforation
part (2) and flow upward (9) and is collected under the upper packer on top of
the water
inside the lower part (L2) of the well-casing (1). With increasing the gas
pressure inside
the lower part (L2) of the casing (1) under the packer (17) the water-level
lowers down.
This level (16) will be changed, going up and down, by fluctuation of the gas
pressure.
To maintain a suitable range for the water-level (16) the modulating-valve
(21) is pre-
adjusted. By certain pressure the valve (21) opens and the collected gas under
the packer
(17) enters the upper part (U) of the well-casing (1) and is collected there
until the
control-valve (6) is opened and the collected gas passes the gas-pipe (5), the
control-
valve (6) outside the well-casing (1) and flows out (7) into a pipeline for
further
processing and use.
During the gas recovery, some water (10) enters the casing (1) as well which
increases
the water-level (16). At this time, the water-pump (13) is reactivated and the
surplus
water can be pumped out.
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