Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02889351 2015-04-27
PRESSURE REGULATED DOWNHOLE EQUIPMENT
BACKGROUND OF THE INVENTION
Field of the Invention
Embodiments of the present invention relate generally to apparatuses and
methods for reducing a pressure of a fluid in a wellbore. More
specifically,
embodiments relate generally to an apparatus and method for reducing a
pressure
differential across a valve.
Description of the Related Art
A wellbore is formed by using a drill bit on a drill string to drill through a
geological formation. After drilling through the formation to a predetermined
length or
depth, the drill string and drill bit are removed, and the wellbore is lined
with a string of
casing. The space between the outer diameter of the casing and the wellbore is
referred to as an annulus. In order to prevent the casing from moving within
the
wellbore, the annulus is filled with cement using a cementing operation. In
addition to
preventing the casing from moving within the wellbore, the cemented annulus
also
provides for a stronger wellbore for hydrocarbon production.
When the casing is sent downhole, the casing is typically filled with a fluid,
such
as drilling mud, and the fluid is maintained at a predetermined pressure. The
fluid
within the casing ensures that the casing does not collapse within the
wellbore. A
bottom end of the casing usually includes a float assembly, such as a float
collar or a
float shoe. The float assembly includes one or more unidirectional valves that
allow
fluid from inside the casing to flow out to the annulus, but prevents fluid
from the
annulus to enter the casing. An upper end of the float assembly may also
include a
receptacle for receiving a device, such as a cement plug.
During a cementing operation, it is preferred that the cement is isolated or
separated from other fluids within the casing. When fluids such as drilling
mud mix
with cement, it can cause the cement to sour and fail when it sets.
Accordingly, a first
1
CA 02889351 2015-04-27
plug is usually sent down in front of the cement during a cementing operation.
The
first plug includes one or more fins around its circumference which acts to
separate the
drilling fluid below the first plug from the cement above the first plug. The
fins also
clean the inner walls of the casing as the first plug descends in the casing.
Because
the first plug provides both a separation and cleaning function, the outer
diameter of
the first plug is equal to or larger than the inner diameter of the casing.
The first plug
includes a bore through a center longitudinal portion of its body. The first
plug also
includes a rupture membrane, such as rupture disc, positioned across the bore,
which
prevents the drilling fluid below the first plug from comingling with the
cement above
the first plug. As the first plug descends in the casing, the drilling fluid
is forced
through the float assembly and out into the annulus. The unidirectional valve
within
the float assembly prevents the drilling fluid from moving back into the
casing.
After the first plug reaches the float assembly, hydrostatic pressure builds
on
the upper side of the rupture membrane. Once the first plug reaches a rupture
pressure, the rupture membrane ruptures, and the cement flows through the bore
of
the first plug, through the float assembly, and into the annulus.
A second plug is usually sent down the casing behind the cement, and the
second plug is usually pushed downward with drilling fluid. The second plug
includes
one or more fins that separate the cement below the second plug from the
drilling fluid
above the second plug. The fins also clean the sidewalls of the casing as the
second
plug descends down the casing. As the second plug is pushed through the
casing, the
cement is squeezed out of the float assembly into the annulus until the second
plug
reaches the first plug. In the prior art, at least one of the first or second
plugs form a
seal within the casing, which prevents fluid from moving past the first or
second plugs.
Thereafter, the cement is given time to cure and set up as a constant pressure
is
maintained within the casing.
The pressure of the drilling fluid above the first and second plugs is bled
off, or
reduced, while the pressure of the cement at the base of the casing is
maintained due
to the unidirectional valve. The change in pressure results in a significant
pressure
2
CA 02889351 2015-04-27
, . .
differential across the unidirectional valve of the float assembly within the
casing. To
prevent the float assembly from failing or yielding, the float assembly is
designed with
materials that can withstand high pressure differentials. Accordingly, the
materials
required for high pressure float assemblies are often expensive.
As the foregoing illustrates, what is needed are cost effective apparatuses
and
methods for handling high pressure differentials across a valve. There is also
a need
for apparatus and methods of reducing the pressure difference across float
assemblies
during cementing operations.
SUMMARY OF THE INVENTION
Embodiments of the present invention generally relate to a method of
regulating
a pressure of a fluid in a wellbore. First, a tubular is positioned within the
wellbore.
The tubular is equipped with a first float assembly and a second float
assembly. Each
float assembly includes a unidirectional valve with an inlet and an outlet.
Next, a
pressure differential between the outlet and the inlet of the first
unidirectional valve is
reached. Then, the pressure differential across the first unidirectional valve
is reduced
when a pressure at the outlet is higher than a pressure at the inlet by a
predetermined
amount.
In another embodiment, a method of regulating a pressure of a fluid in a
wellbore includes positioning a tubular equipped with a first float assembly
and a
second float assembly, wherein each float assembly includes a unidirectional
valve
with an inlet and an outlet; reaching a pressure differential between an
upstream
pressure and a downstream pressure of the unidirectional valve of the first
float
assembly; and reducing the pressure differential across the unidirectional
valve of the
first float assembly when the downstream pressure is higher than the upstream
pressure by a predetermined amount.
In one embodiment, reducing the pressure differential across the first
unidirectional valve includes opening a relief valve to allow fluid to move
across the
3
CA 02889351 2015-04-27
first float assembly. In yet another embodiment, the fluid flowing through the
first float
assembly pressurizes an area between the first and second float assemblies.
In another embodiment, a method of regulating a pressure of a fluid in a
wellbore includes positioning a tubular equipped with a first float assembly
having a
first unidirectional valve and a second float assembly having a second
unidirectional
valve, wherein each of the first and second unidirectional valves include an
inlet and
an outlet; and reducing a pressure differential across the first
unidirectional valve when
a pressure at the outlet is higher than a pressure at the inlet by a
predetermined
amount.
The present invention also relates to a system of regulating a pressure of a
fluid
in a wellbore. The system contains a tubular with a first float assembly and a
second
float assembly disposed therein. The first float assembly includes a first
unidirectional
valve for allowing fluid to flow in a first direction. The first float
assembly is also
equipped with a pressure regulating device configured to actuate when a
predetermined pressure differential is reached. The second float assembly
includes a
second unidirectional valve for allowing fluid to flow in the first direction.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the present
invention
can be understood in detail, a more particular description of the invention,
briefly
summarized above, may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however, that the
appended
drawings illustrate only typical embodiments of this invention and are
therefore not to
be considered limiting of its scope, for the invention may admit to other
equally
effective embodiments.
Figure 1 illustrates a casing with cement disposed between a first plug and a
second plug, according to one embodiment of the present invention;
4
CA 02889351 2015-04-27
. .
Figure 2 shows the casing of Figure 1 with cement injected into an annulus and
disposed between a first float assembly and a second float assembly; and
Figure 3 shows the casing of Figure 1 with cement injected into the annulus
and
disposed below the first float assembly in the casing.
DETAILED DESCRIPTION
The present invention relates to apparatuses and methods of reducing pressure
differentials during wellbore operations such as a cementing operation. In one
embodiment, a plurality of float assemblies, each equipped with a relief valve
and
unidirectional valve, may be used to obtain a desired pressure differential
across the
plurality of unidirectional valves.
A method of regulating a pressure of a fluid in a wellbore includes urging a
fluid
through a plurality of unidirectional valves disposed in a plurality of float
assemblies in
a casing. For example, the fluid may be urged in the casing by at least one
plug.
Next, a fluid pressure differential across at least one of the plurality of
unidirectional
valves is reached. The fluid pressure differential is prevented from
increasing above a
predetermined fluid pressure differential. Preventing the first fluid pressure
differential
from exceeding the predetermined fluid differential may include providing a
relief valve
to permit the fluid to re-enter a portion of the casing. The re-entered fluid
may
pressurize the portion of the casing above the at least one of the plurality
of float
assemblies. Preventing the first fluid pressure differential from exceeding
the
predetermined fluid differential may also include moving the at least one of
the plurality
of float assemblies. Moving the at least one of the plurality of float
assemblies
pressurizes the portion of the casing above the at least one of the plurality
of float
assemblies.
Figure 1 shows a casing 102 with cement 104 disposed between a first plug
106 and a second plug 108, according to one embodiment of the present
invention.
As shown, the casing 102 has been inserted into a wellbore 110 and contains a
first
float assembly 112 and a second float assembly 114 at a lower end.
5
CA 02889351 2015-04-27
As shown, the second float assembly 114 includes a bore 116 and a
unidirectional valve 118. The second float assembly 114 also includes an
optional
relief valve 120 and optional spacer 124. The unidirectional valve 118
controls fluid
flow through the bore 116 and is configured to allow fluid to flow through the
bore 116
and out of the casing 102, but prevent fluid from re-entering the casing 102
through
the bore 116. Exemplary unidirectional valves include a check valve, a plunger
valve,
and a flapper valve.
The relief valve 120 controls fluid flow through a second bore 122 of the
second
float assembly 114. The relief valve 120 may be added to any type of valve or
any
type of downhole tool. For example, the relief valve 120 may be added to a
plunger
valve or ball valve and resides on a packer. The relief valve 120 is
configured to allow
fluid to move across the second float assembly 114 at a predetermined pressure
differential. Exemplary relief valves 120 include a check valve, a ball valve,
a plunger
valve, and other suitable valves known to a person of ordinary skill in the
art. In this
embodiment, the relief valve 120 allows the fluid to move across the second
float
assembly 114 through the second bore 122 in a direction opposite the direction
of the
unidirectional valve 118. The second bore 122 may extend longitudinally and/or
radially to couple an upper portion and a lower portion of the second float
assembly
114. The relief valve 120 may also be configured to restrict fluid flow
through the
second bore 122 upon reaching a predetermined reduced pressure differential
across
the second float assembly 114. For example, fluid may flow downwards in the
casing
102 through bore 116 and unidirectional valve 118 and, when a predetermined
pressure differential is reached, the fluid may re-enter an upper portion of
the casing
102 through second bore 122 and the relief valve 120. The relief valve 120 may
again
restrict re-entry of fluid into an upper portion of the casing 102 upon
reaching the
reduced fluid pressure differential across the second float assembly 114. In
another
example, the relief valve 120 may open at a predetermined pressure
differential and
then closes at or below the predetermined pressure differential. In yet
another
example, the relief valve 120 may open at a first pressure differential and
stay open
6
CA 02889351 2015-04-27
below the first pressure differential until a lower, second pressure
differential is
reached, at which time, the relief valve 120 will close.
The optional spacer 124 is generally located on an upper portion of the second
float assembly 114 and couples the second float assembly 114 to adjacent
apparatuses in the casing 102. For example, the spacer 124 may include a
landing
collar on which the first plug 106 lands during the primary cementing
operation. In one
embodiment, the spacer 124 may be integral with the second float assembly 114.
The
spacer 124 includes a channel 126 configured to fluidly couple the second bore
122 to
the bore of the casing 102. For example, fluid ascending in the second bore
122
travels through channel 126 before occupying the inner diameter of the casing
102
above the second float assembly 114. As shown, the channel 126 may extend
longitudinally and/or radially within the spacer 124.
Although only a first float assembly and a second float assembly have been
described herein, it is contemplated that any suitable number of float
assemblies may
be inserted into the casing. Furthermore, although only references to the
second float
assembly have been described herein, any components described with respect to
the
second float assembly may be incorporated into any float assembly, including
the first
float assembly, inserted in the casing. In one example, a multiple float
assembly
system may be used in which all float assemblies are equipped with the relief
valve. In
another example, a first float assembly and a second float assembly equipped
with
relief valves may be disposed in the casing.
As shown, the first plug 106 and the second plug 108 are used to separate
fluids in the casing 102. For example, the first plug 106 and the second plug
108 are
used to separate cement 104 from fluid in front of the cement 104 and fluid
behind the
cement 104. The fluid in front of the cement 104 may be a drilling fluid and
the fluid
behind the cement 104 may be a push fluid, such as a drilling fluid. In some
applications, a spacer fluid may be disposed between the cement 104 and the
fluid in
front of the cement 104, disposed between the cement 104 and the push fluid
behind
the cement 104, or both. In one embodiment, the first plug 106 may be a cement
plug
7
CA 02889351 2015-04-27
having a bore 128 through the first plug 106, and a rupture disc 130
positioned within
the bore 128 to prevent flow therethrough. The rupture disc 130 is configured
to break
at a predetermined pressure. The first plug 106 and the second plug 108 may
include
one or more fins 132 circumferentially positioned on its exterior surface for
sealingly
contacting the wall of the casing 102. The fins 132 act as a barrier to
prevent
comingling of fluids from above and below the respective plugs 106, 108. The
fins 132
may also clean the wall of the casing 102 as the first plug 106 descends in
the casing
102. It is contemplated that the first plug 106 may be any suitable cement
plug known
to a person of ordinary skill in the art.
Although only a single first plug has been described herein, it is
contemplated
any suitable number of plugs may be inserted into the casing prior to the
insertion of
the second plug. In one example, a multiple plug system may be used to
separate
several types of fluids that may be required for certain operations.
During a cementing operation, the first and second float assemblies 112,114
are positioned downhole with the casing 102. As shown in Figure 1, the second
float
assembly 114 is disposed above and axially spaced from the first float
assembly 112
The first plug 106 is sent downhole preceding the cement 104 and behind a
drilling
fluid. After the first plug 106 reaches the second float assembly 114,
hydrostatic
pressure builds on the rupture disc 130 until the rupture disc 130 reaches the
predetermined rupture pressure. After the rupture disc 130 ruptures, the
cement 104
flows through the bore 128 of the first plug 106, through bores 116 of the
second float
assembly 114 via the unidirectional valve 118, and enter the axial space
between the
first and second float assemblies 112, 114. Then, the cement travels through
the bore
116 of the first float assembly 112 via the unidirectional valves 118, and out
of the
casing 102 to an annulus 134. In this example, the unidirectional valves 118
are
shown as flapper valves. The second plug 108, which is behind the cement 104,
descends until it reaches the first plug 106.
Figure 2 shows the casing 102 of Figure 1 after the second plug 108 has
reached the first plug 106 and the cement 104 has been injected into the
annulus 134.
8
CA 02889351 2015-04-27
As shown, some cement 104 is also disposed in the axial space between the
first and
second float assemblies 112,114. The first and second float assemblies 112,114
include the unidirectional valves 118, the relief valve 120, and the second
bore 122.
In one example, while the injection fluid pushes the second plug 108 down the
casing 102, the pressure differential across the unidirectional valve 118 of
the first float
assembly 112 is below a first predetermined pressure differential. However,
after the
second plug 108 reaches the first plug 106, the fluid pressure above the
second plug
108 may be reduced by bleeding off the injection fluid. Bleeding off the
injection fluid
results in an increase in the fluid pressure differential between the fluid
above the
second plug 108 and the fluid below the first float assembly 112. Accordingly,
the fluid
pressure differential between the top and bottom of the unidirectional valve
118 of the
first float assembly 112 may exceed the first predetermined pressure
differential.
When this occurs, the relief valve 120 in the first float assembly 112 opens
to
reduce the fluid pressure differential across the unidirectional valve 118 of
the first float
assembly 112. In this respect, the relief valve 120 permits the cement 104
below the
first float assembly 112 to re-enter the casing 102. For example, the cement
104 re-
enters the casing 102 by ascending in the second bore 122. The cement 104
leaving
the second bore 122 is retained in the space between the first float assembly
112 and
the second float assembly 114. The unidirectional valve 118 and the relief
valve 120
of the second float assembly 114 prevent the cement 104 from flowing through
the
second float assembly 114. Re-entry of the cement 104 into the casing 102
decreases
the pressure of the cement 104 acting on the lower side of the first float
assembly 112
while increasing the pressure of the cement 104 between the first and second
float
assemblies 112, 114. Thus, the fluid pressure differential across the
unidirectional
valve 118 of the first float assembly 112 is reduced. In one embodiment, the
relief
valve 120 closes when the pressure differential is at or below the first
pressure
differential. In another embodiment, the relief valve 120 remains open until a
closing
pressure differential below the first pressure differential is reached. For
example, the
relief valve may remain open until the pressure differential is less than 95%,
less than
90%, or less than 80% of the first pressure differential. In other examples,
the relief
9
CA 02889351 2015-04-27
valve may remain open until the pressure differential is from 75% to 95%, from
75% to
90%, or from 65% to 80% of the first pressure differential.
The pressure differential across the unidirectional valve 118 of the second
float
assembly 114 increases as the pressure between the first and second float
assemblies 112, 114 increases. When the pressure differential across the
unidirectional valve 118 of the second float assembly 114 reaches a second
predetermined pressure differential, the relief valve 120 in the second float
assembly
114 opens to permit cement 104 to re-enter the casing 102 above the second
float
assembly 114. As a result, the pressure difference across the unidirectional
valve 118
of the second float assembly 114 is reduced. In one embodiment, the relief
valve 120
in the second float assembly 114 closes when the pressure differential is at
or below
the first pressure differential. In another embodiment, the relief valve 120
remains
open until a closing pressure differential below the first pressure
differential is reached.
For example, the relief valve may remain open until the pressure differential
is less
than 95%, less than 90%, or less than 80% of the second pressure differential.
In
other examples, the relief valve may remain open until the pressure
differential is from
75% to 95%, from 75% to 90%, or from 65% to 80% of the second pressure
differential. In this manner, a plurality of float assemblies 112, 114
equipped with a
plurality of relief valves 120 may be used to obtain a desired total pressure
drop
across the first float assembly 112 and the second plug 108.
In the embodiment shown in Figure 2, the pressure from the re-entry of cement
104 above the second float assembly 114 may cause the first and second plug
106,108 to ascend in the casing 102. Re-entry of the cement 104 into the
casing 102
above the second float assembly 114 decreases the pressure of the cement 104
acting on the lower side of the second float assembly 112 while increasing the
pressure of the cement 104 between the second float assembly 114 and plugs
106,
108.
Figure 3 illustrates another embodiment of a plurality of float assemblies
configured to reduce a pressure differential. Figure 3 shows the casing 102 of
Figure
CA 02889351 2015-04-27
. ,
1 with cement 104 injected into the annulus 134 and disposed below the first
float
assembly 172 in the casing 102. As shown, the first float assembly 172
includes the
unidirectional valve 118 and is configured to move in response to a first
predetermined
pressure differential. Although this first float assembly 172 is shown without
a relief
valve, it is contemplated the first float assembly 172 may be equipped with a
relief
valve.
In one example, the pressure differential across the unidirectional valve 118
of
the first float assembly 172 may be below the first predetermined pressure
differential
while the injection fluid pushes the second plug 108 down the casing 102.
However,
after the second plug 108 reaches the first plug 106, the fluid pressure above
the
second plug 108 may be reduced by bleeding off the injection fluid. Bleeding
off the
injection fluid results in an increase in the fluid pressure differential
between the fluid
above the second plug 108 and the fluid below the first float assembly 172.
Accordingly, the fluid pressure differential between the top and bottom of the
unidirectional valve of the first float assembly 172 may exceed the first
predetermined
fluid pressure differential.
In order to reduce the fluid pressure differential across the unidirectional
valve
118 of the first float assembly 172, the first float assembly 172 may ascend
or descend
within the casing 102. In order to ascend or descend, the first float assembly
172 is
equipped with a dynamic seal, which seals the first float assembly 172 to the
casing
102. In one embodiment, the dynamic seal includes an 0-ring disposed around
the
circumference of the first float assembly 172. Accordingly, the first float
assembly 172
is not cemented in place in the casing 102. A biasing member, such as a
spring, may
be disposed between the first float assembly 172 and the second float assembly
114
to control the ascent of the first float assembly 172 in the casing 102. For
example,
the spring may bottom out to end the ascent of the first float assembly 102
when the
pressure differential across the unidirectional valve 118 of the second float
assembly
114 reaches a second predetermined pressure. Other instruments known to
persons
having ordinary skill in the art may be used to end the ascent of the first
float assembly
102. For example, a stop may be used. Thus, the first float assembly 172 may
11
CA 02889351 2015-04-27
=
ascend from its original position at the foot of the casing 102 and move
toward the
second float assembly 114 when the first predetermined fluid pressure
differential is
reached across the unidirectional valve 118. As a result, the pressure exerted
on the
lower side of the first float assembly 172 decreases, thereby reducing the
pressure
differential across the unidirectional valve 118 of the first float assembly
172.
Movement of the first float assembly 172 also causes the pressure between the
first and second float assemblies 172, 114 to increase, which increases the
pressure
differential across the unidirectional valve 118 of the second float assembly
114.
When the pressure differential across the unidirectional valve 118 of the
second float
assembly 114 reaches the second predetermined pressure differential, the
relief valve
120 in the second float assembly 114 may open to reduce the pressure
differential
across the unidirectional valve 118 of the second float assembly 114. In this
manner,
the overall pressure differential across the unidirectional valves 118 of the
first and
second float assemblies 172, 114 may be reduced. In Figure 3, the first float
assembly 172 has moved to a position adjacent the second float assembly 114.
In yet another embodiment, the second float assembly 114 may be configured
to ascend in response to the second predetermined pressure differential. In
this
respect, after the second predetermined pressure differential is reached due
to
movement of the first float assembly 172, the second float assembly 114 may
begin to
move in order to reduce the pressure differential across the unidirectional
valve 118 of
the second float assembly 114.
In yet another embodiment, each or both of the first and second float
assemblies may be equipped with at least one relief valve, movable
configuration, or
both. For example, a relief valve 120 in the first float assembly 112 may
allow cement
104 to enter the casing 102 between the first and second float assemblies
112,114. In
response, the second float assembly 114 may either ascend in the casing 102 or
the
relief valve 120 may open, or both, to reduce the pressure across the
unidirectional
valve 118 of the second float assembly 114.
12
CA 02889351 2015-04-27
In one embodiment, rather than using a single piece of equipment to counteract
the fluid pressure in the casing, multiple pieces of equipment with pressure
regulating
devices may be added to the system to limit the maximum fluid pressure
counteracted
by each piece of equipment. By dividing the overall fluid pressure
differential among
the float assemblies in the casing, the system may counteract a higher fluid
pressure
differential as compared to using only one float assembly. Furthermore,
because float
assemblies with high fluid pressure capacities are more costly than float
assemblies
with low fluid pressure capacities, the system may be less expensive to
implement
even with multiple low fluid pressure float assemblies. It must be noted that
although
embodiments are described herein using a plurality of float assemblies, it is
contemplated that these embodiments are equally applicable to any suitable
valve
equipped with a relief valve, configured to move, or both. For example, two
unidirectional valves equipped with relief valves may be used to counteract a
predetermined pressure differential.
In one embodiment, a method of regulating a pressure of a fluid in a wellbore
includes positioning a tubular equipped with a first float assembly and a
second float
assembly, wherein each float assembly includes a unidirectional valve with an
inlet
and an outlet; reaching a pressure differential between an upstream pressure
and a
downstream pressure of the unidirectional valve of the first float assembly;
and
reducing the pressure differential across the unidirectional valve of the
first float
assembly when the downstream pressure is higher than the upstream pressure by
a
predetermined amount.
In another embodiment, a method of regulating a pressure of a fluid in a
wellbore includes positioning a tubular equipped with a first float assembly
having a
first unidirectional valve and a second float assembly having a second
unidirectional
valve in a wellbore, wherein each of the first and second unidirectional
valves include
an inlet and an outlet; and reducing a pressure differential across the first
unidirectional valve when a pressure at the outlet of the first unidirectional
valve is
higher than a pressure at the inlet of the second unidirectional valve by a
predetermined amount.
13
CA 02889351 2015-04-27
In another embodiment, reducing the pressure differential across the first
unidirectional valve includes opening a relief valve to allow fluid to move
across the
first float assembly.
In one more of the embodiments described herein, the fluid flowing through the
first float assembly pressurizes an area between the first and second float
assemblies.
In one more of the embodiments described herein, the method includes
reducing a pressure differential across the second unidirectional valve when
the
pressure differential across the second unidirectional valve reaches a second
predetermined pressure differential.
In one more of the embodiments described herein, the relief valve closes when
the pressure differential is at or below the predetermined amount.
In one more of the embodiments described herein, the relief valve closes when
the pressure differential is below the predetermined amount of pressure
differential.
In one more of the embodiments described herein, the relief valve remains
open until the pressure differential is less than 80% of the predetermined
amount of
pressure differential.
In one more of the embodiments described herein, reducing the pressure
differential across the first unidirectional valve pressurizes an area between
the first
and second float assemblies.
In one more of the embodiments described herein, reducing the pressure
differential across the first unidirectional valve includes moving the first
float assembly
toward the second float assembly.
In one more of the embodiments described herein, moving the first float
assembly pressurizes an area between the first and second float assemblies.
In another embodiment, a system for regulating a pressure of a fluid in a
wellbore includes a tubular; a first float assembly disposed in the tubular,
wherein the
14
CA 02889351 2015-04-27
=
first float assembly includes a first unidirectional valve for allowing fluid
to flow in a first
direction; and a second float assembly disposed in the tubular, wherein the
second
float assembly includes a second unidirectional valve for allowing fluid to
flow in the
first direction; wherein the first float assembly is equipped with a pressure
regulating
device configured to actuate when a predetermined pressure differential is
reached.
In one more of the embodiments described herein, the pressure regulating
device includes a relief valve for allowing fluid to flow in a second
direction.
In one more of the embodiments described herein, the pressure regulating
device includes a movable first float assembly.
In one more of the embodiments described herein, the system includes a first
plug and a second plug, wherein the first plug includes a removable seal.
In one more of the embodiments described herein, the removable seal includes
a rupture disc.
In one more of the embodiments described herein, reducing the pressure
differential across the first unidirectional valve includes opening a relief
valve to allow
fluid to move across the first float assembly.
In one more of the embodiments described herein, reducing a pressure
differential across the second unidirectional valve when a pressure at the
outlet is
higher than a pressure at the inlet by a predetermined second amount.
While the foregoing is directed to embodiments of the present invention, other
and further embodiments of the invention may be devised without departing from
the
basic scope thereof, and the scope thereof is determined by the claims that
follow.
