Note: Descriptions are shown in the official language in which they were submitted.
CA 02541318 2006-03-27
WELL CEMENTING APPARATUS AND METHOD
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for cementing
individual and multi- zones in a vertical, directional or horizontal wellbore,
using
concentric tubing or drill pipe.
BACKGROUND OF INVENTION
Cementing is used in the oil and gas industry to seal off fluids and
unconsolidated materials from entering the well bore, for packing off unwanted
zones, as a loss circulation material and to abandon wells.
Current cementing technology requires a casing or liner to be placed in the
well
bore and a cement slurry is then pumped downhole and back up into the space
or annulus between the casing or liner and the wall of the well bore. However,
each succeeding casing or liner placed in the wellbore has an outside diameter
significantly reduced in size when compared to the casing or liner previously
installed. Thus, each time casing is run in a wellbore the diameter of the
wellbore is reduced by the size of that casing.
Further, where operations require the cementing of casing such as the setting
of
surface or production casing, there is the need to use the following
equipment: a
casing shoe, float equipment and cement plug. This equipment can only be
removed by.drilling them out. This takes up valuable drilling time and can
prove
difficult when using a reverse circulation concentric drill string system.
The present invention allows the cementing operation to be completed without
the need to run casing or have cement returned to surface thereby allowing
larger diameter wellbores to be drilled into zones of interest. Further, time
and
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money are saved on not having to run intermediate casing strings, and cement
does not have to be pumped to surface. Finally, the present invention allows
cementing to be completed without having to drill out equipment such as cement
plugs, float equipment and casing shoes.
SUMMARY OF THE INVENTION
The present invention provides a cementing apparatus for use in cementing
operations using concentric tubing or drill string such as concentric drill
pipe,
concentric coiled tubing, and the like, which concentric tubing or drill
string is
generally referred to herein as concentric drill string. Concentric drill
string
comprises an inner string having an inner conduit and an outer string forming
an
annular conduit therebetween. The present invention further provides a method
for cementing a well using concentric tubing or drill string. Finally, the
present
invention provides concentric drill string modified for use in cementing a
well.
Examples of cementing operations where the cementing apparatus, modified
concentric drill string, and cementing method of the present invention can be
used include:
= cementing in a casing;
= well abandonment;
= cementing zones off without using casing;
= repairing damaged underground aquifiers, which result from drilling and
fractioning stimulation operations.
In one aspect of the invention, a cementing apparatus is provided comprising
an
isolation cementing tool and a cementing flow control means. In one
embodiment, the isolation cementing tool has a center tube and an outer casing
forming an annular conduit therebetween. The isolation cementing tool further
has an expandable packer means surrounding at least partially the outer
casing.
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The isolation cementing tool is adapted to connect to a bottom of a piece of
concentric drill string in such a fashion as to be in fluid communication with
the
concentric drill string.
In one embodiment, the cementing flow control means also has a center tube
and an outer casing forming an annular conduit therebetween and is either
directly connected to the bottom of the isolation cementing tool or separated
from
the isolation cementing tool by additional pieces of concentric drill string
of
varying lengths such that the cementing flow control means is also is in fluid
communication with both the isolation tool and the concentric drill string.
The cementing flow control means further has a means for stopping or
regulating
flow, positioned either in the annular conduit between the center tube and the
outer casing or in the center tube, i.e., in the inner conduit, to prevent
cement
from flowing upwardly through the annular conduit and inner conduit when
cement is being pumped down through the opposite conduit. Thus, during the
cementing operation, the cementing flow control means operates to allow the
flow of cement down through one conduit but not up through the other conduit
by
having the means for stopping or regulating flow, which is positioned in the
other
conduit, in the "closed position". On the other hand, when cementing is
completed and it may be desirable to pump a fluid such as water, air, gas,
etc.,
down through the closed or sealed conduit, as will be described in more detail
below, the means for stopping or regulating flow is now placed in the "open
position" to allow the fluid to be delivered therethrough.
Means for stopping or regulating flow may comprise a single valve operable to
open and close with or without actuating means, multiple valves, at least one
non-valved flow divider, or at least one other flow restrictor known in the
art. In
one embodiment, the means for stopping or regulating flow comprises at least
one check valve located in either the annular conduit or the inner conduit. It
is
understood that check valves are generally mechanical valves that permit gases
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and liquids to flow in only one direction, thereby preventing process flow
from
reversing. They are often classified as one-way directional valves. Fluid flow
in
the desired direction opens the valve, while backflow forces the valve closed.
The mechanics of check valve operation are not complicated. For example,
many check valves contain a ball that sits freely above the seat, which has
only
one through hole. The ball has a slightly larger diameter than that of the
through
hole. When the pressure behind the seat exceeds that above the ball, liquid is
allowed to flow through the valve. But once the pressure above the ball
exceeds
the pressure below the seat, the ball returns to rest in the seat, forming a
seal
that prevents backfiow.
It is understood, however, that check valves use a variety of technologies to
allow and stem the flow of liquids and gases. Some of these technologies are
as
follows: single disc swing valves, double disc swing valves, lift-check,
silent, ball-
check and cone-check.
Single disc swing valves are designed with the closure element attached such
that the closure element can be pushed aside by the flow, but swings back into
the close position upon flow reversal. Double disc or wafer check valves
consist
of two half-circle disks hinged together that fold together upon positive flow
and
retract to a full-circle to close against reverse flow. The valve may be
inserted
between two flanges.
Double disc swing valves are useful when means for stopping or regulating flow
is located in the annular conduit. In this embodiment, it is understood that
the
two half-circle disks will be C-shaped to allow each half-circle to enclose
half of
the annular conduit. When each half-circle disc is in the closed position, it
is
understood that the entire annual conduit is now sealed and the flow of any
fluid
therethrough is stopped.
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It is understood that the means for stopping or regulating flow may comprise
other types of valves which open and close using various actuating means
rather
than mechanically opening and closing as a result of fluid flow. It is also
understood that the means for stopping or regulating flow may comprise other
non-valved flow dividers or flow restrictors known in the art.
In one embodiment of the cementing flow control means where the means for
stopping or regulating flow is located in the annular conduit of the cementing
flow
control means, which embodiment is used when cement is pumped through the
inner conduits, the inner diameter of the center tube of the cementing flow
control
means is reduced at or near the bottom end thereof to prevent a cement plug
from exiting therefrom, as will be explained in more detail below. In another
embodiment of the cementing flow control means where the means for stopping
or regulating flow is located in the inner conduit of the cementing flow
control
means, which embodiment is used when cement is pumped through the outer
conduits, the inner diameter of the outer casing of the cementing flow control
means is reduced at or near the bottom end thereof to prevent a donut-shaped
cement plug from exiting therefrom.
In operation, when the packer means of the isolation cementing tool is in the
expanded position, the isolation cementing tool is in the "closed position"
and
when the packer means is in the contracted position the isolation cementing
tool
is in the "open position". When in the contracted or open position, fluids are
free
to flow through the outer annulus between the concentric drill string and the
formation walls. In a preferred embodiment, the expansion of the packer means
is controlled by an electric current for quicker opening and closing of the
isolation
cementing tool, however, other means for expanding and contracting a packer
known in the art can also be used.
When running the cementing apparatus in the hole, the isolation cementing tool
is in the open position, i.e., the packer means is contracted. When the tool
is in
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the open position it does not restrict or reduce the radius of the annulus
between
the outside wall of the drill string and the wellbore, as the outside diameter
of the
tool is preferably equal to, less than or slightly larger than the outside
diameter of
the concentric drill string.
When cementing is required, the isolation cementing tool, which is now
positioned directly above the zone to be cemented, is put in the closed
position,
i.e., the packer means is expanded to abut the adjacent wellbore walls. Thus,
the portion of the well bore below the isolation cementing tool is shut off or
isolated from the portion of the well bore above the tool as the expanded
packer
means will not allow fluids to flow passed it.
According to another aspect of the invention, there is provided a system for
cementing a zone in a wellbore, comprising:
= an open hole annular expandable packer means;
= a concentric drill string having a top and bottom comprising an inner string
having an inner conduit and situated within an outer string to form an
annular conduit therebetween, said concentric drill string having an
outside diameter such that it can be snugly inserted through the center of
the annular expandable packer means ; and
= a means for stopping or regulating flow positioned at or near the bottom of
the concentric drill string in either the annular conduit or the inner
conduit.
Any number of annular expandable packer means known in the art can be used,
for example, a TAM International inflatable Casing Annulus Packers (CAPTM).
Other examples of packer means useful in the present invention can be found in
U.S. 5,743,335 and U.S. 6,988,557, incorporated herein by reference. Further,
any number of means for stopping or regulating flow known in the art can be
used, as described above. In a preferred embodiment, one of the inner string
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and outer string has a reduced internal diameter at or near the bottom thereof
to
prevent a cementing plug from exiting the concentric drill string.
According to another aspect of the present invention, the concentric drill
string
itself can be modified for use in cementing operations of the present
invention.
Hence, concentric drill string having an inner string with an inner conduit
and
situated within an outer string to form an annular conduit therebetween is
provided for use in cementing a zone in a wellbore, the concentric drill
string
comprising:
= an expandable packer means surrounding the outer string at or near a
bottom end of the concentric drill string; and
= a means for stopping or regulating flow positioned at or near the bottom of
the concentric drill string in either the annular conduit or the inner
conduit.
According to another aspect of the invention, there is provided a method for
cementing a zone in a wellbore formation with cement, comprising:
= providing a concentric drill string comprising an inner string having an
inner conduit and situated within an outer string to form an annular conduit
therebetween;
= pumping cement down one of the inner or annular conduits of the
concentric drill string to the zone to be cemented;
= sealing off an outside annulus formed between a wall of the wellbore and
an outer surface of the concentric drill string at a position above the zone
to prevent the flow of cement therethrough from the zone; and
= sealing off the other of the inner or annular conduits of the concentric
drill
string to prevent the flow of cement therethrough from the zone.
A further embodiment of the method comprises adding a cementing plug to the
unsealed conduit after all the cement has been pumped therethrough and then
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pumping a first fluid through the unsealed conduit after the addition of the
cementing plug to assist in pushing the cement through the unsealed conduit
and
into the zone in the wellbore formation. In a preferred embodiment, the
cementing plug is prevented from exiting into the wellbore.
A further embodiment of the method comprises opening the sealed conduit and
pumping a second fluid therethrough such that the second fluid is reverse
circulated back up the unsealed conduit thereby removing the cementing plug
and first fluid from the unsealed conduit to the surface of the wellbore.
A further embodiment of the method comprises opening the sealed conduit and
adding curing agents therethrough. Curing agents include various chemicals and
other additives known in the art for curing cement as well as a variety of
gases
such as air, nitrogen and carbon dioxide that are also used in the industry
for
curing cement.
In one embodiment of the method, a cementing apparatus of the present
invention comprising an isolation cementing tool and a cementing flow control
means can used. The cementing apparatus is placed at or near the bottom of
concentric tubing or drill pipe and lowered into the wellbore until the
isolation tool
is slightly above the zone to be cemented. When the cementing process
commences, or shortly thereafter, the isolation cementing tool is put in the
closed
position, meaning that the packer means is expanded to prevent the flow of
cement back to the surface between the outer annulus between the concentric
tubing or drill pipe and the wellbore.
By way of example, cement is pumped down the inner string of the concentric
drill string, through the center tube of the isolation cementing tool and
ultimately
through the center tube of the cementing flow control means and into the
formation. A cement plug of a type well known in the art is then inserted into
the
inner string and "chased" with a first fluid such as water, gas, air, etc.,
which first
fluid is also pumped through the inner string, etc.
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The insertion of the cement plug and the subsequent pumping of first fluid
force
the cement out through the bottom of the cementing flow control means and into
the formation. In this embodiment, it is desirable to prevent the flow of
cement
back up through the annular conduit of the concentric tubing or drill pipe to
the
surface so the cementing flow control means has a means for stopping or
regulating flow located in the annular conduit thereof. For example, when the
means for stopping or regulating flow comprises at least one check valve of a
kind described above, the upward pressure exerted on the check valve, which
upward pressure results from the pumping of the cement through the inner
conduit, will cause the check valve to be in the closed position, thereby
preventing the cement from flowing through the annular conduit to the surface
of
the wellbore. Thus, cement is prevented from flowing up the annular conduit of
the concentric drill string as a result of the upward pressure exerted on the
check
valve in the annular conduit of the cementing flow control means, closing
same.
The cement plug, which preferably has a diameter slightly less than the inner
diameter of the center tube of the cementing flow control means, will
ultimately
hit the portion of the center tube of the cementing flow control means where
the
inner diameter of the center tube is reduced. The plug becomes wedged at that
point such that no further fluid can be pumped therethrough. The first fluid
contained in the inner conduit of the inner string of the concentric drill
string can
then be easily removed by reverse circulating a second fluid such as water,
air,
gas and the like through the annular conduit of the concentric drill string
thereby
forcing the plug to be dislodged and travel up the inner conduit of the inner
string
of the concentric drill string to the surface. Further, any first fluid
present in the
inner string will also be forced up to the surface.
In another embodiment of the method, an open hole annular expandable packer
means known in the art can be used. The annular expandable packer means is
first positioned in the open hole directly above the zone to be cemented and
then
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expanded to be in tight engagement with the wellbore wall. Concentric drill
string
is then inserted into the center of the expandable packer means and is also in
relatively tight engagement with the expandable packer means. In this
embodiment, concentric drill string further comprises a means for stopping or
regulating flow positioned at or near its bottom in either the annular conduit
or the
inner conduit to prevent the flow of cement therethrough from the zone.
The invention has one or more of the following advantages over current
cementing methods:
= Cementing back to surface isn't required;
= Less damage to producing formations from the lower hydrostatic cement
weight;
= Less cement in the formation for fracture treatment to deal with;
= No need to run a string of casing, cementing shoe and float equipment
= Much less cement is needed;
= The main portion of the well can be drilled with the same hole diameter;
= Chemicals to strength and accelerate the curing of the cement can be
added through the concentric drill string, preferably through the annular
conduit;
= Loss circulation material can be added through the concentric drill string,
preferably through the annular conduit;
= Single or multiple zones can be cemented off to prevent fluid invasion or
unconsolidated materials from plugging the well bore;
= Significant cost savings on cementing time, actual cement and casing
costs;
= When water is used as the "chasing" fluid, water is conserved by
collecting it through the concentric drill string, preferably out through the
inner string, to the surface prior to removing the concentric drill string;
= Lower productive zones can be completed with larger diameter casing,
liners or left open hole;
CA 02541318 2006-03-27
= Compressed air can be blown down the concentric drill string, either
through the annular conduit or through the inner string to greatly reduce
the curing time of the cement;
= No casing shoe, float equipment and cement plug to drill out; and
= Well abandonment programs can be done much quicker and cheaper;
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 is a schematic of an embodiment of an isolation cementing tool of the
present invention.
Figure 2 is a vertical sectional view on and enlarged scale of the isolation
cementing tool shown in Figure 1.
Figure 3a and 3b is a schematic of the isolation cementing tool of Figure 1 in
the
open position and closed position, respectively.
Figure 4a is a vertical sectional view of an embodiment of a cementing flow
control means with cement flowing down the center tube and means for stopping
or regulating flow comprising a check valve in the closed position.
Figure 4b is a cross-sectional view of the cementing flow control means of
Figure
4a taken along line I-I showing check valve in the closed position.
Figure 4c is a vertical sectional view of the cementing flow control means of
Figure 4a, in the displacement position, showing check valve in the open
position
and compressed fluid being delivered down the annular conduit for pushing the
cement plug and water up the center tube to the surface.
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Figure 5a is a vertical sectional view of another embodiment of a cementing
flow
control means with cement flowing down the center tube and means for stopping
or regulating flow comprising two check valves in the closed position.
Figure 5b is a vertical sectional view of the cementing flow control means of
Figure 5a, in the displacement position, showing the two check valves in the
open position and compressed fluid being delivered down the annular conduit
for
pushing the cement plug and water up the center tube to the surface.
Figure 6 is a vertical sectional view of an embodiment of a cementing
apparatus
of the invention assembled on concentric drill string.
Figure 7 is a schematic of the surface and downhole equipment involved in
cementing a wellbore where casing has been run in the wellbore.
Figure 8 is a vertical sectional view of an embodiment of a cementing
apparatus
of the invention when using concentric coiled tubing.
Figure 9 is a vertical sectional view showing the connection of a single wall
high-
pressure cement pumping hose to concentric drill string.
Figure 10 is a vertical sectional view showing the connection of a double wall
high-pressure cement pumping hose to concentric drill string.
Figure 11 is a schematic illustration of a concentric coiled tubing unit
pumping
cement down a wellbore.
Figure 12 is a vertical sectional view of another embodiment of the cementing
system of the present invention.
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DETAILED DESCRIPTION
The cementing apparatus and method will be described with reference to the
following preferred embodiments.
Figure 1 schematically illustrates an embodiment of an isolation cementing
tool
30 and means for attaching the tool between two pieces of concentric drill
string
45 and 47. Preferably, isolation cementing tool 30 is attached to concentric
drill
string 45 and 47 such that the isolation cementing tool 30 is position the
proper
distance from the bottom of the wellbore to allow the desired zone to be
properly
cemented.
Concentric drill string 45 and 47 both comprise an inner string 57 and an
outer
string 59, forming an annular conduit 16 therebetween. Concentric drill string
45
and 47 are designed such that at one end of the concentric drill string is a
threaded pin end and at the other is a threaded box end. Thus, pieces of the
concentric drill string can be connected end to end by screwing the thread pin
end of the new piece of concentric drill string to be added into the box end
of the
drill string below. It is understood that concentric drill string could also
be a
continuous length of concentric coiled tubing having an inner coiled tube and
an
outer coiled tube in which case isolation cementing tool would be operably
attached to the end thereof by coupling means known in the art for coupling
downhole tools to coiled tubing.
As can be seen in Figure 1, concentric drill string 45 has threaded pin end 31
at
its bottom end and concentric drill string 47 has threaded box end 35 at its
top
end. Isolation cementing tool 30 is adapted to be inserted between concentric
drill string 45 and 47 by means of threaded box end 37 and threaded pin end
33.
Thus, threaded pin end 31 of concentric drill string 45 screws into threaded
box
end 37 and threaded pin end 33 screws into threaded box end 35 of concentric
drill string 47. It is anticipated that in some instances concentric drill
string 47
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may only be a short piece of concentric drill string, e.g., it may not be a
complete
length of concentric drill pipe as is known in the art. Isolation cementing
tool 30
further comprises a packer means 39 surrounding the isolation cementing tool,
the operation of which will be described in more detail below.
With reference to Figure 2, isolation cementing tool 30 further comprises a
center
tube 34, an outer casing 32, an annular conduit 36 between the center tube and
outer casing, an inner conduit 38, and a packer means 39 surrounding said
outer
casing 32. When isolation cementing tool 30 is inserted between concentric
drill
string 45 and 47, the center tube 34 of the isolation cementing tool 30 is in
fluid
communication, i.e., via inner conduit 38, with the inner string 57 of the
concentric drill string 45 and 47 and the annular conduit 36 of the isolation
cementing tool 30 is in fluid communication with the annular conduit 16 of the
concentric drill string 45 and 47.
In one embodiment, packer means 39 can be expanded or contracted by means
of an electric current flow path. In another embodiment, the packer means
comprises an inflatable ring, which can be inflated by pumping various types
of
fluid into and out of the ring, as is known in the art.
Figures 3a and 3b schematically illustrate the isolation cementing tool
attached to
the concentric drill string in the open and closed position, respectively,
during
cementing operations. When packer means 39 is contracted or deflated as
shown in Figure 3a, the tool is in the open position and fluids can flow
freely
through the wellbore annulus 43 formed between the outer wall of the outer
string
59 of the concentric drill string and formation wall 41. When packer means 39
is
expanded or inflated as shown in Figure 3b, the packer means is forced against
formation wall 41 thereby closing off annulus 43 to fluid movement above and
below packer means 39.
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Figure 4a is a vertical sectional view of one embodiment of a cementing flow
control means 10, which forms part of the cementing apparatus of the
invention.
Cementing flow control means 10 comprises a center tube 4 and an outer casing
2, forming an annular conduit 7 therebetween. Cementing flow control means
further has a means for stopping or regulating flow comprising a check valve 3
which is shown situated within the annular conduit 7 in this particular
embodiment. It is understood that in an embodiment where it is desirable that
cement is pumped down the annular conduit of the concentric drill sting,
cementing flow control means would comprise a means for stopping or regulating
flow in the inner conduit 1 of the center tube 4. For example, in this
embodiment,
means for stopping or regulating flow may comprise a ball-type check valve or
a
single disc swing valve. Check valves useful in downhole tools are well known
in
the art to allow fluid or gas to flow through tools in only one direction.
It can be seen in Figure 4a that the inner diameter of the center tube 4 is
reduced
at the bottom end thereof. Thus, the inner wall diameter at the bottom end is
less
than the diameter of the rest of the center tube 4. This area of reduced
diameter
is often referred to in the art as a stinger and is designated element 99.
Figure
4a shows cement 9 being pumped through the inner conduit 1 of center tube 4.
Annular conduit 7 is closed off at the bottom of the cementing flow control
means
by check valve 3 being in the closed position, thereby preventing cement 9
from
flowing up annular conduit 7. Cementing flow control means 10 further
comprises threaded box end 52 so that this end can be attached to either the
threaded pin end of a piece of concentric drill string or directly attached to
the
threaded pin end 33 of isolation cementing tool.
When the cementing flow control means 10 is properly connected, it is
understood that center tube 4 of the cementing flow control means 10 is in
fluid
communication with the inner string of concentric drill string and the center
tube
of the isolation cementing tool, and that annular conduit 7 of the cementing
flow
CA 02541318 2006-03-27
control means 10 is in fluid communication with the annular conduit of
concentric
drill string and the annular conduit of the isolation cementing tool.
Figure 4b is a cross-sectional view of the cementing flow control means of
Figure
4a where check valve 3 is in the closed position and therefore closing or
sealing
off the entire annular conduit 7. In this embodiment, check valve 3 comprises
two C-shaped half-circle disks 15 and 15' held together by hinges 11 and 11'
such that the half-circle disks fold together upon positive flow (i.e., when
pumping
a second fluid down the annular conduits) and retract to a full-circle to
close
against reverse flow when no fluid is being pumped down the annulus (i.e.,
during the pumping of cement through the inner conduits).
Figure 4c is a vertical sectional view of cementing flow control means 10
during
the displacement/removal of fluid 79 operation. Here, a first fluid 79 such as
water has already been pumped through the inner conduit 1 to chase cement
plug 5 to the bottom of the cementing flow control means, thereby forcing
essentially all of the cement into the formation. During the displacement
operation, a second fluid 13 such as compressed air is pumped down the various
annular conduits and reverse circulated up through the various inner conduits.
The second fluid 13 displaces both cement plug 5 and fluid 79, which are both
eventually forced to the surface of the wellbore where each can be collected.
Fluid 79 can be reused in the cementing process, which is particularly useful
when fluids such as water are only available in scarce quantities.
When the pressure of the second fluid 13 such as compressed air is exerted on
check valve 3, the check valve is forced in the open position, i.e., the two
half-
circle disks fold towards one another thereby allowing for the passage of
second
fluid 13 through the annular conduit 7 and up through inner conduit 1, as
shown
by the arrows in Figure 4c. Thus, air 13 eventually displaces both cement plug
5
and fluid 79 up through the center (inner conduit) of the concentric drill
string to
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the surface. This both eliminates the necessity to drill out the cement plug
and
conserves fluids such as water.
Once cementing is completed and the cement plug and excess water removed,
isolation cementing tool 30 is placed back in the open position, i.e., packer
means is deflated as shown in Figure 2, and the concentric drill string is
tripped
out of the well bore. In a preferred embodiment, isolation cementing tool 30
is
put in the open position and concentric drill string 47 is pulled up above the
cement in the well bore. Isolation cementing tool 30 is then placed in the
closed
position and compressed air or other gas is pumped down annular conduits 16,
36 and 7 to reduce the amount of time for the cement to cure so drilling or
other
operations may resume.
Figure 5a is a vertical sectional view of another embodiment of a cementing
flow
control means 10, which forms part of the cementing apparatus of the
invention.
In this embodiment, cementing flow control means 10 comprises a means for
stopping or regulating flow, which flow means comprises more than one check
valve. Check valve 3 is positioned near the bottom of the cementing flow
control
means and check valve 3' is located near the top of cementing flow control
means 10. Having a means for stopping or regulating flow comprising a
plurality
of check valves ensures that if one check valve fails, there are other check
valves operable to prevent the flow of cement therethrough to the surface of
the
wellbore.
Figure 5b is a vertical sectional view of the cementing flow control means 10
of
Figure 5a during the displacement operation as described above. Figure 5b
shows both check valve 3' and check valve 3 in the open position as a result
of
the flow of a second fluid 13 such as compressed air through the annular
conduit
7.
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Figure 6 illustrates an embodiment of an assembled cementing apparatus of the
present invention. Isolation cementing tool 30 is shown operably attached to
concentric drill string 45 by means of threads as described above. It can be
seen
that annular conduit 16 of concentric drill string 45 is in fluid
communication with
annular conduit 36 of isolation cementing tool 30 and that inner conduit 19 of
concentric drill string 45 is in fluid communication with inner conduit 38 of
isolation cementing tool 30. In this embodiment, cementing flow control means
is directly attached to the end of isolation cementing tool 30 by thread
means.
It can be seen that annular conduit 7 of cementing flow control means 10 is in
10 fluid communication with annular conduit 36 of the isolation cementing tool
30
and that inner conduit 1 of cementing flow control means 10 is in fluid
communication with inner conduit 38 of isolation cementing tool 30.
In operation, in one embodiment of the invention, cement 9 is first pumped
through inner conduit 19 of inner string 57, then through inner conduit 38 of
isolation cementing tool 30, and finally through inner conduit 1 of cementing
flow
control means 10. Isolation cementing tool is in the closed position. Cement
plug 5, which has on outside diameter slightly smaller than the inner diameter
of
the inner string 57, the inner diameter of center tube 34 and the largest
inner
diameter of center tube 4, but larger than the diameter of stinger 99, is
inserted
through inner string 57 and "chased" with a first fluid such as air, gas or
water 79.
The pumping pressure of first fluid 79 pushes cement plug 5 down to the bottom
of the cementing flow control means 10 and thereby forces cement 9 out into
the
wellbore. The pressure ultimately forces cement 9 past formation wall 41 and
into the formation itself causing that part of the formation to become sealed
off.
Some of the cement 9 will be forced up outer annulus 43 but flow will be
stopped
when cement 9 reaches the bottom of inflated/expanded packer means 39 (the
closed position). Cement 9 is further prevented from returning up annular
conduit 7, and subsequently up annular conduit 16 of concentric drill string
45 to
the surface, by means of check valves 3 and 3' sealing off the annular conduit
7
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CA 02541318 2006-03-27
as a result of the upward pressure which results when pumping down cement 9
and fluid 79 through the various inner conduits. In the alternative, check
valves 3
and 3' could be placed in the closed position prior to the commencement of
cementing by an actuating means known in the art.
Cement plug 5, which follows cement 9, is eventually chased down by first
fluid
79 to the bottom of cementing flow control means 10. As previously mentioned,
the inner diameter of center tube 4 is reduced near its bottom forming stinger
99
so that travel of cement plug 5 is stopped. At this point, essentially all of
the
cement 9 will have been forced out of the various inner conduits and into the
formation, leaving most of first fluid 79 still contained in the inner conduit
of inner
string 57 of the concentric drill string 45.
At this point, chemicals or other additives to strengthen or speed up the cure
time
for the cement 9 can be pumped down annular conduit 16 by applying downward
pressure to both check valve 3' and check valve 3 thereby opening them to
allow
the chemicals or additives to reach the cement 9. Also, a drying gas such as
air,
nitrogen, carbon dioxide, etc., can be pumped down annular conduit 16 to speed
up the cement curing process. In some circumstances it may be desirable to
raise the cementing apparatus above the newly deposited cement to allow
enough room to deliver the air, nitrogen, carbon dioxide, etc. for curing the
cement. Thus, packer means 39 will need to be contracted, i.e., put in the
open
position, the apparatus moved up hole, and then packer means 39 reset, i.e.
expanded again to the closed position. Curing gas is then delivered through
the
annular conduit in this embodiment.
Further, first fluid 79, which has essentially been contained in the various
inner
conduits, can now be removed by reverse circulating a second fluid such as air
or other fluid down annular conduit 16 of concentric drill string 45, through
the
annular conduit 36 of isolation cementing tool 30 and through annular conduit
7
of cementing flow control means 10 and up through the center of the center
tube
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4 of cementing flow control means 10, the center tube 34 of the isolation
cementing tool 30 and the inner string 57 of concentric drill spring 45,
thereby
forcing out the first fluid 79 which can then be collected at the surface of
the well.
Figure 7 illustrates another embodiment of the invention wherein casing is
first
placed in the wellbore. Figure 7 shows the surface equipment required to pump
cement down a well bore. Casing 69 is run in the wellbore between formation
walls 41, thereby forming annulus 129 between the casing 69 and formation wall
41. Cement 9 is pumped from surface by cement pump 101 down inner tube 57
of concentric drill string 45, followed by cement plug 5 and fluid 79.
Isolation
cementing tool 30 is in the closed position, i.e., packer means 39 is in the
expanded position and abuts against the inside wall of casing 69. When
isolation
cementing tool 30 is in the closed position, this allows both the pumping
pressure
and the hydrostatic weight of the cement 9 and fluid 79 to push cement 9 up
annulus 129 to the surface of the wellbore. As previously explained, cementing
flow control means 10 prevents cement 9 from entering annular conduit 16 of
the
concentric drill string 45.
Once the cement 9 returns to surface, displacement operations as shown in
Figures 4c and 5b and described above commence. Thus, no casing shoe, float
equipment and cement plug are left in the well bore that have to be drilled
out
when drilling operations resume.
Figure 8 is a vertical sectional view of another embodiment of a cementing
apparatus of the present invention using concentric coil tubing 12. Concentric
coiled tubing 12 comprises inner tube 14, which provides inner conduit 20 for
pumping cement and water, and outer tube 18, wherein outer tube 14 and inner
tube 12 form an annular conduit 17 therebetween for pumping air/fluid during
the
displacement operations.
CA 02541318 2006-03-27
Isolation cementing tool 30 is attached to concentric coiled tubing 12 by
coupling
or connecting means 21, as known in the art for connecting downhole tools to
coiled tubing, to be in fluid communication with concentric coiled tubing 12
as
previously described with drill pipe. A length of concentric coiled tubing 112
is
routinely attached at the end of isolation cementing tool 30 via another
connecting means 23 known in the art. The length of concentric coiled tubing
112 is determined based on the length of the zone to be cemented.
Cementing flow control means 10 is attached to the free end of concentric
coiled
tubing 112 by connecting means 62 as known in the art. As previously
mentioned, the inner diameter of the center tube 4 of the cementing flow
control
means 10 is reduced, forming stinger 99. As mentioned, this reduction in the
inside diameter of the center tube prevents cement plug 5 from passing through
the center tube and into the wellbore.
Electrical cable 22 provides electric current to operate the isolation
cementing
tool 30 by expanding and contracting packer means 39. Other means of
operating isolation cementing tool 30 could include fiber optic cables, radio
frequency, electric magnetic or small diameter capillary tubes which transmit
hydraulic or pneumatic pressure.
Figure 9 is a vertical sectional view showing the connection of a single wall
high-
pressure cement pumping hose 26, which can be used to pump cement 9
through the inner conduit 19. Cement pumping hose 26 is connected to inner
string 57 of concentric drill string 45 by connecting means 63. Preferably,
the
annular conduit 7 is sealed off prior to pumping cement 9 down the inner
string
57 by means of donut spacer 31. It is understood that donut spacer 31 could be
a separate element or could be an integral part of high-pressure cement
pumping
hose 26. Cement 9 is pumped down the inner string 57 through inner conduit 19
to the desired depth. Cementing flow control means 10 (not shown) prevents
cement 9 from flowing back up the annular conduit 7.
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Figure 10 is a vertical sectional view of another embodiment of the invention
showing the connection of a double-walled high-pressure cement pumping hose
126 to concentric drill string 45 which can be used for both delivering cement
and
chasing fluid and also during the displacement of chasing fluid operation. Pin
end 31 of double-walled high-pressure cement pumping hose 29 connects to box
end 35 of concentric drill string 45 by means of threads as previously
described.
During displacement operations, fluid such as air 13 is reverse circulated
through
annular conduit 7 of concentric drill string 45 and up through inner conduit
1,
which pushes cement plug 5 and chasing fluid 79 back to surface.
In an embodiment as shown in Figure 11, truck 101 comprises a cement tank
114 for holding cement, a fluid tank 112 for holding fluid such as water,
which is
used to chase the cement and cement plug to the bottom of the cementing
apparatus, and an air compressor 118 for delivering compressed air for
displacing the chasing fluid. Truck 101 further comprises a pumping mechanism
(not shown) and a valve manifold system (not shown) both of which are
connected to cement tank, water tank and air compressor by double-wall cement
pumping hose 29. Valve manifold system operates to switch between pumping
cement, pumping fluid such as water and pumping air.
Double-wall cement pumping hose 29 connects to concentric coiled tubing 12,
which is wrapped around reel 116 on coiled tubing truck 107. In operation,
cement 9 is pumped via pumping mechanism through hose 29 and ultimately
through either the annular conduit or inner conduit of the concentric drill
string 12.
Cement 9 is pushed to the bottom of wellbore 115 by adding cement plug (not
shown) and pumping fluid such as water from fluid tank 112. This forces cement
9 to be squeezed through formation wall 41 into a fluid zone of the formation
required to be sealed off with cement. Once cement 9 has cured or set, it then
prevents formation fluid 111 from entering wellbore 115.
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Surface blowout preventor (BOP) 109 provides a surface seal for concentric
coiled tubing 12 so that pumping pressure can deliver cement 9, water or air
down to the wellbore 115 to prevent formation fluid 111 from entering wellbore
115. It can be seen from Figure 11 that surface casing 69 has previously been
cemented in place and the rest of wellbore 115 has been drilled open hole.
Once cementing has been completed, isolation cementing tool 30 is placed in
the
open position by contracting packer means 39 and concentric coiled tubing 12
and cementing apparatus are pulled up several feet from the top of the cement
deposited in the wellbore 115. Then, isolation cementing tool 30 is put back
in
the closed position by expanding packers means 39 at which point displacement
operations are commenced.
Compressed air 13 is now pumped through annular conduit 17 to first assist in
drying cement 9 and then to push cement plug and chasing fluid back to the
surface where it is returned to fluid tank 112. It is understood that, in
addition to
compressed air, other chemicals, loss circulation materials and other fluids
can
also be pumped through annular conduit 17.
Figure 12 is a vertical sectional view of another embodiment of the present
invention. In this embodiment, a cementing system is provided for carrying out
the cementing method of the present invention comprising an open hole annular
packer means 200, for example, a TAM International inflatable Casing Annulus
Packer (CAPTM). The packer means is shown in the expanded (inflated) or
closed position. As shown in Figure 12, packer means 200 abuts the wellbore
walls 41. Concentric drill string 45, comprising inner string 57 having an
inner
conduit 19 and outer string 59 forming annular conduit 16, has an outside
diameter which allows it to fit snugly within the center of the annular packer
means 200. In the alternative, an expandable packer means can be provided
which is adapted to surround the outside of the outer string and which can
then
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be lowered down hole together with the concentric drill string for expansion
when
the zone to be cemAted is reached.
In Figure 12, concentric drill string 45 further comprises valve means 3,
which, in
this embodiment, is shown in the closed position within the annular conduit
16.
Concentric drill string optionally comprises a stinger 199 situated at or near
the
bottom of the inner string 57. In operation, cement 9 is pumped through inner
conduit 19 and into the zone 210 to be cemented. Annular packer means 200
and valve means 3 prevents cement 9 from going up the outer annulus 43 and
the annular conduit 16, respectively.
In an embodiment of the invention (not shown) where cement and chasing fluid
is
delivered through the annular conduit of concentric drill string, it is the
radius of
the annular conduit of the cementing fluid control means which is reduced,
thereby forming an annular conduit stinger. In this embodiment, a donut shaped
cement plug, which has a radius small enough to freely slide through the
various
annular conduits but large enough that it can not get passed the annular
conduit
stinger of this embodiment of the cementing fluid control means is used. Fluid
such as water is then pumped through the annular conduits to chase down the
donut shaped cement plug until it gets lodged in the stinger. Compressed fluid
such as compressed air is then pumped through the various inner conduits to
force the donut shaped cement plug and chasing fluid back to the surface. In
this
embodiment, the cementing fluid control means comprises a plurality of check
valves situated in the inner tube rather than the outer conduit.
In an embodiment where reverse circulating cementing operations are taking
place within zones containing hydrocarbons, a surface and downhole well
control
system is added for safety reasons to prevent the flow of hydrocarbons to the
surface. Examples of cementing operations where well control may be needed
are during abandonment of a wellbore, when trying to stop a loss circulation
problem, and when squeezing a wet zone or a depleted zone in a multi - zone
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CA 02541318 2006-03-27
well. During these reverse circulation cementing operations, the well could
"kick" and without the well control downhole and at surface a blow out
situation
could arise. Examples of surface flow control means and downhole flow control
means that can be used with concentric drill string are given in U.S. Patent
No.
6,854,534 and U.S. Patent No. 6,892,829, both of which are incorporated herein
by reference.
