Note: Descriptions are shown in the official language in which they were submitted.
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CASING DEGASSER TOOL
This application claims the benefit of U.S. Provisional Application No.
60/521,523, filed May 13, 2004.
FIELD OF THE INVENTION
The present invention relates to an apparatus and method useful for well
completion of a wellbore containing hydrocarbons. In particular, the present
invention relates to an apparatus adapted to be inserted into production
piping,
such as casing, slotted liners, or tubing, to control the flow of fluids from
the
reservoir through the production piping during well completion operations and
further relates to a process using said apparatus for running joints of
production
piping into a wellbore to form a completed well.
BACKGROUND OF INVENTION
Current technology uses kill fluids to stop the flow of reservoir fluids (e.g.
hydrocarbons) so that well completion operations such as running production
piping in the wellbore or installing a wellhead assembly at surface can be
accomplished without the presence of hydrocarbons. Conventional kill fluids
known in the art are typically aqueous liquids such as water or weighted
fluids
such as drilling mud. The kill fluid applies a hydrostatic pressure against
the
reservoir fluid, which typically is greater than the pressure exerted by the
reservoir fluid attempting to intrude into the wellbore.
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This overbalanced hydrostatic pressure, however, can cause damage to
reservoirs, in particular, to reservoirs containing swelling clays or
reservoirs
having a pressure well below the hydrostatic pressure of the kill fluid being
used.
Hydrocarbon reservoirs with high permeability and porosity can also be
damaged with the use of kill fluids.
The present invention provides an apparatus and method for carrying out
completion activities without the need to kill the flow of hydrocarbons by
means
of kill fluids.
SUMMARY OF THE INVENTION
A casing degasser tool (CDT) is provided which is adapted to be inserted
into production piping such as casing, slotted liners, or production tubing.
One
CDT embodiment comprises a body having a top end, a bottom end and an
outer surface, and at least one expandable sealing element surrounding a
portion of the outer surface of said body. The expandable sealing element can
be formed from a material such as expandable rubber, rubber and steel,
fiberglass or other composite material, and can be expanded such that it
provides a fluid tight seal with the inside wall of the production piping. For
example, the sealing element can be an inflatable ring wherein the inflatable
ring
expands or contracts by pumping fluids into or out of the inflatable ring.
In another embodiment, the CDT comprises at least one sealing element
surrounding a portion of the outer surface of said body, wherein each sealing
element has a fixed dimension, which dimension depends upon the inner
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diameter of the completion piping for which it is designed. Thus, in this
embodiment, the sealing element dimension can vary for each type of
production tubing but will still provide a fluid tight seal when the CDT is
inserted
therein. Hence, it is understood that the sealing element of the CDT can come
in different sizes to ensure that the CDT always fits snuggly inside the
production piping having a range of different inside diameters.
The body further comprises a connection means located at or near the
top end of the body for connecting a wire line or other pulling device to the
CDT
to assist in positioning the CDT within the production piping and for pulling
the
CDT through the length of the production piping.
In one embodiment, the body further comprises an inner cavity extending
through the bottom end of the body so that the bottom end of the body is in
fluid
communication with the inside of the production piping when the CDT is
inserted
therein. In this embodiment, the body may further comprise a pressure relief
fitting and/or a pressure gauge fitting.
The pressure relief fitting has one end in fluid communication with said
inner cavity and an opposite end for connecting a pipe or hose thereto to
bleed
off hydrocarbons to the surface when necessary during a well completion
operation. A flow prover can also be connected to the pressure relief fitting
instead of a pipe or hose to test for well production capability at the
completion
of running the production piping. The pressure relief fitting further
comprises a
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sealing means for keeping the pressure relief fitting sealed until the pipe,
hose or
flow prover is connected thereto.
Similarly, the pressure gauge fitting has one end in fluid communication
with said inner cavity and an opposite end for connecting a pressure gauge or
other instrumentation package thereto for measuring downhole pressure. The
pressure gauge fitting further comprises a sealing means for keeping the
pressure gauge fitting sealed until the pressure gauge or other
instrumentation
package is connected thereto.
A process of running joints of production piping into a wellbore that
contains flowing hydrocarbons, which uses the CDT of the present invention, is
also provided. The process comprises placing the CDT inside a first joint of
production piping, said production piping having a top end and a bottom end,
and lowing the production piping into the wellbore bottom end first. The CDT
is
preferably positioned near the top end of the first joint of production piping
and at
least one sealing element is in frictional engagement with the inside wall
surface
of the production piping to provide a fluid tight seal.
The process further comprises adding a second joint of production piping,
said second joint of production piping also having a top end and a bottom end,
to
the first joint of production piping by coupling the bottom end of said second
production piping to the top end of the first production piping with coupling
means known in the art. A wire line or other pulling device is then attached
to
the CDT by first passing it through the second joint of production piping and
then
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attaching it to the connection means located at or near the top of the body of
the
CDT.
Finally, the CDT is pulled through the top end of the first joint of
production piping, through the bottom end of said second joint of production
piping and into the second joint of production piping. The wire line or other
pulling device that is connected to the top end of the body of the CDT is then
removed and the process is repeated until all joints of production piping have
been coupled together.
To aid in the pulling of the CDT through the production piping, a lubricant
such as pipe thread dope may be added to the inside surface of the production
piping.
In another embodiment of the process, the CDT can simply remain
positioned in the first joint of production piping at all times during the
addition of
each new joint of production piping and the CDT pulled through all production
piping at once when the well is completed.
In one embodiment, when the running of the production piping is
complete (i.e., all of the joints of production piping have been connected
together), well production capability can be tested by connecting a flow
prover to
the pressure relief fitting of the CDT. The CDT can then be removed by means
of the wire line or other pulling device that is connected to the CDT.
In another embodiment, the process of running production casing into
wellbore further comprises periodically checking the downhole pressure by
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means of a pressure gauge attached to the pressure gauge fitting of the CDT.
In another embodiment, the process further comprises bleeding built up
pressure from the wellbore, should the downhole well pressure starts to become
a concern, by attaching a hose or pipe to the pressure release fitting of the
CDT.
The pressure then can be bled down by attaching the opposite end of the hose
or pipe to a blewie line and allowing the built up hydrocarbons in the well to
flow
into a flare stack, a tank or a pit.
This invention may have one or more of the following advantages over the
use of kill fluids to stop the flow of hydrocarbons during completion
operations:
(1 ) time and money can be saved because there is no need to use kill
fluids;
(2) in low and under pressure reservoirs there is less formation
damage as compared to the damage caused as a result of the
hydrostatic weight of the kill fluid;
(3) in dehydrated and clay swelling reservoirs there are no fluids to
cause damage;
(4) it provides an alternative method to using a snubbing unit;
(5) it allows reverse circulated center discharge drilled wells to be
completed without having to kill the well;
(6) wellbores can be safely bled down prior to the installation of the
wellhead without using kill fluids;
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(7) well production capability can be tested by connecting a flow
prover to the pressure relief fitting at the completion of running the
production piping; and
(8) slotted casing and liners can be run into the wellbore without the
need to kill the well.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 is a schematic of the casing degasser tool of the present
invention.
Figure 2 is a schematic of the casing degasser tool inside a joint of
production piping.
DETAILED DESCRIPTION
Figure 1 schematically illustrates an embodiment of the present invention.
Casing degasser tool 15 comprises a body 7 having a closed top end 2, an open
bottom end 4 and an inner cavity 8. Disposed around the outside surface 13 of
body 7, at or near bottom end 4, are a plurality of sealing elements 11,
formed
from a material such as rubber or the like. When casing degasser tool 15 is
placed inside a joint of production piping, sealing elements 11 provide a
fluid
tight seal with the inside wall of the production piping.
Sealing elements 11 may also be made of expandable rubber and the like
so that sealing element 11 can be expanded by means of pumping fluid or air
therein or by means of an electric current. This assists in the frictional
engagement of the sealing element with the inside wall of the production
piping
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to ensure a fluid tight seal. Further, the sealing element can then be
contracted
slightly to facilitate the pulling of the casing degasser tool 15 through the
production piping.
At or near top end 2 is connection means 1 to which a wire line or other
pulling devices known in the art can be attached for positioning the casing
degasser tool 15 within the joint of production piping and for pulling the
casing
degasser tool 15 through the joint of production piping.
The top end 2 of body 7 further comprises pressure relief fitting 5 having
threaded end 9, which is in fluid communication with the inner cavity 8.
Pressure relief fitting 5 comprises a sealing means (not shown), which seals
the
pressure relief fitting 5 until a pipe, or hose (shown as pipe 19 in Figure 2)
is
connected to pressure relief fitting 5 by thread means. The pressure relief
fitting
5 and pipe or hose connected thereto are used to bleed off hydrocarbons from
the wellbore to the surface of the well, when necessary during a well
completion
operation. It is understood that a flow prover (not shown) or other
instrumentation can also be connected to the pressure relief fitting 5 by
thread
means for testing well production capability after well completion.
Casing degasser tool 15 further comprises pressure gauge fitting 3
having threaded end 10, which is in fluid communication with the inner cavity
8.
Pressure gauge fitting 3 comprises a sealing means (not shown), which seals
the pressure gauge fitting 3 until a pressure gauge or other instrumentation
package is attached thereto by thread means for measuring downhole pressure.
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Figure 2 schematically illustrates casing degasser tool 15 when it is
situated inside production piping 21 and said production piping 21 is situated
within a wellbore. Sealing elements 11 of casing degasser tool 15 are shown in
frictional engagement with the inside wall 23 of production piping 21 to
create a
tight fluid seal. Reservoir hydrocarbons 13 are thus prevented from flowing
out
of production casing 21 by sealing element 11. Further, top end 2 of casing
degasser tool 15 is closed so as to prevent the flow of hydrocarbons through
the
inner cavity 8 of casing degasser tool 15. Finally, pressure gauge fitting 3
and
pressure relief fitting 5 are also in the sealed position, unless pipe,
tubing,
l0 pressure gauges and other instrumentation are connected thereto, and thus
hydrocarbons cannot escape therethrough.
A surface control system comprising a surface blowout preventor (not
shown) can also be used in combination with the present invention. A surface
blow out preventor will prevent the flow of any hydrocarbons that may escape
on
the outside of the production piping through the annulus formed between the
outer wall of the production piping and the wellbore wall during well
completion.
Once a new joint of production piping is added to existing production
piping 21, wire line 6 is fed through the new joint of production piping and
through production piping 21 and attached to connection means 1. Casing
degasser tool 15 is then pulled first through the top of production piping 21
and
then through the bottom of the new joint of production casing so as to
position
casing degasser tool 15 preferably in the upper portion of the new piece of
production casing. It is understood that during the addition of each joint of
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production casing, wire line 6 is first removed and then reattached to pull
the
casing degasser tool 15 into the newly added joint of production piping.
In the alternative, casing degasser tool 15 can remain situated in the first
joint of production piping until all subsequent joints of production piping
have
been added. Wire line 6 is then threaded through all interconnected joints of
production piping and attached to connection means 1. Casing degasser tool 15
is then pulled through all joints of production piping upon well completion.
To facilitate the movement of the casing degasser tool 15 through
production piping, sealing element 11, if expandable, may be slightly
contracted
to allow casing degassing tool 15 to move more freely through the production
piping. In the alternative, if sealing element 11 is not expandable, a
lubricant
such as pipe thread dope may be added to the inside surface of each joint of
production piping to facilitate the movement of the degasser tool 15 through
the
production piping.
Pressure of formation 27 is monitored by connecting a proper pressure
gauge (not shown) to pressure gauge fitting 3. When necessary to bleed off
pressure from formation 27, hose or pipe 19 is connected to pressure relief
fitting 5 and hydrocarbons 13 are flared through a blewie line (not shown)
attached to the opposite end of pipe 19 or put into tank or pit (not shown).
In the
alternative, a flow prover (not shown) can be connected to pressure relief
fitting
5 at the completion of running the production piping to test for well
production
capability.
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While the foregoing is directed to one embodiment of the present
invention, other and further embodiments of the invention may be devised
without departing from the basic scope thereof. It is intended that the
appended
claims cover all such modifications and variations as fall within the true
spirit and
scope of the invention.
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