Note: Descriptions are shown in the official language in which they were submitted.
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ZERO DRILL COMPLETION AND PRODUCTION SYSTEM
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to petroleum production wells. More
particularly, the invention relates to well completion and production methods
and
apparatus.
Description of the Prior Art
The process and structure by which a petroleum production well is
prepared for production involves the steps of sealing the production zone from
contamination and securing production flow tubing within the well borehole.
These
production zones are thousands of feet below the earth's surface.
Consequently, prior
art procedures for accomplishing these steps are complex and often dangerous.
Any
procedural or equipment improvements that eliminate a downhole "trip", is
usually a
welcomed improvement.
Following the prior art, production tube setting and opening are
separate "trip" events. First, the wall casing liner is secured by cementing
the
production string is then positioned where desired within the borehole and the
necessary sealing packers set by fluid pressure internally of the tubing bore.
After the
packers are set, a cementing circulation valve in the production tube assembly
is
opened by tubing bore pressure and annulus cement is pumped into position
around
the production tubing and above the production zone upper seal packer.
This procedure leaves a section of cement within the tubing below the
cementing valve that blocks the upper tubing bore from production flow. The
blockage is between the upper tubing bore and the production screen at or near
the
terminal end of the tubing string. Pursuant to prior art practice, the
residual cement
blockage is usually removed by drilling. A drill bit and supporting drill
string must be
lowered into the well, internally of the production tubing, on a costly,
independent
"trip" to cut away the blockage.
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SUMMARY OF THE INVENTION
An objective of the present invention is to position well production
tubing within the wellbore, secure the tubing in the well by cementing, and
open the
tubing to production flow in one downhole trip. In pursuit of this and other
objectives
to hereafter become apparent, the present invention includes a production
tubing
string having the present well completion tool assembly attached above the
production
screen and casing shoe.
This completion tool assembly includes an alignment of four basic
tools in serial downhole order. At the uphole end of the alignment is a
pressure
actuated cementing valve followed by an external casing packer. Below the
casing
packer is a pressure actuated production valve and below the production valve
is a
bore plug landing collar
With the tubing string downhole and the open hole production screen
located at the desired position within the well production zone, an opening
plug is
deposited in the tubing bore at the surface and pumped by water, other well
fluid or
finishing cement down against the plug landing collar. Upon engaging the
landing
collar, the plug substantially seals the tubing bore to facilitate dramatic
pressure
increases therein. Actuated by a pressure increase within the tubing bore
column, the
external casing packer is expanded to block the borehole space annulus between
the
raw borehole wall and the packer body. An additional increase in pressure
slides the
opening sleeve of the pressure activated cementing valve into alignment of the
internal and external circulation ports. Upon alignment of the circulation
ports, tubing
bore fluid such as cement is discharged through the ports into the wellbore
annulus
space. Due to the presence of the expanded external casing packer below the
circulation ports, the annulus cement must flow up-hole and around the tubing
above
the packer.
When the desired quantity of cement has been placed in the tubing bore
at the surface, the fluidized cement within the tubing bore column is capped
by a
closing pump-down plug. Water or other suitable well fluid is pumped against
the
closing plug to drive the remaining annulus cement through the circulation
ports. At
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the circulation port threshold, the closing plug engages a plug seat on the
closing
sleeve of the pressure actuated cementing valve. With a first pumped pressure
increase acting on the closing plug seat, the cementing valve closing sleeve
slides into
a circulation port blocking position. A second pressure increase that is
normally
greater than the first develops a force on the plug seat of such magnitude as
to shear
the seat ring retaining screws. When structurally released from the valve
closing
sleeve, the closing plug and plug seat impose a piston load on the short
cement
column supported by the opening plug and plug landing collar. This column load
is
converted to fluid pressure on the pressure activated production valve to
force a fluid
flow opening through the valve. When the pressure activated production valve
opens,
the residual cement column is discharged through the open valve below the
packer.
Although the residual cement column is discharged into the production
zone bore, the absolute volume of cement in the column is dispersed as
insignificant.
As the closing plug is driven by the finishing fluid through the central
bore of the production valve past the valve opening, the finishing fluid,
water or light
solvent, rushes through the valve opening to flush it of residual cement and
debris. At
this point, a clear production flow path from the production zone into the
production
tubing bore is open. When pressure on the finishing fluid is released,
upflowing
production fluid sweeps the residual finishing fluid out of the tubing bore
ahead of the
production fluid flow.
In accordance with one aspect of the present invention there is
provided a method of producing a well comprising the steps of-.
a) positioning well fluid production tubing within a well borehole in
flow communication with a well production zone;
b) cementing said production tubing within said well borehole above
said well production zone by directing cement through a cementing valve having
a
cement flow channel from an internal pipe bore into a surrounding well
annulus, said
flow channel being opened by a fluid pressure displaced first sleeve element
and
closed by a fluid pressure displaced second sleeve element ;
c) purging substantially all cement from said internal bore by fluid
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displacement; and
d) opening the internal pipe bore to fluid flow from said production
zone by fluid displacement within said internal pipe bore.
In accordance with another aspect of the present invention there is
provided a method of completing a well comprising the steps of
a) assembling a well fluid production string comprising a pressure
activated cementing valve, an external casing packer below said cementing
valve, a
pressure activated production valve below said packer and a plug seal
operatively
combined with production tubing, said plug seal being positioned between said
production valve and a point of well fluid entry into said production tubing;
b) positioning said point of well fluid entry within said well at a
desired well fluid production location;
c) delivering a pump-down plug into said plug seal;
d) increasing fluid pressure within said production tubing to inflate
said external casing packer;
e) increasing fluid pressure within said production tubing to open said
pressure activated cementing valve;
fj pumping a desired quantity of borehole cement down said tubing and
through said open cementing valve;
g) delivering a closing pump-down plug against said pressure activated
cementing valve to close said cementing valve;
h) increasing fluid pressure within said production tubing to open said
production valve;
i) displacing said closing pump-down plug from obstructing a flowpath
through said production valve; and
j) producing well fluid through said production tube.
In accordance with yet another aspect of the present invention there is
provided a well completion tool comprising the combination of
a) a cementing valve having a cement flow channel from an internal
pipe bore into a surrounding well annulus, said flow channel being opened by a
fluid
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pressure displaced first sleeve element and closed by a fluid pressure
displaced second
sleeve element;
b) a fluid pressure engaged well annulus barrier surrounding said pipe
bore and displaced along said pipe bore from said cementing valve;
S c) a production valve positioned along said pipe bore from said annulus
barrier in a direction opposite from said cementing valve, said production
valve
having a rupture opened flow channel from said surrounding well annulus into
said
pipe bore; and
d) a pipe bore plug seat positioned along said bore from said
production valve in a direction opposite from said annulus barner.
In accordance with still yet another aspect of the present invention
there is provided a well production string comprising a production tube having
an
internal flow bore, said production tube suspending the operative assembly of:
a) a cementing valve having a cement flow channel from an internal
pipe bore into a surrounding well annulus, said flow channel being opened by a
fluid
pressure displaced first sleeve element and closed by a fluid pressure
displaced second
sleeve element;
b) a fluid pressure engaged well annulus barner surrounding said pipe
bore and displaced along said pipe bore from said cementing valve;
c) a production valve positioned along said pipe bore from said annulus
barrier in a direction opposite from said cementing valve, said production
valve having
a rupture opened flow channel from said surrounding well annulus into said
pipe bore;
and
d) a pipe bore plug seat positioned along said pipe bore from said
production valve in a direction opposite from said annulus barrier.
BRIEF DESCRIPTION OF THE DRAWINGS
A detailed description of the invention following hereafter refers to the
several figures of the drawings wherein like reference characters in the
several figures
relates to the same or similar elements throughout the several figures and:
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FIG. 1 is a schematic well having the present invention in place for
completion and production;
FIG. 2 is a partial section of the present well completion tool assembly
in the run-in condition;
FIG. 3 is a partial section of a pressure actuated cementing valve;
FIG. 4 is a partial section of the present well completion tool assembly
in the packer inflation condition;
FIG. 5 is a partial section of the present well completion tool assembly
in the annulus cementing condition;
FIG. 6 is a partial section of the present well completion tool assembly
in the cement termination condition;
FIG. 7 is a partial section of the present well completion tool assembly
in the production flow opening condition.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The invention utility environment is represented by the schematic of
FIG. 1 which illustrates a well bore 10 that is normally initiated from the
earth's
surface in a vertical direction. By means and procedures well known to the
prior art,
the vertical well bore may be continuously transitioned into a horizontal bore
orientation 11 as desired for bottom hole location or the configuration of the
production zone 12. Usually, a portion of the vertical surface borehole 10
will be
internally lined by steel casing pipe 14 which is set into place by cement in
the
annulus between the inner borehole wall and the outer surface of the casing
14.
Valuable fluids such as petroleum and natural gas held within the
production zone 12 are efficiently conducted to the surface for transport and
refining
through a string of production tube 16. Herein, the term "fluid" is given its
broadest
meaning to include liquids, gases, mixtures and plastic flow solids. In many
cases, the
annulus between the outer surface of the production tube 16 and the inner
surface of
the casing 14 or raw well bore 10 will be blocked with a production packer 18.
The
most frequent need for a production packer 18 is to shield the lower
production zone
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12 from contamination by fluids drained along the borehole 10 from higher
zones and
strata.
The terminal end of a production string 16 may be an uncased open
hole but is often equipped with a liner or casing shoe 20 and a production
screen 22.
In lieu of a screen, a length of drilled or slotted pipe may be used. The
production
screen 22 is effective to grossly separate particles of rock and earth from
the desired
fluids carried by the formation 12 structure and admit the production zone
fluids into
the inner bore of the tubing string 16. Accordingly, the term "screen" is used
expansively herein as the point of well fluid entry into the production tube.
Pursuant to practice of the present invention, a production string 16 is
provided with the present well completion tool assembly 30. The tool assembly
is
positioned in the uphole direction from the production screen 22 but closely
proximate therewith. As represented by FIG. 1, the production packer 18 (if
necessary), the completion tool assembly 30, the production screen 22 and the
casing
shoe 20 are preassembled with the production tube 16 as the production string
is
lowered into the wellbore 10.
With respect to FIG. 2, the completion tool assembly 30 comprises a
pressure activated cementing valve 32, an external casing packer 34, a
pressure
activated production valve 36 and a plug landing collar 38. Each of these
devices may
be known to those of ordinary skill in some modified form or applied
combination.
As shown in greater detail by FIG. 3, the pressure actuated cementing
valve provides circulation ports 40 and 42 through the inside bore wall of the
tool and
the outer tool casing. Axially sliding sleeve 44 is axially positioned to
obstruct a fluid
flow channel between the inner ports 42 and the outer ports 40 for a well run-
in
setting. Down-hole, the sleeve is positionally displaced by a predetermined
high fluid
pressure within the inside bore of the tool from the closed, run-in setting to
a position
at which the inside and outside ports are aligned. When aligned, well cement
may be
pumped from within the internal bore of the tool and tubing string through the
ports
40 and 42 into the well annulus around the tubing string. Use of the term
"cement"
herein is intended to describe any substance having a fluid or plastic flow
state that
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may be pumped into place and thereafter induced to solidify.
Closure of the fluid flow channel through ports 40 and 42 is
accomplished by a second sliding sleeve 46 as illustrated by FIG. 6. A landing
seat
48 for a closure plug 54 is secured to the inside bore wall of the tool by
shear screws
49, for example. Procedurally, the cement slurry tail is capped by the closure
plug 54.
The closing plug is pumped by water or other suitable well working fluid down
the
tubing string bore until engaging the plug landing seat 48. When the plug
engages the
seat 48, fluid pressure in the bore may be increased to 1000 psi, for example,
against
the plug and seat 48 until the closing sleeve 46 slides to the port 40-42
closure
position. Additional pressure against the closing plug and seat 48, 5000 psi,
for
example, is operative to shear the screws 49 and drive the plug and seat out
of the tool
bore.
The external casing packer 34 is any device that creates a seal in the
wellbore annulus around the tube string. A common example of a casing packer
provides an expansible elastomer boot around an internal tube body. An
internal bore
of the tube body is coaxially connected with the production tube string. The
expansible boot is secured to the tube body around the perimeter of the two
circumferential edges. A fluid tight chamber is thereby provided between the
tube
body and the inside surface of the expansible boot. This chamber is connected
by a
check valve controlled conduit to the interior bore of tube body. Hence,
pressurized
fluid within tube body expands the boot against the casing or borehole wall.
The pressure actuated production valve 36 is a coupling device having
an internal sleeve radially spaced inwardly from the exterior jacket to define
a fluid
flow annulus between the interior wall of the valve jacket and the exterior
wall of the
sleeve. This flow annulus is linked to the interior bore of the valve by
pressure
displaced structure such as a pressure ruptured disc or reed to effect a
single acting
flow connection.
The plug landing collar 38 is an extension of the production valve
sleeve that continues an open flow continuity with the production valve
annulus.
Internally of the landing collar is a pump-down plug seat.
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The above described tubing string assembly is lowered into the well
bore 10 with the packers 18 unset and the external casing packer 34 deflated.
The
cementing valve 32 ports 40 and 42 are closed. The production flow screen 22
is
positioned where desired and an opening pump-down plug 50 is placed in the
tubing
string bore to be pumped by well finishing cement down to seating engagement
with
the landing collar 38 as shown by FIG. 4. If desired, the plug SO may also be
transferred downhole by water or other well working fluid. With the plug SO
secure
upon the landing collar plug seat 38, fluid pressure within the tubing bore is
increased
against the opening plug 50 to inflate the packer 34. This event blocks the
well
annulus between the production screen 22 and the cementing valve 32.
Next, fluid pressure within the tubing bore is further increased to shift
the opening sleeve 44 and align the circulation ports 40 and 42. When the
circulation
ports align, cement flows through the ports and up the borehole annulus around
the
production tubing.
The total cement volume requirement for a particular well is usually
calculated with considerable accuracy. Accordingly, when the desired quantity
of
cement has been pumped into the tubing bore, a closing pump-down plug 54 is
placed
in the bore to cap the cement column. Behind the closing pump-down plug 54,
water
or other suitable well working fluid is pumped to complete the cement transfer
and
settle the closing pump-down plug 54 against the cementing valve plug seat 48.
An
increase of tubing bore pressure to 1000 psi, for example, against the plug 54
and seat
48 causes a shift in the valve closing sleeve 46 thereby closing the fluid
communication ports 40 and 42. Thereafter, the tubing bore pressure is
increased
again, to 5000 psi, for example, to shear the retaining screws 49 and release
both the
seat 48 and the closing plug 54. When released, the free piston nature of the
plug and
seat unit drives against the residual cement column that was isolated between
the
opening pump-down plug 50 and the closing pump-down plug 54. Pressure against
the closing pump-down plug 54 is thereby transferred to the residual cement
column
and consequently to the pressure activated production valve 36. Refernng to
FIG. 7,
this increased pressure against the production valve 36 ruptures flow port
closure
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disks to permanently open flow port 56 between a production flow annulus and
the
tubing bore. Continued pressure against the residual cement column purges the
residual cement through the newly opened production valve flow port 56 into
the well
bore below the packer 34.
It will understood by those of skill in the art that the flow port 56 is
configured to bridge the length of the plug 54 whereby cement and well working
fluid
may simultaneously exit the flow port 56 into the wellbore as plug 54 passes
the open
flow ports.
Another active mechanism in the production valve 36 opening is the
seal bias of the plug 54 bore sealing fins. The wiping bias of the fins is
oriented to
seal uphole fluid pressure with the production tube bore from passing between
the fin
and tubing wall. Conversely, when the static pressure within the wellbore is
greater
than the static pressure in the production tube bore, the plug 54 sealing fin
bias will
allow wellbore fluid flow past the fins into the production tube bore. Hence,
it is not
essential for the plug 54 to be pressure driven past the flow port 56 opening.
At this point, the well completion process is essentially complete and
the well is ready to produce. However, some operators may choose to transfer a
cement contamination fluid into the production zone bore the assure a
subsequent
removal of the residual column cement from the well bore.
Having fully described the preferred embodiments of the present
invention, various modifications will be apparent to those skilled in the art
to suit the
circumstances of a particular well and manufacturing capacity. It is intended
that all
variations within the scope and spirit of the appended claims be embraced by
the
foregoing disclosure.
