U.S. patent application number 12/746880 was filed with the patent office on 2010-10-07 for system for drilling a wellbore.
Invention is credited to Jan-Jette Blange, Petrus Cornelis Kriesels.
Application Number | 20100252333 12/746880 |
Document ID | / |
Family ID | 39327250 |
Filed Date | 2010-10-07 |
United States Patent
Application |
20100252333 |
Kind Code |
A1 |
Blange; Jan-Jette ; et
al. |
October 7, 2010 |
SYSTEM FOR DRILLING A WELLBORE
Abstract
A system is disclosed for drilling a wellbore (1) into an earth
formation. The system comprises an expandable tubular element (4)
extending into the wellbore, whereby a lower end portion (11) of
the wall of the tubular element (8) extends radially outward and in
axially reverse direction so as to define an expanded tubular
section (10) extending around a remaining tubular section (4) of
the tubular element. The expanded tubular section is extendable by
downward movement of the remaining tubular section relative to the
expanded tubular section whereby said lower end portion (14) of the
wall bends radially outward and in axially reverse direction.
Inventors: |
Blange; Jan-Jette;
(Rijswijk, NL) ; Kriesels; Petrus Cornelis;
(Rijswijk, NL) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Family ID: |
39327250 |
Appl. No.: |
12/746880 |
Filed: |
December 8, 2008 |
PCT Filed: |
December 8, 2008 |
PCT NO: |
PCT/EP08/66994 |
371 Date: |
June 8, 2010 |
Current U.S.
Class: |
175/424 |
Current CPC
Class: |
E21B 7/20 20130101; E21B
43/103 20130101 |
Class at
Publication: |
175/424 |
International
Class: |
E21B 7/18 20060101
E21B007/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 2007 |
EP |
07122725.0 |
Claims
1. A system for drilling a wellbore into an earth formation,
comprising an expandable tubular element extending into the
wellbore, wherein a lower end portion of the wall of the tubular
element extends radially outward and in an axially reverse
direction so as to define an expanded tubular section extending
around a remaining tubular section of the tubular element, the
expanded tubular section being extendable by downward movement of
the remaining tubular section relative to the expanded tubular
section such that said lower end portion of the wall bends radially
outward and in an axially reverse direction; and a drill string
extending through the remaining tubular section, wherein the
tubular element and the drill string are arranged for transferring
a thrust force from the tubular element to the drill string, and
wherein the drill string includes a jetting head for deepening the
wellbore by jetting a stream of fluid against the bottom of the
wellbore.
2. The system of claim 1, further comprising means for centralising
the jetting head in the remaining tubular section.
3. The system of claim 1 wherein the expanded tubular section has
an outer diameter, and wherein the drill string is provided with a
reamer for reaming the wellbore to at least the outer diameter of
the expanded tubular section.
4. The system of claim 1 wherein the remaining tubular section and
the drill string are arranged for simultaneous lowering in the
wellbore.
5. The system of claim 4, wherein said lower end portion of the
wall is arranged for lowering into the wellbore at substantially
the same speed as lowering of the drill string during drilling of
the wellbore.
6. The system of claim 1 wherein the wall of the tubular element
includes a material susceptible of plastic deformation during said
bending of the wall so that the expanded tubular section retains an
expanded shape as a result of said plastic deformation.
7. The system of claim 1 wherein the remaining tubular section is
subjected to an axially compressive force acting to induce said
downward movement of the remaining tubular section.
8. The system of claim 7, wherein said axially compressive force
results at least partly from the weight of the remaining tubular
section.
9. The system substantially as described hereinbefore with
reference to the drawings.
Description
[0001] The present invention relates to a system for drilling a
wellbore into an earth formation whereby an expandable tubular
element extends into the wellbore.
[0002] The technology of radially expanding tubular elements in
wellbores finds increasing application in the industry of oil and
gas production from subterranean formations. Wellbores are
generally provided with one or more casings or liners to provide
stability to the wellbore wall, and/or to provide zonal isolation
between different earth formation layers. The terms "casing" and
"liner" refer to tubular elements for supporting and stabilising
the wellbore wall, whereby it is generally understood that a casing
extends from surface into the wellbore and that a liner extends
from a certain depth further into the wellbore. However, in the
present context, the terms "casing" and "liner" are used
interchangeably and without such intended distinction.
[0003] In conventional wellbore construction, several casings are
set at different depth intervals, and in a nested arrangement,
whereby each subsequent casing is lowered through the previous
casing and therefore has a smaller diameter than the previous
casing. As a result, the cross-sectional wellbore size that is
available for oil and gas production, decreases with depth. To
alleviate this drawback, it has become general practice to radially
expand one or more tubular elements at the desired depth in the
wellbore, for example to form an expanded casing, expanded liner,
or a clad against an existing casing or liner. Also, it has been
proposed to radially expand each subsequent casing to substantially
the same diameter as the previous casing to form a monobore
wellbore. It is thus achieved that the available diameter of the
wellbore remains substantially constant along (a portion of) its
depth as opposed to the conventional nested arrangement.
[0004] EP 1438483 B1 discloses a system for expanding a tubular
element in a wellbore whereby the tubular element, in unexpanded
state, is initially attached to a drill string during drilling of a
new wellbore section.
[0005] To expand such wellbore tubular element, generally a conical
expander is used with a largest outer diameter substantially equal
to the required tubular diameter after expansion. The expander is
pumped, pushed or pulled through the tubular element. Such method
can lead to high friction forces between the expander and the
tubular element. Also, there is a risk that the expander becomes
stuck in the tubular element.
[0006] EP 0044706 A2 discloses a flexible tube of woven material or
cloth that is expanded in a wellbore by eversion to separate
drilling fluid pumped into the wellbore from slurry cuttings
flowing towards the surface.
[0007] However there is a need for an improved system for drilling
a wellbore whereby an expandable tubular element extends into the
wellbore.
[0008] In accordance with the invention there is provided a system
for drilling a wellbore into an earth formation, comprising
[0009] an expandable tubular element extending into the wellbore,
whereby a lower end portion of the wall of the tubular element
extends radially outward and in axially reverse direction so as to
define an expanded tubular section extending around a remaining
tubular section of the tubular element, the expanded tubular
section being extendable by downward movement of the remaining
tubular section relative to the expanded tubular section whereby
said lower end portion of the wall bends radially outward and in
axially reverse direction; and
[0010] a drill string extending through the remaining tubular
section, wherein the tubular element and the drill string are
arranged for transferring a thrust force from the remaining tubular
section to the drill string, and wherein the drill string includes
a jetting head for deepening the wellbore by jetting a stream of
fluid against the bottom of the wellbore.
[0011] By moving the remaining tubular section downward relative to
the expanded tubular section during drilling, the tubular element
is effectively turned inside out whereby the lower end portion of
the wall of the tubular element is continuously bent radially
outward and in axially reverse direction so that the tubular
element is progressively expanded without the need for an expander
that is pushed, pulled or pumped through the tubular element. In
this manner the expanded tubular section forms a casing or liner
that is installed in the wellbore during the drilling process, so
that a relatively short open-hole section can be maintained during
drilling.
[0012] Furthermore, the thrust force transmitted from the remaining
tubular section to the drill string can be kept small since the
jetting head requires only a small thrust force when compared to
the large thrust force required for drilling with a conventional
drill bit. In view thereof, the downward force that must be exerted
to the remaining tubular section to move it downward includes only
a small component for thrusting the drill string during drilling.
It is thereby achieved that the risk of exceeding the yield
strength of the remaining tubular section is significantly reduced,
when compared to drilling with a conventional drill bit.
[0013] Suitably the system of the invention comprises means for
centralising the jetting head in the remaining tubular section.
[0014] In a preferred embodiment, the drill string is provided with
a reamer for reaming the wellbore to at least an outer diameter of
the expanded tubular section.
[0015] To maintain a short open-hole section while drilling, it is
preferred that the remaining tubular section and the drill string
are arranged for simultaneous lowering in the wellbore whereby, for
example, said lower end portion of the wall is arranged for
lowering into the wellbore at substantially the same speed as the
speed of lowering of the drill string during drilling of the
wellbore.
[0016] It is preferred that the wall of the tubular element
includes a material that is plastically deformed during the bending
process, so that the expanded tubular section retains an expanded
shape as a result of said plastic deformation. Thus, there is no
need for an external force or pressure to be applied to the
expanded tubular section to maintain its expanded form. If, for
example, the expanded tubular section is expanded against the
wellbore wall as a result of said bending of the wall, no external
radial force or pressure needs to be exerted to the expanded
tubular section to keep it against the wellbore wall. Suitably the
wall of the tubular element is made of a metal such as steel or any
other ductile metal capable of being plastically deformed by
eversion of the tubular element. The expanded tubular section then
has adequate collapse resistance, for example in the order of
100-150 bars.
[0017] Suitably the remaining tubular section is induced to move
downward while the expanded tubular section is kept stationary in
the wellbore.
[0018] In order to induce said downward movement it is preferred
that the remaining tubular section is subjected to an axially
compressive force, which at least partly can result from the weight
of the remaining tubular section. If necessary the weight can be
supplemented by an external, downward, force applied to the
remaining tubular section to induce said movement. As the length,
and hence the weight, of the remaining tubular section increases,
an upward force may need to be applied to the remaining tubular
section to prevent uncontrolled bending or buckling of the
wall.
[0019] Suitably the remaining tubular section is axially extended
at its upper end in correspondence with its downward movement. This
is done, for example, by adding tubular portions at the upper end
in any suitable manner such as by welding. Alternatively, the
remaining tubular section is formed as a coiled tubing that is
unreeled from a reel and subsequently inserted into the wellbore.
In this way the process of eversion of the tubular element can be
continued until a desired length of the tubular element is
expanded.
[0020] The invention will be described hereinafter in more detail
and by way of example, with reference to the accompanying drawing
in which:
[0021] FIG. 1 schematically shows a lower portion of a first
embodiment of the system of the invention;
[0022] FIG. 2 schematically shows the first embodiment during
cutting of a tubular element in a wellbore; and
[0023] FIG. 3 schematically shows a lower portion of a second
embodiment of the system of the invention.
[0024] In the drawing and the description, like reference numerals
relate to like components.
[0025] Referring to FIGS. 1 and 2, there is shown a system
including a wellbore 1 extending into an earth formation 2, and an
expandable tubular element in the form of liner 4 extending from
surface downwardly into the wellbore 1. The liner 4 has been
partially radially expanded by eversion of the wall of the liner
whereby a radially expanded tubular section 10 of the liner 4 has
been formed, which has an outer diameter substantially equal to the
wellbore diameter. A remaining tubular section of the liner 4, in
the form of unexpanded liner section 8, extends concentrically
within the expanded tubular section 10.
[0026] The wall of the liner 4 is, due to eversion at its lower
end, bent radially outward and in axially reverse (i.e. upward)
direction so as to form a U-shaped lower section 11 of the liner
interconnecting the unexpanded liner section 8 and the expanded
liner section 10. The U-shaped lower section 11 of the liner 4
defines a bending zone 12 of the liner.
[0027] The expanded liner section 10 is axially fixed to the
wellbore wall 14 by any suitable anchoring means (not shown), or by
frictional forces between the expanded liner section 10 and the
wellbore wall 14 resulting from the expansion process. The U-shaped
lower section 11 of liner 4 is positioned a short distance above
the bottom of the wellbore so that an open-hole wellbore section 13
is defined below the U-shaped lower section 11.
[0028] A drill string 20 extends from surface through the
unexpanded liner section 8 to the bottom of the wellbore 1, with a
jetting head 22 at its lower end. The jetting head 22 comprises a
plurality of jetting nozzles 24 and cutting nozzles 26. The jetting
nozzles 24 are directed so as to eject fluid jets 28 against the
bottom and/or the wall of the wellbore 1. Each fluid jet 28
suitably includes a stream of fluid, e.g. water, with abrasive
particles entrained therein. The cutting nozzles 26 are directed
radially outward from the jetting head.
[0029] The drill string 20 is provided with a guide device 30
having a curved surface portion 32 arranged to transfer a thrust
force from the liner 4 to the drill string 20, and to support and
guide the U-shaped lower section 11 of the liner 4 during eversion
of the liner 4. The guide device 30 is rotatable relative to the
drill string 20 about its central longitudinal axis. Furthermore,
the guide device 30 is collapsible so as to allow it to pass
through the unexpanded liner section 4 (FIG. 2).
[0030] In FIG. 3 is shown the second embodiment, which is
substantially similar to the first embodiment, except that the
cutting head 22 is provided with reamers 33 adapted to ream the
wellbore 1 to a nominal diameter substantially equal to the outer
diameter of the expanded liner section 10. The reamers 33 are
radially retractable to allow the reamers 33 to pass through the
unexpanded liner section 4 when in retracted mode.
[0031] During normal operation or the first embodiment (FIGS. 1 and
2), a lower end portion of the liner 4 is initially everted. That
is, the lower end portion is bent radially outward and in axially
reverse direction, whereby the U-shaped lower section 11 and a
short length of expanded liner section 10 are initiated.
Subsequently, the expanded liner section 10 is anchored to the
wellbore wall 14 by the anchoring means. Depending on the geometry
and/or material properties of the liner 4, the expanded liner
section 10 alternatively can become anchored to the wellbore wall
automatically by friction forces between the expanded liner section
10 and the wellbore wall 14.
[0032] A downward force is then applied to the unexpanded liner
section 8 so as to move it gradually downward. As a result, the
unexpanded liner section 8 becomes progressively everted whereby
the unexpanded liner section 8 is transformed into the expanded
liner section 10. The bending zone 12 moves in downward direction
during the eversion process at approximately half the speed of
downward movement of the unexpanded liner section 8.
[0033] If desired, the mechanical properties and dimensions of the
liner 4 can be selected such that the expanded liner section 10
becomes pressed against the wellbore wall 14 as a result of the
expansion process so as to seal against the wellbore wall and/or to
stabilize the wellbore wall.
[0034] Since the length, and hence the weight, of the unexpanded
liner section 8 gradually increases, the magnitude of the downward
force can be gradually lowered in correspondence with the
increasing weight of unexpanded liner section 8. Eventually, the
downward force may need to be replaced by an upward force to
prevent buckling of liner section 8.
[0035] The unexpanded liner section 8 is at its upper end extended
in correspondence with its downward movement, for example by adding
tubular sections to the liner, or by continuously forming the liner
from metal sheet on a reel.
[0036] Simultaneously with downward movement of the unexpanded
liner section 8 into the wellbore, the drill string 20 is operated
to deepen the wellbore bottom by ejecting the fluid jets 28 against
the wellbore bottom whereby the drill string is rotated slowly. The
drill string 20 thereby gradually moves downward into the wellbore
1. The force applied to the unexpanded liner section 4 is
controlled such that the U-shaped section 11 of the liner 4 moves
downward at the same speed as the drill string 20 and remains in
contact with the curved surface portion 32 of guide device 30
whereby the U-shaped lower section 11 exerts a small thrust force
to the drill string 20. With increasing eversion of the liner 4, an
increasing portion of the thrust force results from the weight of
the unexpanded liner section 8.
[0037] Since the jetting head 22 requires only a small thrust force
for excavating the wellbore, relative to the thrust force required
for drilling with a conventional drill bit, the compressive load in
unexpanded liner section 4 can be kept relatively low. It is
thereby achieved that the risk of inadvertent buckling of the
unexpanded liner section 4 is significantly reduced.
[0038] If it is required to cut the unexpanded liner section 4, the
guide device 30 is collapsed and the drill string 20 is raised
until the cutting nozzles 26 are positioned at the desired cutting
level (FIG. 2). Subsequently fluid jets 36 with entrained abrasive
particles are jetted through cutting nozzles 26 against the
unexpanded liner section 4 thereby cutting the liner section 4.
[0039] Normal operation of the second embodiment is substantially
similar to normal operation of the first embodiment. In addition,
the reamers 33 are kept in expanded mode during drilling with the
drill string 20 thereby enlarging the diameter of the wellbore 1 to
the nominal diameter.
[0040] In a modified version of the second embodiment (not shown),
the drill string is at its lower end provided with a conventional
pilot drill bit for drilling a pilot bore of relatively small
diameter, and the reamers are provided with jetting nozzles to
enlarge the borehole to its nominal diameter. Since the jetting
nozzles can be precisely controlled with respect to direction and
velocity of the fluid jets, the jetting nozzles in the reamers
allow accurate drilling of the borehole to its nominal
diameter.
[0041] When it is required to retrieve the drill string 20 to
surface the guide device 30 and the reamers 33 (if present) are
radially retracted and the drill string 20 is retrieved through the
unexpanded liner section 8.
[0042] With the system of the invention, it is achieved that the
wellbore is progressively lined with the everted liner directly
above the jetting head during the drilling process. As a result,
there is only a relatively short open-hole section of the wellbore
at all times. The advantages of such short open-hole section will
be most pronounced during drilling into a hydrocarbon fluid
containing layer of the earth formation. In view thereof, for many
applications it will be sufficient if the process of liner eversion
during drilling is applied only during drilling into the
hydrocarbon fluid reservoir, while other sections of the wellbore
are lined or cased in conventional manner. Alternatively, the
process of liner eversion during drilling may be commenced at
surface or at a selected downhole location, depending on
circumstances.
[0043] In view of the short open-hole section during drilling,
there is a significantly reduced risk that the wellbore fluid
pressure gradient exceeds the fracture gradient of the rock
formation, or that the wellbore fluid pressure gradient drops below
the pore pressure gradient of the rock formation. Therefore,
considerably longer intervals can be drilled at a single nominal
diameter than in a conventional drilling practice whereby casings
of stepwise decreasing diameter must be set at selected
intervals.
[0044] Also, if the wellbore is drilled through a shale layer, such
short open-hole section eliminates possible problems due to a
heaving tendency of the shale.
[0045] After the wellbore has been drilled to the desired depth and
the drill string has been removed from the wellbore, the length of
unexpanded liner section that is still present in the wellbore can
be left in the wellbore or it can be cut-off from the expanded
liner section and retrieved to surface.
[0046] In case the length of unexpanded liner section is left in
the wellbore, there are several options for completing the
wellbore. These are, for example, as follows: [0047] A) A fluid,
for example brine, is pumped into the annulus between the
unexpanded and expanded liner sections so as to pressurise the
annulus and increase the collapse resistance of the expanded liner
section. Optionally one or more holes are provided in the U-shaped
lower section to allow the pumped fluid to be circulated. [0048] B)
A heavy fluid is pumped into the annulus so as to support the
expanded liner section and increase its collapse resistance. [0049]
C) Cement is pumped into the annulus in order to create, after
hardening of the cement, a solid body between the unexpanded liner
section and the expanded liner section, whereby the cement may
expand upon hardening. [0050] D) The unexpanded liner section is
radially expanded (i.e. clad) against the expanded liner section,
for example by pumping, pushing or pulling an expander through the
unexpanded liner section.
[0051] In the above examples, expansion of the liner is started at
surface or at a downhole location. In case of an offshore wellbore
whereby an offshore platform is positioned above the wellbore, at
the water surface, it can be advantageous to start the expansion
process at the offshore platform. In such process, the bending zone
moves from the offshore platform to the seabed and from there
further into the wellbore. Thus, the resulting expanded tubular
element not only forms a liner in the wellbore, but also a riser
extending from the offshore platform to the seabed. The need for a
separate riser from is thereby obviated.
[0052] Furthermore, conduits such as electric wires or optical
fibres for communication with downhole equipment can be extended in
the annulus between the expanded and unexpanded sections. Such
conduits can be attached to the outer surface of the tubular
element before expansion thereof. Also, the expanded and unexpanded
liner sections can be used as electricity conductors to transfer
data and/or power downhole.
[0053] Since any length of unexpanded liner section that is still
present in the wellbore after completion of the eversion process,
will be subjected to less stringent loading conditions than the
expanded liner section, such length of unexpanded liner section may
have a smaller wall thickness, or may be of lower quality or steel
grade, than the expanded liner section. For example, it may be made
of a material having a relatively low yield strength or relatively
low collapse rating.
[0054] Instead of leaving a length of unexpanded liner section in
the wellbore after the expansion process, the entire liner can be
expanded with the method described above so that no unexpanded
liner section remains in the wellbore. In such case, an elongate
member, for example a pipe string, can be used to exert the
necessary downward force to the unexpanded liner section during the
last phase of the eversion process.
[0055] In order to reduce friction forces between the unexpanded
and expanded liner sections during the expansion process, suitably
a friction reducing layer, such as a Teflon layer, is applied
between the unexpanded and expanded liner sections. For example, a
friction reducing coating can be applied to the outer surface of
the liner before expansion. Such layer of friction reducing
material furthermore reduces the annular clearance between the
unexpanded and expanded sections, which results in a reduced
tendency of the unexpanded section to buckle. Instead of, or in
addition to, such friction reducing layer, centralizing pads and/or
rollers can be applied between the unexpanded and expanded sections
to reduce the friction forces and the annular clearance
there-between.
[0056] Instead of expanding the expanded liner section against the
wellbore wall (as described), the expanded liner section can be
expanded against the inner surface of another tubular element
already present in the wellbore.
* * * * *