U.S. patent application number 11/458031 was filed with the patent office on 2007-03-29 for method for drilling and cementing a well.
This patent application is currently assigned to TESCO CORPORATION. Invention is credited to ROBERT M. TESSARI, TOMMY M. WARREN.
Application Number | 20070068703 11/458031 |
Document ID | / |
Family ID | 37668403 |
Filed Date | 2007-03-29 |
United States Patent
Application |
20070068703 |
Kind Code |
A1 |
TESSARI; ROBERT M. ; et
al. |
March 29, 2007 |
METHOD FOR DRILLING AND CEMENTING A WELL
Abstract
A method for drilling and cementing a borehole to access at
least a portion of a formation of interest, comprising: drilling a
borehole using a drill string including an external packer and a
drilling assembly to access at least a portion of a formation of
interest; using a drilling fluid selected to minimize adverse
effects on the at least a portion of the formation of interest when
drilling into the at least a portion of the formation of interest;
setting the packer to create a seal in the borehole so that (i) an
upper drill string/borehole annulus above the packer is isolated
from (ii) a lower drill string/borehole annulus below the packer,
with the at least a portion of the formation of interest being open
to the lower drill string/borehole annulus; and introducing cement
above the external packer into the upper drill string/borehole
annulus.
Inventors: |
TESSARI; ROBERT M.;
(Calgary, AB) ; WARREN; TOMMY M.; (Coweta,
OK) |
Correspondence
Address: |
BENNETT JONES;C/O MS ROSEANN CALDWELL
4500 BANKERS HALL EAST
855 - 2ND STREET, SW
CALGARY
AB
T2P 4K7
CA
|
Assignee: |
TESCO CORPORATION
6204-6A Street SE
Calgary
CA
|
Family ID: |
37668403 |
Appl. No.: |
11/458031 |
Filed: |
July 17, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60595606 |
Jul 19, 2005 |
|
|
|
Current U.S.
Class: |
175/57 ;
166/285 |
Current CPC
Class: |
E21B 21/103 20130101;
E21B 33/14 20130101; E21B 7/20 20130101 |
Class at
Publication: |
175/057 ;
166/285 |
International
Class: |
E21B 7/00 20060101
E21B007/00; E21B 33/13 20060101 E21B033/13 |
Claims
1. A method for drilling and cementing a borehole to access at
least a portion of a formation of interest, comprising: drilling a
borehole using a drill string including an external packer and a
drilling assembly to access at least a portion of a formation of
interest; using a drilling fluid selected to minimize adverse
effects on the at least a portion of the formation of interest when
drilling into the at least a portion of the formation of interest;
setting the packer to create a seal in the borehole so that (i) an
upper drill string/borehole annulus above the packer is isolated
from (ii) a lower drill string/borehole annulus below the packer,
with the at least a portion of the formation of interest being open
to the lower drill string/borehole annulus; and introducing cement
above the external packer into the upper drill string/borehole
annulus.
2. The method for drilling and cementing a borehole of claim 1
wherein the drilling fluid generates a hydrostatic pressure lower
than the pressure in the formation of interest.
3. The method for drilling and cementing a borehole of claim 1
wherein the drilling fluid is substantially gaseous.
4. The method for drilling and cementing a borehole of claim 1
wherein the drilling fluid includes air.
5. The method for drilling and cementing a borehole of claim 1
wherein the drilling fluid includes foam.
6. The method for drilling and cementing a borehole of claim 1
wherein the external packer is set substantially without exposing
the at least a portion of the formation of interest to a damaging
hydrostatic head of fluid.
7. The method for drilling and cementing a borehole of claim 1
wherein the external packer is set by compression of the drill
string.
8. The method for drilling and cementing a borehole of claim 1
wherein the external packer is set by use of a liquid-based fluid
and the step of setting the external packer includes: sealing a
lower end of the drill string and introducing a liquid-based fluid
to hydraulically set the external packer.
9. The method for drilling and cementing a borehole of claim 8
wherein the step of sealing the lower end of the drill string
includes displacing a plug through the drill string to a position
at a lower end of the drill string.
10. The method for drilling and cementing a borehole of claim 1
wherein the step of introducing cement above the external packer
includes opening a port through the drill string to access the
upper drill string/borehole annulus.
11. The method for drilling and cementing a borehole of claim 1
wherein the drill string is at least in part formed of wellbore
casing and wherein the method further comprises leaving the drill
string downhole to case the wellbore.
12. The method for drilling and cementing a borehole of claim 11
wherein the drilling assembly is periodically retrieved and
reintroduced through the wellbore casing during drilling.
13. The method for drilling and cementing a borehole of claim 1
wherein the external packer is set with its upper end above the
formation of interest.
14. A method for drilling and cementing a borehole to access at
least a portion of a formation of interest, comprising: drilling a
borehole using a drill string including an external packer and a
drilling assembly to access at least a portion of a formation of
interest, the drilling process including tripping the drilling
assembly to surface and reintroducing the drilling assembly during
drilling; setting the packer to create a seal in the borehole so
that (i) an upper drill string/borehole annulus above the packer is
isolated from (ii) a lower drill string/borehole annulus below the
packer, with the at least a portion of the formation of interest
being open to the lower drill string/borehole annulus; and
introducing cement above the external packer into the upper drill
string/borehole annulus.
15. The method for drilling and cementing a borehole of claim 14
wherein the drill string is at least in part formed of wellbore
casing and wherein the method further comprises leaving the drill
string downhole to case the wellbore.
16. The method for drilling and cementing a borehole of claim 14
wherein the drilling proceeds during at least a period of time
prior to setting the packer using a drilling fluid hydrostatic
pressure lower than the pressure in the formation of interest.
17. The method for drilling and cementing a borehole of claim 14
wherein prior to setting the packer, the method further comprises:
retrieving the drilling assembly to surface; and sealing the bottom
of the drill string.
18. The method for drilling and cementing a borehole of claim 14
wherein after cementing, the method further comprises: drilling
using a drilling fluid hydrostatic pressure lower than the pressure
in the formation of interest.
Description
FIELD
[0001] The invention relates to a method for processing a well and,
in particular, a method for drilling and cementing a well.
BACKGROUND
[0002] When drilling with casing, a casing string is used as the
drill string so that once the well is drilled, the casing string
can remain downhole to line the wellbore. This avoids the need for
a separate operation to trip in a well bore liner after the well
bore is drilled.
[0003] In some drilling operations through fragile formations, such
as those that have low pressure or that are highly porous, it is
desirable to reduce harmful contact with the formation while
drilling through it.
SUMMARY
[0004] In accordance with one broad aspect, the present invention
provides a method for drilling and cementing a borehole to access
at least a portion of a formation of interest, comprising: drilling
a borehole using a drill string including an external packer and a
drilling assembly to access at least a portion of a formation of
interest; using a drilling fluid selected to minimize adverse
effects on the at least a portion of the formation of interest when
drilling into the at least a portion of the formation of interest;
setting the packer to create a seal in the borehole so that (i) an
upper drill string/borehole annulus above the packer is isolated
from (ii) a lower drill string/borehole annulus below the packer,
with the at least a portion of the formation of interest being open
to the lower drill string/borehole annulus; and introducing cement
above the external packer into the upper drill string/borehole
annulus.
[0005] In accordance with another broad aspect, the present
invention provides a method for drilling and cementing a borehole
to access at least a portion of a formation of interest,
comprising: drilling a borehole using a drill string including an
external packer and a drilling assembly to access at least a
portion of a formation of interest, the drilling process including
tripping the drilling assembly to surface and reintroducing the
drilling assembly during drilling; setting the packer to create a
seal in the borehole so that (i) an upper drill string/borehole
annulus above the packer is isolated from (ii) a lower drill
string/borehole annulus below the packer, with the at least a
portion of the formation of interest being open to the lower drill
string/borehole annulus; and introducing cement above the external
packer into the upper drill string/borehole annulus.
[0006] It is to be understood that other aspects of the present
invention will become readily apparent to those skilled in the art
from the following detailed description, wherein various
embodiments of the invention are shown and described by way of
illustration. As will be realized, the invention is capable for
other and different embodiments and its several details are capable
of modification in various other respects, all without departing
from the spirit and scope of the present invention. Accordingly the
drawings and detailed description are to be regarded as
illustrative in nature and not as restrictive.
DRAWINGS
[0007] Referring to the drawings wherein like reference numerals
indicate similar parts throughout the several views, several
aspects of the present invention are illustrated by way of example,
and not by way of limitation, in detail in the figures,
wherein:
[0008] FIGS. 1, 2 and 3 show schematically steps in a method
according to one aspect of the present invention.
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION
[0009] The detailed description set forth below in connection with
the appended drawings is intended as a description of various
embodiments of the present invention and is not intended to
represent the only embodiments contemplated by the inventor. The
detailed description includes specific details for the purpose of
providing a comprehensive understanding of the present invention.
However, it will be apparent to those skilled in the art that the
present invention may be practiced without these specific
details.
[0010] In a method according to the invention, a borehole can be
drilled to access a formation of interest. A formation of interest
herein is that which is desired to be protected from harmful fluid
contact therewith. A formation of interest may therefore include a
fragile formation, such as one that has a low pressure or one that
is highly porous. The formation of interest may be in various
states such as a newly accessed formation or a depleted
formation.
[0011] The borehole may be drilled with a drill string and a
drilling assembly including an external packer which, when desired,
may be positioned and may be set to seal the borehole relative to
the formation of interest so that the drill string/borehole annulus
above the packer is isolated from the drill string/borehole annulus
below the packer. A drilling fluid may be used that is selected to
minimize adverse effects on the formation. Thereafter, cement may
be added above the packer.
[0012] The invention relates in one embodiment to a method of
drilling, casing, and cementing a wellbore where the casing is
carried along with or used as at least a portion of the drill
string, an external casing packer is carried on the casing and may
be set to form a seal in the annulus between the casing and the
borehole after drilling of at least a portion of that borehole and
before cement is introduced. Cement may be pumped into the annulus
between the casing and the borehole above the packer after the
packer creates a seal in the casing/borehole annulus, so that a
potentially damaging hydrostatic head of liquid (packer setting
fluid and/or cement) is substantially prevented from being
communicated to a formation of interest positioned relative to,
which is generally below, the packer.
[0013] The borehole can be drilled into or through a formation of
interest, of which at least a portion thereof is desired to be
protected. The packer may be positioned and may be set to seal the
borehole relative to the formation of interest. For example, the
packer may be positioned above any portion of the formation of
interest that is sought to be protected to isolate the
casing/borehole annulus above the packer from that portion of the
formation of interest, which may be open to the casing/borehole
annulus below the packer.
[0014] A drilling fluid may be used that is selected to minimize
adverse effects to the formation such as, for example, by drilling
the borehole substantially without putting a damaging hydrostatic
pressure head on the formation of interest and/or avoiding the use
of fluids that adversely chemically react with the materials of the
formation of interest. Such a drilling fluid may be for example,
underbalanced relative to the formation of interest to thereby have
a lower hydrostatic pressure than the pressure of the formation of
interest or of a chemical state or composition selected to
substantially avoid an adverse affect on the formation of the
interest. In one embodiment, for example, a foam-type drilling
fluid may be used. In another embodiment, a gaseous-based drilling
fluid may be used, which may be substantially dry. For example, a
low density, compressible drilling fluid can be used including, for
example, air, nitrogen, natural gas, or a mixture of any of these
fluids. In one embodiment, a drilling fluid comprised substantially
entirely of air may be useful.
[0015] In another embodiment, consideration may also be given to
the method by which the packer is set so that the formation is not
damaged by this action. The packer may be set by setting the casing
down in the borehole, by hydraulic actuation or by inflation. If a
compressible fluid is used as the drilling fluid, consideration may
be given to methods for setting the packer since compressible
fluids may not be capable of use to set a packer. If it is not
desirable to set the drill string down on bottom, then care may be
necessary to avoid exposing the formation of interest to a damaging
packer setting fluid. For example, some packers require the use of
non-compressible, higher density, liquid-based fluids to
hydraulically set them. In such an embodiment, once the casing
point is reached the low density compressible fluid used for
drilling may be replaced with the non-compressible, higher density,
liquid-based fluid, such as, for example, water or mud, that may be
used to inflate the packer. In such a method, it may be necessary
to ensure that the higher density liquid does not damage the
formation of interest. Such damage might be caused, for example, by
exposing the formation of interest to the hydrostatic head of the
higher density, packer-setting fluid.
[0016] For drilling, the casing may be used as at least a portion
of the drill string or carried along with the drill string. In so
doing, a drilling assembly may be used that proceeds ahead of the
bottom end of the casing and creates a borehole with an ID greater
than the casing so that the casing can be advanced behind the
drilling assembly. One such drilling assembly includes, for
example, a pilot bit and an underreamer. The drilling assembly and
other components may be sized appropriately to be retrieved and
reintroduced through the casing periodically during drilling and/or
retrieved after drilling is completed. Alternately, the drilling
assembly may be intended to be left downhole.
[0017] The drilling assembly or casing may include or be capable of
accepting seals or valves which are selectively openable/closable
to permit closing of the lower end of the casing, when desired, to
control the passage of fluids out through the drilling assembly and
out of the bottom end of the casing. Such seals or valves may be
provided by a launchable plug, selectively closeable seals in the
drilling assembly, etc. In addition, the casing may include ports
or valves or require the formation of ports for providing an
opening through the casing above the packer to permit introduced
cement to pass into the annulus above the packer. For example, a
selectable port sub, a cementing stage tool, or perforating methods
may be employed for selectively opening a port above the packer. In
one embodiment, a port may be provided that is opened by rotating
an upper portion of the casing relative to a lower end of the
casing that is held stationary by engagement of the borehole wall
through the inflated packer.
[0018] In the method, it may be desirable to hold the introduced
cement in the casing/borehole annulus and possibly also in the
lower casing ID until the cement sets. In one method, for example,
it may be desirable to create a seal adjacent the casing bottom end
to prevent cement from U-tubing from the annulus back into the
casing ID. In one embodiment, a seal is created adjacent the bottom
of the casing to contain cement in the lower region of the casing
and/or in the annulus. In one embodiment, a check valve may be
provided in the casing wall up hole of the external casing packer,
which permits flow from the casing ID to the casing/borehole.
annulus, but acts against reverse flow. In another embodiment, a
cement introduction tool including a seal formable between the tool
and the casing ID to prevent flow of the introduced cement upwardly
past the cement introduction tool may be employed in the casing.
Cement may be introduced through the tool below the seal into the
casing ID and into the casing/borehole annulus. In yet another
embodiment, a wiper plug may be held in place above the cement to
prevent U-tubing.
[0019] Thereafter, the casing may be cleaned out and the borehole
below the packer may be treated, further drilled, produced in any
of various ways.
[0020] FIG. 1 illustrates generally a first step in one possible
method according to the invention wherein a borehole 10 may be
drilled, cased and cemented after drilling while protecting at
least a portion of a formation of interest 12 against damage by
contact with a hydrostatic head of fluid, such as may be generated
by some drilling fluids, packer setting fluids and/or cement.
[0021] In the illustrated embodiment, a casing string 16 is used as
the drill string and a drilling assembly 18 is mounted at the
distal end of the casing string to form the borehole ahead of the
casing string. Periodically during drilling, the drilling assembly
may be tripped to surface for inspection, repair or replacement and
may be returned downhole to continue drilling. Such a process is
facilitated by use of casing as the drill string to surface. By use
of casing as a drill string, the drilling, casing and cementing of
the borehole may be completed without a requirement to ever trip
the casing out of the well. In particular, the casing may be used
as the drill string and then left down hole to case the
borehole.
[0022] The lower end of the casing may include an external casing
packer 20 that may be energized by any of various means including
for example by inflation with water, mud or cement (as shown in the
Figures), by direct compression of the drill string, or by indirect
compression as by use of a hydraulically powered piston, to create
a seal about the casing at the position of the packer, which in
this embodiment is adjacent the casing's lower end. The casing may
also include at least one port 22 (shown closed in FIG. 1) that can
be opened, when desired, to allow fluid such as, for example,
cement to be pumped from the interior of the casing to the exterior
annulus 23, which is that open area between the casing and borehole
10. Port 22 may be positioned in the casing uphole of the external
casing packer.
[0023] In the present method, a borehole is drilled through a
formation 11 including formation of interest 12 using casing as the
drill string and including external packer 20. Drilling into at
least a portion of the formation of interest is accomplished using
a drilling fluid (arrows A) that is substantially inert to the
formation of interest, with consideration as to the properties of
the formation of interest. For example, in one embodiment, drilling
proceeds using a fluid, such as air or foam, that has a lower
hydrostatic pressure than the pressure of the formation of
interest. Of course, other drilling fluids can be used until it is
desired to protect the formation of interest or a portion thereof
against damage or further damage by that drilling fluid. For
example, if desired the operator may wish to drill without
consideration as to the effects of the drilling fluid on the
formation until it is determined that the formation of interest or
a depth of interest has been reached. Thereafter, the operator may
wish to cement the well or otherwise displace the previous drilling
fluid to permit initiation of a method according to the present
invention using a drilling fluid selected to minimize adverse
effects on the formation of interest for a period of time during
drilling.
[0024] Once drilling has been achieved to a desired depth, in the
illustrated embodiment, drilling assembly 18 may tripped out of the
casing and external casing packer 20 may be set to isolate an upper
portion of the casing/borehole annulus from a lower portion of the
casing/borehole annulus, the lower portion of the casing/borehole
annulus being that portion open to the portion of the formation to
be protected. If it is desired to hydraulically set packer 20, care
may be taken to avoid exposing the selected portion of the
formation of interest to the hydrostatic head of the hydraulic
setting fluid. For example, FIG. 2 shows one such method wherein
packer 20 is hydraulically settable. To set the packer, the
drilling fluid is displaced with a hydraulic setting fluid without
exposing the formation of interest to the hydrostatic pressure of
the hydraulic setting fluid. In this method, a plug 28 is installed
to seal the lower end of the casing string before the hydraulic
setting fluid is introduced. For example, in one method, drilling
fluid may be bled off, a plug 28 may be introduced to the casing
string and a circulating head 30 may be installed at surface.
Hydraulic packer setting fluid 32, such as water may be introduced
above the plug to displace the plug downwardly (arrow B). Care may
be taken to avoid causing the plug to land in an uncontrolled or
damaging fashion at the bottom of the casing string and/or care may
be taken to avoid creation of problematic trapped pockets of
drilling fluid. For example, drilling fluid backpressure may be
controlled to control the displacement of the plug and/or the state
of the hydraulic packer setting fluid may be controlled to control
the pressure and/or density of the fluid 32 above the plug. This,
for example, may involve pumping the plug to separate the hydraulic
packer setting fluid from the drilling fluid and to prevent the
higher density hydraulic packer setting fluid from passing through
the bit. While pumping the higher density fluid, some procedure may
be useful to control the rate at which the heavier density fluid
falls in the casing. The controlling step may include, for example,
any of holding backpressure on the annulus, using a
flow-restricting nozzle at the bit, and/or pumping water above a
plug with a positive displacement pump that is rigged up so that no
air can be sucked into the casing. As the hydrostatic pressure of
the fluid in the casing exceeds the hydrostatic pressure in the
annulus with consideration to back pressure and annular friction,
the more dense fluid may tend to fall faster. By controlling the
rate that water is pumped into the casing and preventing air from
being sucked in, the hydrostatic head can be controlled by letting
the water flash to low temperature steam. Of course, if such a
method is used for introducing hydraulic packer setting fluid 32,
the casing may need to be designed with sufficient collapse
pressure to withstand this process.
[0025] Once the plug lands, introduction of hydraulic packer
setting fluid 32 may be continued to gradually bring the
hydrostatic pressure up to the full hydrostatic head of the liquid
setting fluid. The setting fluid then may be manipulated, as by
pressuring up, to set the packer. Packer 20 in the illustrated
embodiment is hydraulically settable and may include a check valve
for permitting hydraulic inflation thereof. As such, once the
packer is set, the check valve may maintain the packer in the
inflated state.
[0026] Once packer 20 is set, as shown in FIG. 3, port 22 may be
opened so that cement can then be introduced to the annulus between
the casing and the borehole above the casing packer. Port 22 may be
opened by various means, as noted previously. In one embodiment,
port 22 may be part of a mechanism providing opening of the port by
rotation of an upper casing portion relative to a lower casing
portion. Since in this embodiment the bottom casing portion is
anchored by the packer, the port may be opened by rotating the
upper casing portion while the lower portion of the casing remains
stationary. Thereafter, hydraulic packer-setting fluid 32 and
cement may be displaced through the casing string and annulus
(arrows C). The cement may be introduced to cement the casing in
the well bore.
[0027] Thereafter, the formation of interest below the packer may
be accessed in any of various ways and for various purposes. If it
is desired to further drill into the formation of interest, it may
be of interest to undertake such further drilling using a drilling
fluid selected to minimize adverse effects on the formation of
interest.
[0028] Thus, as shown, by use of the present invention at least a
selected portion of a formation of interest 12 may be protected
against damage by contact with a hydrostatic head of drilling fluid
and by contact with cement by using a drilling fluid selected to
minimize adverse effects on the formation of interest, when
drilling into it, and by selecting the external casing packer to be
set above the formation of interest. If the packer is settable by
use of hydraulic fluid, in one aspect of the present invention, the
selected portion of the formation of interest 12 may also be
protected against damage by contact with that packer setting
fluid.
[0029] Obviously, any portion of the formation of interest that is
above the upper end 20a of the packer once it is set will be
exposed to the effects of the packer setting fluid and cement after
it moves through port 22 into the annulus above the packer. If it
is desired to completely avoid damage to the formation of interest
by contact with a hydrostatic head of drilling fluid or cement, it
may be useful set the packer so that its upper end (as shown) is
completely above the formation of interest.
[0030] The previous description of the disclosed embodiments is
provided to enable any person skilled in the art to make or use the
present invention. Various modifications to those embodiments will
be readily apparent to those skilled in the art, and the generic
principles defined herein may be applied to other embodiments
without departing from the spirit or scope of the invention. Thus,
the present invention is not intended to be limited to the
embodiments shown herein, but is to be accorded the full scope
consistent with the claims, wherein reference to an element in the
singular, such as by use of the article "a" or "an" is not intended
to mean "one and only one" unless specifically so stated, but
rather "one or more". All structural and functional equivalents to
the elements of the various embodiments described throughout the
disclosure that are know or later come to be known to those of
ordinary skill in the art are intended to be encompassed by the
elements of the claims. Moreover, nothing disclosed herein is
intended to be dedicated to the public regardless of whether such
disclosure is explicitly recited in the claims. No claim element is
to be construed under the provisions of 35 USC 112, sixth
paragraph, unless the element is expressly recited using the phrase
"means for" or "step for".
* * * * *