U.S. patent application number 12/373628 was filed with the patent office on 2010-01-14 for pipe string device for conveying a fluid from a well head to a vessel.
This patent application is currently assigned to AGR Subsea AS. Invention is credited to Roger Stave.
Application Number | 20100006297 12/373628 |
Document ID | / |
Family ID | 38923461 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100006297 |
Kind Code |
A1 |
Stave; Roger |
January 14, 2010 |
PIPE STRING DEVICE FOR CONVEYING A FLUID FROM A WELL HEAD TO A
VESSEL
Abstract
A device including a pipe string device anchored to a sea floor.
The device is configured to convey a fluid from a well head to a
vessel during a drilling phase of a well. The fluid is located in
the pipe string and needing, for well-technical reasons, to be
given a flow boost. The pipe string that is anchored on the sea
floor is provided with at least one injection point for a driving
fluid.
Inventors: |
Stave; Roger; (Bergen,
NO) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
AGR Subsea AS
|
Family ID: |
38923461 |
Appl. No.: |
12/373628 |
Filed: |
July 31, 2007 |
PCT Filed: |
July 31, 2007 |
PCT NO: |
PCT/NO2007/000269 |
371 Date: |
January 13, 2009 |
Current U.S.
Class: |
166/335 ;
175/5 |
Current CPC
Class: |
F17D 1/12 20130101; E21B
21/12 20130101; E21B 21/001 20130101 |
Class at
Publication: |
166/335 ;
175/5 |
International
Class: |
E21B 7/12 20060101
E21B007/12; E21B 41/00 20060101 E21B041/00; E21B 43/01 20060101
E21B043/01 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 14, 2006 |
NO |
20063269 |
Claims
1. A device comprising a pipe string anchored to a sea floor and
adapted to convey a fluid from a well head to a vessel during a
drilling phase of a well, the fluid being located in the pipe
string and needing, for well-technical reasons, to be given a flow
boost, wherein the pipe string that is anchored on the sea floor is
provided with at least one injection point for a driving fluid.
2. The device in accordance with claim 1, wherein the at least one
injection point comprises a fluid-operated ejector.
3. The device in accordance with claim 1, wherein a mechanically
working pump is connected to the pipe string.
4. The device in accordance with claim 1, wherein the pipe string
leads into a separator tank on the vessel.
5. The device in accordance with claim 1, wherein the pipe string
is anchored on the sea floor by an anchor and provided with a
buoyancy body near a sea surface.
6. The device in accordance with claim 1, wherein the pipe string
is suspended from the vessel and connected to the well head by a
flexible connection.
7. A method comprising providing flow assistance to a fluid located
in a pipe string during a drilling phase of a well, the fluid being
conveyed by the pipe string from a well head to a vessel, wherein
the method further comprises supplying the pipe string with a
driving fluid that has a lower density than the conveyed fluid at
at least one injection point located on the pipe string.
8. The method in accordance with claim 7, further comprising
supplying, at the at least one injection point, a driving fluid
which has a lower specific gravity than the fluid being conveyed by
the pipe string.
9. A device comprising a pipe string assembly, wherein at least a
substantial portion of the pipe string assembly is interposed in a
sea between a sea floor and a surface of the sea, wherein the pipe
string assembly includes at least one fluid ejector adapted to
inject a driving fluid into the pipe string assembly to give a
fluid contained in the pipe string assembly a flow boost to assist
the fluid in the pipe string assembly to flow away from the sea
floor towards the surface of the sea.
10. The device of claim 9, wherein the pipe string assembly
includes a plurality of fluid ejectors spaced along the pipe string
assembly.
11. The device of claim 9, wherein the pipe string assembly
includes at least five fluid ejectors spaced along the pipe string
assembly.
12. The device of claim 9, wherein the pipe string assembly
includes at least five fluid ejectors spaced along the pipe string
assembly substantially spaced along the pipe string assembly in
even intervals.
13. The device of claim 9, wherein the pipe string assembly
includes a plurality of fluid ejectors spaced along the pipe string
assembly, wherein a lower fluid ejector, relative to a higher fluid
ejector in a direction opposite the direction of gravity, is
adapted to inject driving fluid into the pipe string assembly to
supply a pressure to the fluid in the pipe string assembly to drive
the fluid in the pipe string assembly to the higher fluid
ejector.
14. The device of claim 9, wherein the pipe string assembly extends
from a location proximate a well head on the sea floor to a
location proximate a buoyant vessel located on the surface of the
sea, wherein a separator is located on the buoyant vessel, and
wherein the separator is adapted to separate driving fluid from a
drilling fluid in the pipe string assembly.
15. The device of claim 9, wherein the device is adapted to control
a return pressure at a well head located proximate the sea floor to
which the pipe string assembly is connected.
16. The device of claim 9, wherein the device is adapted to control
a return pressure at a well head located proximate the sea floor to
which the pipe string assembly is connected by adjusting a
driving-fluid pressure of one or more of the at least one fluid
ejector.
17. The device of claim 9, wherein the device further comprises a
mechanical pump in fluid communication with the pipe string
assembly at a location proximate the sea floor, wherein the
mechanical pump is adapted to increase a flow rate of fluid in the
pipe string assembly.
18. A method, comprising: obtaining the device according to claim
9, directing a drilling fluid in the direction of gravity from a
location proximate the surface of the sea to a well head proximate
the sea floor; directing the drilling fluid directed to the well
head to the pipe string assembly; directing a driving fluid to one
or more of the at least one fluid injector; and driving the
drilling fluid directed to the pipe string assembly in a direction
away from the direction of gravity by injecting the driving fluid
through one or more of the at least one fluid injector.
19. The method of claim 18, wherein the pipe string assembly
extends from the well head to a buoyant vessel located proximate
the surface of the sea.
20. The method of claim 18, wherein the pipe string assembly
includes a plurality of fluid ejectors spaced along the pipe string
assembly, wherein a lower fluid ejector is located lower than a
higher fluid ejector located higher than the lower fluid ejector in
a direction opposite the direction of gravity, the method further
comprising injecting the driving fluid into the pipe string
assembly using the lower fluid ejector to supply a pressure to the
fluid in the pipe string assembly to drive the drilling fluid in
the pipe string assembly to the higher fluid ejector.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a national stage entry application of
PCT/NO2007/000269, filed on Jul. 13, 2007, which claims priority to
Norwegian Patent Application No. 20063269, filed in Norway on Jul.
14, 2006, the contents of these applications being incorporated
herein by reference in their entirety.
BACKGROUND
[0002] The present inventor has recognized that, during the
drilling for and the recovery of petroleum, it is often necessary
to use a well fluid which is adapted for the conditions in the well
with respect to, by way of example only and not by way of
limitation, density and viscosity, among other things. It is
common, for example, to use drilling fluid having a density of
approximately 1.6 kg/l.
[0003] The present inventor has recognised that during the first
phase of the drilling process, "disposable drilling fluid" is
sometimes utilized, and the effluent cuttings are sometimes
deposited on the sea floor, which the inventor has recognized may
have a deleterious effect on the environment and also may result in
increased costs.
[0004] U.S. Pat. No. 6,745,851 discloses a pump-operated solution
which can recover and recirculate drilling fluid.
[0005] The present inventor has recognised that during drilling at
great depths offshore, the head from the drilling vessel down to
the well formation may become so great that drilling fluid
penetrates into the formation. Such a flow of drilling fluid into
the formation is sometimes undesirable because, for example,
relatively expensive drilling fluid is lost, and because an inflow
of this kind may reduce the future productivity of a well.
[0006] A method which is sometimes utilized in offshore wells
involves pumping drilling fluid, as it is returning from the
borehole, out at the well head on the sea floor, then flowing it
back to the vessel via a separate pipe.
[0007] In this way, the static pressure in the borehole can be
controlled, for example, by controlling the liquid head in the
riser, if such is installed, between the well head and vessel.
[0008] NO Patent 319213 (WO2005052307) discloses a method directed
towards controlling the liquid pressure in the well by filling the
upper portion of the riser with a fluid having a different density
relative to the density of the drilling fluid.
[0009] The present inventor has recognised that at relatively great
sea depths, at which the return pipe necessarily is long, the
necessary pump pressure at the sea floor is relatively high because
of the density and viscosity of the drilling fluid. It is difficult
to achieve the necessary flow rate without having to use pipes of a
relatively large diameter, which entails increased pipe weight and
thereby considerably higher investment costs.
SUMMARY
[0010] The present invention relates to a pipe string. More
particularly, it relates to a pipe string for conveying a fluid
from a well head to a vessel, in which, for technical reasons, the
fluid located in the pipe string is to be given a flow boost, and
in which the pipe string is provided along its length with at least
one injection point for a driving fluid. The injection point may be
formed by a fluid-operated ejector. The invention also includes a
method of using the device.
[0011] In an exemplary embodiment, there is a pipe string for
conveying a fluid from a well head to a vessel, in which the fluid
located in the pipe string is to be given a flow boost, wherein the
pipe string is provided along its length with at least one
injection point for a driving fluid.
[0012] In some embodiments, the injection point may comprise a
fluid-operated ejector.
[0013] One or more such injection points can be disposed at
suitable intervals along the pipe string from the sea floor and up
to the vessel. The pipe string forms a separate flow path relative
to a possible riser, in some embodiments.
[0014] In an exemplary embodiment, where the injection point
comprises an ejector, a possible ejector located above will relieve
the ejector located below, so that this ejector starts a flow
feeding the ejector located above with fluid.
[0015] Alternatively, in another exemplary embodiment, a pump may
be arranged which pumps the fluid through the pipe string, wherein
one or more ejectors at the upper portion of the pipe string form
auxiliary apparatuses for a sufficient flow rate through the pipe
string to be achieved.
[0016] In some embodiments, the driving fluid has a lower density
than the fluid located in the pipe string. Thus, on injection of a
second fluid, the overall liquid pressure within the fluid string
at the sea floor will be reduced.
[0017] If the second fluid comprises a gas, the gas may expand as
it rises in the pipe string, thereby further reducing the overall
liquid pressure within the pipe string at the sea floor.
[0018] In some embodiments, the pipe string may be anchored on the
sea floor and be provided with buoyancy bodies at its upper
portion, and/or may be suspended from the vessel which then carries
the weight of the pipe string.
[0019] The device and method according to the invention may provide
a satisfactory flow rate in the pipe string, even with the use of a
pipe string of a relatively small diameter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 schematically presents a vessel which is provided
with a pipe string in accordance with an exemplary embodiment of
the invention.
[0021] FIG. 2 schematically presents the invention in an
alternative embodiment.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
[0022] The following describes some exemplary embodiments,
including apparatuses and methods, of the present invention.
[0023] Referring to FIG. 1, a pipe string 1 which is connected at
its lower end portion to a well head 2 on the sea floor 4, and
which is connected at its upper end portion to a separator 6. The
separator 6 is located on a vessel 8.
[0024] The vessel 8 is typically working a well 10, which is in the
ground, and is connected to the well 10 by a pipe connection 12
extending through the well head 2. Dependent on the operations
involved, the pipe connection 12 may comprise, in a manner known
per se, one or more of drill pipe, marine riser, work riser or
other well-intervention tools.
[0025] The pipe string 1 is anchored on the sea floor 4 by an
anchor 14. At its upper portion, near the sea surface 16, is
arranged a buoyancy body 18 which is arranged to take the weight of
the pipe string 1.
[0026] The pipe string 1 is provided with fluid-operated ejectors
20 suitably spaced apart, which are supplied with driving fluid
from the vessel 8 via at least one driving-fluid pipe 22.
[0027] When a fluid is to flow through the pipe string 1 from the
well head 2, the pressurized fluid supply via the driving-fluid
pipe 22 from the vessel 8 to the ejectors 20 is opened. The flow is
started by each ejector 20 supplying the necessary pressure to the
fluid until the fluid flows to the next ejector along the pipe
string 1.
[0028] At the vessel 8, the fluid enters the separator 6, in which
driving gases that may be present are separated from the rest of
the fluid before the remaining fluid flows on for treatment in, for
example, screening machines, not shown.
[0029] The return pressure at the well head 2 can be controlled by
adjusting the driving-fluid pressure into the ejectors 20.
[0030] In an alternative embodiment, as may be seen in FIG. 2, a
mechanical pump 24 is arranged at the lower portion of the pipe
string 1. The ejectors 20, which are arranged at the upper portion
of the pipe 1, are used to increase the flow rate through the pipe
string 1 beyond that effected by the pump 24 on its own.
[0031] Given the disclosure of the present invention, one versed in
the art would appreciate that there are other embodiments and
modifications within the scope and spirit of the present invention.
Accordingly, all modifications attainable by one versed in the art
from the present disclosure within the scope and spirit of the
present invention are to be included as further embodiments of the
present invention.
* * * * *