U.S. patent application number 11/404143 was filed with the patent office on 2006-08-31 for well drilling and production using a surface blowout preventer.
Invention is credited to Gavin Humphreys.
Application Number | 20060191716 11/404143 |
Document ID | / |
Family ID | 34550303 |
Filed Date | 2006-08-31 |
United States Patent
Application |
20060191716 |
Kind Code |
A1 |
Humphreys; Gavin |
August 31, 2006 |
Well drilling and production using a surface blowout preventer
Abstract
Production and drilling may be achieved by a system which uses a
rotating head coupled to surface blowout preventer stack for fluid
flow control. A casing connects these surface components to a
subsea shutoff assembly with a pair of ram shear devices to cut off
the string to the wellhead. Both the casing and an alternate line
may be latched so that they may be released if necessary. The
rotating head may include a rubber packer to prevent upward flow of
drilling fluid and production hydrocarbons and, at the same time,
provide rotation to the drill string. Managed pressure drilling or
under balanced drilling may be used in some embodiments.
Inventors: |
Humphreys; Gavin; (Aberdeen,
GB) |
Correspondence
Address: |
TROP PRUNER & HU, PC
1616 S. VOSS ROAD, SUITE 750
HOUSTON
TX
77057-2631
US
|
Family ID: |
34550303 |
Appl. No.: |
11/404143 |
Filed: |
April 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10697204 |
Oct 30, 2003 |
7032691 |
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11404143 |
Apr 13, 2006 |
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Current U.S.
Class: |
175/5 ; 166/358;
166/364 |
Current CPC
Class: |
E21B 33/085 20130101;
E21B 21/001 20130101; E21B 21/08 20130101; E21B 19/002 20130101;
E21B 21/085 20200501 |
Class at
Publication: |
175/005 ;
166/358; 166/364 |
International
Class: |
E21B 7/12 20060101
E21B007/12 |
Claims
1. A method comprising: producing hydrocarbons from a subsea well
using a rotating head mounted on a surface blowout preventer and
injecting a density lowering fluid through the drill string and the
surface blowout preventer.
2. The method of claim 1 including using the surface blowout
preventer to provide surface flow control.
3. The method of claim 2 including providing a subsea shutoff
assembly in addition to said surface blowout preventer.
4. The method of claim 3 including providing shear and emergency
disconnect capability in the event the well control is lost.
5. The method of claim 1 including coupling said surface blowout
preventer to a wellhead using a connector and providing a remotely
operable subsurface latch to sever the connection between said
wellhead and said surface blowout preventers.
6. The method of claim 5 including tensioning said casing.
7. The method of claim 5 including providing a flow of mud through
a casing to a drill bit.
8. The method of claim 7 including lowering the density of mud by
beginning the injection of said density lowering fluid when
production begins.
9. The method of claim 1 including providing a rotating head that
transfers rotational energy to said drill string through a
packer.
10. The method of claim 9 including providing said rotational
energy through a resilient packer.
11. The method of claim 1 including drilling under-balanced.
12. The method of claim 1 including using managed pressure
drilling.
13. A drilling rig comprising: a rotating head; a drill string
coupled to said rotating head; a surface blowout preventer mounted
under said rotating head on said rig; and an apparatus to pump
lower density drilling mud to the bottom of a hole through said
drill string and drill bit.
14. The rig of claim 13 including a connector coupled from said
surface blowout preventer to a subsea shutoff assembly.
15. The rig of claim 14 wherein said subsea shutoff assembly
includes a pair of shear blowout preventers.
16. The rig of claim 15 including a remotely operable latch to
disconnect a connector from said subsea shutoff assembly in the
event of an emergency.
17. The rig of claim 16 wherein said connector is tensioned.
18. The rig of claim 17 wherein said subsea shutoff assembly
includes a pair of shear ram subsurface blowout preventers and said
connector on top of said pair of shear ram subsurface blowout
preventers.
19. The rig of claim 13 including a riser coupled to said surface
blowout preventer.
20. The rig of claim 19 including a choke coupled to said surface
blowout preventer to control the pressure in said riser.
21. The rig of claim 13 wherein said rotating head includes a
resilient packer and a drill string and tubing, said resilient
packer to seal the region between said drill string and said tubing
and to transfer rotational energy from said tubing to said drill
string.
22. A method comprising: operating a subsea wellhead in an
underbalanced or balanced condition; providing mud at a first
density to said wellhead; and injecting, from the sea surface, a
first density lowering fluid, into mud returning from said
wellhead, through a drill string.
23. The method of claim 22 including producing hydrocarbons from a
subsea well in an underbalanced condition using a rotating head
mounted on a surface blowout preventer.
24. The method of claim 23 including using the surface blowout
preventer to provide surface flow control.
25. The method of claim 24 including providing a subsurface blowout
preventer in addition to said surface blowout preventer.
26. The method of claim 25 including providing subsurface shear
blowout preventers.
27. The method of claim 23 including providing a rotating head that
transfers rotational energy to said drill string through a
packer.
28. The method of claim 27 including providing said rotational
energy through a resilient packer.
29. The method of claim 28 including operating a valve to begin the
injection of the first density lowering fluid when production is
ready to begin.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 10/697,204, filed on Oct. 30, 2003.
BACKGROUND
[0002] This invention relates generally to drilling of wells and
production from wells.
[0003] Generally, wells are drilled in a slightly over-balanced
condition where the weight of the drilling fluid used is only
slightly over the pore pressure of the rocks being drilled.
[0004] Drilling mud is pumped down the drill string to a drill bit
and used to lubricate and cool the drill bit and remove drilled
cuttings from the hole while it is being drilled. The viscous
drilling mud carries the drilled cuttings upwardly on the outside
and around the drill string.
[0005] In a balanced situation, the density of the mud going
downwardly to the drill bit and the mud passing upwardly from the
drill bit is substantially the same. This has the benefit of
reducing the likelihood of a so-called kick. In a kick situation,
the downward pressure of the drilling mud column is not sufficient
to balance the pore pressure in the rocks being drilled, for
example of gas or other fluid, which is encountered in a formation.
As a result, the well may blowout (if an effective blowout
preventer (BOP) is not fitted to the well) which is an extremely
dangerous condition.
[0006] In underbalanced drilling, the aim is to deliberately create
the situation described above. Namely, the density or equivalent
circulating density of the upwardly returning mud is below the pore
pressure of the rock being drilled, causing gas, oil, or water in
the rock to enter the well-bore from the rock being drilled. This
may also result in increased drilling rates but also the well to
flow if the rock permeability and porosity allowed sufficient
fluids to enter the well-bore.
[0007] In this drilling environment it is general practice to
provide a variety of blowout preventers to control any loss of
control incidents or blowouts that may occur.
[0008] A variety of techniques have been utilized for underbalanced
or dual gradient drilling. Generally, they involve providing a
density lowering component to the returning drilling mud. Gases,
seawater, and glass beads have been injected into the returning mud
flow to reduce its density.
[0009] In deep subsea applications, a number of problems may arise.
Because of the pressures involved, everything becomes significantly
more complicated. The pressure that bears down on the formation
includes the weight of the drilling mud, whereas the pressure in
the shallow formations is dictated by the weight of seawater above
the formation. Because of the higher pressures involved, the
drilling mud may actually be injected into the formation, fracture
it and may even clog or otherwise foul the formation itself,
severely impairing potential hydrocarbon production.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic depiction of one embodiment of the
present invention;
[0011] FIG. 2 is an enlarged schematic depiction of the subsea
shut-off assembly shown in FIG. 1 in accordance with one embodiment
of the present invention;
[0012] FIG. 3 is an enlarged, schematic, cross-sectional view of
the spool 34 shown in FIG. 2 in accordance with one embodiment of
the present invention;
[0013] FIG. 4 is a schematic cross-sectional view of the rotating
head shown in FIG. 1 in accordance with one embodiment of the
present invention;
[0014] FIG. 5 is a schematic depiction of another embodiment of the
present invention;
[0015] FIG. 6 is an enlarged, schematic depiction of a subsea
shut-off valve shown in FIG. 5 in accordance with another
embodiment of the present invention;
[0016] FIG. 7 is an enlarged, schematic, cross-sectional view of
the spool 34 shown in FIG. 6 in accordance with one embodiment of
the present invention; and
[0017] FIG. 8 is a schematic cross-sectional view of the rotating
head shown in FIG. 5 in accordance with another embodiment of the
present invention.
DETAILED DESCRIPTION
[0018] In some embodiments of the present invention, both drilling
and production of fluids from a formation may occur in an
underbalanced condition. As used herein, "underbalanced" means that
the weight of the drilling mud is less than the pore pressure of
the formation. As used herein, "dual gradient" refers to the fact
that the density of fluid, at some point along its course, moving
away from a drill bit, is lower than the density of the fluid
moving towards the drill bit. Dual gradient techniques may be used
to implement underbalanced drilling. The creation of a
dual-gradient or underbalanced condition may be implemented using
any known techniques, including the injection of gases, seawater,
and glass beads, to mention a few examples.
[0019] Referring to FIGS. 1 and 4, a drilling and production
apparatus 11 may include a rotating head 10 which has a sealed
bearing 65 and elastomer pack-off 62 that seals off around the
drill string 40 while drilling operations take place. The return
fluids are then diverted to a flow line below the pack-off 62 to a
choke assembly 68 that controls the flow of the return fluid and
hence the bottom hole pressure created by the mud column. The
rotating head 10 rotates the string 40 through a surface blowout
preventer (BOP) stack 12. The surface blowout preventer stack 12
may include annular blowout preventers that control the flow of
fluid moving upwardly from the wellhead to the overlying apparatus
11.
[0020] The apparatus 11 may be tensioned using ring tensioners 16,
coupled by a pulleys 54 to hydraulic cylinders 56 to create a
tensioning system 50. The pulleys 54 may be connected to the
apparatus 11, be it a rig or ship, so that the tensioners can
maintain tension on the riser even when the apparatus is heaving up
and down. The tensioning system 50 allows the upper portion of the
apparatus 11 to move relative to the lower portion, for example in
response to sea conditions. The system 50 allows this relative
movement and adjustment of relative positioning while maintaining
tension on the casing 22, which extends from a riser tension ring
14 downwardly to a subsea shutoff assembly 24. The tension ring 14
takes the weight of the surface blowout preventer 12 and holds the
tension on the casing riser 22.
[0021] The surface portion of the apparatus 11 is coupled by a
connector 20 to the casing riser 22. The casing riser 22 is
connected to the lower section of the apparatus 11 via a
disconnectable latch 72 located below the sea level WL. The latch
72 may be hydraulically operated from the surface to disconnect the
upper portion of the apparatus 11 from the lower portion including
the subsea shutoff assembly 24.
[0022] Also provided on the ring 14 is a source of fluid that is of
a lower density than the density of mud pumped downwardly through
the casing riser 22 from the surface in one embodiment of the
present invention. The lower density fluid may be provided through
the tubing 60.
[0023] A hanger system includes a tensioner 58 that rests on a
support 56. The hanger system tensions the tensioned tubing 26 that
extends all the way down to a disconnectable subsea latch 74 above
the subsea shutoff assembly 24. Like the latch 72, the latch 74 may
be remotely or surface operated to sever and seal the tubing 26
from the subsea shutoff assembly 24 prior to disconnecting the
riser at latches 72 and 74. In one embodiment, the support 56 may
include hydraulic ram devices that move like shear ram blowout
preventers to grip the tubing 26.
[0024] The rate of lower density fluid flow through the tubing 26
from the surface may be controlled from the surface by remotely
controllable valving in the subsea shutoff assembly 24, in one
embodiment. It is advantageous to provide this lower density fluid
from the surface as opposed to attempting to provide it from a
subsea location, such as within the subsea shutoff assembly 24,
because it is much easier to control and operate large pumps from
the apparatus 11.
[0025] The subsea shutoff assembly 24 operates with the surface
blowout preventer stack 12 to prevent blowouts. While the surface
blowout preventer stack 12 controls fluid flow, the subsea shutoff
assembly 24 is responsible for cutting off or severing the wellhead
from the portions of the apparatus 11 thereabove, using shear rams
30a and 30b as shown in FIG. 2. Thus, the casing 22 may be coupled
by connector 28a to the shear ram 30a. The shear ram 30a is coupled
by a spool 34 with flanges 32a and 32b to the shear ram 30b. The
shear ram 30b may be coupled through the flange 38 to a wellhead
connector 28b, in turn connected to the wellhead.
[0026] As shown in FIG. 2, the tubing 26 connects to a remotely
controlled valve 36 that controls the rate of lower density fluid
flow through the tubing 26 to the interior of the spool 34. The
inlet from the tubing 26 to the spool 34 is between the two shear
rams 30a and 30b.
[0027] The injection of lower density fluid, as shown in FIG. 3,
makes use of the remotely controlled valve 36 on a spool 34. The
spool 34 may have drilling mud, indicated as MIN, moving downwardly
through the casing 22. The returning mud, indicated as M.sub.OUT,
extends upwardly in the annulus 46 surrounding the string 40 and
annulus 44. Thus, lower density fluid may be injected, when the
valve 36 is opened, into the returning mud/hydrocarbon flow to
lower its density.
[0028] An underbalanced situation may be created as a result of the
dual densities of mud in one embodiment. Namely, mud above the
valve 36 may be at a lower density than the density of the mud
below the valve 36, as well as the density of the mud moving
downwardly to the formation. The valve 36 may include a rotating
element 37 that allows the valve 36 to be opened or controlled. As
an additional example, the valve 36 may be a pivoted gate valve
with a hydraulic fail safe that automatically closes the valve in
the event of a loss of hydraulics. The valve 36 may enable the
extent of underbalanced drilling to be surface or remotely
controlled depending on sensed conditions, including the upward
pressure supplied by the formation. For example, the valve 36 may
be controlled acoustically from the surface.
[0029] Thus, in some embodiments of the present invention, flow
control may be done most effectively at the surface, whereas
shutoff control is done on the seafloor bed. The pumping of the
lower density fluid is also done on the surface, but its injection
may be done at the subsea shutoff assembly 24, in one embodiment
between the shear rams 30a and 30b.
[0030] The rotating head 10, shown in more detail in FIG. 4, is
coupled to the surface blowout preventer stack 12 at a joint 70.
Returning fluid, indicated as M.sub.OUT, is passed through a valve
68 to an appropriate collection area. The collection area may
collect both mud with entrained debris, as well as production
fluids such as hydrocarbons. The production fluids may be separated
using well known techniques.
[0031] The upward flow of the fluid M.sub.OUT is constrained by a
pack off 62. In one embodiment, the pack off 62 is a rubber or
resilient ring that seals the annulus around the string 40 and
prevents the further upward flow of the fluids. At the same time,
the pack off 62 enables the application of a rotating force in the
direction of the circular arrow from the rotating head 66 to the
string 40 for purposes of drilling. Sealed bearing 65 may be
provided between a telescoping joint 64 and the rotating head 66 as
both drilling and production may be accomplished in an
underbalanced situation.
[0032] Thus, in some embodiments of the present invention, a subsea
shutoff assembly 24 may be provided to cut off the string in the
event of a failure, such as a blowout. At the same time, surface
annular blowout preventers control fluid flow. Dual gradient
drilling may be achieved through the provision of fluid from the
surface through a side inlet into the region between the upper and
lower ram type shear blowout preventers 30. Through the provision
of the separate tubing 26 with a remotely operable latch 74,
appropriate volumes of fluid can be achieved that would not be
available with conventional kill and choke lines. The tubing 26 for
providing the density control fluid may be both tensioned and
latched. As a result, dual gradient production and drilling may be
achieved in some embodiments of the present invention.
[0033] Referring to FIG. 5, in accordance with another embodiment
of the present invention, lower density drilling mud may be
injected at an appropriate time. Namely, instead of simply
supplying the density lowering fluid on a continuous basis, at the
point when production is ready to begin, lower density drilling
fluid is pumped downwardly through the top device 76 and the drill
string 40.
[0034] A density lowering fluid lowers the density of the drilling
mud moving downwardly into the drill hole towards the drill bit.
The lower density drilling mud is pumped to the drill bit and then
moves upwardly through the drill pipe open hole casing annulus or
spool 34 (FIG. 7). The drill bit may include at least one one-way
check valve.
[0035] Thus, referring to FIGS. 5 and 6, there is no need for any
down hole injection of density lowering fluid since that fluid is
pumped down the drill string 40.
[0036] Similarly, referring to FIG. 7, the spool 34 need have no
accommodation for the injection of density lowering fluid as in the
previous embodiment. Instead, the fluid M.sub.in2 is already of
lowered density when production begins and the fluid reaches the
spool 34. Thus, in some embodiments, prior to the inception of
production, the well may be operating in a balanced or overbalanced
condition. Upon production, the density of the drilling mud may be
reduced by lower density drilling mud through the top drive.
[0037] Finally, referring to FIG. 8, the upward flow of fluid,
first shown in FIG. 7 and indicated as M.sub.out2 is of reduced
density for two reasons. It contains the density lowering fluid
that was pumped downwardly through the drill string 40. Secondly,
it includes the flowing hydrocarbons or fluids which further lower
the density of the drilling mud.
[0038] Therefore, the fluid moving upwardly, indicated as
M.sub.out2 is of a density lower than the density of the downwardly
moving fluid M.sub.in2. Moreover, both M.sub.in2 and M.sub.out2 are
of lower density than the previously pumped drilling mud which was
unaccompanied by density lowering fluid added through the top drive
76.
[0039] The outward flow of drilling fluid, indicated as M.sub.out
in FIG. 8, may pass outwardly through a choke 78. The choke 78,
also shown in FIG. 5, is positioned between the rotating head 10
and the surface blowout preventer stack 12 to maintain control. The
choke 78 back pressure controls the egress of the drilling mud to
control well pressure and inflow from the wellbore.
[0040] In addition, in some embodiments, the drill string 40 will
have two non-return valves installed above in the drill bit at the
bottom of the drill string 40. These valves will reduce the
probability of uncontrolled flow inside the drill string 40.
[0041] Thus, the fluid pressure in the bottom of the hole may be
lower than the pore pressure of the surrounding formation. As a
result, an underbalanced drilling situation is established when
production begins.
[0042] In accordance with still another embodiment, managed
pressure drilling (MPD) may be used instead of overbalanced or
underbalanced drilling. In managed pressure drilling, the pressure
of the drilling mud exactly balances the pore pressure in the
formation. In such case the drilling mud pumped downwardly into the
formation exactly matches the formation pore pressure.
[0043] The pressure within the spool 34 and through the drill
string 40 may be managed by the choke 78 in some embodiments. By
controlling the rate of egress of fluids indicated as M.sub.out,
the pressure within the spool 34 and the remainder of the string 40
may be controlled. In other words, slowing the egress of fluids
increases the pressure and opening the choke decreases the
pressure. In this way, the choke 78 may be utilized in conjunction
with the valve 76 to control the pressure within the system. In one
embodiment, the pressure may be controlled to set a drilling mud
pressure which precisely balances the pore pressure, achieving
managed pressure drilling.
[0044] In some embodiments, a flex joint and telescopic joint may
be used to connect the surface blowout preventer stack 12 to the
valve 76 in other components.
[0045] While the present invention has been described with respect
to a limited number of embodiments, those skilled in the art will
appreciate numerous modifications and variations therefrom. It is
intended that the appended claims cover all such modifications and
variations as fall within the true spirit and scope of this present
invention.
* * * * *