U.S. patent application number 12/156960 was filed with the patent office on 2008-12-11 for dimpled riser floatation module.
Invention is credited to Barry James McMiles.
Application Number | 20080302537 12/156960 |
Document ID | / |
Family ID | 40094791 |
Filed Date | 2008-12-11 |
United States Patent
Application |
20080302537 |
Kind Code |
A1 |
McMiles; Barry James |
December 11, 2008 |
Dimpled riser floatation module
Abstract
An improved subsea riser for use in oil and gas drilling
applications having a cylindrical floatation member adapted for
attachment to a blow out preventer. The member may be configured
with a plurality of generally evenly spaced dimples, indentations
or protrusions about the circumference of the member to provide
more streamlined water flow around the riser reducing turbulence
and oscillations of the riser. The dimples, indentations or
protrusions may be arranged in several ways including icosahedral,
dodecahedral, octahedral and other polyhedral configurations.
Inventors: |
McMiles; Barry James; (Katy,
TX) |
Correspondence
Address: |
JAMES D. PETRUZZI
4900 WOODWAY SUITE 745
HOUSTON
TX
77056
US
|
Family ID: |
40094791 |
Appl. No.: |
12/156960 |
Filed: |
June 6, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60933570 |
Jun 7, 2007 |
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Current U.S.
Class: |
166/350 ;
405/224.2 |
Current CPC
Class: |
E21B 17/012
20130101 |
Class at
Publication: |
166/350 ;
405/224.2 |
International
Class: |
E21B 17/01 20060101
E21B017/01 |
Claims
1. A riser comprising: a generally cylindrical member adapted for
attachment to a blow out preventer from the drilling platform or
rig to provide a conduit on a oil field installation; and a
plurality of generally evenly spaced dimples about the
circumference of said member, wherein said dimples extend along a
predetermined longitudinal dimension of said member.
2. A riser as claimed in claim wherein said dimples are arranged in
an icosahedral pattern based on a polyhedral with identical
triangular faces.
3. A riser as claimed in claim 1 wherein said dimples are arranged
in a dodecahedral pattern based on a polyhedral with identical
pentagonal faces.
4. A riser as claimed in claim 1 wherein said dimples are arranged
in a octahedral pattern based on a polyhedral with identical
triangular faces.
5. A riser as claimed in claim 1 wherein said dimples are indented
in a predetermined amount relative to the radius of the outer
annulus of said member.
6. A riser comprising: a generally cylindrical member adapted for
attachment to a blow out preventer from the drilling platform or
rig to provide a conduit on a oil field installation; and a
plurality of generally evenly spaced indentations about the
circumference of said member, wherein said indentations extend
along a predetermined longitudinal dimension of said member.
7. A riser as claimed in claim 6 further comprising dimples
arranged in an symmetrical pattern on the surface of said
indentation.
8. A riser as claimed in claim 6 further comprising: dimples
arranged in an symmetrical pattern on the surface of said
indentations; said dimples arranged in an icosahedral pattern based
on a polyhedral with identical triangular faces.
9. A riser as claimed in claim 6 further comprising: dimples
arranged in an symmetrical pattern on the surface of said
indentations; said dimples arranged in an a dodecahedral pattern
based on a polyhedral with identical pentagonal faces.
10. A riser as claimed in claim 6 further comprising: dimples
arranged in an symmetrical pattern on the surface of said
indentations; said dimples arranged in an a octahedral pattern
based on a polyhedral with identical triangular faces.
11. A riser comprising: a generally cylindrical member adapted for
attachment to a blow out preventer from the drilling platform or
rig to provide a conduit on a oil field installation; and a
plurality of generally evenly spaced protrusions about the
circumference of said member, wherein said protrusions extend along
a predetermined longitudinal dimension of said member.
12. A riser as claimed in claim 11 further comprising: dimples
arranged in an symmetrical pattern on the surface of said
protrusions.
13. A riser as claimed in claim 11 further comprising: dimples
arranged in an symmetrical pattern on the surface of said
protrusions; said dimples arranged in an icosahedral pattern based
on a polyhedral with identical triangular faces.
14. A riser as claimed in claim 11 further comprising: dimples
arranged in an symmetrical pattern on the surface of said
protrusions; said dimples arranged in an a dodecahedral pattern
based on a polyhedral with identical pentagonal faces.
15. A riser as claimed in claim 11 further comprising: dimples
arranged in an symmetrical pattern on the surface of said
protrusions; said dimples arranged in an a octahedral pattern based
on a polyhedral with identical triangular faces.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application takes priority from a provisional
application for patent bearing Ser. No. 60/933,570 filed Jun. 7,
2008 entitled Dimpled Riser Floatation and is incorporated as if
fully set forth herein.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
DESCRIPTION OF ATTACHED APPENDIX
[0003] Not Applicable
BACKGROUND OF THE INVENTION
[0004] This invention relates generally to the field of sub sea
risers and more specifically to an improved dimpled floatation
module. Offshore oil/gas drilling and production face hazards due
to the exposure of submerged rig components to underwater sea
currents. With the present invention production disruptions from
strong underwater currents can be mitigated by reducing turbulence
about the riser and oscillations which can disrupt production and
potentially lead to catastrophic failure of the submerged rig
components.
BRIEF SUMMARY OF THE INVENTION
[0005] The primary advantage of the invention is to provide a
floatation that is more hydrodynamic.
[0006] Another advantage of the invention is to provide reduced
drag on the riser column.
[0007] Another advantage of the invention is that it will require
less tension to keep the riser vertical and therefore reduce the
load on the rig.
[0008] Another advantage of the invention is that it will possibly
reduce the number of tensioners required on the rig itself.
[0009] In accordance with a preferred embodiment of the invention,
there is shown a riser having a generally cylindrical member
adapted for attachment to a blow out preventer from the drilling
platform or rig to provide a conduit on a oil field installation
and a plurality of generally evenly spaced dimples about the
circumference of the member, wherein the dimples extend along a
predetermined longitudinal dimension of the member.
[0010] In accordance with another preferred embodiment of the
invention, there is shown a riser having a generally cylindrical
member adapted for attachment to a blow out preventer from the
drilling platform or rig to provide a conduit on a oil field
installation and a plurality of generally evenly spaced
indentations about the circumference of the member, wherein the
indentations extend along a predetermined longitudinal dimension of
the member.
[0011] In accordance with another preferred embodiment of the
invention, there is shown a riser having a generally cylindrical
member adapted for attachment to a blow out preventer from the
drilling platform or rig to provide a conduit on a oil field
installation and a plurality of generally evenly spaced protrusions
about the circumference of the member, wherein the protrusions
extend along a predetermined longitudinal dimension of the
member
[0012] Other objects and advantages of the present invention will
become apparent from the following descriptions, taken in
connection with the accompanying drawings, wherein, by way of
illustration and example, an embodiment of the present invention is
disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The drawings constitute a part of this specification and
include exemplary embodiments to the invention, which may be
embodied in various forms. It is to be understood that in some
instances various aspects of the invention may be shown exaggerated
or enlarged to facilitate an understanding of the invention.
[0014] FIG. 1 is a schematic diagram illustrating fluid flow around
a sphere.
[0015] FIG. 2A is a schematic diagram of fluid flow about a smooth
sphere and resulting turbulence.
[0016] FIG. 2B is a schematic diagram of fluid flow about a dimpled
sphere and resulting reduced turbulence.
[0017] FIG. 3 is a curve depicting drag resulting from flow about a
smooth and nonsmooth surfaced sphere.
[0018] FIGS. 4A, 4B, 4C, and 4D are plan views of exemplary dimpled
configurations.
[0019] FIG. 5A is plan view of a floatation module according to a
preferred embodiment of the invention.
[0020] FIG. 5B is a side elevational view of a floatation module
according to a preferred embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Detailed descriptions of the preferred embodiment are
provided herein. It is to be understood, however, that the present
invention may be embodied in various forms. Therefore, specific
details disclosed herein are not to be interpreted as limiting, but
rather as a basis for the claims and as a representative basis for
teaching one skilled in the art to employ the present invention in
virtually any appropriately detailed system, structure or
manner.
[0022] Offshore oil/gas drilling and production face hazards due to
the exposure of submerged rig components to underwater sea
currents. Critical among these components are the marine risers,
consisting of a series of long steel pipes of circular
cross-section, used for deep-water extraction of oil and/or natural
gas. These long cylindrical structures, exposed to strong sea
currents, induce the flow around them to separate and initiate
vortex shedding--whereby vortices of opposite sign are shed
synchronously from the aft of the structure. The resultant lift and
drag forces create turbulence about the riser and floatation
mechanism and excite forced oscillations of the cylinder. To
mitigate such vibrations the current invention seeks to reduce
turbulence about the floatation module. Increasing development
costs and increasingly hostile field environments, demand more
robust, reliable, and refined designs and tools. This invention
addresses the need by reducing drag and turbulence about the
floatation module as described herein.
[0023] To reduce drag around the floatation module, the present
invention places golf ball like dimples about the periphery of the
floatation module. A variety of dimple configurations are feasible
as more fully described below. The dimples reduce drag and wear
caused by moving water by creating turbulence in the water around
the floatation module. Surface dimples force the water to hug the
floatation module more closely, so instead of flowing past it, the
water follows the curvature of the floatation module around to the
back. The result is a smaller wake and less drag.
[0024] The most common dimple patterns are icosahedral,
dodecahedral, and octahedral. The icosahedral pattern is based on a
polyhedral with 20 identical triangular faces, much like a 20-sided
die. Similarly, a dodecahedral is based on a polyhedral with 12
identical faces in the shape of pentagons. The octahedral is based
on an eight-sided polyhedral with triangular faces. As a general
rule, the more dimples something has, the less drag and better
fluid dynamic properties as these properties apply to any fluid
with some viscosity including aerodynamic and hydrodynamic
applications.
[0025] The size, shape and depth of the dimples may also affect
performance. Hexagonal and pentagonal shapes have been found to
further reduce the drag. Shallow dimples on a golf ball, for
example, generate more spin on a golf ball than deep dimples, which
increases lift and causes the ball to rise and stay in the air
longer and roll less. Deep dimples generate less spin on a golf
ball than shallow dimples, which decrease lift and causes the ball
to stay on a low trajectory, with less air time and greater roll.
Small dimples generally give the ball a lower trajectory and good
control in the wind, where as large dimples give the ball a higher
trajectory and longer flight time.
[0026] The dimples have a fluid dynamic (hydrodymanic or
aeordynamic) effect. Water or air moving over the over the subject
surface causes friction, which in turn produces negative pressure
behind the object, called drag. "Laminar drag" over a smooth
surface separates out much quicker than "turbulent drag" over a
dimpled surface. This produces less pressure, and the air or water
moves more easily around the subject surface.
[0027] Dimples create a turbulent boundary layer as fluid (e.g. air
or water) flows past the surface of the floatation module. This
allows fluid to "hug" the surface further around the floatation
module as it passes, reducing the size of its wake and,
consequently, its drag. For this reason a surface with dimples of
the right depth is more aerodynamic than a smooth surface.
[0028] FIG. 1 shows a dimpled sphere (shown here as a golf ball)
102 traveling through a low viscosity medium such as air or water
creating an equivalent fluid flow 104, in this case streaming air.
As later described the fluid flow 104 more closely follows the
countour of the sphere 102 since the surface is non smooth.
[0029] FIG. 2A and FIG. 2B show the boundary layer which is the
thin layer of air next to the ball. FIG. 2A shows a smooth ball 200
in a fluid flow 202 which produces a continuous, laminar boundary
layer 204. Since the fluid flow 202 slides off the smooth ball 200
rather than following the ball's hemisphere surface opposite the
fluid flow 202 a large area of turbulant air or wake 206 is created
behing the ball 200. FIG. 2B shows a dimpled ball 210. Rather than
flowing in a continuous, laminar boundary layer, it has a
microscopic pattern of fluctuations and randomized fluid flow 212.
In short, a turbulent boundary layer 214 has better tires; meaning
that the fluid flow 212, in this example, air grabs portions of the
dimpled ball 210 and slows down the rotation almost like a
well-treaded tire gripping against a road. The fluid flow 212
conforms to the ball's hemisphere surface opposite the direction of
the fluid flow 212 creating a much smaller area of turbulant air or
wake 216 behind the ball. Air travels around the ball further
before separating, creating a smaller wake 216 and much less drag
while the spinning motion warps the airflow to generate lift.
[0030] FIG. 3 graphically depicts the phenomenon described above
which gives a dimpled golf ball only about half the drag of a
smooth one. The Y axis of the graph shows the drag coefficient
scale 300 and the X axis shows a logarithmic Reynolds number scale
302. A perfectly smooth golf ball with no dimples would travel
about 130 yards when hit with a driver by a good player due to the
lower drag coefficient to Reynolds number relationship depicted as
the smooth sphere line 304. On the other hand, a ball with
well-designed dimples, struck the same way, will travel about 290
yards due to the higher drag coefficeint to Reynolds number
relationship depicted as the golf ball line 306.
[0031] Dimple design has changed significantly over time, from
random patterns, to formal rows, to interstitial designs. The
depth, shape and number have all been varied and tested. With
regard to the number of dimples, as one increases the number of
dimples, the smaller they must be to fit on the chosen surface
area. Eventually, as the number increases, the dimples get smaller
and the surface becomes almost smooth--and will perform likewise.
So a compromise is the answer.
[0032] It has generally been found that less than about 300 dimples
is too few, and more than about 500 is too many is typical in the
case of a standard golf ball. Most balls on the market today have
thus converged to the middle ground with between 350 and 450
dimples. FIGS. 4A, 4B, 4C and 4D show exemplary designs and
layouts. FIGS. 4A and 4B a ball with 392 dimples in an Octahedral
layout 400 and 402. The octahedral is based on an eight-sided
polyhedral with triangular faces. FIGS. 4C and 4D show a ball with
432 dimples in an icosahedral layout 404 and 406. As described
herein the icosahedral pattern is based on a polyhedral with 20
identical triangular faces, much like a 20-sided die.
[0033] A similar density of dimples would be advantageous about the
periphery of the floatation module as shown in FIG. 5A. FIG. 5A
shows a cross sectional plan view of a floatation module 500 with a
plurality of surface depressions or dimples 502 positioned about
the surface in a manner to effect the maximum reduction of drag. As
shown in FIG. 5B, a partial side elevational view of a floatation
module 520, there are numerous dimples 522 positioned about the
surface of the floatation module. The surface dimples 502 and 522
break up the flow of water around the floatation module and create
a turbulence that reduces drag on the floatation module 500 and
520. This greatly reduces the wear and tear on the floatation
module and as described herein may reduce turbulence and vibration
of the floatation module, and the riser.
[0034] In an alternative embodiment, small protrusions may be
symmetrically placed about the circumference of the riser, each
having a pattern of dimples on the protrusions. In this way, the
protrusions act as small spheroids with dimples to achieve the
overall purpose of breaking up laminar flow and creating
turbulences that produce enhanced hydrodynamic effects. The
protrusions may be of any of a variety of sizes shapes to achieve
the desired goal.
[0035] This solution can be used in a variety of subsea
applications where significant water flow is a problem and through
the present invention can be reduced thus extending the life of
undersea equipment. As with a golf ball, by optimizing the number
and formation of the dimples, drag can be reduced and the erosive
effects of water flow about the floatation is reduced.
[0036] While the invention has been described in connection with a
preferred embodiment, it is not intended to limit the scope of the
invention to the particular form set forth, but on the contrary, it
is intended to cover such alternatives, modifications, and
equivalents as may be included within the spirit and scope of the
invention as defined by the claims.
* * * * *