U.S. patent application number 12/323067 was filed with the patent office on 2009-04-23 for composite drill pipe and method of forming same.
This patent application is currently assigned to ADVANCED COMPOSITE PRODUCTS & TECHNOLOGY, INC.. Invention is credited to James Heard, Marvin Josephson, James C. Leslie, II, James C. Leslie, Liem Truong.
Application Number | 20090101328 12/323067 |
Document ID | / |
Family ID | 40562276 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090101328 |
Kind Code |
A1 |
Leslie; James C. ; et
al. |
April 23, 2009 |
COMPOSITE DRILL PIPE AND METHOD OF FORMING SAME
Abstract
A lightweight and durable drill pipe string capable of short
radius drilling formed using a composite pipe segment formed to
include tapered wall thickness ends that are each defined by
opposed frustoconical surfaces conformed for self aligning receipt
and intimate bonding contact within an annular space between
corresponding surfaces of a coaxially nested set of metal end
pieces and a set of nonconductive sleeves. The distal peripheries
of the nested end pieces and sleeves are then welded to each other
and the sandwiched and bonded portions are radially pinned. The
composite segment may include imbedded conductive leads and the
axial end portions of the end pieces are shaped to form a threaded
joint with the next pipe assembly that includes contact rings in
the opposed surfaces of the pipe joint assembly, the contact of
which is effected by either piercing with a pointed contact from
one end into the other to connect the corresponding leads across
the joint or contacting opposed rings in each end.
Inventors: |
Leslie; James C.; (Fountain
Valley, CA) ; Leslie, II; James C.; (Mission Viejo,
CA) ; Heard; James; (Huntington Beach, CA) ;
Truong; Liem; (Anaheim, CA) ; Josephson; Marvin;
(Huntington Beach, CA) |
Correspondence
Address: |
FULWIDER PATTON LLP
HOWARD HUGHES CENTER, 6060 CENTER DRIVE, TENTH FLOOR
LOS ANGELES
CA
90045
US
|
Assignee: |
ADVANCED COMPOSITE PRODUCTS &
TECHNOLOGY, INC.
Huntington Beach
CA
|
Family ID: |
40562276 |
Appl. No.: |
12/323067 |
Filed: |
November 25, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10952135 |
Sep 28, 2004 |
7458617 |
|
|
12323067 |
|
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|
Current U.S.
Class: |
166/65.1 ;
166/242.6; 29/428 |
Current CPC
Class: |
E21B 17/003 20130101;
F16L 13/103 20130101; F16L 15/08 20130101; E21B 17/02 20130101;
F16L 25/0018 20130101; E21B 17/206 20130101; Y10T 29/49826
20150115; F16L 31/00 20130101; E21B 17/028 20130101; E21B 17/20
20130101 |
Class at
Publication: |
166/65.1 ;
166/242.6; 29/428 |
International
Class: |
E21B 17/02 20060101
E21B017/02; B23P 11/00 20060101 B23P011/00; B29C 65/00 20060101
B29C065/00; E21B 12/00 20060101 E21B012/00 |
Goverment Interests
STATEMENT OF GOVERNMENT INTEREST
[0002] This invention was partly funded by the Government of the
United States of America under Cooperative Agreement No.
DE-FC26-99FT40262 awarded by the U.S. Department of Energy and the
Government of the United States of America has certain rights in
the invention.
Claims
1. A drill pipe string forming a metal to composite interface,
comprising: a plurality of longitudinally aligned filament wound
composite pipe segments configured at their respective opposite
extremities with tapered sections formed by cylindrical walls
tapering distally to thin annular edges; pairs of male and female
couplers interposed between adjacent ends of respective pipe
segments including inner and outer concentric cylindrical members
formed by respective outer and inner walls, the respective walls
formed with respective confronting bonding surfaces angling
distally in one direction in conical fashion away from one another
to cooperate in forming conical nesting cavities for complementary
receipt of the respective tapered sections of the adjacent pipe
segments of said string; a bond bonding the pipe segment walls to
the male and female couplers; and said male and female couplers
including respective threaded male nipples and female openings for
screwable connection of respective adjacent male and female
couplers together.
2. The drill pipe string of claim 1, further comprising: at least
one electrical lead conductor embedded within respective pipe
segments including respective exposed connector portions protruding
from respective pipe segment opposite extremities; respective
electrical contact surfaces positioned within respective male
nipples and female openings disposed for electrical engagement to
an adjacent electrical contact surface when adjacent male nipples
and female openings are connected together; and wherein the
respective male and female couplers include lead passages
configured for routing respective exposed portions into electrical
contact with the respective contact surfaces of connected male
nipples and female openings making said electrical contact
therein.
3. A drill pipe string forming a metal to composite interface,
comprising: a plurality of filament wound composite pipe segments
configured at their respective opposite extremities with tapered
sections formed by cylindrical walls tapering distally to thin
annular edges; pairs of male and female couplers including
respective proximate ends interposed between adjacent ends of
respective pipe segments and further including inner and outer
concentric cylindrical members formed by respective outer and inner
walls, the respective walls formed with respective confronting
bonding surfaces angling distally in one direction in conical
fashion away from one another to cooperate in forming conical
nesting cavities for complementary receipt of the respective
tapered sections of the adjacent pipe segments of said string
wherein one of the respective cylindrical members projects distally
farther from its coupler proximate end than the other cylindrical
member; a bond bonding the pipe segment walls to the male and
female couplers; and said male and female couplers including
respective threaded male nipples and females openings for screwable
connection of respective adjacent male and female couplers
together.
4. The drill pipe string of claim 3, wherein: the inner cylindrical
member projects distally farther than the outer cylindrical
member.
5. The drill pipe string of claim 3, wherein: the composite
segments include a predetermined amount of carbon material.
6. The drill pipe string of claim 3, further comprising: an
electrical conductor mounted to respective pipe segments and routed
through respective male and female couplers to effect an electrical
connection between adjacent the adjacent ends of respective pipe
segments.
7. The drill pipe string of claim 3, wherein: respective pipe
segment ends include a predetermined diameter and respective pipe
segment walls taper narrowing in cross-section from the pipe
segment ends to an intermediate point therefrom.
8. The drill pipe string of claim 3, wherein: the female couplers
include male bosses and the male couplers include female bosses
configured for operative receipt of a male boss from an adjacent
pipe segment end.
9. A drill pipe string for end to end connection, comprising:
composite walls forming elongated pipe segments having first and
second extremities; one or more conductor lead segments imbedded in
the walls of respective pipe segments and extending between the
respective first and second extremities therein and projecting
distally therefrom to form mating connector links; first and second
connectors connected to the respective mating connector links and
operative upon respective extremities of the pipe segments being
connected together to form respective electrical couplings.
10. The pipe string of claim 9, wherein: the respective connectors
are formed with metallic male and female end fittings at the
respective first and second extremities, including metallic walls
with connector stems on the respective fitting proximal ends and on
their respective distal ends with respective male and female bosses
connected together.
11. The pipe string of claim 10, wherein: the first connectors
include respective electrically conductive contact rings in
electrical contact with respective lead segments and constructed to
be, when the respective male and female fittings are connected
together, in operative electrical contact with one another.
12. The pipe string of claim 10, wherein: the male and female
bosses are threadably connected.
13. The pipe string of claim 9, further comprising: respective
hollow sleeve walls including proximate extremities and distal
extremities, the sleeve walls positioned between the respective
composite wall first and second extremities and respective
connectors.
14. The pipe string of claim 13, wherein: skirts formed on the
respective sleeve walls proximate extremities define a first pair
of sockets receiving the respective composite wall first and second
extremities; a second pair of sockets formed on the respective
sleeve wall distal extremities receive the respective connectors,
the sleeve walls further include respective passages for routing of
respective mating connector links into operative electrical contact
upon respective extremities of the pipe segments being connected
together.
15. The pipe string of claim 11, wherein: the metallic walls of
respective fittings incorporate connector passages receiving the
respective mating connector links disposed in electrical contact to
respective contact rings.
16. The pipe string of claim 15, wherein: the metallic fittings are
formed at their respective distal ends with flanges incorporating
shoulders and circumscribing the base of the respective bosses; the
respective connector passages are configured to pass through
respective metallic fitting flanges; and the sleeves incorporate
flanges on respective distal extremities configured for abutment
against the shoulders of respective end fittings, the sleeve
flanges incorporating the passage for routing respective connector
mating links.
17. The pipe string of claim 13, wherein: the composite walls are
formed with an exterior surface tapering narrowingly from an
intermediate point on the exterior surface toward the pipe first
and second extremities and an interior surface tapering expandingly
from an intermediate point of the walls toward the pipe first and
second extremities; the sleeves are formed with a tapered interior
surface on their respective proximate extremities configured to
receive the respective pipe segment extremities and indexed to
fittingly match the tapered exterior surface of respective pipe
segment first and second extremities; and the connectors are formed
with a tapering exterior surface narrowing from an intermediate
point along a connector exterior surface to the connector proximal
ends and configured for receipt within the sleeves and indexed to
the interior surface of respective pipe segment extremities.
18. The pipe string of claim 11, further comprising: insulator
rings made of an electrically insulative material positioned
adjacent respective bosses; and the connector mating links
projecting through respective insulator rings in electrical
engagement with respective contact ring.
19. The pipe string of claim 18, wherein: the insulator rings are
made from an elastomeric material.
20. The pipe string of claim 18, further comprising: piercing means
incorporated within the flanges of the respective female boss for
piercing the insulator ring of the male boss.
21. The pipe string of claim 18, wherein: the insulator rings
include one or more axially projecting pockets; the conductive
contact ring incorporates one or more legs projecting in electrical
connection from the contact ring configured for receipt within the
respective pockets; respective fittings include an abutment surface
incorporating one or more bores operative for receipt of the
insulator ring pockets; and at least one mating connector link
projecting longitudinally through the bores of the respective
abutment surfaces and through the respective insulator ring pockets
in conductive contact with the contact ring legs.
22. The pipe string of claim 20, wherein: the insulative material
is constructed to flow out from the respective insulator rings when
pierced and fills voids surrounding the contact rings of adjacent
fittings.
23. The pipe string of claim 9, wherein: the mating connector links
are optical fibers.
24. The pipe string of claim 13, wherein: the composite pipe
segments, sleeve walls, and connectors are formed with respective
sets of holes configured to be aligned upon receipt of the
composite pipe segment through the sleeve and connectors; and
further comprising a set of fasteners configured for receipt within
the respective holes for cooperating in coupling the pipes,
sleeves, and connectors together.
25. The pipe string of claim 13, wherein: the sleeves further
include respective longitudinal grooves on their exterior surface
aligned with the respective passages for routing the respective
connector mating links projecting longitudinally within respective
grooves through the respective sleeve shoulders.
26. A method for fixing the ends of composite pipe segments within
metal end fitting assemblies, comprising the steps of: forming the
exterior and interior surface portions of each end of said segment
ends to define opposed frustoconical surfaces; inserting each end
of said composite pipe segment into an annular gap formed between
concentrically nested exterior and interior tubular end pieces
conformed to thereby center the nested end pieces along the
corresponding ones of said frustoconical surfaces on each said pipe
segment end; bonding the interior and exterior end surfaces of each
end of said pipe segment to the corresponding surfaces of said
exterior and interior end pieces; welding together the peripheral
edges of said interior and exterior end pieces distal of said
interior and exterior surfaces while concurrently cooling those
portions of said end pieces that are bonded to the ends of said
segment; and pressing in interference fit a plurality of radially
aligned pins through the bonded combination of said segment ends
received between said exterior and interior end pieces.
27. A method according to claim 26 wherein: the step of bonding
includes the further step of aligning the adjacent portions of said
interior and exterior pieces into intimate contact with the
corresponding ones of said frustoconical surfaces.
28. A method according to claim 26 wherein: said step of forming
further includes wrapping graphite fibers together with imbedded
conductors; and said step of bonding further includes conveying the
ends of said conductors through said interior pieces.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The teachings herein constitute a continuation in part of
the matter disclosed in U.S. patent application Ser. No. 10/952,135
filed Sep. 28, 2004, and the benefit of this earlier filing data is
claimed for all matter common therewith.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to drill pipe strings and the
method for forming the same, and more particularly to providing a
lightweight string for extended reach and short radius drilling and
to protecting connections for transmitting signal and/or power
across the joints forming the pipe string.
[0005] 2. The Prior Art
[0006] Oil well drilling is often performed from drilling
platforms, which, for deep water applications may involve costs of
several hundred thousand dollars per day. Thus, there is a great
demand for drill pipe strings which are lightweight yet durable
enough to reach greater distances by directional drilling from the
platforms to thereby add to the return on investment. The design
discipline for short radius and extended reach are often different
but both benefit from favorable strength to weight ratios.
[0007] The ability to adjust drilling rate, reach and direction in
the pursuit of oil traps has long been rendered inefficient by the
lack of a reliable and durable pipe string and method for obtaining
feedback during drilling. The depth and reach of exploration are
restricted primarily by the cumulative weight and unit strength of
a drill pipe string. Steel pipe has been effective for its
durability but its weight-to-strength ratios has reached its
boundaries in ultra-deep, deep directional and/or extended reach
drilling because of its weight or by the weight induced friction of
the rotating pipe string as it rests on the walls of the well bore
or rubs against the casing wall. The stiffness associated with
steel has also made adjusting to or performing short radius turns
difficult and dangerous as drill operators are essentially guessing
at the changes in subterraneous conditions as the pipe progresses
without consistent signal feedback. The drilling entrepreneur,
therefore, has been limited for some time by the stiffness, the
unit weight, and the fatigue, shear and tensile strength limits of
metal pipe.
[0008] Furthermore, deep drilling and directional drilling require
monitor and feedback of the drilling environment. As a drill string
progresses, the rotational velocity, torque, and stress variations
require measurement to guide the drill workman in adjusting the
drill operation. Measuring while drilling (MWD) also allows the
drill operator to periodically check the likelihood of successfully
locating an oil trap. The dilemma thus far has been in successfully
leading a signal down the pipe. Prior efforts have focused on
leading instrumentation or signal lines down through hollow pipe
interiors. Signals that are traditionally carried down through the
pipe tend to suffer adverse consequences of the rigorous and
treacherous environment associated with drilling. As the pipe
progresses, chunks of sharp, hard earth and particulates
regurgitate back toward the surface along the pipe circumference or
through its interior. As a result, various material alternatives
have been proposed both to reduce the linear weight and flexure of
the string as well as to improve its fatigue, shear and tensile
limits and methods proposed to carry a signal between pipe string
segments. The search for light weight and high strength material
substitutes has led to composite pipe structures since composites
also offer the added benefits of being more resistive to
corrosion.
[0009] Composites, while sufficiently lightweight and durable for
deep and directional drilling, are less effective at forming the
mechanical joints required in drill pipes. While virtually all
drilling operations require limited length pipe segments determined
by the size of the drilling rig and/or the handling power of any
lifting equipment, the step of joining such pipe segments into a
long string is a fundamental aspect of all drilling. For this
reason, the more recent development focus has been directed to the
interface between the composite wall of the pipe and metal end
fittings on a segment end. The interface of these two structures
provides an economically and mechanically viable structure for
extended reach and short turn radius drilling.
[0010] Composite materials have a further advantage that heretofore
has not been extensively recognized, namely the convenient
imbedding of signal and/or power conductors into the laminates
forming the pipe wall. Imbedding the signal within the pipe walls
is particularly useful with short radius directional drilling since
it allows for an uninterrupted, continuous down hole signal
feedback and control augmentation while drilling, thus maximizing
the effectiveness of the invariably very high drilling costs at the
remaining remote or deeply submerged formations. Additionally, the
non-conductive nature of composites insulates electrical signals
when used, preventing dissipation of power into the pipe walls.
This synergistic aspect of composite pipe has not been fully
recognized nor exploited in the art simply because the technical
challenge of forming an effective connection between the composite
tube wall and the end fitting has overwhelmed all other
considerations. The process of imbedding conductors or connecting
them across a joint from a metal/composite interface coupled with
protecting the signal line down the pipe string length has
therefore been relegated to inattention.
[0011] At the core is the inherent difficulty in forming a high
integrity interface between the composite pipe wall and the
adjoining surfaces of the end fitting. In the past, fitting
assemblies with variously opposing surface geometries have been
proposed to effect a secure capture of the composite end within the
fitting. Some examples of such end fittings include those taught in
U.S. Pat. No. 5,233,737 to Policelli; U.S. Pat. No. 4,810,010 to
Jones; U.S. Pat. No. 6,315,002 to Antal et al.; and others. While
suitable for the purposes intended each of the foregoing assemblies
include threaded or otherwise releasably engaged parts clamping the
composite between each other with inherently uneven load
concentrations resulting in highly uneven shear stresses. This
uneven load distribution between adjacent parts, of course, results
in correspondingly uneven local strain deformations when exposed to
the various high loadings in the course of use. There is therefore
an inherent incidence of local bond separation between the
composite itself and the adjoining fitting surface, with some
consequence for failure.
[0012] Alternatively, end fitting assemblies have been proposed in
which radial pins or other radial fasteners are added to the
assembly, as exemplified by the teachings of U.S. Pat. No.
5,332,049 to Tew; U.S. Pat. No. 5,288,109 to Auberon et al.; U.S.
Pat. No. 5,443,099 to Chaussepied et al.; and others. Once again,
while a change is realized from these radial interconnections the
essentially separated nature of a single metal to composite surface
interface is also susceptible to uneven load transfer with the
consequent local separations an inherent possibility. For example,
the '109 patent to Tew appears to disclose a single metal-composite
interface held together by radial pins and an adhesive bond which
may suffer from disparate torsional forces. Tew appears to propose
an outer protective sheath lacking a tapered surface interface and
suffers the shortcoming that, particular to long reach
applications, the coupling itself fails to provide a high strength
joint capable of carrying the high torsional force necessary to
withstand the loads of both extended reach applications and short
radius. Moreover, such assemblies suffer from a lack of another
significant attribute, namely the bridging of a protected
electrical signal between pipe connections.
[0013] In the past various conductor connection arrangements
bridging a pipe joint have been proposed for transmitting power and
signals down pipe strings. Examples of such arrangements can be
found in the teachings of U.S. Pat. No. 6,367,564 to Mills et al.;
U.S. Pat. No. 4,220,381 to van der Graaf, U.S. Pat. No. 2,748,358
to Johnston; and U.S. Pat. No. 5,334,801 to Mohn. Each of these,
and others similarly implemented, either refer to indirect coupling
like that obtained by capacitive coupling or by Hall effect, or
speak of full insulation of paired leads in light of the conductive
nature of the pipe string, or incorporate a conductive tube
surrounded between two insulative regions as in the '564 patent to
Mills. Additionally, where electrical leads are incorporated
throughout the pipe string, the signal and power carrying
arrangements suffer from being lead down the string either within
the pipe hollow passage or external the pipe exposed to damaging
objects. Thus while suitable for the purposes intended these prior
art teachings do not avail themselves to all the advantages of a
composite, non-conducting pipe string and the protective
capabilities of embedding a conductor in the composite walls and it
is these advantages that are realized herein. Such arrangements are
either prone to damage or add significant weight and contribute to
inflexibility in the pipe string by incorporating full length metal
tubes within the structure.
[0014] It can be seen then that a need exists for a lightweight and
durable structure capable of withstanding the rigors of deep and
directional drilling that is also capable of carrying a protected
signal down a pipe string length.
SUMMARY OF THE INVENTION
[0015] Briefly and in general terms, the present invention is
directed to a segment of drill piping constructed of composite
materials connected end to end with metallic end fittings in a
manner that provides a diffusion of torsional loads on a
metal-composite junction and protects a signal carrier throughout
the length of the pipe. A metallic end fitting is connected to the
composite pipe section to form a first metal-composite interface
partially carrying torsional loads. The interface is reinforced by
a metallic sleeve attached concentrically about the first interface
to form a second metal-composite interface also carrying torsional
loads. The composite pipe segment includes at least one conductive
lead embedded in its walls that are exposed at each pipe segment
end and connected to extremities of the end fittings.
[0016] The conductor is carried down a strong lightweight drill
pipe string with a composite to metal interface by forming
reinforced composite tubular segments. Each segment is made from a
generally uniform wall thickness and the conductor is embedded
within these composite walls with ends exposed at each segment end.
Each wall may be constructed with both ends linearly tapered to a
reducing wall thickness over a fixed axial increment. Both the
interior and exterior tapers of these substantially identical end
surfaces are then each mated and bonded to corresponding linearly
tapered portions of cylindrical metal end fitting pieces and
metallic sleeve fittings being further conformed for a closely
fitted annular nested assembly. Once fully nested the dimensions of
the tapered gap thus formed between the fittings closely match the
end tapers of each composite segment, assuring an intimate surface
contact and therefore an effective bond over the full surface of
the metal to composite interfaces, the centralizing taper assuring
this bond with or without bond line control. The end of the metal
fitting is formed to extend beyond its nested receipt within the
exterior piece to form either the male or female end of a threaded
drill pipe connection, commonly referred to as the `pin end` and
the `box end` of the pipe segment. The exposed conductor ends are
conveyed through the sleeve and end fittings to make contact with a
conductive contact ring. Upon coupling of adjacent male-female
fittings, the outward facing surface of the contact rings engage
one another effecting an electrical contact across the joint.
[0017] The metal end fittings are formed with threaded bores so
that a male end on one pipe segment will fit into the female end of
an adjacent pipe segment. The end fittings include a flange with a
shoulder at the flange base. Formed within each flange is an
annular recess defined by an abutment surface formed at the flange
interior base. The abutment surface includes multiple bores
extending through the flange shoulders. The end fitting further
includes a skirt projecting distally away from the flange with
interior and exterior surfaces formed to fit concentrically with
the ends of the pipe segment and the sleeve as described above.
[0018] The sleeve includes a flange and shoulder at its base and a
skirt projecting distally therefrom. The sleeve interior surface is
formed to cooperate with the exterior surface of the pipe segment
and assists in reinforcing the metal to composite interface of the
pipe segment and end fitting. The sleeve flange rests against the
fitting shoulder and a bore at the sleeve shoulder allows the
exposed lead ends to pass through the sleeve flange and into the
end fitting shoulder to make contact with a conductive contact ring
leg described more fully herein.
[0019] Those skilled in the art will appreciate that the foregoing
assembly results in a fairly large composite-to-metal interface
surface for effecting the bond, thus widely diffusing any load
concentrations thereacross. To reinforce the joint interface,
further steps are provided for integrating the assembly into a
unitary structure once the initial bond has been made. More
precisely, the distal portions of the nested inner and outer pieces
are each in direct contact with adjacent exterior flange rings
which are then welded to each other while the portions thereof
forming the interface cavity with the composite end bonded therein
are cooled by water spray. Following this welding step the bonded
portion may receive a plurality of radial pins press fit and
secured through matched openings in the tapered skirts of the inner
and outer piece and also through corresponding openings in the
tapered end of the composite pipe segment bonded therein to fully
tie the separate items into an integral structure, with the press
fit receipt of the pins in the more resilient composite insuring an
internal compression prestress across the bond. In this manner all,
the conveniences of a part-wise assembly are retained while the
resulting end structure has all the advantages of an integral unit.
More importantly, this manner of assembly insures a
self-centralizing benefit where the tapered ends of the composite
segment themselves provide the reference structure against which
the inner and outer pieces are aligned. Once this centralized
alignment is fixed by bonding the intimately aligned surfaces to
each other the subsequent welding, and pinning if desired of the
nested pieces assures the end structure the integrity necessary to
transfer the large stresses developed across the joint.
[0020] The same convenience of part-wise assembly that results in
an integral structure is also useful in realizing further benefits
associated with composite tubes, namely the benefit of bridging
across the pipe joint electrical or signal continuity between
embedded signal or power leads in each segment. In a first example,
the part-wise assembly process allows insertion of exposed ends of
imbedded conductors into passages formed in the sleeve for
connection to axially aligned spring biased pins mounted on pistons
within a sealed manifold of the end fitting. Application of
pressure to the manifold then extends the pins against their spring
bias to pierce the insulation covering on concentric annular
contact rings deployed in the opposed mating surface of the next
adjacent end fitting threadably mated therewith, with the contact
rings in turn connected for electrical contact with corresponding
conductors imbedded in the next segment, and so on.
[0021] In a second example both the opposed faces surrounding the
threaded connection each include opposing annular recesses within
which coaxial contact rings are received within an annular
insulating ring formed with annular walls that define an annular
gap. The insulating ring includes multiple hollow open-ended legs
extending axially out and fit into the bores in the abutment
surface of the end fitting. A conductive contact ring with multiple
legs projecting axially to fit into the insulation ring bores rests
within the insulation ring. The insulating ring and contact ring
assembly are inserted into the annular recess with the insulating
ring legs fitting into the bores of the abutment surface.
Preferably the contact rings project slightly beyond each of the
opposing surfaces and as the pipe joint of the next segment is
threadably coupled to the pipe string the resulting compression of
the rings against each other then effects the contact between the
opposed joint ends. To assure complete sealing of each ring by the
walls of the insulating seal the peripheries of some of the ring
surfaces may be chamfered to provide annular voids into which the
excess insulation material can flow as the joint ends are threaded
together. Each of the rings, moreover, may be perforated to engage
a corresponding lead end extending through the insulator which then
similarly seals by material flow this part of the surface and the
buried edge of the rings may include axial projections that extend
into conforming pockets formed in the seal to engage depressions in
the groove bottom and thereby fix the ring and seal combination
against rotation in the groove as the threaded pipe joint is
made.
[0022] Thus a quick and expedient contact mechanism is devised
either effected by the pressurizing step or by the threaded
advancement of the joint ends onto each other thereby providing for
a convenient transmission of signal or power down the well bore.
The foregoing connection sequence may be utilized with composite
segments of a layered construction, resulting in a fully sealed
pipe string, a manner of construction that obtains further
convenience for fabrication mandrel release by introducing internal
pressure once the core layer has been formed with the pressurized
core then serving as its own mandrel for next the successive
wrappings of fiber and further interleaved membranes.
[0023] Those in the art will appreciate that this layered
construction process allows for introduction of sealant between
selected layers while appropriate compliance selection of the other
layers and the fiber wrapping angle can then be used to control the
bending compliance and thus the turning radius of the resulting
piece. In this manner, all the desired functions and attributes can
be accommodated in the assembly process which then renders pipe
segments that are particularly useful in the ultra deep and
extended reach drilling efforts that are currently required.
[0024] In a third example of the present invention, load diffusion
across the metal-composite interface is further enhanced by
utilizing an alternate construction. The cross-sectional area of
the metal-composite interface is altered by positioning the ends of
the linearly tapered cylindrical metal end fittings and sleeves
longitudinally offset from one another. In one formation of the
resulting nesting cavity, the cylindrical wall of the end fitting
extends deeper into the pipe segment interior than the
concentrically surrounding sleeve wall. Thus, a reinforced and
nested metal-composite interface is maintained while providing
enhanced diffusion of stress loads across the joint surfaces and in
turn, providing a supported degree of flexing at the juncture.
[0025] Other features and advantages of the invention will become
apparent from the following detailed description, taken in
conjunction with the accompanying drawings which illustrate, by way
of example, the features of the invention
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a perspective illustration, separated by parts, of
a conventional drill pipe string extended into a well bore;
[0027] FIG. 2 is an exploded perspective illustration, partially in
section, of the metal to composite end fitting assembly embodying
the pipe assembly;
[0028] FIG. 3 is a further perspective illustration of the pipe
assembly incorporating the parts illustrated in FIG. 2;
[0029] FIG. 4 is a sectional view, of a coupled pipe joint
illustrating the signal connection between pipe parts shown in FIG.
2;
[0030] FIG. 5 is an enlarged end view taken along the line 5-5
shown in FIG. 4.
[0031] FIG. 6 is an enlarged end view taken along the line 6-6
shown in FIG. 4.
[0032] FIG. 7 is a side view, enlarged of the circle shown in FIG.
4.
[0033] FIG. 8 is a side view, enlarged of the circle shown in FIG.
4.
[0034] FIG. 9 is a perspective illustration, in partial section, of
the tooling arrangement useful in combining the inventive assembly
into an integral fixture;
[0035] FIG. 10 is a diagrammatic view, in perspective, illustrating
the inventive implementation of a forming facility useful in
forming the composite pipe segment on a rotary mount incorporating
portions of the end fitting assembly;
[0036] FIG. 11 is an enlarged cross sectional end view taken along
the line 11-11 of FIG. 10.
[0037] FIG. 12 is a sequence diagram of an end fitting assembly
sequence in accordance with the present invention;
[0038] FIG. 13 is a perspective exploded illustration, of a second
embodiment of the metal to composite end fitting of the present
invention and showing an electrical contact mechanism bridging
electrical conduction across a threaded pipe joint;
[0039] FIG. 14 is an enlarged sectional detail view of the contact
mechanism shown generally in FIG. 13 before the full threaded
engagement of a pipe joint;
[0040] FIG. 15 is an enlarged sectional detail view of the contact
mechanism shown generally in FIG. 13 after the full threaded
engagement of a pipe joint;
[0041] FIG. 16 is a side cross sectional view of the threaded joint
interface and contact mechanism shown generally in FIG. 13;
[0042] FIG. 17 is a broken longitudinal sectional view of a third
embodiment of the pipe assembly shown in FIG. 3; and
[0043] FIG. 18 is a detailed view in enlarged scale taken from the
circle 18 shown in FIG. 17.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] As shown in FIG. 1 current drilling practices depend on a
string SP composed of drill pipe segments PS connected end-to-end
to turn a cutting tool CT mounted on the lower string end. In the
course of such turning, the tool CT grinds and penetrates through
the bottom of the well bore WB with the particulates continuously
brought out to the surface by a circulating flow of drilling mud DM
pumped into the bore to equalize bore pressures. As readily
available formations are depleted these drilling projects now
extend to much greater depth, and/or greater lateral reach, with
the weight of the pipe string SP and/or its friction load in the
well bore setting the practical exploration limits. The complexity
of a drilling rig RG conformed for such long reach drilling is
enormous and the logistics of its movement alone, encourage
directional capability along with an increasing pipe string. This
same complexity of the rig also determines the manipulation
convenience of each of the pipe segments PS, again resulting in its
own logistic and mechanical constraints resolved by the size of the
rig (or off-shore platform) that can be effectively implemented at
the well site, thereby limiting the length of each segment PS and
multiplying the number of required joints JT that need to be made
to extend the string to the desired depth. The combined weight of
the string, including all the down hole joints and any wear knots
or pipe protectors 90 shielding the pipe from wall contact, along
with the friction load resulting from this wall contact, are thus
resolved at the last surface joint which sets the design limit. It
is within this limit that the rig operator tries to discover oil by
periodic insertion of instruments down the bore, or simply by
inspecting the drilling debris brought to the surface.
[0045] In addition to the above physical concerns there are also
those imposed by various laws and ordinances dealing with the
environment. There is currently substantial public resistance to
the equipment clutter associated with crude oil production
appearing in one's neighborhood, further promoting directional
drilling, a technique that compounds torsional loading as very long
drill pipe strings are turned while resting on the wall of the
well. This same technique also demands shorter radius turns, or a
more flexible pipe, and also accurate instrumentation to inform the
operator of the actual direction that is being drilled and of any
formation details that are encountered. For all these reasons light
weight, high strength, but elastic pipe is desired, particularly if
signal and power conductors can be combined therewith. All these
concerns are now substantially resolved in the inventive structure
and process described by reference to FIGS. 2-18.
[0046] By particular reference to FIGS. 2-4 the inventive pipe
assembly, generally designated by the numeral 10, comprises a
tubular composite pipe segment 11, formed by winding up reinforcing
fiber, such as carbon fiber, preferably wound in stress determined
orientation patterns between plies of interleaved wrapping, all
bonded together by resinous filler to form a cylindrical structure
of a generally uniform wall thickness over most of its length.
[0047] Pipe segment 11 may be formed with a generally uniform taper
along a selected portion of each end 12-1 and 12-2 reducing in wall
thickness. Each end may be defined by interior and exterior wall
surfaces 12i and 12e respectively, that are configured for receipt
within conforming annular cavities formed by male and female
couplers comprising a set of nested metallic end fittings 20-1 and
20-2 and metallic sleeves 30-1 and 30-2. Those skilled in the art
will appreciate that the surfaces of the pipe segment and adjoining
structures for that matter, may use other surface configurations,
yet, in one embodiment, tapered and frustoconical surfaces are used
permitting a diffusion of torsional loads across the surfaces of
connected pieces.
[0048] The metallic end fittings 20-1 and 20-2 include a flange 29
with shoulders 29-1 and 29-2 and skirt 23 including an exterior
surface 22e tapering in reducing cross section away from the
flange.
[0049] The metallic sleeves 30-1 and 30-2 include respective
telescoping flanges 39 and skirts 33 formed with interior surfaces
32i tapering in expanding cross section away from the flange.
[0050] The annular cavities formed by the nested pieces are formed
by axially aligning the tapered exterior surface 22e of skirt 23
adjacent an oppositely tapered surface 32i on the skirt 33
interior. The surfaces 22e and 32i are each closely matched to
respective dimensions and tapered surfaces 12e and 12i where
insertion of the surfaces 12e and 12i into the annular cavity forms
an aligned pipe segment end interface. Those skilled in the art
will appreciate that this self aligning construction creates a
bonding interface that can be effected by any high temperature
epoxy resin and will further appreciate that the close fit of this
bond is further enhanced by close dimensional matching between the
coaxially nested end fitting and sleeve pieces so that the sleeve
forms a peripheral support for the tapered end of the pipe segment
as it is slid into position within the end fitting.
[0051] In addition, each of the skirts 23 and 33, moreover, may
include a radially matched set of lateral openings 24 and 34
dimensioned for press fit or interference receipt of corresponding
optionally used pins 45 that also pass through corresponding
circular openings 15 formed in the tapered ends 12-1 and 12-2 once
the ends are fully received, bonded and indexed within their
receiving cavities. This same indexed alignment may orient the
exposed ends 18 of conductor leads 17 that are woven into the
filament matrix of the pipe segment 11 into alignment with
longitudinal drillings 37 formed in skirts 33 to effect an
electrical connection across the pipe joint herein described.
Beyond this bonding receipt, each of the pieces is formed as a
closely dimensioned telescoping cylindrical segments 26 and 36
which are each provided with corresponding exterior flanges 29 and
39 aligned next to each other when the skirts are properly
positioned. Of course, the same drillings 37 extend through the
flange 39 to convey the lead ends 18 therethrough.
[0052] Those skilled in the art will appreciate that while pieces
20-1 and 20-2, and also pieces 30-1 and 30-2, are described above
by identical descriptions, in application one of the nested end
piece sets serves as the male portion of the threaded joint,
otherwise referred to as the `pin end`, and the other end piece set
serves as the female threaded, or the `box end`. Accordingly, those
parts of the end fitting pieces 20-1 and 20-2 that are exterior of
flanges 29 are of necessity different depending on the joint
function that is formed. Thus end fitting 20-1 includes a threaded
boss 51-1 extending beyond the exterior shoulder 29-1 of the flange
29 that is conformed for threaded receipt in a threaded cavity 51-2
formed in the other exterior shoulder 29-2 of the other flange 29
on the end fitting piece 20-2. Each of the flanges 29, moreover,
includes drilling continuations shown as drillings 27-1 and 27-2
(FIG. 4) aligned with drillings 37, drilling 27-1 conveying the
conductor end 18 into a circular recess 53-1 formed in the flange
shoulder surface 29-1 where the lead is connected to an insulated
ring 54-1 conformed for receipt within the interior of recess
53-1.
[0053] In an exemplary assembly, the overall length of the pipe
assembly 10 measures approximately 359 inches. In this assembly,
the composite pipe 11 measures 338.00 inches long between
respective outer sleeve proximal ends 30-1 and 30-2 and includes an
inner diameter of 1.625 inches and an outer diameter of 2.510
inches intermediate the end assemblies. The diameters expand
outwardly therefrom toward the assembly fittings where the pipe
inner surface 12i and exterior surface 12e respectively are formed
with radial dimensions matching their confrontment with end fitting
exterior surface 22e and sleeve inner surface 32i respectively. The
overall pipe string diameter expands from the composite pipe 11
outer diameter of 2.510 inches to a metallic fitting end diameter
of 3.405 inches. The length of the "pin" end assembly measures
approximately 10.00 inches from the distal end of male boss 51-1 to
the outer sleeve 30-1 proximal end. The "box" end assembly measures
approximately 1.00 inch longer between respective like features of
female boss 51-2 and sleeve end 30-2 to accommodate the male boss
51-1. Thus, it will be appreciated that the metal to composite
conjunction is useful in extended reach applications by providing a
diffusion of loads across the joint interface.
[0054] During operation in extended reach drilling applications, as
pipe strings drill deeper into earth using longer strings, the
greater the weight of the string becomes, thus promoting drag and
inhibiting drilling performance and efficiency. Greater weight
contributes to increasing tensile strength loads under the
increasing pressures of deep extended reach drilling environments
pulling and stretching on the pipe assembly components, and in
particular, tugging on joints where tensile loads can separate
parts. As will be appreciated, the length of the drill string of
the presently described embodiment is approximately 86% composite
material length compared to approximately 14% metallic material
length. The metal is primarily reserved for the end fittings 20 and
sleeves 30 that support the joint interface to the composite pipe
segment 11 and provide strengthened joint coupling between adjacent
pipe assemblies where tensile loads can do significant harm.
Furthermore, to aid in drilling extended distances, it will be
understood that as the composite layers are formed, additional
carbon material may be added to strengthen the tensile load
capacity of drill strings. The composite pipe 11 walls may also be
conveniently adjusted to thicker or thinner thicknesses depending
on the depth of drilling by forming the pipe segments with more or
less composite layers.
[0055] It will be appreciated that the drill string is conducive to
carrying torsional loads by both the internal fitting to composite
wall interface and by the metallic outer sleeve. In operation, as
the drill pipe string turns, force loads are distributed along the
walls of the drill pipe assembly and are diffused over pipe walls
expanding from the intermediate portion toward the joint assembly
interfaces and ends. When loads propagate toward the joint
assemblies, these loads encounter the dual tapered surface
interface between the metallic end fittings 20 and metallic sleeves
30 confronting the composite pipe disposed intermediately
therebetween distributing the loads across two surfaces interfaces.
As torsional forces encounter the first tapered interface between
the metallic end fitting and composite pipe, the tapered surfaces
create a larger area of load confrontment thereby diffusing the
load effects over a greater surface area. Those skilled will
appreciate that this effect is enhanced by a second tapered
interface between the composite pipe and sleeve tapered surfaces
where the loads once again encounter an extended surface area
diffusing the loads a second time as the outer sleeve carries part
of the load. As such, drill assemblies for long reach with the
proposed configuration can be assembled in strings beyond 35,000
feet in length.
[0056] Referring to FIGS. 5-8, end fitting 20-2 includes a drilling
27-2 indexed with drilling 37 in the sleeve 30-2 to convey the
other conductor end 18 into a manifold 56 (FIG. 8) formed in flange
29 and terminating in one or more openings 57 through shoulder
surface 29-2 opposing the recess 53-1 when the ends are threadably
mated. Opening 57, may in turn, be provided with a spring biased
piston 58 carrying a bayonet point 59. Referring to FIG. 5, a
sectional end view of the "pin" end is illustrated showing the
insulated contact ring 54-1 circumscribed within the circular
recess within the flange 29-1. The assembly of circular features in
FIG. 5 are shown in relation to the features of FIG. 6 where the
spring-biased piston and bayonet point on the "box" end in manifold
56 are in circumferential alignment to the ring. Once the bosses
51-1 and 51-2 are joined together, it is then useful to pressurize
the manifold interior, advancing the piston against the spring bias
to drive the bayonet point through the insulation on the opposingly
aligned contact ring. In this manner, one example of circuit
continuity is effected between the conductors 17 imbedded in the
joined segments regardless of their relative orientation.
[0057] Those in the art will further appreciate that the foregoing
arrangements are particularly suited for custom forming of
composite pipe segments 10 by way of the nested end fittings
described herein. By particular reference to FIGS. 9-12, the
fitting end pieces 20-1 and 20-2 may be combined with a forming
mandrel effected by an inner core layer 111 (FIG. 10), to form the
turning core for the subsequent winding of fiber plies 92 and the
remaining interleaved layers 93 forming the composite pipe 11, in
step 201. In this step the winding pitch, fiber density and the
selection of any sealing wraps may also be determined by the
particular parameters of the well and the mandrel structure may be
further stiffened and assisted by internal pressurization while the
fiber wind-up tension is controlled. Of course, conductive leads 17
may be concurrently also imbedded into the wrap, again in
accordance with the type and nature of the signals and/or power
that may be conveyed thereon. Once the structural conditions are
met the end fittings are withdrawn from the core layer and
thereafter nested in the sleeve pieces 30-1 and 30-2 in step 202. A
bonding agent, such as a high temperature epoxy resin is then
applied to the pipe ends 12-1 and 12-2 and the ends are then
re-positioned into the interiors of sleeve pieces 30-1 and 30-2
with the end fitting pieces 20-1 and 20-2 then pressed into their
common interiors, shown as the self-centralizing step 203. In the
course of this same step the exposed conductor ends 18 are conveyed
into their appropriate drillings to be thereafter connected either
to the bayonet contact 59 or the contact ring 54-1. In step 204 the
foregoing assembly is then brought into a spray cooled welding
fixture illustrated in FIG. 9 in which a weld 91 is applied by a
welding device 151 to join the exterior flanges of the nested
pieces 20-1 and 30-1 to each other (and by the same example also
the nested pieces 20-2 and 30-2) while water spray heads 152 and
153 cool the adjacent structure. Optionally, once fixed by their
flanges, the sleeve and end pieces, with the ends 12-1 and 12-2
captured therebetween, are then drilled, in step 205, with
perforations 34 which thereafter receive press fit pins 45.
[0058] In this manner a self-centralized end arrangement is useful
both in the manufacturing and also in effecting a closely held bond
interface between the high strength metal end pieces and the
composite pipe segment with the interface further stabilized and
fixed by welding and press fit pins. Simultaneously, this manner of
manufacture also provides a durable, convenient and effective
manner of incorporating a conductor into the pipe fully protected
by the pipe pieces. The resulting high strength joint is then
further complemented by the appropriately selected wind-up pitch,
weave density and interleaving that are selected for the particular
task. Thus, the fabrication and the ending structure are rendered
both highly effective and convenient.
[0059] It will also be appreciated that the aforedescribed drill
pipe string may be improved upon to include enhanced configurations
for effecting an electrical connection along the pipe string and
modifications to the composite-metal interface providing a durable
yet flexible structure conducive to short radius drilling.
[0060] By reference to FIGS. 13-16, a second preferred embodiment
employs the interior and exterior distantly converging tapered
surfaces at the opposite extremities of the composite segments 11
and showing an alternative contact implementation is obtained by
embedding coaxial contact rings in each of the opposing shoulder
surfaces 29-1 and 29-2 surrounding both the `pin` end and the `box`
end of the joint assembly. As will be appreciated by those skilled
in the art, one or the other or both of the tapers may be in the
form of continuous smooth surfaces as shown in FIGS. 2 and 16 or in
some instances in the form of stepped surfaces cooperating to
progressively narrow the thickness of the segment wall in the
distal direction. Once again, like numbered parts functioning in a
manner like that previously described are utilized except that
shoulder surfaces 29-1 and 29-2 are each provided with an annular
groove 53-1 and 53-2 of a sectional dimension conformed to receive
a corresponding elastomeric annular seal 255-1 and 255-2. Seal
255-1 is generally shaped as a U sectioned structure defined by
concentric inner and outer annular walls 256i and 256o extending
from a bottom wall 257. A conforming contact ring 261 chamfered
along its upper edges by a peripheral chamfer 261e is then captured
by elastic stretching within the annular cavity 256 formed between
the inner and outer sealing walls 256i and 256o of the seal 255-1
with the outer wall stretching just over the chamfer to retain the
ring in position. A similarly dimensioned contact ring 262 is then
received in the annular cavity 258 formed between the inner and
outer walls 258i and 258o of the `box` end seal 255-2, with the
groove depth (or wall height) of walls 258i and 258o being
substantially greater than the thickness of the ring and the depth
of the receiving recess 53-2. The height of seal 255-1, in turn, is
somewhat less than its receiving recess 53-1. Preferably, both the
contact rings are inserted within their respective seals so that
each contact surface projects just slightly above the corresponding
surface 29-1 and 29-2, a projection determined by the dimensions of
the annular recesses or grooves 53-1 and 53-2 and the dimensions of
each seal. Of course, walls 258i and 258o each project beyond the
corresponding surface of ring 262 before the threaded engagement of
the joint, as illustrated in FIG. 14.
[0061] In this projecting deployment both the opposing seals and
the rings seated therein are fixed in rotation in each
corresponding recess 53-1 and 53-2 by way of spaced axial pins 263
and 264 that project from the buried edges of each of the rings 261
and 262 into conforming pockets 259 in each of the seal bottoms
which are then inserted into conforming cavities 269 formed in the
abutment surface bottoms of each of the recesses 53-1 and 53-2
(FIG. 13). The projecting seal edges and the rings therein
therefore slide in rotation relative each other as the pipe joint
is made. As illustrated in FIG. 15, once the joint is made, the
excess volume of the elastomeric matter forming each of the seal
walls 258i and 258o fills the volume of the edge chamfers 261e
which also assist in the spreading of the seat edges to facilitate
a direct contact between the rings as illustrated before the mating
in FIG. 14. Thus the edge chamfers in ring 261 allow for the
elastomeric material flow of the seal material as the joint is
threaded together, ensuring a completely surrounding sealing
closure as the exposed edges of the rings are pressed against each
other while the smaller contact dimension formed between the edge
chamfers 261e assures a better ring contact while also
accommodating a somewhat less precise axial registration between
the pipe segments. This same material flow may be utilized to both
seal and capture the exterior insulation 275e around a conductor
275 extending through corresponding drillings 271-1 and 271-2
through corresponding shoulders 38-1 and 38-2 and extending into
one of the cavities 269 in the bottoms of recesses 53-1 and 53-2 to
pass the respective lead ends 275 through the seal material and
thereafter into perforations 261p and 262p in the corresponding
rings 261 and 262. Referring to FIG. 16, a return conductor 285
connected directly between the pipe segment ends can then be
utilized to provide the return or common ground. Thus, when
environmental resistance is encountered at certain depths, the load
carrying capacities of the drill string sections can be adjusted
accordingly. In this manner, a rugged and reliable contact is
effected, thus accommodating both the power and the signal needs in
deep well drilling.
[0062] In operation, threaded assemblies may not result in the same
two polar points aligning functionally. It may occur that a point
on a threaded end does not meet a corresponding point on a
receiving end more than once because the boss end may begin at a
different point for threading or the degree of torque applied at
the end of the threading shifts the points. Those skilled in the
art will appreciate that by utilizing contact rings at the end
fittings of a threaded pipe assembly, an effective and efficient
means for conduction of a signal is maintained even where the
conductors are not in direct contact or alignment to one another.
It will be seen that the contact rings 262 and 261 will be in
conductive engagement regardless of where the conductor 275 is
situated on one end piece after threading relative to where the
next conductor 275 is on an adjacent segment. Thus, as long as the
contact rings are engaged and the conductors are in conductive
proximity to the axial pins 263 of their respective contact ring
and insulated from electrical diffusion from one another and the
surrounding conductive elements, signal can be successfully
transmitted from one conductor through the contact ring conjunction
to the next conductor.
[0063] It will also be appreciated that by using annular seals 255
to incorporate the contact rings 261 and 262, an efficient means of
maintaining the conductive integrity is preserved. The annular seal
assists in protecting the contact ring from the conductive
properties and stress imposed by the metal walls of the pipe end
fittings. By sheathing the conductor in an insulation 275e in
conjunction with housing the contact rings in the annular seals,
signal loss may be prevented from escaping to the pipe exterior.
Once the two pipe ends are press fit, further insulation is
achieved where the elastomeric flow fills the annular voids within
the shoulders 29 of the two ends. By insulating the conductive
components of the contact rings from other conductive components, a
signal can be transmitted down a line without short. Additionally,
as the pipe assembly advances through jagged rock surfaces
contacting the drill pipe outer walls, it will be further
appreciated that embedding the conductor 275 into the composite
pipe segment walls and subsequently into the sleeves 30 and end
fittings 20 protects the conductor from frictional contact with the
surrounding environment.
[0064] It will be further appreciated that each of the conductors
{17; 275} may be variously effected either as an electrical power
lead, a signal lead or even a fiber optic filament. Of course,
known techniques of signal superposition, frequency and/or pulse
modulation or other signaling formats can then be effected by these
leads to bring out down hole information directly to the rig
operator as the drilling is taking place which can then be used to
modify, in known techniques, the drilling direction and the cutting
rate, commonly referred to as LWD or `logging while drilling` and
MWD or `measuring while drilling.` In this manner, all the control
and pipe compliance conditions can be conveniently accommodated in
a pipe string that, because of its light weight, is particularly
suited for ultra deep and/or extended reach drilling.
[0065] In a third preferred embodiment, it will be understood that
for short radius drilling applications such as from offshore oil
platforms where the drilling direction is rapidly changed to avoid
obstructions or based on a feedback signal, the nested pieces and
their respective tapered surfaces may be modified to withstand
varying external loads on the pipe joints accommodating flexing
during drilling while maintaining a metal-composite interface
conducive for carrying a torsional load capacity. For example, the
drill string configuration in FIGS. 17 and 18 is similar to the
drill string embodiment shown in FIGS. 2-4, except that the
longitudinal length of the metal end fitting 320 is concentric with
and projects approximately 1 inch farther of the end of the outer
sleeve 330 facilitating flexure at the metal-composite junction.
Similar to the embodiment shown in FIGS. 2-4, end fittings 320-1
and 330-1 respectively also include tapered wall surfaces 332i and
322e projecting divergently away from the end fittings to form a
conical nesting cavity with and for bonded receipt of tapered
surfaces 312i and 312e of pipe segment ends 312-1. Additionally,
those skilled will recognize that the composite pipe segment 311
can be constructed to include less carbon material providing more
flexibility in the composite segment length. Thus, it will be
appreciated that the pipe assembly 300 is conducive for providing
quick turns while maintaining durable integrity during advancement
of drilling.
[0066] In operation, as the drill assembly 300 rotates advancing
toward an oil trap, the composite walls and offset metallic end
portions provide a flexure point at the metal-composite interface
facilitating directional change during short radius turns. Those
skilled will recognize that the composite pipe walls are relatively
more flexible than the metal end fittings. Thus, upon a relatively
rapid change in drilling direction, the composite walls will bend
in the direction of the turn and the internal metallic fitting end
bends with the composite walls. The external metallic sleeve end,
in turn, provides a flex point for the internal metal end fitting
and composite wall to bend from while simultaneously supporting the
metal-composite joint interface to partially carry torsional loads.
As portions of the string advance past short radius turns, the
bending loads on the composite walls lessen and the more rigid
metal end fitting helps draw the composite walls back to a linear
state. Similar to the embodiment shown in FIGS. 2-4, as loads
propagate down the drill string and encounter the
metallic-composite joint interface, torsional loads once again
encounter two extended cross-sectional areas between the metal and
composite surfaces and thus, diffuse the loads at the two
interfaces. Thus, an appreciable degree of flexibility may be
achieved during short radius drilling while providing a durable
structure that can return to is rigidity as the pipe string is
extracted from its hole.
[0067] It will also be recognized that the drilling experience is
further enhanced by incorporating the conductor 275 to the pipe
assembly 300 without detracting from the efficiency of or
compromising the integrity of the assembly structure. As a string
travels deeper into earth and the loads continue to mount on the
string structure, it will be appreciated that measuring signals
sent along the string via the conductor 275 can provide feedback
for adjusting rotational speed as well as update the composition of
surrounding geological attributes relative to oil proximity. The
flexibility of the conductor cooperates with the advancement of the
pipe assembly 300, particularly in short radius applications where
the conductor can flex right along with the pipe segment during
tight turns.
[0068] By using a composite material for the pipe in combination
with metal end fittings, a lighter and cost-effective solution is
demonstrated for deep well drilling. Furthermore, those skilled in
the art will appreciate that assembling a drilling pipe with offset
metal component ends provides for competitive structural integrity
and flexing during small radius turning. By proposing a conductor
imbedded in the pipe walls and the end to end mating with the
exemplary connections shown, a protected and uninterrupted signal
may be sent down the length of the pipe and a return signal
monitored providing data for necessary adjustments during
drilling.
* * * * *