U.S. patent number 3,825,078 [Application Number 05/350,459] was granted by the patent office on 1974-07-23 for method of mounting and maintaining electric conductor in a drill string.
This patent grant is currently assigned to Esso Production Research Company. Invention is credited to Joe K. Heilhecker, Karl O. Heintz, Donald B. Wood.
United States Patent |
3,825,078 |
Heilhecker , et al. |
July 23, 1974 |
METHOD OF MOUNTING AND MAINTAINING ELECTRIC CONDUCTOR IN A DRILL
STRING
Abstract
An insulated electric conductor employed in a tubular drill
string to transmit electric energy between subsurface and surface
locations is arranged within the drill string in a wound, helical,
coiled, looped, folded, overlapped or other convoluted
configuration. Preferably, the convoluted conductor, or a portion
thereof, is maintained in tension. The convoluted configuration
provides an excess length of conductor stored within the drill
string which enables the conductor to be extended as the drill
string is lengthened.
Inventors: |
Heilhecker; Joe K. (Houston,
TX), Wood; Donald B. (Houston, TX), Heintz; Karl O.
(Houston, TX) |
Assignee: |
Esso Production Research
Company (Houston, TX)
|
Family
ID: |
27401995 |
Appl.
No.: |
05/350,459 |
Filed: |
April 12, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
267729 |
Jun 29, 1972 |
|
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Current U.S.
Class: |
175/57; 166/385;
175/104; 166/66; 175/4 |
Current CPC
Class: |
E21B
23/14 (20130101); E21B 19/22 (20130101); E21B
19/00 (20130101); E21B 17/003 (20130101) |
Current International
Class: |
E21B
17/00 (20060101); E21B 19/22 (20060101); E21B
23/14 (20060101); E21B 19/00 (20060101); E21B
23/00 (20060101); E21b 007/00 (); E21b
047/12 () |
Field of
Search: |
;339/16 ;174/47
;166/315,65,65M ;175/40,50,104,57 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Brown; David H.
Attorney, Agent or Firm: Graham; Robert L.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of application Ser. No.
267,729, now abandoned filed in the U.S. Pat. Office on June 29,
1972.
Claims
We claim:
1. In a method of drilling a well wherein an insulated electric
conductor is employed in a drill string to transmit electric energy
between a subsurface location in said drill string and a location
substantially at the surface, the improvement which comprises
placing said conductor in said drill string in a configuration such
that the total length of said conductor is substantially longer
than the distance between said subsurface and surface locations;
adding a length of pipe to said drill string to increase the
distance between said subsurface and surface locations; and
threading said conductor through said length of pipe.
2. In a well drilling operation wherein an insulated electric
conductor is employed internally of a pipe string to transmit
electric energy between a subsurface location and a location
substantially at the surface, an improved method for extending said
electric conductor through lengths of pipe which are individually
added to said pipe string as the drilling progresses which
comprises storing a length of conductor within said pipe string
which is in excess of the distance between said locations;
extending a portion of said electric conductor through a length of
pipe to be added into said pipe string; connecting said length of
pipe into said pipe string.
3. A method as defined in claim 2 wherein the step of storing a
length of conductor in the pipe string provides an excess length of
conductor at least equal to said length of pipe to be added into
said pipe string.
4. A method of installing an insulated electric conductor in a
tubular drill string in a well which comprises placing said
conductor internally of said drill string; arranging said conductor
to form overlapped portions having an upper loop and a lower loop
within said drill string; and introducing additional conductor into
said drill string while lowering said lower loop within said drill
string to lengthen the overlapped portions.
5. A method as defined in claim 4 and further comprising biasing
said upper loop and said lower loop apart to remove slack in said
conductor.
6. In a method of drilling a well wherein an insulated electric
conductor is employed in a pipe string to transmit electric energy
between subsurface and surface locations in said pipe string, the
improvement which comprises placing said conductor in said pipe
string in a configuration such that the length of said conductor is
substantially longer than the distance between said subsurface and
surface locations; and extending said conductor through individual
lengths of pipe as each of said lengths is added to said pipe
string.
7. A method as defined in claim 6 wherein the step of extending
said conductor through individual lengths of pipe is performed
after each of said lengths of pipe is added into said pipe
string.
8. A method as defined in claim 6 wherein the step of extending
said conductor through individual lengths of pipe is performed
before each of said lengths of pipe is added to said pipe
string.
9. A method as defined in claim 6 wherein the configuration of said
conductor is convoluted.
10. A method as defined in claim 6 wherein the step of extending
said conductor includes withdrawing a portion of said conductor
from said pipe string and threading said portion through each
length of pipe as said length of pipe is added to said pipe
string.
11. A method as defined in claim 6 wherein said conductor is placed
in said pipe string in a configuration such as to provide
overlapped portions having an upper loop and a lower loop.
12. A method as defined in claim 11 wherein the lower loop is
biased downwardly to remove slack from a portion at least of said
conductor.
13. A method of establishing and maintaining electric continuity
between a subsurface location and surface location in a pipe string
used to drill a well which comprises placing an electric conductor
in said pipe string which extends between said subsurface and
surface locations and which has a length substantially in excess of
the distance between said subsurface and surface locations;
advancing said well sufficiently to require lengthening said pipe
string; adding a length of pipe into said pipe string; and
extending a portion of said electric conductor through said length
of pipe.
14. A method of establishing electric continuity within a pipe
string in a well between a subsurface location and a location
substantially at the surface which comprises placing an insulated
electric conductor in said pipe string to extend from said
subsurface location to said surface location; convoluting at least
a portion of said conductor within said pipe string such that the
length of said conductor in said pipe string exceeds the distance
between said subsurface and surface locations; and tensioning at
least a portion of said conductor to reduce slack in said
conductor.
15. In a method of drilling a well using a pipe string wherein the
pipe string is lengthened as the well becomes deeper by
disconnecting the pipe string at the surface and adding a length of
pipe into the pipe string by connecting said length of pipe at each
end to the pipe string, the method of providing electric continuity
between a subsurface location in the pipe string and a location
substantially at the surface of the well, which comprises placing
an insulated electric conductor in the well within the pipe string
to extend from said subsurface location near the lower end of said
pipe string to said surface location, said conductor having a
length substantially in excess of the distance between said
subsurface and surface locations; breaking said electric continuity
by separating said conductor substantially at the surface when the
addition of said length of pipe is to be made into the pipe string;
and reconnecting said electric conductor before both ends of the
additional length of pipe are connected into said pipe string to
include a length of electric conductor extending through said
additional length of pipe.
16. A method as defined in claim 15 which includes the step of
removing slack from at least a portion of the conductor in the pipe
string.
17. A method as defined in claim 15 in which a portion of the
conductor in the pipe string is withdrawn therefrom after the
conductor is separated and is extended through said additional
length of pipe.
18. A method as defined in claim 15 in which at least a portion of
the electric conductor lowered within the pipe string is convoluted
such that the length of said conductor between said subsurface and
surface locations exceeds the distance between said locations.
19. A method as defined in claim 18 wherein said convoluted
conductor includes overlapped portions having an upper loop and a
lower loop.
20. A method as defined in claim 19 and further comprising biasing
said upper and lower loops apart.
21. A method as defined in claim 19 wherein said upper loop is
supported on said pipe string and said lower loop is biased
downwardly.
22. In a method of drilling a well using a pipe string, an improved
method of establishing and maintaining electric continuity through
said pipe string between a subsurface location in the well and a
surface location which comprises lowering in said pipe string an
insulated electric conductor to extend between said locations and
having a substantially length in excess of the distance between
said locations; advancing said well sufficiently to require the
insertion of an additional length of pipe into said pipe string;
disconnecting said pipe string and separating said electric
conductor at the surface; threading electric conductor through an
additional length of pipe; reconnecting said electric conductor to
reestablish electric continuity between said locations through said
pipe string including said additional length of pipe; and inserting
said additional length of pipe into said pipe string.
23. A method of establishing and maintaining electric continuity in
a drill string in a well as said well is being drilled which
comprises lowering an insulated electric conductor in said drill
string to extend from a subsurface location near the lower end of
said drill string substantially to the surface; convoluting a
portion of said conductor such that the length of conductor in said
drill string is in excess of the distance between said subsurface
location and the surface; threading an electric conductor section
through a length of pipe to be added to said drill string;
connecting said conductor section to said electric conductor; and
connecting said length of pipe to said drill string.
24. A method for establishing and maintaining electric continuity
between a subsurface terminal within a pipe string used to drill a
well and a surface terminal which comprises placing an insulated
electric conductor in said pipe string to extend between said
terminals and which has a length substantially in excess of the
distance between said terminals; advancing said well sufficiently
to require an additional length of pipe in said pipe string;
disconnecting said pipe string at a point near the surface;
withdrawing a conductor section from said pipe string; separating
said conductor section from the remainder of said conductor;
threading said conductor section through a length of pipe;
reconnecting said conductor section to the remainder of said
conductor; and connecting said length of pipe into said pipe
string.
25. A method of electrically connecting a first electric terminal
located within a pipe string at a subsurface location in a well
with a second electric terminal located near the surface of the
well which comprises lowering within the pipe string an electric
conductor which is longer than the distance between the terminals;
securing the lower end of said conductor at said subsurface
location in electrical connection with said first electric
terminal; locating the upper end of said conductor at said surface
location in electrical connection with said second electric
terminal; and convoluting and tensioning at least a portion of said
electric conductor between said terminals so as to remove slack in
said electric conductor.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an improved method for establishing and
maintaining electric continuity through a drill string using an
insulated electric conductor. The invention can be employed in
wellbore telemetry operations and other operations wherein it is
desired to transmit electric energy between the surface and a
subsurface location in a well.
2. Description of the Prior Art
In the drilling of oil wells, gas wells, and similar boreholes, it
frequently is desirable to transmit electric energy between
subsurface and surface locations. One application where electrical
transmission has received considerable attention in recent years is
found in wellbore telemetry systems designed to sense, transmit,
and receive information indicative of a subsurface condition. This
operation has become known in the art as "logging while drilling."
A major problem associated with wellbore telemetry systems proposed
in the past has been that of providing reliable means for
transmitting an electric signal between the subsurface and surface
locations. This problem can best be appreciated by considering the
manner in which rotary drilling operations are normally performed.
In rotary drilling, a borehole is advanced by rotating a drill
string provided with a bit. Lengths of drill pipe, usually about 30
feet long, are individually added to the drill string as the
borehole is advanced. In adapting an electrical telemetry system to
rotary drilling equipment, it will thus be appreciated that the
means for transmitting an electric signal between subsurface and
surface locations must be such as to permit the connection of
additional pipe lengths to the drill string. An early approach to
the problem involved the use of a continuous electrical cable which
was adapted to be lowered inside the drill string and to make
contact with a subsurface terminal. This technique, however,
required withdrawing the cable each time an additional length was
connected to the drill string. A more recent approach involves the
use of special drill pipe equipped with an electric conductor. Each
pipe section is provided with connectors that mate with connectors
of an adjacent pipe section and thereby provide an electrical
circuit across the joint (See U.S. Pat. Nos. 3,518,608 and
3,518,609). Disadvantages of this system include the high cost of
special pipe sections, the use of a large number of electric
connectors (one at each joint), and the difficulty of maintaining
insulation of the electric connectors at each joint.
Although the advantages and desirability of telemetering
information from a subsurface location to the surface as drilling
operations progress have long been appreciated, electrical
telemetry systems have not proven successful mainly because of the
unavailability of a reliable and practical conductor for
transmitting electric signals to the surface.
SUMMARY OF THE INVENTION
The method of the present invention is adapted for use in a well
drilling operation wherein an insulated electric conductor disposed
in a pipe string used to drill a well is employed to transmit
electric energy between a subsurface location within the pipe
string and the surface.
A novel feature of the invention resides in placing the electric
conductor in the pipe string in a configuration such that the
length of the conductor is substantially longer than the distance
between the subsurface and surface locations. This configuration
provides an excess length of conductor stored within the drill
string. As each additional length of pipe is connected into the
pipe string, thereby increasing the distance between the subsurface
and surface locations, the conductor can be extended through the
additional length of pipe by withdrawing a portion of the excess
length of conductor from within the pipe string and threading it
through the additional length of pipe.
Although the conductor can be arranged within the pipe string in a
variety of convoluted configurations to provide the excess length,
the preferred configuration is such that the conductor has
overlapped longitudinal portions which preferably are disposed in
parallel relation and extend axially with respect to the pipe
string.
Another novel aspect of the present invention involves a method of
lengthening a pipe string and electric conductor within the pipe
string as drilling progresses. Briefly, the method involves
disconnecting both the pipe string and electric conductor at the
surface, threading a conductor section through the additional
length of pipe, and finally connecting the conductor section and
length of pipe to the electric conductor and pipe string,
respectively.
Still another novel feature of the invention resides in maintaining
an electric conductor or at least a portion thereof within the pipe
string in tension during drilling operations to remove or reduce
slack in the conductor.
The method of the present invention permits the use of a continuous
conductor from the subsurface location substantially to the
surface. In the preferred embodiment, only one connector, located
near the surface, is exposed to the drilling fluid. Moreover, the
method can be employed in rotary drilling operations using
conventional drill pipe.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of well drilling equipment provided with
an electric conductor arranged within the pipe string in a
preferred configuration.
FIG. 2 is a fragmentary view of FIG. 1 illustrating the disposition
of the electric conductor at a time subsequent to that illustrated
in FIG. 1.
FIGS. 3-6 are schematic views illustrating a preferred sequence of
steps for adding a length of pipe into the pipe string.
FIG. 7 is an enlarged fragmentary view, shown partially in
longitudinal section, of an improved apparatus useful in the
present invention.
FIG. 8 is a top plan view of the upper guide of the assembly
illustrated in FIG. 7.
FIG. 9 is a top plan view of the lower guide of the assembly
illustrated in FIG. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Conventional rotary drilling equipment, as schematically
illustrated in FIG. 1, includes swivel 10, kelly 11, tubular drill
string 12, and bit 13. These components, connected in the manner
illustrated, are suspended from the drilling derrick 14 by means of
rig hoisting equipment. The kelly 11 passes through rotary table 16
and connects to the upper end of the drill string 12. The term
"drill string" as used herein refers to the column of pipe 12
between the bit 13 and the kelly 11, and the term "pipe string"
refers to the complete column of pipe including kelly 11. The major
portion of the drill string 12 normally is composed of drill pipe
with a lower portion being composed of drill collars. The drill
string 12 consists of individual pipe sections connected together
in end-to-end relation. In the lower three sections of FIG. 1, the
diameters of the borehole and the drill string 12 have been
expanded in relation to the upper section to reveal further
details.
The borehole 17 is advanced by rotating the drill string 12 and bit
13 while at the same time drilling fluid is pumped through the
drill string 12 and up the borehole annulus. The drilling fluid is
delivered to swivel 10 through a hose attached to connection 18 and
is returned to the surface fluid system through pipe 19. A kelly
bushing 20 couples the rotary table 16 to the kelly 11 and provides
means for transmitting power from the rotary table 16 to the drill
string 12 and bit 13. (The use of a power swivel eliminates the
need for the kelly and rotary table. The present invention can be
used with either system; for purposes of illustration, however, the
invention will be described with reference to the kelly and rotary
table system.)
As mentioned previously, it frequently is desirable to monitor a
subsurface drilling condition during drilling operations. This
requires measuring a physical condition at the subsurface location,
transmitting this data as an electrical signal to the surface, and
reducing the signal to useful form. Typical situations where
telemetry is applicable in drilling operations include drilling
through abnormal pressure zones, drilling through zones where hole
deviation is likely to be a problem, directional drilling,
exploratory drilling, and the like.
Although the present invention may be employed in most any drilling
operation wherein an electric conductor is used in pipe string to
transmit electric energy between a subsurface location and a
surface location, it finds particularly advantageous application in
a wellbore telemetry system such as that illustrated in FIG. 1
comprising an instrument 21, an insulated electric conductor 22,
and receiver 23.
The instrument 21 capable of measuring a subsurface condition and
generating an electric signal indicative or representative of that
condition is provided within the drill string 12. A variety of
devices capable of sensing a physical condition are available.
These include transducers for measuring pressure, temperature,
strain and the like; surveying instruments for measuring hole
deviation; and logging instruments for measuring resistivity or
other properties of subsurface formations. The instrument 21 may be
powered by batteries or by energy transmitted through conductor 22.
Alternatively, a subsurface generator driven by fluid flowing
through the drill string 12 may be used to power instrument 21.
The method of the present invention relates primarily to the
electric conductor 22 employed within the drill string to transmit
electric energy between surface and subsurface locations. The
energy may be a signal generated by the subsurface instrument 21
and transmitted to the receiver 23 at the surface. Alternatively,
the energy may be electric power transmitted from the surface to
actuate or drive a subsurface instrument or motor. Or, energy may
be transmitted down the conductor 22 to power the instrument 21,
and simultaneously intelligence may be transmitted up the same
conductor.
As applied in telemetry operations, it is preferred that the energy
being transmitted be in the form of a pulsating signal. Information
can be transmitted by varying the number, amplitude, width or
spacing of a train of electrical pulses, or it can be transmitted
by modulating the frequency or amplitude of the pulsating signal.
More than one transducer or other device may be employed in the
instrument 21 if desired, in which case a multiplexer may be used
for sending the various signals over a single conductor.
The instrument 21 may be mounted directly in the drill string 12
or, as illustrated in FIG. 1, it may be a separate tool that is
lowered into the drill string 12 on the conductor 22.
The conductor 22 extends from a terminal on the subsurface
instrument 21 substantially through the drill string 12, and
connects to a suitable surface terminal which is electrically
connected to receiver 23. In this preferred embodiment the
conductor extends through the kelly and connects to a terminal at
device 25 located at the upper end of the kelly 11. Kelly conductor
24 serves to interconnect conductor 22 and device 25. It should be
observed, however, that conductor 24 may be embedded in the kelly
11, in which case the conductor 22 will extend to the upper end of
the drill string 12 and connect to conductor 24 at that location.
In order to facilitate the addition of pipe sections to the drill
string 12, however, it is preferred that conductor 24 be disposed
within kelly 11 as illustrated and extend slightly more than the
length of one pipe section below the kelly 11.
If telemetry operations are to be performed while the kelly 11 and
drill string 12 are rotating, the upper end of conductor 24 will be
connected to device 25 capable of transmitting electric energy from
a rotating member to a stationary member. Device 25 may be a rotary
transformer having a rotor secured to the kelly 11 and a stator
secured to the stationary portion of the swivel 10, or it may be a
slip ring and brush assembly. Device 25 and electric conductor 38
provides means for transmitting signals from the conductor within
the pipe string to receiver 23. The return path for the electric
circuit may be provided by a variety of grounding circuits but
preferably is through the pipe string or conductor armor. Conductor
39 of the return path interconnects stationary portion of device 35
and receiver 23. If telemetry operations are to be performed at
times when the drill string 12 and kelly 11 are stationary, the
conductors 38 and 39 may be connected directly to conductor 24
through a suitable connector. In this situation, conductors 38 and
39 will be disconnected when the kelly 11 and drill string 12 are
rotated. Other means for transmitting the signal to the receiver 23
include a wireless transmitter connected to conductor 22 and
located on a rotating member, e.g. kelly 11.
The receiver 23 is an instrument capable of receiving the signal
generated by instrument 21 and reducing it to useful form.
In accordance with one aspect of the present invention, the
conductor 22 is arranged within the drill string 12 in a
configuration such that the length of the conductor 22 is
substantially longer than the distance between the subsurface
location of instrument 21 and a surface location. As described in
detail below, the excess length of conductor 22 stored in the drill
string 12 permits the conductor 22 to be extended as the drill
string 12 is lengthened. A portion of the conductor 22 is arranged
in a wound, coiled, helical, folded, looped or other convoluted
configuration that provides the excess length. It is preferred,
however, that the conductor 22 be arranged in an overlapped
configuration such as that illustrated in FIGS. 1 and 7. This
configuration provides the conductor 22 with longitudinal portions
26, 27, and 28 which are disposed in parallel relation and extend
axially with respect to the drill string 12. The overlapped
configuration permits the excess length of conductor to be almost
double the distance between the subsurface location of the
instrument 21 and the surface.
The apparatus for installing and maintaining the conductor 22 in
the overlapped configuration comprises an upper guide 29 secured to
the drill string 12, and a lower movable guide 30. In the installed
position, the conductor 22 extends upwardly from the instrument 21,
around the upper guide 29, downwardly from the upper guide 29,
around the lower guide 30 and upwardly from the lower guide 30 to
the upper end of the drill string where it connects to conductor
24. The guides 29 and 30 are shown schematically in FIG. 1 and in
detail in FIGS. 7-9.
As best seen in FIG. 4, conductor 24 has a lower tail section 33
which extends slightly more than the length of one pipe section
below kelly 11. The lower end of tail section 33 is provided with
connector 32 which is adapted to mate with connector 31 attached to
the upper end of conductor 22. The conductor 22 is thus joined to
conductor 24 at a point slightly below the top pipe section 34 of
the drill string 12 (see FIG. 3). The electric conductor thus
extends from a terminal on instrument 21 to a surface terminal
within kelly 11 and comprises conductor 22 and conductor 24
connected together by connectors 31 and 32.
The connectors 31 and 32, in addition to providing a water tight
connection, should have sufficient mechanical strength to support
the conductor 22 and associated subsurface equipment. For example,
this connection may be provided by a threaded housing or it may be
provided by an assembly which includes latching dogs to impart
sufficient mechanical strength to the connectors.
As mentioned previously, the excess conductor, e.g. overlapped
portions 27 and 28, permit the conductor 22 to be extended as the
drill string 12 is lengthened. The drill string 12 is normally
composed of individual pipe sections approximately 30 feet in
length. A length of pipe will be added to the drill string 12 for
each incremental advance of the borehole 17. Normally the
additional length of pipe is one pipe section. However, the
additional length may include two or more pipe sections connected
together. In any event, the borehole advancement is sufficient to
permit the addition of a length of pipe. Each additional length of
pipe, one pipe section in this example, may be connected into the
pipe string by the procedure described below with reference to
FIGS. 3 and 6. The procedure for installing the equipment as
depicted in FIG. 3 will be described later.
As shown in FIG. 3 drilling has progressed to the point that one
additional pipe section, e.g. section 36, must be added into the
pipe string 12. Pipe section 36 is disposed in a shallow borehole
37 (commonly referred to as a "mouse hole") below the derrick
floor. Initially, the kelly 11 and drill string 12 are elevated and
the drill string 12 is suspended in the rotary table 16. The kelly
11 is then disconnected from the drill string 12 and is elevated
sufficiently to pull the tail section 33 of kelly conductor 24
completely out of the drill string 12. Thus the kelly 11 is
elevated slightly more than the length of one pipe section. As the
kelly 11 is elevated, the mated connectors 31 and 32 and a portion
of conductor 22 are pulled through the top pipe section 34 of the
drill string 12. This also pulls the lower guide 30 up the drill
string 12 a distance about equal to one-half the length of pipe
section 34 and shortens the overlapped portions 27 and 28 of
conductor 22. With a slotted support plate 35 positioned between
connector 31 and pipe section 34 to support the upper end of
conductor 22, connector 32 is separated from connector 31 breaking
electric continuity and placing the equipment in the condition
illustrated in FIG. 4.
The kelly 11 is then swung over into alignment with the pipe
section 36. The tail section 33 of conductor 24 is threaded through
the pipe section 36 and the kelly 11 is joined to the upper end of
pipe section 36 (see FIG. 5). The kelly 11 and pipe section 36 are
then raised and aligned with the drill string 12. The tail portion
33 extends a short distance, e.g. 1-3 feet, below pipe section 36
permitting the connector 32 to be mated with connector 31
reestablishing electric continuity from the subsurface terminal at
instrument 21 to the surface terminal at device 25. With the
connectors 31 and 32 mated, the support plate 35 is removed. The
lower guide 30 draws the connectors 31 and 32 a short distance
downwardly into the drill string 12. If internal upset drill pipe
is used, the tail portion 33 preferably should be sufficiently long
to permit the connectors 31 and 32 to move downwardly within the
drill string 12 to clear the upset restriction at the pipe
joint.
The lower end of pipe section 36 is then connected to the drill
string 12 (see FIG. 6). Section 36 thus is inserted or added into
the pipe string by connecting one end to the drill string 12 and
the other end to kelly 11. The kelly 11 and drill string 12 are
then lowered until the kelly bushing 20 engages the rotary table
16. Drilling will then continue until another pipe section must be
added. The upper end of conductor 22 is threaded upwardly through
the additional pipe section 36, and another pipe section is added
into the pipe string by the procedure described above and depicted
in FIGS. 3-6. This operation may continue until the excess length
of conductor 22 is used up. This occurs when the lower guide 30
engages or approaches upper guide 29 (see FIG. 2). The conductor
22, guides 29 and 30 and instrument 21 are then withdrawn from the
drill string 12. It should be observed, however, that the excess
length of conductor can be restored within the drill string 12
after it has been completely or partially used up. This may be
achieved by merely connecting a conductor of the desired length to
the upper terminal end 31 of conductor 22 and introducing an
additional length of conductor into the drill string 12. The lower
guide 30 is thus lowered within the drill string 12, increasing the
lengths of overlapped portions 27 and 28. The amount of conductor
that can be added in this manner can be about equal to the amount
of excess conductor used up.
Details of preferred construction of guides 29 and 30 are shown in
FIGS. 7-9. The upper guide 29 comprises a generally cylindrical
body 41, a semicircular member 42 secured to body 41, and a
plurality of arms 43 pivotally mounted on the body 41. Formed in
body 41 is an axial opening 44 and side slot 45 which are sized to
receive conductor 22.
The outer periphery of semicircular member 42 is provided with a
groove 62, the radius of which is approximately equal to the radius
of conductor 22.
Each of the arms 43 fits into a longitudinal slot 46 formed in the
body 41 and is pivotable about a pin 47. The length of each slot 46
is such that an arm 43 mounted therein can be pivoted about pin 47
to a fully retracted position within slot 46. An upper, flat
surface 49 of each arm 43 engages a downwardly facing surface
formed in body 41. The arms 43 extend radially outwardly beyond the
internal diameter of the drill string 12 and are adapted to rest on
an annular notched shoulder 50 formed in the box end of a pipe
section. Shoulder 50 may be provided by milling the box end of the
pipe section in which guide 29 is to be retained, or alternatively
may be provided by a special sub. Each arm may also be secured to
body 46 by a shear pin 48 to prevent the upper guide 29 from being
jarred out of the mounting notch.
The lower guide 30 includes a body 51, a sheave 52, and a weight
53. The body 51 has an upper nose section 54 provided with a side
opening slot 55. The width of slot 55 is slightly larger than the
diameter of conductor 22. The sheave 52 is journalled in body 51 by
bolt 57 and bearing 58. The weight 53 attached to the lower end of
body 51 may be provided by a plurality of cylindrical sections
connected together in end-to-end relation and may include a
centralizer 60 secured thereto. The weight 53 should be
sufficiently large to maintain a downward biasing force on the
conductor to remove or reduce slack in at least a portion of the
conductor. Preferably, the weight should maintain the conductor in
tension. Experience has shown that slack cable can be damaged by
drilling fluid flowing through the drill string 12. A 40-pound
weight has served satisfactorily for a three-sixteenth inch armored
cable.
The surface equipment for lowering or raising the conductor 22 and
associated equipment within the drill string 12 can be similar to
cablehandling equipment used in well logging operations. Such
equipment normally includes a power winch containing a conductor
wound thereon and a sheave suspended from the rig drawworks for
guiding the conductor into or out of the drill string 12.
The conductor 22 and associated equipment may be installed in the
drill string 12 by the following procedure. With the kelly 11
disconnected from the drill string 12, instrument 21 is lowered
into the drill string 12 on conductor 22. The conductor 22 is
unreeled from a power winch and fed into the drill string 12 until
the instrument 21 reaches the desired subsurface location. The
drill string 12 normally will be provided with a suitable
releasable latching means for receiving and engaging the instrument
21.
With the instrument 21 properly located, the conductor 22 extends
to the surface. On the rig floor, the conductor 22 is wound about
the upper and lower guides 29 and 30 in the configuration shown in
FIG. 7, except that the guides 29 and 30 will be positioned in
end-to-end abutting engagement. In installing the conductor 22 on
guide 30, the sheave 52 is first removed from body 51 by
disconnecting bolt 57, and with the conductor 22 wound thereon is
reinstalled on body 51. The guides 29 and 30 with conductor wound
thereon is then inserted into the upper end of the drill string 12.
Arms 43 of the upper guide 29 fit into the notches of shoulder
50.
At this point, it will be observed that the conductor 22 extends
from instrument 21 upwardly to the upper guide 29, around
semiconductor member 42, downwardly to the lower guide 30, around
sheave 52, and upwardly through slot 55 of guide 30 and opening 44
of guide 29. This arrangement provides the conductor 22 with a
convoluted configuration comprising overlapped portions 26, 27, and
28. The lower guide 30 is suspended on a looped portion of the
conductor 22. Additional length of conductor 22 is then unreeled
from the winch and fed through opening 44 of the upper guide 29
lowering the lower guide 30 in the drill string 12. Overlapped
portions 27 and 28 are lengthened as the lower guide 30 descends
within the drill string 12. The conductor 22 which extends from the
instrument 21 to the upper guide 29 passes between adjacent bow
springs of centralizer 60 (if used) and through a guide member 61
strapped to the weight 53. Member 61 and centralizer 60 prevent the
lower guide 30 from twisting with respect to the upper guide
29.
The conductor 22 is fed into the drill string 12 until its upper
terminal end provided with connector 31 engages the upper guide 29.
In the embodiment wherein the kelly 11 is provided with conductor
24 as illustrated in FIG. 4, it is preferred to position connector
31 a short distance above the upper guide 29. This may be achieved
by adding a pipe section, preferably a short pipe section, to the
drill string 12 and pulling the connector 31 and a portion of
conductor 22 through the short pipe section. A second pipe section
is then added to the drill string 12 in the manner described above
with reference to FIGS. 3-6. The short pipe section permits the
mated connectors 31 and 32 to be lowered a short distance below the
top pipe section of the drill string without engaging guide 29 and
the second pipe section is needed to accommodate the tail section
33 of conductor 24.
In other embodiments, as for example where conductor 22 connects to
a conductor embedded in kelly 11 and no tail section is employed,
it will not be necessary to use the short pipe section or to add
the second pipe section.
During drilling operations, additional pipe sections are added to
the drill string 12 as the borehole 17 is advanced until it becomes
necessary to change the drill bit 13 or until the excess length of
conductor 22 is used up. The length of excess conductor 22 stored
in the drill string normally will be sufficient to complete at
least one bit run. The capabilities of a particular bit, of course,
will depend on the types of strata being drilled but normally will
be between about 500 and 3,000 feet.
When it becomes necessary to withdraw the drill string 12 from the
borehole, as for example to replace the bit 13, the conductor 22
and associated equipment will first be retrieved from the drill
string 12 by the following procedure. The kelly 11 is disconnected
from the drill string 12 and the mated connectors 31 and 32 are
pulled through the top pipe section of the drill string 12.
Connector 32 is disconnected from connector 31 and conductor 22 is
withdrawn from the drill string 12 by reeling it on a power winch.
The excess portions 27 and 28 are shortened until the lower guide
30 abuts the upper guide 29. A sufficient amount of tension is then
pulled on the conductor 22 to shear the shear pins 48 (if used)
holding the arms 43 of the upper guide 29 in place. This permits
the arms 43 to pivot free of shoulder 50 and to retract within body
41 which releases the upper guide 29 from the drill string 12. The
assembly is then retrieved from the drill string 12. The apparatus
is disconnected from the conductor 22 and the remaining conductor
22 with the instrument 21 is retrieved. The drill string 12 is then
withdrawn in the usual manner. The drill string 12 with a new bit
13 is lowered into the borehole. With the bit 13 located about two
pipe lengths above the bottom of the borehole, the conductor 22
which was withdrawn from the borehole may be reinstalled in the
drill string 12. However, if additional excess length of conductor
is desired, a longer conductor must be employed.
The conductor 22 usable in the preferred embodiment of the present
invention should have the following properties. It should have a
breaking strength sufficiently high to support the guides 29 and 30
and instrument 21 and to permit shearing of pins 48 (if used); it
should have an operating temperature at least equal to the maximum
subsurface temperature encountered; and it should be sufficiently
flexible to permit it to be arranged in the proper convoluted
configuration. One particular conductor that has been successfully
tested is a single conductor three-sixteenth inch armored cable
manufactured by Vector Cable Company and sold as type 1-18P. Tests
have shown that this cable can be bent around guides having a
2-inch pitch diameter. The tests employed upper and lower guides
similar to those illustrated in FIGS. 7, 8, and 9. Materials and
dimensions of the upper and lower guides were as follows:
Upper Guide (29): Body (41) Material AISI 1018 Steel Outside
diameter, inches 1 3/16 Length, inches 4 9/16 Semicircular Member
(42) Material AISI 1018 Steel Width, inches 1/2 Pitch diameter,
inches 2 Arms (43) Material AISI 1018 Steel Radial extent of outer
ends, inches 1 27/32 Lower Guide (30): Body (51) Material Brass
Length, inches 8 Outside diameter, inches 11/2 Sheave (52) Material
Phosphor Bronze Pitch diameter, inches 2 Width, inches 7/16 Weight
(53) Material Brass Length, inches 68 Outside diameter, inches 11/2
Weight, pounds 40
An instrument suspended on the cable was lowered into internal
upset drill pipe to a depth of about 400 feet. The drill pipe had
an outside diameter of 4.5 inches, an inside diameter of 3.64
inches, and an upset inside diameter of 2.81 inches. The upper and
lower guide assembly with the cable properly arranged thereon was
then placed in the upper end of the drill pipe. About 600 feet of
cable were introduced into the drill pipe forming overlapped
portions having lengths of about 300 feet each. This arrangement
provided about 1,000 feet of cable disposed in the drill pipe,
about 600 feet of which was excess cable. Drilling mud was flowed
through the drill pipe for about 2 hours. The cable and guides were
then withdrawn from the drill pipe without difficulty.
A variation of the invention involves use of a separate retriever
cable for pulling the conductor 22 through a length of pipe to be
added to the drill string. In this variation, the retriever cable
which can be a wireline is threaded through the length of pipe to
be added to the drill string. With the additional length of pipe
suspended in elevators above the drill string, the retriever cable
is connected to the upper terminal end of conductor; one end of the
additional pipe length is connected to the drill string; the
retriever cable is pulled through the additional pipe length
threading conductor 22 upwardly through the additional pipe length.
The conductor 22 is reconnected to conductor 24 and added pipe is
connected to kelly 11. In this embodiment it should be noted that
the threading or extending of a portion of conductor 22 is
performed before the additional length of pipe is connected into
the pipe string; in the embodiment described earlier, the step of
extending the conductor was performed after the additional length
of pipe was connected into the pipe string.
As mentioned previously, the present invention also contemplates an
improved method for lengthening a pipe string while at the same
time lengthening an electric conductor provided therein. The method
involves lowering an insulated conductor 22, preferably an armored
cable free of connectors, to a subsurface terminal near the lower
end of a pipe string used to drill a well; threading a conductor
section, e.g., section 33, through a length of pipe to be added to
the pipe string; connecting the conductor section 33 to conductor
22; and finally connecting the pipe length into the pipe string.
The conductor section 33 preferably is connected to a surface
terminal; it may also be initially disconnected from the surface
terminal and connected to the surface terminal during the operation
for lengthening the pipe string and conductor.
Although the present invention has been described with reference to
conventional rotary drilling operations, it can also be used with
other types of drilling equipment including turbo drills and
positive displacement hydraulic motors. These devices normally
include a motor or turbine mounted on the lower end of the drill
string and adapted to connect to and drive a bit. The motor or
turbine powered by the drilling fluid drives the drill bit while
the drill string remains stationary. When this type subsurface
drilling device is used in directional drilling operations, the
present invention provides a highly useful means for transmitting
directional data to the surface.
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