U.S. patent number 3,825,079 [Application Number 05/383,959] was granted by the patent office on 1974-07-23 for method for mounting an electric conductor in a drill string.
This patent grant is currently assigned to Esso Production Company. Invention is credited to Joe K. Heilhecker.
United States Patent |
3,825,079 |
Heilhecker |
July 23, 1974 |
METHOD FOR MOUNTING AN ELECTRIC CONDUCTOR IN A DRILL STRING
Abstract
Method for performing wellbore telemetry operations wherein an
electric circuit between a subsurface location in a pipe string and
the surface is established and maintained by placing an electric
conductor in the pipe string to extend from the subsurface location
to the surface, arranging the conductor in an overlapped
configuration having an upper loop and a lower loop, biasing the
lower loop downwardly to remove slack from the conductor, advancing
the wellbore in increments of sufficient length to require
lengthening the pipe string and for each such incremental
advancement, lengthening the pipe string by adding a length of pipe
thereto. The length of pipe added to the drill string has extending
therethrough an electrical conductor section for lengthening the
conductor in the pipe string.
Inventors: |
Heilhecker; Joe K. (Houston,
TX) |
Assignee: |
Esso Production Company
(Houston, TX)
|
Family
ID: |
23515473 |
Appl.
No.: |
05/383,959 |
Filed: |
July 30, 1973 |
Current U.S.
Class: |
340/855.1;
166/66; 175/57; 166/385; 175/40; 175/104 |
Current CPC
Class: |
E21B
17/003 (20130101); E21B 23/14 (20130101); E21B
19/00 (20130101); E21B 19/22 (20130101); E21B
4/04 (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 4/04 (20060101); E21B
4/00 (20060101); E21b 007/00 (); E21b 047/12 () |
Field of
Search: |
;166/315,65,65M
;175/57,40,50,104 ;339/16R ;174/47 ;324/8 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Brown; David H.
Attorney, Agent or Firm: Graham; Robert L.
Claims
I claim:
1. A method of establishing and maintaining electric continuity
between a subsurface location within a pipe string used to drill a
well and a location substantially at the surface which comprises
placing an electric conductor string in said pipe string to extend
between said locations; overlapping a portion of said conductor
string to form an upper loop and a lower loop; biasing said lower
loop downwardly while maintaining said upper loop in said pipe
string to remove slack from the said conductor string; advancing
said well in increments of sufficient length to require lengthening
said pipe string; and for each of said incremented advancements
lengthening both said pipe string and said conductor string by
inserting a length of pipe into the pipe string and a conductor
section into the conductor string, said conductor section having a
length different from said pipe length.
2. A method as defined in claim 1 wherein each conductor section is
slightly longer than its associated pipe length and wherein the
biasing step moves the lower loop downwardly from the upper loop to
remove slack from the conductor string introduced by each addition
of a pipe length and a conductor section.
3. A method as defined in claim 1 and further comprising the step
of preventing the upper and lower loops from twisting relative to
one another.
4. A method of establishing and maintaining electric continuity
between a subsurface location within a pipe string used to drill a
well and a location substantially at the surface which comprises
lowering an electric conductor string in said pipe string to extend
between said locations; overlapping a portion of said conductor
string to form an upper loop and a lower loop; biasing said upper
loop and lower loops apart; and preventing said upper loop and
lower loops from twisting relative to one another.
5. A method as defined in claim 4 and further comprising the steps
of advancing said well sufficiently to require the addition of a
length of pipe; adding a conductor section into said conductor
string to lengthen said conductor string by an amount slightly
longer than said length of pipe and adding said length of pipe to
said pipe string to lengthen said pipe string, said step of biasing
said loops apart being operative to remove slack from said
conductor string introduced by the addition of said conductor
section.
6. A method for establishing and maintaining electric continuity
between a subsurface location within a pipe string used to drill a
well and a location substantially at the surface which comprises
lowering an electric conductor string in said pipe string to extend
between said locations; looping said conductor string around upper
and lower guides to form overlapped conductor portions; supporting
the upper guide within said drill string; and mounting said lower
guide on a track connected to said upper guide to maintain the
lower guides in substantial vertical alignment with the upper
guide, said lower guide being suspended on a looped portion of said
conductor string and being movable along said track.
7. A method for installing an electric conductor string within a
rotatable pipe string used to drill a well which comprises lowering
an electric conductor string in said pipe string; looping said
conductor string around upper and lower guides to form overlapped
conductor portions; supporting the upper guide within said drill
string; and maintaining said lower guide in substantial vertical
alignment with said upper guide as said pipe string is rotated to
prevent said overlapped conductor portions from twisting while
enabling said lower guide to move vertically in relation to said
upper guide.
8. A method as defined in claim 7 wherein said upper and lower
guides are maintained in substantial vertical alignment by a rigid
track secured to said upper guide, said lower guide being slidably
mounted on said track.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an improved method for performing
wellbore telemetry operations. In one aspect it relates to a method
for establishing and maintaining electric continuity between a
subsurface location in a rotary drill string and a surface
location.
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
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 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 conventional rotary
drilling, a borehole is advanced by rotating a drill string
provided with a drill bit at its lower end. Lengths of drill pipe,
usually about 30 feet long, are added to the drill string,
one-at-a-time, as the borehole is advanced in increments. In
adapting an electric telemetry system to rotary drilling equipment,
the means for transmitting the electric signal through the drill
string must be such to permit the connection of additional pipe
lengths to the drill string as the borehole is advanced.
An early approach to the problem involved the use of continuous
electric 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 from the drill
string each time a pipe length was added to the drill string. A
more recent approach involves the use of special drill pipe. Each
pipe section of the special pipe is provided with an electric
conductor having connectors at its opposite ends. Electric
continuity is maintained across the junction of two pipe sections
by connectors of one section contacting a connector on the adjacent
pipe section (see U.S. Pats. No. 3,518,608 and 3,518,609).
Disadvantages of this system include the high cost of the special
pipe sections, the need for a large number of electric connections
(one at each joint), and the difficulty of maintaining insulation
of the electric connectors at each joint.
Still another approach involves the use of cable sections mounted
in each pipe section (See U.S. Pat. No. 2,748,358). The cable
sections are connected together as pipe sections are added to the
drill string. Each cable section is normally made slightly longer
than its associated pipe section, with the result that a small
amount of slack is present in the conductor string at all times.
Drilling fluid flowing through the drill string exerts a fluid drag
on the loose cable which tends to damage the connectors or snarl
the cable.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide an electric
circuit between a subsurface location in a well and the surface,
thereby permitting the monitoring of a subsurface condition during
drilling operations. The invention also contemplates that the
circuit between the surface and subsurface locations may be used to
actuate a subsurface instrument employed in the drill string.
Briefly, the method involves placing within a pipe string used to
drill a well an insulated electric conductor string; while
maintaining said electric conductor string in tension, advancing
said well in increments sufficiently long to require additional
pipe, and for each incremental advancement inserting into the
system a pipe length provided with an electric conductor section to
lengthen both the pipe string and the conductor string.
Important advantages of the method of the present invention over
prior art techniques are that it permits the use of individual
conductor sections without the need for multiple supports within
the pipe string; the conductor is maintained in tension during the
drilling operation so that the disturbance of fluid flow on the
conductor is minimized; and means for maintaining the conductor in
tension compensates for variation in lengths of the conductor and
removes slack from the conductor string each time a conductor
section is added to the conductor string.
Apparatus usable in the method described above include an upper
guide supported within the pipe string, a lower guide disposed
below the upper guide, an electric conductor extending from a
subsurface location within the pipe string around the upper and
lower guides and to the surface, and means, preferably a track
between the guides, for preventing relative rotary movement of the
upper and lower guides but permitting relative axial movement
therebetween.
An important feature of the apparatus is that it prevents the
overlapped conductor lengths from twisting as a result of the
rotary action of the drill pipe. Experience has shown that rotation
of the drill pipe containing overlapped cable lengths can sometimes
cause the cable to become twisted or snarled. By incorporating a
track or guide for preventing relative angular movement of the
upper and lower guides, the risk of cable twisting or snarling is
minimized.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of well drilling equipment provided with
an electric conductor for transmitting an electric signal between
subsurface location and the surface.
FIG. 2 is a side elevation view of the apparatus useful in the
method of the present invention.
FIG. 3 is a view similar to FIG. 2 showing the apparatus revolved
90.degree. from the position of FIG. 2.
FIG. 4 is a transverse sectional view of apparatus shown in FIG. 3,
with the cutting plane taken generally through line 4--4
thereof.
FIG. 5 is a transverse sectional view of the apparatus shown in
FIG. 2 with the cutting plane taken generally through the line 5--5
thereof.
FIGS. 6, 7, and 8 are sequence views illustrating a procedure for
lengthening the conductor and pipe strings during drilling
operations.
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 tubular pipe
between the bit 13 and the kelly 11; and the term "pipe string"
refers to the complete pipe column including the kelly 11. The
major portion of the dril 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, either drill
pipe or drill collars, connected together in end-to-end
relation.
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 (not shown) attached to hose
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 rotaty table. The
present invention may also be used in systems which employ a power
swivel in lieu of a kelly and rotary table; for purposes of
illustration, however, it will be described in connection with the
kelly and rotary table arrangement.)
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 electric 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 tubular pipe to
transmit electric energy between the subsurface and surface
location, it finds particularly advantageous application in a
wellbore telemetry system such as that illustrated in FIG. 1 which
comprises an instrument 21, conductor string 22, and receiver
28.
The instrument 21 capable of measuring a subsurface condition and
generating an electric signal indicative or representative of that
condition is mounted or adapted to be mounted in 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 present invention is concerned primarily with a method for
maintaining the electric conductor in the pipe string 12 during
drilling operations. The energy transmitted through conductor 22
may be a signal generated by the subsurface instrument 21 and
transmitted to the receiver 28 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.
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 electric 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.
In one aspect, the present invention contemplates maintaining the
conductor string 22 in tension as drilling operations are in
progress. As schematically illustrated in FIG. 1, the conductor
string 22 extends from instrument 21 around upper and lower guides
23 and 24 disposed in the drill string 12, and to the surface where
it connects to kelly conductor 25. In this embodiment, the kelly
conductor 25 extends through the kelly 11 and connects to a
terminal located at the upper end of the kelly 11. It should be
observed, however, that conductor 25 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 25 at that location.
In order to facilitate the addition of pipe sections to the drill
string 12, however, it is preferred that conductor 25 extend
through the interior of the kelly 11 as illustrated and connect to
the upper end of conductor string 22 a short distance (e.g. 1 or 2
feet) below the lower end of kelly 11.
In telemetry operations are to be performed while the kelly 11 and
drill string 12 are rotating, the upper end of conductor 25 will be
connected to a device 26 capable of transmitting electric energy
from a rotating member to a stationary member. Device 26 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 26 and electric
conductor 27 provide means for transmitting signals from the
conductor string 22 within the pipe string to receiver 28. 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 29, part of the return path,
interconnects stationary portion of device 26 and receiver 28. If
telemetry operations are to be performed at times when the drill
string 12 and kelly 11 are stationary, device 26 will not be needed
and the conductors 27 and 29 may be connected directly to conductor
22 and ground through a suitable connector. In this situation,
conductors 27 and 29 will be disconnected from conductor string 22
and ground when the kelly 11 and drill string 12 are rotated. Other
means for transmitting the signal to the receiver 28 include a
wireless transmitter connected to conductors 22 or 25 and located
on a rotating member, e.g., kelly 11.
The receiver 28 is an instrument capable of receiving the signal
generated by instrument 21 and reducing it to useful form.
In performing the method of the present invention, the conductor
string 22 with instrument 21 suspended thereon is first lowered
within the drill string 12 until instrument 21 is located at the
proper subsurface location. At the surface, conductor 22 is looped
over guides 23 and 24 to provide an overlapped configuration.
This guide assembly with conductor looped therearound is then
lowered within the drill string 12. In a preferred form, the upper
guide 23 is supported within the drill string and the lower guide
24 is suspended on a looped portion of conductor 22. The lower
guide 24 which may include a weight 30 maintains tension on the
conductor 22 and is free to move toward or away from the upper
guide as conductor 22 is retrieved from or fed into the drill
string 12. With the guide assembly installed in the drill string
12, the upper terminal end of conductor string 22 is connected to
kelly conductor 25. Connection of the kelly 11 to the drill string
12 places the equipment in condition for drilling and for
performing telemetry operations if desired.
Under normal drilling, the wellbore is advanced in increments of
sufficient length to require lengthening both the drill string 12
and conductor string 22 disposed therein. The procedure for
lengthening these strings will be described with reference to FIGS.
6-8 wherein a length of pipe 31 to be added to the drill string 12
is shown disposed in a shallow hole 32 ("mouse hole") below the
derrick floor. The length of pipe 31 is provided with a conductor
section 33 having electrical connectors 34 and 35 at its opposite
ends. Conductor 35 is adapted to mate with connector 36 at the
upper terminal end of conductor string 22, and connector 34 is
adapted to mate with the lower terminal connector 37 of kelly
conductor 25. The connectors of adjacent conductor sections 31 are
also adapted to mate; that is, lower connector 35 of one section 31
mates with upper connector 34 of the preceding section in the
conductor string 22. As illustrated in FIG. 6, each conductor
section 33 is slightly longer than its associated pipe length 31.
The longer conductor section facilitates the connecting procedure
because it ensures that the lower connector 35 will be exposed
below the pipe length 31 with the later suspended from kelly
11.
In inserting each pipe section 31 provided with conductor section
33, the drill string 12 is initially elevated and suspended in the
rotary table 16 and the kelly 11 disconnected from drill string 12.
The kelly 11 is elevated pulling mated connectors 36 and 37 above
the upper end of drill string 12. A support plate 38 or spider is
inserted between the upper end of the drill string and connector
36, and serves to support the conductor string 22. Connectors 36
and 37 are then separated. FIG. 6 illustrates the position of the
equipment at this juncture in the procedure. The kelly 11 is swung
over into alignment with pipe length 31 and the kelly conductor 25
is connected to conductor section 33 by mating connectors 37 and
34. (See FIG. 7.) The kelly 11 is then screwed into the pipe
section 31. This assembly is elevated above the drill string 12.
Exposed connector 35 is mated with connector 36 inserting conductor
section 33 into the conductor string 22. After the support plate 38
is removed, the lower end of pipe length 31 is screwed into the
drill string 12 and becomes a part thereof. (See FIG. 8.) The mated
connectors 35 and 36 are pulled downwardly within the drill string
12 by the lower guide 24 until all slack introduced by the
conductor section 33 is removed from the conductor string 22. The
equipment is then returned to the drilling position and drilling
operations resumed. For each incremental advancement of the
borehole of approximately 30 feet, the drill string 12 and
conductor string 22 are lengthened by the procedure described
above.
It will be seen from FIG. 1 that the lower guide 24 is free to move
downwardly relative to the upper guide 23 each time the drill
string 12 and conductor string 22 are lengthened. The overlapped
lengths of conductor 22 between guides 23 and 24 will normally be
short at the beginning of the operation but will become longer as
the well is advanced and as pipe lengths 31 and conductor sections
33 are added into the system.
The amount of initial overlap will be determined, in part, by the
length of conductor string 22 and the length of drill string 12 at
the time the telemetry equipment is introduced intothe system.
Since the conductor string 22, as delivered to the drilling site,
will normally have a fixed length, it will be necessary to adjust
the length of the drill string 12 to approximate that of the
conductor string 22. This can be done by lowering the drill string
12 in the well until its length is about 15 to 30 feet shorter than
the length of conductor string. The excess length of conductor can
be used to form the overlapped portions of the conductor string 22.
If the excess length is 30 feet, the overlapped portions will each
be 15 feet long and the lower guide 24 will initially be 15 feet
below the upper guide 23.
It is thus seen that the apparatus for maintaining the conductor
within the drill string 12 serves three important functions: (1) it
maintains the conductor in tension, preventing it from being
excessively disturbed by the drilling fluid being pumped through
the drill string; (2) it permits variations in the length of the
conductor string as initially installed; and (3) it removes slack
from the conductor string as conductor sections are introduced into
the conductor string.
Details of a preferred construction of the apparatus useful in the
present invention are shown in FIGS. 2-5. As illustrated, the upper
guide 23 comprises a cylindrical body member 41, a sheave 42
journaled to body 41, support arms 43, and guide rollers 44 and 45.
The sheave 42 is mounted for free-wheel rotation on shaft 47 and is
disposed within opening 46 formed in the body 41. The outer side of
the opening 46 is closed by the panel 48 (shown cutaway in FIG. 3).
The sheave 42 has a grooved outer periphery for retaining conductor
22. Its pitch diameter is sufficiently small to fit within the
drill string 12 and yet permit the conductor 22 to be bent
therearound. The rollers 44 and 45 are mounted for free-wheel
rotation in an opening 49 formed in the body 41 at a location above
the sheave opening 46 but laterally offset therefrom. Opening 49 is
enclosed on one side by panel 51 (shown cutaway in FIG. 3). Panels
48 and 51 are secured to body 41 by fasteners such as screws but
are removable therefrom to permit the conductor 22 to be mounted on
the apparatus.
The support arms 43 are pivotally mounted in the upper extremity of
the body 41. In the supporting position the arms 43 extend radially
outwardly as illustrated and rest on the box end of a drill pipe
section. The arms 43, however, are pivotable downwardly into
suitable slots 52 formed in the body member 41 to permit the
assembly to be retrieved from the drill string 12 if desired. A
central opening 53 extends from opening 49 through the upper nose
end of the body 41. A side opening slot 54 (see FIG. 4) provides
access to opening 53.
The lower guide 24 which is adapted to be suspended on a looped
portion of the conductor 22 is movable in relation to the upper
guide 23, preferably, along a stabilizing track 55. The lower guide
24 includes an elongated body member 56, a sheave 57 journalled to
body 56, and means for slidably mounting the lower body 56 on track
55. Lower sheave 57 which can be about the same size and structure
as the upper sheave 42 is mounted for free-wheel rotation on shaft
58 within opening 59 formed in body member 56. Panel 61 closes one
side of opening 59 and serves tO prevent conductor 22 from becoming
dislodged from the lower guide assembly. In the embodiment
illustrated in FIGS. 2 and 3, the lower sheave 57 is slightly
smaller in diameter than sheave 42 and is positioned in approximate
vertical alignment with rollers 44 and 45.
The lower body member 56 preferably is roughly semicircular in
cross section having a flat longitudinal surface 62 (see FIG. 5).
The track 55 which serves to maintain the lower guide 24 in the
proper attitude in relation to the upper guide 23 may be
rectangular, square, or triangular in cross section or any other
configuration which prevents relative angular movement of the lower
guide 24. Fastening means such as clamps 66 and 67 maintain the
body member 56 slidably secured to the track 55 at axially spaced
points.
In the embodiment disclosed herein, the track 55 is in the form of
an elongate triangular member having diverging legs 63 and 64 (see
FIG. 5). The outer edges of the legs 63 and 64 are adapted to
engage the flat surface 62 at laterally spaced points and the
clamps 66 and 67 have V-shaped interiors conforming to the outer
surface of track 55. Clamps 66 and 67 may be bolted to the body as
illustrated. The upper end of the track 55 is secured to the upper
body member 41 by suitable fasteners such as bolts 68. The lower
end of the track 55 may be provided with a centralizer 69 which
includes a plurality of bow springs 70.
The overall length of the apparatus including upper guide 23, lower
guide 24, track 55, and centralizer 69 need not exceed the length
of one or two pipe sections or approximately 30 to 60 feet.
However, if desired, it can be made to extend a considerable
distance within the drill string 12 by employing tracks that
connect together in end-to-end relation; it is possible for the
track 55 to extend several hundred feet. A long track would be
required for a system such as that disclosed in assignee's
copending application Ser. No. 350,459 which stores conductor
within the drill string using upper and lower guides and supplies
lengths of conductor as the drill string is lengthened. In such a
system the guides normally are initially disposed far apart and
move toward one another as the excess length of conductor is used
up. For purposes of the present invention, however, the track 55
may be considered as being approximately equal to one 30-foot pipe
section.
The upper and lower body members 41 and 56 may be machined from
steel or other strong metal. The track 55, sheaves 42, 57, and
rollers 44 and 45 are of conventional construction and are
commercially available. The lower body member 56 should be
sufficiently long to provide sufficient weight to impart a downward
tensioning force on the conductor looped thereon. A weight of about
forty pounds should be sufficient for most applications.
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 23 and 24
and instrument 21; 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. A particularly suitable conductor
is a single conductor 3/16-inch armored cable manufactured by
Vector Cable Company and sold as Type 1-18P. Tests have shown that
this cable can be bent around sheaves having a pitch diameter of
two inches.
Both the upper and lower assemblies with conductor wound thereon
should have a sufficiently small diameter to pass through the
interior of a drill string. For a 41/2 inch drill pipe with
internal upset I. D. of 2.81 inches, 2 inch sheaves and somewhat
smaller body diameters provide adequate clearance.
The installation of the apparatus and performance of the method of
the present invention is described below. After drilling has
progressed to the point that it is desired to commence wellbore
telemetry operations, drilling operations are interrupted and an
instrument 21 is lowered into the pipe string on the conductor 22
using conventional techniques. For this operation, a sheave
disposed above the derrick floor is normally employed to guide the
conductor string 22 into the wellbore as it is unreeled from a
drum. With the instrument 21 properly seated in the lower end of
the pipe string 12, preferably in a locking sub immediately above
bit 13, the conductor 22 is manually looped around the upper and
lower sheaves 42 and 57, threaded between the guide rollers 44 and
45 and positioned in the nose opening 53. With the conductor string
22 properly mounted on the apparatus, the panels 48, 51, and 61 are
installed and, by use of rig drawworks, the assembly is elevated
above the derrick floor and lowered into the drill string 12. This
may be achieved by connecting the conductor connector 36 to the
kelly connector 37 and elevating the kelly 11. The lower guide 24,
following track 55, is drawn up into abutting engagement with the
upper guide 23; the entire assembly is raised by elevating the
kelly 11. The assembly is lowered through the upper end of the pipe
string until the support arms 43 engage the box end of the top pipe
section.
Since connector 36 cannot pass through opening 53 in body member
41, conductor 22 should extend a short distance above the upper
guide 23. To provide a length of conductor above the upper guide
23, conductor 22 is fed into the drill string 12 lowering guide 24
along track 55 to its lowermost position. This also places the
connector 36 near the upper guide 23. A length of pipe is then
added to the upper end of the drill string 12 and the conductor 22
threaded upwardly through the added pipe length. This moves the
lower guide to about the mid point of track 55.
As drilling operations proceed, pipe lengths and conductor sections
are added to lengthen both the pipe string and the conductor in the
manner described previously with reference to FIGS. 6-8. This
condition is schematically illustrated in FIG. 1 which shows the
conductor string as comprising the original long conductor trained
about the guides 23 and 24 and a plurality of conductor sections 33
extending from connector 36 to the surface.
Since the conductor sections are normally longer than the pipe
length, the lower guide moves downwardly a short distance away from
the upper guide 23 for each lengthening of the pipe string and
conductor string 22. The lower guide 24 is sufficiently heavy to
remove slack from the conductor string 22. If the excess length of
conductor averages one foot, about 30 pipe lengths may be added as
the drilling progresses. This should place the lower guide 24 near
the lower end of the track 55 and the connector 36 near the upper
guide assembly. The apparatus may be returned to its original
condition merely by pulling the conductor string 22 upwardly and
removing one of the conductor sections 33 from the conductor string
22. This moves the lower guide 24 along track 55 about 15 feet and
moves the connector 36 about 30 feet above the upper guide 23.
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 turbodrills 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.
* * * * *