Wells – Processes – Assembling well part
Reexamination Certificate
2001-02-26
2002-09-10
Neuder, William (Department: 3672)
Wells
Processes
Assembling well part
C166S065100, C175S320000, C439S578000
Reexamination Certificate
active
06446728
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to underground directional boring and more particularly, to automatically extending and retracting electrically isolated conductors provided in a segmented drill string. An associated method is also disclosed.
Guided horizontal directional drilling techniques are employed for a number of purposes including, for example, the trenchless installation of underground utilities such as electric and telephone cables and water and gas lines. As a further enhancement, state of the art directional drilling systems include configurations which permit location and tracking of an underground boring tool during a directional drilling operation. As will be seen, the effectiveness of such configurations can be improved by providing an electrical pathway between a drill rig which operates the boring tool and the boring tool itself.
Turning to
FIG. 1
, a horizontal boring operation is illustrated being performed using a boring/drilling system generally indicated by the reference numeral
10
. The drilling operation is performed in a region of ground
12
including an existing underground utility
14
. The surface of the ground is indicated by reference number
16
.
System
10
includes a drill rig
18
having a carriage
20
received for movement along the length of an opposing pair of rails
22
which are, in turn, mounted on a frame
24
. A conventional arrangement (not shown) is provided for moving carriage
20
along rails
22
. During drilling, carriage
20
pushes a drill string
26
into the ground and, further, is configured for rotating the drill string while pushing. The drill string is made up of a series of individual drill string or drill pipe sections
28
, each of which includes any suitable length such as, for example, ten feet. Therefore, during drilling, drill pipe sections must be added to the drill string as it is extended or removed from the drill string as it is retracted. In this regard, drill rig
18
may be configured for automatically or semi-automatically adding or removing the drill string sections as needed during the drilling operation. Underground bending of the drill string enables steering, but has been exaggerated for illustrative purposes.
Still referring to
FIG. 1
, a boring tool
30
includes an asymmetric face
32
and is attached to the end of drill string
36
. Steering of the boring tool is accomplished by orienting face
32
of the boring tool (using the drill string) such that the boring tool is deflected in the desired direction. Boring tool
30
includes a mono-axial antenna such as a dipole antenna
44
which is driven by a transmitter
46
so that a magnetic locating signal
48
is emanated from antenna
44
. In one embodiment, power may be supplied to transmitter
46
from a set of batteries
50
via a power supply
52
. In another embodiment (not shown), to be described in further detail below, an insulated electrical conductor is installed within the drill string between the drill rig and the boring tool in order to carry power to transmitter
46
. A control console
54
is provided at the drill rig for use in controlling and/or monitoring the drilling operation. The control console includes a display screen
56
, an input device such as a keyboard
58
and a plurality of control levers
60
which, for example, hydraulically control movement of carriage
20
along with other relevant functions of drill rig operation.
Drill pipe
28
defines a through passage (not shown) for a number of reasons, including considerations of design, manufacturing methods, strength, and weight, but also because typical horizontal directional drilling also requires the use of some type of drilling fluid (not shown), most commonly a suspension of the mineral bentonite in water (commonly referred to as “drilling mud”). Drilling mud, which is generally alkaline, is emitted under pressure through orifices (not shown) in boring tool
30
after being pumped through the interior passage of drill pipes
28
which make up drill string
26
. Drilling mud is typically pumped using a mud pump and associated equipment (none of which are shown) that is located on or near drill rig
18
. The pressures at which the drilling mud is pumped can vary widely, with a commonly encountered range of operation being 100 PSI to 4,000 PSI, depending on the design and size of the particular drill rig. For proper operation, pipe connections between drill pipe sections
28
must not only be sufficiently strong to join the sections against various thrust, pull and torque forces to which the drill string is subjected, but they must also form a seal so as to not allow the escape of drilling mud from these connections which could result in an unacceptable drop in drilling mud pressure at the orifices of the boring tool.
Continuing to refer to
FIG. 1
, drilling system
10
may include a portable locator/controller
70
held by an operator
72
for sensing locating signal
48
in a way which allows the underground position of boring tool
30
to be identified. Such portable detectors are described, for example, in U.S. Pat. Nos. 5,155,442, 5,337,002, 5,444,382 and 5,633,589 as issued to Mercer et al, all of which are incorporated herein by reference. Alternatively, one or more detectors (not shown) designed for positioning at fixed, above ground locations may be used, as described in U.S. patent application Ser. No. 08/835,834, filing date Apr. 16, 1997, which is commonly assigned with the present application and is incorporated herein by reference.
Guided horizontal directional drilling equipment is typically employed in circumstances where the inaccuracies and lack of steering capability of non-guided drilling equipment would be problematic. A typical example is the situation illustrated in
FIG. 1
in which the intended drill path requires steering the boring tool around, in this instance beneath, obstacles such as utility
14
. Guided drilling is also important where the intended path is curved (not shown) or the target destination is more than a short distance (typically over
50
feet) from the starting point. In the latter situation, simply aiming a non-guided boring tool at the target destination from the starting point will seldom result in maintaining a sufficiently accurate drill path and/or arriving reasonably close to the target destination.
While system
10
of
FIG. 1
illustrates a “walk-over” type locating system using a steerable boring tool, it should be appreciated that “non-walkover” guidance/locating systems (not shown) are also useful in conjunction with steerable boring tools. The less commonly used non-walkover systems typically utilize an instrumentation/sensor package (not shown) located in the boring tool that is electrically connected directly to console
54
at the drill rig via the aforementioned insulated electrical conductor (not shown) located inside the through passage of the drill string. While batteries
50
may be used in the boring tool to power the instrumentation/sensor package, the insulated conductor may be used to supply electrical power to the instrumentation/sensor package, thus eliminating batteries
50
for reasons which will be seen. At the same time, data may be transmitted from the instrumentation/sensor package to console
54
on the insulated conductor. Data can also be sent to the instrumentation/sensor package for calibration, signal processing and programming.
In the instance of both walkover and non-walkover systems, the objective is to use information obtained from the locating system as a basis for making corrections and adjustments to the direction of steerable boring tool
30
in order to drill a bore hole that follows an intended drill path. Therefore, in most drilling scenarios, a walkover system is particularly advantageous in since the origin of the locating signal leads directly to the position of the boring tool. Typically, the locating signal, in a walkover system, is also used to transmit to above ground locations encoded information including the roll and pitch or
Chau Albert W.
Mercer John E.
Digital Control, Inc.
Neuder William
Pritzkau Michael
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