Communications: electrical – Wellbore telemetering or control – Selective control of subsurface equipment
Reexamination Certificate
2000-11-30
2004-12-21
Dang, Hung (Department: 2635)
Communications: electrical
Wellbore telemetering or control
Selective control of subsurface equipment
C340S853600, C340S853800, C166S255100
Reexamination Certificate
active
06833795
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of underground boring and, more particularly, to a system and method of detecting buried objects and utilities in proximity with a drill pipe/cutting tool during underground boring system operation.
Utility lines for water, electricity, gas, telephone, and cable television are often run underground for reasons of safety and aesthetics. In many situations, the underground utilities can be buried in a trench which is then back-filled. Although useful in areas of new construction, the burial of utilities in a trench has certain disadvantages. In areas supporting existing construction, a trench can cause serious disturbance to structures or roadways. Further, there is a high probability that digging a trench may damage previously buried utilities, and that structures or roadways disturbed by digging the trench are rarely restored to their original condition. Also, an open trench may pose a danger of injury to workers and passersby.
The general technique of boring a horizontal underground hole has recently been developed in order to overcome the disadvantages described above, as well as others unaddressed when employing conventional trenching techniques. In accordance with such a general horizontal boring technique, also referred to as horizontal directional drilling (HDD) or trenchless underground boring, a boring system is situated on the ground surface and drills a hole into the ground at an oblique angle with respect to the ground surface. A drilling fluid is typically flowed through the drill string, over the boring tool, and back up the borehole in order to remove cuttings and dirt. After the boring tool reaches a desired depth, the tool is then directed along a substantially horizontal path to create a horizontal borehole. After the desired length of borehole has been obtained, the tool is then directed upwards to break through to the earth's surface. A reamer is then attached to the drill string which is pulled back through the borehole, thus reaming out the borehole to a larger diameter. It is common to attach a utility line or other conduit to the reaming tool so that it is dragged through the borehole along with the reamer.
It can be appreciated that contacting or striking an underground utility or other unknown buried obstruction by the drill string and/or cutting head may represent a significant hazard to workers and others near the work site. A common approach to addressing the potential hazards facing workers due to a utility strike, for example, involves the use of an above-ground locator. Although such an approach improves the chances of detecting utilities and obstructions situated ahead of the drill pipe/cutting tool, several factors can negatively influence the accuracy and reliability of above-ground locators, including sensitivity and range limitations, operator skill and interpretive capabilities, changing or undesirable geology, presence of natural or manmade buried structures, and the like.
There exists a need in the excavation industry for an apparatus and methodology for detecting buried objects, such as utilities, lying ahead of an approaching drill string/cutting tool. There exists the further need for such an apparatus and methodology that provides for increased boring safety upon detecting a buried object. The present invention fulfills these and other needs.
SUMMARY OF THE INVENTION
The present invention is directed to an apparatus and method for detecting underground objects for use with a horizontal directional drilling (HDD) machine. In accordance with an embodiment of the present invention, a drill pipe is configured to cooperate with the HDD machine to produce a horizontal bore. A transmit apparatus is provided with the drill pipe and transmits electromagnetic probe signals ahead of the drill pipe. Optionally or in addition, the transmit apparatus transmits electromagnetic probe signals lateral to the drill pipe.
A receive apparatus is provided with the drill pipe and receives electromagnetic return signals resulting from the probe signals. A processor, coupled to the transmit and receive apparatuses, compares characteristics, such as amplitudes, of at least some of the return signals, and generates an alert signal indicative of a detected object in proximity with the drill pipe in response to the processor comparing return signals having about the same amplitude.
The transmit apparatus and receive apparatus, according to one configuration, share one or more common antennae. According to another configuration, the transmit apparatus may include two transmit antennas situated apart from one another on the drill pipe. The two transmit antennas may, for example, be situated about 180 degrees from one another on the drill pipe. The receive apparatus may include a single receive antenna or two or more receive antennas.
According to further configuration, the receive apparatus may include two receive antennas situated apart from one another on the drill pipe. The two receive antennas may, for example, by situated about 180 degrees from one another on the drill pipe. The transmit apparatus may include a single transmit antenna or two or more transmit antennas.
The object detection apparatus may further include an orientation sensor provided with the drill pipe. The orientation sensor generates a horizontal orientation signal indicating that one or more antennae of the transmit and receive apparatuses are oriented along a substantially horizontal plane relative to a surface of the earth. The processor, according to this embodiment, compares the return signal amplitudes in response to the horizontal orientation signal.
The drill pipe may be configured to include an integral or attachable cutting tool, and the receive and transmit apparatuses may be provided with the cutting tool. The drill pipe and the cutting tool may be provided with one or both of receive and transmit apparatuses, respectively.
The processor may be a distributed processor which includes a first processor provided at the drill pipe and a second processor provided at the HDD machine. The distributed processor may also include a processor provided in an above-ground locator or repeater. The first processor may communicate the return signals to the second processor, and the second processor may generate the alert signal. The first processor may alternatively generate the alert signal. The first processor may communicate a processed set of data developed from the return signals to the second processor, in which case the second processor receives the processed data set from the first processor for further processing at the HDD machine.
According to a further embodiment, the underground object detection apparatus includes a side looking object detection apparatus, in addition to or exclusive of a forward looking object detection apparatus. In one configuration, according to this embodiment, the transmit apparatus transmits electromagnetic probe signals lateral to the drill pipe. The receive apparatus receives electromagnetic lateral return signals resulting from the laterally transmitted probe signals. The processor compares amplitudes of at least some of the lateral return signals, and generates an alert signal indicative of a detected object in proximity with a side of the drill pipe in response to the processor comparing lateral return signals having about the same amplitude.
The transmit and receive apparatuses, according to one embodiment, define an impulse or chirp ground penetrating radar apparatus. According to another embodiment, the transmit and receive apparatuses define a stepped-frequency ground penetrating radar apparatus. In accordance with yet another embodiment, the transmit and receive apparatuses define a swept-frequency ground penetrating radar apparatus.
In accordance with another embodiment, an underground object detection apparatus of the present invention includes a horizontal directional drilling (HDD) machine. A drill pipe is coupled to the HDD machine and is controlled by the HDD
Alft Kevin
Bogatyrev Eugene
Johnson Dennis J.
Crawford & Maunu PLLC
Dang Hung
Vermeer Manufacturing Company
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