Mining or in situ disintegration of hard material – Processes – Mine safety
Reexamination Certificate
2001-07-12
2002-12-24
Bagnell, David (Department: 3672)
Mining or in situ disintegration of hard material
Processes
Mine safety
C299S019000, C175S050000, C324S338000, C324S351000, C702S011000
Reexamination Certificate
active
06497457
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to coal mining, and more specifically to using directional drilling to bore horizontally through a coal deposit so methane can be drained off to safe levels and electronic imaging with ground penetrating radar to more accurately estimate the true coal reserve.
2. Description of the Prior Art
Natural deposits of coal are sometimes permeated with methane gas, e.g., coalbed methane (CBM). Water seepage is another problem in coal mining, and it needs to be drained off to prevent flooding. In certain concentrations, the methane gas can be explosive and a general hazard to mining operations. So the methane is conventionally vented off until safe concentration levels are reached. Very often this means wasting the gas instead of collecting it and distributing it for sale.
Ventilating furnaces were once used to ventilate mines with chimney drafts. Electric power and fans were yet to be developed. The ventilating furnace was located at the bottom of the mine, and this, of course, posed an ignition hazard for high enough methane concentrations. Explosions caused by the ventilating furnaces were a frequent occurrence.
In U.S. Pat. No. 3,934,649, issued Jan. 27, 1976, Pasini and Overby describe a method for removing methane from coalbeds prior to mining the coal. It comprises drilling at least one borehole from the surface into the coalbed. The borehole is started at a slant rather than directly vertically, and as it descends, a gradual curve is followed until a horizontal position is reached where the desired portion of the coalbed is intersected. Approaching the coalbed in this manner and fracturing the coalbed in the major natural fraction direction cause release of large amounts of the trapped methane gas.
U.S. Pat. No. 4,299,295, issued Nov. 10, 1981, to Amzi Gossard, describes a process for drilling spaced horizontal boreholes in coal and other mineral deposits. The boreholes are typically in excess of 1500 feet long, and patterned to maximize gas removal. Directional drilling guidance is provided by a continuous downhole survey tool connected to data display devices by an internal drill rod cable system. Directional drilling control is provided by a positive displacement motor positioned at the end of the drill string and operated by a flow of drilling fluid through the drill string from the drilling rig. The mineral strata surrounding the borehole is periodically hydrofractured to permit effective removal of the gas. The hydrofractionation is effected without removal of the drill string or survey instruments from the borehole. Upon completion of the borehole, the drill string is removed and gas which enters the borehole from the surrounding deposit is withdrawn.
David Summers, et al., describe in U.S. Pat. No. 4,317,492, a method and apparatus for drilling horizontal holes in geological structures from a vertical bore. The geological structures intended to be penetrated in this fashion are coal seams, as for in situ gasification or methane drainage, or in oil-bearing strata for increasing the flow rate from a pre-existing well. Other possible uses for this device might be for use in the leaching of uranium ore from underground deposits or for introducing horizontal channels for water and steam injections.
The present inventor, Larry G. Stolarzyck, has described methods and equipment for imaging coal formations in geologic structures in many United States Patents. Some of those Patents are listed in Table I, and are incorporated herein by reference.
TABLE I
Patent No.
Issued
Title
U.S. Pat. No. 04577153
Mar. 18, 1986
Continuous Wave Medium Frequency Signal
Transmission Survey Procedure For
Imaging Structure In Coal Seams
U.S. Pat. No. 04691166
Sept. 01, 1987
Electromagnetic Instruments For Imaging
Structure In Geologic Formations
U.S. Pat. No. 04742305
May 03, 1988
Method For Constructing Vertical Images
Of Anomalies In Geological Formations
U.S. Pat. No. 04753484
June 28, 1988
Method For Remote Control Of A Coal
Shearer
U.S. Pat. No. 04777652
Oct. 11, 1988
Radio Communication Systems For
Underground Mines
U.S. Pat. No. 04879755
Nov. 07, 1989
Medium Frequency Mine Communication
System
U.S. Pat. No. 04968978
Nov. 06, 1990
Long Range Multiple Point Wireless
Control And Monitoring System
U.S. Pat. No. 04994747
Feb. 19, 1991
Method And Apparatus For Detecting
Underground Electrically Conductive
Objects
U.S. Pat. No. 05066917
Nov. 19, 1991
Long Feature Vertical Or Horizontal
Electrical Conductor Detection
Methodology Using Phase Coherent
Electromagnetic Instrumentation
U.S. Pat. No. 05072172
Dec. 10, 1991
Method And Apparatus For Measuring The
Thickness Of A Layer Of Geologic
Material Using A Microstrip Antenna
U.S. Pat. No. 05087099
Feb. 11, 1992
Long Range Multiple Point Wireless
Control And Monitoring System
U.S. Pat. No. 05093929
Mar. 03, 1992
Medium Frequency Mine Communication
System
U.S. Pat. No. 05121971
June 16, 1992
Method Of Measuring Uncut Coal Rib
Thickness In A Mine
U.S. Pat. No. 05146611
Sept. 08, 1992
Mine Communication Cable And Method For
Use
U.S. Pat. No. 05181934
Jan. 26, 1993
Method For Automatically Adjusting The
Cutting Drum Position Of A Resource
Cutting Machine
U.S. Pat. No. 05188426
Feb. 23, 1993
Method For Controlling The Thickness Of
A Layer Of Material In A Seam
U.S. Pat. No. 05260660
Nov. 09, 1993
Method For Calibrating A Downhole
Receiver Used In Electromagnetic
Instrumentation For Detecting An
Underground Conductor
U.S. Pat. No. 05268683
Dec. 07, 1993
Method Of Transmitting Data From A
Drillhead
U.S. Pat. No. 05301082
Apr. 05, 1994
Current Limiter Circuit
U.S. Pat. No. 05408182
Apr. 18, 1995
Facility And Method For The Detection
And Monitoring Of Plumes Below A Waste
Containment Site With Radiowave
Tomography Scattering Methods
U.S. Pat. No. 05474261
Dec. 12, 1995
Ice Detection Apparatus For
Transportation Safety
U.S. Pat. No. 05686841
Nov. 11, 1997
Apparatus And Method For The Detection
And Measurement Of Liquid Water And Ice
Layers On The Surfaces Of Solid
Materials
U.S. Pat. No. 05769503
June 23, 1998
Method And Apparatus For A Rotating
Cutting Drum Or Arm Mounted With Paired
Opposite Circular Polarity Antennas And
Resonant Microstrip Patch Transceiver
For Measuring Coal, Trona And Potash
Layers Forward, Side And Around A
Continuous Mining Machine
USRE032563
Dec. 15, 1987
Continuous Wave Medium Frequency Signal
Transmission Survey Procedure For
Imaging Structure In Coal Seams
USRE033458
Nov. 27, 1990
Method For Constructing Vertical Images
Of Anomalies In Geological Formations
SUMMARY OF THE PRESENT INVENTION
Briefly, a coal mining method embodiment of the present invention begins by using directional drilling to bore several horizontal shafts through a coal deposit with its natural overburden still intact. Any methane gas permeating the coal deposit is pumped out and preferably sold as natural gas to commercial and residential customers, or used locally in support of mining operations. The methane gas evacuation continues until the concentrations are reduced to safe levels for mining. But before mining begins, ground penetrating radar equipment is lowered into the boreholes for electronic imaging studies of the coal deposit. One borehole is used for a transmitter and another for a receiver. Many measurements are made at a variety of frequencies and equipment positions within the boreholes. Such studies estimate the electrical conductivity of the surrounding material, and thereby give clues where and how much coal is actually deposited. More accurate assessments of the coal reserve can then be developed from this information, and the results can be used with much higher confidence than the traditional reserve estimates obtained with conventional methods. The better numbers are preferably used to dictate business planning.
An advantage of the present invention is that a coalbed is first harvested for its methane through a system of boreholes, then the boreholes give access to ground penetrating radar and imaging equipment.
Another advantage of the present invention is
Bagnell David
Main Richard B.
Stephenson Daniel P
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