Boots – shoes – and leggings
Patent
1989-01-19
1992-05-05
Hayes, Gail O.
Boots, shoes, and leggings
367 42, G01V 136
Patent
active
051113996
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a seismic processing apparatus and in particular to a portable apparatus capable of carrying out real time processing of data during acquisition and subsequent reprocessing of acquired data.
BACKGROUND OF THE INVENTION
The exploration for hydrocarbons and minerals at present is becoming of widespread importance, as the earth's resources are being consumed at an alarming rate. The seismic exploration method has proved very successful over the last 65 years for locating hydrocarbons. Today there is a great demand to adapt these techniques to the search for minerals, which places greater demands on the processing of data.
The basic principle of seismic exploration consists of transmitting a sound wave through the earth's rock structures and picking up reflected and/or refracted waves. Analysing the properties of these sound waves yields information about the earth's geological features. These features, together with samples taken from exploratory bore holes, enable the geologist to determine the position and extent of hydrocarbon and mineral deposits.
In land exploration, a large number of geophones are spaced apart along a line extending over many kilometers, in either one or both directions, from a sound source. In a typical land data acquisition arrangement, the geophones are each connected to a recording truck via independent channels, which may consist of multiconductor cables carrying analogue signals, or a single cable carrying a digital multiplexed signal from each geophone. At the recording truck the signals from each geophone channel are connected to a switching device which selects which channels are to be recorded. The sound source e.g. an explosive charge, is moved along the line at fixed intervals of distance, and the geophone channels selected for recording are those in the proximity of this sound source. At each interval or "shot point" a recording is made and in this manner data is acquired while moving along the exploration line.
In marine exploration the reflected and refracted sound waves are detected using a hydrophone streamer which is towed in a straight line behind a survey ship. The streamer consists of a number of sections, each containing a hydrophone (or group of hydrophones), and are linked to the recording equipment via independent channels. The ship moves along the exploration line towing the sound source, which produces a sound wave at fixed intervals of distance. The sound wave passes through the water into the earth's surface and the reflected and refracted waves are detected by the hydrophone streamer and recorded. In this manner data is acquired while the survey ship moves along the exploration line.
At present, digital recording is used almost exclusively in seismic exploration. This gives a large dynamic range, and signal processing techniques can be applied to the data directly using digital computers. Typical recording equipment used at present has a capacity of up to 120 channels, sampling rates in the range 0.25 to 4 milliseconds, and a dynamic range of 84 dB. The analogue-to-digital conversion generally consists of 14 bits for the magnitude, one bit for the sign and three bits to represent the gain applied to the amplifier during conversion. Data from each geophone is sampled sequentially, digitised and placed onto tape (i.e. in a multiplexed form).
As sound sources, explosives are used extensively for both land and marine exploration, but are now beginning to be replaced by other sources. For example, a weight drop method is often used in land exploration, in which a weight is dropped from a predetermined height onto the ground to produce the sound wave. The weight can be dropped many times at a particular location, and the reflected seismic signals detected by the geophones for each drop can be added to increase the signal amplitude. A method called vibroseis is frequently used for land exploration in which a mass in contact with the ground is made to vibrate with a frequency that is continuously changed or swept
REFERENCES:
patent: 4630242 (1986-12-01), Done
patent: 4744064 (1988-05-01), Hughes
"Seismic Signal Processing via ILLIAC IV Computer", Gary Ackins et al, IEEE Trans. on Geoscience Elec., vol. GE-7, No. 1, Jan. 1961, pp. 34-41.
Mini-Micro Conf. Record, Nov. 1983, P. Cavill, "Transputer Systems", pp. 1-6.
AFIPS Conference Proceedings, 5-8, Jun. 1978, "Present and Future".
Peter Ekelmann, "Transputer: Mikrorechner-Konzept fur hohe Verarbeitungsleistung", Elektronic, vol. 32 (1983).
Peter Cavill, "Transputer Systems", Mini-Micro Conference Record (1983), Nov. 8-11, San Francisco, CA U.S.A.
Gordon David P.
Hayes Gail O.
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