GEOSCIENCE ASSOCIATES AUSTRALIA HISTORY
GEOSCIENCE ASSOCIATES began operations as a small geophysical contractor, doing seismic work, in the USA in 1961. A couple of years later, Geoscience put together the first logging unit, to work in Uranium exploration. The 1960’s saw a great deal of expansion and development in the GA logging systems, with GA growing and moving to other countries. In 1971, GA opened it’s first workshop in Australia, as a well logging contractor to the minerals industry. The basic logging suites were analogue and tailored for the uranium search. As the Australian Company grew, so did the needs of our clients. Requests and demands for new services, both down-hole and on the surface, pushed us into the quest for better calibration - quicker data acquisition, and manipulation - exotic down-hole tools and uniform log presentations to name just a few.
In 1977, Geoscience ( now totally Australian owned ) initiated a Research and Development section. This section was charged with the task of searching, creating and maintaining the latest in logging technology. The section was to further develop and integrate these changes into the Geoscience logging systems. The R and D section has done this job well, and has provided Geoscience with several generations of logging devices. New technology, along with an emphasis on customer service has been GEOSCIENCE’S main strengths as a service contractor.
In 1983, Geoscience moved into new premises in Mt Barker with expansion into manufacturing and marketing the equipment on an international basis.
TRADITIONAL LOGGING METHODS
Historically, the techniques for measuring electric logging parameters and processing them have been “analog” in nature. Each parameter used in processing the curves was obtained down hole, conditioned to a suitable form, and sent to the surface over a wire or pair of wires.
The number of parameters, which can be sent to the surface at one time, is limited by the number of wires available. Since there are usually many parameters required to generate a suite of curves ( logs ), the hole had to be logged several times. Surface equipment used in this scheme was also analog in design. This equipment used analog filters, analog amplifiers, analog attenuators etc., to form a type of ‘analog computer’. This ‘computer’ processed the data, then related it to a chart recorder which drew the curves and was depth driven by some analog technique. Notations and any quality control was left up to the operator.
If more parameters were required, the above was repeated with the the different Sondes and different processors. Remembering that the analogue chart was the only permanent record, and to change any parameter, the hole had to be relogged.
MODERN LOGGING METHODS
Modern logging equipment, on the market today, has some form of digital processing included. Although the parameters are digitized, and are usually processed digitally on the surface, they may still use analog methods of transferring the information from the down hole Sonde.
Some systems digitize down hole and transmit the parameter data to the surface, via the logging cable, using some modern telemetry system.
DOWNHOLE LOGGING HISTORY
Geophysical borehole logging apparently began in 1869 when Lord Kelvin, of temperature fame, logged a water well with a temperature tool using a platinum resistance thermometer circuit.
In 1921 Marcel Schlumberger had logged a borehole to determine the in-situ resistivity of the formation in the Beseges coal basin near Molieressur-Ceze. This hole was 2500 feet deep and was cased to 1500 feet. Between March 20 and 22 several resistivity measurements over a few feet, at the bottom, of the hole did reflect the variations in the nature of the formations. Borehole geophysics remained an academic study until the Schlumberger brothers, Marcel and Conrad, started in the business of open hole geophysical logging for oil exploration in 1927.