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All of the Great Lakes with the exception of Lake Superior are underlain by Paleozoic sediments and can be considered drillable with the various types of equipment illustrated. However, Lake Ontario being underlain by a veneer of essentially Ordovician and Cambrian rocks only, is less attractive explorationwise.
An arbitrary 108-foot maximum (18 fathoms) is set as the practicable depth of water which could be handled by the types of equipment presently in use, beyond which companies would have to resort to floating drilling vessels or to more elaborate and expensive drilling towers.
Lake Erie and Lake St. Clair have so far been the center of off-shore drilling activity in the Great Lakes
region, with Lake Huron now on the verge of exploitation. Offshore development in Lake Erie has been concentrated in two main areas: in the east and under-lake extensions of the Clinton-Medina gas fields are being proven; in the west end further biostromic Guelph gas-bearing reefs and extensions, as well as dolomitized Trenton oil and gas production are being sought.
Operating problems may be summarized as follows: relatively high costs of offshore contract drilling, short operating season (6-7 months), weather, disappointing results to-date of drilling based on geophysical surveys (seismic, gravity, magnetic, sparker), and attempts by the fishing industry and by champions of possible lake-pollution to prevent lake-drilling. Also the economics of offshore oil production are an unknown factor which will have to be determined by the type of production encountered.
The favorable marketing conditions in the heavily populated areas surrounding the Great Lakes provide ample incentive for offshore exploratory work. However, because of the problems mentioned, one of the main keys to a profitable natural gas operation has been to minimize drilling development and production costs. Some companies have accomplished this by operating their own offshore towers and by sub-contracting the actual drilling operations.
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