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Palaeomagnetic Properties of Hydrocarbon Reservoirs |
CB-Magneto A/S, PO Box 7015, Jorenholmen, N-4004 Stavanger, Norway
Cores from wells 34/10–16 and 34/10–17 in the Tampen Spur area, Norway were studied to establish a magnetic polarity stratigraphy for the Brent Group in the area. Approximately 100 samples from each well were treated by traditional thermal and alternating field demagnetization procedures and the apparent polarities determined. Thin sections were studied and scanning electron microscopy carried out with the purpose of verifying a primary origin of the remanent magnetization.
Correlation of the two wells based on the polarity logs was in agreement with the lithoand biostratigraphic correlations. However, the mineralogical analysis did not determine any primary magnetic minerals, although potential remanence carrying diagenetic minerals were observed. This, combined with magnetic data indicating extensive remagnetization of the sediment, lead to the conclusion that the remanent magnetization of these sediments is late diagenetic, probably of Tertiary age.
The results are not encouraging with respect to the use of palaeomagnetism as a chronostratigraphic tool for these sediments. It may, however, be useful for dating diagenetic events and, as a result of the strong secondary magnetization, magnetic orientation techniques can be successfully applied to the core material.
