Study of hydrocarbon migration events: Development and application of new methods for constraining the time of migration and an assessment of rock-fluid interactions. Final report, September 9, 1993--August 31, 1996

摘要

The primary objective of this project was to test and refine a paleomagnetic method to date hydrocarbon migration. As the research progressed, goals were broadened to address whether paleomagnetic methods could also be used to constrain the time of hydrocarbon generation resulting from the thermal alteration of organic matter. Alternative models such as the potential role of orogenic fluids with respect to the precipitation of authigenic magnetite have also been assessed. Numerous field tests of the paleomagnetic dating method and laboratory simulation experiments to elucidate the mechanisms for magnetite precipitation have been conducted, with significant progress being made in both areas. With respect to migration, two field tests have been performed. The first consists of calcite veins impregnated with hydrocarbons in the Devonian Old Red Sandstone, which contain a late Paleozoic chemical remanent magnetization (CRM) that resides in magnetite. The CRM dates the time of hydrocarbon migration into the veins. The second test concerns calcite veins impregnated with hydrocarbons that occur in a fault zone in Jurassic, organic-rich limestones in England. These veins contain a Cretaceous/early Tertiary age CRM residing in magnetite that reflects the time of hydrocarbon/radiogenic fluid migration into the veins. With respect to the thermal maturation of organic matter, the authors found that lacustrine, organic-rich beds in the Old Red Sandstone in Scotland contain a CRM in magnetite that does not appear to be related to fluids, but rather to in situ maturation of the organic matter. The results of these field tests and simulation experiments are encouraging and indicate that both hydrocarbon migration and organic matter maturation may result in magnetite authigenesis.