A Note on Migration of Hydrocarbon Into Oil Shale Related to Tectonics, New Brunswick, Canada

Abstract

Oil shale samples of the 300-500 meter thick Carboniferous Frederick Brook Member of the Albert Formation, New Brunswick, Canada, were examined using reflected white and fluorescence light microscopy and Rock-Eval pyrolysis. The oil shale examined in this study are immature to marginally mature. Presence of bitumen within some of the immature oil shale samples is an enigma and indicates that bitumen must have are migrated into the oil shale possibly during and also after their deposition. The oil shale were deposited within a rift-lake system, where syn- and post-depositional faults likely provided conduits for migration of hydrocarbons from oil shale of the Albert Formation that was buried sufficiently deep to experience thermal stress necessary to generated liquid hydrocarbon towards the shallower immature oil shale deposits examined. Organic petrological evidence for hydrocarbon migration includes the presence of bitumen and crystalline carbonate in contact with oil shale. The low permeability oil shale acted as seal/aquatard and created a diagenetic front stopping the advance of some migrating fluids, such as brines and bitumen, resulting in formation of a reaction zone. Oil droplets are found in the reaction zone that has migrated away from the zone through the oil shale. The migrated bitumen found in the oil shales consists of Naphthene rich asphalt, which is none fluorescent and insoluble in CS2 and asphaltene-rich asphalt, which is fluorescing and is soluble in CS2. There are also fragment of light brown fluorescing bitumen in immature oil shale and oil droplet as fluid inclusions within the carbonate matrix, indicating oil migration and entrapment within these early diagenetic carbonate cements shortly after deposition of the oil shales.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016