| dc.description.abstract | The use of petroleum inclusions in petroleum and reservoir geology is a relative new tool utilized to get a better understanding of petroleum generation and migration, paleo-fluid distribution in traps, and the organic facies and maturity of source rocks. Fluid inclusions are tiny quantities of liquid, vapour, or a mixture of these phases, trapped in mineral cement formed after deposition (diagenetically trapped in mineral cements). This study represents the first systematic attempt to study the C15+ fraction trapped in diagenetic inclusions and produced oils of various traps in the Haltenbanken Area, including selected samples from the following fields; Njord, Smørbukk, Smørbukk South, Lavrans, Tyrihans North and South, Trestakk and the 6407/4-1 discovery.
The oil and inclusion samples from the different fields show wide variation in maturity. A maturity trend within the inclusion samples was found to go from the least mature in the south-east to the most mature in the north-west, except from the 6407/4-1 trap, located in the south-east, but having high maturities. The oil samples showed a more uniform maturity and a specific trend was not observed. This probably reflects that the reservoired oils represent a more integrated maturity spectrum than do the inclusions. The Njord oil sample differs from the others, in showing high maturities within the medium range parameters, whilst low maturities are observed within the biomarker parameters. This is a result of mixing between a low maturity oil and higher maturity condensate, and was only observed in this sample.
Organic facies variations of petroleums within the fields, if found were small, but between the fields the inferred organic facies of the source rocks having generated the petroleums vary within the range from open marine, to more proximal and terrigeneous influenced depositional environments for the source rock. A trend was observed with higher terrestrial input to the source rock kerogen in the proximal east-western region, whereas in the more distal north-western regions the contributing kerogen is inferred to be more amorphous and deposited under more reducing conditions. It is believed that a marine type II rock is the source for the petroleum found in both inclusions and traps.
Thus, in general, the oil samples from the traps show the same facies signatures as the extracts from the petroleum inclusions, but at a higher maturity. This could correspond to a situation in which the inclusion have trapped paleo-petroleum generated when the source rock were shallower and expelling petroleum of lower maturity. | nor |