Abstract: Volumetric compositional balance of generated and entrapped petroleum compounds on the Franklin field (North Sea)

GAULIER, M.; J.M. VANDENBROUCKE; F. BEHAR; J.L RUDKIEWICZ; S. DROUET; F. BRIGAUD; S. DUPPENBECKER; A. VEAR

The Franklin field in the North Sea exhibits high temperature and high pressure that induced an unconventional charge history. During an EU supported Thermie project, we investigated the formation and thermal stability of petroleum compounds in this field. Based on seismic data, a 3D data set described the petroleum system. Through combined decompaction and maturity modeling of the Kimmeridge source rock, the timing of structuration and the change in trap size resulted in volume estimations of the generated and trapped hydrocarbons.

The geochemical studies of the oils and the typing of the source rock indicated marine type II organic source. Kerogen cracks to: methane (C1), wet gas (C2-C5), light saturates (C6-C14SAT), light aromatics (C6-C14ARO), heavy saturates (C15+SAT), heavy aromatics (C15+ARO) and NSO compounds (C15+NSO). The calculated volume of each class generated by the source rock has been compared to actual observations in the reservoir.

We correctly estimated the light hydrocarbons and the C15+SAT with discrepancies lower than 20%, in good agreement with predicted migration efficiency from laboratory measurements. C2-C5 is overestimated probably due to losses through the cap-rock of the reservoir. Methane is significantly underestimated, due to difficulty in estimating the amount of secondary cracking. C15+ARO and C15+NSO show a strong deficit: almost no NSO are found in the oil. This clearly indicates the importance of retention phenomena in the source rock, losses along migration pathways and secondary cracking.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria