The characteristics of oils in the subsurface as well as the hydrocarbon filling history of the Fry Field and the Rind Discovery, blocks 25/5 and 25/2 Norwegian North Sea, were studied using geologic, organic geochemical, fluid inclusion, and pressure, volume, and temperature (PVT) data. Geochemical signatures of present and paleopetroleum distributions in combination with microthermometry of fluid inclusions are integrated in this study with burial history modeling to understand the filling history of these structures and the timing of the main petroleum system events. Oils from the Rind Discovery are significantly different from the fluids encountered in Fry Field, indicating that these structures received oil from different kitchen areas. In the Rind Discovery, migration of oil between the main southern compartment and the presently dry and overpressured adjacent northern compartment was timed relatively, based on the maturity differences in the bitumen from these two structures, as well as using fluid inclusion data. Sealing of the fault between these two compartments, caused by fault movement and/or diagenesis, disrupted communication, and the caprock failed because of pressure buildup in the presently dry northern structure. The oil charge in the main structure was preserved from pressure buildup because of communication updip. The difference in the homogenization temperatures of the petroleum and aqueous inclusions from these two compartments was used in combination with their burial histories, to bracket the time for overpressure buildup and leakage.

Within the Fry Field, geochemical analyses indicated that most of the oils encountered belonged to one uniform population, a conclusion supported by the PVT data. However, one of the compartments contained slightly biodegraded oil that was entirely different from the oil in the rest of the field. This biodegraded oil is believed to be sourced from Dunlin Group shales, and the presence of this oil in this isolated compartment indicates a lack of communication with the main reservoir strata of the Fry Field. Maturity differences between the oils sampled from the Fry indicated that the most mature oils are encountered at the crest of the reservoir and oils of decreasing maturity occur toward the flanks, suggesting that this trap was filled in the usual top- and down-flank style. Using the burial history of the Fry Field, we determined that the filling of the subcompartment holding the biodegraded oil must have occurred at about 40 Ma, before oil from the Late Jurassic Draupne shales more homogeneously filled the main Fry structure. The integration of the geochemical data obtained from the Rind Discovery and the Fry Field with 1-D basin modeling of both the reservoir and kitchen areas allowed the timing of the main petroleum system events to be constrained, namely, the generation, migration, emplacement, and leakage of hydrocarbons in the study area.