Yanzhe Fu

• Our research work focuses on the gas-condensate Kristin Field on the mid-Norwegian margin where Middle Jurassic sandstone reservoirs are currently subjected to High Pressure and High Temperature (HPHT) conditions. A high-resolution 3D seismic dataset was interpreted to derive structural trends and horizon geometries for a full 3D basin model. The chrono-and litho-stratigraphy of the seismic sequences were tied to wells. The calibrated heat flow simulation suggests a basal heat flow trend of 57mW/m2 during the Jurassic pre-rifting, increasing to 83mW/m2 at the end of the Jurassic rifting and decaying to a constant 53mW/m2 from the Miocene to present. The reconstructed hydrocarbon filling history shows that the Kristin traps were charged around 135Ma ago. The generated hydrocarbons could have migrated into the neighboring Smørbukk Field during the pre-Pliocene due to lateral fluid communications across the fault zones. The reconstruction of overpressure evolution and the comparison of different pressure generating processes demonstrate that only sedimentary compaction disequilibrium is not sufficient to explain the overpressure magnitudes observed in the Kristin system. Volumetric contributions from the generated gas must be taken into account. Overpressure modeling indicates that dramatic overpressure buildup in the Kristin reservoir is a recent event. It was mainly caused by secondary oil to gas cracking and closure of the fault zones both triggered by the rapid Pliocene-Pleistocene sedimentation in the area. The large volume of gas from secondary cracking may also have overprinted the geochemical signals of primary coal-gas. This work provides significant new insights into the evolution and dynamics of the overpressured Kristin system and contributes to the understanding of petroleum compositional evolution, overpressure buildup processes, and regional hydrocarbon migration patterns on the Halten Terrace through geological time.