Thermo-Tectonic Evolution and Numerical Petroleum System Modeling of One of the Oil Fields on Krasnoleninsky Arch, SW West Siberian Basin

Abstract

Abstract In the West Siberian Basin, thermal maturity anomalies correlate with heterogeneities in the basement and are presumably caused by localized hydrothermal activity. NE and SE oriented faults potentially served as vents for hydrothermal fluids and provided migration pathways for large oil fields. An example oil field located upon the Krasnoleninsky Arch in the southwestern West Siberian Basin was investigated to understand the timing and interplay of the petroleum system elements including the activity of faults. Three boreholes and two seismic sections were used to build 1D and 2D petroleum system models. Detailed boundary conditions were defined and thermal modeling was performed by matching calculated values to calibration data. Different scenarios of opened/closed faults were tested to determine the history of oil migration. Good calibration with basal heat flow was achieved from initially 95 mW/m2 in the Triassic and slowly decreasing to values between 60 and 70 mW/m2 until today. Modelled present-day surface heat flow varies between 70 and 78 mW/m2. While subsidence is rather continuous from the Early Cretaceous until the Late Eocene, the Lower Cretaceous stands out. This dynamic epoch exhibits fluctuating sedimentation rates and tectonic uplift, which resulted in surface exposure and in local erosional unconformities. NE and SE directed basement lineaments were reactivated mainly as strike-slip faults during the Barremian and the Aptian. Late Jurassic oil-prone source rocks reached depths between 2,300 and 2,500 m and maximum temperature of 120 to 130 °C. Ro varies around 0.9 % and transformation ratios yield 55 to 75 %. Two peaks of petroleum generation were identified during the Barremian (ca. 120 Ma) and the Campanian (ca. 80 Ma). Since about 600 m of low-permeable rock separate the source rocks and the overlying reservoir rocks, we conclude that both pulses required open faults for successful migration and charge of our example oil field.