Petroleum System Modeling of Northern Alaska
Oliver Schenk, Kenneth E. Peters, Leslie B. Magoon, Kenneth J. Bird, 2012. "Petroleum System Modeling of Northern Alaska", Basin Modeling: New Horizons in Research and Applications, Kenneth E. Peters, David J. Curry, Marek Kacewicz
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Northern Alaska is a prolific oil and gas province estimated to contain a sig-nificant proportion of the undiscovered oil and gas of the circum-Arctic. A three-dimensional petroleum system model was constructed with the aim of significantly improving the understanding of the generation, migration, accumulation, and loss of hydrocarbons in the region. This study provides a unique geologic perspective that will reduce exploration risk and assess the remaining potential hydrocarbon resources in this remote province.
The present-day geometry is based on newly interpreted seismic data and a database of more than 400 wells. A key aspect of this model is an improved reconstruction of the progradation of the time-transgressive Cretaceous–Tertiary Brookian sequence and multiple erosion events in the Tertiary. The deposition of these overburden rocks controlled the timing of hydrocarbon generation in underlying source rocks and their principal migration from the Colville Basin northward to the Barrow Arch. The model provides a reconstruction of the complex and dynamic interplay of diachronous de-position and erosion and allows assessment of variations in migration behavior and prediction of the present-day petroleum distribution.
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Temperature-time–based first-order kinetic models are currently used to predict hydrocarbon generation and maturation in basin modeling. Physical chemical theory, however, indicates that water pressure should exert significant control on the extent of these hydrocarbon generation and maturation reactions. We previously heated type II Kimmeridge Clay source rock in the range of 310 to 350°C at a water pressure of 500 bar to show that pressure retarded hydrocarbon generation. This study extended a previous study on hydrocarbon generation from the Kimmeridge Clay that investigated the effects of temperature in the range of 350 to 420°C at water pressures as much as 500 bar and for periods of 6, 12, and 24 hr. Although hydrocarbon generation reactions at temperatures of 420°C are controlled mostly by the high temperature, pressure is found to have a significant effect on the phase and the amounts of hydrocarbons generated.
In addition to hydrocarbon yields, this study also includes the effect of temperature, time, and pressure on maturation. Water pressure of 390 bar or higher retards the vitrinite reflectance by an average of ca. 0.3% Ro compared with the values obtained under low pressure hydrous conditions across the temperature range investigated. Temperature, pressure, and time all control the vitrinite reflectance. Therefore, models to predict hydrocarbon generation and maturation in geological basins must include pressure in the kinetic models used to predict the extent of these reactions.