Quick mapping of basin modelling results—a key for quantifying prospect sensitivities

Abstract

Many critical geological factors of exploration prospect evaluation can be studied using standard 1D and 2D basin modelling programs. To investigate basin modelling results spatially in prospective areas, mapping routines are attractive methods, especially where input data are too sparse to perform full 3D basin modelling. Norsk Hydro's QuickVol3D applies a new mapping method for basin modelling results such as temperature and maturity parameters. The program is highly flexible and can handle different amounts of available input data. The minimum requirement for the application of QuickVol3D is at least one depth-converted map of the top source rock horizon and results from at least one basin modelling study (1D or 2D). QuickVol3D is being used to study particularly the hydrocarbon generation and expulsion in exploration prospect areas. The hydrocarbon expulsion model employed in QuickVol3D is based on the sorption of generated hydrocarbons. Once the amount of generated hydrocarbons overcomes the defined sorption capacity, all excess masses are regarded as being expelled. Therefore, hydrocarbon expulsion masses are calculated as a function of the source rock hydrocarbon generation kinetic, maturity, source rock richness (hydrogen index), initial content of organic matter, and the sorption capacity for oil and gas. This expulsion model reconstructs many observations more correctly than standard pore space saturation models, such as why poor source rocks might generate higher hydrocarbons (oil), but expel only light components (gas). Hydrocarbon expulsion in the drainage area of the Agat discovery, Norwegian North Sea, has been used as an example application of QuickVol3D. Calculated amounts of expelled hydrocarbons indicate that the undersaturated gas in the trap resulted from an early emplacement of gas and further burial without major contribution of additional oil volumes.