Accumulation and removal of world's largest hydrocarbon resources with changing hydrology and climate in the Cenozoic

Hydrocarbon resources form from organic matter at moderate temperatures in sedimentary basins, under favorable conditions of migration and accumulation. This short communication examines how the global distribution of large hydrocarbon resources is influenced by long term solution and dissolution resulting from changes in climatic conditions. Laboratory experiments on water washing showed that water solubility of gas and light oil increases with temperature and decreases with salt content. Thus, water can transport hydrocarbons over large distances in the seaward direction, if stratigraphy and tectonic setting provide suitable aquifers, and if salinity is low. If salinity rises, for example due to high evaporation rates or contact with salt deposits or seawater, gas and light oil drop out of solution. This assumed water washing mechanism cannot act in areas with no or low water flow rates, such as arid or arctic regions, where hydrocarbons are not transported but remain in situ. Hydrocarbons accumulate under four major hydrological and climatic regimes. a) In deltas, or offshore areas next to outlets of great rivers. b) Offshore in humid and hot climate next to mountain ranges. c) Onshore in arid or semi-arid climate, and. d) Onshore in arctic regions. Climate changes in the Cenozoic severely affected the formation of hydrocarbon resources, due to alternations in temperature, precipitation and the hydrogeological cycle. The occurrence of permafrost is also relevant, as it prevents meteoric water from infiltrating and decomposing hydrocarbon accumulations by water washing at high latitudes. Recent natural phenomena show that present global warming threatens at least nine large hydrocarbon provinces in arctic regions already, as permafrost decomposes or ice sheets melt, becoming unable to act as seal for gas or light oil below any longer or as aquiclude, respectively.