Overpressure generation and retention in source rocks; Salym analogue of secondary reservoirs, West Siberian Basin, Russia.

The build-up of pressure on conversion of kerogen to hydrocarbons is a widely recognized phenomenon in oil and gas generation. During kerogen transformation, hydrocarbon production is frequently accompanied by an increase in volume. The generation of hydrocarbons leads to higher pressures within the source rock causing the fluids to expel out of the source rocks and migrate upwards into shallow reservoirs. The capture of the fluid exodus along the migration pathways owing to pressure differences between over pressured source and reservoir rocks catalyzes hydrocarbon entrapment where favorable geological trapping conditions prevail. However, where such avenues are denied, the source rocks themselves become the site for hydrocarbon accumulation at overpressures. The source rocks of Salym field in West Siberian Basin are one such typical example of hydrocarbon generation, in situ pore pressure generation and retention. A geological model has been conceived to explain the mechanism involved based on P-T conditions of the reservoirs in Bazhenov and Achimov Formations and application of fundamental fracture mechanics. [ABSTRACT FROM AUTHOR]