Prospecting for undiscovered petroleum. Any method used to discover new oil and gas fields. Five different elements need to be present for an accumulation to work and if any of these elements are absent then we get a dry hole: (1) structure/trap – a geological feature which is defined using seismic, in which hydrocarbons may be trapped; (2) reservoir – a porous rock which can contain hydrocarbons and from which hydrocarbons can flow into an oil/gas well; (3) seal – an impermeable formation located above the reservoir, which prevents the hydrocarbons from escaping; (4) source – a rock containing the precursors of hydrocarbons which can then be turned into oil or gas by thermal maturation, (5) migration – the process by which hydrocarbons move between source and reservoir. Estimating the probability of all these elements is a key part of exploration.