Petroleum geology refers to the specific set of geological disciplines that are applied to the search for hydrocarbons (oil exploration).
Petroleum geology is principally concerned with the evaluation of seven key elements in sedimentary basins: Source, reservoir, seal, trap, timing, maturation and migration.
In general, all these elements must be assessed via a limited 'window' into the subsurface world, provided by one (or possibly more) exploration wells.
These wells present only a 1-dimensional segment through the Earth and the skill of inferring 3-dimensional characteristics from them is one of the most fundamental in petroleum geology.
Recently, the availability of cheap and high quality 3D seismic data (from reflection seismology) has greatly aided the accuracy of such interpretation.