Results from previous drilling provide important information for explorationists. When a well is drilled, small rock chips called cuttings are recovered from the drilling fluid. These are ground up and broken off by the drill bit as it cuts into the earth. Geologists, geochemists and palynologists - scientists who study pollen and small fossils - examine the cuttings to learn more about the age, chemistry, porosity, permeability and other properties of the subsurface rock formations.
Larger, more continuous cylindrical rock samples, called cores, can also be cut using a special coring bit. Although coring adds to the cost of the well, laboratory analysis and visual examination of the core provide additional important details about the basin's history, the composition and physical characteristics of the rock and any fluids within it.
Even if a well fails to encounter oil or gas in commercial quantities, it still provides valuable information about underground rocks and structures. This may allow explorationists to generate new prospects or to match up certain seismic patterns with corresponding rock formations, which can lead to success with the next well - or the one after that.
