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.
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.
Petroleum Communication Foundation. Our Petroleum Challenge: Exploring Canada's Oil and Gas Industry, Sixth Edition. Calgary: Petroleum Communication Foundation, 1999. With permission from the Centre for Energy.