How are wells drilled in California?
A well is made by drilling a hole called a wellbore, into the earth (watch a movie). Oil and gas wells can range in depth from a few hundred feet to over 20,000 feet. Metal pipe, called casing, is placed in the well-bore and cement is pumped down the casing. The cement pushes out around the bottom of the casing (watch a movie), and flows up the space between the wellbore and casing, back to the surface. When the cement hardens, it forms a bond between the walls of the wellbore and the outside of the casing. This bond protects groundwater, and oil and gas reservoirs, from contamination. Holes are then made in the casing opposite the reservoir, allowing oil and/or gas to move into the casing, and up to the surface where they are processed and transported to market.
