 Everywhere you go, in the city or the country, rock beds are beneath you for thousands of feet. Deep in the beds, heat and pressure turn decaying plants and animals into oil and gas. The oil and gas migrate through porous rocks until they're trapped by impermeable rock barriers. Geologists look for the traps. Exploration companies drill wells into them, searching for oil and gas. Before drilling can begin, division engineers must approve the drilling plans. The plans include the protection of surface and underground environments. During drilling, heavy drilling mud is circulated into the well to control underground pressures. Blowout prevention equipment installed on every wellhead acts as a backup pressure control system. With it, a well can be shut in at any time. Division engineers specify the blowout prevention equipment used on each well. They witness tests to ensure the equipment is in operating order. Good well control training and widespread use of blowout prevention equipment have made California blowouts rare. About 68,000 oil and gas wells were drilled in the state from 1954 through 1980. Only 31 blowouts occurred during this time, with little environmental damage. Drilling oil wells in an urban area is a safe but sometimes noisy task. Therefore, drilling rigs are especially designed to muffle sound. At more permanent locations, drill sites are built to blend in with other structures in the area. About 26 wells will be drilled from this San Fernando Valley site. 77 wells have been drilled from inside this yellow building in Los Angeles. Derricks on this landscape drilling island in Long Beach Harbor have been mistaken for apartment buildings. Most oil and gas wells are drilled through water zones. Fluids from oil, gas and water zones must not mix. To prevent this during drilling, heavy mud is pumped into the well bore. These zones are sealed when sections of pipe called casing are cemented in the hole. Cement is pumped down the well through the casing, out beneath it, and back to the surface. To check the cement seal, operators may be required to conduct a water shut-off test witnessed by a division engineer. The casing is perforated through productive oil and gas zones. Depending on reservoir type and pressure, different kinds of production equipment are installed. The amount of oil and gas produced from every well is reported to the division each month. Sometimes, sumps are dug on oil and gas leases. The sumps, open depressions holding oil and water, can be dangerous to wildlife. Twelve years ago, the division began to locate and classify California oil field sumps. Today, all of the hazardous sumps have been screened or eliminated. Good housekeeping is encouraged at all oil and gas leases. This makes leases more attractive, safer, and environmentally acceptable. Each year, recipients are chosen for a lease award. Dry holes and wells no longer commercially productive are abandoned. To abandon a well, cement is placed across all oil zones. Freshwater, saltwater contact zones and at the surface. The rest of the well is filled with heavy drilling mud. Before 1915, many California wells were abandoned incorrectly. Today, when these wells are found, they are properly abandoned. Money from a special fund may be used for the work. The division of oil and gas protects California's oil, gas and geothermal resources. It encourages the wise development of these natural resources through good conservation and engineering practices.