 California has over 11,000 injection wells. Why do we need them? What are they? How are they used? Are they safe? These are the answers we need to know. Producing oil and gas also means producing saltwater. This remnant of ancient seas often trapped in oil and gas reservoirs. The amount of saltwater produced each year from California oil and gas wells matches the fresh water needs of San Francisco. Disposing of the saltwater is a major concern. In the early days, most of the water was simply dumped at the surface. Today, safe disposal methods are used. For 40 years, much of the water has been returned underground through wells. These wells are called Class II injection wells. What is injected? Salt and fresh water produced from oil and gas wells, oil and gas traces left in the water, and sometimes about a 1% amount of materials used in oil and gas production projects. What else is injected? Nothing. These wells are tailor-made for saltwater. Other substances could ruin them, plus criminal and civil penalties are imposed for illegal injection. 10% of the wells are used for disposal alone. In about 90% of the wells, the injected water is used to produce oil, such as at this water flood well and this steam flood well. Here, the water or steam are injected back into the oil zones. They help to move the oil towards the oil wells. About 55% of California's oil is produced this way. Many types of rock beds lie beneath California. The more porous layers, like sandstone, often hold large amounts of liquid. The oil, gas and saltwater come from such beds. Finer grained layers, like shale, often cover the porous beds. They act as caprocks, locking in the liquids. For every proposed Class II well site, the rock beds are studied, especially the porous sandstone zones being considered for injection and the shale caprocks covering them. Class II injection occurs in sandstone zones, often at depths greater than 2,500 feet, far below the depths where most rinking water and irrigation water are found and underneath impermeable caprock. All injection zones are approved by the Environmental Protection Agency. When a well is drilled, steel pipe, called casing, is placed in the hole and cemented. The cement prevents fluids in other zones from mixing with each other or with injected fluids. The casing and cement are perforated in the injection zone. For extra protection, tubing is lowered into the well to a point just above the perforations. A packer is set near the bottom of the tubing as a seal. When injection begins, special tests are run to make sure the well is operating correctly. To ensure injection wells remain mechanically sound, annual tests are made for disposal and water flood wells and three-year tests for steam flood wells. What kinds of tests are run, spinner, tracer and temperature surveys? Test results and monthly well performance records are reviewed by engineers from the Department of Conservation's Division of Oil and Gas. Often fluid samples are taken. We make sure the equipment is in good condition and functioning properly. We check the well head injection pressure and see that no on-site materials damage the environment or present a safety hazard. Deficiencies are corrected. If any malfunction endangers fresh waters, injection is halted until the well is repaired. How do class 2 injection operations work? The oil and gas are separated from the salt water at the production well. For disposal projects, the salt water is trucked or piped to a disposal well. There, the water is transferred into holding tanks and injected into a nearby well. For injection projects used to produce oil and gas, such as those near Kalinga, the produced salt water is delivered to a central oil field site. Sometimes it's heated or turned to steam. Then it passes through a pipeline network and into the injection wells. The division regulates all class 2 injection wells in California. It enforces provisions of the public resources code and the Federal Safe Drinking Water Act. This injection program is also monitored by the Environmental Protection Agency. Each class 2 project is studied by the division and reviewed by the State Regional Water Quality Control Board. The division evaluates engineering and geological data, including chemical analyses of reservoir fluids. A request for public comments about the project is placed in local papers. A public hearing is held on request. If the division issues a permit, it will include many conditions, such as approved injection zones and pressures and testing requirements. Class 2 injection wells are a safe way to dispose of the salt water produced with oil and gas. In California, the wells have an outstanding safety record. They protect our underground and surface environment.