The earth's crust is composed of sediments and rock, which may be either porous or non/porous. Reservoirs of oil and gas are usually found in porous rocks. Salt water, which occurs with the oil and gas in the reservoir, is typically produced along with the oil and gas. The salt water, or produced water, may be returned by fluid injection into the reservoir from which it originated for secondary and enhanced recovery operations, but also may be disposed of into porous rocks not productive of oil or gas. There are currently approximately 52,000 injection/disposal wells in Texas that are permitted by the Railroad Commission to be used in association with oil and gas production operations.
The ideal fluid injection or disposal well is one using a porous zone of relatively low or moderate pressures that is sealed above and below by unbroken impermeable strata. The injection interval must be permeable and of sufficient thickness and lateral dimensions to contain the volume of fluid to be injected without the injection pressure increasing to the point that it will fracture the sealing layers of rock. Fluid injection and disposal wells must be designed and operated to perform the specific job for which they are intended, which is to confine the injected fluids to the injection interval and to protect fresh water resources. Fresh water is one natural resource without which life cannot be sustained.
The objective of the Railroad Commission's Injection-Storage Permits and Support Program is to ensure that our surface and subsurface fresh water is free of pollution or contamination that could result from unsound installations and operations. Proper well completion, injection procedures, and monitoring will ensure that fresh water sources will be available for generations to come