Abstract

Development of heavy oil resources is rapidly expanding the use of thermal enhanced recovery operations in Kern County, California, resulting in rapidly increasing demand for steam cogeneration facilities. One cogeneration by-product is a wastewater which must be disposed of in accordance with State and Federal regulations. Currently, two methods of wastewater disposal are available under California regulations, surface impoundments and injection wells.

Cogeneration wastewaters are “designated wastes” under California regulations. The quality of the vast majority of cogeneration wastewaters is such that surface disposal is required to be into Class II surface impoundments. These impoundments require a double clay liner, vadose zone monitoring, ground water monitoring and a thorough geologic evaluation. The overall costs can be comparatively high. Surface impoundments are permitted and regulated through the California Regional Water Quality Control Board.

Injection wells are a cost effective alternative to surface impoundments. Under current Underground Injection Control Program (UIC) regulations, cogeneration wastewaters from Thermal Enhanced Oil Recovery projects may be disposed in Class II injection wells. The California Division of Oil and Gas permits and overseas the mechanical integrity of Class II injection wells. The includes: an engineering study of the proposed project; a geologic study which demonstrates the project geology, a competent confining zone, injection zone characteristics, formation water analysis, and evaluation of pressure and waste fronts within the area of influence; and an injection plan of the wastewater treatment and injection facilities, the latter being most common in California. Three agencies may be involved in issuing permits for the operation of a Class V injection wells. The California Division of Oil and Gas permits and oversees the mechanical integrity of Class II injection wells. The detailed information required for a permit includes: an engineering study of the proposed project; a geologic study which demonstrates the project geology, a competent confining zone, injection zone characteristics, formation water analysis, and evaluation of pressure and waste fronts within the area of influence; and an injection plan of the wastewater treatment and injection facilities.