The discharge of produced water into surface waters has been regulated since the late 1960's. The regulations prohibit discharge of any water that would cause permanent harm to the environment and sets limits on waters that are discharged based on best available technology for removing regulated contaminants. The United States is subdivided into categories under United States Environmental Protection Agency (EPA) regulations. Discharge limits in the subcategories range from no discharge to surface waters to discharges limited by toxicity and oil content. Discharge limits are determined by available technology for controlling toxicity and oil and grease.
This paper reviews the development of the guidelines and limits on produced water discharges and the technology to meet the regulatory limits for each category. It also discusses the problem of new exploration areas that might not fit into a one of the existing categories. As the exploration production industry advances, it is moving into areas such as very deep water that may have different technology constraints than those addressed by past regulations. Currently each subcategory has limits determined by technology appropriate to that subcategory. If future exploration areas do not fit into a recognized category, what should be done? For example, in very deep water, is a new subcategory needed with limits appropriate to water treating technology that can be economically applied in that environment?
The cost of meeting environmental regulations on the disposal of produced water is a significant portion of the lifting costs in producing oil. This is especially so in offshore waters, and consequently is a very important factor in determining the economics of oil production. When United States offshore production began in the late 1950s there were no uniform regulatory limits on the disposal of produced water offshore. Until the early 1960s the disposal of produced water was regulated by local and state authorities. The limits were established to address obvious impacts. For example, salty produced water was not discharged on cropland because it prevented plant growth. Over a period of time a well defined set of regulations has been developed setting limits on the discharge of produced water to surface waters. These regulations addressed production areas that existed at the time. Now that exploration and development of very deep waters is underway it is imperative that existing regulations be examined to see if they are still appropriate or even achievable in these new frontier areas.
The United States Environmental Protection Agency (EPA) recognized that the potential impact of the discharges varied depending on the nature of the effluent and the location of the facility. Consequently, the EPA developed the present regulatory system tp address the specific requirements of these subcategories. The subcategories include:
The onshore subcategory
The stripper well subcategory
The "beneficial use" subcategory
The coastal subcategory
The territorial seas subcategory, and
The outer continental shelf subcategory.