Drilling Fluids and Reserve Pit Toxicity

Abstract

Drilling fluids are now classified as exempt under the Resource Conservation and Recovery Act (RCRA) hazardous waste laws. Since 1986, however, the U.S. Environmental Protection Agency (EPA) has been studying reserve pit contents to determine whether oilfield wastes should continue under this exemption. Concerns regarding reserve pit contents and disposal practices have resulted in state and local governmental regulations that limit traditional methods of construction, closure, and disposal of reserve pit sludge and water. A great deal of attention and study has been focused on drilling fluids that eventually reside in reserve pits. In-house studies show that waste from water-based drilling fluids plays a limited role (if any) in possible hazards associated with reserve pits. Reserve pit water samples and pit sludge was analyzed and collated. Analyses show that water-soluble heavy metals (Cr, Pb, Zn and Mn) in reserve pits are generally undetectable or, if found in the total analysis, are usually bound to clays or organics too tightly to exceed the limitations as determined by the EPA toxicity leachate test. The authors' experience is that most contamination associated with reserve pits involves high salt content from produced waters and/or salt formations, lead contamination from pipe dope, or poorly designedmore » pits, which could allow washouts into surface waters or seepage into groundwater sources. The authors' analyses show that reserve its associated with water-based drilling fluid operations should not be classified as hazardous; however, careful attention attention should be paid to reserve pit construction and closure to help avoid any adverse environmental impact.« less