Regulatory Aspects of Waste Disposal Using Controls And Slurry Fracture Injection

Abstract

Abstract The Canadian oil industry has been disposing solid wastes using Slurry Fracture Injection ™ (SFI ™) for five years. Projects in Saskatchewan and Alberta have provided a good experience base, and a regulatory framework is evolving. This article addresses technological and regulatory aspects necessary for the safe operation of SFI ™. Regulatory agencies involved in permitting SFI ™ of nonhazardous oilfield wastes must assure that there are no long-term effects related to potable water contamination or degradation, surface land use impairment, or loss of current or potential natural resources. To achieve these goals, a flexible yet appropriate set of guidelines is needed to guarantee that applicants have carried out appropriate site, formation, well, and SFI ™ process operations planning before a permit is issued. Thereafter, the major regulatory tasks are to maintain audit control of waste volumes, enforce a minimum monitoring level which will demonstrate waste containment in the target zone, assure that nearby resources are secure, and confirm that only permitted wastes are being injected. The regulatory agency should ensure project compliance through audits and random checks. Introduction Slurry Fracture Injection (SFI ™) projects have been permitted in Alberta and Saskatchewan to dispose of oily sand, tank bottoms ("slops"), and produced or waste water. The technology is now widely understood and a regulatory framework is evolving in Alberta that allows SFI ™ projects to proceed in an environmentally secure manner. To understand the need for regulatory control and enforcement, it is necessary to understand the basic technological aspects of SFI ™, the arguments for its environmental security, and the industry's capabilities in monitoring and analysis. This article will address these issues and make specific recommendations. Oilfield Waste Streams Large volumes of non-Dangerous Oilfield Wastes (non-DOW) are produced during exploration, drilling, production, and refining. Table 1 describes some typical non-DOW streams. Refinery wastes may have high levels of metals and other compounds which may result in a hazardous classification. The largest volume non-DOW stream in the Canadian oil industry is produced water and sand from Cold Heavy Oil Production (CHOP)(1). Most produced water is filtered and injected into disposal formations at pressures below the natural fracture pressure. CHOP involves letting reservoir sand enter the wellbore during heavy oil production to increase production efficiency(1–3) The sand settles to the bottom of on-site stock tanks that are periodically cleaned, and sand is transported to the disposal facilities. On average, produced sand is perhaps 2 – 3% of the total volume of heavy oil produced during CHOP, but can vary from a fraction of 1% to more than 10%. In Canada, sand production estimates were ∼300,000 m3 for 1997, and this number will grow as heavy oil production increases. For a single company producing between 20,000 and 50,000 m3/yr of sand, at least six to 12 months per year of dedicated SFI ™ operation is needed for disposal. Also, on the order of 80,000 – 400,000 m3 of waste (produced) water will be co-disposed with these sand volumes.