Tar Sands Drilling Waste Management: A Clean Solution

Abstract

Tar sands are a combination of sand, clay, water and bitumen. In-situ techniques using steam and/or solvents are used to reduce the bitumen viscosity such that it can be recovered and refined into petroleum products. Steam-assisted gravity drainage (SAGD) is an increasingly common technique which involves drilling two horizontal wells into the tar sand deposits. Steam and hot water are injected into the upper well to reduce the viscosity of the bitumen, which will drain into the lower well where it can be pumped to the surface. The waste generated from drilling these wells is extracted from the drilling fluid by shakers and includes sand contaminated with bitumen and drilling fluid. Treatment of this waste stream is challenging and typically these sands are stored at the rig site or transported for disposal at centralized sites. This paper presents novel technology for treatment of the tar sands drilling waste generated from SAGD and other tar sands drilling operations. The continuous treatment process is based on hot water addition, mixing and separation techniques to reduce the viscosity and specific gravity of the bitumen to separate it from the sand. Treatment of cuttings with light to heavy bitumen contamination and varying quantities of fine sand and clay particles has shown this treatment method to be a simple and effective means of producing clean sand and recovering the bitumen component. The energy used to heat the circulating water is recycled to minimize waste and maximize energy efficiency. The cleaned sand can be blended with natural soil and safely disposed in the environment. The recovered bitumen can be used as feedstock for further processing and refining.With the total recoverable tar sand reserves in Canada and Venezuela estimated at 300 billion barrels, the market demand for this technology is potentially immense. Effective treatment of the tar sands cuttings will convert the waste into a valuable revenue stream in an environmentally responsible manner.