Economic Disposal of Solid Oil Field Wastes Through Slurry Fracture Injection

Abstract

Abstract A variety of solid oil field wastes, including produced sand, tank bottoms, and crude contaminated soils from old well cellars and tank farms can be economically disposed of in an environmentally acceptable manner through slurry fracture injection (SFI). Solids are mixed into a slurry with fresh or produced water and injected at high pressure into suitable sand formations. The carrying fluid bleeds off rapidly, leaving behind a pod of solid wastes entombed by the natural earth stresses. High fluid leakoff allows more efficient creation and packing of short wide fractures. At shallow to moderate depths, in-situ stresses may be sufficiently modified to establish horizontal fractures and allow periodic disposal of large quantities of solids - on the order of tens of thousands of cubic yards. With proper process design and monitoring, fracture growth can be carefully controlled and contained within the target interval. The slurry fracture injection process has been successfully applied to dispose of large quantities of oil saturated sands and tank bottoms in Alberta and Saskatchewan, Canada. This technique offers a number of economic and environmental advantages for disposal of solid oil field wastes. when reinjecting into depleted oil sands, the crude waste is simply being returned to Its place of origin. The long term liability to the operator is eliminated, in marked contrast to surface storage or landfill disposal. Finally, for moderate to large quantities of solid waste fracture injection costs are less than typical transport and landfill disposal costs. Introduction Oil field operations have historically produced a variety of solid wastes associated with drilling, production, and storage processes. When a well is drilled oily cuttings and drilling muds are generated. In the past these materials were sometimes dumped or stored in unlined pits near the well. During production, oily sand is often produced and settles, along with scale, in tank bottoms. In some instances large scale sand production is actually promoted to enhance oil production, such as With cold production operations in Alberta. And finally, crude transport and storage operations are subject to accidents and spills, resulting in large quantities of crude contaminated soils around wellheads, pipelines, and tank farms. Crude oil and crude contaminated sands or soils are generally designated as non-hazardous wastes because the material typically does not contain significant quantities of toxic aromatic hydrocarbons. However, these materials must still eventually be disposed of in an environmentally acceptable manner. The problem can become most pressing as oil fields Within urban areas reach the end of their productive lives. P. 313