Produced solids, contaminated soils from refinery sites, drilling mud and rock chips. and other low toxicity solid wastes can be economically disposed of in an environmentally acceptable manner using slurry fracture injection. Ideal target strata are found in horizontally stratified sediments isolated from the surface by low permeability barriers, and of high porosity and permeability. Slurried wastes are injected under high pressure, the carrying fluid bleeds off rapidly, leaving behind a pod of solid wastes entombed by the natural earth stresses, with no excess pressures to cause future problems. Environmental risks associated with this approach to waste management are far less than conventional landfills, the economics are similar or better, and the need for long-term maintenance or permanent land use changes are eliminated.
Wastes solids are produced in the oil industry during drilling. as spent drilling mud and rock chips; during production, as produced solids. either large quantities of produced sand or smaller quantities of produced times; and from other sources such as contaminated soils from crude oil or product refinery wastes of a solid nature such as spent catalyst, and so on. The industry is seeking economical and environmentally secure means of permanently disposing of these wastes.
In this article, a new approach to the permanent disposal of solid oil-field wastes is proposed, The technique is high pressure slurry fracture injection, and uses well understood oil-field technology in a novel application. On the surface, granular wastes are slurried, introduced into a reciprocating high pressure slurry pump, and pumped down the well, exiting through perforations in a suitably chosen receiving formation.. The excess fluids that carried the solids dissipate into the porous permeable stratum, leaving the solid wastes behind, permanently entombed by the weight of the overburden above them.
This article will discuss the sources and types of waste proposed for slurry fracture disposal, present precedents for this type of disposal, explain why slurry fracture injection has a high environmental acceptability, identify the most desirable stratigraphic conditions for application of this technology, present relevant technical considerations, and end will discussion of several real applications in the mineral industry.
All phases of the oil industry. from exploration through drilling, producing, refining, and marketing, generate some amount of solid waste, most of these wastes being of extremely low toxicity, or even totally benign, but of no possible use.
During exploratory and development drilling, the drilling mud and rock chips must be disposed of in an environmentally acceptable manner. Recently, ground-up rock chips in mud have been successfully disposed of in the North Sea and other environmentally sensitive areas by injection under high pressure through the annulus behind intermediate stream casing 1 (Figure 1). Because casing is sealed in shale strata, this injection process takes place in a low permeability medium, requiring forcing of the slurry of fine-grained wastes into the formation, generating an hydraulic fracture (parting) of the shale.