DIFFERENTIATING BETWEEN HYDRAULIC FRACTURING APPLICATIONS (Invited Presentation)

Hydraulic fracturing has received abundant media attention in recent years due to a rapid increase in the use of the technique in combination with horizontal drilling technology to produce oil and gas resources from tight reservoirs. Hydraulic fracturing techniques are also used in a variety of other applications that are unrelated to oil and gas production, including tunnel and dam construction, enhanced geothermal energy, carbon sequestration, groundwater remediation, block cave mining, rock burst mitigation, and water well development.

Environmental concerns associated with large-scale hydraulic fracturing in oil and gas reservoirs have resulted in legal efforts to ban the technique in certain states in the US and countries around the world. Concerns include soil and groundwater contamination and induced seismicity. A clear understanding of how hydraulic fracturing techniques are used in various applications is important to avoid unintended consequences of any regulations aimed at hydraulic fracturing in the oil and gas industry. The methodology for each application varies widely in terms of scale, pressures applied, additives, and fracture propagation. Rock stress measurements, for instance, focus primarily on the breaking strength of rock, and can be conducted with a small-volume high-pressure pump that produces only a few liters/minute. The total volume of water injected may be on the order of tens or hundreds of liters. A typical oil and gas well hydraulic fracture treatment, on the other hand, requires millions of liters of injected proprietary fluid and proppant in order to propagate and maintain the fracture effectively into the reservoir. Though both applications are termed “hydraulic fracturing”, they differ greatly in terms of potential impacts to the environment.

This presentation characterizes a range of hydraulic fracturing applications in terms of the objectives, techniques, and potential for environmental concerns associated with the standard methods. A nomenclature that clearly differentiates discrete applications is presented that is intended to help prevent the lumping of all hydraulic fracturing techniques into a single basket.