An umbrella term for oil and natural gas that is produced by means that do not meet the criteria for conventional production (See Conventional oil and gas development). What qualifies as “unconventional” at any particular time is a complex function of resource characteristics, available exploration and production technologies, current economic environment, and the scale, frequency, and duration of production from the resource. Perceptions of these factors inevitably change over time and they often differ among users of the term. (Source: Schlumberger 2019).
For the purposes of HEI-Energy, the phrase is defined as the wave of onshore development and production of oil and natural gas from shale and other unconventional, or low permeability, geologic formations as practiced starting around the beginning of the 21st century through multistage hydraulic fracturing in horizontal wells. UOGD operations include:
- field development: exploration, site preparation, vertical and horizontal drilling, well completion (casing and cementing, perforating, acidizing, hydraulic fracturing, flowback, and well testing) in preparation for production, and management of wastes;
- production operations: extraction, gathering, processing, and field compression of gas; extraction and processing of oil and natural gas condensates; management of produced water and wastes; and construction and operation of field production facilities; and
- post-production: well closure and land reclamation.