Rock Products

MAY 2015

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www.rockproducts.com Frac Sand Insider May 2015 | 35 Geology Frac sand ("raw frac sand") is an industrial mineral commodity that consists of a naturally occurring, highly pure silica sand that is used as a proppant during hydraulic fracturing of unconvention- al oil and gas reservoirs to maximize and extend well production (Beckwith, 2011). A proppant is a granular material that is added to the fracking fuid to prop open the fractured formation to pro- mote the economic fow (conductivity) of hydrocarbons during a well's productive life (Beckwith, 2011). Unconventional reservoirs are reservoirs with low permeability (are "tight") to the fow of hy- drocarbons. Such reservoirs may include tight sandstones, shales and carbonates, or coalbed methane reservoirs that cannot be pro- duced at economic fow rates or cannot recover economic volumes of gas unless the well is stimulated by a large hydraulic fracture treatment and (or) is produced using horizontal wellbores (Oil and Gas Journal, 2014). The current hydraulic fracture treatment pro- cess involves multi-stage fracturing of up to a few dozen stages, allowing for a large number of fractures to be created at specifc locations within a single wellbore (Rock Products, 2014c). Such treatment requires large quantities of frac sand for each well in a productive play, with the average 10,000-ft. horizontal well in 2010 using as much as 2,500 tons (2,268 metric tons) (Geiver, 2014). The recent meteoric rise in the demand for frac sand has par- alleled the upward trend of horizontal drilling and hydrofracking em- ployed by the petroleum industry as it responds to growth in the global energy market, especially the demand for environmentally cleaner-burning natural gas. While the principal source for frac sand is the traditional glass sands of the Midwest that are primarily pure silica, the high silica content is but one of the necessary criteria. Among the additional specifcations are requirements for high sphe- ricity/roundness, a uniformly medium- to coarse-grain size, high crush resistance, low solubility, low turbidity, and good friability. Ad- ditional factors that infuence the economics of frac sand mining are the deposit's accessibility at or near the surface, areal extent and thickness, textural uniformity, nearness to trucking and rail transpor- tation routes, and proximity to the active unconventional petroleum basins (Figure 1). INTRODUCTION 1. Map of shale plays and basins in North America. (Modifed from U.S. Information Administration, 2011; and Kuuskraa and others, 2011.) Shale plays

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