Fracking of gas and oil requires forcing open rock, usually with an initial round of explosives followed by high pressure pumping of a toxic cocktail of water, chemicals, and suspended grains of sand. Massive quantities—up to 25,000 tons per well—of this frac sand prop open the blasted and pressurized fissures in the rock.
Until 2018, midwestern US mines thoroughly dominated the frac sand supply. Since mid 2017, perhaps two dozen mines have opened in the Permian Basin region, in a scramble by the increasingly debt-ridden shale industry to cut costs with inferior but cheaper sand. These mines may supply two third of US frac sand demand by the end of 20191.
Frac sand supply is highly vulnerable at processing plants and during conveyor transport. In stages dependent on electricity, when the electrons stop flowing, so does the sand. Rail transport has been disrupted by blockades and with jumper cables, though single incidents don’t have broad or long-lasting results. Truck transport is decentralized and therefore difficult to impact, with the notable exception of loading sites. For example, at the Black Mountain Sand mine3:
It takes an army of trucks to haul that much sand to well sites. And they need to get in and out of the mines efficiently. An automated system that knows which sand to feed each truck speeds the process along. Still, they come in so fast that the line can back up quickly. On a recent afternoon, it was several deep. On a really hectic day, it can swell to 100.4
An electrical outage, disruptions to loading equipment, or hardware or software damage to the automated system would make the loading process much less efficient—or perhaps shut it down entirely.
As of early 2019, sand mining is in a bust phase5 of the typical boom/bust commodity cycle. Multiple mines have been idled.6 Disruption to supply from one mine or processing plant is fairly easily replaced from others; if activist intervention forced a mine or plant to shut down, idled sites could restart to meet the demand. Targeting mines, plants, or decentralized transport would be attacks of attrition, unlikely to have systemic impact.
In contrast, truck loading sites are transportation bottlenecks before the final journey to dispersed drill sites. Breakdown in these hubs would delay critical supply of sand to multiple frac operations at once, so would more likely trigger cascading failure.