Short answers, pulled from the story.
Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen, a solid mixture of organic chemical compounds. This substance differs from bitumen-impregnated rocks and humic coals because its maturation does not exceed early mesocatagenetic stages.
The largest resource deposits occur in the United States within the Green River Formation, covering portions of Colorado, Utah, and Wyoming. Deposits in the United States constitute more than 80% of world resources, with other significant holders being China, Russia, and Brazil.
Humans have used oil shale as a fuel since prehistoric times because it generally burns without any processing. Around 3000 BC, rock oil was used in Mesopotamia for road construction and making architectural adhesives.
These deposits have given rise to expectations of yielding at least 40 liters of shale oil per tonne using the Fischer Assay. Analysts distinguish between oil shale resources and oil shale reserves, where resources refer to all deposits while reserves represent those extractable economically using existing technology.
Mining oil shale involves numerous environmental impacts more pronounced in surface mining than underground operations including acid drainage induced by sudden rapid exposure and subsequent oxidation of formerly buried materials. Above-ground retorting uses between one and five barrels of water per barrel of produced shale-oil.