During hydraulic fracturing, sand is mixed into high-pressure fluid pumped into shale. What is the sand's role after the fractures form?

During hydraulic fracturing, why must the fluid be pumped into shale at very high pressure?

Why is a horizontal section often drilled through a shale layer before it is hydraulically fractured?

A technician pumps water-based fluid containing a friction reducer down a shale well. Why add the friction reducer?

After a hydraulic-fracturing treatment ends, some injected fluid and formation fluids move up the production well. What is this return to the surface called?

Tight rock has very low permeability, so hydrocarbons move poorly toward a well. Which action addresses that limitation?

Natural gas is held in a fine-grained, organic-rich rock formed from compacted mud, which is both its source and its reservoir. It is produced with horizontal wells and fracturing. What resource is it?

Oil from a low-permeability formation such as shale that commonly must be hydraulically fractured to produce commercially is called what?

A deposit in northern Alberta, Canada, holds a thick, heavy hydrocarbon called bitumen mixed among mineral grains near the surface. Some of it is mined at the surface. What resource is it?

Which unconventional resource is produced by pumping groundwater out of a seam, which lowers the pressure so methane held on the rock's surfaces can flow to the well?

Which unconventional resource contains kerogen that must be heated by retorting to yield hydrocarbon liquids and gases?

Natural gas is trapped in a low-permeability rock made of cemented quartz grains and cannot migrate readily toward a well. How is this resource classified?

Which location faces the greatest water-supply concern if a company withdraws water for hydraulic fracturing?

A spill releases hydraulic-fracturing chemicals onto land above a drinking-water aquifer. Which risk is most direct?

An operator discharges inadequately treated hydraulic-fracturing wastewater to a river. What environmental risk does this create?

Why can deep injection of large volumes of oil-and-gas wastewater increase earthquake risk near some faults?

Natural gas from fracked shale can emit less carbon dioxide than coal when burned for the same energy, but methane can leak from wells and pipelines. What determines the overall climate trade-off?

Compared with a vertical well, a horizontal well through tight shale contacts more reservoir rock. What accompanying trade-off is documented for this approach?

Surface mining of oil sands can supply bitumen for petroleum products. Which cost is associated with separating bitumen from the sand?

A utility replaces coal-fired generation with natural-gas generation from shale. Which statement best captures one benefit and one remaining cost?