What is the name of the petroleum-recovery process that injects high-pressure fluid to create cracks in rock?

Hydraulic fracturing is the petroleum-recovery process that injects high-pressure fluid to create cracks in rock.

The injected fluid is usually mostly water, mixed with proppants such as sand and small amounts of chemical additives. The pressure opens fractures in low-permeability formations, while the proppant helps keep those pathways open after pressure falls.

The technique has been used in oil and gas production since the mid-20th century, but its combination with horizontal drilling helped unlock large shale reserves in the United States during the 2000s. Hydraulic fracturing is commonly called “fracking.”

It is different from acidizing, which dissolves parts of a formation with acid, and from water flooding, which injects water mainly to maintain reservoir pressure and move oil toward producing wells.