How does hydraulic fracturing increase the flow of oil from tight rock formations?

In petroleum engineering, hydraulic fracturing—commonly known as fracking—is a technique used to extract oil from "tight" rock formations, such as shale or dolomite, which are characterized by very low porosity and permeability.12

The process increases the flow of oil through the following steps:

• Creating Fissures: A mixture of water, chemical additives, and a propping agent (typically sand) is pumped into the wellbore at high pressure. This pressure is sufficient to crack the dense rock, creating a network of interconnected fissures that extend beyond the immediate area of the wellbore.31
• Propping Open Passages: Once the rock is fractured, the sand (proppant) remains lodged within the new fissures after the hydraulic pressure is released. This prevents the fractures from closing, ensuring that the newly created flow paths remain open.13
• Enhancing Permeability: By establishing these interconnected channels, the formation’s overall permeability is significantly increased. This allows oil that was previously trapped in impermeable rock to flow more easily into the production tubing and up to the surface.13