Such rocks are said to be permeable; sandstones and gravels are good examples of permeable rocks.
In areas of permeable rocks, most rain soaks into the ground.
They are formed when heat from the caldera encounters water in permeable rock and pressure builds, venting steam.
During the process, fracturing fluid leakoff (loss of fracturing fluid from the fracture channel into the surrounding permeable rock) occurs.
In the case of the Hamza, the porous and permeable sedimentary rocks behave as conduits for the water to sink to greater depths.
Once water creates a channel through the permeable rock to the producing wellbore, there is little benefit in injecting additional water.
The chalk is a white sedimentary rock, notably homogeneous and fine-grained, and very permeable.
A fine-grained, permeable rock, for instance, will provide a much greater surface area than a densely cemented, massive rock.
In addition to coal methane or gas trapped in less permeable rocks or gas hydrates, the most promising source appears to be shale gas.
A trap forms when the buoyancy forces driving the upward migration of hydrocarbons through a permeable rock cannot overcome the capillary forces of a sealing medium.