1. n. [Shale Gas]
A fine-grained detrital sedimentary rock formed by consolidation of clay- and silt-sized particles. Mudrocks are highly variable in their clay content and are often rich in carbonate material. As a consequence, they are less fissile, or susceptible to splitting along planes, than shales. Mudrocks may include relatively large amounts of organic material compared with other rock types and thus have potential to become rich hydrocarbon source rocks. The typical fine grain size and low permeability, a consequence of the alignment of their platy or flaky grains, allow mudrocks to form good cap rocks for hydrocarbon traps. However, mudrocks are also capable of being reservoir rocks, as evidenced by the many wells drilled into them to produce gas.