Chapter 1 – Shale

Shales, also known as mud rock or clay rock, are very fine-grained sedimentary rocks with a particle size less than 0.06 mm. This rock deposits in terrestrial as well as marine environments. Along with the fine-grained sediment, sometimes organic material also deposits, particularly in a marine environment. Organic material deposits normally under a reducing environment. When the content of organic material is more than 1%, it is called carbonaceous shale or black shale. Shale is the source rock for conventional and non-conventional hydrocarbon. Because of its very low porosity and high permeability the storage capacity of shale is very low, and the generated hydrocarbon migrates to a reservoir rock with high porosity such as sandstone. But in the case of nonconventional shale gas the shale is a source rock as well as a reservoir rock. Shale gas is composed of 90% methane with a minor amount of ethane, butane, and pentane. Shale gas is an odorless gas with almost no sulfur or nitrates and is an excellent source of energy with a minimum impact on the environment. The unit of measurement of natural gas is trillion cubic feet (TCF).