What Is Shale Gas?

What Is Shale Gas?

Marcellus Shale Gas Well
Photo by WCN 24/7

Shale gas is simple natural gas that has been formed inside shale formations. It is becoming a more important natural gas source in many countries. It has been recovered in the United States for a longer period of time than in Britain or the rest of Europe, but it is becoming more commonplace in Europe, as well. In 2010, the United States got 20% of its natural gas from shale, and the number is estimated to be 46% by the year 2035.

Shale gas is expected to expand greatly the amount of energy supplied for the world’s use. China has possibly the largest reserves of shale gas. It has been said that increasing development of shale gas extraction will reduce the world’s greenhouse gas emissions. It should be noted that some other studies indicate that its extraction and use may actually release more greenhouse gases than are released when conventional natural gas is recovered.

Horizontal gas drilling has been taking place since the 1930’s, and the first fracking well in the United States was dug in 1947. Fracking on a larger scale was not utilized until 1975 or so. At least in the United States, the industry has been aided by tax credits and cooperative ventures. Since its success in the United States, fracking has been used in other countries like Britain, to pursue their own shale gas deposits.

How is shale gas used as an energy source?

Many shale types do not yield natural gas. It is an unconventional source, so in order to obtain sufficient quantities to be economically feasible, the shale must be fractured, to provide adequate permeability. Natural fractures in shale allowed the gas to be more easily produced, but hydraulic fracturing is needed to create large enough fractures to obtain shale gas in quantity.

Shale gas wells are often drilled horizontally, having some lateral lengths of nearly 3000 metres. These allow the greatest area to contact with the shale. The most productive shale deposits used for gas extraction are organically rich, and they must be fairly rigid and brittle, to allow for the maintenance of open fractures.

Some shale gas is trapped within natural fractures, while other gas may be located in pore spaces. Some may have also been absorbed into organic materials within or near the shale. The gas that is found within the existing shale fractures is more immediately produced, while the gas that has been absorbed into surrounding organic materials will not be released until pressure is brought to bear by the fracking well.