Permafrost 1 : (n.) Drilling Fluids. The permanently frozen subsoil that lies below the upper layer (the upper several inches to feet) of soil in arctic regions
Schlumberger Ltd. (The World's Leading Supplier Of Technology, Integrated Project Management And Information Solutions to Customers Working in The Oil and Gas Industry Worldwide), Schlumberger Oilfield Glossary Cedex, France 2014. http://www.glossary.oilfield.slb.com/en/Terms/sym/ a.aspx, (Ergo - Brit) {766}