The void between the drill string and the casing of the well borehole.


American National Standards Institute. The ANSI coordinates development of safe systems, processes and products through standards development and conformity assessment programs. Standards provide dimensions, ratings, terminology and symbols, test methods, and performance and safety requirements for personnel, products, systems and services in hundreds of industries.


American Society of Mechanical Engineers

Auxiliary Line

Service lines running parallel to the riser. These include control system fluid line, buoyancy control line, mud boost line, hydraulic supply.