Definition - What does Annular Pressure mean?
Annular pressure is the pressure that builds up in the spaces between the drill string and the external casing or borehole wall. Excess pressure can cause problems in a trenchless drilling operation. It is important to measure and monitor this pressure while drilling if possible.
Trenchlesspedia explains Annular Pressure
A number of factors can contribute to the buildup of pressure in the annulus. When the drilling mud is not effectively transporting and removing drill cuttings, the pressure could increase. Changes in pressure and temperature surrounding the borehole could also affect the annular pressure.
It is possible to enact real time monitoring of the annular pressure in a process called measurement while drilling (MWD). Annular pressure may increase as the depth of a borehole increases. Pressure can either be static or dynamic. While annular pressure is normally expressed in pounds per square inch (psi), it may also be expressed as equivalent circulating density (ECD), which is measured in pounds per gallon (ppg).
Prediction of annular pressure is one facet of the science behind trenchless construction technology. Researchers attempt to model annular pressure to give trenchless operators a greater understanding of the drilling process.