What is loss circulation in drilling?

Question

What is loss circulation in drilling?

Answer 1

Not sure why this is in the Arts & Humanities category, but here's the info you seek:

circulation loss

1.  n.  [Drilling] ID: 1293

The loss of drilling fluid to a formation, usually caused when the hydrostatic head pressure of the column of drilling fluid exceeds the formation pressure. This loss of fluid may be loosely classified as seepage losses, partial losses or catastrophic losses, each of which is handled differently depending on the risk to the rig and personnel and the economics of the drilling fluid and each possible solution.

http://www.glossary.oilfield.slb.com/Dis...

Kabum

Answer 2

When they drill for oil they encounter gas, oil or water under pressure which can come boiling up the outside of the casing and create mayhem (and fire) on the drilling rig.

To prevent this, drilling fluid or "mud" is pumped down at a pressure equal to the down hole pressure.  This fluid circulates back up the hole and is pumped down again constantly.

If the Drill Push miscalculates or if there is a sudden unanticipated break in the rock formation, the fluid an "escape" out into the formation and so not circulate back up.  Circulation has been lost.   While there is some loss of fluid most of the time, a sudden loss of most of the fluid is very dangerous and can sometimes cause a blow out and fire - although modern blowout preventers are very fast and effective.