Lost Circulation - Control

Control

Although preferred, ceasing lost circulation completely is not always possible or required. Controlled losses allows drilling to continue while keeping the wellbore full, preventing an influx of gas or fluid into the wellbore, known as a" kick", which can lead to a blowout.

A number of options are available when lost circulation occurs, depending on the severity.

• Minor losses may be controlled by increasing the viscosity of the fluid with bentonite and/ or polymers, or with the addition of other additives which typically includes sawdust.
• Severe losses will require increasing the viscosity of the fluid with bentonite and/ or polymers and the addition of other additives which typically includes sawdust.

Total losses can be regained through conventional use of increased viscosity and additives, or through use of unconventional methods such as pumping of golf balls, tree branches, rags, additive sacks, and other items in conjunction with, or followed by, a high viscosity fluid. If total losses occur and circulation cannot be regained, several options are available, depending on the operational requirements and depth being drilled in relation to desired production geological zones. Continuing drilling while pumping drilling fluid is one option, though continued drilling while pumping water is less costly and more often used. Sometimes the cuttings from continued drilling will aid in reducing or stop losses altogether. A third option is to cement the zone where the losses occurred, and to drill through the cement and continue drilling the well. This third option is very often the most cost effective if severe losses occur, as lost circulation can sometimes not be controlled with conventional or unconventional methods.