The Function of Circulating Fluid
All diamond impregnated, surface-set diamond, TSP-set, Pax-set and tungsten-carbide set bits require the use of circulating fluid during normal operation. The circulating fluid has several functions including
- To flush the bits cuttings up and out of the drill hole.
- To clear the cuttings from the bit face so that the diamonds (or other cutting media) do not re-grind the resulting sludge.
- To cool the bit crown during operation.
- To lubricate the bit and to improve the cutting action.
- To reduce the friction of the rotating drill string.
- To monitor the behaviour of the bit and the formation being drilled. The behaviour and change of properties of the circulating fluid is an important source of information for the operator by considering: return fluid loss, system pressure increases or decreases, and changes from being acidic to alkaline.
- To reduce vibration. Wherever feasible, the use of liquid polymer viscosifiers and lubricants are recommended to enhance bit performance. As circulating fluid additives, these materials tend to reduce rod torque and vibration particularly in extremely deep or severely angled drill holes.
Determination of In-Hole Fluid Circulation Parameters
Click here to view or download the Recommended Operating Parameters for Bit Hydraulics in .pdf format. (554kb)