The following are possible indicators of hole cleaning problems:

• excessive overpull on connections and trips
• reduced overpull when pumping
• excessive fill after trips
• erratic and increasing torque while drilling
• lack of cuttings over shakers (or large slugs of cuttings followed by periods of very few cuttings).

Solutions to Hole Cleaning Problems

Circulation, no matter how long it is carried out, does not guarantee effective hole cleaning. Special tripping procedures may be necessary in wells with cutting beds and in wells with severe overgauge sections.

Solutions such as pumping and backreaming out, or using undergauge stabilisers in the string to disturb cutting beds, have been effective.

The instantaneous ROP shall be such that cuttings can be removed.

Downhole Motors in Deviated Wells

Drilling with a downhole motor in an inclined well without rotating the drillstring may result in undisturbed cutting beds. Where possible, the string should be rotated prior to POOH in addition to implementing some or all of the above measures.

Hi-Vis Pills in Deviated Wells

In deviated wells, increasing the mud viscosity and pumping Hi-Vis pills may not improve hole cleaning.

A series of Low-Vis pills giving a more turbulent flow, followed by a heavy pill to sweep the disturbed cuttings, may improve hole cleaning in these sections.

The following table lists the recommended total volumes (Low-Vis + Hi-Vis pills) for pumping sweep pills in deviated wells: