The vast majority of previous work on cuttings transport concentrated on water-base mud systems. The use of low toxicity oil-base mud continues to rise due to increasing environmental concerns with the use and disposal of conventional diesel oil-base mud systems. This study utilizes a full scale test apparatus to compare the cuttings transport performance of low toxicity oil-base and water-base mud systems with similar rheological properties, using limestone drilled cuttings. Extensive comparisons are now being made of cuttings transport efficiency for different mud types and hole angles from a practical standpoint.

The results indicate that the water-base mud and the low toxicity inverted emulsion oil-base mud systems perform slightly different at all angles of inclination except at the critical range 40° to 50° where the oil-base muds have higher annular cuttings concentration due to severe cuttings bed down-sliding. Limestone cuttings transport using a water-base mud, as well as a low toxic oil-base mud, shows cuttings concentrations increase with increasing mud yield point. The effect of increased yield point and plastic viscosity increases cuttings bed buildup, bed down-sliding and gel film thickness, thus reducing transport performance. In most cases the increase in hole inclination angle results in reduced transport efficiency.

Torque requirements are significantly less for oil-base muds having the same annular cuttings concentration. For both muds the torque requirements increase with increasing yield point and plastic viscosity at higher hole inclinations.

You can access this article if you purchase or spend a download.