The Effect of Weight Material Type on Rate of Penetration Using Dispersed and Non-Dispersed Water-Base Muds

Abstract

ABSTRACT The penetration rates of dispersed and non-dispersed water-base muds were studied using Mancos Shale. The full-scale wellbore simulator at Drilling Research Laboratory was utilized. Previous studies1 have indicated that in invert oil muds higher penetration rates can be achieved when the weighting agent is ilmenite rather than barite. This study compares barite and ilmenite in water-base systems. Two grind sizes of ilmenite (fine and standard) were used in order to determine the effects of particle size on penetration rate. In addition to these tests, hematite, fine-grind ilmenite and barite were tested in a low colloid invert oil mud system as a supplement to the original study. An additional test was conducted with a conventional diamond bit and the low colloid oil mud for comparison. Highest penetration rates were observed with the standard particle size distribution ilmenite for the water-base muds. For the invert oil mud, similar penetration rates were observed for the fine-grind ilmenite and the hematite; the barite weighted mud resulted in relatively lower rates of penetration. The fine grind ilmenite/low colloid oil mud/diamond bit combination provided penetration rates equal to or greater than the barite/low colloid oil mud/roller cone bit combination.