Environmental Control of Drilling Mud Discharge Through Dewatering in Cold Weather Climates: Effect of Ambient Temperature

Abstract

ABSTRACT The paper presents results of an experimental study into the effect of drilling mud temperature upon the dewatering performance. Three temperature ranges were considered: from flowline temperature to room temperature, from room temperature to freezing point, and the freeze (-4°F)/thaw (54°F) cycle. The tested drilling fluids included unweighted and weighted fresh water muds and a weighted salt water mud. A sealed laboratory batch reactor was used in the experiments to prevent rapid vaporization of separated water at temperatures above 140°F. Also, ice or ice-salt baths were utilized for deep freezing. The dewaterability (net water removal) was measured with a bench-top plate press under constant expression pressure 30 psi. The freeze/thaw treatment greatly enhanced dewaterability by releasing 34-39% by volume of the mud water. Mechanical dewatering followed; it required half the chemicals and released an additional 36-43% of water. The process proved to be very effective, reducing waste mud volume by 64-72%. It also seemed to be well-suited for the Arctic with its natural freeze/thaw cycles. The results of experiments at temperatures above 70°F showed that there is little advantage to dewatering hot drilling mud diverted from active system. A 10% increase of water removal was observed above 140°F. The experiments at temperatures below 70°F showed that in cold weather climates the waste drilling mud diverted from active system should be dewatered when its temperature is still above 40°F. Otherwise, more chemicals will be needed for separation enhancement or the dewatering process will become entirely ineffective.