Performance Report: Whole Mud System Dewatered with 20 Hours Less Processing Time in Colorado Field Trial

Challenge: On a multi-well drilling pad in Colorado, each well needed to be dewatered for reuse on the next well. Drilling time was averaging 7–10 days and the mud volume needed to be dewatered within a 24-hr period during which the rig skidded to the next well. On previous wells it had not been possible to dewater the whole mud volume during the available 24-hr period for skidding the rig. Mud feed rates were poor, often as low as 20 gal/min; the feed rate needed to increase significantly to enable the whole mud volume to be dewatered to 8.4 lb/gal between wells.

Solution: The M-I SWACO DEWATERING Unit Type 2 is a fully automated, “plug-and-play” unit and was designed for a mud feed capacity of 100 gal/min. With the use of CD-600 CENTRIFUGE equipment, up to 140 gal/min can be processed.

Result: In this first dewatering trial for which the CD-600 centrifuge unit was used, the capability of the unit was fully tested while dewatering about 900 bbl of a 9.8-lb/gal bentonite polymer mud. The mud was successfully dewatered to obtain an effluent density of 8.4 lb/gal using an anionic coagulant, an anionic flocculant polymer and dilution with recycled effluent.

Throughout the Dewatering Unit Type 2 field trial with the CD- 600 Centrifuge, the effluent was maintained at 8.4 lb/gal compared to the feed mud density of 9.8 lb/gal. As the mud contained high amounts of clay, it was necessary to dilute with water to maintain optimum performance. The effluent was recovered as a relatively clear fluid. It was regularly tested to help ensure no polymer or coagulant carryover, even at high flow rates. The effluent was also reused for dilution at a rate of 50 gal/min so no increase in volume was created.

Tests were successfully carried out and maximum capability rates established for feed rate, dilution rate and chemical injection rates. The whole mud system was dewatered in approximately 20 hr less processing time compared to previous wells and each well on the pad was dewatered while the drilling rig was skidding to the next well.

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"The new containerized and acclimatized DEWATERING Unit Type 2 exceeded mud-feed design specifications during the field trial. With the use of the M-I SWACO CD-600 centrifuge, the unit was able to process used mud at up to 140 gal/min.”
Diana Garcia
Project Engineer