The CLS unit deployed at a drilling site in the Williston Basin
An alternative to trucking: on-site solutions for brine mud remediation
Drake Water Technologies, Inc. (DWT), Helena, MT, in cooperation with National Oilwell Varco (NOV) FluidControl, Denver, CO, has conceived, developed, and demonstrated a bench scale and pilot Cuttings Leaching System (CLS) for treatment of salt water brine mud (SWBM) drilling residues. The mobile CLS process was specifically designed to reduce salt content and render treated solid residues safe for on-site disposal and beneficial use in the reclamation of drilling sites. Use of the mobile CLS system will eliminate the costly collection, transport, and landfill tipping fees associated with current disposition of these wastes. The research and development for the new CLS technology has been supported and funded by NOV.
CLS TREATMENT PROCESS
The CLS process treats salt water brine mud (SWBM) drilling residues by reducing salt content and rendering treated solid residues safe for on-site disposal. The SWBM drilling residues are treated in a fluidized bed. The solids are treated as they sweep through the system. The “washing” is done in the interstitial pockets of the solids that contain the dissolved salts, which are subsequently withdrawn in a brine at the top of the CLS unit. The clean solids are augered out of the base sump of the unit and leave the unit as a damp, stackable clean solids cake that can be used in reclamation at the site.
CLS in the Field
On September 8, 2015, Drake Water Technologies, Inc., in cooperation with NOV staff, deployed the CLS prototype unit to a drilling site west of Williston, North Dakota. Following deployment and shakedown, the prototype was operated successfully with the following field results:
⦁ >98% removal of salt according to EC probes in the system
⦁ >98.8% chloride removal by Cl- ion specific electrode resulting in final chloride in solids of <1,000 mg/kg on a dry basis
⦁ Chlorides in treated material leachate were 216 mg/L, which is less than the 250 mg/L specified by the ND Department of Health
⦁ Sampled product was taken for a maximum throughput run averaging 612 lb mass per hour, which is >20% above system design throughput of 500 lb mass per hour.
⦁ Dewatering screw product exhibited 20% moisture by mass
⦁ CLS system design was tolerant of upsets and recovered quickly from upsets.
Laboratory results from a post-treatment sample collected during a CLS run demonstrated that the treated cuttings contained120 mg/L chloride, less than half the limit set by ND DEH.
Laboratory analyses from several samples collected by staff during several runs resulted in an average chloride content of 57,315 mg/L in the feed materials (both centrifuge and shaker cuttings) and an average of 672 mg/L in the treated material. The result is a 98.8% removal of chloride.