Improving the Utilization of Vertical Cuttings Dryer (VCD) Units to Process Hazardous Drilling Waste, in Rajasthan, India
Authors: Rajaram M. , Lang C. M. , Elliott T. , Lochhead I. , Patel M. , Sawant V. 
Published: November 2015

Cairn India is an operator carrying out development and exploration drilling in the RJ-ON-90/1 area on land in Rajasthan, India. The block is approximately 3000 sq. km and there have been over 400 development wells and 52 exploration wells drilled since 2009. CIL as an organization decided to adopt best practices in all aspects of its operations including environmental management. This paper addresses how the use and optimization of cuttings dryer technologies has led to improved efficiencies in waste management while maintaining environmental targets without increase in costs. The optimization process also has a positive impact on waste management HSE aspects by reducing the number of units being used and improving process control.

A ramp up in drilling activity between 2013 and 2015 resulted in significant quantities of drilling waste (hazardous cuttings waste generated from drilling with Synthetic Based Mud) that threatened the overflow of the CIL hazardous landfill site located at the Mangala Processing Terminal. With environmental regulations becoming more stringent and land costs increasing steadily, the Company had to re-think its approach towards waste management.

The presence of hazardous drilling waste is not only an environmental concern but an operational challenge for the Company. During the rainy season, the rainwater turns the hazardous solid waste into slurry thereby resulting in hazardous liquid waste. This liquid is extremely difficult to treat and nearly impossible to reduce by evaporation. With rainwater filling the waste pits at the rig site, this hazardous liquid waste may flow into the adjacent lands destroying crops and imposing a threat to cattle that may drink the water. The key was to treat hazardous solid waste as soon as possible and dispose of the residue into the landfill.

A primary target for improvement in effective management of hazardous drilling waste solids is to process all the generated hazardous waste in order to reduce oil-on-cuttings (OOC)% to an acceptable level prior to disposal, and if possible recycle as much recovered fluid (base oil/emulsion) as possible. The maximum OOC as per the Central Pollution Control Board, India is 10gm/kg for the cuttings to be safely disposed of in lined pits.

Centrifugal / Vertical Cuttings Dryer units are often used as a part of waste management strategies on both onshore and offshore rigs. VCD manufacturers build units which to date have primarily been installed at the rig sites, and are plumbed directly into the shakers by means of screw conveyors that transfer the cuttings from the shakers directly to the VCD unit. This paper illustrates that in cases where multiple VCDs are required, the number of units may be optimized with minimal loss in base oil recovery and such optimization may also deliver cost benefits dependent upon drilling activity levels.

Additionally, reduction of waste pit requirements has the potential to reduce environmental footprint along with increased cost savings. Using SBM with reduced environmental impact may potentially increase the usage of SBM allowing for greater technical choices during well bore construction.