Drilling for natural gas and oil in the northern states will grow inexorably over the next few decades. New environmental regulations imposed by state environment protection agencies, such as the PADEP, now address disposal of drilling fluids. These new regulations can significantly add to an energy companies drilling budget. Southern states have begun adopting similar regulations as an alternative to the open-pit disposal approach for drill tailings.
S. Howes, with significant input from the operator and energy company, designed and built a closed-loop solids control system to solidify and neutralize residual drilling cuttings. S. Howes designed a system that greatly reduces the amount of haul-off and over-bulking of cuttings by utilizing a pugmill unit to process the drill cuttings. Unlike many other service providers attempting to develop similar systems, our setup processes air and mud drilled cuttings without having to rig up or down more equipment. The unit is completely self-contained and at no time do cuttings have to be transferred over open ground. The auger tank sits underneath the rigs primary shakers and captures the cuttings as they fall off the shaker slides. Once inside the auger tank cuttings are conveyed via dual screws, and then up into the pugmill by the incline auger. The pugmill consists of dual counter rotating paddle augers that blend wet cuttings simultaneously with lime or other bulking agents. The lime comes from a 30 ton portable silo. It is equipped with a dust house for loading, and the filters can be purged with air if needed. It has a 30 ton capacity which allows you leeway between refills of the pneumatic trucks which generally run around 22 tons. The bulking agent is augered into the pugmill to mix with the wet cuttings. All the augers are controlled by a VFD control panel so drying agent can be administered dependent upon the wetness of the drill cuttings. This helps to allow adequate bulking and controls the troublesome over bulking associated with the mixing with an excavator. A centrifuge stand can be mounted over the auger tank to process those solids as well.
This particular operator was drilling the 17 1/2” surface hole with water-based spud mud and discharging directly into the auger tank for solidification with the pugmill. Depending upon the wetness of those cuttings the VFD augers could be synced with that of the lime silo for the appropriate bulking. Product is then discharged into a 20 yard roll-off container for shipment to landfill. After running 13 3/8” casing we processed the 12 ¼” and 8 ¾” vertical air sections of the hole. The operator had a shale gas separator rigged up directly in front of the auger tank discharging solids into it, and the tank is plumbed for a trash pump to circulate water for eliminating dust. Finally, kicking off the curve section on synthetic oilbase (SOBM) we have a secondary drying shaker that mounts inside the auger tank for that portion of the hole. The effluent is pumped into the centrifuge for processing and reuse. The fluid recovered can also be blended with unweighted slurry in a whole mud dilution. This minimizes the volume lost to the centrifuge, and helps the mud retain its chemical properties while still maintaining an appropriate low gravity solids content. Options for fluid recovery can be tailored to the customers’ specifications.
Assembly of the unit is fairly simple and consists of only 5 pieces. It has a very small footprint in the backyard which is helpful on multiple well pads where space restraints are an issue.
In summary, the system benefits the drilling company by:
• Allowing the operator to use one setup to process air and mud cuttings
• Reducing over bulking and lowers tonnage by 1/3 compared to that of mixing with an excavator
• Reducing bulking significantly lowers trucking costs, disposal costs at the landfill and the amount of bulking agent needed to process cuttings
• Eliminating cuttings being transferred over open ground because it is a self contained unit
• Creating virtually dust free, consistently mixed cuttings
• Creating an environmentally friendly solution in today’s ever evolving Eco-conscious oilfield