China has enacted a number of environmental protection regulations to limit waste discharge during well drilling and completion. Most domestic oil fields solidify the waste in sewage pits after drilling and well completion, according to Kosun Machinery in an article on Environmental Expert. When the waste in sewage pits falls into clear liquid and sludge via natural sedimentation, two-thirds of the upper clear liquid is drained. Curing agent is then added to the remaining sludge for solidification.
Because the waste contains a lot of water and requires the use of a significant amount of chemical agents, the solution is expensive, achieves unsatisfactory results and fails to completely eliminate pollution risks.
Faced with more stringent environmental protection regulations, onshore oilfields are replacing the direct solidification method with a solid-liquid separation method. Effective mud/gas separation is a key aspect of this process. One way this can be achieved by using dewatering equipment such as orifice filter press, filter belt dewatering conveyors and decanter centrifuges. However, dewatering equipment is still in the trial phase and yields lower efficiency due to its low degree of automation.
Kosun Machinery has developed a solution that reduces waste at the source by disposing of it during drilling. The solution includes the following four steps:
- Solids control.
- Dewatering/water treatment/water recycling/filtration.
- Mud recovery.
- Stabilization/biodegradation/thermal desorption/cuttings reinjection.
During the drilling process, the Kosun Mud Solid Control System connects to the mud pump and performs four-stage solids control treatment on the mud. The treated mud can be put directly into use, and the dewatered waste can be delivered via conveyor to the Hi-G drying shaker and vertical cuttings dryer for further separation.
After being treated by purifying equipment, the separated water can be recycled. The waste residues become very dry after going through the Hi-G shale shaker and vertical cuttings dryer and can be disposed of via solidification, biodegradation, thermal desorption and cuttings reinjection.
Through this method, zero-waste discharge is achieved.
Nuverra Environmental Solutions is also working on a process to turn drilling waste into reusable products.
Photo: oil pump via Shutterstock.