Waste mud is one of the main pollution sources in the oil and gas industry. In order to prevent the environmental pollution caused by waste drilling mud, it must be treated. According to different treatment and discharge conditions, there are many treatment methods for waste mud at home and abroad. Solidification treatment is one of the most widely used methods, especially suitable for waste mud that is not suitable for land cultivation.
1. Solidification of waste drilling mud
Solidification treatment is to put a proper proportion of curing agent into the anti-seepage waste mud pit, mix it evenly according to certain technical requirements, and transform the harmful components into a non-polluting solid through physical and chemical changes for a certain time.
Calculation method of mud solidification: the sum of solid phases after solid-liquid separation of cement slurry and desander, desilter, waste mud discharged from centrifuge, and grit discharged from grit tank.
2. MTC technology
The conversion of mud into cement slurry, abbreviated as MTC (Mud To Cement) technology, is the world’s leading cementing technology. Slag MTC refers to adding water-quenched blast furnace slag, activator, dispersant and other treatment agents into the slurry to convert the slurry into cement slurry. This technology reduces the treatment cost of waste slurry and also reduces the cost of cementing.
3. Chemically enhanced solid-liquid separation
The chemically enhanced solid-liquid separation process first performs chemical destabilization and flocculation treatment on the drilling waste mud, strengthens the mechanical solid-liquid separation ability, and converts the harmful components in the waste mud into less hazardous or harmless substances or reduces its leaching rate during chemical destabilization and flocculation treatment. Then, the unstabilized and flocculated waste mud is pumped into the turbo-type drilling fluid centrifuge. The rotating swirl in the drilling fluid centrifuge and the agitation generated by the rotating drum jointly produce a comprehensive dynamic effect, which has a strong effect on the semi-static sedimentation in the centrifuge, and realizes solid-liquid separation, so that the free water between the floc particles and part of the intermolecular water are separated by centrifugation. After solid-liquid separation, the amount of pollutants (sludge) is reduced, the volume is greatly reduced, and the cost of harmless treatment is doubled.
4. Disposal of waste mud from offshore drilling
(1) Treatment of water-based mud
(2) Treatment of oil-based mud
Process flow of mud non-landing treatment
(1) Collection unit. Waste drilling mud enters the screw conveyor through solid control equipment, and water is added for dilution and mixing.
(2) Solid-liquid separation unit. In order to reduce the water content and pollutants of the mud cake, it is necessary to add treatment agents and repeatedly stir and wash.
(3) Wastewater treatment unit. The content of suspended solids in the water separated by centrifugation is high. The suspended solids in the water are removed through the air flotation sedimentation and filtration system to reduce the content of organic matter in the wastewater, and then enter the reverse osmosis system for concentration treatment.