Characteristics And Application Of Physicochemical Biological Coupling Treatment Process For Waste Drilling Mud

Aiming at the safe disposal and resource reclamation of waste drilling mud in oil and gas fields,this study proposed a physicochemical biological coupling treatment and resource utilization technology based on the characteristics of mud in terms of super stability,high turbidity and complex composition.Herein,we investigated the operation conditions and pollutants reduction efficiency of the core process of each treatment unit.The applications of centralized treatment for waste drilling mud were further explored.The results provide a theoretical and practical basis for the treatment of waste drilling mud.The waste drilling mud is viscous and semi fluid,with solid content of 15%～25%and colloid content of more than 90%.Based on its remarkable high turbidity and super stability characteristics,a high-efficiency solid-liquid separation technology with delayed stirring was proposed in order to ensure the separation effect of the solid-liquid phase after gel breaking.For the purpose of reinjection into the formation after treatment or preparation of drilling and production fluid,a three-stage treatment strategy with the core of"iron carbon micro electrolysis+nucleation-induced pelleting coagulation+contact oxidation-ozone floatation+nucleation induced chemical hardening"was put forward in view of the characteristic pollutants such as COD_cr,petroleum,corrosion bacteria and dissolved salt in the mud separation fluid.There exit two categories of solid material after solid-liquid separation.For one thing,the rock cuttings composed of crushed stones are solidified and used for building materials preparation.For another,the sludge formed by a large amount of clay is treated by special microorganism induction and indigenous microorganism co-remediation.Finally,the resource utilization of waste drilling mud and near zero emission of pollutants can be realized.The results showed that under the optimal coagulation conditions,the average particle size and settling velocity of flocs in the delayed stirring system were 7.86 mm and 27.76 mm/s,respectively,demonstrating a significantly better solid-liquid separation effect compared to that of conventional coagulation.After separation,the COD_cr in water can be reduced to less than 300 mg/L by iron carbon micro electrolysis with nucleation-induced pelleting coagulation and bio-enhanced contact oxidation.After further control of corrosive bacteria and dissolved salts by the deep process of"ozone flotation+nucleation induced chemical hardening",the effluent of biochemical section can stably meet the requirements of reinjection and drilling fluid configuration.For the treatment of rock cuttings in the separated solids,the composite LSH/SYZ curing agent was employed with the dosage of 22.5%.The strength of the solid block was more than 1.5MPa after molding and air drying,and the concentration of pollutants in the leaching solution was lower than the relevant limit requirements in the Identification standards for hazardous wastes-Identification for extraction toxicity（GB 5085.3-2007）.After the sludge treatment by special microbial agents and indigenous microorganisms,the degradation rate of petroleum was more than 95%,and the biological toxicity was within the scope of safety control.Based on the above technical ideas,the design plan of a waste drilling mud treatment plant in 100000 m³/a is proposed.The project covers an area of 105 mu,with a total investment of 49.95 million yuan and a total cost of 84.63 yuan/ton per unit mud treatment.After the project is put into operation,63000 m³ of water resources can be recovered annually,more than 3 million pieces of unburned bricks can be prepared,and15000 m³ of oily sludge can be repaired.The construction and implementation of the project is of great significance for the optimization of oil and gas fields,including solving environmental protection treatment and resource reclamation of waste drilling mud,alleviating the current situation of local water shortage,and promoting the green and sustainable development.