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With the flourishing shale gas exploitation produces more oil based mud (OBM) drill cuttings, the hard-to-treat hazardous waste burden the local environment heavily. However, the problems of high energy consumption, high treating cost and high secondary contamination risk still remain unsolved for mainstream technologies such as thermal distillation, incineration and chemical extraction. Therefore, a new method and device based on cyclone desorption of high speed self-rotation to dispose of OBM drill cuttings are put forward to overcome the challenge. The working process includes: viscosity reduction in heated gas; cyclone deoiling; condensation and recycling of exhaust; separation of oil and water in coalescer. It is found that the self-rotation speed of solid particles in a 3-dimensional rotating turbulent flow field of cyclone is as high as 2,000 to 6,000 rad/s which coexists with revolution speed of 20 to 300 rpm. The remarkable pulsing centrifuge forces in the self-rotation and revolution coupling motion can enhance the desorption process of the oil so as to accomplish the separation and enrichment of oil and solid phase, and deep removal of organics from OBM drill cuttings. It turned out that the deoiling efficiency of OBM drill cuttings, a sample from Chongqing shale gas field, increased as the processing time longer and, to be exact, after 2.1 seconds the oil content fell from 17.9% to 0.16% which is about a half of the maximum allowable content of petroleum in pollutants, 0.3%, in GB 4284-84 "Control Standards for Pollutants in Agricultural Sludge". In general, the innovation of cyclone desorption of high speed self-rotation is the pulsing centrifuge force of self-rotation and revolution coupling motion, so it's free of chemical addition and high heating temperature. Therefore, the application of cyclone desorption of high speed self-rotation for OBM drill cuttings disposal is expected to lower treatment cost, enhance processing effect, and finally improve the environment of shale gas exploitation area and contribute to energy development.

Summary With the flourishing shale gas exploitation producing more oil-based mud (OBM) cuttings, the hard-to-treat hazardous wastes heavily burden the local environment. However, the problems of treating OBM cuttings, such as huge energy consumption, tremendous treatment costs, and high risk of secondary contamination, still remain unsolved with the current treatment technologies, such as thermal desorption, incineration, and chemical extraction. In this study, we introduce a new method and equipment based on cyclone desorption to recover oil from OBM cuttings. The technological process includes viscosity reduction in heated gas, cyclone deoiling, condensation and recycling of the exhaust, and separation of oil and water in the coalescer. Based on the analysis of the physicochemical properties and the oil distribution inside the OBM cuttings samples collected from the Chongqing shale gas field, we designed this cyclone oil desorption technology and built the pilot-scale equipment to conduct the deoiling experiments. The results showed that the deoiling efficiency of OBM cuttings improved as the processing time increased. To be precise, after 2.7 seconds of treatment, the oil content of the cuttings samples fell sharply from 17.9 to 0.16%, which is about one-half of the maximum allowable oil content in pollutants of 0.3%, specified in the national standard (GB 4284-84 1985) promulgated by the People’s Republic of China. The foundation of the technology is that the particles have a high-speedself-rotation (more than 30,000 rad/s) coupled with a revolution in the cyclone in which a generated centrifugal force removes the oil from the pores of the particles. This process is purely physical and involves no phase change of the oil, so it is free of chemical addition and high heating temperature. The application of this newly developed cyclone oil desorption technology is expected to lower the treatment costs, enhance the processing efficiency, contribute to the energy development, and eventually benefit the local environment where the shale gas exploitations take place.