Micro-nano Bubble Cavitation Reactor And Its Application In Fracturing Flowback Fluid Treatment From Oilfield

As an important stimulation measure,fracturing technology has been dominant in the exploitation of low permeability oilfields.In the drilling and exploitation processes of oil and natural gas,fracturing flowback fluid pollution is produced.Fracturing flowback fluid from oilfield has the characteristics of complex composition,variety and high content of organic species,systemic stability and high emulsification,which make it difficult to treat.The existing treatment technology has the problems of complicated and lengthy processes,high investment in equipment,variety and large dosage of chemicals and less industrial applications.The lack of high-efficiency and low-cost technology in the treatment of fracturing flowback fluid from oilfield has become increasingly prominent.Therefore,it is imperative to study high-efficient and low-cost treating technologies such as short-process modularization technology,armored devices and inexpensive green chemicals.Oxidation is an essential step in the treatment of fracturing flowback fluid from oilfield,which can degrade organic pollutants in waste liquid and reduce COD of waste liquid considerably.The paper studied the micro-nano bubble manufacturing and micro-nano bubble cavitation/oxidation technology through the coupling of hydrothermal jet and cyclotron pressurization processes.The internal flow field of the cyclotron pressure component,the key component of the micro-nano bubble reactor was simulated,and the structure of components were optimized.Based on that,a prototype of micro-nano bubble cavitation reactor was developed,and the performance of which was evaluated with two parameters,bubble size and dissolved oxygen content.The micro-nano bubble cavitation reactor and the reactor enhanced chemicals technology were used to treat fracturing flowback fluid from oilfield respectively,and the effect of both treatments on waste liquid were investigated.?1?Characteristic analysis of fracturing flowback fluid from oilfield.According to analyzing the general characteristics of the fracturing flowback fluid from Changdi Waste Water Station of Gudao Oilfield in Shengli Oilfield,the basic physicochemical properties,the metal elements content,the particle size distribution and the types of suspended solids and the types of organic matter were mastered.;The sedimentation and separation characteristics of suspended solids and petroleum substances in fracturing flowback fluid from oilfield were analyzed through sedimentation experiments;Through the oxidation characteristics analysis of waste liquid by hydraulic cavitation/oxidation method,the degradation of oilfield fracturing flowback fluid and its main component-diethylhexyl phthalate?DEHP?was analyzed.The experimental results show that the hydraulic cavitation cavitation/oxidation technology has the tendency to degrade macromolecular organics into small molecular organic matter gradually,and produce H₂O and CO₂eventually.?2?Design,structural optimization and performance test of micro-nano bubble cavitation reactor.The structure of the reactor was designed by using the three-dimensional mapping function of Soildworks software and the internal flow field of the cyclotron pressure component was simulated by using Fluent software.Through the simulation results,the optimum structure of the cyclotron pressure component was obtained:the 45^o inclination angle,the three-fan structure,the 12^o contraction angle in the contraction section and the 55^o diffusion angle in the diffusion section.The bubble size of the micro-nano bubble cavitation reactor was analyzed by high-power and large-depth microscopy,the micro-nano bubbles with size of 780 nm were observed.The oxygen carrying capacity of micro-nano bubble cavitation reactor was tested by dissolved oxygen concentration detector.the results showed that the reactor could increase the dissolved oxygen value of fracturing backflow fluid from oilfield by 115.1%.?3?The treating experiments of micro-nano bubble cavitation reactor on fracturing flowback fluid from oilfield.The micro-nano bubble cavitation reactor was used to treat fracturing fluid flowback from oilfield,and effects of fluid feeding rate,gas feeding rate,reaction time,solution pH value and initial COD on the treatments of organics in the waste liquid were investigated.The experimental results show that the COD removal rate approaches 25.64%under the conditions of pH=2,the initial COD of 7800 mg·L^-1,the fluid feeding rate of 210 L·h^-1,the gas feeding rate of 100 L·h^-1 and the reaction time of30 min.The micro-nano bubble cavitation reactor treated fracturing flowback fluid from oilfield by using H₂O₂,potassium ferrate,polyaluminum chloride and Fenton reagent as oxidants respectively.The experimental results show that the COD removal rate can approach 50.64%under the conditions of pH=1,the fluid feeding rate of 210 L·h^-1,the gas feeding rate of 100 L·h^-1,the reaction time of 30 min and the potassium ferrate dosage of 400 mg·L^-1.The enhanced chemicals treatment technology of micro-nano bubble cavitation reactor greatly improves the treating effect of fracturing flowback from oilfield,and provides new technical support for the treatment of fracturing flowback fluid from oilfield.The paper has 44 pictures,9 tables and 114 references.