Study On Electrochemical Treatment Of Flowback Of Fracturing Fluid

At present,hydraulic fracturing technology has become the main means of reservoir reform and stimulation.Fracturing fluid used must be returned to ground for reducing damage to the stratum.Thus,flowback of fracturing fluid has become the key problems restricting the ecological development of oilfields.As a result of complex composition and difficult to deal with flowback of fracturing fluid,there are many drawbacks using traditional methods.Electrochemical oxidation has significant advantages in treating flowback of fracturing fluid,with broad prospects for development.In this paper,laboratory experiment makes up simulated flowback of fracturing fluid according to the actual characteristics of flowback of fracturing fluid,and research the effect of processing time,temperature,relative current density and concentration Cl^-to HPG on the electrochemical oxidation,degree of degradation about HPG was characterized by apparent viscosity and viscosity average molecular weight.Orthogonal experiments are designed to determine the proportion of the effect of different influence factors to the electrochemical oxidation of simulated flowback of fracturing fluid.To explore the indirect oxidation mechanism,laboratory contrastive experiment research the effect of containing different electrolytes NaCl and NaNO₃ during same other experimental conditions for exploring indirect oxidation mechanism of Cl^-.Benzoic acid is used to seize HO·for exploring indirect oxidation mechanism of HO·,and research the changes of HO·produced during same other experimental conditions.The presence of boron influences reconfigure the fracturing fluid using flowback of fracturing fluid,and emission standards are strict.So,to explore the existing form of boron is crucial in flowback of fracturing fluid.By measuring the content of boron,IR,TGA and SEM,to make a thorough inquiry about broken key position of HPG and the existing form of boron after electrochemical oxidation.The research results show that the degree of degradation of HPG increase with processing time prolonging,higher temperature and relative current density are beneficial to the degree of degradation of HPG,Cl^-has a significant oxidation effect to the degradation of HPG,and its viscosity-reducing effect contributes 60%in total viscosity reduction.And the viscosity-reducing rate showed a significant increase with the increase of Cl^-concentration at first,but the increase was not obvious as the Cl^-concentration continues to increase.The results of orthogonal experiments illustrate that the order of the influence factors is processing time>temperature>Cl^-concentration>relative current density.The results of the content of HO·show that the amount of HO·increases first and then decreases as the reaction time prolonged,increases with increasing temperature,and increases then decreases slightly with improved relative current density.However,the relationship of the amount of HO·and NaNO₃concentration is not obvious.The results of the existing form of boron in the flowback of fracturing fluid after electrochemical oxidation show that part of the crosslinked boron is released by the breaking effect,and the amount of release increases with the extension of the electrolysis time.The detection results of IR,TEM,and viscosity average molecular weight of HPG before and after electrochemical oxidation show that electrochemical oxidation effectively degrades HPG and releases boron in the crosslinked state.