Study On The Stability Mechanism Of Produced Water From ASP Flooding

With the large scale popularization and application of the ASP flooding technology,the output of produced water from ASP flooding is increasing.The water quality is becoming more complex and the difficulty of treatment is increasing,which has become one of the technical bottlenecks in the construction of oil field ground engineering.The produced water from ASP flooding has the characteristics of high degree of oil emulsification,high particle size oil droplet content,high viscosity,high interfacial film strength and high salinity.Demulsification and destabilization are the keys to improve the efficiency of oil-water separation.The study on stability of produced water from ASP flooding is the premise of demulsification and destabilization.The research objects in this paper are the simulated water samples of produced water from ASP flooding.The stability of produced water from ASP flooding is studied through combining test and molecular simulation.The main contents are as follows:?1?Stability analysis is conducted in simulated produced water from ASP flooding.The effects of temperature and drug concentration were investigated on the stability of ASP flooding.The results of the study showed that,with the increasing temperature,the absolute value of Zeta potential and oil content first increased and then decreased,viscosity decreased,surface tension decreased slightly,and oil droplet size increased slightly.The presence of surfactants reduced oil content and surface tension,increased Zeta potential,decreased oil droplet size,and made moil droplets difficult to gather and dispose;the presence of polymer increased the viscosity of produced water,oil content and Zeta potential;with the presence of alkali,the oil content of the system decreased and then increased,and the surface tension decreased,the Zeta potential increased and then decreased,and the oil droplet size decreased.With the extension of settling time,the simulated produced water was more and more stable,the oil concentration in the simulated water sample was basically stable at 202mg/L,the viscosity was 4 mPa·s,Zeta potential was-60.84 mV,the surface tension was 35.87 mN/m,the droplet diameter of the simulated water less than 10?m was70%,and less than 20?m was 100%?2?With high-speed microimaging and single drop method,the breaking velocity of oil droplets and the thickness of interfacial film were obtained by image processing software in the single system and the three element composite system.The effect of the rate of film thinning and the rate constant of the oil drop and the dosage of agent on the strength of the O/W type oil drop interfacial film were analyzed.In the composite system,with the increasing of alkali content,the interfacial film thinning rate and the rate constant decreased first and then increased;With the increasing of polymer and surfactant content,the thinning rate and rupture rate constant of oil droplet interfacial film decreased.The law of the action of the single system and the compound system converged.Surfactant should modify the stability oil-water interfacial film.The constant of oil-water interfacial film rupturing rate is 0.00182 s^-1with high surfactant concentration,while the rate of film thinning decreases to0.00512 mm/s.?3?The adsorption heat effect of oil surfactant at the oil/water interface and the simulation of intermolecular interaction were researched.Sodium dodecyl benzene sulfonate?SDBS?was used as surfactant for oil displacement.At the same temperature,SDBS concentration increased,the interfacial tension decreased,heat increased,system energy decreased,and the system tended to be stable;under the same surfactant concentration,with the increasing temperature,the interfacial tension decreased,the amount of heat gradually increased,and the adsorption heat value reached the maximum at 343 K.At this time,the system was the most stable.The results of molecular simulation showed that:the SDBS could form a stable monolayer at the dodecane/water interface,which has a good effect on reducing the interfacial tension of oil and water.By calculating the IFE,interface layer thickness,surfactant monolayer adsorption morphology and other parameters,the ability of surfactant to reduce the oil water interface at different temperatures were respective:343 K>353K>328 K>313 K>298 K.And the effect was strengthened with the increasing concentration.