Study On The Fast Determination Of Sodium Dodecyl Polyoxyethylene Ether Sulfate And Its Loss During Adsorption

Most of China's oilfields use chemical flooding to increase oil recovery.Foam flooding is one of the chemical flooding methods.Shengli oil field has researched and developed the foaming agent and applied it for field tests of foam flooding.The main component of the foaming agent is sodium dodecyl polyoxyethylene ether sulfate,a nonionic-anionic surfactant with the chemical formula C₁₂H₂₅?OC₂H₄?_nOSO₂ONa.Accurate detection of sodium dodecyl polyoxyethylene ether sulfate can not only control the amount of foaming agent injected into the wellhead to reduce costs,but also monitor the outflow concentration of foaming agent at the production wellhead and then infer the foaming agent's migration conditions under stratum.It has extensive application value.In this dissertation,reversed-phase chromatography,reversed-phase ion-pair chromatography,quaternary ammonium type strong anion exchange chromatography,and imidazole ion chromatography were used to separate the oilfield injection fluid sample,then UV-Vis detector and refractive index detector were used to detect sodium dodecyl polyoxyethylene ether sulfate.It was found that the four methods have the disadvantage of having a high detection limit and cannot be used for actual sample detection.Finally,a liquid chromatography-mass spectrometry detection method was established for the detection of sodium dodecyl polyoxyethylene ether sulfate in oil field injection fluids,and the sensitivity was improved by electrospray ionization mass spectrometry.The results showed that the minimum detection limit of this method was 2 mg/L,the analysis time was short,and the repeatability was good.The detection results were not affected by polyacrylamide,high-concentration inorganic salts,and crude oil and other interferences.Sodium dodecyl polyoxyethylene ether sulfate will undergo adsorption loss during the flooding process.Therefore,based on the established detection method,the rules of its'adsorption on oil sands and other substances were studied,in order to provide reference data for foam flooding experiment in the laboratory,and design a more reasonable oil displacement agent formulation.The results showed that the static adsorption capacity of 5000 mg/L sodium dodecyl sulfate sodium sulfate on kaolin,montmorillonite,oil sand and quartz sand were 0.77 mg/g,2.17 mg/g,1.73 mg/g and2.09 mg/g;the static adsorption of sodium dodecyl alcohol polyoxyethylene ether sulfate on the oil sand reaches adsorption equilibrium after 8 hours;the adsorption amount decreases with increasing temperature;and increases with increasing salinity and increasing polyacrylamide concentration.