Research On Remediation Of Oil/Water Transition Layers In Oil Gathering And Transportation System

With the successive increase of water content, most oilfields have entered into the late development stage. So crude oil dehydration is the key procedure in the oil gathering and transportation system. In order to enhance dewatering rate and improve the quality of oil, many methods have been used in oilfields, such as thermal dehydration, electric dehydration, mechanical centrifugal dehydration, adding chemical reagent, ultrasonic dehydration and so on. The survey found that the quality of crude oil has been seriously affected as the existence of oil/water transition layers resulting in the dehydration of crude oil is not timely or inefficient. Therefore, we focus on analyzing the formation mechanism of oil/water transition layers, discussing its impact on crude oil dehydration and using the method of ClO₂ oxidation demulsification for the remediation of oil/water transition layers.The method of analysis and chemistry experiment was used in the research. Firstly, the structure and composition of the oil/water transition layers were analyzed and its formation mechanism. Then, the survey for the remediation of oil/water transition layers with ClO₂ oxidation had been performed. With the dewatering rate as target, the rules for temperature, stirring time, reaction time, acid volume and concentration of ClO₂ impacting on oil/water transition layers were researched. The best remediation option was determined with orthogonal experiment analysis,. In addition, causticity and security of the process of oil/water transition layers'remediation were discussed under the best option.The study found that oil/water transition layers is an oil/water emulsion which is formed under the joint action of natural emulsifiers, solid particle emulsifiers and polymers. The content of solid particle emulsifiers especially FeS is not much, but their existence decides the steady state of oil/water transition layers. The experimental results show that ClO₂ could effectively improve the dehydration rate of oil/water transition layers. The dehydration rate depends on stirring time, reaction temperature, reaction time, acid volume and concentration of ClO₂. For fresh oil/water transition layers, the dehydration rate could reach to 86% with option 55℃, stirring 5min, reaction time 4h, concentration of ClO₂ 10% and acid volume 0.3%. For aging oil/water transition layers, the dehydration rate could reach to 90% with option 50℃, stirring 5min, reaction time 5h, concentration of ClO₂ 15% and acid volume 0.5%. Under these conditions, the corrosion rate of corrosion is in the range of available standards (0.1 1.0 mm / a). Theoretically less residual ClO₂ content will ensure system safe on the condition of controlling well with the remediation process.