Scale formation and selection of scale inhibitors for water injection pipelines in Wangjiawan District of Xingzichuan Oilfield
Water injection development is one of the commonly used ways to enhance oil recovery in oilfields.However,during the process of the injection water being treated by the united station and transported to each water distribution room and single well wellhead,the scale and blockage of the water injection pipeline are serious;it shows a series of phenomena,such as the decrease of the effective inner diameter of pipelines,the decrease of the fluid transmission efficiency,and the increase of the injection pressure.In order to solve this problem,this paper takes the scale formation of water injection pipelines in a united station of Xingzichuan Oilfield as the research object and uses X-ray diffractometer to determine the type of scale sample.Sewage water samples at different nodes in water injection process and compatibility tests were combined,and the causes of pipeline scaling were analyzed.According to the scale characteristic,the optimization and evaluation experiments of scale inhibitors were carried out using the static scale inhibition method.The research results indicate that the reinjection water from Chang2 contains a large amount of Ca2+and HCO3-,and there is a serious tendency for scaling on its own;at the same time,the suspended solids would interact with CaCO3 precipitation to form a scale mainly composed of CaCO3 and containing a small amount of SiO2 and silicates if their contents do not meet the standard after water treatment.Green and environmentally friendly polymer scale inhibitors were selected and their optimal concentration was determined through experiments.The scale inhibition rate of on-site injected water reached 91.62％at scale inhibitor is 60 mg/L.Based on this,on-site dosing measures for scale inhibitors were proposed,which can effectively solve the problem of oilfield water scaling;it also provides a certain technical reference for on-site scale prevention in the same type of oilfield reinjection water pipeline.
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