The Study Of Decalcification From Calcium Rich Crude Oil

In recent years,with the application of the tertiary recovery technology,the calcium content in the crude oil become higher and higher.Excessive calcium content has a negative effect on refinery operation.In industry,the chelating calcium technology combining with electric desalting process is mainly used.Therefore,it is necessary to select suitable decalcifying agents,optimal operating conditions of decalcification.In this experiment,the crude oil is from Xinjiangchunguang oilfield.Frist,the basic properties of crude oil,the distribution and composition of calcium were analyzed.Second,the experimenter used HEDP,B,N-330,AA/AMPS,nitrilotriacetic acid,A,EDTA and glacial acetic acid reacting with calcium to measure their decalcification ability and do some theoretical analysis.At the same time,the operating conditions and process of decalcification were studied.The research results show that the crude oil from Xinjiangchuangguang oilfield is heavy,acid and calcium rich.The 94 to 96 percent of calcium is concentrated in resin and asphaltene and the polarity of the calcium compounds is very high.The 72 percent of calcium is organic,the 99.55 percent of calcium is ionized and the all calcium is porphyrin.It was also found that these organic calcium was mostly the naphthenic acid calcium which have high branched degree and short side chains.The decalcification effect of the mixed decalcifying agents was better than that of single agent.A and B were chose as a component of the decalcifying agent,and when the mass ratio of A and B was 2:1,the decalcified effect is best.By experiment,when the optimum operation conditions of decalcification was: the dosage of decalcifying agents was 6000 ?g/g,the rate of injection water was 20%,the reaction temperature was 90?,the stirring time was 5 min and the settling time was 10 h,the decalcification rate can reach 92%.It is concluded through the orthogonal experiment that the influence of various factors on decalcification rate was in the order: the dosage ofdecalcifying agent>the rate of injection water>the reaction temperature>the stirring time.Using primary desalination,secondary desalination and triple decalcification,the decalcification rate was high to 94%.Finally,the density,viscosity,the content of Ca,Fe,salt decrease,the content of Ni and V remained unchanged,and the acid value was increased.The content of oil in discharge water can reach 14 ?g/g,the content of Ca,Fe and water hardness significantly increased,and the pH value reduced.