Study On The Visbreaking Behavior Of Heavy Oil By Aquathermolysis

Aquathermolysis is a new technology for heavy oil recovery,which is based on thermal recovery of heavy oil exploitation,especially for the heavy oils with higher sulfur contents.Usually the sulfur compounds in heavy oils play an important role in the process of aquathermolysis and the thiophene is studied as a model compound to study the role of sulfur compounds in the process of aquathermolysis.Experments of aquathermolysis were carried out using crystallization kettle and effect of influence factors was studied through experiments of single factor.The properties,structure and composition of heavy oil were measured by IR,NMR,elemental analysis,rheometer and other analytical methods.Sulfur compounds were analyzed before and after reaction using the XANES method.Effect of additives on aquathermolysis was studied.The sulfur content of Shanjiasi heavy oil is 2.32wt%,The amounts of resin and asphaltene were 52.56%,they also contain a large number of aromatic rings which are pericondensed and alkyl side chains.The main structures of sulfur groups in asphaltene are thiophene and thioether,Sulfide reacts in aquathermolysis.Shanjiasi heavy oil is Bingham liquid which has a certain yield value when temperature is between 40 to 80 degrees celsius.The viscosity reduction rate after aquathermolysis increased when temperature and time increased.The presence of catalyst and water has a greater impact on aquathermolysis.Ferrocene and nickel naphthenate which are oil-soluble are better than ferrous sulfate and nickel sulfate which are water-soluble.The effect of nickel naphthenate is better than ferrocene.Optimal concentration of ferrocene and nickel naphthenate is 0.2%,the viscosity reduction rates were 71.35% and 65.59% respectively.In the absence of catalyst,the optimum dosage of water was 40% as well as the catalyst is ferrocene or nickel naphthenate.Because of the side chain cleavage reaction and fracture reaction of alkyl bridge between ring system,the molecular weight of resin and asphaltene in heavy oil decreased as well as the content of resin and asphaltene after reaction of heavy oil,while the contents of saturate and aromatic increase,which leads to viscosity reduction and improvement of flow ability.The effect of nickel naphthenate to promote side chain cleavage of asphaltene and resin is better,while ferrocene has a better effect on side chain cleavage of resin.Different metal ions have a better catalytic effect on different structures,so it is reasonable to devise a catalyst that uses different metals.In the experimental condition,it is found that the content of sulfide decreases a lot,while the thiophene type decrease a little.Hydrogen donor can reduce the content of heavy component and increase the content of saturate and aromatic after reaction.Surfactant makes it easier that water,oil and catalyst contact each other,which leads to a higher viscosity reduction rate.