Experimental Study On Catalytic Upgrading And Viscosity Reduction Of Offshore Heavy Oil Platforms

High density and high viscosity of heavy oil has great difficulty in heavy oil recovery and transportation.The high contents of resins and asphaltenes in heavy oil are the main reason of high density and high viscosity of heavy oil.At present,Bohai heavy oils are mainly transported by sea pipes.But the low temperature of sea water makes the energy eonsumption of the technology high.At present,the main methods of viscosity reduction include Dilution,Heating,Emulsification and Upgrading.Dilute needs to consume a large amount of light oil resources,Heating needs to add insulation facilities along the pipeline with high energy consumption,and there are difficulties in demulsification of heavy oil.Considering the limit space of off shore production platform,shortage of light oils,high nenrgy consumption,difficulties of pipeline transportation,it is difficult to achieve viscosity reduction for the three viscosity reduction methods of heavy oil.Upgrading can destroy the molecul structures of heavy oil,and reduce the viscosity of crude oil irreversiblely.Catalytic upgrading of heavy oil is a research hot spot,which greatly faelilitate the transportation of heavy oil.Two heavy oils LD and NB uesd in this paper were provided by Liaohe oilfield and Bohai offshore oilfield,respectively.And the effects of heavy oil composition on viscosity of heavy oils were discussed.In this paper,two kinds of oil-soluble catalysts were synthesized,optimum catalysts and their optimum reaction conditions were selected by catalytic upgrading experiments of heavy oil NB.Catalytic mechanisms were inferred by analyzation of components changes of heavy oil.Two kinds of oil-soluble catalysts were synthesized and catalytic upgrading experiments of heavy oil NB were conducted under the reaction condition(mass fraction of catalysts 0.12%,reaction temperature 340oC and reaction time 30 min),two optimum catalysts PASF and FASF were selected.The optimun reaction conditions of two catalysts were discussed:mass fraction of catalyst PASF 0.125%,reaction temperature 360?and reaction time 40 min,mass fraction of catalyst FASF 0.1%,reaction temperature 370?and reaction time 40 min.The viscosities of upgraded oil were decreased from 2167 mPa·s to 113 and 279mPa·s with PASF and FASF,whose viscosity reduction rates were 94.78%and 87.12%,respectively.The optimum reaction conditions of heavy oil NB were selected using continuous upgrading installation:mass fraction of catalyst PASF 0.125%,reaction temperature 400? and reaction time 40 min,mass fraction of catalyst FASF 0.125%,reaction temperature 410? and reaction time 40 min.The viscosities of upgraded oil were decreased to 456 and 500 mPa·s with PASF and FASF,whose viscosity reduction were 78.96%and 76.93%,respectively.Experiments have proved the greatly viseosity reduction of heavy oil by PASF and FASF,the changes of the properties of upgrading heavy oils were analyzed with rising contents of saturates,aromatics and asphaltenes,and decreasing contents of resins.Catalytic mechanisms of two catalysts were inferred by analyzation of components changes of heavy oil.Resins are the main reaction parts of heavy oil upgrading,when the temperature rises to the reaction temperature,the Fe3+can catalyze the cracking reactions of side chain,aromatic system and the bonds with low energy such as C-S bonds in the resins and asphaltenes,resulting the increase of saturated fraction and aromatic fraction in heavy oil,sulfur?contents and CO2.etc.in tail gas.At the same time,some saturated fractions cracked into some hydrocarbon with lower molecule weight.