An Experimental Study On Viccosity Reduction By Emulsification Of LD Heavy Oil

With the increase of exploitation years,the output of terrestrial crude oil shows a decreasing trend,and the proportion of offshore crude oil gradually increases in the energy structure.China’s bohai sea area is rich in crude oil resources,among which more than 2/3 are heavy oil.Therefore,heavy oil will be the main object of China’s offshore oil field development.Compared with conventional crude oil,heavy oil has the characteristics of high viscosity,high density and high pour point,and special measures are often needed to improve its mobility during pipeline transportation,so as to improve transportation efficiency,reduce energy consumption cost and eliminate potential safety hazards.In this paper,O/W emulsification is adopted to reduce the apparent viscosity of heavy oil and improve the flow state for LD heavy oil.The main works and results are as follows:(1)The single emulsifier with better viscosity reducing effect was selected by measuring the viscosity and diversion ratio.Among several different emulsifier,non-ionic surfactant op-10 and anionic surfactant sodium oleate and SDBS had better emulsifying effect on LD heavy oil.Meanwhile,the influence of single emulsifier with different concentration on rheology,static stability and microstructure of O/W emulsion was investigated to determine the optimal concentration of emulsifying agent.The 1.00%was chosen as the best concentration.(2)The selected emulsifier was compounded and NaOH was added to further optimize the emulsifier formula.LD heavy oil has the best compatibility when the mass ratio of op-10 and SDSB is 4:1 in a binary system.NaOH has remarkable effect on the optimization of compound emulsifier.The O/W emulsion which prepared by 1.00%compound emulsifier and 2000 mg/L NaOH has good stability and the static diversion ratio for 24 hours is 17.8%and the viscosity reduction rate is 98.1%.Therefore,the final formula is that the total concentration is 1.00%,the mass ratio of op-10 and SDSB is 4:1 and the concentration of NaOH is 2000 mg/L.(3)The LD heavy oil O/W emulsion was prepared by using the scheme.The influence of oil-water ratio,emulsification time,stirring velocity and emulsification temperature on the apparent viscosity and static stability of the emulsion was discussed by using the control variable method and explained from the microstructure of emulsion.In the preparation of LD heavy crude oil O/W emulsion external factors should be kept as:oil/water ratio 7:3～8:2 and emulsification time 5 min,stirring speed 1000 r/min,emulsification temperature 30℃.(4)Taking the diversion ratio of LD heavy oil O/W emulsion at different salt concentrations as the index,the salt resistance of the emulsifier compounding scheme was evaluated,and the demulsifier with better dehydration effect was selected.Ca2+ and Mg2+ had significant effects on the stability of emulsion,and Ca2+ had more significa1t effects.Among the five alternative demulsifiers,the demulsifier with CaC12 mass concentration lower than 2.00%has good demulsifying effect on emulsion,with a dehydration rate of 96,2%at 180 min and a high clarity of the extracted water.Therefore,2.00%CaCl2 was selected as the demulsifier of LD heavy oil O/W emulsion.