Analysis Of North Shaanxi Crude Oil And Study Of Its Chemical Demulsification Mechanism

In order to enhance oil recovery in North Shaanxi Oil fields,water and polymer flooding is used so that water content in crude oil is increased,compositions of crude oil emulsion become more complex and problems of crude oil demulsification and dehydration are increased.In order to understand crude oil demulsification and dehydration and select correctly demulsifiers,study of crude oil demulsification mechanism is needed.The inorganic anions and cations in representative crude oils of Cui Ge Lao 12 well,and Nian Zhuang 107 well,and Nian Zhuang 206 well,and Zichang 2 well,and Zichang 1006 well in northern Shaanxi oil field are analysed.The content of resin,asphalt and wax of intermediate layer producted with crude oil demulsification and dehydration is mensurated.Distribution of polyether in oil-water two phase is determinate.Electric property of crude oil emulsion is tested.The complex of metal ion in the crude oil and polyether as demulsifier is synthesized to explained demulsification mechanism.Determination of inorganic anions in crude oil by extraction-ion chromatograp hy.The representative crude oils from Cui Ge Lao 12 well,Nian Zhuang 107 we ll,Nian Zhuang 206 well,Zi Chang 2 well,Zi Chang 1006 well in Northern Sha anxi oil field were respectively dissolved in xylene,and the inorganic salts were extracted by ethanol,acetone and water from the solutions of the crude oils in xy lene.The contents of fluoride,chloride,bromide,nitrite,nitrate,sulfate and phosp hate in the inorganic salt solutions are determined by ICS-900 ion chromatograph.AS9-HC anionic analysis column is used as ion exchange column,and a mixtureof 4.5×10-3mol·L^-1sodium carbonate-8.0×10-4mol·L^-1 sodium bicarbonate is used a s eluent.It is indicated by experiment that the inorganic salts in North Shaanxi o il are mainly chlorides and its contents in crude oils of Cui Ge Lao 12 well,Nian Zhuang 107 well,Nian Zhuang 206 well,Zi Chang 2 well,Zi Chang 1006 we ll are 324.3?g·g^-1,21.83?g·g^-1,19.45?g·g^-1,2.210×104?g·g^-1,1.673×104?g·g^-1 respect ively,and It is also indicated that One of the reasons that dehydration of the cru de oil emulsion from Zi Chang block is more difficult than others is its higher c ontents of the chloride and bromide than others.For six sample injections,the RS D of retention times is between 0.18% and 0.52%,the recovery of inorganic anio ns is between 95.60% and 103.0%.Contents of inorganic cations that are sodium,vanadium,manganese,nickel,t ungsten,magnesium,aluminum,zinc,arsenic,strontiun,zirconium,cadmium,alead,bismuth,barium,calcium,chromium,molybdenum,iron,copper,cobalt in norther n Shaanxi oil field are determinated by dry ashing and inductively coupled plasm a atomic emission spectrometry?ICP-AES?.According to SH/T0715-2002 standard,Representative crude oil samples from Cui Ge Lao,and Zi Chang,and Nian Zh uang oilfield blocks in northern Shaanxi oilfield are ashed in quartz beaker.the s amples are mixed with concentrated sulfuric acid in quartz beakers,and they are heated by infrared ray lamp and heating plates to be ashed.And then ashed samp les are heated for 3 hours at 525 ?in the furnace to be completely ashed.The completely ashed samples are dissolved by dilute nitric acid and contents of indiv idual elements are determinated by ICP-AES.And precision,and the recovery of the method were determined.Results show that contents of Na,Ba,Al,Ca,As,Fe,Bi,Pb,Ni,Cr,Sr,Mg,Cu,Zn,Mo,V,Zr,Cd,W,Mn decrease in turn,co ntents of Na,Ba,Ni,Pb,Cr is Zi Chang > Nian Zhuang > Cui Ge Lao oilfield block,and contents of Mg,V,Zn,Cu,Al,Fe is Zi Chang > Cui Ge Lao > Nia n Zhuang oilfield block.Higher content metal elements in northern Shaanxi oil ar e Na,Ba,Al,and Ca.The contents of Na,Ba,Al,Ca,Pb,Ni,and Cr of Zi Ch ang 1006 well,Zi Chang 2 well are higher than other oilfield block wells.In order to understand where polyether demulsifier is after crude oil demulsification and dehydration,distribution of polyether demulsifiers in oil-water two phases was studied by KI-I2 spectrophotometry.Results show that the same polyether demulsifiers are more dissolved in Nian Zhuang 206 well water,less Zi Chang 2 well dissolved in water,and distribution coefficient of polyether demulsifiers in oil-water two phases for the crude oil from Nian Zhuang 206 well is less than 1.The distribution coefficient of TP4016080 polyether demulsifier is the smallest in several used polyether demulsifiers,and the coefficients of Zi Chang 2 well and Nian Zhuang 206 well are all less than 1.In crude oil demulsification and dehydration,demulsifier and metal ion form positive charge complex which has surface activity,the positive charge of the complex neutralized negative charge of interface double electric layer of liquid drop leads to flocculation and Coalescence of liquid drops.In order to proved this mechanism,the complex is synthesized by metal ion in crude oil and demulsifier polyether.For example,at room temperature,five-membered ring complexes are synthesized by Ca²⁺ and polyethylene glycol and by Ca²⁺ and triethylene tetramine at 60 ?.