The Synthesis Of An Oil-soluble Heavy Oil Viscosity Reducer And Its Effect On Asphaltene Gum

With the continuous decrease of reserve and production for conventional crude oil,the exploitation of heavy oil has been increasingly important in our country.The characteristics of high viscosity,high freezing point,poor flowability and other issues make it hard to exploit it,so reducing viscosity and improving flowability are the key,and oil-soluble flow improver is one of the important research directions.Based on the current study of the viscosity-reducing mechanism of flow improver,using pentaerythritol,octadecanol and phthalic anhydride as reactants,toluene as a water-reagent,p-toluenesulfonic acid as a catalyst to synthesis a small-molecule oil-soluble flow improver with long-chain alkyl groups and polar groups.Using tetradecyl alcohol,cetyl alcohol and octadecanol to instead the octadecanol in relatively good monomer ratio,and synthesize flow improver with mixed long chains.Through viscosity-temperature relation and crude oil four-component analysis,a high-viscosity crude oil with a lower content of asphaltene and resin was selected.According to the viscosity-reducing effect to know the relative better monomer ratio is 0.0050mol,0.0100mol and 0.0100mol and the best viscosity-reducing effect at 500 ppm is 61.10%.using GC-MS to analysis the carbon number distribution of n-alkanes in the saturated of crude oil.The tetradecyl alcohol,cetyl alcohol and octadecanol were used to instead the octadecanol in relatively good monomer ratio to synthesize flow improver with mixed long chains,which the best viscosity-reducing effect at 500 ppm is 65.10%.It showed that the viscosity-reducing effect can be further improved as the long-chain composition of the flow improver is more matched with the composition of the carbon number distribution of n-alkanes in saturated of crude oil.Through viscosity-temperature relation and crude oil four-component analysis,a high-viscosity crude oil with high asphaltene content and resin content was selected.According to the viscosity-reducing effect to know the optimal single factor conditions:the optimal addition dosage was 100 ppm,the optimal monomer molar amount,pentaerythritol:octadecanol:phthalic anhydride=0.0015mol:0.0100mol:0.0066mol,the optimal amount of catalyst p-toluenesulfonic acid was 0.07g,the optimal amount of water-carrying agent toluene was 1.0g,the first step experiment temperature was 90?,the time was 2.5h,the second step experiment temperature was 110?,the time was 1h.Under 50?,flow improver dissolved in toluene solution and a dosage of 500ppm can reduce the apparent viscosity of the heavy oil by 53.76%.The flow improver was characterized by infrared spectroscopy and gel permeation chromatography.Through analyze the effect between flow improver and asphaltene/resin respectively to explore the mechanism of the viscosity reduction.Scanning electron microscope(SEM)were used to observe changes of morphological features of asphaltene and resin before and after the addition.Through added n-heptane and alcohol as poor solvent to asphaltene and resin solution respectively to configure 8 concentrations of solution samples and analyze the precipitation tendency.The microscope was used to observe the aggregation morphology changes of asphaltene particles and resin particles before and after the addition.Using UV-Vis spectrophotometer to test the 8 kind of sample solution,the result showed the flow improver has a stronger dispersive effect on the resin than the asphaltene.X-ray diffraction(XRD)was used to test the structure change of colloid samples before and after the addition.The elemental analyzer was used to analyze the content of C,N and S in the asphaltene and resin,the results indicated that the C and N elements in the asphaltene were less than the resin,while the S elements were 8 times of the resin,indicating that the asphaltene contain more aromatics and naphthenic substances and has stronger intermolecular forces.In summary,this kind of small-molecule flow improver has a better viscosity-reducing effect on the heavy oil used in this experiment and has different effects on different asphaltene and resin.