Interface Properties And Rheological Properties Of Active Crude Oil Based On Emulsifiers With Different Structures

In oilfields developed by water injection,water production from oil wells is a common problem.And it will consume formation energy,affect crude oil recovery,and increase the workload of dehydration of produced fluid.In order to reduce the water production of oil wells,the most direct way is to block the water in oil wells.Among many chemical plugging agents,each plugging agent has its own applicable scope of implementation.Although many plugging agents are selective,they cannot truly block water without damaging the oil layer.Active crude oil is a liquid dispersion type of plugging agent,which is a selective water plugging technology with low construction cost,good water control and oil enhancement effect,and no damage to the oil layer.The crude oil added with emulsifier is called active crude oil.The emulsifier can be dissolved or dispersed in the crude oil by stirring.It was found that the effect of implementing active crude water plugging varies greatly due to the different crude oil and emulsifiers in different oil field blocks,which limits the promotion and application of this technology to a certain extent.Therefore,it is necessary to study the matching relationship between the crude oil components,properties and emulsifier structure used in water plugging of active crude oil,as well as the interface and rheological properties of active crude oil emulsion to improve the success rate of active crude oil water plugging.Therefore,the structure of emulsifier,crude oil composition and component,oil-water interface performance,stability and rheological characteristics of active crude oil emulsions with series of emulsifiers were studied by combining modern analysis methods such as spectroscopy,chromatography,and rheology in this thesis.And the mechanism of active crude oil water plugging was also clarified according to the results of microscopic visualization experiments and core water plugging experiments.The specific research contents and results are as follows:?1?Two kinds of crude oils with different apparent properties were selected as the research object,and the relationship between crude oil family composition,component structure and crude oil rheological properties was analyzed.It was shown that the crude oil components of 1#and 2#are similar.The carbon numbers of saturated alkanes are distributed in C₁₂?C₃₆,and the content of C₁₈ and C₁₉ is relatively high.The number of aromatic rings of aromatic hydrocarbons and colloids is mainly concentrated in 3?5 rings in two kinds of crude oil.There are more low-ring components in the colloids and aromatic hydrocarbons of 2#crude oil than that of 1#,which is conducive to the dissolution and dispersion of asphaltenes in crude oil.The content of colloids and asphaltenes in 2#crude oil is higher than 1#crude oil,and 2#crude oil has higher viscosity and loss modulus.?2?The active crude oil was prepared with nonionic Span surfactants as emulsifiers,which has the same hydrophilic end groups and different lipophilic group structures.Through interface and rheological analysis,it was found that with the growth of the carbon chain,the strength of the Span active crude oil-water interface film increases significantly.The presence of double bonds in the Span80 molecular structure also contributes to the improvement of the interface film strength.The active crude oil interface film composed of Span80 and 2#crude oil with high colloid and asphaltene content has high strength,and the emulsion has high shear resistance,viscosity temperature performance and viscoelasticity.?3?Active crude oil was prepared by using cardanol surfactants with the same lipophilic end groups and different ion types and structures of hydrophilic group as emulsifiers.Through interface and rheological analysis,it was found that the charge characteristics of hydrophilic end groups have an effect on the performance of the oil-water interface.Cardanol quaternary ammonium salt cationic surfactant can stabilize the oil-water interface and improve the strength of the oil-water interface film by electrostatic interaction with the negatively charged colloid and asphaltene in the crude oil component.It can form W/O emulsion,which has relatively high shear resistance,viscosity temperature stability and viscoelasticity.?4?Taking the polymer surfactant with both polymer and surface active characteristics as the research object,the oil-water interface performance,emulsification stability and rheological properties of five different kinds of polymer surfactant were studied.It was shown that type?polymer surfactant with relatively small molecular weight and strong emulsifying ability can emulsify with crude oil to form multiple emulsions and significantly improve the shear resistance and viscoelastic properties of the emulsions.?5?Using the epichlorohydrin-dimethylamine series cationic polymers with dual characteristics of cationic groups and polymer chains as emulsifiers,the oil-water interface performance,emulsification stability and rheological properties of the series of cationic polymers active crude oil were studied.It was shown that polyepichlorohydrin-dimethylamine with high cationicity,relatively small molecular weight,and low branching degree can undergo electrostatic interaction with the negatively charged colloids and asphaltenes in the crude oil component.Electrostatic adsorption cooperated with the bridging and intercalation of polymer molecular chains can stabilize the oil-water interface film and significantly increase the strength of the interface film.The active crude oil emulsion prepared from 2#crude oil with high content of colloids and asphaltenes and polychloroprene-dimethylamine has high viscosity and good viscoelasticity,and has emulsion stability and rheological stability.?6?The micro-visual displacement system was used to observe and analyze the state of channels in ideal model and simulation model before and after the active crude oil injection.The water blocking mechanism of active crude oil was clarified.First,when the emulsified droplets are larger than the pore throat,the emulsified droplets can deform and block the pores and pore throats;when they are smaller than the pore throat,the"Jamin"effect of small droplets can block.Second,the emulsified droplets are adsorbed on the wall of channels,the radius of the channel decreases,and the resistance to water flow increases.?7?Micro-visual displacement experiments were carried out on the active crude oil optimized by interface and rheological analysis.The experimental results showed that Span80,cardanol cationic surfactants and polyepichlorohydrin-dimethylamine active crude oils can all emulsify in the model pores,and the crude oil with high asphaltene and colloid content has a strong emulsification blocking.The core water plugging experiment showed that the three active crude oils have obvious water blocking effects.The non-ionic surfactant Span80,cardanol cationic surfactant and polyepichlorohydrin-dimethylamine can all be used as emulsifiers for the active crude oil preparation.The average increase value of oil recovery is11.22%,6.24%and 18.27%respectively.?8?The plugging selectivity experiments of saturated medium and permeability showed that active crude oil has obvious plugging selectivity.Active crude oil can preferentially block pores with high permeability and large water content.It does not block oil-containing pores,and can significantly improve recovery.Active crude oil plugging is a water-reducing and oil-increasing technology that can automatically adapt to the formation environment.