Molecular Weight Grading Method And Flooding Properties Of Polymer Surfactant

Polymer surfactant flooding is a new technology to improve oil recovery after polymer flooding,which has strong viscosity and profile control performance,and dual function of emulsifying and displacement.Influenced by the polymerization process,there exists a wide distribution range of the molecular weight of the polymer surfactant used in oil field.Grafting density,grafting rate,grafting type and number of active groups may be quite different among components with different molecular weight,which affect the performance of oil displacement in turn.Therefore,it is necessary to carry out molecular weight separation,study on the viscosity,emulsification and displacement performance of the different molecular weight components,which will play a guiding role in the synthesis of polymer surfactant and oil field experiments.Double gradient elution and precipitation method are adopted to classify the components of polymer surfactant according to the relative molecular weight,which obtain the molecular weight distribution,and different molecular components are separated quickly and efficiently.FTIR spectra and 1HNMR analysis of components with different molecular weight indicates that the different components occupy similar molecular structure,and the difference lie in the molecular weight and content of hydrophobic group in unit mass.The solution properties of components after separation are compared and analyzed.After separation the viscosity under the same concentration decrease,and especially the micro-molecule component.SEM analysis demonstrates the aggregation morphology and viscosifying mechanism of different components intuitively.Salt resistance of BI is superior to B?,in the same salt concentration,viscosity of micro-molecule and macro-molecule polymer surfactant are lower than that of sample before the separation.BI type polymer surfactant has stable viscosity performance,and viscosity retention rate is high,while stable performance decline after separation.At the same temperature,concentration and salinity conditions,BI bears better the viscoelastic properties.Under the condition of different polymer surfactant concentration and the ratio of water to oil emulsion of polymer surfactant is oil in water type,the emulsion particle size decreases with the increase of the concentration;after the separation,emulsion particle size of macro-molecular polymer surfactant increases at a certain degree,and that of micro-molecule will decrease,but the distribution of emulsion particle size remain the same.The emulsion stability increase with the increase of concentration,and decrease with the increase of W/O ratio.Macro-molecular emulsion stability decreases,while the stability of micro-molecular emulsion increase.Micro-molecule is more conducive to the stability of emulsion system.Micro-molecule contains more active groups,the emulsion viscoelastic properties are better than that of the macro-molecular emulsion.Core flooding experiments show that BI is better in flow control and B? is better in displacement efficiency.The EOR effect of the different components is as original sample is better than micro-molecular component,while macro-molecular component performes worst.Furthermore,the fluid distribution and flow pattern of different components are studied by CT core scanning imaging and experiment of microscopic model,which reveals the mechanism of EOR.