Demulsification Of Polymer Flooding Produced Fluids In Bohai Oilfield

Polymer flooding is an important technology in tertiary oil extraction, which has been used in lots of oil fields in China and abroad. However, as it's newly used in offshore oil in China, some relevant technologies to deal with the produced fluidies by polymer flooding in Bohai oil field are necessary. As a result, the mainly work purpose is for synthesis some effective demulsifiers for the produced fluidies in Bohai oil field based on the polymer flooding.In this thesis, the mainly investigated contents are as follows:Firstly, a series of stable simulated polymer flooding produced fluids were prepared in the laboratory, which based on the crude oil emulsions characteristics of SZ36-1 oil field in Bohai.Secondly, five kinds of different structures demulsifiers named CM, CN, RFQ, PCA and PS respectively were synthesized, furthermore the demulsification efficiency of them was then evaluated by the polymer flooding produced fluids.Thirdly, some of the demulsifiers and intermediate were analyzed by the MS,GPC and ~1H NMR, and then combined with the demulsification results to optimize the structures and improve the efficiency of demulsifiers.Fourthly, the relationship between demulsification structures and efficiency was studied by the dynamic interfacial tension measurements from the example of RFQ02 and PS02.Fifthly, the influence of water content, polymer content and polymer structures to the demulsification of simulated polymer flooding produced fluids were studied by both the macroscopical and microcosmic methods, such as the optic microscope, scanning electronic microscopy (SEM) and interfacial tension (IFT) measurements.The obtained conclusions are as follows: Firstly, the two block polyether demulsifiers, which the molar ratio between polyethylene oxide (PEO) and polypropylene oxide (PPO) is from 1:4 to 2:3 and the precursor contents is 0.5 wt%, give optimal performance to polymer flooding produced fluids in Bohai oil field.Secondly, the star-structures demulsifiers (PS) showed excellent demulsification capability due to its higher branches and stronger interfacial adsorption capacity, which induced molecules arrayed loose on the oil-water interface, and formed weaker interfacial membrane, as a result, easy to demulsify.Thirdly, polymer AP-P4 which used in Bohai oil field presented high interfacial activities and could decrease the IFT of crude oil emulsions, finally, the dehydration ratio decreased with increasing polymer concentration, and the separated water got cloudy.Forthly, not only the simulated polymer flooding produced fluids but also the produced fluids from A7 oil well in Bohai, can be well treated by the PS demulsifiers. It is an effective demulsifiers to solve the separation difficulties from polymer flooding in offshore oil field, and better than BH01 which used in Bohai oilfield at the present time.Fifthly, as the hydrophobically associating water-soluble polymers exhibited significant viscosity enhancing capacity and high interfacial activities, the presence of them increased both the viscosity of emulsions and the intensity of interfacial film, in which case slow down the diffusion of demulsifier molecules and enhance the stability of emulsions, finally, the separation of water from oil becomes more difficult.