The D Oilfield of the Bohai Sea is a typical extra-heavy oil reservoir.This kind of heavy oil has poor fluidity under formation conditions,and the development effect of conventional steam huff and puff is poor.Auxiliary chemical synergism is needed to improve the development effect.Through a one-dimensional high-temperature displacement experimental device and a high-temperature and high-pressure micro-displacement physical simulation experimental device,indoor physical modeling experiments have been used to study the process of steam compound chemical synergism and thermal composite chemical enhancement mechanism.It is found that steam composite chemical flooding can significantly improve the recovery rate of extra heavy oil,and its mechanism of increasing production is reflected in the use of steam heat to reduce viscosity,the aid of chemical agents to reduce viscosity,and the improvement of steam utilization rate through plugging control.Compared with single steam flooding,the oil displacement efficiency of steam composite chemical flooding has increased by 16%.The viscosity-reducing agent in the steam composite chemical system can dissolve the gum and asphaltene in heavy oil,and the viscosity-reducing rate has reached 70%.The yield value is significantly reduced to change the rheology of heavy oil and reduce the starting pressure,which is conducive to the flow of extra-heavy oil in the reservoir.Under the condition of 120℃,the steam composite chemical synergism can reduce the oil-water interfacial tension to the level of 10-5mN/m,which can improve the oil displacement efficiency.In addition,the foam can also seal the high-permeability layer and increase the oil displacement efficiency of the low-permeability layer by 15%.The research results provide theoretical guidance for developing offshore extra heavy oil efficiently.
offshore extra heavy oilthermal compound chemistrysynergistic mechanismviscosity reductionplugging
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