Experimental Study On Surfactant-assisted Hydrocarbon Gas Huff-n-Puff In Heavy Oil Reservoirs

A considerable portion of heavy oil reservoirs at home and abroad suffered from a serious problem,that the oil recovery remained low because of reservoir adaptability and the limitations of development.For the past few years,anomalous performances occurred in the primary production process of some unconventional heavy oil reservoirs: low production GOR,high oil production rates,high oil recovery.Foamy oil behavior was validated to be one of the reasons.However,foamy oil cannot be formed in all the heavy oil fields.In addition,the rheological properties and flow characteristics of foamy oil are very complicated.Therefore,it is necessary to apply this mechanism into recovery of convetional heavy oil fields.This paper presented a new enhanced solvent injection technique,called the surfactant-assisted hydrocanbon gas huff-n-puff method.In this process,an oil-soluble foaming agent and hydrocanbon gas were injected in a cyclic manner,but in separate slugs.The methane provided the solution gas drive energy,and most propane stayed in the oil to keep the oil viscosity low.The presence of the foaming agent promoted the formation of in situ foamy oil.A new experimental procedure was also developed to prove that the selected foaming agent had an effective foaminess in convetional heavy oil,and investigate the effects of various process parameters on foamy oil stability.Moreover,a statistical approach was utilized to ensure reliability of the experimental data.Finally,we proposed a new method to describe foamy oil rupture and simulate its defoaming kinetics.The experimental results showed that foamy oil stability increased with higher surfactant concentration,higher heavy oil viscosity,higher asphaltene and resin concentration,lower temperature and smaller gas bubbles size.