Study On The Law Of Superheated Steam Influencing Reservoir Physical Properties

The main methods of heavy oil recovery are steam huff and puff,steam flooding and insitu combustion of reservoirs.As an effective steam displacement technology,superheated steam SAGD(Steam Assisted Gravity Drainage)is becoming more and more mature and is gradually applied in oil field exploitation.Injecting superheated steam underground to heat heavy oil reduces its viscosity and increases its fluidity.At the same time,high temperature steam will also lead to changes in mineral composition of reservoir rocks,resulting in changes in porosity and permeability of reservoir rocks,and ultimately affecting heavy oil recovery efficiency.Previous literatures have found that hot water,wet steam,p H value and metal ion concentration can affect reservoir physical properties.The influence of high temperature superheated steam on reservoir rock physical properties is relatively less studied.Therefore,it is of great significance to explore the influence of superheated steam on reservoir rock physical properties for heavy oil recovery.In this paper,X-ray diffraction is used to analyze the composition of core minerals and single component combination before and after reaction,and to explore the reaction path.Under the condition of superheated steam at 250 ～400 ℃,the main reaction paths of core are: illite is formed by reaction of montmorillonite,kaolinite and quartz,chlorite and illite are formed by reaction of kaolinite,potassium feldspar and quartz.The core before and after displacement is tested by mercury injection experiment.It is found that the permeability and porosity of the rocks increase after displacement because of the change of the mineral composition of the core and the dissolution of quartz grains,which mainly constitute the framework of the rocks.It is also found that with the increase of superheated steam temperature,the permeability and porosity of rocks increase.With the increase of superheated steam injection rate,the permeability and porosity of rocks increase.The change of displacement temperature on rock permeability is more significant than that of displacement rate.After superheated steam flooding at different temperatures,core velocity sensitivity decreases.When the temperature exceeds a certain range,the velocity sensitivity changes from equal to weak,which indicates that the core velocity sensitivity decreases after superheated steam flooding.Superheated steam is beneficial to reduce reservoir damage.By compared the thermal conductivity of rocks before and after displacement,it is found that the thermal conductivity of rocks after displacement decreases because of the increase of porosity of rocks after displacement.The thermal conductivity of rocks before and after displacement decreases with the increase of temperature.