Analysis Of Phase Distribution And Phase Transition On In-situ Combustion

The underground reaction temperature of In-situ Combustion(ISC)is high,which exceeds the conventional thermal recovery temperature.Therefore,intense phase change occurs,and the phase change will affect the displacement effect.As far as possible,understand the phases in each zone during the In-situ Combustion to understand the phase change rules in each zone as detailed as possible in order to ensure the accuracy and reliability of the site solution.This paper first compares and analyzes the quasi-component division methods in thermal recovery technology,summarizes the two main division methods of quasi-component division of crude oil,traditional composition division and group composition division,and summarizes the characteristics,application examples typical dynamic models of In-situ Combustion over the years of the two major methods.Finally,based on the characteristics of In-situ Combustion,a method of dividing firefighting pseudo-components based on reaction characteristics was proposed,and a numerical model of In-situ Combustion was established.The characteristics of typical In-situ Combustion zones were analyzed,and the characteristics of In-situ Combustion zones of crude oil with different properties were analyzed in contrast,phase-based fire flooding screening and design criteria are also given.Simulations show that the violent phase transition caused by the nature of crude oil reduces the maximum temperature of the In-situ Combustion and expands the range of heat,which leads to the enhanced In-situ Combustion effect in the same time.After successful In-situ Combustion,the lighter content in heavy oil,the more severe the phase change.The wider the area,the stronger the phase transition effect,to a certain extent,helps the reservoir to maintain pressure and increase formation energy.At the same time,the number of movable fluids increases,and the range of gas generated by combustion is wider.The effect of flue gas flooding is enhanced,and the oil recovery rate is increased.To improve recovery.The more the heavy component content,the slower the oil wall moves,and the shape of the oil wall changes from oblong to fat,but the oil saturation,temperature,and pressure increase;the more the heavy component content,the wider the condensed hot water zone The narrower,the slower the spreading speed,the higher the water saturation average value,temperature,and pressure;the water vapor zone moves faster than the oil vapor zone,and the location is closer to the production well.The steam zone plays a key role in the In-situ Combustion process,especially the gas-liquid phase at the junction of the steam zone and the condensing hot water zone becomes fierce,transferring a large amount of heat to the low temperature area;the larger the heavy component content,the wider the steam zone width.The larger the range,the higher the average temperature and pressure;the better the coking effect of the coking zone,the larger the coking area;the more intense the oxidation reaction in the combustion zone,the higher the CO2 content.the higher the average temperature and pressure,the basic the phase diagram shape of the combustion zone The same,the higher the inflection point temperature and pressure of the P-T phase diagram.After the reservoir succeeds,the larger the gas injection rate is,the lower the viscosity of crude oil is,and the effect is poor.When the viscosity of the crude oil is around 10,000 cp,the gas injection rate has less influence on the recovery effect,and the recovery factor does not change much.When the viscosity of crude oil is greater than 10000 cp,the effect of phase transition on the recovery efficiency of fire flooding is reduced.The article explores the mechanism of burning and flooding of heavy oil with different properties from the perspective of phase transition,and provides theoretical basis for the field production of fire flooding.