Heat And Mass Transfer Model For Expanding Solvent-SAGD Process And Its Application

Recently,the heavy oil reservoir is still one of the most important and promising petroleum resources.Due to the high viscosity of heavy oil,it is always recovered by the steam-injecting method.To increase the heavy-oil production rate and reduce the greenhouse gas emission during the steam-injection process,Enhanced Solvent SteamAssisted Gravity Drainage method(ES-SAGD),in which solvent and steam are coinjected into the reservoir,has been proposed.Although the ES-SAGD has been effective to some extent in the field,the promotion and application of the method are limited by some factors,which are the unclearance of the heat-and-mass-transfer mechanism at the chamber edge,the inaccuracy characterization of the heat-and-mass-transfer process,and the lack of the synthetical assessment of ES-SAGD.In this thesis,the equilibrium state at the chamber edge is firstly determined,then it is combined with the distributions of temperature and mass to analyze the heat transfer mechanism by the theoretical study.Meanwhile,the mass transfer mechanism of solvent at the chamber edge is revealed by conducting a series of experiments and numerical simulations.Then,the steam chamber is divided into steam-swept and horizontal-wellbore regions and the characterization of heat and mass transfer process in each region are conducted.As for the steam-swept region,a mathematical model for the temperature and saturation distributions is firstly established,the results of which are compared with those of simplified methods in the literature.As for the horizontal-wellbore region,the mathematical model coupling the phase change and heat-and-mass transfer in the wellbore and from the wellbore into the formation is developed for the determination of properties profiles in the wellbore.According to the heat and mass transfer at the chamber edge,the calculation method for the shape of the SAGD chamber edge is established,with which the influences of chamber shape on the oil production rate and on the heatloss rate are clarified.On the basis of SAGD chamber calculation method,the heat-andmass-transfer mechanism at the ES-SAGD chamber edge,together with the temperature and saturation distribution characterization method,a comprehensive mathematical model for the evolution of ES-SAGD chamber is developed.Finally,by simultaneously applying the horizontal-wellbore properties-profiles computing method and the comprehensive mathematical model for the evolution of ESSAGD chamber,the chamber shape,oil production rate as well as the steam-oil ratio are calculated and analyzed for different solvents injections.Based on the calculation results,taking into account the greenhouse gas emission and cost of injection,a synthetical evaluation method is established.With this synthetical assessing method,the critical oilprice environment and the technical conditions,when the conventional SAGD could be replaced by the ES-SAGD,can be finally determined.This thesis is of great theoretical significance in predicting injection-production performance and synthetically assessing ES-SAGD process.