Numerical Simulation Of Steam Assisted Gravity Drainage Based On TOUGH2

Steam assisted gravity drainage,as one of the most currently remarkable thermal recovery techniques for heavy oil,has been successively applied in many countries such as Canada,Venezuela and the United States.As a major oil sands resource country in the world,it is imperative for China to increase heavy oil production.Although China has made some achievements in the field of SAGD,it is still in its infancy.Therefore,it is of great academic value and economic significance to carry out the research on the mechanism and numerical simulation of SAGD.The main research contents and conclusions are as follows:(1)Firstly,the theoretical background of SAGD numerical simulation is reviewed and combed,and a dedicated Python module is developed independently for TOUGH2 post-processing,finally a complete simulation workflow is formed.The results show that the improved TOUGH2 has the preliminary ability to simulate the SAGD process.The heat and mass transfer and immiscible multiphase flow problems involved in SAGD can be solved successfully with the help of TOUGH2;(2)Secondly,a dual horizontal well SAGD numerical model is established based on the improved TOUGH2.The continuous numerical simulation of start-up stage and production stage in heavy oil recovery is carried out,the development law of two-dimensional section and three-dimensional steam chamber of SAGD is revealed,and the dynamic characteristics of SAGD recovery are analyzed and evaluated at the same time.The results show that the model can quantitatively analyze the dynamic spatial distribution of residual oil saturation and temperature,which is helpful to grasp the development dynamics of the whole production areas.The cumulative oil-vapor ratio under the recovery scheme is 0.188(greater than 0.13),and the recovery percent is 57%.This result demonstrated that the recovery scheme is economically viable;(3)Thirdly,according to the 6 main factors affecting the development effect of SAGD,the parameter sensitivity analysis is carried out.The physical mechanism of the parameters affecting the SAGD is deeply analyzed,and the reservoir parameters,injection and production parameters and well pattern parameters are optimized.The results show that the factors of vertical permeability and horizontal permeability ratio,oil saturation of reservoir and injection temperature are positively correlated with the SAGD development effect,while the factors of steam injection velocity,vertical well spacing and lateral well spacing have an optimal value,which means it is not appropriate whether it is too big or too small;(4)Finally,a comparative study of the development process and effect is carried out for two different cases of reservoir SAGD with and without mudstone interlayer.The results show that when there is a continuous horizontal mudstone interlayer between the injection well and the production well,it has a significant obstruction to the rising process of the steam cavity,and the peak oil production rate is reduced by 4%.TOUGH2 is a numerical simulator for nonisothermal flows of multicomponent,multiphase fluids in three-dimensional porous and fractured media.It is developed by the Lawrence Berkeley National Laboratory over the past half century,mainly for the field of hydraulics,including geothermal research.Through the secondary research and partial improvement of algorithm,this paper explores the application of pure source code to the simulation of SAGD for the first time.The results obtained so far have laid a solid analytical foundation for the subsequent realization of thermal-hydraulic-mechanical coupling and the attempt to study the combination scheme of geothermal recovery and heavy oil thermal recovery.