| Improving oil recovery rate is the consistent goal of petroleum industry, especially to heavy oil reservoir. It is widely known that the classic method to recover heavy oil is steamflooding. To overcome the steam override, steam channeling and poor oil recovery rate of hot water zone, thermal/chemical combined oil recovery technology was developed in 1980's. Although many works have been done, the study in this field is still at earlier stage. Nowadays the mechanism of this technology has not been well interpreted. There was not a perfected mathematic model to describe thermal/chemical combined oil recovery technology.In this paper, we have investigated the characteristics of thermal/chemical combined oil recovery technology based on experimental, theoretical and numerical studies. The mathematical model was developed and this model was solved using numerical method. The numerical simulation software of thermal/chemical combined oil recovery technology was programmed. The main points of this paper are as follows.(1) The experiments including the tests of physical-chemical properties of surfactants under the condition of high temperature and thermal/chemical combined flooding performance were conducted. Mathematical model can be developed based these experiments. The results showed that surfactant decreased interfacial tension (IFT) between oil and water, changed the rock wettability and the relative flow between oil and water, and increased oil recovery rate eventually. For most favorable systems, incremental oil recoveries from steam flooding to thermal/chemical combined flooding up to 19.65% were achieved. Surfactant spices, concentration, grounder water properties, high temperature, and so on affect the effects of surfactant.(2) The experiments of oil/water relative permeability of surfactants flooding were conducted. The effects of temperature and interfacial tension on relative permeability were discussed. According to the experiment results, an empirical model was developed to describe the oil/water relative permeability of high temperature-low tension system. The parameters of this model were explicit function of temperature and interfacial tension. The results showed that the predicted values of this model were in good agreement with experimental data.(3) According to the mechanisms of surfactant adsorption, thermal degradation and chemical reaction of surfactants with mineral ions, a model of surfactant transport inporous media saturated by oil and water was presented. This model considered more factors reasonably than foreigner's model and could describe the real surfactant transport process in the core. The model was solved using finite difference method coupling with oil-water mass conservation equations and energy conservation equation. The effects of temperature, displacement velocity and slug size on surfactant transport process were discussed. Surfactant adsorption at the solid-liquid interface was modeled with Langmuir-type model and surface excess model, respectively. The surface excess model was firstly used to study surfactant adsorption under multiple-phase flow condition.(4) According to the mechanism of thermal/chemical combined oil recovery technology, three-dimensional, multiple-phase and multiple-component model of this combined oil recovery technology was developed. Phase equilibrium and effects of temperature and interfacial tension on multiple-phase flow in porous media were considered in this model. The model is more perfect and more reasonable the foreigner's model. The models were solved using finite difference method. The difference equation set was solved combined simultaneous solution method and step solution method. That is means the thermal recovery model was solved by fully implicit method and the surfactant transport equation was solved by implicit method. Model calculations indicate that the algorithm of the software is stable and the process is relative sample.(5) The software for three-dimension, multiple-phase...
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