Research Of Coupled Thermo-hydro-mechanical Law Of Heavy Oil Reservoir

Our country owns abundant heavy oil resources, and heavy oil resources have been effectively explored and utilized in every major oilfields. Seeing heavy oil exploitation, thermal recovery is always chosen as the main development method. However, injection of high temperature steam or hot water could dramatically changes the temperature system of the reservoir, other physical properties of oil and fluids are changed at the meantime. During the processes of heavy oil development, because of the tremendous changes of temperature, the effects of temperature on rock frame could not be ignored, and the formation will involve in complex coupled thermo-hydro-mechanical.In order to fix out the underground conditions related to coupled thermo-hydromechanical, through a series of physical experiments, effects of temperature on strength properties of rock(compressive strength properties and shear strength properties), rock deformation characteristics, porosity, permeability and influence on physical properties of formation fluids are researched. Through the uniaxial compression test and triaxial compression test, mechanical parameters of rock under different temperature are measured. With the usage of the coaxial cylinder rotary rheometer, the changes of fluid’s viscosity in relation to temperature are studied. And the effects of temperature and effective stress on rock porosity and permeability are learned by rock compressibility apparatus and core flow test instrument.Basing on laboratory experiments listed above, state equations of fluids and rock could be established. Basing on the law of conservation of mass and the law of energy conservation as the basis, combined with the stress-strain relationship of rock under various temperature and fluids flow equations etc, it’s also possible to establish coupled thermo-hydro-mechanical mathematical model of heavy oil reservoir which includes seepage control equation of oil and water, rock deformation control equation and temperature field control equation, then all the coupling equations could be solved using the fully coupled algorithm combined with definite condition and initial condition. The model we established is a fully coupled model, we can find parameters of other two fields in every control equation.After its certification, the coupled mathematical model could be used to the numerical simulations for the mechanism study. Here we observe changes of three fields by changing temperature of the injected fluid, injected pressure and permeability of formation, in order to studying how these three fields affect each other.By comparing the distributions of three fields under thermal-hydro-mechanical and hydro-mechanical two conditions(considering the effects of temperature or not), the production indexes could be predicted, all works above will provides a theoretical foundation for practical applications.