The Coupled Models Of Thermo-Hydro-Mechanical And Its Applications In Heavy Oil Recovery

Steam injection is an important heavy oil recovery method.In the high temperature steam injection process,the interaction between Thermo-Hydro-Mechanical coupling mechanism and reservoirthermodynamics is the basic issue to be solved for the current development of this field.In this research,based on a comprehensive consideration of coupling relationship between fluid seepage,temperature and reservoir deformation involving in the thermal recovery process,a Thermo-Hydro-Mechanicalcouplingmathematical model of wellbore-reservoirsystem has been established,and parts of the problems within heavy oil thermal recovery projects have been studied.The main contents include:1 The thermal recovery project of heavy oil involves a wellbore-reservoirsystem,in this paper,the wellbore-reservoirsystem is decomposed into two relatively independentand interrelated subsystems:thermodynamic system of borehole water vapor(steam)pipe flow,thermodynamic systemof reservoir thermal mass transfer(seepage/convection).Both the thermodynamic model of wellbore for parameter analysis and the heat transfer model of reservoir flow have been established,and the thermodynamic conditions linking two subsystems have been given in the paper;2 Based on the continuum mechanics and Thermo-Hydro-Mechanicalcoupling theory,the mathematical models of wellbore-reservoir under the interactionbetweenthree main parameters(temperature,pressure and skeleton deformation)has been studied separately,and the variation law of temperature,pressure,effective stress with different steam injection condition has been analyzedquantitatively by using the finite element numerical simulation method,as well as theformation inspiratory process and the diffusion range.It is demonstrated by comparative study of numerical examples as the flowing: in heavy oil thermal recovery process,due to the skeleton rock deformation caused by high temperature steam injection,porosity and permeabilitymake changes,which takes significant effect on the thermal recovery result,the spread scope will expand with the increase of permeability,and the production will be improved.3 According to the stress damage theory of sandstone,the reservoirskeleton damage model has been established,which may happen during steam injection,and the pore pressure and skeletal stress caused by temperature have been analyzed by examples,we find that,the best steam injection rate should take both the efficiency and wellbore/formation into account.4 In thermal recovery wells,there exits water/steam gravity separation and steam overlay phenomenon,based on the water/steam mixing mechanism and parameter study of pipe string-wellbore flow,by using the method of model simulation,physics experiments,engineering design and others,a vapor two phase mixerfitted with a uniform flow injection composite string structure is designed,and improved in production.5 For the shale interlayer fracture problem of Haqian 1 field during SAGD recovery project,in this paper,a thermal recovery rupture test platform is built to carry out the high temperature/non-uniform stress test of artificial cement mortar samples,cement mortar natural cores and wrapped cores and other natural specimens,considering the complex condition of wellbore temperature and reservoir stress during steam injection,a rupture test device for thermal recovery reservoir is developed,which offers physical foundation for quantitative evaluation of shale reservoirs in steam injectionconditions.