Experimental and Simulation Study of Solvent Injection to Heavy Oil Fractured Reservoirs

In this work a series of first contact miscible solvent injection process are conducted on horizontal glass micromodels at several fixed flow rate conditions. The micromodels are initially saturated with the crude oil. The produced oil as a function of injected volume of solvents was measured using image analysis of the provided pictures. The concentration calibration curves of solvents in crude oil were used for evaluating the solvents concentration. Several fractured with constant width and non-fractured five-spot micromodels were used. The experimental measurements have been used for verifying and developing of a simulation model which later used for sensitivity analysis of solvent injection process. The results show that when the fracture spacing and solvent injection rate are increased, the oil recovery decreased. The oil recovery increased as the fracture orientation angle and solvent viscosity increased. Small connate water saturation can even be advantageous in this process. A threshold value for the ratio of connate water saturation to the oil volume has been found which beyond that the process loses its efficiency. The oil recovery after water alternating solvent (WAS) injection process in fractured medium in presence and absence of connate water saturation are considerable greater than that is obtained either by continues solvent injection or water injection alone. If the system is modelled to be dual porosity, even with continues solvent injection scenario, the early breakthrough of injection solvent yields in smaller recovery factor than the dual permeability case. In the case of water alternating solvent (WAS) injection process for dual porosity model molecular diffusion mechanism would become stronger and increase ultimate recovery by delaying injection solvent breakthrough to production well.

Keywords:

Micromodel , Simulation , Solvent , D ual porosity , Dual permeability , Fractured porous medium , Five-spot model , Crude oil