Study of Displacement Characteristics of CO2 in Tight Sandstone Reservoir by Nuclear Magnetic Resonance

The displacement oil characteristics of different pressure of carbon dioxide(CO2) in cores of different permeability and core with fracture of tight sandstone reservoir are studied by nuclear magnetic resonance(NMR) technology. This paper briefly describes the principle of nuclear magnetic resonance(NMR) and the experimental method. The results show that the tight sandstone reservoir, low and ultra-low permeability core in the initial CO2 displacement pressure,core capillary pores rang and micro capillary pores rang of oil is produced different degree,with CO2 displacement pressure increased, oil recovery degree of core capillary pores rang is increase and cumulative recovery degree is different. Tight sandstone reservoir core with fractures,oil of fractures and the part of oil in capillary pores range in the initial CO2 displacement pressure is displacement, with CO2 displacement pressure increased, oil recovery degree and cumulative recovery degree is smaller in core capillary pores rang and micro capillary pores rang. When CO2 displacement pressure increased, the part of oil of core capillary pores range is proportional to the increase into micro capillary pores rang in tight sandstone reservoir, low and ultra-low permeability cores and fracture tight sandstone reservoir core and change the distribution of residual oil. Thus it is concluded that the nuclear magnetic resonance(NMR) technology can further study of oil recovery degree and the distribution of residual oil under different displacement pressure of CO in capillary pores rang and micro capillary pores rang of tight sandstone reservoir, for the tight sandstone reservoir microscopic oil displacement mechanism is of important value.