Investigation on the water-coning control by CO2 injection in strong bottom water reservoir

The crestal CO2 injection can be used to control the flow of water in a strong bottom water reservoir. Pressure-Volume-Temperature and relative permeability studies were done under formation circumstances (50 MPa, 110 degrees C) to elucidate the mechanism of water-coning regulation. The findings of the PVT test demonstrated that CO2 might shift the water phase downward, so regulating water-coning and lowering the viscosity of the oil, thereby preventing water break. The results of the relative permeability test indicated that CO2 could reduce the relative permeability of brine, increase the relative flow capacity of crude oil, form a CO2-oil miscible bank concurrently, increase the efficiency of oil displacement by water flooding, and inhibit the formation of water-coning. An appropriate strong bottom-water block was chosen as a trial location for evaluating the water-coning control by CO2 injection. The results suggested that crestal CO2 injection was more successful in reducing water cut than the basic gravity effect. The results also indicated that CO2 injection is a more effective method of controlling water-coning than water plugging.