Study on Factors Affecting CO2 Recovery of Fractured Pressure-sensitive Reservoirs

Abstract

The different deformation degree of fractures caused by the intrinsic strong pressure-sensitive property of the ultra-low permeability reservoirs would change the channeling law of CO₂ in fractures, then affect the oil displacement efficiency. Thus, revealing the seepage characteristics of CO₂ in fractured reservoirs is the groundwork to improve the oil displacement efficiency of CO₂. The directional pressure-sensitive property of fractures was simulated by a physical model. The simulation of physical experiment with multi-physics coupling was carried out by theoretical derivation and finite element analysis software COMSOL Multiphysics. The stronger heterogeneity of reservoirs , makes CO₂ much easier to rush. Increasing injection pressure , can increase the proportion of CO₂ in low permeability area. As the pressure-sensitive property between high and low permeability layer is different, increasing the effective stress would induce stronger heterogeneity. Therefore, in order to control the effect of pressure-sensitive property on production，the formation pressure should be controlled reasonably in development process. In this study, the factors, especially the fracture development directions, which show significant influence on the oil recovery of CO₂ flooding in fractured and pressure-sensitive reservoirs, were studied with physical experiments and numerical experiments. The results obtained in the study can provide a more reliable theoretical basis for CO₂ flooding design and profile control technology.

Keywords

• CO2 flooding,pressure-sensitive,fracture direction

Study on Factors Affecting CO2 Recovery of Fractured Pressure-sensitive Reservoirs

Abstract

The different deformation degree of fractures caused by the intrinsic strong pressure-sensitive property of the ultra-low permeability reservoirs would change the channeling law of CO2 in fractures, then affect the oil displacement efficiency. Thus, revealing the seepage characteristics of CO2 in fractured reservoirs is the groundwork to improve the oil displacement efficiency of CO2. The directional pressure-sensitive property of fractures was simulated by a physical model. The simulation of physical experiment with multi-physics coupling was carried out by theoretical derivation and finite element analysis software COMSOL Multiphysics. The stronger heterogeneity of reservoirs , makes CO2 much easier to rush. Increasing injection pressure , can increase the proportion of CO2 in low permeability area. As the pressure-sensitive property between high and low permeability layer is different, increasing the effective stress would induce stronger heterogeneity. Therefore, in order to control the effect of pressure-sensitive property on production，the formation pressure should be controlled reasonably in development process. In this study, the factors, especially the fracture development directions, which show significant influence on the oil recovery of CO2 flooding in fractured and pressuresensitive reservoirs, were studied with physical experiments and numerical experiments. The results obtained in the study can provide a more reliable theoretical basis for CO2 flooding design and profile control technology.

Keywords

• CO2 flooding,pressure-sensitive,fracture direction

References

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