Transient pressure analysis and interpretation for analytical composite model of CO2 flooding

This work deals with the inverse problems of parameters estimation for mass transfer during CO2 injection in oil reservoir. Such method is based on well testing theory which monitors reservoir dynamic performance through transient pressure. In this paper, considering the skin and storage effect of well, three-region composite transient pressure analysis model for CO2 flooding is established by introducing pseudo pressure for real gas, and then non-dimensional transport equations for each region are derived and solved analytically by the method of Laplace transformation. According to the type curves of the model pressure, fluid flowing in reservoir can be divided into seven stages, and the flowing factors׳ effect on curve shape is discussed too. Then relevant parameters during mass transferring can be achieved by type curve matching field testing data. We also provide a new method for parameter matching during testing data interpretation through feature points׳ analysis, which facilitates the matching process and reduces ambiguity of parameters estimation.