On the basis of fluid distribution of carbon dioxide flooding in low permeability reservoir, the flowing areas are divided into CO₂ region, CO₂-oil transition region and oil unswept region. Considering the power law variation of fluid physical parameters in the transition region, we establish a varied property carbon dioxide flooding three-zone composite reservoir well testing model, and obtain the solution of bottom hole pressure by applying Laplace transform and Stehfest numerical inversion. In this way, the characteristics of variation of the well testing curve and influential factors are investigated. The results show that the slope of curves representing the transition section between the CO₂ region and transition region and radial flow of the transition region is mainly affected by the power law exponent of mobility and storativity and mobility and storativity ratio in the CO₂-transition region interface. The larger the storativity power law exponent and storativity ratio at the CO₂-transition region interface is, the earlier the transition section between miscible region and oil unswept region begins, the lower the peak is. When the radius of the transition region is increased, the line of radius flow in the transition region becomes longer, the transition curve from the transition to oil unswept region shifts right, and CO₂ injection pressure decreases.

low permeability reservoir  /  CO₂ flooding  /  three-zone composite reservoir model  /  well testing curves