Well test analysis of low velocity and non-Darcy flow in composite reservoir with dynamic boundary

Low velocity and non-Darcy flow exists in low-permeability reservoirs near the wellbore. Various kinds of stimulation treatments make the physical properties of the formation and fluid surrounding and far away from the well different. Thus the vadose area of low permeability reservoir can be divided into two zones: near wellbore zone and distant wellbore zone, which make it a composite reservoir. Based on the low velocity and non-Darcy flow theory, a well testing model is established in composite reservoir with full consideration on the effect of threshold pressure gradient and dynamic boundary, and it is solved by numerical discrete method. Then the characteristic curve and the propagated rule of the dynamic boundary of the model are gained and analyzed. The results show that the pressure derivative in log-log well test plot in distant wellbore zone and near wellbore zone does not stay level, but goes upward gradually. At early stage of dynamic boundary propagate, the situation of dynamic boundary R D and the dimension time t D have a good linear relationship. In middle and late stage, R D 3 and t D have a good linear relationship.