Transient flow modeling of advanced wells

A new approach to combined transient well flow and reservoir flow modeling is presented with focus on advanced well completions. It is intended for efficient optimal well design. The model is formulated to handle concurrent and countercurrent flow in tubing, annulus and in the reservoir, and for flow between the well and the reservoir. Both frictional and acceleration pressure losses are included. The model together with its time–pace discretization is presented and demonstrated in four separate case studies. In Case 1, the remote reservoir is modeled as a tank which is coupled to the near well region. The coupled model is transient in all parts of the system. It is concluded that reservoir flow along the well trajectory in general cannot be neglected. In Case 2, the numerical model is validated against an analytical solution for flow in a semi-infinite pipe. In Case 3, transients in both material and momentum are included. It is concluded that a fully transient approach must be used for very early transients. In Case 4, consideration is given to two-phase flow of oil and gas. It is noted that the transient vaporization of oil at decreasing pressures is correctly captured by the model.