Modelling a Transient Flow in a Well and Coupling it with the Flow in the Reservoir

It is now widely recognized that a correct reservoir model must incorporate a precise des cription of well physics. Multiphase flow distribution in a multi-layered reservoir depends on a good description of the bottom hole pressure evolution (time and space). The conventional methods used in most reservoir simulators perform the coupling of transient flow in the reservoir area with stationnary flow in the well. The model described in this paper performs the well calculations (from the bottom hole to the well head) in transient flow conditions (gas-water flow). Thus our simulator provides both a realistic well behavior and a correct description of the well reservoir exchanges. In the case of an imposed well head pressure, starting the well-flowing involves transient flow in both well and reservoir areas. In the diphasic case, the flow in the well is modeled with a one-phase equivalent fluid. METHOD: The Euler equations (in id, assuming energy constant and taking into account the friction term) are the equations governing the well flow. The well and reservoir coupling is perfor med through the massic flow rate exchange between the two areas and the continuity rela tion of the pressures on the welibore. A new implicit scheme derived from the ROE scheme has been developped to discretise the equations. Both efficiency and interest of our method are shown in real case-studies.