T2Well - An integrated wellbore-reservoir simulator

We have developed T2Well, a numerical simulator for nonisothermal, multiphase, multicomponent flows in integrated wellbore-reservoir systems. The new model extends the existing numerical reservoir simulator TOUGH2 to calculate the flow in both the wellbore and the reservoir simultaneously and efficiently, by introducing a special wellbore subdomain into the numerical grid. For gridblocks in the wellbore subdomain, we solve the 1D momentum equation of the mixture (which may be twophase) as described by the Drift-Flux Model (DFM). The velocity of the mixture is calculated by solving the momentum equation numerically, while the individual phase velocities are calculated from the mixture velocity and other fluid parameters as defined by the DFM. A novel mixed implicit-explicit scheme is applied to facilitate the solution of the momentum equation within the Newton-Raphson iteration framework of TOUGH2. Specifically, the pressure gradient, gravity component, and time derivative of momentum are treated fully implicitly, whereas the spatial gradient of momentum is treated explicitly. The friction term is calculated with a mixed implicit-explicit scheme. Applications of the new simulator to problems in various fields are presented to demonstrate its capabilities.