A fully implicit EOS based compositional two-phase transient flow simulator in wellbores

Abstract

Transient two-phase flow in pipes and wellbores appears in several processes in petroleum industry. Predicting pressure, temperature and composition behavior during offshore well tests can support investment decisions in exploration. The governing system of equations that model production (or injection) and build-up (or fall off) is composed by the mass conservation of each component, the transport equation for each phase and one overall system energy equation. In this paper we develop a fully implicit equation of state based thermal compositional simulator able to model two-phase multicomponent flow in wellbores and pipes. This simulator is fully compositional and includes thermal effects. The thermodynamics calculations are based on the Peng-Robinson equation of state, and the momentum equations are based on the Single-Pressure Two-Fluid model. The finite volume method is used to discretize the non-linear system of equations, and time is discretized using Euler's implicit technique. The obtained numerical solutions for both co-current as well as countercurrent flow showed excellent agreement when compared to benchmark solutions published in the literature. A well kick-off followed by constant flow rate production and posterior shut-in was also simulated and the numerical results were discussed. It also models surge pressure and gravitational segregation effects in the wellbore. The presented simulator may be applied in numerical pressure transient analysis and pressure behavior in flowlines connecting wellheads and production platforms.