Mechanistic Time Dependent Modeling & Simulation of Underbalanced Drilling Operations ( A Case Study)

Underbalnaced drilling is a drilling method stands on keeping bottomhole pressure below formation pore pressure which leads to formation fluid(s) production under a controlled situation# this paper presents an advanced dynamic model and computer simulation using commercial multiphase flow simulator (olga) for underbalanced drilling# the model is formulated based on the theory of multiphase transient flow referring to the drilling mud, water, oil, gas# many of important factors affecting underbalanced drilling have been taken into account comprehensively in the model, including ipr relation, physical properties and mass transfer behavior of fluids, flow regime and phase migration features, geometry and deviation of wellbore as well as the different operating modes which may be carried out in practical underbalanced drilling# through a number of simulating computations, tests and verification, it is shown that the model and dynamic multi phase flow simulator (olga) give acceptable results in accordance with an actual drilling practice#