A Simulator for Gas Kicks in Oil-Based Drilling Muds

Abstract

ABSTRACT Mathematical techniques used in a newly developed simulator for gas kicks in oil based drilling fluids are presented. The simulator works in one spatial dimension. By deleting the material derivative term in the momentum equation, a quasi-stationary approximation is obtained, which does not contain (hyperbolic) pressure propagation effects. The equations are solved using a finite difference predictor-corrector shooting technique. Simple front tracking is employed for mud fronts and gas front. The simulator is very modular in its structure. For several effects, a number of alternative formulations are programmed. Effects included in the simulator are frictional pressure losses (one- and two-phase), pressure loss in bit and choke, rise velocity of free gas, dissolution of gas in mud (including non-equilibrium effects), pressure and temperature dependent densities. The simulator is equipped with interactive graphics, allowing the process to be observed and controlled (BOP, choke, pump rate, mud type pumped).