Rapid Pressure Waves Through Gas-Liquid Flow in Wells and Pipelines

Abstract

This paper was presented as part of the student paper contest associated with the European Petroleum Conference. Abstract A new computer model named MultiPress can predict rapid pressure transients in multiphase pipelines and wells. The model shows that pressure pulses behave similar in horizontal multiphase flow as in single-phase flow. In vertical wells there are strong non-linear effects because gas content, density and speed of sound vary down into the well. Introduction Rapid pressure transients in wells and pipelines are created if a valve is quickly closed or opened, and if a burst disk breaks. Leaks, ruptures, and blowouts can also induce such pressure waves. It is very useful to know how pressure transients propagate in the pipelines. Important applications are design of production system, leak detection and flow control, ref. 1-3. In single-phase flow there are robust theories concerning pressure transients ref.4, but for multiphase flow the problem is more complex. Traditional two-fluid programs do not model pressure pulses in an adequate manner. There are two main problems. Firstly the traditional two-fluid models do not give a correct description of the pressure propagation velocity. Secondly the numerical methods are usually of first order which means that they smear out the solution and loose the rapid pressure variations. This work presents a new computer program, MultiPress that predicts rapid pressure transients in multiphase wells and pipelines. The program is based on advanced numerical methods and knowledge about pressure pulse propagation in gas-liquid flow. Rapid Pressure Transients The traditional two-fluid models ref. 5, give a good description of the flow variables, but the rapid pressure pulses are not correctly treated. The problem is the interaction between the phases. Drift-flux models ref. 6, on the other hand, give a correct description of the propagation phenomena, ref. 7. The homogeneous approach ref. 6, is a simple drift-flux model assuming that the gas and liquid move with the same velocity.