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Abstract

A two-phase model has been developed for analyzing and designing gas/condensate distribution pipeline network system. The model is developed based on looped system approach with some modifications. In this model, a phase behavior model is implemented for predicting the fluid properties required for the governing equations for the network system. By utilizing the Linear Theory Method, the Beggs-Brill's two-phase flow model is implemented in this model to predict the hydrodynamic variables in each leg of the network using the iterative technique which is developed in this study. A generalization of the two-phase network model is provided thereby making it possible for the two-phase flow model used to be replaced with any other that may be more applicable for the particular situation. Using the iterative procedure developed, pressure at all nodes, gas flow rate and liquid holdup at each leg can be predicted. The test results demonstrate that the model can serve as a predictive and design tool for solving a two phase flow problem in a pipeline network.

Introduction

The increasing role of natural gas as an energy source, especially in the non-transportation sector of an industrial economy, cannot be over-emphasized. It is also certain to play a major role in the transportation sector of the economy as the technology of natural gas-driven engine improves. This dramatic increase in gas utilization will necessitate the transportation of higher volumes of natural gas than ever before. This implies a critical need for a more efficient utilization of the existing network of pipelines. Optimal design and operation of the gas pipeline is in the essence. A very important complicating factor in the design of a gas pipeline network is the fact that condensation invariably takes place in these pipelines. The introduction of liquid into a gas pipeline subjects it to two-phase flow.

The use of pipelines for gathering and transportation of natural gas is standard. Condensation in these gathering lines is a common occurrence because of the multicomponent nature of the gas which is subjected to varying temperature and pressure. In general, the phase behavior of natural gas is quite sensitive to pressure, temperature and composition. Thus, the amount of condensate formed in the gas-carrying pipeline is dependent upon these variables. What this means is that gas may enter the pipeline as single-phase gas but invariably becomes to contiguous phases somewhere within the pipeline network due to condensation. Furthermore, since the slope and pipeline network due to condensation. Furthermore, since the slope and orientation of the pipeline varies, the effect of gravity must also be taken into consideration. It is therefore imperative to utilize a compositional approach in trying to model this system. It is now a fact generally recognized in the gas industry that the adequate design of gas pipelines requires a good knowledge of the impact of condensation on the pipelines requires a good knowledge of the impact of condensation on the basic design and operating parameters which, in turn, would affect the deliverability of the pipeline in question. The problem of two-phase flow in pipes and conduits in complex even when flowing in a single pipe. pipes and conduits in complex even when flowing in a single pipe. P. 18-1 P. 18-1

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