# Numerical Analysis of Rapid Gas Decompression From a Pipeline In Different Natural Gas Mixtures Under Low Temperature Conditions And Water Presence In a Pipe

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OnePetro

ABSTRACT

The paper presents a one-dimensional transient mathematical model of compressible thermal two-phase flows of multi-component gas mixture and water in pipes. The set of the mass, momentum and enthalpy conservation equations is solved for the gas and water phases. Thermophysical properties of multi-component gas mixture are calculated by solving the Equation of State (EOS) model. The Soave-Redlich-Kwong (SRK-EOS) model is chosen. Gas mixture viscosity is calculated on the basis of the Lee-Gonzales-Eakin (LGE) correlation. The proposed mathematical model is successfully validated on the experimental measurements of rapid decompression in conventional dry natural gas mixtures at low temperature and shows very good agreement with the experimental data at high and low pressure. The influence of the temperature and water on rapid gas decompression process is investigated numerically by using the proposed mathematical model. Numerical results show that the model predicts the decompression wave speed in dry natural gas mixtures much better than GASDECOM and OLGA codes, which are the most well-known and frequently used codes in oil and gas pipeline transport industry.

INTRODUCTION

New technologies on natural gas production require more intensive gas transmission from one place to another one. A rupture in pipelines happens and brings numerous problems for oil and gas engineers. The fracture propagation control in gas transport pipeline service is performed by using the Battelle two-curve method, which was developed by the Battelle Columbus Laboratories in order to determine the fracture arrest toughness (Eiber et. al., 1993, 2004). The fracture propagation speed in the pipeline wall material and the decompression wave speed in gas mixture are required to be employed in the Battelle analysis. The fracture propagation is arrested when the decompression wave speed in gas mixture is quicker than the fracture propagation velocity in the pipeline wall. Therefore, the information on the decompression wave speed in different gas mixtures at different pressure, temperature and water fraction is very important in fracture propagation control.

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ISOPE-I-12-072

June, 2012