Open Access

ARTICLE

A Multiphase Wellbore Flow Model for Sour Gas “Kicks”

by Miao He, Yihang Zhang, Mingbiao Xu, Jun Li

1 Yangtze University, School of Petroleum Engineering, Wuhan, 430100, China
2 Hubei Cooperative Innovation Center of Unconventional Oil and Gas, Yangtze University, Wuhan, 430100, China
3 China University of Petroleum, Beijing, 102249, China

* Corresponding Authors: Yihang Zhang. Email: ; Mingbiao Xu. Email:

Fluid Dynamics & Materials Processing 2020, 16(5), 1031-1046. https://doi.org/10.32604/fdmp.2020.011145

Received 22 April 2020; Accepted 24 August 2020; Issue published 09 October 2020

Abstract

This study presents a new multiphase flow model with transient heat transfer and pressure coupling to simulate HTHP (high temperature and high pressure) sour gas “kicks” phenomena. The model is intended to support the estimation of wellbore temperature and pressure when sour gas kicks occur during drilling operation. The model considers sour gas solubility, phase transition and effects of temperature and pressure on the physical parameters of drilling fluid. Experimental data for a large-diameter pipe flow are used to validate the model. The results indicate that with fluid circulation, the annulus temperature with H₂S kicks is the highest, followed by CO₂, and CH₄ is the lowest. The phase transition point of H₂S is closer to wellhead compared with CO₂, resulting in a faster expansion rate, which is more imperceptible and dangerous. With fluid circulation, the drilling fluid density and plastic viscosity both first decrease and then increase with the increase in the well depth. The bottom hole pressure when H₂S kicks is greater than that for CO₂ with the same amount of sour gas, and the pressure difference gradually increases with the increase of H₂S/CO₂ content. In addition, a parametric sensitivity analysis has been conducted to evaluate qualitatively and rank the influential factors affecting the bottom hole temperature and pressure.

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Keywords

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