Study on the wellbore flow and phase transition during formation H<SUB align="right">2S invasion

Abstract

Considering the special physical properties of hydrogen sulphide (H2S) and its phase transition in the wellbore, a mathematical model for wellbore flow and heat transfer during formation H2S invasion was established. Heat transfer and pressure were calculated along with H2S physical properties parameters, and a solution method of the model was proposed. The results indicate that liquid H2S transforms into gas state during its rising process in the annulus when choke pressure is low; the flow above phase transition point is two-phase flow while the flow below phase transition point is single-phase flow in the annulus. The paper exhibits the results and the reasons of the bottom-hole pressure and the depth of phase transition varying with different H2S influx rate, injection rate, choke pressure, and land surface temperature. The study is of certain significance for improving the safety during the exploration of acidic oil and gas reservoirs.