STUDY ON THE WELLBORE TEMPERATURE SENSITIVITY DURING FORMATION H2S INVASION IN OIL-BASED DRILLING FLUIDS

摘要

With the deepening of oil amp; gas reservoirs exploration and development,an increasing number of sour-gas reservoirs especially those with high content of hydrogen sulfide (H2S) are developed in the world.Considering the temperature sensitivity of H2S,there is a big error if the temperature and heat transfer are neglected in the drilling process,and the kick or blowout is easy to occur,so it’s necessary to put forward the research study on the temperature sensitivity during formation H2S invasion in oil-based drilling fluids.In view of the special physical properties of H2S and its phase transition in the wellbore,a mathematical model for wellbore flow and heat transfer during formation H2S invasion was established and a solution method of the model was proposed,and the wellbore temperature,pressure and H2S physical properties were coupling calculated.The effect of choke temperature and geothermal gradient on the depth of phase transition and bottom-hole pressure were analyzed,and the results indicate that the bottom-hole pressure reduces but the depth of phase transition increases with the increase of the choke temperature and geothermal gradient.The wellbore pressure and flow influenced by the heat transfer were analyzed and compared in the paper.The study is of certain significance for improving the safety of acidic oil amp; gas reservoirs exploration and development.