Simulation of thermochemical sulfate reduction of gaseous hydrocarbons in Wushenqi area, Ordos Basin, China

Prediction of the H2S distribution is critical to lower the risks during petroleum exploration and development in the exploration area. Natural gas of two wells produced from the Ordovician Majiagou Formation Ma5-6 section from Wushenqi area show great difference in H2S content. To investigate whether the different thermal maturity of the two wells contributes to the different H2S content, the thermal mature history and transformation ratio of gas hydrocarbons and sulfate into H2S and CO2 through TSR (thermochemical sulfate reduction) were simulated by using Petromod 2016. Simulation result shows that difference of thermal maturity of the two wells is about 0.6%. Propane and butane have all been consumed to generate H2S. The transformation ratio of ethane is higher for the well with higher thermal maturity. The high H2S content in the well with high thermal maturity and no H2S in the well with lower thermal maturity was not caused by the different thermal maturity. Some other geological factors should be considered.