Understanding the Mechanisms of H2S Production During SAGD Processes Using Compositional Thermal Reactive Reservoir Simulation

Steam Assisted Gravity Drainage is a popular EOR method to recover heavy oil and bitumen. It consists of injecting steam to decrease the oil viscosity in the reservoir. During this process, the steam reacts with the oil due to the high temperature leading to the emission of the corrosive and highly toxic H2S if the oil contains sulfur. These reactions are called aquathermolysis. Understanding the mechanisms leading to H2S generation in the reservoir and to its resulting production at surface is of paramout importance for field operators in order to properly design their surface facilities and respect the environmental regulations. This study aims at providing more insights into these mechanisms. In particular the H2S generation and its distribution among the gas, oil and water phases in the reservoir have been investigated as well as its production process at well. Sensitivity analyses of H2S emissions on the injection temperature and the reservoir permeability have also been investigated. Overall this work illustrates the complex interactions between chemical reactions, thermodynamics equilibria and multiphase flows occuring in the reservoir and gives further insights on the mechanisms leading to the H2S production and its variation at the wellhead during the lifetime of a SAGD project.