Forecasting of H2S Production due to Aquathermolysis Reactions

Abstract

Abstract Steam injection has been recognized as an efficient process for recovering hydrocarbons from heavy oil and bitumen reservoirs. However, it is now well known that the steam injection induces chemical reactions within the reservoir, called aquathermolysis and yielding acid gases. Hydrogen sulfide (H2S) being highly toxic and highly corrosive, even at low concentrations, it is of major importance to forecast H2S production. However, until now, there are only very few publications relating reservoir simulations of steam injection processes accounting for thermal and compositional effects in a chemically reactive context. The proposed paper relates a work focused on H2S production forecast during a SAGD process from aquathermolysis experimental results and simulation. After a description of the aquathermolysis experiments, the simplified sulfur-based kinetic model deduced from the experimental results is presented. This sulfur-based kinetic model has been used to build a thermo-kinetic component-based model usable in a compositional and thermal reservoir simulation. A simulation of the experimental aquathermolysis reactor being run for validating the thermo-kinetic model, the simulation results of H2S production and oil SARA composition versus time are shown to be in good agreement with the experimental results. Then, the thermo-kinetic modeling has been input in a cross-section model designed for simulating a SAGD process. The H2S production results were found to be consistent with published field data. The work related in the paper contributes to provide a new insight to the simulation of H2S production by aquathermolysis, through the presentation of a simplified modeling of the aquathermolysis reactions, and the description of a methodology for building an EOS (Equation Of State) model compatible with the reactive model. The followed approach is shown to be usable for forecasting H2S production due to an aquathermolysis phenomenon during a steam injection process.