Assessment of H2S Production Risks in Heterogeneous Reservoirs UsingLaboratory-Calibrated Compositional Thermal Reactive Simulations

摘要

SAGD is commonly used as a thermal EOR method to produce heavy oil.However it suffers from theproduction of acid gases formed by aquathermolysis chemical reactions that occur between the steam,thesulfur-rich oil and the mineral matrix.The objectives of this paper are to take advantage of a comprehensivechemical model coupled to compositional thermal reservoir simulations to predict and understand the H2Sproduction variation at surface according to the type of reservoir.Thermal reservoir simulations coupled to both a SARA based 10-component/5-reaction chemical modelfully calibrated against laboratory data and a compositional PVT are used to simulate SAGD processes onheavy oil fields in Athabasca,Canada.Numerical results are then analyzed to provide a comprehensiveanalysis of the mechanisms leading to in-situ H2S generation and its production at wellheads based oncompositional thermal simulations coupled to a fully laboratory calibrated SARA-based chemical model.Composition of the pre-steam,post-steam and produced oil are compared to understand the effect of theaquathermolysis reactions.The impact of heterogeneities on H2S production both in-situ and at surface canalso be observed and explained,especially the variations in vertical permeability.Then simple reservoirmodels with two facies are used to further understand the impact of heterogeneities on H2S production atsurface.Overall heterogeneous cases show important changes in the temperature distribution,fluid flows,reactions kinetics and steam chamber shape that lead to H2S production variations at surface.This detaileddescription of the involved mechanisms in acid gases production will allow operators to better forecast theirH2S risks according to their reservoir properties.