Interfacial Evolution and Migration Characteristics of Acid Gas Injected into a Saline Aquifer

Abstract

Acid gas injection into saline aquifers is one of promising ways to reduce greenhouse gas emissions and to dispose hazardous waste simultaneously. On the basis of Level Set method, an improved mathematical model that described interfacial dynamics of acid gas-brine system in a deep confined saline aquifer was proposed for predicting the propagation of the acid gas plume, which was featured by using Peng-Robinson equation and modified Lucas equation to describe variations of the density and viscosity of acid gas in saline aquifers. The evolutional characteristics of acid gas plume were obtained through numerical simulations using COMSOL Multiphysics 3.5a. The results showed that under intrinsic characteristics of aquifers and operational conditions given, the variation of acid gas density was the major factor that influences the patterns and shapes of the plume. The leading edge position of acid gas plume was intensively dependent on the acid gas composition. Under the scheme of fixed mass flow rate injection, as the molar fraction of H2S increased, the position of leading edge advanced gradually towards the injection well. Moreover, the estimation of the storage efficiency of acid gas in saline aquifers was clarified and discussed. The proposed approach and the simulation results will provide insights into the determination of optimal operational strategies and rapid identification of the consequences of acid gas injection into deep confined saline aquifers.