Assessment of CO2 Hydrate Generation During Sequestration in Depleted Hydrocarbon Reservoirs

Abstract

Abstract Carbon sequestration is the process of capturing and storing of atmospheric carbon dioxide (CO2) in the subsurface. The objective of any carbon sequestration project is to store CO2 safely for hundreds or thousands of years with a goal of reducing global climate change and net carbon emission. Based on preliminary studies depleted oil and gas reservoirs are considered good storage sites because they are well understood have already proven capacity to store hydrocarbons over millions of years. Low abandonment pressure in these reservoirs provide an additional voidage-replacement potential for CO2 and allows for a low surface pump pressure during early period of injection. However, the injection process poses several challenges including the potential for hydrate formation. This work aims to raise awareness of hydrate formation, which is a key operational challenge related to CO2 injection in depleted gas reservoirs. Hydrates, specifically CO2 hydrates, can significantly impact the efficiency and safety of CCS operations. This work provides a new approach to assess and anticipate the CO2 hydrate formation in the near wellbore region. A method for coupling a compositional dynamic simulator with flow assurance code using python is introduced to address the phase behavior of CO2 near wellbore under different operational conditions. The proposed approach helps the reservoir engineer to anticipate hydrate formation in the early stage of project and plan to take necessary mitigation actions to avoid injectivity issue due to CO2 Hydrate formation. This work will also address the challenges associated with the numerical modeling of hydrate formation and dissociation, such as accurate thermodynamic modeling and phase equilibrium predictions. The results from this work were identified several important parameters affecting hydrate formation during CO2 injection, namely injection temperature, reservoir pressure and thermal properties of the rock and fluid. It is important to pay attention to these key parameters to ensure accurate prediction of hydrate formation and dissociation phenomena. A sensitivity analysis was conducted to identify their effects on hydrate formation during the CO2 injection. The resulting tornado plot helped the study team to understand how quickly the hydrate can form after the start of injection. This helped the team to perform the necessary operational risk assessment.