Perpustakaan Digital ITB

Global energy-related CO2 emissions have increased, raising significant environmental concerns due to CO2's greenhouse effect. Carbon Capture and Storage (CCS) aims to mitigate these emissions by capturing and storing CO2. This study focuses on CO2 injection into sandstone reservoirs at the "B" structure in the "S" field, specifically examining the impact of capillary-driven backflow on salt precipitation. The objectives are to analyze the effect of capillary backflow on salt distribution and determine its impact on injectivity and trapping mechanisms. Since salt precipitation involves the concentration of ions beyond their limit, salinity becomes a key factor. Capillary-driven backflow, which supplies salt out of the injection point, plays an important role in salt precipitation even in less saline targets. This study applies numerical simulations through CMG GEMTM to model water vaporization and salt precipitation phenomena. The field will be on injection for 10 years, with the trapping mechanism observed over a 50-year range. Simulations revealed distinct time scales for flooding and drying fronts, with capillary backflow significantly influencing salt distribution, injectivity, and trapping mechanisms. Distinct time between two fronts is the consequence of the different phenomena involved. Flooding front involves the piston-like displacement, while drying front involves gradual evaporation at residual brine. Higher injection rates initially improved injectivity due to high pressure counteracting capillary forces but ultimately reduced it due to increased salt precipitation. Capillary backflow caused water saturation re-equilibration and local salt precipitation, while uniform but less substantial precipitation occurred without it. Injectivity impairment ranged from 21% to 74% with capillary backflow, and cumulative CO2 injection in the capillary-driven backflow model was 9% lower than without it. However, the model with capillary backflow results in a 5% higher residual trapping share. Capillary backflow enhances CO2 trapping in an immobile form and increases early mineral trapping efficiency, though the effect is minimal. Additionally, it allows CO2 in mineral forms to redissolve into brine after injection stops, impacting mineral trapping and redissolution trends. Higher initial halite volume fractions result in more end salt near the wellbore, with minimal impact on overall salt distribution. Higher initial calcite does not always lead to more precipitation due to complex interactions with dissolved CO? affecting brine acidity and solubility. Changes in salt precipitation align with porosity and permeability alterations, resulting in consistent permeability reduction. This study underscores the importance of considering capillary backflow in CO2 injection operations to avoid overestimating injectivity and cumulative injection, while also understanding its impact on trapping effects behavior.