Perpustakaan Digital ITB

Depleted oil and gas reservoirs have become the main focus as the target formation under consideration of CO2 sequestration, including Carbon Capture Storage (CCS) purposes. CO2 often be injected in a supercritical state to decrease its volume and allows more CO2 to be stored in the reservoir. However, when injecting superciritcal CO2 into a depleted reservoir significant temperature drop or often called Joule-Thomson effect may occur. When Joule-Thomson effect occurs, rersulting in a temperature drop below 32°F, it can lead to embrittlement of downhole equipment and freezing of pore fluids. This can result in loss of well integrity and well injectivity. To mitigate this problem, this study will analyze temperature profile along the well depth and apply simple analytical solution to assess temperature drop around the wellbore radius of the well. The analytical solution will be presented by assuming constant thermophysical porperties and steady-state flow. By using a conceptual study case, this solution will be developed to identify the most effective option for maximizing the injectivity into the reservoir, while minimizing temperature drop and pore fluid freezing. The analytical solution can be implemented in simple spreadsheet software and allows fast evaluation in a constant CO2 injejction rate. According to this study, Joule-Thomson effect is unlikely to occur along the well depth but occurs around the wellbore radius. This study found that the minimum degree of temperature drop of -0.0023°F/ft is seen when the injection scenario is performed with 1100 psig injection pressure and 7.33 kg/s of CO2 injection rate. Injecting CO2 into a reservoir with permeability of 5 mD leads to pore fluid freezing. Nevertheless, this issue can be avoided by reducing the injection rate to 5.8 kg/s or below.