Midstream on a chip: ensuring safe carbon dioxide transportation for carbon capture and storage

Emerging technologies like enhanced oil recovery and carbon sequestration rely on carbon dioxide water content data to ensure that pipelines remain sub-saturated to avoid corrosion and hydrate flow assurance issues. To improve throughput and confidence in the hydrate phase equilibria data to avoid pipeline blockages, further research into the carbon dioxide water content must be conducted. However, the liquid carbon dioxide regime is experimentally difficult to study and the available data disagree between studies. This work aims to provide the critical and accurate data for liquid carbon dioxide for a high pressure range (13.8 to 103.4 bar) and temperature range (20 and -30 °C) utilizing a small volume microfluidic reactor (<20 microliter) coupled with Raman spectroscopy, which can reveal any phase metastability in the system. The small volume of the microfluidic system (<20 microliter) allowed experiments to be run in a few hours, compared to a whole week for prior larger scale measurements. The carbon dioxide water content results from this work agree well with both model predictions and available literature data in the gas region; however, once carbon dioxide was converted to liquid, the data showed a weak function of pressure, similar to model predictions and some previous data sets. The discrepancies between literature data are attributed to metastable phases present in the equilibrium cells, as the data is usually taken in the carbon dioxide near critical region, close to carbon dioxide's dew point, and near the hydrate phase transition. For these reasons, it is important to observe and qualify all phases in the cell, as was done in this novel study with in situ Raman spectroscopy coupled to Midstream on a chip, to ensure accurate water content of the carbon dioxide fluid phase is being measured.