Method and device for analysing the CO2 content of a borehole fluid

摘要

The carbon dioxide (CO 2) in the cell is transferred from it by scavenging with an inert gas, and the amount of CO 2 present in the fluid after acidification is measured, using an infrared or thermal conductivity cell. The quantity of CO 2 in the geological formation is calculated. The procedure consists of drilling a borehole (10) through the geological formation (20) from the surface, using a drilling fluid with a pH above 8. A quantity of the circulated fluid is drawn back up and transferred to a cell (5) where its pH level is measured and adjusted by acidification to give a value of below 4. The carbon dioxide (CO 2) in the cell is transferred from it by scavenging its inner volume with an inert gas, and the amount of CO 2 present in the fluid after acidification is measured, using an infrared or thermal conductivity cell. The quantity of CO 2 in the geological formation is calculated from the result after taking into account the quantity of carbonate yielded by the formation and/or by additives in the drilling fluid.