Leading the Way in CCS Monitoring: An Innovative CO2 Measurement in Reservoirs

An innovative CO2 measurement in reservoirs utilizes both saturation log and production log tools. The pulsed-neutron water flow log (WFL) survey determined the CO2 injection profile by monitoring the injection rate and wellhead pressure. The WFL survey was recorded during CO2 injection at a rate of 4.8 tons per hour at a wellhead pressure of more than 1000 psi. The survey covered the full perforation interval, with WFL stations taken at multiple depths. The pulsed-neutron tool was logged in GSH (Gas, Sigma and Hydrogen-Index) mode across the injected formation and the shallower seal, covering both ‘Top Seal’ and ‘Storage Formation’ zones. The pulsed-neutron porosity measurement was processed using a new algorithm that compensates for borehole-filled CO2 gas (as opposed to the conventional algorithm designed for water/oil/gas-filled borehole). The density measurements in Fig.1 revealed that the water level during injection was pushed down to B ft, while the shut-in water level was at A ft. The minimal injection rate computed below B ft is due to low velocity and high-water holdup. The phenomena and interpretation results showed that the CO2 injection profile was determined using gas velocity measurements from WFL stations and fluid density measurements. The presence of gas was indicated by using new algorithm technique and high values of the gas ratio indicator (GRAT) and the difference between pulsed-neutron porosity (TPHI) and effective porosity (PHIE). The lower part of the perforated interval exhibited minimal injection (<5%). The study concludes that 5% of fraction of the perforation interval of the injected CO2 went into reservoir, with minimal injection across the lower part. The interpretation results provide valuable insights into the CO2 injection profile and the effectiveness of the injection process in the first CCS well in Onshore Abu Dhabi. The evaluation marks a groundbreaking initiative in the monitoring of CO2 storage within an onshore field in Abu Dhabi. The innovative technique is set to revolutionize both CO2 injection and monitoring processes and pave the way for better and more efficient CCS wells design/execution.