Characterizing CO2 residual trapping in-situ by means of single-well push-pull experiments at Heletz, Israel, pilot injection site – experimental procedures and results of the experiments

• Published in: International journal of greenhouse gas control 2020-10, Vol.101, p.103129, Article 103129
• Main Authors: Niemi, Auli, Bensabat, Jacob, Joodaki, Saba, Basirat, Farzad, Hedayati, Maryeh, Yang, Zhibing, Perez, Lily, Levchenko, Stanislav, Shklarnik, Alon, Ronen, Rona, Goren, Yoni, Fagerlund, Fritjof, Rasmusson, Kristina, Moghadasi, Ramin, Shoqeir, Jawad A.H, Sauter, Martin, Ghergut, Iulia, Gouze, Philippe, Freifeld, Barry
• Format: Article
• Language: English
• Subjects: CO2 injection experiments; Gas partitioning tracers; Hydraulic tests; Residual trapping
• ISSN: 1750-5836; 1878-0148; 1878-0148
• DOI: 10.1016/j.ijggc.2020.103129

•Two dedicated field experiments carried to quantify the CO2 residual trapping in-situ at 1.6 km depth.•The experimental procedures and results of these experiments are presented.•Hydraulic withdrawal test as a characterization method was robust and gave a clear signal.•Tracer experiments can give more detailed information of CO2 residual distribution but are more complicated to carry out. Two dedicated field experiments have been carried out at the Heletz, Israel pilot CO2 injection site. The objective has been to quantify the CO2 residual trapping in-situ, based on two distinctly different methods. Both experiments are based on the principle of a combination of hydraulic, thermal and/or tracer tests before and after creating the residually trapped zone of CO2 and using the difference in the responses of these tests to estimate the in-situ residual trapping. In Residual Trapping Experiment I (RTE I), carried out in autumn 2016, the main characterization test before and after the creation of the residually trapped zone were hydraulic withdrawal tests. In this experiment, the residually trapped zone was also created by fluid withdrawal, by first injecting CO2, then withdrawing fluids until CO2 was at residual saturation. The second experiment, Residual Trapping Experiment II (RTE II), was carried out autumn 2017. In this experiment, the residually trapped CO2 zone was created by CO2 injection, followed by the injection of CO2-saturated water, to push away the mobile CO2 and leave the residually trapped CO2 behind. In this test, the main reference test carried out before and after creating the residually trapped zone was injection and recovery of gas partitioning tracer Krypton. This paper presents the experimental procedures and results of these experiments. A hydraulic withdrawal test as a characterization method was robust and gave a clear signal. Given the difficulties in injecting water optimally saturated with CO2, in order not to dissolve the residually trapped CO2 or to create situations with excess mobile gas, withdrawal test may also be a generally preferable hydraulic testing method, in comparison to injection. The limitation of any hydraulic test is that it only gives an averaged value over the test section. At Heletz additional information about CO2 distribution was obtained based on thermal measurements and by monitoring the pressure difference between the two sensors in the bolehole. The latter could be used to estimate the amount of mobile CO