Impact of CO2 solubility on design of single well tracer tests to evaluate residual saturation during carbon capture and storage

Masra Awag*, Eric Mackay, Saeed Ghanbari

*Corresponding author for this work

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Single-well tracer technique have been well applied in many petroleum industry and environmental applications. However, these tests have not been well developed for CO2 geological storage purposes to evaluate residual CO2 saturation during the appraisal phase of site investigation, due to the challenges occurring from the complex phase behaviour. In this study, two single-well tracer tests are numerically modelled to quantify the residual gas saturation. Our study addresses the design of an alternative single well tracer test sequence, which involved a single pass of the tracer saturated water over the residually trapped zone, thereby reducing the amount of CO2 dissolution into the tracer solution. A one-dimensional numerical modelling of the tracer propagation and partitioning with homogenous properties was used for the calculations of the difference in tracer breakthrough times during water withdrawal from the tests. Model sensitivity variations were applied to analyse the impact of reservoir and treatment design parameters on the residual gas saturation. The residual gas saturations calculated reflect the input values, including the effect of hysteresis, to within 10% accuracy. It was found that changing the CO2 saturated water volume injected after CO2 made the CO2 front to travel to different distances from the well, and thus the tracer had different size of residually trapped zones to travel through when it is back produced and encounters different residual gas saturations, and therefore affected the residual gas saturation calculations. The modelling also shows that optimal injection of CO2-saturated water to prevent the dissolution of the residually trapped CO2 and establish the residually trapped zone was challenging to achieve, and therefore using the fluid withdrawal method was more robust to establish the residually trapped zone. This is because of the dependency of solubility on pressure. The numerical models may be used to design, optimise, and interpret the field tests.

Original languageEnglish
Pages (from-to)6-19
Number of pages14
JournalAdvances in Geo-Energy Research
Issue number1
Early online date19 Nov 2023
Publication statusPublished - Jan 2024


  • CO store characterization
  • partitioning tracer
  • residual CO saturation
  • single well tracer test
  • tracer test design

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Geotechnical Engineering and Engineering Geology
  • Mechanics of Materials


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