Detection of CO2 leakage from a simulated sub-seabed storage site using three different types of pCO2 sensors

• This work is focused on results from a recent controlled sub-seabed in situ carbon dioxide (CO2) releaseexperiment carried out during May–October 2012 in Ardmucknish Bay on the Scottish west coast. Threetypes of pCO2sensors (fluorescence, NDIR and ISFET-based technologies) were used in combination withmultiparameter instruments measuring oxygen, temperature, salinity and currents in the water columnat the epicentre of release and further away. It was shown that distribution of seafloor CO2 emissionsfeatures high spatial and temporal heterogeneity. The highest pCO2values (∼1250 atm) were detectedat low tide around a bubble stream and within centimetres distance from the seafloor. Further up in thewater column, 30–100 cm above the seabed, the gradients decreased, but continued to indicate elevatedpCO2at the epicentre of release throughout the injection campaign with the peak values between 400and 740atm. High-frequency parallel measurements from two instruments placed within 1 m fromeach other, relocation of one of the instruments at the release site and 2D horizontal mapping of therelease and control sites confirmed a localized impact from CO2emissions. Observed effects on the watercolumn were temporary and post-injection recovery took <7 days.A multivariate statistical approach was used to recognize the periods when the system was dominatedby natural forcing with strong correlation between variation in pCO2and O2, and when it was influencedby purposefully released CO2.Use of a hydrodynamic circulation model, calibrated with in situ data, was crucial to establishingbackground conditions in this complex and dynamic shallow water system.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

CCS

QICS

CO2 release

Leakage detection

pCO2 sensors

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