The Ground CO2 Mapper. An innovative tool for the rapid and precise mapping of CO2 leakage distribution

The recently developed Ground CO2 Mapper (“Mapper” for short) is an inexpensive, light, robust, and low power consuming tool for determining the distribution of CO2 at the soil-atmosphere contact as an indicator of CO2 leakage. The basic premise behind the Mapper is that the contact between the ground surface and the atmosphere represents an interval where CO2 leaking from the subsurface can accumulate in anomalous concentrations due to two mechanisms, the higher density of CO2 with respect to air and the tendency of wind speed (and thus mixing) to approach zero near the ground surface due to frictional drag. Because of its measurement target and the tool’s very rapid response time, Mapper surveys can be conducted very quickly at a high sampling density, yielding accurate maps of CO2 spot anomalies. The unit can be used by anyone and deployed within only 5-10 minutes after sensor and GPS signal warm-up. Here we describe the Mapper and present results from a site of natural diffuse CO2 degassing in central Italy

Spatial-temporal water column monitoring using multiple, low-cost GasPro-pCO2 sensors: implications for monitoring, modelling, and potential impact

Monitoring of the water column in the vicinity of offshore Carbon Capture and Storage (CCS) sites is needed to ensure site integrity and to protect the surrounding marine ecosystem. In this regard, the use of continuous, autonomous systems is considered greatly advantageous due to the costs and limitations of periodic, ship-based sampling campaigns. While various geochemical monitoring tools have been developed their elevated costs and complexities mean that typically only one unit can be deployed at a time, yielding single point temporal data but no spatial data. To address this the authors have developed low-cost pCO2 sensors (GasPro-pCO2) that are small, robust, stable, and which have a low power consumption, characteristics which allow for the deployment of numerous units to monitor the spatial-temporal distribution of pCO2, temperature, and water pressure in surface water environments. The present article details the results of three field deployments at the natural, CO2-leaking site near Panarea, Island. While the first consisted of 6 probes placed on the sea floor for a 2.5 month period, the other two involved the deployment of 20 GasPro units along a transect through the water column in the vicinity of active CO2 seeps over 2 – 4 days. Results show both transport and mixing processes and highlight the dynamic nature of the leakage-induced marine geochemical anomalies. Implications for monitoring programs as well as potential impacts are discussed

Gases and seabed fluid fluxes at the Panarea shallow hydrothermal vents (Aeolian Islands)

CO2 leaking into the shallow sediments and overlying seawater is partitioned in different forms, each migrating at its own rate and having potentially different impacts. To begin with the CO2 gas will migrate through the shallow subsurface either alone as a free gas or together with associated deep fluids (e.g. brines), with the free-phase CO2 equilibrating with the surrounding pore waters/associated brines. Migrating upward these fluids will enter the base of the water column, with the release of gas bubbles (and possibly associated waters) from the sediments into the overlying seawater. The bubbles will rise in the water column creating what is known as a bubble “flare” with the CO2 in the bubbles dissolving in the surrounding surface water as they rise. Depending on the depth and the chemical/physical characteristics of the water column, these bubbles may or may not reach the water surface. Any co-migrating water/brine will also be released into the water column, creating a plume having a chemical composition that is distinct from the surrounding seawater, consisting of dissolved gases (mainly CO2), elements in the original brine, and elements liberated via CO2-induced water-rock interaction. The height that this dissolved plume will reach in the water column will depend on the original flow rate across the sediment-water interface and the density contrast between the plume and surrounding seawater. Both the gas-induced and water plumes will then migrate laterally and vertically as a result of the local currents, water column stratification, and density effects, meaning that there is the potential for impact both in the near and far field for pelagic organisms, both in terms of a lower pH and the possibility of elevated concentrations of toxic elements. This study was carried out in the framework of two EC funded projects, RISCS and ECO2 related to research on sub-seabed CO2 storage as climate change mitigation strategy, and potential impact on marine ecosystems. Here, we investigated how CO2-leakage, a risk associated with subseafloor CO2-storage, can affect physical and chemical characteristics of the surrounding ecosystem. We studied the Panarea natural laboratory site (Aeolian Islands), where natural CO2 is leaking from the seafloor into the overlying water column, as an analogue for a leakage scenario

Preliminary Experiments and Modelling of the Fate of CO2 Bubbles in the Water Column Near Panarea Island (Italy)

Although CO2 capture and storage in deep, offshore reservoirs is a proven technology, as illustrated by over 15 years of operation of the Sleipner site in the Norwegian North Sea, potential leakage from such sites into the overlying water column remains a concern for some stakeholders. Therefore, we are obliged to carefully assess our ability to predict and monitor the migration, fate, and potential ecosystem impact of any leaked CO2. The release of bubbles from the sea floor, their upward movement, and their dissolution into the surrounding water controls the initial boundary conditions, and thus an understanding of the behavior of CO2 bubbles is critical to address such issues related to monitoring and risk assessment. The present study describes results from an in situ experiment conducted in 12 m deep marine water near the extinct volcanic island of Panarea (Italy). Bubbles of a controlled size were created using natural CO2 released from the sea floor, and their evolution during ascent in the water column was monitored via both video and chemical measurements. The obtained results were modelled and a good fit was obtained, showing the potential of the model as a predictive tool. These preliminary results and an assessment of the difficulties encountered are examined and will be used to improve experimental design for the subsequent phase of this research

Water column monitoring at CO2 leaking sites near Panarea Island

The fate and transport of geologically produced CO2 that leaks from the sea floor into the overlying water column has numerous important implications related to large scale carbon cycling and potential impact on marine organisms, and is of interest for the development of improved monitoring techniques and strategies for offshore Carbon Capture and Storage (CCS) sites. The CO2 leakage areas off the east coast of Panarea Island, Italy provides an excellent environment to study these processes given the wide range of different flux rates in relatively shallow water. The water column at this site was monitored using two completely different but complementary approaches, continuous monitoring along short 2D transects using GasPro pCO2 sensors and discrete seasonal sampling along a 700 m transect crossing multiple leakage areas. Results are discussed in terms of the movement of CO2, and associated tracers, in the water column

Surface gas measurements and related studies for the characterization and monitoring of geological CO2 storage sites; experiences at Weyburn and in Salah.

Preliminary baseline soil gas data collected in the summer and autumn of 2001 above the Phase 1A injection area of the EnCana Enhanced Oil Recovery project at the Weyburn oilfield in south Saskatchewan was presented at GHGT-6 in Kyoto. Data can now be presented for all three years of the study with conclusions, the predominant one being that the major controls on soil gas levels are seasonal and meteorological with no indications of leakage from depth. In the autumns of 2002 and 2003 further in situ monitoring of CO2, CO2 flux, O2, CH4, radon (222Rn) and thoron (220Rn) was carried out. Soil gas samples were also collected for laboratory analysis of helium, permanent gases, sulphur species and light hydrocarbons. All sampling was repeated over the same 360 point sampling grid and more detailed profiles for both follow-up years. Marked changes in CO2 levels (especially flux) for each of the three-year datasets indicate changes in surface conditions, rather than CO2 from a deeper source. The radon and thoron data was found to be similar for the three years but appears to vary in response to drift composition, and seasonal effects, rather than migration from a deep source. In 2003 further work was agreed in addition to the main grid and profile data. A control area was sampled for the same suite of gases, 10km to the northwest of the oil field. It included similar topography, land use and drift composition to the main sampling grid. There were 35 sample locations on a 7 x 5 point grid with 100m spacing and two additional sites. Early conclusions indicate that the soil gas results in the control area are very similar to those from the main grid, vindicating control site selection and further supporting a lack of deeply sourced CO2 over the injection area. Along with the control site, five zones of possible CO2 leakage were also surveyed and sampled. Two cross a river lineament that may be associated with deep faulting, two were abandoned oil well sites and one site overlays a deep salt dissolution feature. (Unfortunately CO2 flux and gamma measurements were not carried out at these sites.) A northeast/southwest trending lineament, just north of the main grid, was sampled along two profiles perpendicular to the feature, with an increased density of sampling over the feature. The feature generally followed an incised river valley and anomalous CO2 was only detected on the valley floor, where it would be expected as there was lush vegetation in this zone. There were no coincident anomalies for other gases. Soils around two abandoned wells were also sampled. A 16-site grid was surveyed around each well. One well had been completely abandoned and the other was suspended due to failed casing. Such boreholes represent possible points of weakness that may be routes for CO2 migration. The well with failed casing had weakly anomalous CO2 locally to the south, again unmatched for other gases. The fully abandoned well had background CO2 values. Two perpendicular profiles of 10 sites at 25m spacing were sampled for soil gas over the mapped centre of the dissolution feature. Background values were obtained. In 2003 two vertical profiles were performed both indicating an increase in CO2 to a depth maximum of 1.80m; this increase is matched by a corresponding decrease only in O2, indicating biological respiration. Radon concentration indicated no anomalies. Portable gamma spectrometric data was collected in 2003 over the west-centre area of the grid, the profiles and over the control grid. The composition of soils from both areas was found to be very similar.PublishedBerkeley, California4.5. Degassamento naturaleope