Evaluating the Performance of Soil Flux Surveys and Inversion Methods for Quantification of CO2 Leakage

Schroder, Ivan; Wilson, Peter; Feitz, Andrew; Ennis‐King, Jonathan

doi:10.1016/j.egypro.2017.03.1499

Cited by 16 publications

(9 citation statements)

References 31 publications

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“…These hotspots established in the more clay-rich regions, and soil gas saturation in the hotspots were lower, reaching a maximum of 60%. In addition, soil surveys aided by krypton tracer found that CO2 spread much further from the horizontal well in the wet season (Schroder et al, 2017). It is hypothesised that the greater extent of the vadose zone in the dry season allows greater quantities of CO2 to accumulate in the subsurface, and so limits the intensity of CO2 release to surface (Feitz et al, 2014a, Schroder et al, 2017.…”

Section: Temporal Effects On Co 2 Fatementioning

confidence: 99%

What have we learnt about CO2 leakage from CO2 release field experiments, and what are the gaps for the future?

Roberts

Stalker

2020

Earth-Science Reviews

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Legislation and guidelines developed for Carbon Capture and Storage (CCS) have set performance requirements to minimize leakage risk, and to quantify and remediate any leaks that arise. For compliance it is necessary to have a comprehensive understanding of the possible spread, fate and impacts of any leaked CO 2 , and the ability to detect and quantify any CO 2 seepage into marine or terrestrial environments. Over the past decade, a number of field scale CO2 release experiments have been conducted around the world to address many of the uncertainties regarding the characteristics of near-surface expression of CO 2 in terms of the impact and quantitation of CO2 leaks. In these experiments, either free phase or dissolved CO2 was injected and released into the shallow subsurface so as to artificially simulate a CO2 leak into the near-surface environment. The experiments differ in a number of ways, from the geological conditions, surface environments, injection rates and experimental set-up -including the injection and monitoring strategy. These experiments have provided abundant information to aid in the development of our scientific understanding of environmental impacts of CO2 while assessing state of the art monitoring techniques.We collated a global dataset of field-scale shallow (depths < ~25 m) controlled CO2 release experiments. The dataset includes 14 different field experiment locations, of which nine intended to release CO2 to the surface, and the remaining sites intended for CO2 to remain in the shallow subsurface. Several release experiments have been conducted at half of these sites, and so in total, 42 different CO2 release tests have taken place at the 14 sites in our dataset. We scrutinized our dataset to establish: (i) the range of experimental approaches and settings explored to date (such as the environment, subsurface conditions, injection strategy and whether gaseous or dissolved CO2 were injected and in what quantities); (ii) the range of CO2 injection and surface release rates at these experiments; (iii) the collective learnings about the surface and subsurface manifestation of the CO2 release, the spread and fate of the CO2, rates of CO2 flux to surface, and methods of measuring these; (iv) the strengths and limitations of current approaches for detecting and quantifying CO2. This allowed us to highlight where uncertainties remain and identify knowledge gaps that future experiments should seek to address. Further, drawing on the collective experiences, we have identified common issues or complications which future CO2 release experiments can learn from.

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Section: Temporal Effects On Co 2 Fatementioning

confidence: 99%

What have we learnt about CO2 leakage from CO2 release field experiments, and what are the gaps for the future?

Roberts

Stalker

2020

Earth-Science Reviews

View full text Add to dashboard Cite

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“…These include unintended leakage at two CO2 injection operations: micro-seepage at CO2-EOR operations in Rangely (USA) [22]; and wellhead leakage at KB5 well at the In Salah CO2 injection project due to a missing flange [46]. Other analogues include geyser style seepage from two abandoned boreholes (Crystal Geyser and 10-mile Geyser, Utah) [29], diffuse gas emission from an abandoned coal mine at Banditella, Italy [47] and an abandoned water well in Qinghai [73]. None of the industrial analogues studied here report CO2 flux, only total leak rate, but in most cases the seep area is typically small -limited to the wellbore or its vicinity -and therefore flux would be anomalously high.…”

Section: 1 Global Database Of Co2 Seepagementioning

confidence: 99%

What Have We Learnt About CO2 Leakage in the Context of Commercial-Scale CCS?

et al. 2018

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The viability of Carbon Capture and Storage (CCS) depends on the reliable containment of injected CO2 in the subsurface. Robust and cost-effective approaches to measure monitor and verify CO2 containment are required to demonstrate that CO2 has not breached the reservoir, and to comply with CCS regulations. This includes capability to detect and quantify any potential leakage to surface. It is useful to consider the range of possible leak rates for potential CO2 leak pathways from an intended storage reservoir to surface to inform the design of effective monitoring approaches. However, in the absence of a portfolio of leakage from engineered CO2 stores we must instead learn from industrial and natural analogues, numerical models, and laboratory and field experiments that have intentionally released CO2 into the shallow subsurface to simulate a CO2 leak to surface. We collated a global dataset of measured or estimated CO2 flux (CO2 emission per unit area) and CO2 leak rate from industrial and natural analogues and field experiments. We then examined the dataset to compare emission and flux rates and seep style, and consider the measured emission rates in the context of commercial scale CCS operations. We find that natural and industrial analogues show very wide variation in the scale of CO2 emissions, and tend to be larger than leaks simulated by CO2 release experiments. For all analogue types (natural, industrial, or experiment) the emission rates show greater variation between sites than CO2 flux rates. Quantitation approaches are non-standardized, and that measuring and reporting both the CO2 flux and seep rate is rare as it remains challenging, particularly in marine environments. Finally, we observe that CO2 fluxes tend to be associated with particular emission characteristics (vent, diffuse, or water-associated). We propose that characteristics could inform the design and performance requirements for CO2 leak monitoring approaches tailored to detect specific emission styles.

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“…60%). In addition, soil surveys aided by krypton tracer found that CO2 spread much further from the horizontal well in the wet season [21], and it was hypothesized that the greater extent of the vadose zone in the dry season allows greater quantities of CO2 to accumulate in the subsurface, and so limits the intensity of CO2 release to surface [21,22]. These effects may be observed at Tipperary and Taradale, where the measured CO2 emission was substantially greater in the wet season.…”

Section: What Controls the Observed Variations In Co2 Emission?mentioning

confidence: 99%

Quantifying CO2 Leak Rates in Aquatic Environments

et al. 2018

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The Daylesford region of Victoria (Australia), is a region of natural CO2 seepage. Small bubble streams of CO2 are released into ephemeral river beds proximal to mineral springs that contain high dissolved CO2 content. We study four sites of CO2 degassing to (i) establish the characteristics of CO2 seepage caused by transport to surface of CO2-rich water, (ii) provide an estimate of CO2 flux in the region, and (iii) investigate seasonal effects on CO2 seepage. We observe that bubbling behavior varies considerably between sites, including the number and distribution of bubbling points, and bubble stream the continuity. Total CO2 seep rates at each site were low (< 20 kg/d) but varied substantially between different sites. There were no obvious indicators of total emission rate; the bubble density or other characteristics at the highest emission seep were not remarkably different to the smaller seeps. We find that the total CO2 emission varies inconsistently with season, with some seep rates increasing and other decreasing in the dry season when water levels are lower. We find there are challenges in quantifying the total gas leakage at sites of highly localized and intermittent degassing. Our work has implications for detecting and quantifying leaks from engineered CO2 storage sites which emerge in aqueous environments, which could be these are marine or terrestrial (lakes or rivers).

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Evaluating the Performance of Soil Flux Surveys and Inversion Methods for Quantification of CO2 Leakage

Cited by 16 publications

References 31 publications

What have we learnt about CO2 leakage from CO2 release field experiments, and what are the gaps for the future?

What have we learnt about CO2 leakage from CO2 release field experiments, and what are the gaps for the future?

What Have We Learnt About CO2 Leakage in the Context of Commercial-Scale CCS?

Quantifying CO2 Leak Rates in Aquatic Environments

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