Surface geochemical measurements applied to monitoring, verification, and accounting of leakage from sequestration projects

A detailed study of [Formula: see text] and [Formula: see text] surface fluxes, shallow soil gas composition, 10-m hole soil gas composition was made at Rangely, Colorado, Teapot Dome, Wyoming, USA, and the results of geochemical verification measurements at Weyburn, Saskatchewan, Canada. Summer and winter soil gas and gas flux measurements were made at Rangely, and winter only at Teapot Dome. The objectives were to determine if leakage of [Formula: see text] and/or [Formula: see text] could be detected in the overpressured Rangely and the underpressured Teapot Dome systems. At Weyburn, the objective was the determination of the presence or absence of an alleged leak. Seasonal surface [Formula: see text] fluxes at Rangely were similar at on-field locations and an off-field control area. Methane fluxes were much higher at on-field locations than in the control area, suggesting a reservoir source. Seasonal differences in [Formula: see text] fluxes suggested methanotrophic oxidation was occurring in the soils. Shallow soil gas concentration measurements of [Formula: see text] were similar at a 100-cm depth, on-field and in the control area. Methane soil gas concentrations were higher on-field than in the control area; summer and winter. These data were used to select locations with and without evidence for seepage allowing nested sampling up to a 10-m depth. More complex chemical and isotopic measurements were made in 10-m holes at Rangely and Teapot Dome. Methanotrophy was operational at the active Rangely and the passive Teapot Dome systems. A small methane leakage rate of 400–700 tonnes [Formula: see text] and [Formula: see text] of [Formula: see text] tonnes [Formula: see text] were determined at Rangely, and rates near zero at Teapot Dome. Inert gases, carbon-containing gases, as well as isotopic ratios supported the presence of pathways at geochemically anomalous locations at Teapot Dome. Measurements of soil gas and inert gas isotopes in shallow groundwater by other authors at Weyburn, Saskatchewan, found no evidence of leakage.

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Baseline studies of surface gas exchange and soil-gas composition in preparation for CO2 sequestration research: Teapot Dome, Wyoming

AAPG Bulletin ◽

10.1306/03310504109 ◽

2005 ◽

Vol 89 (8) ◽

pp. 981-1003 ◽

Cited By ~ 27

Author(s):

Ronald W. Klusman

Keyword(s):

Gas Exchange ◽

Co2 Sequestration ◽

Soil Gas ◽

Gas Composition ◽

Teapot Dome

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Trace gas flux measurements at the landscape scale using boundary-layer budgets

Philosophical Transactions of the Royal Society of London Series A Physical and Engineering Sciences ◽

10.1098/rsta.1995.0039 ◽

1995 ◽

Vol 351 (1696) ◽

pp. 357-369 ◽

Cited By ~ 25

Keyword(s):

Boundary Layer ◽

Local Area ◽

Surface Fluxes ◽

Trace Gas ◽

Significant Heterogeneity ◽

Methane Fluxes ◽

Flux Measurements ◽

The Mean ◽

Nocturnal Inversion ◽

One Year

Methane effluxes from wetland areas of Scotland were estimated by using the boundary-layer budget method by collecting air samples with an aircraft upwind and downwind of an area of extensive peatland. Nocturnal local area methane fluxes were also estimated at a peat bog site, Loch More, located at 58° 24' N 03° 36' W, using the concentration build up under the nocturnal inversion and from profiles of methane concentration using a tethered balloon. The mean daytime flux for the Loch More case studies in 1993 was found to be 128 ± 57 μ mol m -2 h -1 for the NE region of Scotland, comparable to but generally larger than those obtained for the same region one year earlier. The fluxes are smaller than those obtained in Caithness by the same technique. In 1993 the nocturnal fluxes were found to be 38 ± 7 μ mol m -2 h -1 , significantly smaller than those found during 1992. The daytime fluxes measured by the aircraft were generally larger than fluxes measured by micrometeorological techniques at the same time. These differences can be explained in terms of the significant heterogeneity in surface fluxes that exist on scales of a few hundred metres or less and the possibility of additional sources other than peatland in this region.

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The influence of idealized surface heterogeneity on virtual turbulent flux measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-5059-2018 ◽

2018 ◽

Vol 18 (7) ◽

pp. 5059-5074 ◽

Cited By ~ 12

Author(s):

Frederik De Roo ◽

Matthias Mauder

Keyword(s):

Energy Budget ◽

Turbulent Flux ◽

Surface Heterogeneity ◽

Surface Fluxes ◽

Convective Conditions ◽

Mean Flow ◽

Flux Divergence ◽

Length Scales ◽

Flux Measurements ◽

The Mean

Abstract. The imbalance of the surface energy budget in eddy-covariance measurements is still an unsolved problem. A possible cause is the presence of land surface heterogeneity, which affects the boundary-layer turbulence. To investigate the impact of surface variables on the partitioning of the energy budget of flux measurements in the surface layer under convective conditions, we set up a systematic parameter study by means of large-eddy simulation. For the study we use a virtual control volume approach, which allows the determination of advection by the mean flow, flux-divergence and storage terms of the energy budget at the virtual measurement site, in addition to the standard turbulent flux. We focus on the heterogeneity of the surface fluxes and keep the topography flat. The surface fluxes vary locally in intensity and these patches have different length scales. Intensity and length scales can vary for the two horizontal dimensions but follow an idealized chessboard pattern. Our main focus lies on surface heterogeneity of the kilometer scale, and one order of magnitude smaller. For these two length scales, we investigate the average response of the fluxes at a number of virtual towers, when varying the heterogeneity length within the length scale and when varying the contrast between the different patches. For each simulation, virtual measurement towers were positioned at functionally different positions (e.g., downdraft region, updraft region, at border between domains, etc.). As the storage term is always small, the non-closure is given by the sum of the advection by the mean flow and the flux-divergence. Remarkably, the missing flux can be described by either the advection by the mean flow or the flux-divergence separately, because the latter two have a high correlation with each other. For kilometer scale heterogeneity, we notice a clear dependence of the updrafts and downdrafts on the surface heterogeneity and likewise we also see a dependence of the energy partitioning on the tower location. For the hectometer scale, we do not notice such a clear dependence. Finally, we seek correlators for the energy balance ratio in the simulations. The correlation with the friction velocity is less pronounced than previously found, but this is likely due to our concentration on effectively strongly to freely convective conditions.

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Underestimation of denitrification rates from field application of the <sup>15</sup>N gas flux method and its correction by gas diffusion modelling

Biogeosciences ◽

10.5194/bg-16-2233-2019 ◽

2019 ◽

Vol 16 (10) ◽

pp. 2233-2246 ◽

Cited By ~ 4

Author(s):

Reinhard Well ◽

Martin Maier ◽

Dominika Lewicka-Szczebak ◽

Jan-Reent Köster ◽

Nicolas Ruoss

Keyword(s):

Field Experiments ◽

Pore Space ◽

Soil Surface ◽

Gas Diffusion ◽

Surface Fluxes ◽

Soil Gas ◽

Total Production ◽

Concentration Gradients ◽

Flux Method ◽

Gas Flux

Abstract. Common methods for measuring soil denitrification in situ include monitoring the accumulation of 15N-labelled N2 and N2O evolved from 15N-labelled soil nitrate pool in closed chambers that are placed on the soil surface. Gas diffusion is considered to be the main transport process in the soil. Because accumulation of gases within the chamber decreases concentration gradients between soil and the chamber over time, the surface efflux of gases decreases as well, and gas production rates are underestimated if calculated from chamber concentrations without consideration of this mechanism. Moreover, concentration gradients to the non-labelled subsoil exist, inevitably causing downward diffusion of 15N-labelled denitrification products. A numerical 3-D model for simulating gas diffusion in soil was used in order to determine the significance of this source of error. Results show that subsoil diffusion of 15N-labelled N2 and N2O – and thus potential underestimation of denitrification derived from chamber fluxes – increases with chamber deployment time as well as with increasing soil gas diffusivity. Simulations based on the range of typical soil gas diffusivities of unsaturated soils showed that the fraction of N2 and N2O evolved from 15N-labelled NO3- that is not emitted at the soil surface during 1 h chamber closing is always significant, with values up to >50 % of total production. This is due to accumulation in the pore space of the 15N-labelled soil and diffusive flux to the unlabelled subsoil. Empirical coefficients to calculate denitrification from surface fluxes were derived by modelling multiple scenarios with varying soil water content. Modelling several theoretical experimental set-ups showed that the fraction of produced gases that are retained in soil can be lowered by lowering the depth of 15N labelling and/or increasing the length of the confining cylinder. Field experiments with arable silt loam soil for measuring denitrification with the 15N gas flux method were conducted to obtain direct evidence for the incomplete surface emission of gaseous denitrification products. We compared surface fluxes of 15N2 and 15N2O from 15N-labelled micro-plots confined by cylinders using the closed-chamber method with cylinders open or closed at the bottom, finding 37 % higher surface fluxes with the bottom closed. Modelling fluxes of this experiment confirmed this effect, however with a higher increase in surface flux of 89 %. From our model and experimental results we conclude that field surface fluxes of 15N-labelled N2 and N2O severely underestimate denitrification rates if calculated from chamber accumulation only. The extent of this underestimation increases with closure time. Underestimation also occurs during laboratory incubations in closed systems due to pore space accumulation of 15N-labelled N2 and N2O. Due to this bias in past denitrification measurements, denitrification in soils might be more relevant than assumed to date. Corrected denitrification rates can be obtained by estimating subsurface flux and storage with our model. The observed deviation between experimental and modelled subsurface flux revealed the need for refined model evaluation, which must include assessment of the spatial variability in diffusivity and production and the spatial dimension of the chamber.

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Continuous temporal soil-gas composition variations for earthquake precursory studies along Hsincheng and Hsinhua faults in Taiwan

Radiation Measurements ◽

10.1016/j.radmeas.2009.10.010 ◽

2009 ◽

Vol 44 (9-10) ◽

pp. 934-939 ◽

Cited By ~ 23

Author(s):

Vivek Walia ◽

S.J. Lin ◽

W.L. Hong ◽

C.C. Fu ◽

T.F. Yang ◽

...

Keyword(s):

Soil Gas ◽

Gas Composition

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Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-5697-2013 ◽

2013 ◽

Vol 13 (11) ◽

pp. 5697-5713 ◽

Cited By ~ 66

Author(s):

A. Fraser ◽

P. I. Palmer ◽

L. Feng ◽

H. Boesch ◽

A. Cogan ◽

...

Keyword(s):

Mole Fraction ◽

Transport Model ◽

Correlation Coefficients ◽

Methane Flux ◽

Surface Fluxes ◽

Total Carbon ◽

Tropical Regions ◽

Spatial Coverage ◽

Methane Fluxes ◽

Atmospheric Sampling

Abstract. We use an ensemble Kalman filter (EnKF), together with the GEOS-Chem chemistry transport model, to estimate regional monthly methane (CH4) fluxes for the period June 2009–December 2010 using proxy dry-air column-averaged mole fractions of methane (XCH4) from GOSAT (Greenhouse gases Observing SATellite) and/or NOAA ESRL (Earth System Research Laboratory) and CSIRO GASLAB (Global Atmospheric Sampling Laboratory) CH4 surface mole fraction measurements. Global posterior estimates using GOSAT and/or surface measurements are between 510–516 Tg yr−1, which is less than, though within the uncertainty of, the prior global flux of 529 ± 25 Tg yr−1. We find larger differences between regional prior and posterior fluxes, with the largest changes in monthly emissions (75 Tg yr−1) occurring in Temperate Eurasia. In non-boreal regions the error reductions for inversions using the GOSAT data are at least three times larger (up to 45%) than if only surface data are assimilated, a reflection of the greater spatial coverage of GOSAT, with the two exceptions of latitudes >60° associated with a data filter and over Europe where the surface network adequately describes fluxes on our model spatial and temporal grid. We use CarbonTracker and GEOS-Chem XCO2 model output to investigate model error on quantifying proxy GOSAT XCH4 (involving model XCO2) and inferring methane flux estimates from surface mole fraction data and show similar resulting fluxes, with differences reflecting initial differences in the proxy value. Using a series of observing system simulation experiments (OSSEs) we characterize the posterior flux error introduced by non-uniform atmospheric sampling by GOSAT. We show that clear-sky measurements can theoretically reproduce fluxes within 10% of true values, with the exception of tropical regions where, due to a large seasonal cycle in the number of measurements because of clouds and aerosols, fluxes are within 15% of true fluxes. We evaluate our posterior methane fluxes by incorporating them into GEOS-Chem and sampling the model at the location and time of surface CH4 measurements from the AGAGE (Advanced Global Atmospheric Gases Experiment) network and column XCH4 measurements from TCCON (Total Carbon Column Observing Network). The posterior fluxes modestly improve the model agreement with AGAGE and TCCON data relative to prior fluxes, with the correlation coefficients (r2) increasing by a mean of 0.04 (range: −0.17 to 0.23) and the biases decreasing by a mean of 0.4 ppb (range: −8.9 to 8.4 ppb).

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Towards better error statistics for atmospheric inversions of methane surface fluxes

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-7115-2013 ◽

2013 ◽

Vol 13 (14) ◽

pp. 7115-7132 ◽

Cited By ~ 25

Author(s):

A. Berchet ◽

I. Pison ◽

F. Chevallier ◽

P. Bousquet ◽

S. Conil ◽

...

Keyword(s):

Expert Knowledge ◽

Transport Model ◽

Vertical Mixing ◽

Real Data ◽

Surface Fluxes ◽

Error Statistics ◽

The North ◽

Error Covariance ◽

Methane Fluxes ◽

General Statistical

Abstract. We adapt general statistical methods to estimate the optimal error covariance matrices in a regional inversion system inferring methane surface emissions from atmospheric concentrations. Using a minimal set of physical hypotheses on the patterns of errors, we compute a guess of the error statistics that is optimal in regard to objective statistical criteria for the specific inversion system. With this very general approach applied to a real-data case, we recover sources of errors in the observations and in the prior state of the system that are consistent with expert knowledge while inferred from objective criteria and with affordable computation costs. By not assuming any specific error patterns, our results depict the variability and the inter-dependency of errors induced by complex factors such as the misrepresentation of the observations in the transport model or the inability of the model to reproduce well the situations of steep gradients of concentrations. Situations with probable significant biases (e.g., during the night when vertical mixing is ill-represented by the transport model) can also be diagnosed by our methods in order to point at necessary improvement in a model. By additionally analysing the sensitivity of the inversion to each observation, guidelines to enhance data selection in regional inversions are also proposed. We applied our method to a recent significant accidental methane release from an offshore platform in the North Sea and found methane fluxes of the same magnitude than what was officially declared.

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Near-Surface Monitoring of Large-Volume CO2 Injection at Cranfield: Early Field Test of SECARB Phase III

SPE Journal ◽

10.2118/163075-pa ◽

2013 ◽

Vol 18 (03) ◽

pp. 486-494 ◽

Cited By ~ 19

Author(s):

Changbing Yang ◽

Katherine Romanak ◽

Susan Hovorka ◽

Robert M. Holt ◽

Jeff Lindner ◽

...

Keyword(s):

Carbon Sequestration ◽

Shallow Groundwater ◽

Soil Gas ◽

Phase Iii ◽

Co2 Injection ◽

Co2 Leakage ◽

Gas Monitoring ◽

Near Surface ◽

Surface Monitoring ◽

Gas Component

Summary An early field project of the Southeast Regional Carbon Sequestration Partnership (SECARB) was conducted in Cranfield oil field, western Mississippi. Carbon dioxide (CO2) was injected into coarse-grained fluvial deposits of the Cretaceous lower Tuscaloosa formation, forming a gentle anticline at depths of 3300 m. CO2 injection started in July 2008, increasing to 23 wells (as of May 2011), with total injection rates greater than 1 million tons/yr. Focused monitoring programs of the deep subsurface and near surface have been implemented in different study areas. Here we present results of the near-surface monitoring program over a 3-year period, including shallow groundwater monitoring and soil-gas monitoring. A general methodology of detecting CO2 leakage into shallow groundwater chemistry is proposed. A set of geochemical indicator parameters was identified on the basis of the characterization of groundwater geochemistry, and these were further tested and validated using numerical modeling approaches, laboratory experiments, and field experiments. For soil-gas monitoring, a site (P-site) containing a plugged and abandoned well, a nearby open pit, and an engineered pad (representing a typical industrial near-surface environment for soil-gas monitoring) was selected for detailed study. The site was heavily instrumented with various sensors for measuring soil-gas concentrations at different depths, soil-water content, matric potential, and weather information. Three monitoring technologies were assessed: soil CO2 concentration measurements, CO2 flux measurements on the land surface, and multiple soil-gas component measurements. Results indicate that soil-gas-component measurements provide reliable information for gas-leakage detection. Methodologies of near-surface monitoring developed in this study can be used to improve CO2-leakage monitoring at other CO2 sequestration projects. This early field project was funded by the US Department of Energy, National Energy Technology Laboratory, as part of the Regional Carbon Sequestration Partnerships (RCSP) program. SECARB is led by the Southern States Energy Board (SSEB).

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DETECTION OF INERT GASES BY COLD ELECTRON EMISSION FROM CARBON NANOTUBE EMITTERS

Modern Physics Letters B ◽

10.1142/s0217984905009304 ◽

2005 ◽

Vol 19 (24) ◽

pp. 1207-1211 ◽

Cited By ~ 4

Author(s):

SEONGJEEN KIM

Keyword(s):

Carbon Nanotubes ◽

Gas Sensors ◽

Electron Emission ◽

Dark Current ◽

Gas Adsorption ◽

Inert Gases ◽

Inert Gas ◽

Gas Composition ◽

Cold Electron ◽

Electron Emitters

In this work, different from the typical gas sensors responding by gas adsorption on their surface, a new gas sensor using carbon nanotubes (CNTs) as electron emitters is introduced for detecting inert gases which hardly possess chemical or electrical adsorption in normal conditions. The proposed sensor works by figuring out the variation of the dark current and the initial breakdown voltage on Paschen's law under applied high voltage. As they depend on the gas composition and the pressure in a sealed chamber, it is possible to detect the identity and the concentration of unknown inert gas species.

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