Wellbore Cement Porosity Evolution in Response to Mineral Alteration

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Wellbore Cement Porosity Evolution in Response to Mineral Alteration During CO Flooding 2

Michael C. Cheshire, Andrew G. Stack, J. William (Bill) Carey, Lawrence M. Anovitz, Timothy R Prisk, and Jan Ilavsky Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b03290 • Publication Date (Web): 13 Dec 2016 Downloaded from http://pubs.acs.org on December 16, 2016

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Environmental Science & Technology

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Wellbore Cement Porosity Evolution in Response to

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Mineral Alteration During CO2 Flooding

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Michael C. Cheshire1*, Andrew G. Stack1, J. William Carey2, Lawrence M. Anovitz1, Timothy R.

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Prisk1, Jan Ilavsky3 1

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Oak Ridge National Laboratory, Oak Ridge, TN 37831

Los Alamos National Laboratory, Los Alamos, NM 87545 3

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Argonne National Laboratory, Argonne, IL 60439

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Abstract

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Mineral reactions during CO2 sequestration will change the pore-size distribution and pore-

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surface characteristics, complicating permeability and storage security predictions. In this paper,

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we report a small/wide angle scattering study of wellbore cement that has been exposed to

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carbon dioxide for three decades. We have constructed detailed contour maps that describe local

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porosity distributions and mineralogy of the sample, and relate these quantities to the carbon

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dioxide reaction front on the cement. We find that the initial bimodal distribution of pores in the

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cement, 1-2 nm and 10-20 nm, are affected differently during the course of carbonation

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reactions. Initial dissolution of cement phases occurs in the 10-20 nm pores, and leads to the

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development of new pore-spaces that are eventually sealed by CaCO3 precipitation, leading to a

ACS Paragon Plus Environment

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loss of gel and capillary nanopores, smoother pore surfaces, and reduced porosity. This suggests

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that during extensive carbonation of wellbore cement, the cement becomes less permeable due to

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carbonate mineral precipitation within the pore space. Additionally, the loss of gel and capillary

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nanoporosities will reduce the cement reactivity to CO2 due to reactive surface area loss. This

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work demonstrates the importance of understanding not just changes in total porosity, but how

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the distribution of porosity evolves with reaction that affects permeability.

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Introduction

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Porous media are the principal host for any subsurface fluid and are, therefore, the main sites

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for geochemical reactions associated with CO2-sequestration. How geochemical reactions and

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their kinetics affect these media has been the subject of considerable research, particularly with

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respect to potential mineral trapping of CO2.1 Recent work has considered potential pore-size

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dependencies of geochemical reactions.2,3 If pore-size dependent geochemical reactions occur,

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they could have significant impact on long-term security through changes to permeability and

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sealing capacity in the subsurface CO2 storage complex.4,5,6,7 While it may be expected local

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changes in porosity due to dissolution and carbonate or other mineral precipitation may

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increase/reduce permeability4,5, pore-size dependent reactions may affect permeability in

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unforeseen ways since functions describing permeability have a non-linear dependence on pore

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size.6,7 A complicating factor is that large permeability variations (up to five orders of

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magnitude) are observed in rocks with similar porosities.8 This natural variability in the starting

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material makes reactive transport models difficult to implement, because permeability cannot be

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determined on the basis of porosity alone.7 Complicating permeability calculations of porous

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media are the tortuosity and constrictive parameters.9,10,11 Tortuosity is defined as ratio of the


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flow length without porous media versus path length in porous media.9,10,11 Constrictivity, also

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known as bottleneck effect, describes the variable openness of the flow path in a natural porous

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media.9,10,11 Therefore, changes in the interfacial regions within the pore-spaces have direct

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impact on the tortuosity, constrictivity, and subsequently, permeability. Furthermore, given the

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large uncertainty in the initial permeability, coupled to pore structure alterations (i.e., changes to

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porosity, pore-size distribution, tortuosity, and constrictivity), predicting permeability evolution

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in response to anthropogenic perturbation becomes problematic.

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In this study, we investigate detailed changes in porosity as a function of pore-size that occurs

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in a field sample of wellbore cement exposed to CO2 during CO2-enhanced oil recovery.

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Wellbore cement integrity is a major concern for CO2 sequestration operations as the cement is a

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key element of the hydrodynamic sealing system, and thus CO2-reacted cement represents a

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potential leakage pathway.12,13 In addition to their intrinsic importance in establishing zonal

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isolation in wells, ordinary portlandite cements are an excellent analogue for natural nano-porous

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geological materials containing phases that with a high degree of reactivity permit more efficient

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experimental observations. Examples of potential CO2 storage materials with reactive phases

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include some caprocks14,15, volcanic sediments such as the Nagaoka injection site16, and basalts

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present at Big Sky17 and Carbfix.18,19

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The wellbore cement investigated here was recovered from a CO2 injection well located in the

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SACROC unit in West Texas.20 The well was a producer for 25 years prior to conversion to a

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CO2/water injection well for 30 years for the purposes of enhanced oil recovery (Figure 1a).

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Analysis of the wellbore cement showed that it was partially carbonated due to CO2 leakage

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along the cement/rock interface (Figure 1b).20 The unaltered portion of the wellbore cement is

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composed of 86 wt. % amorphous materials. The remaining material consists of typical cement


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phases, e.g., portlandite, katoite, brownmillerite, and calcite. The carbonated cement had

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experienced dissolution and precipitation reactions in which cement phases dissolved (i.e.,

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portlandite and calcium silica hydrate) and calcite and aragonite with lesser amounts of vaterite

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(total CaCO3 phases 55%) precipitated along with various amorphous phases (i.e., silica). Thus,

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the SACROC wellbore cement shows a reaction series that may be expected to occur at CO2

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sequestration sites.21 This process of carbonated fluids interacting with reactive phases with

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potential porosity and permeability alteration impacts sequestration site performance.10 We,

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therefore, focused this investigation on measuring cement porosity evolution in response to

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chemical and mineral alteration during CO2 injection to provide a better understanding of pore-

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scale processes and how those processes might influence permeability and mechanical

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properties.

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Experimental Methods

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The SACROC sample was prepared and analyzed as an ~50 µm thick thin-section mounted on

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a borosilicate slide with epoxy (Figure 1b). It was analyzed via ultra-small (USAXS), small X-

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ray scattering (SAXS) (to reveal pore distributions) and wide-angle (WAXS) X-ray scattering (to

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reveal Bragg peaks of mineral phases) at the Advance Photon Source, Argonne National

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Laboratory on beamline 9ID.22 Beam size for (U)SAXS measurements was 0.2 mm × 0.2 mm

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and WAXS measurements were 0.2 mm × 1.5 mm. For (U)SAXS measurements, the sample was

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rastered across the X-ray beam developing a 4 × 31 point grid covering most of the sample.

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WAXS measurements were collected across the shale - orange cement (i.e., alteration zone) and

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orange – grey cement interfaces (Figure 1b). Data reduction and analyses were conducted using

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the Irena and Nika macro packages yielding Q-Intensity plots [Q = 4π/λ*sin θ, where θ is the


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scattering angle and λ is the X-ray wavelength (0.6888(8) Å)].23,24 Porosity data was determined

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using the methods described by Wang et al.25 and Anovitz et al.26, while scattering characteristics

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were modeled using the Unified Fit model with a phase contrast determined between open

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porosity (unepoxied pores) and cement solids.27,28 For detailed methods description regarding

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scattering application to the characterization and analysis of porosity and pore structures were

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refer the reader to review Anoviz and Cole29. Orange and grey zone cement compositions are

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provided by Carey et al.20. Contouring and interpolation were done using Igor Pro 6.37 (Lake

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Oswego, 2015). Manual indexing, phase identification, and peak area calculations were

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performed on WAXS curves to determine the spatial distribution of mineralogy in the sample.

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Errors presented with total porosity and pore sizes are one-sigma standard deviation from each

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population.

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Electron microscopic analyses were performed using a Hitachi S4800 scanning electron

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microscope (SEM) at the High Temperature Materials Laboratory at Oak Ridge National

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Laboratory (ORNL). The sample was carbon coated prior to SEM analysis and analyzed at 15.0

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kV. Ion microscopy was performed with Zeiss’ Orion NanoFab He-ion microscope at ORNL’s

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Center for Nanophase Materials Sciences.

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Results and Discussion

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Bulk mineral analyses shows the alteration zone is primarily (55 wt. %) carbonate minerals

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(i.e., calcite, aragonite, and vaterite) and residual amorphous materials (44 wt. %).20 The exact

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nature of the amorphous material is not well known, but may include unreacted or partially

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altered calcium silica hydrate (C-S-H) phases, amorphous SiO2, iron (oxy)hydroxides, and

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aluminum (oxy)hydroxides.31,32,33,13 WAXS data from this investigation shows the carbonated


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cement is mineralogically zoned with aragonite predominantly along the shale interface with

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calcite progressively increasing towards the reaction front and spiking at the edge of the reaction

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boundary (Figure 2a). There is a weak inverse relationship between calcite and aragonite

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suggesting environmental changes leading to the predominance of either aragonite or calcite.

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Lighter colored diagonal veins within the orange alteration zone are dominated by calcite,

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whereas, orange colored areas appear to be aragonite dominated. Vaterite was previously

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reported20 from bulk XRD data, but is absent in the WAXS data. This absence is most likely due

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to high detection limits associated with the WAXS setup. Carbonate mineral detection limits for

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the WAXS system are currently not known, but previous20 bulk XRD analyses on the SACROC

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sample show vaterite to be present around 7 wt.%.

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The genetic relationships among calcite and aragonite (and vaterite) in this particular sample

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are not known. Whether these carbonate minerals are from direct precipitation or a solid-state

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transformation is essential to developing a detailed model on the microenvironments associated

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with well-bore cements during CO2 flooding or sequestration. Our observations suggest that

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calcite does not form as a function of aging (the region adjacent to the shale has been carbonated

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longer than the interior regions of the cement). The data suggest a hypothesis that aragonite

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forms at the highest degrees of supersaturation and calcite forms at lower supersaturation, as it is

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possible that the pH and CO2 content of the cement pore fluid declined as CO2 penetrated the

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cement.

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The parent cement contains primarily amorphous phases with heterogeneously distributed

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portlandite (Figure 2b), both in abundance and particle orientation. There are at least two calcite

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filled fracture sets in the parent wellbore cement that are perpendicular and subparallel to the

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reaction interface. The timing associated with the calcite infilling is not documented, so it is


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difficult to determine its closure is concurrent with the CO2-induced alteration or occurred during

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a separate event. In either case, calcite-filled fractures suggest that these fractures acted as

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conduits for CO2/CO32--bearing fluids at some point during the wellbore’s lifetime.16 Fracture

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self-sealing within cement from calcite and amorphous silica precipitation has been

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demonstrated experimentally by Huerta et al.34 and Abdoulghafour et al.35. In these particular

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examples Ca2+, H4SiO4(aq), and CO32- residence times within the fracture system determine

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whether pH is buffered followed by calcite and silica precipitation.34,35 The nearly complete

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calcite infilling associated with the SACROC fractures would further suggest that fluid flow

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during this period was minimal. Interestingly, work from Walsh et al.36,37 adds that hydraulic

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apertures are further reduced due to changing mechanical properties and fracture roughness

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deformation. Portlandite within the parent cement indicates that CO2 has not diffused into the

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parent cement where fractures are not present.20

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SEM analysis of the parent cement shows textures associated with typical cement phases

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(Figure 3a). Individual unhydrated clinkers are still present in the cement phase, but the majority

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of the sample appears to be hydration products filling the voids between the clinkers (Figure 3a).

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As CO2 or H2CO3 + H2O permeated into the cement, the parent cement textures were completely

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removed as carbonates and amorphous phases formed (Figure 3b).

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Plotting X-ray scattering data with respect to analysis position allowed us to produce contour

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maps of total porosity, porosity ranges, and fractal characteristics in relationship to microscopic

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and mineralogical data. Figure 4a shows the total porosity contours overlaid on the alteration

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zone and parent wellbore cement. Scattering results from within the unaltered, parent cement

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(i.e., gray areas) indicates total porosity ranging from 0.129 to 0.473 and an average porosity of

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0.27(8) with a bimodal nanopore distribution (Figure 4b; i.e., 1 - 2 nm and 19(2) nm populations)


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representing gel nanopores and medium capillary nanopores.38,39 The average porosity

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determined via scattering data is similar to the 0.335 porosity value reported by Carey et al.20

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using He-pycnometry. These results are consistent with previous works showing good

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agreements between low-pressure gas sorption techniques (such as CO2, N2 BET and He-

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pycnometry) and scattering techniques used for porosity and pore structure determinations.40 The

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alteration zone (i.e., orange areas) shows a less heterogeneous porosity distribution, ranging from

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0.075 to 0.252, with an average porosity of 0.14(4) (Figure 4a). Reaction fronts between

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alteration zone and parent wellbore cements show a gradual porosity decrease as the parent

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cement is carbonated. High porosity zones occur in the parent cement and are farthest away from

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the alteration front, while low porosity zones are associated with the alteration zone. Empirical

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porosity-permeability relationship such as the Kozeny-Carman relation suggests that this change

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in porosity has the potential to result in permeability changes along the cement/rock interface of

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approximately seven orders of magnitude (0.075 yielding 3.8×10-11 Darcys to 0.473 yielding

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2.4×10-4 Darcys.7,41-43 Although the Kozeny-Carman model is a simplified porosity-permeability

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relationship, empirical results all indicate a strong non-linear dependence of permeability on

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porosity.7

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At the reaction interface, pore occlusion occurs primarily within the 5 - 250 nm pores. Pore

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volumes are approximately cut in half for 100 nm or larger pores, whereas a reduction in volume

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of only about a third is observed for 10 nm pores, and significant reduction for 1 - 2 nm pores

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(Figure 4b). CO2-alteration appears to completely modify cement porosity through dissolution

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and reprecipitation, thereby removing all measurable gel nanopores (i.e., 1 - 2 nm pore sizes)

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while developing a unimodal, capillary pore distribution centered at 17(2) nm (Figure 4b). Pore

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sizes greater than ~250 nm appear to have experienced little alteration. If the trend in Figure 4 is


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taken at face-value, it seems to suggest a sequence of where initial reactions, perhaps

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precipitation, lead to constriction of 10-20 nm pores (points A-B), followed by concomitant

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dilation of 10-20 nm pores and disappearance of the 1- 2 nm pores, likely due to dissolution

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(points B-C), and lastly back-filling of 10-20 nm pores, likely due to precipitation (points C-D).

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This pore-size dependence will modify permeability differently than if reactions occurred

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uniformly across pore size.

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Reaction front porosity characteristics from the SACROC wellbore cement are not consistent

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to reaction front porosities observed in previous experiments.30,31,44 Experiments where various

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cements were exposed to supercritical CO2 show sharp leading edge boundaries, characterized

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by a high-porosity zone due to acid-induced dissolution and by a low porosity zone from

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carbonate and/or silica precipitation at the front.30,31,44 These differences may suggest the

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occurrence of multiple alteration events in the SACROC sample due to multiple periods of CO2

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infiltrations and potential pulses of CO2 upwelling. The experiments, on the other hand, were

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conducted under steady pCO2 conditions and shorter reaction times (i.e., up to 1 year versus 30

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years).30,31,44

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The scattering data yield information on the fractal dimension of the pore-fluid surfaces

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present in the cement as alteration proceeds. Porous media often display two types of fractal

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microstructure: (1) mass fractals, whose dimension (Dm; power-law slope = -Dm) is indicated by

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a power-law slope of ≥ -3 on a plot of log I(Q) as a function of log Q; and (2) surface fractals

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(Ds; power-law slope = (Ds – 6)), whose slope is between -3 and -4 (Figure 5a).25,26,29,45-48 Mass

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fractals (Dm) describe the spatial pore distribution of porous solids. Compact structures typically

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have Dm ~ 3 and Dm decreases as the pore volumes become increasingly open networks.25,45,46


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For surface fractals (Ds), smooth surfaces are described with Ds = 2 (i.e., slope = -4), and,

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approach 3 with roughening (i.e., slope = -3).25,45,46

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The parent cement in this sample has a rough pore-solid interface indicated by an average

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surface fractal, Ds, of 2.96(13), and Ds decreases to 2.43(20) due to CO2-alteration (Figure 5b).

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The decrease in Ds implies an overall smoothing of the surface and possible reduction of surface

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area. Decreasing Ds has been suggested34 to proceed via preferential solute (e.g., CO32-, Ca2+)

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sorption onto rough, more energetically favorable sites, effectively annealing rough surfaces and

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reducing the number of reactive sites.

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Mass fractal scattering (i.e., Dm ) is observed over length-scales ranging from 22 nm to 630 nm

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for both the alteration zone and parent wellbore cements. Changes in Dm suggest that less

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compact, more open structures develop due to carbonation (Figure 5c). The parent cement shows

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a fairly uniform Dm ranging from 2.81 to 2.99, further suggesting a more compact and tight pore

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structure compared to the alteration zone.49,50

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Reasons for the limited infiltration of CO2 and carbonation are difficult to determine without

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detailed knowledge of the temporal variations of CO2 at the cement-shale interface. However, a

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possible explanation based on experimental data for limited CO2-brine migration is that coupled

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geochemical/geomechanical processes reduce permeability36,37, swelling of the amorphous

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material35, filling of fractures with calcium carbonate34, or due to a fluctuating/limited CO2

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supply. In any case, limited wellbore cement carbonation is consistent with experimental studies

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of cement and supercritical CO2.30-32

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Carbonation reactions result in an increase in volume with a possible change in molar volume

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up to +53.6 cm3 mol-1 (assuming a C-S-H phase with composition 3.4CaO•2SiO2•3H2O, molar

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volume = 128 cm3 mol-1) for a dewatered, carbonated cement with an amorphous silica


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byproduct.39 The observed gel and capillary nanoporosity loss is consistent with these estimates

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of complete carbonation. Gel nanopore loss coincides with C-S-H dissolution during

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carbonation. Further, C-S-H and portlandite dissolution develops new porosities that are

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subsequently closed off during CaCO3 precipitation.

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Empirical observations have shown a non-linear inverse relationship between cement porosity

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and compressive/tensile strengths51 and carbonation of cement has been found to increase

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compressive strength.52,53 However, in three-point bending tests, CO2 attack on cement yielded a

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~93% decrease in strength and ~84% decrease in elastic modulus.54 An interesting complexity

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overlying these porosity-mechanical relationships are microfracture developments near the

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reaction front due to molar volume expansion during carbonate mineral formation coupled with

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alteration zone (i.e., unaltered cement, portlandite depleted, carbonate mineral, and amorphous

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aluminosilicate zones) displaying differing mechanical properties.55,56 Carbonate crystallization

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can induce pore over-pressurization causing damage to the matrix in form of microfractures.

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Fabbri55 speculates that most of these microfractures will occur at or near the reaction interface.

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Many instances these microfractures will not be included in the porosity calculations and

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therefore can make porosity-mechanical behavior relationships difficult to quantify. Additional

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to the microfracture effects, Hangx56 has shown that alteration zones from carbonation displays

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24-56% mechanical weakening in the portlandite-depleted and 150-181% mechanical

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strengthening in the carbonation zones as compared to neat cement.

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Environmental Implications

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The ultimate environmental implications of this work are if carbonation reactions increase, or

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decrease, CO2 storage security in cement. A review of cement carbonation behavior in relation


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to CO2 sequestration indicates that carbonation of wellbore cement reduces permeability,10

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consistent with the results on total porosity in this study. This would enhance CO2 storage

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security. Coupled to this may be variable impacts on mechanical strength of the cement, but the

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strength requirements for wellbore cement are limited.10 This work shows that reactions during

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cement carbonation reduced the gel and capillary nanoporosities, but did not significantly alter

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larger-scale porosity. This raises the importance of determining how the distribution of pore sizes

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changes in context to the total porosity and how this affects overall permeability. Furthermore,

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CO2 permeation and alteration was limited to only 8-10 mm (0.3 mm year-1) over the 30 years of

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CO2 interaction with the wellbore cement. The small penetration depth supports work suggesting

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that cement matrix leakage is not a primary leakage pathway.33 These observations can be related

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to reservoir rock and caprock properties as well as cement. Pore-scale dependent reactions

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coupled with a nonuniform alteration of the pore-sized distribution during reactive transport of

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CO2 have the potential for compounding effect on the storage security of subsurface CO2.2,3

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Acknowledgment

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This work was supported as part of the Center for Nanoscale Control of Geologic CO2, an

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Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science,

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Basic Energy Sciences under Award #DE-AC02-05CH11231. This research used resources of

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the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User

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Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract

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#DE-AC02-06CH11357. JWC acknowledges support from the DOE National Energy

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Technology Laboratory (NETL) under Grant #FE-371-14-FY16, which is managed and

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administered by Los Alamos National Laboratory and funded by DOE/NETL and cost/sharing


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partners. He-ion microscopy was conducted at the Center for Nanophase Materials Sciences,

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which is a DOE Office of Science User Facility. The authors would like to thank Larry Lake for

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providing production data.

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REFERENCES

276

(1) Gaus, I. Role and impact of CO2-rock interactions during CO2 storage in sedimentary rocks.

277

Int. J. Greenhouse Gas Control. 2010, 4, 73-89.

278

(2) Stack, A.G.; Fernandez-Martinez, A.; Allard, L.F.; Banuelos, J.L.; Rother, G.; Anovitz, L.M.;

279

Cole, D.R.; Waychunas, G.A. Pore-size-dependent calcium carbonate precipitation

280

controlled by surface chemistry. Environ. Sci. Technol. 2014, 48, 6177-6183.

281 282 283

(3) Stack, A.G. Pore-Size Dependent Precipitation Reactions: A Geochemical Frontier. Rev. Mineral. Geochem. 2015, 80, 165-190. (4) Borgia, A.; Pruess, K.; Kneafsey, T.J.; Oldenburg, C.M.; Pan, L. Numerical simulation of salt

284

precipitation in the fractures of a CO2-enhanced geothermal system. Geothermics. 2012,

285

44, 13–22.

286 287

(5) Cohen, Y. and Rothman, D.H. Mechanisms for mechanical trapping of geologically sequestered carbon dioxide. Proc. R. Soc. A. 2015, 471, 20140853.

288

(6) Freeze, R.A. and Cherry, J.A. Groundwater. Prentice Hall: Englewood Cliffs, NJ. 1979.

289

(7) Zhang, S.; DePaolo, D.J.; Xu, T.; Zheng, L. Mineralization of carbon dioxide sequestered in

290

volcanogenic sandstone reservoir rocks. Int. J. Greenhouse Gas Control. 2013, 18, 315-

291

328.

292

(8) Gibson-Poole, C.M.; Svendsen, L.; Underschultz, J.; Watson, M.N.; Ennis-King, J.; van

293

Ruth, P.J.; Nelson, E.J.; Daniel, R.F.; Cinar, Y. Site characterization of a basin-scale CO2


13


Page 14 of 25

294

geological storage system: Gippsland Basin, southeast Australia. Environ. Geol. (N. Y.).

295

2008, 54, 1583-1606.

296

(9) Bear, J. Dynamics of Fluids in Porous Media. Dover: New York. 1988.

297

(10) Steefel, C.; Molins, S.; Trebotich, D. Pore scale processes associated with subsurface CO2

298 299 300

injection and sequestration. Rev. Mineral. Geochem. 2013, 77, 259-303. (11) Berg, C.F. Permeability description by characteristic length, tortuosity, constriction, and porosity. Transp. Porous Med. 2014, 103, 381-400.

301

(12) Gasda, S.E.; Bachu, S.; Celia, M.A. Spatial characterization of the location of potentially

302

leaky wells penetrating a deep saline aquifer in a mature sedimentary basin.

303

Environmental Geology. 2004, 46, 707-720.

304 305

(13) Carey, J. W. Geochemistry of wellbore integrity in CO2 sequestration: Portland cementsteel-brine-CO2 interactions. Rev. Mineral. Geochem. 2013, 77, 505-539.

306

(14) Smith, M.M.; Sholokhova, Y.; Hao, Y.; Carroll, S.A. Evaporite caprock integrity: An

307

experimental study of reactive mineralogy and pore-scale heterogeneity during brine-CO2

308

exposure. Environ. Sci. Technol. 2012, 47, 262-268.

309

(15) Kampman, N.; Busch, A.; Bertier, P.; Snippe, J.; Hangx, V.; Di, Z.; Rother, G.; Harrington,

310

J.F.; Evans, J.P.; Maskell, A.; Chapman, H.J.; Bickle, M.J. Obersvational evidence

311

confirms modeling of the long-term integrity of CO2-reservoir caprocks. Nature

312

Communications, 2016, 7, 12268.

313 314

(16) Mito, S.; Xue, Z.; Ohsumi, T. Case study of geochemical reactions at the Nagaoka CO2 injection site, Japan. Int. J. Greenhouse Gas Control. 2008, 2, 309-318.


14

Page 15 of 25


315

(17) Zakharova, N.V.; Goldberg, D.S.; Sullivan, E.C.; Herron, M.M.; Grau, J.A. Petrophysical

316

and geochemical properties of Columbia River flood basalt: Implications for carbon

317

sequestration. Geochem., Geophys., Geosyst. 2012, 13, Q11001.

318

(18) Gislason, S.R.; Wolff-Boenisch, D.; Stefansson, A.; Oelkers, E.H.; Gunnlaugsson, E.;

319

Sigurdardottir, H.; Sigfusson, B.; Broecker, W.S.; Matter, J.M.; Stute, M.; Axelsson, G.;

320

Fridriksson, T. Mineral sequestration of carbon dioxide in basalt: A pre-injection

321

overview of the CarbFix project. Int. J. Greenhouse Gas Control. 2010, 4, 537-545.

322

(19) Matter, J.M.; Stute, M.; Snæbjörnsdottir, S.O.; Oelkers, E.H.; Gislason, S.R.; Aradottir,

323

E.S.; Sigfusson, B.; Gunnarsson, I.; Sigurdardottir, H.; Gunnarsson, E.; Axelsson, G.;

324

Alfredsson, H.A.; Wolff-Boenisch, D.; Mesfin, K.; Taya, D.F.; Hall, J.; Dideriksen, K.;

325

Broecker, W.S. Rapid carbon mineralization for permanent disposal of anthropogenic

326

carbon dioxide emissions. Science, 2016, 352, 1312-1314.

327

(20) Carey, J.W.; Wigand, M.; Chipera, S.J.; WoldeGabriel, G.; Pawar, R.; Lichtner, P.C.;

328

Wehner, S.C.; Raines, M.A.; Guthrie, G.D. Analysis and performance of oil well cement

329

with 30 years of CO2 exposure from the SACROC Unit, West Texas, USA. Int. J.

330

Greenhouse Gas Control. 2007, 1, 75-85.

331

(21) Johnson, J. W.; Nitao, J. J.; Knauss, K. G. Reactive transport modeling of CO2 storage in

332

saline aquifers to elucidate fundamental processes, trapping mechanisms and

333

sequestration partitioning. Spec. Publ. - Geol. Soc. London. 2004, 233, 107-128.

334

(22) Ilavsky, J.; Jemian, P.R.; Allen, A.J.; Zhang, F.; Levine, L.E.; Long, G.G. Ultra-small-angle

335

X-ray scattering at the Advanced Photon Source. J. Appl. Crystallogr. 2009, 42, 469-479.

336

(23) Ilavsky J. and Jemian, P. R. Irena: tool suite for modeling and analysis of small-angle

337

scattering. J. Appl. Crystallogr. 2009, 42, 347-353.


15


338 339

Page 16 of 25

(24) Ilavsky, J. Nika: software for two-dimensional data reduction. J. Appl. Crystallogr. 2012, 45, 324-328.

340

(25) Wang, H.-W.; Anovitz, L.; Burg, A.; Cole, D.R.; Allard, L.F.; Jackson, A.J.; Stack, A.G.;

341

Rother, G. Multi-scale characterization of pore evolution in a combustion metamorphic

342

complex, Hatrurim basin, Israel: Combining (ultra) small-angle neutron scattering and

343

image analysis. Geochim. Cosmochim. Acta. 2013, 121, 339-362.

344

(26) Anovitz, L.M.; Cole, D.R.; Rother, G.; Allard, L.F.; Jackson, A.J.; Littrell, K.C. Diagenetic

345

changes in macro- to nano-scale porosity in the St. Peter Sandstone: An (ultra) small

346

angle neutron scattering and backscattered electron imaging analysis. Geochim.

347

Cosmochim. Acta. 2013, 102, 280-305.

348 349 350 351 352 353

(27) Beaucage, G. Approximations leading to a unified exponential/power-law approach to small-angle scattering. J. Appl. Crystallogr. 1995, 28, 717-728. (28) Beaucage, G. Small-angle scattering from polymeric mass fractals of arbitrary mass-fractal dimension. J. Appl. Crystallogr. 1996, 29, 134-146. (29) Anovitz, L.M and Cole, D.R. Characterization and analysis of porosity and pore structures. Rev. Mineral. Geochem. 2015, 80, 61-164.

354

(30) Kutchko, B.G.; Strazisar, B.R.; Dzombak, D.A.; Lowry, G.V.; Thaulow, N. Degradation of

355

well cement by CO2 under geologic sequestration conditions. Environ. Sci. Technol.

356

2007, 41, 4787-4792.

357

(31) Kutchko, B.G.; Strazisar, B.R.; Lowry, G.V.; Dzombak, D.A.; Thaulow, N. Rate of CO2

358

attack on hydrated class H well cement under geologic sequestration conditions. Environ.

359

Sci. Technol. 2008, 42, 6237-6242.


16

Page 17 of 25


360

(32) Kutchko, B.G.; Strazisar, B.R.; Huerta, N.; Lowry, G.V.; Dzombak, D.A.; Thaulow, N.

361

CO2 reaction with hydrated class H well cement under geologic sequestration conditions:

362

Effects of flyash admixtures. Environ. Sci. Technol. 2009, 43, 3947-3952.

363

(33) Carroll, S.; Carey, J.W.; Dzombak, D.; Huerta, N.J.; Li, L.; Richard, T.; Um, W.; Walsh, S.;

364

Zhang, L. Review: Role of chemistry, mechanics, and transport on well integrity in CO2

365

storage environments. Int. J. Greenhouse Gas Control. 2016, 49, 149-160.

366

(34) Huerta, N.J.; Hesse, M.A.; Bryant, S.L.; Strazisar, B.R.; Lopano, C. Reactive transport of

367

CO2-saturated saturated in a cement fracture: Application to wellbore leakage during

368

geologic CO2 storage. Int. J. Greenhouse Gas Control. 2016, 44, 276-289.

369

(35) Abdoulghafour, H.; Luquot, L.; Gouze, P. Characterization of the mechanisms controlling

370

the permeability changes of fractured cements flowed through by CO2-rich brine.

371

Environ. Sci. Technol. 2013, 47, 10332-10338.

372

(36) Walsh, S.D.C.; Mason, H.E.; Du Frane, W.L.; Carroll, S.A. Experimental calibration of a

373

numerical model describing the alteration of cement/caprock interfaces by carbonated

374

brine. Int. J. Greenhouse Gas Control. 2014, 22, 176-188.

375

(37) Walsh, S.D.C.; Mason, H.E.; Du Frane, W.L.; Carroll, S.A. Mechanical and hydraulic

376

coupling in cement-caprock interfaces exposed to carbonated brine. Int. J. Greenhouse

377

Gas Control. 2014, 25, 109-120.

378 379 380 381

(38) Mindess, S.; Young, J.F.; Darwin, D. Concrete, 2nd Edition. Pearson: London, England, 2002. (39) Jennings, H.M. and Tennis, P.D. Model for the developing microstructure in Portland cement pastes. J. Am. Ceram. Soc. 1994, 77, 3161-3172.


17


Page 18 of 25

382

(40) Clarkson, C.R.; Solano, N.; Bustin, A.M.M.; Chalmers, G.R.L.; He, L.; Melnichenko, Y.B.;

383

Radlinski, A.P.; Blach, T.P. Pore structure characterization of North American Shale gas

384

reservoirs using USANS/SANS, gas adsorption, and mercury intrusion. Fuel. 2013, 103,

385

606-616.

386 387 388 389 390 391

(41) Carman, P.C. Fluid flow through granular beds. Transactions of the Institute of Chemical Engineers. 1937, 15, S32-S48. (42) Goto, S.; Roy, D.M. The effect of W/C ratio and curing temperature on the permeability of hardened cement paste. Cem. Concr. Res. 1981, 11, 575-579. (43) Cui, L.; Cahyadi, J.H. Permeability and pore structure of OPC paste. Cem. Concr. Res. 2001, 31, 277-282.

392 393

(44) Rimmele, G.; Barlet-Gouedard, V.; Porcherie, O.; Goffe, B.; Brunet, F. Heterogeneous

394

porosity distribution in Portland cement exposed to CO2-rich fluids. Cem. Concr. Res.

395

2008, 38, 1038-1048.

396

(45) Martin, J.E. and Hurd, A.J. Scattering from fractals. J. Appl. Crystallogr. 1987, 20, 61-78.

397

(46) Allen, A.J.; Baston, A.H.; Wilding, C.R. Small angle neutron scattering studies of pore and

398

gel structures diffusivity, permeability and damage effects. Pore Structure and

399

Permeability of Cementitious Materials. 1989, 137, 119-125

400

(47) Anovitz, L.M.; Lynn, G.W.; Cole, D.R.; Rother, G.; Allard, L.F.; Hamilton, W.A.; Porcar,

401

L.; Kim, M.-H. A new approach to quantification of metamorphism using ultra-small and

402

small angle neutron scattering. Geochim. Cosmochim. Acta. 2009, 73, 7303-7324

403

(48) Anovitz L.M.; Cole D.R.; Jackson A.J.; Rother G.; Littrell K.C.; Allard L.F.; Pollington

404

A.D.; Wesolowski D.J. Effect of Quartz Overgrowth Precipitation on the Multiscale


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405

Porosity of Sandstone: A (U)SANS and Imaging Analysis. Geochim. Cosmochim. Acta.

406

2015, 153, 199-222.

407

(49) Beddoe, R.E. and Lang, K. Effect of moisture on fractal dimension and specific surface of

408

hardened cement paste by small-angle x-ray scattering. Cem. Concr. Res. 1994, 24, 605-

409

612.

410 411 412 413

(50) Winslow, D.; Bukowski, J.M.; Young, J.F. The fractal arrangement of hydrated cement paste. Cem. Concr. Res. 1995, 25, 147-156. (51) Chen, X.; Wu, S.; Zhou, J. Influence of porosity on compressive and tensile strength of cement mortar. Construction and Building Materials. 2013, 40, 869-874.

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(52) Taylor, H. F. W. Cement Chemistry. Academic Press: London, 1990.

415

(53) Takla, I.; Burlion, N.; Shao, J.-F.; Saint-Marc, J.; Garnier, A. Effects of the storage of CO2

416

on multiaxial mechanical and hydraulic behaviors of oil-well cement. J. Mater. Civ. Eng.

417

2011, 23, 741-746.

418

(54) Li, Q.; Lim, Y.M.; Flores, K.M.; Kranjc, K.; Jun, Y.-S. Chemical reactions of portland

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cement with aqueous CO2 and their impacts on cement’s mechanical properties under

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geologic CO2 sequestration conditions. Environ. Sci. Technol. 2015, 49, 6335-6343.

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(55) Fabbri, A.; Corvisier, J.; Schubnel, A.; Brunet, F.; Goffe, B.; Rimmele, G.; Barlet-

422

Gouedard, V. Effect of carbonon the hydro-mechanical properties of Portland cements.

423

Cement and Concrete Research. 2009, 39, 1156-1163.

424

(56) Hangx, S.J.T.; van der Linden, A.; Marcelis, F.; Liteanu, E. Defining the brittle failure

425

envelopes of individual reaction zones observed in CO2-exposed wellbore cement. Env.

426

Sci. Tech. 2016, 50, 1031-1038.

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List of Figures

429 430

Figure 1. A) Production and injection history from well 49-6 within the SACROC unit (L. Lake,

431

personal communication, 2015). B) Image from the sliced sample with parent wellbore cement

432

(grey), CO2 alteration zone (orange), and shale interfaces (modified from Carey et al.16).

433


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Page 21 of 25


434

A

p

p

p

p

p

435

B

p

436

Figure 2. A) Diffraction data from the WAXS analyses. Vertical graphs show raw integrated

437

peak intensities from the calcite 104 (red), aragonite 111 (purple), and portlandite 110, 101

438

(blue) indices. For clarity, the spots from the WAXS scans are not presented, but the vertical

439

graphs are present in the analysis locations. B) Helium-ion photomicrograph showing portlandite

440

plates (P, on edge) within the parent cement. Cubic features are probably halite.

441


21


A

200 µm

B

200 µm

Page 22 of 25

442 443

Figure 3. Backscatter-SEM images showing the different textural and composition zones within

444

the SACROC sample. A) Grey, parent cement shows unhydrated clinkers with calcium silica

445

hydrate between clinkers. B) The carbonated region displays reworked textures with most of the

446

parent cement textures removed.

447


22

Page 23 of 25


448 449

Figure 4. A) Contours of total porosity distribution associated with the SACROC wellbore

450

cement sample showing changes in porosity across the reaction interface between relatively

451

unaltered gray cement (bottom) and altered, orange zone (top). B) Individual porosity

452

distributions for points along the X=35 mm transect. Porosity of the parent cement (point A) has

453

a bimodal distribution with peak frequencies at 1 - 2 nm and 19(2) nm size distributions.

454

Reaction interface shows similar size distribution to the parent cement with a significant loss of

455

the larger pore sizes. Porosities within the orange alteration zone (points C and D) are markedly

456

altered and show a unimodal distribution with 17(2) nm pore sizes. Error bars represent

457

estimated uncertainty in the collected scattered X-ray intensity values propagated to the pore

458

volume distribution.


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Page 24 of 25

459 460

Figure 5. A) (U)SAXS plot of log I(Q) as a function of log Q for a parent cement (black curve;

461

x35, y59) and carbonated cement (green curve; x35, y48). Red curves overlaying each scattering

462

curve are the modeled scattering curve from the Unified Fit modeling package. B) Surface fractal

463

dimension approaching Ds = 2 within the alteration zone. Carbonation is smoothing the pore-


24

Page 25 of 25


464

solid interface. C) Mass fractal dimensions across the alteration zone and parent cement. The

465

mass fractal is much more variable in the carbonation zone (both higher and lower).

466 467

For Table of Contents Only

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25

Wellbore Cement Porosity Evolution in Response to Mineral Alteration

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