Pore-water squeezing from indurated shales

Mazurek, Martin; Oyama, Tadasu; Wersin, Paul; Alt‐Epping, Peter

doi:10.1016/j.chemgeo.2015.02.008

Cited by 49 publications

(28 citation statements)

References 52 publications

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“…It is worth noting that while Cl -/Br -ratios at Mont Terri and Mont Russelin are close to marine values (around 290 g/g), this is not the case for Opalinus Clay in the more eastern parts of northern Switzerland where values up to 1000 are observed (borehole Schlattingen: Mazurek et al 2015;boreholes Weiach, Riniken, Schafisheim: Meier and Mazurek 2011). Here, the Cl -/Br -ratio points to non-marine components of salinity, e.g.…”

Section: Plausibility Of a Tertiary Component In Watersmentioning

confidence: 99%

Pore-water evolution and solute-transport mechanisms in Opalinus Clay at Mont Terri and Mont Russelin (Canton Jura, Switzerland)

Mazurek

Haller

2017

Swiss J Geosci

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Data pertinent to pore-water composition in Opalinus Clay in the Mont Terri and Mont Russelin anticlines have been collected over the last 20 years from longterm in situ pore-water sampling in dedicated boreholes, from laboratory analyses on drillcores and from the geochemical characteristics of vein infills. Together with independent knowledge on regional geology, an attempt is made here to constrain the geochemical evolution of the pore-waters. Following basin inversion and the establishement of continental conditions in the late Cretaceous, the Malm limestones acted as a fresh-water upper boundary leading to progressive out-diffusion of salinity from the originally marine pore-waters of the Jurassic low-permeability sequence. Model calculations suggest that at the end of the Palaeogene, pore-water salinity in Opalinus Clay was about half the original value. In the Chattian/Aquitanian, partial evaporation of sea-water occurred. It is postulated that brines diffused into the underlying sequence over a period of several Myr, resulting in an increase of salinity in Opalinus Clay to levels observed today. This hypothesis is further supported by the isotopic signatures of SO 4 2-and 87 Sr/ 86 Sr in current pore-waters. These are not simple binary mixtures of sea and meteoric water, but their Cl -and stable water-isotope signatures can be potentially explained by a component of partially evaporated sea-water. After the re-establishment of fresh-water conditions on the surface and the formation of the Jura Fold and Thrust Belt, erosion caused the activation of aquifers embedding the low-permeability sequence, leading to the curved profiles of various pore-water tracers that are observed today. Fluid flow triggered by deformation events during thrusting and folding of the anticlines occurred and is documented by infrequent vein infills in major fault structures. However, this flow was spatially focussed and of limited duration and so did not markedly affect the bulk pore-water.

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Section: Plausibility Of a Tertiary Component In Watersmentioning

confidence: 99%

Pore-water evolution and solute-transport mechanisms in Opalinus Clay at Mont Terri and Mont Russelin (Canton Jura, Switzerland)

Mazurek

Haller

2017

Swiss J Geosci

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“…Laboratory pH of the early aliquots of 7.4-7.5 are in agreement with one measured in-line of 7.5, just after taking a first sample aliquot. Of note are substantial initial concentrations of organic carbon (60 mg/l), and this was also observed in subsequent advective displacement experiments [13,14] as well as in pore water squeezing [20]. Improved analytical capabilities revealed in later experiments that approximately half of the dissolved TOC is present in form of carboxylic acids like acetate, formate, and lactate.…”

Section: Anion Exclusion Effect and Controls On Pore Watermentioning

confidence: 76%

“…Both methods do induce certain artefacts. One issue is the observed salinity gradient obtained from subsequent squeezing aliquots [20], a consequence of anion exclusion, that render the composition of a squeezed aliquot sensitive to the chosen squeezing conditions. Both methods appear to mobilize organic compounds and this is evident in substantial concentrations of low-molecular-weight organic acids (early aliquots in advective displacement) that are much higher than what can be recovered in aqueous extracts or during long-term borehole sampling.…”

Section: Discussionmentioning

confidence: 99%

Advective Displacement Method for the Characterisation of Pore Water Chemistry and Transport Properties in Claystone

Mäder

2018

Geofluids

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The advective displacement method applies large hydraulic gradients to a confined rock core sample to yield small aliquots of the preserved in situ pore water, applicable to aquitard rocks with hydraulic conductivities as low as 10 −14 m/s. Examples from argillaceous rocks indicate that only minor artefacts are induced and that analytical methods optimized for small aliquots provide a comprehensive chemical and isotopic characterisation. Multicomponent transport properties are derived from extending experimental time and using a traced artificial pore water for injection. Examples include quantification of the anion exclusion effect that can even resolve a small difference between transport properties for chloride and bromide in claystone. Controls by mineral saturation and cation exchange processes are also constrained by data from this approach. Technical details are provided for construction, material selection, components, sensors, and analytical issues.

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“…In some cases it is possible to directly sample porewater by collecting seepage, and this is thought to yield samples that are most representative of the mobile water fraction [29,50], but the sampling durations are very long, on the order of months to years [51]. Indirect methods are also available, including out-diffusion [52][53][54], ultracentrifugation [55], high-pressure squeezing [48,56,57], crushing and leaching [48,[58][59][60], advective displacement [9], and absorption by paper [61]. These methods are susceptible to artefacts from disturbance of the equilibrium between minerals, bound water, and mobile water [62] that result in mineral dissolution [57], cation exchange [63], and changes in DDL thickness [64].…”

Section: Introductionmentioning

confidence: 99%

Measurement of Cl⁻ : Br⁻Ratios in the Porewater of Clay-Rich Rocks—A Comparison of the Crush-and-Leach and the Paper-Absorption Methods

Celejewski

Barton

2018

Geofluids

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Characterization of porewater chemistry in low-permeability, clay-rich rocks provides insights into solute transport mechanisms and the origin and residence time of porewater. Extraction of porewater for chemical quantification is challenging, and several methods have been applied including squeezing, advective displacement, crush and leach, and a relatively new technique that extracts porewater by absorption into a cellulosic paper by capillary action. Here we compare porewater Cl − and Br − mass ratios from samples using the paper-absorption and crush-and-leach techniques. Samples were obtained from Upper Ordovician shales in the Michigan Basin in Ontario, the Opalinus Clay at the Mont Terri Rock Laboratory in Switzerland, and the Upper Ordovician Lorraine Group shale in southern Quebec. The data display consistent and reproducible differences among methods for Cl − and Br − mass ratios, with the paper-absorption method producing systematically lower Cl − : Br − ratios. The observed differences in Cl − : Br − ratios are attributed primarily to anion exclusion effects which are stronger for Br − than for Cl − , resulting in higher Br − concentrations in the largest pores that are preferentially sampled by the paper-absorption technique. In addition, calculations suggest that Cl − is more effective than Br − in forming ion pairs and clusters with neutral or positive charge which can enter the diffuse double layer. This causes a further decrease in the Cl − : Br − ratios for the mobile water. One important message from this work is that different extraction methods should not be expected to converge on a unique porewater Cl − : Br − ratio because each method reflects different proportions of the interlayer, diffuse double layer, and mobile fractions of porewater.in the Opalinus Clay at Mont Terri, Switzerland, the Boom Clay at Essen, Belgium, and the Couche Silteuse at Marcoule, France, by plotting spatial profiles of tracers across these formations. The data allowed for determination of transport processes and porewater residence times.Sampling porewater from low-permeability, clay-rich formations for chemical quantification is a challenging endeavor. This is in part due to the small volumes available for extraction and because of the complexity of waterclay interactions [24]. Negatively charged clay surfaces are balanced by cation-rich water in direct contact with the surface [25,26]. This cation-rich water is "bound water" and occupies the interlayer positions in clay minerals or the diffuse double layer (DDL) that surrounds mineral surfaces,

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Pore-water squeezing from indurated shales

Cited by 49 publications

References 52 publications

Pore-water evolution and solute-transport mechanisms in Opalinus Clay at Mont Terri and Mont Russelin (Canton Jura, Switzerland)

Pore-water evolution and solute-transport mechanisms in Opalinus Clay at Mont Terri and Mont Russelin (Canton Jura, Switzerland)

Advective Displacement Method for the Characterisation of Pore Water Chemistry and Transport Properties in Claystone

Measurement of Cl⁻ : Br⁻Ratios in the Porewater of Clay-Rich Rocks—A Comparison of the Crush-and-Leach and the Paper-Absorption Methods

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Pore-water squeezing from indurated shales

Cited by 49 publications

References 52 publications

Pore-water evolution and solute-transport mechanisms in Opalinus Clay at Mont Terri and Mont Russelin (Canton Jura, Switzerland)

Pore-water evolution and solute-transport mechanisms in Opalinus Clay at Mont Terri and Mont Russelin (Canton Jura, Switzerland)

Advective Displacement Method for the Characterisation of Pore Water Chemistry and Transport Properties in Claystone

Measurement of Cl− : Br−Ratios in the Porewater of Clay-Rich Rocks—A Comparison of the Crush-and-Leach and the Paper-Absorption Methods

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Measurement of Cl⁻ : Br⁻Ratios in the Porewater of Clay-Rich Rocks—A Comparison of the Crush-and-Leach and the Paper-Absorption Methods