FIB-SEM and TEM Investigations of an Organic-rich Shale Maturation Series from the Lower Toarcian Posidonia Shale, Germany&lt;subtitle&gt;Nanoscale Pore System and Fluid-rock Interactions&lt;/subtitle&gt;

Bernard, Sylvain; Brown, Leon D.; Wirth, Richard; Schreiber, Anja; Schulz, Hans-Martin; Horsfield, Brian; Aplin, Andrew C.; Mathia, Eliza

doi:10.1306/13391705m1023583

Cited by 35 publications

(37 citation statements)

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“…A similar trend was observed by Bernard et al . (). They found slightly higher porosities between 10% and 14% for the Wickensen, 4% and 6% for the Harderode, and 9% and 12% for the Haddessen samples, based on both gravimetric (Archimedes) and volumetric (mercury injection) methods.…”

Section: Resultsmentioning

confidence: 97%

“…According to Bernard et al . (), a significant fraction of the pore space of the Posidonia shales is in the clay minerals. Clay minerals are known to have an electrically “active” surface layer that can supply ions in aqueous solutions (e.g., in Mitchell ).…”

Section: Discussionmentioning

confidence: 98%

“…Of these minerals the only well conducting ones are the pyrite minerals, but in the Posidonia black shale, these are found in isolated clusters (Bernard et al . ), which are not interconnected and, therefore, cannot provide regional electrical induction. Furthermore, the composition and electrical resistivity of the organic matter that is found at the grain boundaries depends on thermal maturity.…”

Section: Discussionmentioning

confidence: 99%

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The electrical conductivity of Posidonia black shales — from magnetotelluric exploration to rock samples

Adão

Ritter

Spangenberg

2015

Geophysical Prospecting

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A B S T R A C TWe carried out a magnetotelluric field campaign in the South-East Lower Saxony Basin, Germany, with the main goal of testing this method for imaging regional Posidonia black shale sediments. Two-dimensional inversion results of the magnetotelluric data show a series of conductive structures correlating with brine-saturated sediments but also with deeper, anthracitic Westphalian/Namurian coals. None of these structures can be directly related with the Posidonia black shale, which appears to be generally resistive and therefore difficult to resolve with the magnetotelluric method. This assumption is supported by measurements of electrical resistivity on a set of Posidonia shale samples from the Hils syncline in the Lower Saxony basin. These rock samples were collected in shallow boreholes and show immature (0.53% Ro), oil (0.88% Ro), and gas (1.45% Ro) window thermal maturities. None of the black shale samples showed low electrical resistivity, particularly those with oil window maturity show resistivity exceeding 10 4 m. Moreover, we could not observe a direct correlation between maturity and electrical resistivity; the Harderode samples showed the highest resistivity, whereas the Haddessen samples showed the lowest. A similar trend has been seen for coals in different states of thermal maturation. Saturation of the samples with distilled and saline water solutions led to decreasing electrical resistivity. Moreover, a positive correlation of electrical resistivity with porosity is observed for the Wickensen and Harderode samples, which suggests that the electrical resistivity of the Posidonia black shale is mainly controlled by porosity.

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Section: Resultsmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

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The electrical conductivity of Posidonia black shales — from magnetotelluric exploration to rock samples

Adão

Ritter

Spangenberg

2015

Geophysical Prospecting

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“…At all maturities, most of this porosity is associated with the carbonate matrix; in immature samples, this is primarily within microfossil tests and coccolith‐rich fecal pellets, which become filled with migrated bitumen in the oil window. Into the gas window, dissolution and reprecipitation of carbonate results in a rigid matrix in which large pores can be formed and retained because of continuing expulsion of petroleum, and the densification and gasification of retained OM (Bernard et al, , ; Mathia et al, ; Milliken et al, ; Modica & Lapierre, ; Pommer & Milliken, ).…”

Section: Discussionmentioning

confidence: 99%

“…The drive to characterize and predict the pore systems of fine‐grained sediments has increased markedly in the last decade because of their exploitation as major hydrocarbon reservoirs. Recent studies have used microscopy, MICP, gas sorption, and small‐angle scattering techniques both alone and in combination to measure and infer aspects of pore structure and connectivity (e.g., Bernard et al, , , ; Chalmers & Bustin, ; Chalmers et al, ; Clarkson et al, , ; Curtis et al, ; Klaver, Desbois, Littke, & Urai, ; Klaver, Desbois, Urai, & Littke, ; Ko et al, ; Fishman et al, ; King et al, ; Loucks et al, ; Mastalerz et al, ; Milliken et al, ; Modica & Lapierre, ; Ross & Bustin, ). These studies have started to unravel the nature of mudstone pore systems but have rarely quantified the pore architecture as a function of lithology, texture, and thermal maturity.…”

Section: Introductionmentioning

confidence: 99%

Influence of Clay, Calcareous Microfossils, and Organic Matter on the Nature and Diagenetic Evolution of Pore Systems in Mudstones

et al. 2019

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Mudstones exert a fundamental control on the flow of both aqueous and nonaqueous fluids in sedimentary basins. Predicting their flow and storage properties requires an understanding of pore size and connectivity, yet there are very few quantitative descriptions of pore systems of mineralogically and texturally well-characterized mudstones. We use a combination of electron microscopy, mercury injection capillary pressure porosimetry, and CO 2 sorption methods to generate a quantitative description of the size distribution, connectivity, and evolution of pore systems in a sequence of Posidonia Shale mudstones buried to 100-180°C. We place the pore data into a detailed mineralogical, petrographical, and textural context to show that the nature and evolution of porosity and pore systems can be described in terms of associations with clay-rich, microfossil-rich, and organic matter-rich domains, common to many mudstones. Pore size distributions are described by power laws, and pore systems are well connected across the full nanometermicrometer spectrum of pore sizes. However, connected networks occur primarily through pores <10 nm radius, with typically 20-40% of total porosity associated with pores with radii <~3 nm, within both organic matter and the clay matrix. Clay-rich, microfossil-rich, and organic matter-rich domains have distinct pore size distributions which evolve in very different ways with increasing thermal maturity. We suggest that the flow of aqueous and nonaqueous fluids depends not only on the overall connectivity of pores but also the larger-scale connectivity and wetting state of clay-rich, microfossil-rich, and organic matter-rich domains.Plain Language Summary Mudstones are Cinderella sediments: important but neglected. The most abundant sediment type, they act as unconventional oil and gas reservoirs, as top seals to conventional hydrocarbon reservoirs, and as critical barriers to the leakage of CO 2 and radionuclides from underground storage sites. Risking and predicting flow and leakage through these rocks requires a quantitative description of pore systems and their connectivity. This is challenging since even the biggest pores in shales are smaller than a micron, with many pores only a few nanometers in size. Our work uses a combination of techniques to characterize and quantify the nanoporous nature of shales. Pores are generally smaller than 100 nm but are well connected, but mainly through throats less than 20 nm. We have also placed the pore system data into a geological framework in order to be more predictive about the pore systems of shales generally. By quantifying the nature of pores in the various mineral and organic building blocks of shales we can consider the larger scale flow properties of shales and thus their potential either to transmit fluid (useful for a shale gas reservoir) or to retain fluid (useful for a CO 2 or nuclear waste storage site).Quantitative descriptions of pore systems underpin our understanding of the storage and flow of both aqueous and nonaqueous fluids in...

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Multiproxy geochemical characterization of Kommugudem Formation, Krishna Godavari Basin, India: Implication on hydrocarbon potential and shale brittleness

Kala

Devaraju

et al. 2021

Geological Journal

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The unconventional reserves are vital future energy resources and globally augmented interest endeavours the discovery of gas and oil-rich shales. The Kommugudem Formation, Krishna Godavari Basin was evaluated based on sample laboratory and well log studies from six wells deciphering mineralogical and organic geochemical parameters to provide an understanding of hydrocarbon potential and brittleness. Kommugudem Formation constitutes Type III kerogen dominantly with high total organic carbon (TOC) and T max indicating the presence of high organic matter. The mean vitrinite reflectance indicates mature to post-mature shale majorly in the gas generation window. Fourier transform infrared spectroscopy functional group investigation revealed the presence of aromatics and aliphatics with a higher degree of abundance owing to higher TOC content. The basic well logs recorded in the studied region are used to estimate the continuous TOC and porosity of the formation and corroborate with laboratory core data. Petrographic, X-ray diffraction, and field emission scanning electron microscopy studies revealed the presence of dominantly siliceous mineral matter with relatively lower clay and carbonates. Organic mudstone classification indicates formation is dominantly silica-dominated lithotype and clay-rich siliceous mudstone. Microfractures and micropores are observed in mineral and organic matter that may act as storage sites for hydrocarbons. Kommugudem Formation on the basis of mineralogy indicates compositional analogy with brittle zones of Barnett Shale Formation. The high mineralogical brittleness index of the Kommugudem Formation indicates good conditions for hydraulic fracturing. The present investigation demonstrates excellent hydrocarbon generation potential and good brittleness in wells A and B while C, D, E, and F have relatively lower potential and may have low gas and oil sources.K E Y W O R D S hydrocarbon potential, Krishna Godavari Basin, mineralogical brittleness index, shale gas 1 | INTRODUCTION Shale gas reserves are a globally prospective energy source and in India, shale gas resources exploration is in the emerging stage. India has an estimation of 96 Tcf of risked, technically recoverable shale gas reserves with the most likely shale gas reserves in regions of Cambay,

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FIB-SEM and TEM Investigations of an Organic-rich Shale Maturation Series from the Lower Toarcian Posidonia Shale, Germany<subtitle>Nanoscale Pore System and Fluid-rock Interactions</subtitle>

Cited by 35 publications

References 15 publications

The electrical conductivity of Posidonia black shales — from magnetotelluric exploration to rock samples

The electrical conductivity of Posidonia black shales — from magnetotelluric exploration to rock samples

Influence of Clay, Calcareous Microfossils, and Organic Matter on the Nature and Diagenetic Evolution of Pore Systems in Mudstones

Multiproxy geochemical characterization of Kommugudem Formation, Krishna Godavari Basin, India: Implication on hydrocarbon potential and shale brittleness

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