GAS HAZARD ASSESSMENT IN THE RUDNA MINE, BASED ON ANALYSIS OF POROSITY OF DOLOMITES FROM THE RESERVOIR FORMATION

Reservoir dolomites saturated with gas under high pressure were found in the ceiling of excavations in a Rudna copper mine in southwestern Poland. Reservoir dolomites are a major concern in the mining industry and the focus of substantial research. High-porosity dolomites are definitively considered "hazardous", but the gas is extracted from the dolomites with low porosity, too. So, it is necessary to know way of gas occurrence in the pore space. This article aims to describe the reservoir potential of the dolomites through pore space characterisation and determine whether the gas can migrate into the excavations. A comprehensive analysis of the distribution of pore size and nature using microscopic observations, X-ray microtomography and mercury porosimetry. The results distinguished three types of dolomites with different porosities: dolomites with high effective porosity, dolomites with reduced effective porosity, and sealed dolomites. Particular attention should be paid to sealed dolomites. Their effective porosity results from mercury porosimetry are very low. However, they also contained 4% closed porosity described from microscopic observations, where gas is accumulated, too. Presence of gas in the closed pores dolomites is a common phenomenon. However, the presence of high-pressure gas traps within locally more porous, microcraced and permeable dolomites is a major threat.

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A physical model for porosity reduction in sandstones

Geophysics ◽

10.1190/1.1444346 ◽

1998 ◽

Vol 63 (2) ◽

pp. 454-459 ◽

Cited By ~ 41

Author(s):

Doron Gal ◽

Jack Dvorkin ◽

Amos Nur

Keyword(s):

Elastic Moduli ◽

Pore Space ◽

Total Porosity ◽

Effective Porosity ◽

High Porosity ◽

Formation Factor ◽

Archie’S Law ◽

Unconsolidated Sands ◽

Porosity Reduction ◽

Reduction Mechanisms

The experimental elastic moduli‐porosity trends for clean sandstones can be described by the modified upper Hashin‐Shtrikman (MUHS) bound. One geometrical (but not necessarily geological) realization is: as porosity decreases, the number of the pores stays the same and each pore shrinks while maintaining its shape. This concept of uniform porosity reduction implies that permeability is proportional to the effective porosity squared, and that formation factor is proportional to the inverse of the effective porosity. The effective porosity here refers to the part of the pore‐space that dominates fluid flow. The proposed relations for permeability and formation factor agree well with the experimentally observed values. These laws are different from the often used forms of the Kozeny‐Carman equation and Archie’s law, where permeability is proportional to the total porosity cubed and formation factor is proportional to the inverse of the total porosity squared, respectively. We suggest that the uniform porosity reduction concept be used in consolidated rocks with porosities below 0.3. The transition from high‐porosity unconsolidated sands to consolidated sandstones can be described by the cementation theory: the MUHS moduli‐porosity curves connect with those predicted by the cementation theory at the porosity of about 0.3. This scheme is not appropriate for modeling other porosity reduction mechanisms such as glass bead sintering because, during sintering, the pores do not maintain their shapes, rather they gradually evolve to rounder, stiffer pores.

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Crystals Springing Into Action: Metal-Organic Framework CUK-1 as a Pressure-Driven Molecular Spring

Chemical Science ◽

10.1039/d1sc00205h ◽

2021 ◽

Author(s):

Paul Iacomi ◽

Ji Sun Lee ◽

Louis Vanduyfhuys ◽

Kyung-Ho Cho ◽

Pierre Fertey ◽

...

Keyword(s):

High Pressure ◽

Single Crystal ◽

Metal Organic Framework ◽

Mercury Porosimetry ◽

Crystalline Material ◽

X Ray Diffraction ◽

Mechanical Pressure ◽

X Ray ◽

Metal Organic

Mercury porosimetry and in situ high pressure single crystal X-ray diffraction revealed the wine-rack CUK-1 MOF as a unique crystalline material capable of a fully reversible mechanical pressure-triggered structural contraction....

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Observing the evolution of geometry and flow in dissolving rocks

10.5194/egusphere-egu2020-1010 ◽

2020 ◽

Author(s):

Max Cooper ◽

Silvana Magni ◽

Phung Vu ◽

Tomasz Blach ◽

Andrzej Radlinski ◽

...

Keyword(s):

Flow Field ◽

Field Experiments ◽

Numerical Models ◽

Pore Space ◽

Mineral Dissolution ◽

High Porosity ◽

X Rays ◽

Light Water ◽

X Ray ◽

Virtual Channels

Dissolution of porous media is a complex process involving nonlinear couplings between flow, transport, the evolving geometry of the media, and the process of dissolution itself. In some cases these couplings lead to the formation of intricate patterns, the characteristics of which depend strongly on flow, mineral dissolution rate, and initial pore space geometry. In particular, finger-like channels, termed "wormholes", are spontaneously formed where the majority of flow is focused. Capturing the dynamics of wormhole growth has so far been largely limited to numerical models, with few studies observing their time evolution in real rocks. In this study we capture the dynamics of both wormhole growth and their alteration of flow in the rock by placing the experiment within neutron and X-Ray tomographs and scanning while actively dissolving limestone cores.&#160;To observe the evolution of wormhole geometry limestone samples are dissolved in a cell translucent to X-Rays and neutrons. For each experiment a high (30-35 micrometer) resolution scan was taken of the initial sample geometry, as well as the geometry after dissolution. During acidization tomography was performed at 60-70 micrometer resolution with acquisition times ranging from three to six minutes. For several experiments dissolution was paused and and a contrasting agent injected to visualize the flow field within the sample. Flow field experiments were performed with neutron tomography by first injecting heavy water, followed by light water as the contrast agent, and with X-Ray tomography by injection a solution of potassium iodide into light water. Results of dissolution experiments show that wormhole growth can be tracked at sufficiently high spatial and temporal resolution to measure changes to the pore space.These experiments highlight the importance of the near-tip region on the dynamics of wormhole propagation. In particular, focusing of the flow is shown to take place not only within the wormhole but also significantly (>5mm) into the porous region past the wormhole tip. These "virtual channels" link the tip with the neighboring regions of high porosity. Several such virtual channels can exist, indicating potential paths of further growth, and demonstrate the strong coupling of flow and geometry evolution. Additionally, we observe a dramatic dependence of the dissolution patterns on the initial pore structure, in particular the total initial porosity, distribution of pore sizes and connectivity of the pore space. In pore spaces with poor connectivity and low porosity the wormholes tend to be very tortuous and thin. Such wormholes advance through rapid, almost discontinuous jumps, guided by the above-described pre-focusing mechanism. On the other hand, the advancement of a wormhole in a well-connected rock is much more diffuse, controlled by merging between neighboring pore spaces.

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Charakterystyka utworów czerwonego spągowca w aspekcie badań rentgenowskiej mikrotomografii komputerowej i mikroskopii optycznej

Nafta-Gaz ◽

10.18668/ng.2020.11.01 ◽

2020 ◽

Vol 76 (11) ◽

pp. 765-773

Author(s):

Marek Dohnalik ◽

◽

Konrad Ziemianin ◽

Keyword(s):

Pore Space ◽

Mercury Porosimetry ◽

Mineralogical Composition ◽

Effective Porosity ◽

Hydrocarbon Exploration ◽

Core Material ◽

Reservoir Properties ◽

Average Value ◽

Full Characterization ◽

Single Well

The article presents the results of microtomographic and petrographic investigations of Rotliegend sandstones collected from core material from wells located in the area of the Fore-Sudetic Monocline in its central and northern parts and also on the border of the Fore-Sudetic Monocline and the Mogilno - Łódź Synclinorium. Three areas were selected for the study: Czarna Wieś–Parzęczewo (19 samples), Środa Wielkopolska–Kromolice (21 samples) and Siekierki–Miłosław (21 samples). The aim of the petrologic and microtomographic studies was to investigate how the different reservoir properties of sandstones will be reflected in the results of the methods used. Strong differences between samples from the region of Środa Wielkopolska–Kromolice and the other studied areas have been demonstrated. In the case of this area several key factors were noticed: the highest average value of effective porosity; the highest average content of pores belonging to class VII (pore volume subsystem classification); three times higher average value of the CT porosity coefficient and the largest length of the average chord. Also in terms of petrography (composition of grains, cement type) it is a region where major differences, especially compared to the region of Czarna Wieś–Parzęczewo, can be seen. Based on the obtained results, it was possible to rank the examined regions in terms of their reservoir properties – from the worst (Czarna Wieś–Parzęczewo) to the best (Środa Wielkopolska–Kromolice). These conclusions are also confirmed by other petrophysical analyses (eg. mercury porosimetry, permeability analysis). Combination of the obtained microtomographic and petrographic results allowed to obtain a full characterization of the investigated samples – both in terms of the mineralogical composition of grains, as well as the development of the pore space. These data, especially in combination with the results of density and porosity analyses (helium pycnometry and mercury porosimetry), open up a number of possibilities to carry out different types of modeling (porosity, permeability) both on the scale of the sample itself, as well as the scale of a single well or even the whole basin, which is crucial for creating a hydrocarbon exploration strategy.

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Geometrical and Topological Analysis of Pore Space in Sandstones Based on X-ray Computed Tomography

Energies ◽

10.3390/en13153774 ◽

2020 ◽

Vol 13 (15) ◽

pp. 3774 ◽

Cited By ~ 1

Author(s):

Linxian Gong ◽

Lei Nie ◽

Yan Xu

Keyword(s):

Computed Tomography ◽

Fluid Flow ◽

Pore Space ◽

Topological Analysis ◽

Network Models ◽

High Porosity ◽

Micro Computed Tomography ◽

X Ray ◽

And Topology ◽

Low Porosity

The pore geometry and topology properties of pore space in rocks are significant for a better understanding of the complex hydrologic and elastic properties. However, geometry and topology information about the sandstone pore structures is not fully available. In this study, we obtained the topological and geometrical pore parameters from a representative elementary volume (REV) for fluid flow in sandstone samples. For comparison, eight types of sandstones with various porosities were studied based on the X-ray micro-computed tomography technique. In this study, the REV size was selected based on the parameters from the respective pore network models (PNM), not just the porosity. Our analysis indicates that despite different porosity, all the sandstone samples have highly triangular-shaped pores and a high degree of pore structural isotropy. The high porosity group sandstones exhibit wider ranges of pore sizes than the low porosity group sandstones. Compared to the high porosity group sandstones, the low porosity group sandstones samples showing a higher global aspect ratio, indicating some pores exist in the form of bottlenecks. The pore topological properties of different sandstones show a high dependence of the porosity. The high porosity group sandstones obtain large coordination numbers, large connectivity densities and low tortuosities. The results from this study will help better understand the complex pore structure and the fluid flow in sandstone.

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Nano-probe x-ray analysis and high-resolution imaging on planar defects in high-pressure synthesized infinite-layer superconductor

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100171377 ◽

1994 ◽

Vol 52 ◽

pp. 728-729

Author(s):

Y. Y. Wang ◽

H. Zhang ◽

V. P. Dravid ◽

H. Zhang ◽

L. D. Marks ◽

...

Keyword(s):

High Pressure ◽

High Resolution ◽

Atomic Structure ◽

Emission Spectra ◽

High Resolution Electron Microscopy ◽

Planar Defects ◽

X Ray ◽

Infinite Layer ◽

Resolution Electron ◽

Resolution Imaging

Azuma et al. observed planar defects in a high pressure synthesized infinitelayer compound (i.e. ACuO2 (A=cation)), which exhibits superconductivity at ~110 K. It was proposed that the defects are cation deficient and that the superconductivity in this material is related to the planar defects. In this report, we present quantitative analysis of the planar defects utilizing nanometer probe xray microanalysis, high resolution electron microscopy, and image simulation to determine the chemical composition and atomic structure of the planar defects. We propose an atomic structure model for the planar defects.Infinite-layer samples with the nominal chemical formula, (Sr1-xCax)yCuO2 (x=0.3; y=0.9,1.0,1.1), were prepared using solid state synthesized low pressure forms of (Sr1-xCax)CuO2 with additions of CuO or (Sr1-xCax)2CuO3, followed by a high pressure treatment.Quantitative x-ray microanalysis, with a 1 nm probe, was performed using a cold field emission gun TEM (Hitachi HF-2000) equipped with an Oxford Pentafet thin-window x-ray detector. The probe was positioned on the planar defects, which has a 0.74 nm width, and x-ray emission spectra from the defects were compared with those obtained from vicinity regions.

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Effect of high pressure-temperature on silicon layered structures as determined by X-ray diffraction and electron microscopy

The European Physical Journal Applied Physics ◽

10.1051/epjap:2004119-10 ◽

2004 ◽

Vol 27 (1-3) ◽

pp. 415-418

Author(s):

J. Bak-Misiuk ◽

A. Misiuk ◽

J. Ratajczak ◽

A. Shalimov ◽

I. Antonova ◽

...

Keyword(s):

Electron Microscopy ◽

High Pressure ◽

Layered Structures ◽

X Ray Diffraction ◽

X Ray

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Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

10.26434/chemrxiv.11345063.v2 ◽

2020 ◽

Author(s):

Keishiro Yamashita ◽

Kazuki Komatsu ◽

Hiroyuki Kagi

Keyword(s):

Crystal Structure ◽

High Pressure ◽

Crystal Growth ◽

Single Crystal ◽

Room Temperature ◽

Growth Technique ◽

Salt Hydrate ◽

X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl2·7H2O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

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Revisiting the High-Pressure Properties of the Metal-Organic Frameworks ZIF-8 and ZIF-67

10.26434/chemrxiv.13146278.v1 ◽

2020 ◽

Author(s):

Pia Vervoorts ◽

Stefan Burger ◽

Karina Hemmer ◽

Gregor Kieslich

Keyword(s):

High Pressure ◽

State Of The Art ◽

Energy Landscape ◽

Structural Flexibility ◽

Zeolitic Imidazolate Frameworks ◽

Stimuli Responsive ◽

X Ray Diffraction ◽

X Ray ◽

Open Questions ◽

Metal Organic

The zeolitic imidazolate frameworks ZIF-8 and ZIF-67 harbour a series of fascinating stimuli responsive properties. Looking at their responsitivity to hydrostatic pressure as stimulus, open questions exist regarding the isotropic compression with non-penetrating pressure transmitting media. By applying a state-of-the-art high-pressure powder X-ray diffraction setup, we revisit the high-pressure behaviour of ZIF-8 and ZIF-67 up to p = 0.4 GPa in small pressure increments. We observe a drastic, reversible change of high-pressure powder X-ray diffraction data at p = 0.3 GPa, discovering large volume structural flexibility in ZIF-8 and ZIF-67. Our results imply a shallow underlying energy landscape in ZIF-8 and ZIF-67, an observation that might point at rich polymorphism of ZIF-8 and ZIF-67, similar to ZIF-4(Zn).

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