Hasil untuk "Petrology"

D. Green, A. .. Ringwood

G. Ranalli, D. Murphy

Chang-qing Liu, Zhao-biao Yang, He-qing Chen et al.

Abstract Since 2021, significant advances have been made in the exploitation of deep coalbed methane (CBM) in China, with peak gas production rates reaching over 100,000 m3/d from wells in the Ordos basin. Despite these successes, research on gas flow mechanisms and transient pressure behavior, particularly in the context of horizontal wells and intensive stimulation, has lagged behind field developments. In this study, a “dual-porosity and dual-phase” model, which incorporates free and adsorptive gas, coal quality and excess adsorption, has been proposed to better understand gas flow dynamics during extraction from deep coal seams with multi-fractured horizontal wells. Utilizing Laplace transformation and the Gaver-Stehfest numerical inversion method, combined with boundary elements and point-source functions, a semi-analytical solution is derived. This solution identifies six distinct flow regimes under constant-rate conditions: wellbore storage flow (I), early pseudo-radial flow (II), elliptical flow (III), transitional flow (IV), desorptive gas dominatedflow (V), late pseudo-radial flow (VI). A notable “desorptive concave” response in Regime V and the presence of free gas in Regime III, are distinctive features of deep coal gas reservoirs. A comprehensive sensitivity analysis is conducted to examine the impact of various parameters on pressure responses. Eventually, a field case study validates the model, emphasizing the significant contribution of desorbed gas in Regime V. These findings offer valuable insights into the gas flow mechanisms of deep coal reservoirs and provide guidance for optimizing multi-fractured horizontal well management strategies.

Degterev, Artem V., Chibisova, Marina V.

In 2024, 616 ash emissions were registered at Ebeko volcano (Paramushir Island, Northern Kurils) to heights from 1.5 to 4.5 km above sea level (181 of them reached a height of 3 km or more). The distribution of emission frequency and height during the year turned out to be unusual compared to the periods 2018–2021 and 2022–2023. The period from February to April was characterized by increased explosive activity: the total number of emissions and their maximum height significantly exceeded the values of the same months of the previous years. From May to September, on the contrary, the eruptive activity significantly decreased relative to the average values of 2018–2021 and 2022–2023 (previously, the peak activity occurred during the summer months, when more than 100 events per month could be registered). From October 2024, a further decrease in the height and frequency of emissions, as well as a decrease in the concentration of ash in eruptive clouds, has been recorded. The last vapor-gas emission with insignificant ash content occurred on January 16, 2025. The pause in the activity of the Ebeko volcano since mid-January 2025 still maintains the need for continuous monitoring, given its high activity in recent years and its proximity to the settlement.

A. El Maz, A. Vauchez, J.-M. Dautria

<p>The study of metapelitic sillimanite- and garnet-bearing granulite xenoliths brought to the surface by the basanite of the 650 ka Tafraoute maar shed new light on the lower crust of the Tabular Middle Atlas (Morocco). Two main types of granulites are distinguished: (1) layered quartzo-feldspathic and (2) unlayered restitic. Mineralogy, petrology, <span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span> estimates, and electron backscatter diffraction (EBSD) data support that these granulites underwent two successive tectono-metamorphic events before their entrapment in lava. During the first event, probably the Hercynian orogeny, the Tafraoute lower crust acquired its foliation and primary paragenesis, likely including kyanite; it yields <span class="inline-formula"><i>P</i></span> and <span class="inline-formula"><i>T</i></span> conditions of 1.1 <span class="inline-formula">±</span> 0.1 GPa and 850–880 °C. The second event corresponds to a reheating up to ultrahigh temperatures (1050 <span class="inline-formula">±</span> 50 °C) under slightly lower-pressure conditions (0.9 <span class="inline-formula">±</span> 0.1 GPa). This led first to the transformation of kyanite into large prismatic sillimanite. The latter displays uncommon evidence of the dislocation creep deformation of a moderate intensity that points to a tectonic episode occurring after their formation. After deformation has stopped, a reaction between sillimanite and garnet resulted in the crystallization of orthopyroxene and spinel-deformation-free coronas around garnets. Approaching the peak of temperature, anhydrous partial melting of quartzo-feldspathic layers likely occurred, and the resulting felsic melt spread into the rocks. This reheating event might be the consequence of the Late Permian to Mid Jurassic rifting that preceded the formation of the Middle Atlas range, possibly associated with underplating of hot gabbroic magma. This event was followed by gradual cooling down to <span class="inline-formula">∼</span> 800 °C, leading to static crystallization of the felsic melt in the quartzo-feldspathic granulites. The last event susceptible to have affected the lower crust is the alkali magmatism active in the Middle Atlas during the Mio-Plio-Quaternary. In this context, the origin of restitic granulites is questionable. It may result either from the thermal event associated with the pre-alpine rifting or from the emplacement of basaltic dikes in the lower crust before the Quaternary eruption of the Tafraoute volcano. During this eruption, the studied granulites were entrapped in the ascending lava and very quickly transferred up to the surface, triggering the formation of small vesicular glass pockets. This study highlights the contrasted post-Hercynian evolution of the lower crust in the northern coastal alpine orogen (Rif) and the Tabular Middle Atlas; the first one underwent a tectonic exhumation without reheating during the Alpine orogeny, while the second one is characterized by a reheating to ultrahigh temperature, probably during the pre-alpine rifting, but was probably not or only slightly affected by the alpine events.</p>

Wei He, Kai Hu, Jian Cao et al.

Amid growing global clean energy demand, coalbed methane (CBM) in the coal-rich Weizhou area holds great development value. This study explores Weizhou CBM's geochemical traits and genesis via analyzing gas compositions (Shanxi and Taiyuan Formations), stable isotopic distributions (δ13C1, δD, δ13CO2, and δ15N), and their burial depth variations. Results show that CBM is hydrocarbon-dominated: Shanxi and Taiyuan Formations have average methane contents of 89.89% and 88.24%, respectively. Coal metamorphism is medium-to-high (Ro: 1.76%–2.52%, subbituminous to anthracite). Isotopic averages were as follows: Shanxi versus Taiyuan (δ13C1: −36.91‰ vs. −36.68‰; δ13C2: −19.46‰ vs. −24.2‰; and δ13CO2: −17.56‰ vs. −15.29‰) and regional δD (−188.7‰) and δ15N (−1.27‰). Further, the results identify gas source differentiation between the Shanxi Formation and Taiyuan Formation, which is controlled by burial depth and coal metamorphism degree. A strong δ13C1–δ13C2 correlation (δ13C1=0.5044 δ13C2−26.188, R2=0.616) confirms the dominant status of thermogenic gas. δ13C1−C1/C2+C3 data fall in the secondary thermogenic zone, indicating modification by diffusion, migration, and fractionation. Gas source compositions differ between the upper Shanxi (0–4 seams) and the lower Taiyuan (5–20 seams) Formations. These findings support optimized Weizhou CBM exploration and utilization.

J. Clemens, C. Mawer

J. Eichelberger, C. Carrigan, H. Westrich et al.

A. V. Morozkin, A. V. Garshev, V. O. Yapaskurt et al.

Magnetic and magnetocaloric properties of polycrystalline Gd3Co4Ge13 (Cubic, Yb3Rh4Sn13-type, Space group Pm-3n, No. 223, cP40) have been studied by carrying out dc magnetization measurements in applied magnetic fields up to 140 kOe. The compound Gd3Co4Ge13 orders antiferromagnetically at 9 K (TN). The antiferromagnetism appears to be weak and with increasing applied magnetic fields, ferromagnetic interactions become dominant. This field-induced antiferromagnetic to ferromagnetic state that is marked as a change from inverse to normal magnetocaloric effect in the isothermal magnetic entropy change vs temperature plot around TN. At 2 K, the magnetization shows a tendency toward saturation in applied magnetic field and a magnetic moment of 5.3 µB per Gd3+ is obtained in 140 kOe field.

Marcin Stachowicz, Roman Gajda, Agnieszka Huć et al.

Abstract As a result of external compression applied to crystals, ions relax, in addition to shortening the bond lengths, by changing their shape and volume. Modern mineralogy is founded on spherical atoms, i.e., the close packing of spheres, ionic or atomic radii, and Pauling and Goldschmidt rules. More advanced, quantum crystallography has led to detailed quantitative studies of electron density in minerals. Here we innovatively apply it to high-pressure studies up to 4.2 GPa of the mineral hsianghualite. With external pressure, electron density redistributes inside ions and among them. For most ions, their volume decreases; however, for silicon volume increases. With growing pressure, we observed the higher contraction of cations in bonding directions, but a slighter expansion towards nonbonding directions. It is possible to trace the spatial redistribution of the electron density in ions even at the level of hundredths parts of an electron per cubic angstrom. This opens a new perspective to experimentally characterise mineral processes in the Earth’s mantle. The use of diamond anvil cells with quantum crystallography offers more than interatomic distances and elastic properties of minerals. Interactions, energetic features, a branch so far reserved only to the first principle DFT calculations at ultra-high-pressures, become available experimentally.

Ivan A. Panteleev, Vladimir I. Okunev, Victor A. Novikov

According to the stick-slip model, the relative movement of the fault planes is an act of unstable sliding, where movement begins when the stresses tangential to the fault plane reach a certain limit. The physical mechanism of dynamic slip along a fault consists of the sequential formation of conglomerates of loaded particles (force chains) in the contact zone and their subsequent destruction. These chains together form a force skeleton characterized by a specific spatial structure and strength properties. An increase in shear stress on the fault banks leads to local destruction of the strength skeleton; further evolution of the system brings destruction processes to higher spatial levels, ultimately leading to a shift in the fault banks. Since the evolution of the process of destruction of force chains in the contact zone of a fault along the hierarchy of scales from bottom to top is similar to the evolution of crack formation in a loaded medium from microscale to macroscale (specimen scale), the authors hypothesized the coherent behavior of acoustic noise accompanying the preparation of dynamic slip and recorded in different areas of fault zones. This work is devoted to testing this hypothesis on a laboratory scale, using an installation that simulates movement along a fault. As a result of the analysis, the hypothesis about the synchronization of the statistical properties of the acoustic emission during the preparation and implementation of the dynamic movement was confirmed. It is shown that the observation (detection) of the effect of the synchronization of the statistical properties of acoustic emission depends both on the set of parameters for which the spectral coherence measure is calculated and on the location of the recording of the initial data.

L. Meinert

Liu Yongliang, Ou Zhidong, Deng Hongda et al.

Abstract The breathing pipe of a produced water storage tank in a sulfide-containing natural gas station is prone to deposit formation, which leads to pipeline blockage. In this study, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses of the deposit in breathing pipe show that the deposit is composed of elemental sulfur and corrosion scales of ferrous polysulfide and ferrous sulfate. Existing deposit formation prediction models cannot predict the formation of elemental sulfur and corrosion scales in sulfide-containing environments. Herein, based on thermodynamic models of elemental sulfur and corrosion scale formation, deposit formation models of elemental sulfur, ferrous polysulfide, and ferrous sulfate scale formation are established. It is found that deposition of elemental sulfur and ferrous polysulfide increases with decreasing temperature of the breathing tube. Corrosion of pipe in the precipitating corrosive water leads to higher activity of $$\left[{\mathrm{Fe}}^{2+}\right]$$ Fe 2 + on the inner wall of the pipe carried by the sulfide-containing natural gas. Consequently, ferrous polysulfide and ferrous sulfate are easily deposited when the activity products of ferrous, sulfide, and sulfate ions are higher than the thermodynamic solubility product constant. The aforementioned prediction models are applied to predict the deposition of ferrous polysulfide, ferrous sulfate corrosion scale, and elemental sulfur using the chemical composition data of gas and precipitating water in the breathing pipe of the produced water tank of TB101-X1 well. The prediction results of the models are consistent with those of actual chemical composition analysis, which verifies the accuracy and reliability of the models.

Yong‐Fei Zheng, Qiong-Xia Xia, Ren‐Xu Chen et al.

M. Walter, S. Kohn, D. Araújo et al.

M. Streck

K. Cashman, R. Sparks

M. Kohn

Chusi Li, N. Arndt, Qingyan Tang et al.

J. Forshaw, D. Waters, D. Pattison et al.

Recently published activity–composition (a–x) relations for minerals in upper amphibolite‐ and granulite facies intermediate and basic rocks have expanded our ability to interpret the petrological evolution of these important components of the lower continental crust. If such petrological modelling is to be reliable, the abundances and compositions of phases calculated at the interpreted conditions of metamorphic equilibration should resemble those in the sample under study. Here, petrological modelling was applied to six granulite facies rocks that formed in different tectonic environments and reached different peak metamorphic pressure–temperature (P–T) conditions. While phase assemblages matching those observed in each sample can generally be calculated at P–T conditions that approximate those of peak metamorphism, a consistent discrepancy was found between the calculated and observed compositions of amphibole and clinopyroxene. In amphibole, Si, Ca and A‐site K are underestimated by the model, while Al and A‐site Na are overestimated; comparatively, in clinopyroxene, Mg and Si are generally underestimated, while Fe2+ and Al are typically overestimated, compared to observed values. One consequence is a reversal in the Fe–Mg distribution coefficient (KD) between amphibole and clinopyroxene compared to observations. Some of these mismatches are attributed to the incorrect partitioning of elements between the predicted amphibole and clinopyroxene compositions; however, other discrepancies are the result of the incorrect prediction of major substitution vectors in amphibole and clinopyroxene. These compositional irregularities affect mineral modal abundance estimates and in turn the position and size (in P–T space) of mineral assemblage fields, the effect becoming progressively more marked as the modal abundance of hornblende increases; hence, this study carries implications for estimating P–T conditions of high‐temperature metabasites using these new a–x relations.