Arabian Journal of Geosciences最新文献

The deep mining industry commonly encounters significant challenges, including large displacements of the roof in the gob-side entry retaining, and large deformations and failures of the filling body, which seriously compromise the structural safety and reliability of mines. In this study, we focus on a specific engineering case of the 8318 working face from the Xinzhou coal mine, employing the methodology of roof cutting for pressure relief and goaf filling with gangue reinforcement. Through a comprehensive approach involving numerical analysis, theoretical derivation, and experimental validation, the key parameters of the gob-side entry retaining by roof cutting, and the cooperative load-carrying mechanism of gangue reinforcement in gob-side entry retaining by cutting roof were systematically investigated. The numerical simulations and underground mine pressure monitoring data demonstrated that the optimum roof cutting height is 10 m at an optimum roof cutting angle of 8°. The proposed cooperative load-carrying technology of gob-side entry retaining by roof cutting significantly reduced the peak vertical stresses in the centre of the roof and the filling body by 22.6% and 43.4%, respectively. Furthermore, individual pillar stress levels showed notable reductions, with the maximum working stress and average stress decreasing by 34.2% and 47.8%, respectively. The practical implementation of our study offers valuable guidance in the control of surrounding rock in deep mining, thereby contributing significantly to the advancement in the field of surrounding rock support control.

Environmental protection requirements and the need to increase the proportion of oil recovered by secondary methods have led to the rise in popularity of microbial enhanced oil recovery (MEOR) techniques. Usually, MEOR requires the use of indigenous strains of microorganisms residing in wells, as they are adapted to local conditions. However, for some wells and fields, such as the Boca de Jaruco field in Cuba, information about the oilfield microorganisms and their properties is extremely limited. One of the properties crucial for the successful implementation of MEOR in fields is the ability of indigenous strains to produce biosurfactants. The aim of the present study is to evaluate the ability of six bacterial isolates obtained from the Boca de Jaruco field in Cuba to produce biosurfactants. The isolates capable of utilizing oil as their sole carbon source were identified as Bacillus subtilis (strains CC21, CC23, CC31, and CC32), Bacillus licheniformis (strain CC33), and Aeromonas veronii (strain CC22). It was determined that all isolates can tolerate temperatures between 30 and 60 °C, salinity ranging from 0.5 to 10.0% NaCl, and pH levels between 6 and 9. Regarding their ability to produce biosurfactants, assessed using the drop collapse method, oil-spreading method, emulsification activity test, and surface tension measurement, the isolates ranked as follows: A. veronii CC22 > B. subtilis CC21 = B. subtilis CC31 > B. subtilis CC23 = B. subtilis CC32 > B. licheniformis CC33. The biosurfactants produced were stable in the presence of 1.7 to 20.0% NaCl, irrespective of temperature (30 or 70 °C). However, substituting 20% of the NaCl with CaCl₂ resulted in destabilization of the biosurfactants produced by all investigated isolates, with destabilization levels averaging up to 32% at 70 °C.

The reservoir fluid PVT model is necessary to all types of hydrodynamic modelling (field development, well flow, well test, basin modelling, etc.). The PVT model, when not properly tuned, can result in significant inaccuracies in calculating PVT properties and field production of volatile oil and gas-condensate systems. The process of tuning the reservoir fluid PVT model is a complex and time-consuming task. Various methods, such as regression and machine learning (ML), have been employed for reservoir oil PVT model tuning; however, a definitive approach has not yet been identified. This paper introduces a novel and efficient step-by-step approach for developing and tuning reservoir fluid PVT which enables engineers to tune PVT models much faster than before. The new proposed approach can assist in the initialisation of a PVT model by employing effective methods for initial data pre-processing. Furthermore, it can accurately reproduce the results obtained from field measurements and basic laboratory studies conducted on representative samples, in a model using a cubic equation of state. Tuning the PVT model enables the reliable modelling of the PVT properties of all five types of reservoir fluids (black oil, volatile oil, gas condensate, wet gas, dry gas) in various applications; the applications include the design and monitoring of field development, multiphase flow calculations in wells and field pipelines, and basin modelling. It is possible to algorithmise and automate the application of this approach in specialised software. This study considered eight Russian reservoir oil and gas-condensate systems, for which the PVT models were tuned, using the proposed approach. The comparison between proposed approach and other tuning methods in modern PVT simulators (PVTi, PVTsim, Multiflash, PVT Designer) is shown in the article. These examples show the effectiveness of the proposed approach.

The Koldam site is located in the Himachal Lesser Himalaya in the vicinity of the main boundary thrust. The area near Koldam is seismically active, with earthquakes ranging in size from mild to major. Earthquakes result in the death and destruction of people and property. It is vital to research the features and nature of earthquake sources. This paper examines an analysis of 45 local earthquakes that were observed in the Himachal Himalaya region during the period from June 2014 to May 2019. The seismic moment, source radius, and stress drop are among the source parameters that are computed for earthquakes. These source parameters are computed using the hypocenter parameters, corner frequency (({f}_{text{c}})), and low-frequency spectral level (({Omega }_{text{o}})) with the help of Seisan software following Brune’s source model which describes the displacement amplitude spectrum as the physical process that releases energy at the source. This study is used to monitor and interpret the characteristics of the regional seismicity. The seismic moment ranges between 7.94 × ({10}^{10}) and 1.25 × ({10}^{15}) N-m with magnitudes between 1.6 and 4. The source radius is found to vary from 122.3 to 427.2 m. The stress drops of most of the events vary from 0.45 to 74.92 bar except for two events which have stress drops of 130.56 bar and 175.06 bar, respectively. Stress drops of 19 events range from 0.45 to 10.83 bar with M_o between 1 × 10¹² and 8 × 10¹² N-m, stress drops of 18 events range from 2.5 to 39.41 bar with M_o between 1 × 10¹³ and 8 × 10¹³ N-m, and stress drops of 6 events range from 18.08 to 74.92 bar with M_o between 1 × 10¹⁴ and 4 × 10¹⁴ N-m, respectively. Stress drops exhibit an increasing tendency up to a focal depth of 20 km, beyond which they show a decreasing pattern that appears to be associated with the strength of the crust. It appears that below 20 km, the strength of the upper crust decreases based on the variation of the maximum stress drop with focal depth. A scaling relationship has been established between the source parameters and the magnitudes for the region. A scaling law ({M}_{text{o}}) = 3.85 × ({10}^{15}{f}_{text{c}}^{-3.068}) has been developed between the seismic moment and corner frequency, for the region. This law almost agrees with that of the Kameng region (({M}_{text{o}}) = 2.0 × ({10}^{15}{f}_{text{c}}^{-3.34})) of the Arunachal Lesser Himalaya, the Bilaspur region (({M}_{text{o}}) = 2.0 × ({10}^{15}{f}_{text{c}}^{-3.03})) of the Himachal Lesser Himalaya, and the Garhwal Himalaya (({M}_{text{o}}) = 3.0 × ({10}^{16}{f}_{text{c}}^{-3.0})).

The Badabagh Member sandstone is mainly quartz arenite, and its composition ranges from sub-arkose to sub-lithic arenite. Petrographic analysis, scanning electron microscopy (SEM), X-ray diffractometer (XRD), and quantitative measurements of reservoir properties were utilized to thoroughly examine the physical and diagenetic characteristics of the Badabagh Member sandstone. Mechanical compaction; the precipitation of calcareous, ferruginous, and silica cement; the creation of clay minerals; the breakdown and alteration of unstable clastic grains like feldspar and rock fragments; and grain fracturing are among the identified diagenetic properties. Primary porosity was greatly decreased by mechanical compaction and using authigenic cement, such as ferruginous, calcareous, and silica. Clastic grains and cement dissolved, resulting in secondary porosity. Porosity was estimated to have been 40% at first, then compaction decreased it to approximately 9.76%, and cementation further reduced it to 28.03%. Compared to compaction, cementation had a relatively greater effect on the reduction of porosity in the Badabagh Member sandstone. On the other hand, some primary porosity was preserved due to sporadic patches of calcareous cement and imperfect filling. Physical compaction, cementation, and grain ductility were primary contributors to reduced porosity and permeability, whereas clay coatings like kaolinite booklet-type coating, pore-lining chlorite coating around grains, and feldspar dissolution were instrumental in preserving reservoir quality by creating secondary porosity. The sandstone under study exhibits diagenetic processes that are intimately related to its reservoir potential.

The northeastern region of Oman presents exceptional outcrops of carbonatite and ultramafic lamprophyre along the east coast, and they intruded a sequence of marine sedimentary rocks. This study aims to study these outcrops through geological and geophysical methods to assess their dimensions and orientations beneath the recent coastal sediments. Geologically, the area is characterized by sedimentary rocks belongings to the Batain nappes. The Batain Group consists of various formations rich in alkaline volcanic rocks, including the Wahra Formation, which hosts the studied outcrops. Fieldwork revealed folded cherts and shales with fault zones and breccias containing ultramafic lamprophyre and carbonatite. Geophysical surveys utilizing radiomagnetotelluric (RMT) soundings identified the lateral extension of these rock sequences beneath sedimentary cover. Inversion of RMT data provided insights into the resistivity distribution, delineating the ultramafic lamprophyre and carbonatite body beneath the sediments. Structural analysis suggests that these rocks were involved in transpressive deformation during late Neogene tectonic events. Despite challenges posed by conductive beach sediments, the RMT method proved effective in shaping these subsurface features, contributing to understanding the geological complexities of the region.

Infiltration, signifying the downward movement of water, consistently shapes various surface runoff features, influencing both their magnitude and distribution. Traditionally, assessing soil infiltration in the field has been a time-consuming and challenging task. However, the use of assorted infiltration models has significantly streamlined this process. This study focused on measuring soil infiltration in clay soil using a double-ring infiltrometer. The Horton infiltration model emerged as a prominent choice for analyzing the infiltration characteristics of clay soil. Cumulative infiltration depths were employed to determine model parameters and evaluate its performance. A comparison between measured infiltration rates and model-estimated rates was conducted. Statistical parameters, such as the coefficient of determination (R²), indicated a strong mean value of 0.842, approaching unity. Both the root mean squared error (RMSE) and absolute mean difference (AMD) demonstrated robust agreement between field-measured infiltration depths and model-estimated infiltration depths. The results of this investigation suggest that the Horton infiltration model serves as a suitable tool for estimating soil infiltration characteristics in the Kokamthan village within the Godavari basin, part of the Kopargaon region.

Regional climate studies are essential for pinpointing climate hotspots and developing effective resilience strategies. This study examined trends in eight precipitation and ten temperature extremes in Odisha, India, using RClimDex in R studio with data from the India Meteorological Department, Pune, covering 1980 to 2010 for Khordha, Keonjhar, and Sambalpur. Statistical significance was tested through linear regression and Mann-Kendall tests. Results show a significant shift in climate, particularly in Sambalpur and Khordha, where nine and seven out of ten temperature indices, respectively, exhibited significant changes. The mean maximum temperature increased significantly in Khordha (0.03 °C/year) and Sambalpur (0.026 °C/year), while the mean minimum temperature rose significantly in Khordha (0.03 °C/year) but decreased in Keonjhar (-0.029 °C/year) and Sambalpur (-0.061 °C/year). Cool nights significantly decreased in Khordha (-0.229 days/year) and increased in Sambalpur (0.557 days/year). Warm nights rose significantly in Khordha (0.484 days/year) but declined in Sambalpur (-0.421 days/year). The warm spell duration indicator showed significant increases across all regions, with increments of 0.308, 0.438, and 0.689 days/year in Khordha, Keonjhar, and Sambalpur, respectively. Warm days also rose significantly in Khordha (0.301 days/year) and Sambalpur (0.379 days/year). Regarding precipitation, Khordha showed positive trends in all eight indices, with a significant change in heavy rainfall days. In Keonjhar, no significant changes were observed, while Sambalpur experienced a significant decrease in total annual rainfall (-9.621 mm/year). These findings highlight a significant shift in climate patterns within Odisha, with Sambalpur and Khordha more vulnerable to extreme events compared to Keonjhar.

This research investigates the seismic soil-pile-structure interaction (SSPSI) effects on a tall building supported by a pile-mat foundation in Dhaka soil using nonlinear time-history analysis. A comparison between fixed base and flexible base models is conducted to analyze key design parameters including lateral displacements, inter-story drifts, foundation rotation, natural frequencies, and response spectra. The study focuses on a specific soil profile (Soil profile-1) in Dhaka, comprising cohesive and non-cohesive soil layers. A 42-story structure with four basements, situated on Dhaka soil, is modeled using finite element analysis with Midas GTS NX software. Results reveal that the settlement of the mat foundation exceeds permissible limits for tall buildings supported by a cohesive layer of Dhaka soil, advocating for the practicality and cost-effectiveness of a mat on piling foundation in such scenarios. Dynamic soil-structure interaction analysis demonstrates that although the flexible base model exhibits larger lateral displacement and inter-story drift compared to the fixed base model, these values remain within acceptable limits. Nominal foundation rotation is observed in the mat on pile foundation for Dhaka soil. The study concludes that employing a pile-mat foundation while neglecting soft soil does not significantly alter the analysis for tall buildings with multiple basements in Dhaka, validating the importance of considering SSPSI effects in structural design and analysis.

The present study explores the influence of silt content on the undrained monotonic behavior of compacted tuff. All undrained triaxial tests were performed at both relative densities D_r = 50 and 90% and compacted with the optimum water content on tuff soil mixed with silt in the range of 0 to 50%. Experimental results show that adding fines content (FC) up to 20% increases the resistance of dense compacted tuff (D_r = 90%) by about 35% for 100 kPa of confining pressure, and the addition of 10% silt fines results in a maximum increase of 15.71% in the medium dense state specimen (D_r = 50%). The deviator stress reveals a decrease by adding more than 20% of silt. Moreover, the soil cohesion was found to attain maximum values with the optimum silt percentage of FC = 10% for medium-density samples (D_r = 50%) and FC = 20% for dense samples (D_r = 90%), respectively. Finally, the study showed a direct correlation between the cohesion of the soil prepared in a dense state (D_r = 90%) and the soil’s maximum dry density (MDD). In particular, the maximum dry density corresponds to a higher cohesion.