Petrology Of Rocks Research Articles

Automatic recognition of debris rock lithology based on unsupervised semantic segmentation

Automatic recognition of debris rock lithology based on unsupervised semantic segmentation

Remote sensing analysis and geodynamic setting of magmatic spessartine-almandine-bearing leucogranites, Um Addebaa area, southeastern Desert, Egypt: Bulk rock and mineral chemistry

This study aims to incorporate optical multispectral remote sensing, petrography, geochemical, and field investigations in producing mapping and surface abundance of garnet mineralization within Um Addebaa area, southeastern Desert of Egypt. Datasets of Landsat-8 OLI/TIRS, ASTER and Sentinel-2A (S2A) were handled and scaled enhanced to discriminate the units of lithologic rock and garnet mineralization. The spectral mapping techniques of constrained energy minimization (CEM) and matched filtering (MF) are used to detect the garnet-rich zones which confined to the leucogranites masses. These granites are spessartine-almandine-rich, certainly along the interaction with the ophiolitic mélange. Notably, they have high total alkalis, SiO2, and Al2O3, Rb, 104Ga/Al, Y, Zr, Pb, Rb/Sr, Al2O3/TiO2, and FeO/MgO, and strong Ti, Sr, and Ba depletion as well as low CaO/Na2O ratio (<0.3). These geochemical parameters reflecting calc-alkaline, and strongly peraluminous magma of S-type. They are derived by two episodes of partial melting clay-rich metapelite crustal rocks followed by extreme Fe-Ti oxides and feldspar fractionation. These leucogranites formed within extension tectonic regime during post-collisional episode, resulting raising of asthenosphere and partial melting of the crustal metasedimentary rocks. Garnet occurs as, aggregates and/or vein like-shape, subhedral to rounded grains, homogenous and rarely reveal weak zonation. It’s cracked and free of inclusions. It contains appreciated concentrations of FeO and MnO and minor amounts of CaO and MgO, dominantly spessartine-almandine end-member (Alm52-59Sps 31-36 Grs 8-12 Prp0.5-0.8 Adr0). Garnet chemical composition reflect it is magmatic origin with MnO- FeO-rich magma that is produced from in situ nucleation from strongly peraluminous magmas during post- collision setting.

Experimental study on mechanical response and crack evolution law of coal and sandstone under different stress environments.

In order to study the mechanical response and crack evolution law of different lithologic rock bodies under different stress environments in deep stress mines, based on the deviator stress theory, the actual triaxial disturbance unloading rock test system was used to simulate the stress occurrence environment of the original rock. The mechanical characteristics of different σ2 coal rock masses were studied, and the crack evolution law of coal and sandstone under different stress environments was analyzed. The results show that the increase of σ2 inhibits the deformation in the σ2 direction of coal and sandstone, promotes the expansion and deformation in the σ3 direction, and enhances its peak strength and elastic modulus. The development characteristics of internal cracks in rock mass are directly related to the stress environment, and the increase of σ2 promotes the increase of the proportion of coal RA value, weakens the proportion of sandstone RA value, aggravates the development of coal internal shear cracks, and inhibits the development of internal shear cracks in sandstone. The larger σ2, the greater the initial AE ringing count of coal and sandstone, and the greater the AE cumulative energy when the rock mass is finally damaged. At the same time, due to the self-organizing behavior in the process of crystal failure in sandstone, the cumulative energy curve of sandstone fluctuates in a step-like manner. The ringing count and cumulative energy increase suddenly, which can predict the imminent instability and failure of the rock, and the research results can provide an experimental basis for the sudden instability of deep high-stress roadways.

Failure mechanism and control technology of soft-rock roadways subjected to high structural stress

The prevention and control of deformation and instability in high-stress soft rock roadways hold significant value for ensuring normal mine production and the safety of personnel and equipment. This study focuses on the pedestrian descent from the 11th mining area of the Yindonggou Mine, providing a thorough elucidation of the internal mechanisms leading to large deformation and instability in the roadway. It accounts for the influences of surrounding rock lithology, geological structure, and support measures. Consequently, based on the theory of rock instability, corresponding tunnel repair measures and control strategies were proposed and verified through field application. The results indicate that: (1) High strength dispersion and insufficient support resistance of the expansive weak and fractured surrounding rock sections are critical factors inducing significant deformation in the soft rock roadway of Yindonggou Mine. (2) The primary factor contributing to the large deformation disaster in the Yindonggou Mine roadway is the disturbance caused by proximate coal seam mining, which exacerbates the conflict between the high structural stress in the strata and the low strength of the surrounding rock. High-level stress initially leads to deformation in the weakly supported floor, followed by deformation and instability of the surrounding rock, ultimately culminating in the collapse of the entire roadway section. (3) Soft rock support should be designed with varying schemes tailored to the rock type and structural stress of the surrounding rock in the tunnel. For tunnels with carbon mudstone and expansive soft rock as the main roof and floor components, the support plan should primarily focus on enhancing the support stiffness of the tunnel wall. Conversely, for tunnels where sandstone predominates as the roof and floor material, the support plan should aim to restore the three-dimensional stress state of the surrounding rock and fully utilize its self-supporting capacity. (4) Based on the engineering conditions of pedestrian downhill in No.11 mining area of Yindonggou Mine, a differentiated support scheme is proposed. The feasibility and effectiveness of each support scheme are verified by numerical simulation, so as to provide valuable reference and enlightenment for similar projects.

Paleontological studies of the Devonian-Carboniferous boundary beds of Berchogur (Western Kazakhstan): possibilities of global correlation

Research subject. Devonian-Carboniferous boundary beds in the Berchogur Depression (Western Kazakhstan). New data on the fauna of ammonoids, conodonts, and foraminifers from the Berchogur sections were obtained during fieldwork studies in 2018–2019. Aim. Identification of episodes of the Global Hangenberg event (crisis) in the Berchogur section and correlation of the potential markers of the base of the Carboniferous in this section. Materials and Methods. The research was conducted using paleontological and lithological methods. Results. The study of fossil assemblages and rock lithology exposed by new excavations suggests that the markers of the Hangenberg event are present in the section; moreover, they can be correlated with the phases of this event in the sections of Western Europe. A correlation of ammonoid, conodont, and foraminiferal zones is proposed. It is shown that the conodont S. (Eo.) praesulcata in the Berchogur section first appears in Member 2b, and the first appearance of S. (Eo.) sulcata is recorded in Member 3b. Based on the findings of ammonoids of the genus Acutimitoceras, Members 3b and 3c can be correlated with the upper part of the prorsum ammonoid Zone, which corresponds to the level of appearance of S. (Eo.) sulcata. The intervals corresponding to episodes of the global Hangenberg event (pre-crisis, crisis, and partly post-crisis) are provisionally identified in the section. Conclusions. The pre-crisis interval corresponds to the abundance of foraminifers in the Q. kobeitusana substricta Zone and the Upper expansa and lower part of the Lower praesulcata conodont zones. The so-called crisis prelude corresponds to the extinction of the quasiendothyrid foraminiferal community and the upper part of the Lower praesulcata Zone (Member 2a2). The Hangenberg Extinction, or the lower crisis interval, corresponds to the clays of Member 2b in, and to the interval of most of the Middle praesulcata Zone – the lower part of the Upper praesulcata Zone, and to the Hangenberg black shales in Europe. The subsequent regressive episode (Member 3a) corresponds to the upper part of the Upper praesulcata Zone. The members with ammonoids (3c) and conodonts of the sulcata Zone (3b and 3c) and Member 4 correspond to the transgressive phase and are considered equivalent to the Stoсkum Limestone of the Rhenish Massif.

Brittle Regime Slip Partitioned Damage and Deformation Mechanisms Along the Eastern Denali Fault Zone in Southwestern Yukon

AbstractRare bedrock exposures of the eastern Denali fault zone in southwestern Yukon allow for the measurement, sampling, and analyses of brittle regime fault slip data and deformation mechanisms to explore relations to far field, oblique plate motions. Host rock lithologies and associated slip surfaces show episodic damage zone‐related deformation and calcite ± hematite ± chlorite related hydrothermal fluid flow. This regional scale network of asymmetric fault damage is spatially and kinematically linked to a discrete and narrow fault core. Fault network observations, orientations, slip data, and strain inversions document a slip partitioned strike‐slip fault system with locally and mutually overprinting strike‐, oblique‐, and dip‐slip components. Microstructural analyses reveal crystal plastic and co‐seismic brittle deformation mechanisms active in a narrow range of upper crustal temperature, pressure, fluid, and chemical conditions. The net damage related slip is not exclusively formed by a single kinematic system, but rather a fully partitioned, time integrated system likely operative for much of the fault's brittle regime evolution temporally constrained by previously published thermochronometric data. Although the fault slip data was collected from outcrop‐scale exposures at sites tens of kilometers apart, results show remarkable correlation between fault kinematics and plate motions along the ∼580 km long eastern Denali fault segment. End member, subhorizontal, northeast directed reverse and north directed dextral strike slip fault strain axes closely reflect relative plate motion interactions over at least the last 30 m.y. and act as a proxy for far‐field stresses compatible with the kinematics of the damage zone network.

LA-ICP-MS U–Pb dating and trace element analyses of detrital rutile from the Elbtal Group (Saxony, Germany): provenance constraints of the Saxonian Cretaceous Basin

AbstractThe steep sandstone cliffs of the Upper Cretaceous Elbtal Group exposed in the Eastern Erzgebirge and the Zittau Sandstone Mountains are impressive remnants of the Saxo-Bohemian Cretaceous Basin. Despite the excellent exposure, little is known about the provenance. Herein, we present LA-ICP-MS U–Pb and trace element data of detrital rutile grains separated from five different formations of the Elbtal Group to characterise and differentiate potential source regions. The Cenomanian samples of the Eastern Erzgebirge (Niederschöna and Oberhäslich formations, lower Elbtal Group) yield an U–Pb rutile age cluster at 320–330 Ma. The source rock lithology is predominantly of metapelitic origin. The Zr-in-rutile temperatures indicate amphibolite- to lower granulite-facies metamorphic conditions. Thus, the Variscan basement exposed in the Erzgebirge is assumed as proto source. The Middle Turonian to Early Coniacian samples from the Zittau Sandstone Mountains (Oybin, Lückendorf and Waltersdorf formations; upper Elbtal Group) yield similar U–Pb rutile ages with a cluster at 320–330 Ma. The source rock lithology is likewise predominantly classified as metapelitic and the Zr-in-rutile temperatures cluster in upper amphibolite- to granulite-facies metamorphic conditions. Exposures with high-grade metamorphic Variscan basement are assumed as likely proto sources for these sedimentary rocks. Sedimentary structures indicate a northerly source and thus contrast with direct input from the Variscan basement located to the south and east. Thus, the most likely sedimentary model is reworking of sediments that were eroded from the Variscan basement prior to the Turonian and deposited within a basin at the northern margin of the Bohemian Massif. Graphical abstract

Tectonic–Hydrothermal Processes and their Relationship with the Petroleum Potential of the Bazhenov-Abalak Complex of Western Siberia

Abstract —The main types of reservoir rocks have been identified within the Bazhenov-Abalak complex. To assess the geological resources of hydrocarbons, it is proposed to formally divide the entire set of lithological rock types comprising the Bazhenov-Abalak complex into two main varieties: fluid seals and reservoirs. We argue that it is possibile to distinguish between potentially productive and productive rocks, represented by siliceous and carbonate varieties, according to logging data. A possible mechanism for the formation of reservoir rocks within the Bazhenov-Abalak complex as a result of the tectonic-hydrothermal impact on these deposits has been reconstructed. An original methodology for identifying perspective zones of various categories of hydrocarbon accumulation in the Bazhenov-Abalak complex through integrating seismic data and tectonophysical modeling carried out on their basis has been proposed. For example, an assessment of the predicted geological resources of hydrocarbons contained in the Bazhenov-Abalak complex within the limits of 3D seismic exploration of the Yem-Yegovskaya area has been carried out. The necessity of assessing the prospects for oil content and calculating the predicted geological resources of hydrocarbons in the whole Bazhenov-Abalak complex, and not only in the Bazhenov Formation, is substantiated, based on a single mechanism of formation of reservoir rocks of tectonic-hydrothermal origin in them.

A geospatial approach to delineate lineaments on the granite gneissic terrain of Mpwapwa district, Dodoma, central Tanzania

The study sought to utilise Geographic Information Systems (GIS), Remote Sensing, and a blend of manual and automatic techniques to delineate and analyse the spatial distribution and orientation of lineaments within the terrain of Mpwapwa District. The study employed various techniques, including the Optimum Index Factor (OIF), Band Combination, Principal Component Analysis (PCA), and Directional Filtering on the Landsat 8 imagery, and Hill Shading technique was used on Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM). These techniques were employed in the processing steps for both manual and automatic lineament extraction, utilizing various software tools. Lineament control and validation were executed using digitized geological maps, topographical maps, and Google Earth images.The results revealed lineaments with a total length of 2060.6 km, non-uniformly distributed and predominantly present in hard rock lithologies, such as migmatitic granite, migmatitic biotite gneiss, biotite gneiss, granitoid gneiss, and porphyroblastic gneiss. The findings further indicate that NE-SW and NW-SE are the dominant lineament trends. Additionally, the study revealed that areas with medium, high, and very high lineament density and intersection are primarily located in the southwest and northeast parts of the Mpwapwa District. Meanwhile, regions with low lineament density are spread through the entire district.In this study, GIS and remote sensing emerged as valuable tools for identifying and mapping lineaments within a challenging hydrogeological setting. Findings from this study will serve as a foundational framework for subsequent geological and hydrogeological investigations in the area of study.

Chemical weathering in the Mekong River Basin: Clay mineralogy and element geochemistry of lower-reach river sediments

Chemical weathering of parent rocks in river basins plays a significant role in controlling the global geochemical cycle and climate change, especially in the world's largest river basins such as the Mekong River Basin in tropical regions. However, the chemical weathering process of the Mekong River Basin is still not well understood. In this study, clay mineralogy and major/trace-element geochemistry of fluvial sediments (clay, silt, and sand fractions) collected from the lower Mekong River Basin (Cambodia and Vietnam) were utilized to investigate the sediment provenance and chemical weathering process. The major-element compositions of the clay, silt, and sand fraction sediments from both the mainstream and tributaries consist of dominant SiO2, Al2O3, and Fe2O3, (84 wt%, 89 wt%, and 95 wt%, respectively) and minor K2O, Na2O, MgO, CaO, TiO2, P2O5, and MnO. The clay mineral assemblages in mainstream sediments are high in illite (36 wt%), moderate in kaolinite (28 wt%) and chlorite (26 wt%), and low in smectite (10 wt%), whereas those in tributary sediments are high in smectite (37 wt%), moderate in kaolinite (26 wt%) and chlorite (22 wt%), and low in illite (15 wt%). The different clay mineral assemblages between mainstream and tributary sediments can be significantly related to the parent rock lithology and/or the weathering process in the source region. On the basis of clay mineralogy and elemental geochemistry, river sediments of the mainstream in the lower reach may be derived mainly from felsic rocks in the lower part of the middle reach of this basin, with secondary contributions from the upper and lower reaches as well as the upper part of the middle reach. Sediments in the Kampi and Speu tributaries highly originate from felsic rocks, whereas sediments in the Srepok, Ter, and Chhiong tributaries can be mostly weathering products of mafic rocks. The clay mineral proxies (smectite/(illite + chlorite) and kaolinite/(illite + chlorite)) combined with the elemental geochemistry (CIA, αAlE values, and weathering trends) of the clay fraction sediments indicate intensive chemical weathering in the lower and middle reaches. The high-relief topography and cold and dry climatic conditions in the upper reach result in high illite and chlorite contents in the soil and moderate chemical weathering. The chemical weathering intensity increases from the upper to middle reaches and further to the lower reach. Tectonics in the middle and upper reaches of the Mekong River Basin play the most important role in controlling weathering and erosion processes, whereas East Asian–Indian monsoon climate conditions with warm temperature and predominant rainfall throughout the year and lithology are the main forcing factors for the intensity of chemical weathering in the lower reach.

IDENTIFICATION OF HYDROTHERMAL DISTRIBUTIONS USING THE WENNER-SCHLUMBERGER CONFIGURATION GEOELECTRIC METHOD IN LEMEU VILLAGE, LEBONG REGENCY, BENGKULU

The hot spring pool, Lemeu Village, Lebong Regency, is one of the geothermal fields. This research aims to identify the study area's geothermal potential and lithology. This is illustrated by the correlation method of resistivity and electrical conductivity values of rocks based on geoelectric measurements. This research uses the Wenner-Schlumberger configuration geoelectric method, as many as four tracks spread around the hot spring hill with a length of 480 meters, which are used to see variations in resistivity values that can indicate the presence of hydrothermal potential. The result is a 2D Resistivity model processed with Res2DinvX32 software. Based on the interpretation results, the subsurface rock lithology in each track is relatively similar in color, texture, grain size, and composition because it is around the hill. The Hulusimpang formation consists of clay, silty sand, tuff, andesite, basalt, and granite. Hydrothermal is found on lines 2 and 4 with resistivity values of 7.3 and 10.1 Ωm at a depth of 26 meters. Geothermal potential in the research area is divided into several temperature categories; some have low, medium, and high temperatures. In the research area, tracks 1 and 3 have low temperatures.

Grain textural bias in detrital single-mineral provenance studies

Detrital single-mineral geochemistry and geochronology are strong tools in provenance studies and indicate great potentials in addressing issues in earth sciences. Various biases (both natural and artificial) exist objectively and may mislead provenance interpretations. Both the sedimentary sorting process and hand-picking in-laboratory processing may lead to analyzed grain textural (e.g., size and shape) variability and thus may introduce biases in single-mineral provenance analysis. Here, we take the Mesozoic–Cenozoic Qaidam basin, northeastern Tibet, as an example to investigate the relationship between single-mineral grain texture and detrital zircon geochronological and detrital tourmaline, rutile and garnet geochemical data and to explain how grain texture affects detrital single-mineral provenance interpretations. Results indicate that Precambrian zircons take less proportions in coarse (>125 μm), subrounded and high aspect ratio (>2) fractions than Phanerozoic zircons. Parent rock lithology discrimination results of detrital tourmaline and garnet in different grain size fractions show significant differences. Zr-temperature values of detrital rutile have an increasing trend with increasing grain size. The geochemistry of detrital tourmaline, rutile and garnet shows no dependence with grain aspect ratio and roundness. We suggest that inheritance of grain texture features from parent rocks is the major reason. Detrital zircons from recycled (meta)sedimentary rocks tend to be smaller and more rounded than those from igneous rocks. Detrital tourmaline, rutile and garnet grains from different parent rock types vary in size. Grain textural bias may cause the underestimated contributions of the Qilian Shan to the Cenozoic Qaidam basin if small detrital zircons were not involved in the analysis. Quantitative description of the source-to-sink system of the Cenozoic Qaidam is also influenced by grain textural bias. This study highlights the underestimated grain textural bias in single-mineral provenance studies. We suggest that a comprehensive understanding of potential sedimentary sources, depositional processes, sample petrographic features and laboratory analysis procedures is important to reliable provenance interpretations and to related implications in earth sciences.

Research on the Development Height Prediction Model of Water-Conduction Fracture Zones under Conditions of Extremely Thin Coal Seam Mining

Addressing the difficult problem of predicting the height of water-conducting fracture zones in shallow and thin coal seams, a prediction model of water-conduction fracture zones based on a backpropagation (BP) neural network was developed by integrating theoretical analysis, field measurements, and algorithmic advancements. Firstly, through overburden migration analysis and correlation tests, the height index system of the water-conducting fracture zone was determined. This system includes mining height, buried depth, dip angle, working face width, and overburden rock lithology, with five groups of characteristic parameters. Then, 35 pairs of minefield-measured data were collected to establish the measured height data set of the water-conducting fracture zone. Secondly, a BP neural network prediction model and a traditional support vector regression (SVR) prediction model were constructed based on a Pytorch framework, and the models were trained and tested by selecting data sets. Thirdly, the optimal prediction model was determined by comparing the model with the empirical model and multiple regression model of mining regulations for coal pillar maintenance and pressure in buildings, water bodies, railways, and main shafts. Finally, a typical mine was selected for application to verify the suitability of the optimal model. The results show that: (1) the predicted value of the neural network model is consistent with the change trend of the measured value, which accords with the theoretical law; (2) compared with traditional forecasting methods, the error of the BP neural network prediction model is stable and the prediction effect is the best; (3) dropout can effectively mitigate mitigation training overfitting, achieve regularization, and improve prediction accuracy; (4) the field application further verified that the BP neural network model is the best for predicting the height of water-conducting fracture zones of extremely thin coal seams, and the research results can provide technical guidance for similar fragile coal seams.

Rock lithology classification algorithm based on improved self-attention mechanism VIT

Abstract When applying VIT to image classification, although good accuracy has been achieved, there is a limitation on the number of stacked layers. The similarity between different tokens increases as the model deepens, leading to low accuracy in shallow VIT models and wasting computational resources in deep VIT models. To address this issue, a multi-valued self-attention mechanism is proposed. By introducing an additional clue “V,” that does not vary arbitrarily, the dot product similarity observes each position in the token sequence more, reducing the depth of the attention mechanism network and avoiding the problem of similarity disappearing between deep tokens. Additionally, the loss function is improved by combining the Focal Loss function with Label Smoothing, enhancing the model’s handling of uncertain images while retaining the category focus of Focal Loss. Experiments are conducted on a rock lithology classification dataset, showing that compared to the VGG model and ResNet-18, the accuracy of the ResNet-50 model improves by 17.6%, 12%, and 4.9%, respectively. This paper also demonstrates the effectiveness of the multi-valued self-attention mechanism, which significantly reduces depth and parameter count while maintaining comparable accuracy. Finally, generalization experiments on the CIFAR-10 dataset further validate these conclusions.

Machine learning and remote sensing-based lithological mapping of the Duwi Shear-Belt area, Central Eastern Desert, Egypt

Machine learning and remote sensing techniques are widely accepted as valuable, cost-effective tools in lithological discrimination and mineralogical investigations. The current study represents an attempt to use machine learning classification along with several remote sensing techniques being applied to Landsat-8/9 satellite data to discriminate the various outcropping lithological rock units at the Duwi Shear Belt (DSB) area in the Central Eastern Desert of Egypt. Multi-class machine learning classification, multiple conventional remote sensing mapping techniques, spectral separability analysis based on the Jeffries-Matusita (J-M) distance measure, fieldwork, and petrographic investigations were integrated to enhance the lithological discrimination of the exposed rock units at DSB area. The well-recognized machine learning classifier (Support Vector Machine—SVM) was adopted in this study, with training data determined carefully based on enhancing the lithological discrimination attained from various remote sensing techniques of False Color Composites (FCC), Principal Component Analysis (PCA), and Minimum Noise Fraction (MNF), along with the fieldwork data and the previously published geologic maps. High overall accuracy of the SVM classification was obtained, however, inspection of the individual rock unit classes’ accuracies revealed lower accuracy for certain types of rock units which were also found associated with lower separability scores as well. Among the least separable rock units were; metagabbro rocks that showed high spectral similarity with the volcaniclastic metasediments rocks, and the metaultramafics of the ophiolitic mélange showed spectral attitude of high correlation to that of the Hammamat volcanosedimentary rocks. Target-oriented Color Ratio Composites (CRC) technique was implemented to better discriminate these hardly separable rock units. A final integrated geological map was obtained comprising the various discriminated Neoproterozoic basement rock units of the DSB area. The successfully mapped litho-units include; Meatiq Group (amphibolites, gneissic granitoids, and mylonitized granitoids), ophiolitic mélange (metaultramafics, metagabbro-amphibolites, and volcaniclastic metasediments), Dokhan volcanics, Hammamat sediments, and granites. An adequate description of these rock units was also given in light of the conducted intense fieldwork and petrographic investigations.

Identification Of Liquefaction Slide Planes Using The Geoelectric Resistance Type Method In Balaroa Village

Introduction: Research has been conducted with the title "Identification of Liquefaction Sliding Fields Using the Type Resistance Geoelectric Method in Balaroa Village". This study aims to determine the subsurface constituent rock layers and the position of the sliding plane based on the type resistance data. Method: This study consists of 6 measurement tracks with a track length of 150 meters using the Vertical Electrical Sounding (VES) method with the Schlumberger configuration. Data processing uses the software program Progress version 3.0 and ipi2win. Results and Discussion: The results obtained indicate the presence of subsurface constituent layers, namely: Passive clay, clay sand, and gravel, and the presence of an inclined plane of 25° to 55.5% with a steep slope. Conclusion: Based on data analysis and interpretation, it can be concluded that the rock lithology at the study site consists of passive clay, clay sand, and gravel, based on the value of specific resistance. The slope of the sliding plane layers that have the potential to trigger landslides and liquefaction at the site tends to be west-east with a slope angle of 25°, or 55.6%, which is included in the steep slope category

Identification of Aquifer Layer Using Geoelectric Method in Oil Palm Plantation Area of PT Unggul Widya Teknologi Lestari Pasangkayu Regency

Introduction: Aquifer layers have been identified in the oil palm plantation area of PT Unggul Widya Teknologi Lestari Pasangkayu Regency. This study aims to determine the lithology of subsurface rocks and the depth of the aquifer layer as a source of clean water in the study area. Method: This study uses the geoelectric method of type resistance with Wenner configuration, with the number of electrodes 24 rods and a spacing of 10 meters. 2D cross-sectional model using Res2Dinv software program. Results and Discussion: Based on the value of the type resistance of the subsurface constituent rock lithology at the research site is interpreted to consist of three layers, namely clay with a specific resistance value &lt; 29.15 Ωm, sand and sandy clay with a specific resistance value of 29.15 Ωm to 72.89 Ωm, and conglomerate with a specific resistance value &gt; 72.89 Ωm. The aquifer layer is interpreted with a specific resistance value of 29.15 Ωm to 72.89 Ωm. The aquifer layer is detected to spread from the northeast to the southwest of the research site with a depth of ±25-39 m. Conclusion: In the oil palm plantation of PT Unggul Widya Teknologi Lestari, the subsurface layer consists of clay (1.98 Ωm - 29.15 Ωm), sand and passive clay (29.15 Ωm - 72.89 Ωm), and conglomerate (72.89 Ωm - 1120.5 Ωm). Thin aquifers, with a thickness of 5-10 m and depth of 25-39 m, are detected in the sand and sandy clay layers.

Study of rock-breaking performance of V-axe-shaped PDC cutter in tight sandstone formation

In the field of oil and gas drilling engineering, tight sandstone strata are one of the strata that are difficult to drill. The V-axe-shaped cutter has a good effect in crushing tight sandstone strata. However, there were few studies on its specific structural parameters and rock-breaking performance in tight sandstone formations. To further explore its structural parameters and rock-breaking performance, this paper studies the rock-breaking performance of a V-axe-shaped PDC cutter in tight sandstone formation by combining experiments with finite element simulation. Mechanical tests show that the compressive strength is high, with values of 130.3 MPa, 223.3 MPa, and 271.6 MPa under confining pressures of 0/15/30 (MPa), respectively, with the condition of 0.02 mm/min loading rate. Rock lithology tests that the sandstone in this formation has strong abrasiveness. The penetration ability should be considered when evaluating the rock-breaking performance of cutting cutters. The results show that the V-axe-shaped PDC cutter mainly uses shear, extrusion, and point load to break rock together. It has a stronger ability and stability to attack the rock. With a 100° V-shaped angle (α) and 140° Axe-shaped angle(β) has the best rock-breaking property. The back-rake angle of the cutter can reduce cutter vibration and significantly improve PDC bit rock-breaking efficiency. The optimal rock-breaking back-rake angle of the V-axe-shaped cutter is 20° in dense sandstone formations. With the increase of wear height(0–3 mm), the synthetical mechanical specific energy (MSE) is reduced by 11.53%, 6.30%, 10.30%, and 33.28%, respectively, compared with the conventional cutter. The tests indicate that the rock-breaking efficiency of the V-axe-shaped PDC cutter is 12.9% higher than that of the conventional PDC cutter. The application of V-axe-shaped cutters on the bit is expected to improve the rock-breaking efficiency and footage of PDC bit in tight sandstone formations and realize the development of low-cost and high-benefit oil and gas resources.

Effect of Rock Lithology and Reloading Direction on Rock Stress Memory

Effect of Rock Lithology and Reloading Direction on Rock Stress Memory

Quantitative Elimination of Seismic Pseudofaults and Fine Analysis of True Faults Underlying Igneous Rocks of No-Well Areas: A Case Study of Shuntuoguole Uplift in Tarim Basin

Abstract After multistage tectonic movement and evolution, large superimposed oil and gas basins generally developed many igneous rocks in the early rifting stages. The lithology and lithofacies of igneous rocks are complex, which is easy to lead to the distortion of the underlying migration velocity field and thus the response of seismic pseudofaults. Also, because of the obvious shielding and absorption effect of igneous rocks on seismic waves, the waveform quality of underlying strata is poor and the seismic response characteristics of faults are fuzzy. Currently, relevant studies have shown that the influence of igneous rock can be eliminated by the prestack depth migration with an accurate igneous rock velocity model. However, improving the accuracy of the velocity model needs to be corrected by well-logging data, resulting in poor applicability of the existing velocity modeling technology underlying igneous rocks without well, which is an obvious technical bottleneck. In this paper, the secondary strike-slip fault in Shuntuoguole low uplift of Tarim Basin, which has great oil and gas exploration potential but a very low degree of drilling, is selected as the research object. Aiming at difficult fault detection underlying igneous rocks caused by lack of drilling, the accuracy of fault seismic identification is improved by “interpretative fault preprocessing” and “fault sensitive attribute optimization.” In addition, through the “extreme hypothesis method” to maximize the complex migration velocity and simulate the underlying target layer distortion maximization, we realize the quantitative elimination of seismic pseudofaults. The practical application shows that this technology can determine the true and fake underlying faults quantitatively without establishing an accurate igneous rock velocity model. It is crucial not only for exploring oil and gas in the Tarim Basin’s secondary strike-slip faults but also for offering a method and technical guide for identifying faults in other basins affected by igneous rocks.