Rock Formations Research Articles

Anthropogenized Karst Landscapes in the Area of the Pismata Locality in the Canyon Valley of the Rusenski Lom River near the Village of Ivanovo

The present paper is an attempt to reconstruct and assess the impact of localized, studied and documented permanent changes in anthropogenic rock sections, forms and formations. The karst rock crown shapes to a large extent the area of Pismata near the village of Ivanovo, Ruse region. It has for centuries suffered an active anthropogenic impact. The same has led to the gradual transformation of the vast majority of natural rock niches, caves, sheds, rock bridges and other karst formations into sites with different purposes for humans. The stages of human economic, household and cultural activity in the region have influenced the modern appearance of entire rock sections, passages, terraces and have led to the gradual formation of typical samples of anthropogenic karst landscapes. These samples can be used as a model and comparative material in identifying and studying different types of architectural, cultural and historical anthropogenic karst landscapes in the canyon valleys of the Rusenski Lom River and its tributaries, and in other areas with similar landscapes.

Blasting of Unstable Rock Elements on Steep Slopes

The improvement of safety conditions on hazardous rock slopes in civil work, mining and quarrying, and urban environments can be achieved through the use of explosives for the removal of unstable rock elements and final profiling. This technique is often applied because, in most cases, drill and blast operations, where they can be used, are cheaper and faster than other techniques and require fewer subsequent maintenance interventions. Blasting represents a suitable and effective solution in terms of different geometries, rock formation types, access to site, safety, and the long-term durability of results. The primary purpose of this approach is the improvement of the safety conditions of sites, depending on their local features, as well as the safety of workers, so that the blasting scheme, geometry, and firing can be carefully adapted, thus imposing relevant limitations on the operating techniques. All these constraints associated with complex logistics make it difficult to standardize the demolition technique, due to different situations in terms of extension, location, fracturing state, and associated traffic risk. Considering the significant number of influencing factors for both the rock mass features and for the topography, the present research has been necessarily validated through the analysis of several case histories, thus on an experiential basis focusing on some simple control parameters to help engineers and practitioners regarding the first design and control of blasting schemes.

Site-Specific Hydrogeological Characterization for Radiological Safety: Integrating Groundwater Dynamics and Transport

The radiological impact of radionuclide transport via groundwater pathways at the Wolsong Low- and Intermediate-Level Waste (LILW) Disposal Center was estimated by considering site-specific characteristics, including hydrogeology, geochemistry, and land use. Human intrusion scenarios, such as groundwater well development, were analyzed to evaluate potential pumping volumes and radionuclide migration pathways. Particular attention was given to the hydrological and geochemical aspects of radionuclide transport, with a focus on local aquifer heterogeneity, flow dynamics, and interactions with engineered barriers and surrounding rock formations that delay radionuclide migration through sorption and other retention mechanisms. Sorption coefficients (Kd), calibrated using site-specific geochemical data, were incorporated to ensure realistic modeling of radionuclide behavior. A hierarchical approach integrating scenario screening, particle tracking techniques, and mass transfer modeling was employed. Numerical simulations using FEFLOW ver. 7.3 and GoldSim ver. 14.0 software provided insights into near-field and far-field transport phenomena under well pumping conditions. The results revealed distinct spatial flux behaviors, where carbon-14 (14C) dominated near-field flux due to its high inventory, while technetium-99 (99Tc) emerged as the primary dose contributor in the far-field flux, owing to its anionic nature and limited sorption capacity. Additionally, under high-pH conditions near concrete barriers, cellulose degradation into isosaccharinic acid was identified, enhancing radionuclide mobility through complex formation. These findings underscore the importance of site-specific sorption and speciation parameters in safety assessment and highlight the need for accurate geochemical modeling to optimize waste placement and ensure long-term disposal safety. The outcomes provide valuable insights for optimizing waste placement and contribute to the development of evidence-based safety strategies for long-term performance assessment.

An investigation into the impact of diapir structures on formation pressure systems: a case study of the Yinggehai Basin, China

Under the influence of diapir structure, the formation pressure system is complicated. The characteristics of high temperature and high pressure are obvious, the prediction is difficult, and complex accidents such as well kick and leakage are frequent, which seriously restrict the efficient development of oil and gas resources. Therefore, taking Yinggehai Basin in China as an example, combined with the evolution characteristics of diapir structure, the influence of diapir structure on abnormal high-pressure, wellhole collapse and fracture is analyzed. Three pressure calculation methods are selected, and the distribution rules of pressures and safety density window are analyzed, too. The results show that the diapir structure and its associated fault not only constitute the fluid transport system, but also make the deep overpressure transfer upward and accumulate into high pressure in the shallow formation, and the development of the associated fault destroy the integrity of the formation rock and reduce the strength of the rock. The upwelling of hot fluid changes the local geothermal conditions, reduces the hydrocarbon generation threshold of shallow source rocks, promotes the evolution of clay minerals, causes hydrothermal expansion, and enhances the shallow high pressure. In high-temperature environment, the cooling effect of drilling fluid will produce heating stress, change the stress distribution around the wellhole, and increase the risk of wellbore instability. Additionally, under the influence of diapir structures, the pore pressure in deep formations increases, while the fracture pressure decreases, resulting in a significantly narrowed safe density window. The safety density window width generally presents a half-spindle shape, and with the increase of depth, the window width increases first and then decreases.

Mechanical and Permeability Characteristics of Gas-Bearing Coal Under Various Bedding Angles

Coal structures are commonly found in coal rock formations. Understanding the evolutionary laws of mechanics, deformation, and permeability of gas-bearing coal rock during the failure process at different bedding angles is crucial for studying the prevention and control techniques of coal and rock gas dynamic disaster mitigation. In this study, a mechanical seepage test of gas-bearing coal under various bedding angles was conducted using the fluid–solid coupling triaxial servo test system. The results indicate the following corrections: ① Both axial peak strain (ε1) and radial peak strain (ε3) initially increase and then decrease, reaching their maximum values at 45°, indicating that the specimen eventually slips along the bedding plane and fails. ② As the bedding angle increases, the peak stress of the coal body shows a “V”-shaped distribution, with the peak strength of the gas-bearing coal sample being the lowest at 60°. ③ The minimum permeability of the coal sample increases with the rise in the bedding angle. The bedding direction of the coal samples at 90° and 75° aligns with the axial direction, leading to more seepage channels. ④ At a bedding angle of 60°, the minimum dissipated energy (Ud) is required for sample failure, indicating that the sample is highly prone to failure.

MODELING OF THREE-DIMENSIONAL SUBSURFACE STRUCTURES BASED ON GRAVITY ANOMALY IN SOUTHWEST SUMBA INDONESIA

Modeling subsurface conditions using gravity anomaly data, focusing on density contrasts, provides critical insights into subsurface structures and supports identifying rock types. This study aims to define residual gravity anomalies in the Sumba region and utilize them to develop a three-dimensional subsurface model of Southwest Sumba, characterizing density contrasts and associated rock formations. Gravity data from the TOPEX dataset were employed in this research. The Airy isostasy model was applied to separate regional and residual anomalies, followed by a three-dimensional inversion using the Generalized Cross-Validation (GCV) method. The results reveal residual gravity anomalies range from -170 mGal to 211 mGal, with the Java Trench exhibiting the highest anomaly. The 3D modeling shows a relatively homogeneous density contrast at shallow depths, transitioning to more erratic variations at greater depths, extending to 15 km beneath Southwest Sumba Island. Furthermore, the calculated densities are consistent with the region's known geological background. The Java Trench, located south of Sumba, notably demonstrates a consistently high-density contrast from shallow to deeper depths, highlighting its tectonic complexity.

Using machine learning methods for prediction of drilling rate: case of water drilling operations in gneiss rock

ABSTRACT An accurate model for ROP prediction in gneissic rock formations was proposed in this study to help reduce drill costs, total drilling time, and allowing companies to be more competitive. The developed ROP prediction model has considered for (04) parameters: percussion pressure, blowing pressure, pressure of compressor, rotation speed. Pressures values range between 5 and 294.3 MPa, while the drilling time and drilling depth ranges from 1.17 h to 44.21 h and from 1.8 m to 4.6 m respectively, for a constant rotation speed of 1 526 tr/min. Multi-Layer Perceptron, Multiple Regression, K-Nearest Neighbors, Ridge Regression and Random Forest have been used for training and validation tests. Comparisons of results based on the R2 shows that the best model is obtained through the Random Forest method, with an R2 of value 0.974 while the second-best method is the K-Nearest Neighbors method, with an acceptable R2 of 0.737. Related RMSE and MAE obtained from both methods are relatively low, with values of 0.0794 m/h and 0.254 m/h for RMSE, and 0.0123 m/h and 0.041 m/h for MAE respectively.

Formation evaluation for Mauddud Formation in Bai Hassan oilfield, Northern Iraq

Formation evaluation is a critical process in the petroleum industry that involves assessing the petrophysical properties and hydrocarbon potential of subsurface rock formations. This study focuses on evaluating the Mauddad Formation in the Bai Hassan oil field by analyzing data obtained from well logs and core samples. Four wells were specifically chosen for this study (BH-102, BH-16, BH-86, and BH-93). The main objectives of this study were to identify the lithology of the Mauddud Formation and estimate key petrophysical properties such as shale volume, porosity, water saturation, and permeability. The Mauddud Formation primarily consists of limestone and dolomite, with some anhydrites present. It is classified as a clean formation due to its low shale volume of approximately 17%. The results of the study show a low water saturation of around 30% and an effective porosity reaching up to 32% (with an average of 11%). The Mauddud Formation was further analyzed using the cluster analysis method, which identified four distinct hydraulic flow units (HFUs). The permeability of the Mauddud Formation was predicted using the flow zone indicator method, revealing a range from moderate to sound quality, averaging approximately 22 md.

Determination the depth and thickness of the Yamama Formation using the reflection seismic method in the Nasiriyah field-Southern Iraq

An interpretive study of the Yamama Formation for seismic data in the Nasiriyah oil field was achieved in this work. We choice this location for our study because of its important location between several oil fields. Using SERVPRO-10, the NS-1 well data and the seismic data were represented by time, depth, velocity, thickness, and three-dimensional mapping of the thickness distribution. The seismic interpretation of the upper and lower-time maps of the Yamama Formation showed the presence of faults towards the southwest and northeast as a result of the influence of the transverse fault system. Structural features of the Yamama Formation was also identified from the depth maps, with seven closures identified in the upper boundary and three in the lower boundary, representing the lowest occurrence of structural influence. The 3D map showed the highest value of formation thickness in the northeast direction, and that represents the distribution of formation rock units the directions of increasing sediment thickness, and the deposition location from the shelf margin to the sedimentary basin, indicates the increasing in sedimentation energy of the basin. Petrophysical properties of the Yamama Formation maps show a significant increase in the value of density and velocity and its relationship with acoustic impedance and a decrease in porosity from northeast to southwest directions

Karren of Provence (France), Gréolières, Caussols, Tourrettes-sur-Loup and Luberon

The rock relief of karst forms, either of surface forms or of caves which are forming on different carbonate rocks and under different conditions, is one of the most telling traces of their formation, along with the characteristic factors and development. Therefore, we meticulously studied and examined the geological features and rock formations, as well as how they fit into the rocky relief. The diverse shaping of the karst surface is revealed by the rock relief of selected karren on different carbonate rocks, fine-grained homogeneous and compact limestones, as well as porous fine-grained sandstones. We have also newly explained the formation of parallel channels on the inclined surfaces of denuded rock (Gréolières); the gradual reshaping of the rock surface from a subsoil one to one directly exposed to rain and water creeping along the gently sloping rock (Caussols). Furthermore, the unique shaping of carbonate sandstones, specifically such with large channels (Tourrettes-sur-Loup) is presented for the first time. The speed of karstification of younger carbonate rocks is revealed by channels on the walls of the palace in Avignon.

Effect of Temperature on Kerogen Transformation and Hydrocarbon Generation in Bazhenov Formation (Western Siberia, Russia) Rocks During Hydrous Pyrolysis

The aim of this investigation is to determine the role of temperature in hydrocarbon generation in Bazhenov formation source rocks, as hydrothermal processes in situ are supposed to be the main contributor to kerogen transformation in Western Siberia. Laboratory modeling of organic matter isothermal transformation in powdered and extracted samples by hydrous pyrolysis at 300 °C, 325 °C, 350 °C, 375 °C, and 400 °C for 24 h was performed. Heated samples were analyzed via pyrolysis, and hydrocarbons were investigated by GC and GC-MS. Results show that more than 90% of the kerogen generation potential was utilized. The amounts of liquid and gaseous products reached 82 and 126 mg of hydrocarbon/g TOC, respectively. The volume of generated gas increased while the maximum production of liquid decreased with temperatures over 350 °C. The biomarker composition of liquid products at different temperatures was similar. The characteristics of kerogen and the product composition had a high correlation with the parameters for samples naturally formed in situ under an elevated heat flow. More subtle chemical analyses are required to determine the effects of kerogen’s chemical structure and the rock mineral composition on oil and gas generation.

Correlation of Damage in Rocks Dynamically Loaded by Percussive Tools Using Piston Coefficient of Restitution (COR)

AbstractEfficient drilling operations require optimal drilling parameters to achieve higher penetration rates and minimize tool wear. This study focuses on characterizing the piston coefficient of restitution (COR) as a damage indicator for rocks dynamically loaded by percussive tools. The COR offers a nuanced understanding of damage, particularly at low impact energies where plastic deformation beneath the insert and sub-surface fractures predominates over chip mass removal. Various design parameters, including piston-to-bit mass ratio, piston length and impact velocity, were varied to evaluate their impact on the piston COR in pristine rock samples. Tests were conducted on granite, sandstone and limestone, all common rocks in down-the-hole hammer drilling. Despite variations in the impact energy level, the influence of mass or length ratios on the COR and the resultant destroyed rock volume was minimal. X-ray computed tomography revealed the significance of the crushed zone beneath the crater, affecting the rock ability to exert mechanical work on the bit during unloading. This characteristic led to the identification of a distinctive non-linear shape in the COR curves, with clearly delineated regions for each rock type, corresponding to different damage rates. These findings underscore the potential of the piston COR as a valuable tool for aiding in the identification of optimal drilling parameters and understanding rock formation characteristics during drilling.

Fault Gouge Permeability Under Confined Conditions: An Investigation for CO2 Storage Applications

This investigation provides an in-depth experimental analysis of the prepared artificial fault gouge material on permeability characteristics as a function of the confining pressures and injection flow rate pertinent to both CO2 storage and subsurface fluid flow that addresses an ultimate challenge in CO2 storage. The purpose of the research is to gain a better understanding of the role of fault gouge material in structuring fluid flow patterns within geological media and improving the safety and efficiency of subsurface storage systems. In order to ensure the reproducibility of the experimental program, fault gouge material that resembled the size distribution and material type observed in the field and reported within the literature was purposefully designed and prepared. A set of core-flooding experiments were conducted to evaluate the relationships between permeability, confining pressure, and fluid flow rates. The subsequently obtained results showed that lower permeability is always the result of increasing confining pressure, highlighting the significance of fault gouge material for controlling fluid flow in fractured rock formations. These conclusions provide novel insights and can be applicable in practice when evaluating the integrity of CO2 storage sites, which calls for knowledge of permeability behavior under high-stress conditions.

Application of Pumping Tests to Estimate Hydraulic Parameters of Volcanic Aquifers in Lake Tana Basin, Ethiopia

The purpose of this study was to enhance the understanding and sustainable groundwater management of volcanic aquifer systems by estimating key hydrogeological parameters. The transmissivity of a volcanic aquifer system was estimated using analytical solutions based on 68 constant rate and recovery data sets collected from various sources. A combination of hydro-lithostratigraphy and diagnostic plots was employed to identify the aquifer types and flow conditions, which facilitated model selection. Transmissivity of the confined aquifer was modeled using both Theis and Cooper–Jacob methods, with the Theis residual drawdown solution utilized for estimation. For the unconfined aquifer, the Neuman method was used, and the Hantush/Jacob method was employed for leaky aquifers. The results showed that the transmissivity of the Tertiary basalt varied from 0.38 m2/d to 860 m2/d, while the Quaternary aquifer system ranged from 2.33 m2/d to 1.8 × 104 m2/d, indicating an increase in transmissivity with younger volcanic flows. Specific capacity (SC) was estimated for 74 wells and the values ranged from 0.62 to 5860 m2/d. This wide variation of specific capacity and transmissivity showed significant heterogeneity within the volcanic aquifers. This study introduces the innovative application of derivative diagnostic plots in groundwater research, offering an efficient approach for analyzing and interpreting pumping test data to characterize aquifer systems in various hydrogeologic units. This study focuses on aquifer characterization in hard rock formation, demonstrating methods that can be applied to similar geological environments globally. For the Blue Nile basin in general and for the Lake Tana basin in particular, the study result of aquifer characterization will contribute to exploration, development, and improved groundwater management in the region.

Characterization of Dolomite Stone Broken Under Axial Impact

As the extraction of oil and gas progresses into deeper and ultra-deep geological formations, the enhancement of rock-breaking efficiency in drill bits has emerged as a critical factor in ensuring energy security. Among the various techniques employed, vibratory percussion drilling technology is widely recognized for its ability to improve both the efficiency and speed of penetrating hard rock formations. This study examined the effects of varying loading conditions on the characteristics of rock fracture and damage, maintaining a constant cutting speed and lead angle. By designing a small polycrystalline diamond compact (PDC) drill bit and incorporating simulation results, the research sought to analyze the influence of axial impact components on the efficiency of breaking dolomite samples, as well as the effects of impact frequency and amplitude on drilling pressure and rock-breaking energy. The findings revealed that an increase in the axial impact amplitude significantly enhanced rock-breaking efficiency, elevated von Mises stress, and increased principal compressive stress. An increase in impact frequency effectively reduced the overall stress and frictional work. These results underscored that the stress analysis revealed that the peak stress increased at lower impact amplitudes, with notable changes occurring at an amplitude of 1.5, leading to a 100% increase in Mises peak stress compared with an amplitude of 1.0. Axial impact drilling promoted deep crack formation and the development of a tensile damage zone beneath the cutter, indicating its effective rock-breaking capabilities. Axial impact drilling significantly reduced the threshold drilling pressure compared with conventional rotation, with an impact amplitude of 0.3 mm decreasing the static load by 44.1%. Additionally, increasing the axial impact amplitude enhanced the rate of penetration (ROP) while maintaining a constant static load, resulting in remarkable efficiency improvements. The results of the study are expected to provide theoretical guidance for the mechanism of impact rock breaking and the design of impact rock-breaking tool parameters.

Exploring Talc Deposits: Physical Characteristics, Geological Factors, and Formation in Ultramafic and Mafic Rocks—A Comprehensive Review

Exploring Talc Deposits: Physical Characteristics, Geological Factors, and Formation in Ultramafic and Mafic Rocks—A Comprehensive Review

Mechanical properties and microstructural analysis of laterite stone masonry from India for sustainable construction

Laterite is a naturally occurring rock formation that is used worldwide as a building material in tropical regions. Its unique features have enabled some of the most astounding architectural feats, which irrevocably altered the cultural and historical contexts of their surroundings. This study examines the laterite stone masonry performance, with a specific focus considering its mechanical properties, mineral composition, and microstructure. However, mineralogical composition and microstructural features vary, affecting mechanical qualities and endurance. The study also extensively examines four varieties of laterite samples used for construction in the Udupi region. Experiments were performed to determine the percentage of water absorption and its impact on the compressive strength of Laterite stone. L1 Laterite stone showed better performance due to its exceptional strength. It surpasses the other samples and is well-suited for the construction of load-bearing structures as it aligns with the IS 3620 standards. Stack bond masonry prism samples were built using four varieties of laterite stones with 1:6 cement mortar for the joints. These prism specimens were subsequently tested under compression, tension, and shear loading to determine the variation in their behaviour. The series of tests performed revealed that the prisms failed due to splitting and crushing under compression loads. In shear and tensile bond tests, all laterite masonry prism samples failed due to rupture of the joint. Microstructure study confirmed that the increased strength of lateritic samples L1 and L2 is due to less prominent clay particles coupled with a higher percentage of ferrous content.

Key Parameters of the Roof Cutting and Pressure Relief Technology in the Pre-Splitting Blasting of a Hard Roof in Guqiao Coal Mine

The phenomenon of crushing the support of the hard roof of a coal seam occurs occasionally during the coal mining process. However, making the hard roof fall is difficult due to its good integrity and high strength. A vast area of unsupported, suspended roof can easily form in the goaf, inducing the hidden dangers of rock burst and coal and gas outbursts. A deep-hole pre-splitting blasting technique is used to fracture the roof and relieve the pressure exerted by the rigid roof in order to improve the caving of the hard roof and protect the stability of the roadway, ensuring safe and effective operational production of the 1127 (1) working face in Guqiao Coal Mine. By collecting field samples, the mechanical properties of relevant rock formations are ascertained. Combining numerical simulation with theoretical computation, a roof cutting pressure-relief scheme with a roof cutting height of 13.5 m and a roof cutting angle of 20° is selected. This scheme can decrease the peak vertical stress on the roadway roof from 22.01 MPa to 13.63 MPa compared to when roof cutting is not performed. By ensuring the effectiveness of roof cutting for pressure relief, this scheme can optimize the actual construction workload to a minimum. The study’s conclusions provide insightful information and can be used as a guide for future research on related technical topics.

Experimental Study on the Output Characteristics of a Novel Intensifier Controlled by an Electromagnetic Valve

The application of ultra-high-pressure (UHP) water jets for rock slotting in the bottom hole has been recognized as a highly effective approach to enhance rock-breaking efficiency. However, the current downhole intensifiers are confronted with various limitations, including the short duration of UHP pulse water jet output and challenges in attaining both controllable and adjustable output frequencies, consequently leading to compromised slotting efficiency. In this study, a novel intensifier controlled by an electromagnetic valve was designed, and a visual test platform was constructed to investigate the output pressure characteristics and their influencing factors. The output characteristics of the intensifier consist of a mixed pulse jet composed of high-pressure and low-pressure jets, resulting in a square wave-like output waveform with an adjustable frequency. The output pressure characteristics of the intensifier are primarily influenced by the input pressure and the switching time of the electromagnetic valve, assuming that the structural parameters are constant. Increasing the input pressure raises the peak pressure, thereby enhancing the slotting capability of the jet stream. Aligning the switching time of the electromagnetic valve with the rotation period of the drill bit improves the slotting efficiency. In the lab tests, the output pressure of the intensifier was successfully increased to 118.2 MPa, with a sustained duration of a high-pressure jet segment for 2.1 s. These research findings offer a new method for enhancing drilling efficiency in deep hard rock formations.

Contribution to the Petrographic Study of the Geological Formations of the Mbanga Sector and its Headwaters in the Tshela Territory (Central Kongo, DRC)

In order to fill the glaring gaps in the geological data for the Mbanga region and surrounding area, in the Province of Kongo-Central in DR Congo, geological investigations were carried out in the field over a three-week period. The results obtained, coupled with those from the laboratory, led to the identification of eight different lithofacies in the study area, namely: metaryolites, sericite schists and biotitose schists, all with grey to greenish grey facies. This work consists of a detailed petrographic study to identify the different facies of the West Congo Supergroup belonging to the Mayumbian Group and the Zadinian Group. The geology of the Mbanga sector and its surroundings is made up of metamorphic layers of volcanic and sedimentary origin. The various rock formations in our study area are grouped into two West Congo Supergroup groups; the metarhyolite formation belongs to the Tshela/Seke-Banza Group (Mayumbian) and the others belong to the Matadi Group (Zadinian).