Strata Research Articles

Lava–water–sediment interaction: Dolomite U[sbnd]Pb dating marks the Cenozoic Ocean–continent transformation in the southwestern Tianshan Mountains

The regression of the Neotethys Ocean from the southwestern Tianshan Mountains remains debatable because of notable sedimentary discontinuities and lack of fossil evidence. This study aimed to explain this problem by applying comprehensive carbonate UPb dating to newly recognised pyroclastic rock layers in the Tuoyun Basin, southwestern Tianshan Mountains. These rocks, referred to as peperite in the early literature, are not like typical pyroclastic rocks; rather, they are formed by the mixing of magma with wet sediment. Field observations have revealed that the pyroclastic rock layers are overlying Cenozoic pillow basalts and then covered by the later columnar jointing basalts, recording a transformation from marine to terrestrial environment. The dolomite-dominated mineralogy and major element analysis indicate that the pyroclastic rock is dolomitic in composition. The sedimentary origin is supported by the δ18OSMOW values (23.7‰ to 36‰) and δ13C values (−6.48‰ to −7.08‰) of the bulk-rock pyroclastic rock and the δ34S values (−20.79‰ to 23.86‰) of native sulfur. However, the relatively depleted initial ratios of 87Sr/86Sr (0.7048–0.7065) and εNd(t) values (−0.52 to +3.10) suggest the possibility of isotopic exchange with the conjugate basalts. For carbonate from Tuoyun pyroclastic rock, UPb isotope dating using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA–MC–ICP–MS) produced well-defined Lutetian ages of 46.1 ± 0.5–41.7 ± 0.6 Ma. This indicates that the Tuoyun region was in a marine environment during the Lutetian epoch and then transformed into a continental environment after the marine regression. In this study, we successfully applied the UPb technique by LA–MC–ICP–MS to constrain the timing of ocean–continent transformation through carbonate UPb dating. These findings explain the regression of the Neotethys Ocean from the southwestern Tianshan Mountains and offer novel insights into the geological evolution history of this region.

Development of a method for identifying cracks in permafrost rocks based on differentiation of GPR data

Relevance. The presence of cracks significantly affects the physical and mechanical properties of rocks, which must be taken into account when planning mining operations and building mining structures. In the conditions of the distribution of permafrost rocks, characteristic of the North-East of Russia, the study of fracturing is possible using the ground penetrating radar method, which is used to assess the structure of rock masses of placer deposits. The criteria for identifying cracks based on the characteristics of GPR wave fields are currently known, and the main problem preventing the full use of the GPR method for studying cracks in subsurface layers of rocks is the significant complexity of processing and interpreting GPR measurement data. The purpose of the work is to develop a method for processing the results of ground penetrating radar measurements to identify cracks in frozen rocks. Methods. Physical and computer modeling of GPR measurements of a rock mass with a fracture, differential calculus methods for analyzing the GPR wave field structure model. Results and their scope. As a result of the research, based on an early developed model of the structure of the GPR wave field, the use of the differentiation operation for identifying cracks in permafrost rocks was justified. Special cases of rectilinear inclined and horizontal axes of in-phase of ground penetrating radar signals are considered and corresponding formulas are obtained for them. The theoretical results obtained were tested on computer and physical modeling data, as well as on field measurement data. An analysis of the features of the signals after differentiation was carried out, and the features of the original radargrams were noted, which may interfere with the reliable interpretation of the results obtained. Conclusions. In the practice of processing data from ground penetrating radar measurements, the results of the research will make it possible to more quickly identify zones of increased fracturing in rocks. In the future, it is planned to develop an algorithm and software that implements it for mapping rock fractures using ground penetrating radar data.

Reservoir impoundment-triggered seismicity in Brazil: the case of M4.0 Nova Ponte earthquake

Reservoir-triggered seismicity commonly occurs as a result of reservoir impoundment. In particular, the Nova Ponte reservoir triggered a series of earthquakes, including the 1998 M4.0 earthquake, which represents the second-largest earthquake triggered by reservoir impoundment in Brazil. The earthquake occurred after prolonged seismic activity following reservoir impoundment starting in 1993. After more than two decades, the mechanisms governing these earthquakes and their relation with the spatiotemporal evolution of the seismic events are still poorly understood. Here, we explain the causal mechanisms of the two largest earthquakes: an initial response M3.5 in 1995 and the delayed M4.0 in 1998. To this end, we numerically simulate the poromechanical subsurface response to reservoir impoundment using a 3D model that includes three geological layers down to 10 km depth. From the proposed potential nodal planes of the 1995 M3.5 earthquake, we show that the earthquake has most likely occurred on a vertical, E–W-oriented strike-slip fault with a reverse-displacement component. Deviatoric stresses generated by the water column loading on the surface, superimposed by undrained pore pressure enhancement in deep low-permeability layers can explain the fault reactivation. We find that for the 1998 M4.0 earthquake to occur, conductive flow pathways with permeability as high as 6.6·10−15 m2 should exist to transmit pore pressure to a deep critically oriented fault. Our analysis raises the importance of accounting for coupled poromechanical mechanisms controlling fault stability, hydromechanical properties of different rock layers, and realistic shape of the reservoir to accurately assess the potential for reservoir-triggered seismicity. We conclude that reliable forecasting models require accurate subsurface characterization before reservoir filling to enable managing the associated reservoir-triggered seismicity.

Numerical Simulation of Heat Transfer of Porous Rock Layers in Cold Sandy Regions

The heat transfer characteristics of porous rock layers (PRLs) have significant seasonal differences. This feature has been used to protect the permafrost subgrade under highways and railways from degeneration. However, in cold sandy environments, the transformation law of heat transfer characteristics of PRLs on account of climate warming and aeolian sand filling needs to be solved. This work developed a coupled heat transfer model for the soil–PRL system aimed at analyzing the convective heat transfer process and mechanism of a closed PRL. Furthermore, the impact of climate warming and sand filling on the cooling performance of the PRL under different mean annual air temperatures (MAATs) of −3.5, −4.5, and −5.5 °C was quantified. The numerical results indicated that the natural convection of the closed PRL occurred only in winter, and the effective convective height of the rock layer decreased with the sand-filling thickness. As the thickness of sand filling increased, the critical temperature difference for the occurrence of natural convection increased, accompanied by decreases in the Rayleigh number, the duration, and intensity of natural convection. When the sand-filling thickness exceeded 80 cm, natural convection would not occur in the PRL. Under a warming scenario of 0.052 °C·a−1, the cooling performance of the PRL could offset the adverse impact of climate warming and raise the permafrost table in the first 20 years. Moreover, the closed PRL can be more effective in permafrost regions with colder MAATs. For cold sandy permafrost zones, sand-control measures should be taken to maintain the long-term cooling performance of the PRL. This study is of great significance in guiding porous rock embankment design and road maintenance along the Qinghai–Tibetan Railway.

Experimental investigation on identification of lithologies and layered rock interface based on drilling vibration response

The rapid and accurate acquisition of lithologies and rock interfaces is an important prerequisite for guiding the development of oil gas and solid mineral resources as well as the construction of tunnel engineering. However, few studies have been conducted to identify the lithologies and rock interfaces using drilling information. The author used a drilling test platform and an integrated drilling information acquisition system to conduct drilling vibration tests on rock samples of limestone, sandstone, and coal with different lithologies and rock strengths. The test results indicated the following: 1) The drilling vibration response can characterize the properties of the lithology and rock strength and can be used as a key index to distinguish the lithologies and rock layer interface. 2) There were substantial differences in the drilling response (WOB and torque) and vibration response (vibration velocity, acceleration, and amplitude) of the single rock sample. The mean axial vibration velocities of coal, limestone, and sandstone were 5.6, 7.3, and 13.9 mm/s, respectively. The mean axial vibration accelerations were 9.2g, 32.3g, and 13.1g, respectively. The mean amplitudes of the rock surface were 402.6, 588.3, and 2003.8 μm, respectively. The mean weight on the bit was 1.3, 2.6, and 3.5 kN,1 respectively, and the mean torque was 12.3, 25.1, and 33.6 N m, respectively. 3) For the combined rock samples, the drilling and vibration responses of the layered rock interface showed an evident surge. 4) The rock strength affected the drilling and vibration responses. The stronger the rock, the higher was the drilling response (WOB and torque), higher the vibration acceleration, and lower the vibration speed and amplitude. The drilling vibration response displayed a high sensitivity to rock strength. It could effectively characterize the strength characteristics of the rock to accurately identify the lithologies and layered rock interface.

Geophysical research on the interplays between soil–rock variability and hydrogeological structures: a case study

Understanding the spatial variations in soil–rock profiles is crucial for identifying weathered rock layers and mapping geological structures, particularly in the complex feldspar-rich granitic terrain of Penang Island, Malaysia. This study employs a combination of electrical resistivity and seismic refraction tomographic techniques, along with borehole lithological data, in three distinct areas on the island. Its goal is to provide insights into surficial and subsurface soil–rock characteristics and water-bearing structures within the North Penang Pluton (including a part of the Sungai Ara axis) for sustainable groundwater development, addressing the needs of the region's growing population. The research identifies three distinct geological units at the near-surface: residual soils, highly to moderately weathered/fractured granitic layers and fresh bedrock, each with its hydrogeological properties. Promisingly, the weathered layers offer significant groundwater development potential, with deep weathered and potentially fractured zones exceeding depths of 30 m in the study area. These findings have substantial implications for sustainable groundwater development, especially in tropical hard-rock terrains. In addition, the study underscores the limitations of small geophysical spacings when probing deeper groundwater resources. This knowledge is essential for informed decision-making in water resource management and infrastructure development, addressing the ongoing global challenge of ensuring access to clean water resources amid population growth.

Searching for identity: finding the expression of place under ground

ABSTRACTCities are increasingly looking for green solutions to urban development, such as green roofs and vertical green infrastructure, as a response to globalisation and climate change. However, while engineered topsoils are being used to support green infrastructure initiatives, the hidden layers of mineral soil and rock that give landscapes their unique shape are often ignored. This research looks at the potential of subterranean soil conditions to express regional differences and challenge global trends in soil use by engaging with the underground in Aotearoa New Zealand. It finds that the uniqueness and richness of the layers of hidden soil can lead to new ways of understanding place through texture, colour, and structure, which in turn can inform aesthetic decisions and develop authentic regional aesthetics.

Impact of mining-induced seismicity on land subsidence occurrence

Mining-induced seismicity can damage buildings and surface infrastructure and cause fatalities. It is a growing concern, owing to the sudden occurrence of seismic events, lack of effective prediction capabilities, and associated consequences. In this study, we analyzed 13 high-energy mining-induced earthquakes from 2016 to 2020 in Poland's Legnica-Glogow Copper District (LGCD), based on data recorded by the Induced Seismicity-European Plate Observing System (IS-EPOS). We used European Space Agency (ESA) Sentinel-1 Copernicus satellite radar images, to study the co-seismic subsidence in the region. Additionally, we employed volumetric point source approximation and a Bayesian inverse modeling scheme to estimate the location and strength of subsurface collapses from the land subsidence data. Finally, we correlated the geological constraints with the land subsidence and earthquake source parameters. The interferometric synthetic aperture radar (InSAR) displacement maps portrayed maximum line-of-sight (LOS) displacements of −144 mm and − 124 mm in ascending and descending images, respectively, with maximum land subsidence reaching −142 mm. Notably, only a few earthquakes with large magnitudes caused land subsidence. There was a significant correlation between earthquake magnitude and land subsidence; the greater the thickness of the loose Quaternary strata, the smaller the land subsidence. According to the inversion results, the focal depths of the collapses associated with the earthquakes were 437–669 m. However, the estimated collapse depths were situated above the mining exploitation fields, within the rigid Triassic rock layers. The associated collapse energy was 1.62 times greater than the seismic energy, indicating aseismic deformation in the field. Additionally, we observed spatial discrepancy between the location of the earthquake epicenters and the maximum land subsidence. Thus, our study can improve the current understanding of the impact of mining-induced seismicity, the occurrence of associated land subsidence, and seismic mechanisms in mining areas.

Semi-automated Rock Layer Recognition from Borehole Log Data Using Combined Wavelet and Fourier Transform: A Case Study in the KG basin, India

Abstract The accurate identification of rock layer interfaces from wireline logs is one of the crucial issue of geological interpretation as we face difficulties in traditional interpretations due to the presence of various kind of high and low frequencies in the log data. Determination of rock boundaries in shallow marine sediments is very important to understand several issues related to the exploration of conventional and non-conventional hydrocarbons. Presently a combined wavelet and Fourier transform-based approach was demonstrated to discriminate the rock layers from wireline log data in Krishna-Godavari basin, which were acquired during the India National Gas Hydrate Program Expedition 02 (NGHP-Exp.-02). Initially, we selected the suitable mother wavelets and optimum level of decomposition to perform the wavelet transform by computing the error between the original log signal(s) and approximation coefficients (cA’s) of the decomposed signal(s) at several decomposition levels. Subsequently, discrete wavelet transform (DWT) of a particular decomposition level was applied to the log signals to obtain the detail coefficients (cD’s), which contain the high-frequency components of the log signals. Further, these high-frequency components of the log signals were utilized in frequency spectrum-based filtering approaches. This approach was adapted to yield information about the abrupt changes occurring in the log signals across the studied depth interval. The combined application of Fourier and wavelet transforms to shallow marine log data demonstrates that this approach is an efficient tool for delineating rock layer boundaries.

Параметры опорного давления около очистной выработки, отрабатывающей угольный пласт с непрочными породными слоями его кровли и почвы

The problem of the stressed state of a carboniferous massif containing a coal seam worked out by a working belongs to the class of flat elastically plastic problems. To construct the stress field in the marginal extremely stressed zone of the seam, the Coulomb–Mohr criteria for the transition of the seam to the limiting state, as well as the methods of bulk medium mechanics developed by V.V. Sokolovsky, were used. If the rock layers of the soil and the roof of the coal seam are not strong enough, then the limiting state occurs first in it, and then at some distance from its edge and in the layers of rocks of the massif. It occurs when the reduced stress in the rock layers reaches the value of the reduced stress in the seam corresponding to the strength limit of the layers for uniaxial compression. After that, the seam and rock layers work together. Based on the constructed stress field of the seam, the problem of the stress state of the array is reduced to the problem of elasticity theory and solved by the method of boundary elements and successive approximations. According to the results of the computational experiment, the parameters of the reference pressure of the reservoir being worked out, depending on the width of the working, were obtained. Comparative estimates are given with similar parameters when mining a seam in the soil and roof of which there are strong layers of rocks.

Aquifer hydraulic conductivity characterization by inflatable packer method in the underground coal gasification process

Underground coal gasification technology is a technology that converts coal into gaseous products through the gasification process. UCG technology is known as clean energy technology. The potential risk of UCG that can occur is groundwater contamination, this is due to gas leaking into the rock layers and the aquifer above it. An important parameter of groundwater contamination is hydraulic conductivity, obtained by the double inflatable packer method. The test results of aquifer-03 (142-151 m), the hydraulic conductivity value is 1.82 e-6 m/s - 2.16 e-6 m/s, the aquifer zone order range from the upper limit to the lower limit tends to be homogeneous in sand lithology. fine. The top layer of aquifer-04 (213-230 m), is silt lithology, the middle is silty sand lithology and the bottom is silty sand lithology. The hydraulic conductivity value is 1.22 e-6 m/s - 3.88 e-8 m/s, the range is quite wide with a difference of 2 orders, this is due to differences in grain lithological composition with finger type aquifer layers and are not interconnected. If there is a gas leak, then aquifer-03 lithology is more affected as a medium for spreading groundwater pollution than aquifer-04 lithology.

Identification of Geothermal System in Cisolok, West Java based on the Correlation of Gravity Method, ADMT (Active Directory Magnetotelluric), and Drill Log Data

Indonesia has 40% geothermal potential of the world’s geothermal potential. One proof of its potential is in Cisolok, West Java. The method used in this study is the gravity method from 2013 GGMPlus satellite with First Horizontal Derivative (FHD) analysis which is correlated with ADMT and drill log data. Based on overlaid between Land Surface Temperature (LST) map and residual anomaly map, Cisolok has a temperature of around 23.8 – 26.5 °C. These correlations describe the normal fault structure in the south that controls the Cisolok geothermal system. The results of the 3D inversion modeling show alternating layers of tuff, tuff breccia and silt as a cap rock with a density contrast of 0 – 0.2 gr/cc at a depth of 0 – 325 m, thick limestone layers with a density contrast of -0.1 – (-0.05) gr/cc at a depth of 325 – 700 m, and a layer of granodiorite rock as an intrusion body with a density contrast of -0.2 – (-0.15) gr/cc at a depth of 700 – 900 m. Based on the results obtained, it can be proven that the gravity method and the ADMT method have a fairly good correlation in geothermal exploration activities.

Earth crust of eastern segment of Ukrainian Carpathians in the regional profile RP-5 zone: structure, geodynamics, oil and gas bearing

The purpose of the work is to present widely to the scientific community and analyze in detail the structure and oil and gas bearing of the Bukovyna lithosphere (the eastern part of the Carpathian region of Ukraine) based on the unique data on the regional RWМ-CDP profile RP-5 and on the neighboring regional profiles with the involvement of other geological and geophysical data. The methodology includes a detailed comprehensive analysis of the deep structure and oil and gas bearing and oil and gas prospects of the region and its separate zones based on seismic data on the regional profile RP-5 and nearby oil and gas bearing and oil and gas prospective areas with the involvement of a complex of geological and geophysical data. Results. In the zone of the profile RP-5, the occurrence of sedimentary strata and covers of the Folded Carpathians, the Carpathian foredeep and the edge of East-European craton in the earth's crust of Bukovyna was traced in detail, including the different depth tiers of the Carpathian thrusts and folds. The stepwise dipping of the edge of the East-European craton below the Carpathians is revealed here (generally similar to other segments of the Ukrainian Carpathians). The presence here of weakly dislocated autochthonous layers of Mesozoic rocks under the Carpathian thrusts is also established. In these horizons, several bands of folds of the Carpathian extension were discovered, some of them, in particular, the Lopushna fold, are associated with discovered oil and gas deposits. The thickening of the horizons of the lower crust under the axial part of the Bukovyna Folded Carpathians was revealed. In the pre-Carpathian part of the profile, there are 2 deepped ancient "seismofocal" zones of different age of formation and different vergence (researched in detail by S.G. Slonytska using special methods), as well as a number of apophysis-like intrusions. As a result of the comprehensive analysis, the influence of the characteristic features of the local Alpine geodynamic process was traced – the Alpine/Carpathian compression of the lithosphere in the northeast direction orthogonal to the Carpathians and the corresponding thrusts of the allochthon on the previously stepwise dipped here in the southwest direction western edge of the East-European craton as a result of rift-like pre-alpine geodynamic processes. Originality. The peculiarities of the deep structure, geodynamics, seismicity and oil and gas bearing of the Bukovyna lithosphere were determined based on the data of the regional profile RP-5, taking into account new data from oil and gas exploration studies in the subregion and data on various components of the geodynamic process in the whole Carpathian region of Ukraine. The oil and gas prospects of a number of deep folds of autochthonous Mesozoic rocks in the subthrust of the Pokuttya-Bukovyna Carpathians have been predicted and confirmed. Practical significance. The research results make it possible to more clearly justify the directions of oil and gas exploration in the subregion.

Geotribometamorphism in seismic zones of the Earth’s crust

Geotribometamorphism means a process of destructive-constructive changes of the rocks in the seismotectonic zones in the Earth’s crust. Due to the friction between rock blocks and layers, kinetic energy is generated, which deforms and destroys the rocks until mylonitization and melting in an environment of high temperature and pressure. Subsequently, the disintegrated material recrystallized into new high-pressure rocks such as eclogites, garnet lherzolites, phengite and kyanite schists and calciphyres. These rocks mark paleoseismic zones and events that occurred during the Precambrian and Phanerozoic.

DEFORMATION FEATURES OF EMBEDDED MATERIALS UNDER COMPRESSION CONDITIONS

Purpose. The purpose of the article is t o study the deformation characteristics of the backfill materials made of crushed rock of different granulometric composition under compression conditions to assess the stability of the side rocks in a coal massif with preparatory workings when selecting the parameters of protective structures. Methods. Compression tests were carried out in the laboratory to model the behaviour of crushed rock fill materials under load. Cylindrical specimens were subjected to axial static compression without the possibility of lateral expansion. The results. It has been experimentally established that the maximum value of the compaction coefficient of the crushed rock kс=1.57 is achieved under conditions of compression, when the relative change in the volume of the source material is 35-36% and the relative void is 5-6%. Under such conditions, the ultimate compressibility of the deformable body is achieved at its relative deformation λ = 0.36 and the presence of particles of different sizes (diameters) in the total volume of the rock layer (before compression). At the minimum value of the compaction coefficient kс=1.14, which corresponds to the small fraction of the crushed rock, the relative change of the void is 1.5%. For a large fraction of crushed rock at kс=1.43, the relative change in voids is 6.2%. This situation is associated with the destruction of rock particles and the reduction of voids between them. Compliance with certain requirements for backfill materials made of crushed rock, taking into account its particle size distribution, increases the efficiency of using the backfill of the excavated space. It is advisable to evaluate the bearing capacity of backfill materials by the value of the compaction coefficient of crushed rock. Scientific novelty. A functional relationship between the change in the specific potential strain energy and the relative deformation of the rock layer has been established, which allows us to estimate the degree of compaction of crushed rock under compression. Practical significance. To ensure maximum compaction of the crushed rock when using partial or complete backfilling of the worked-out space used for the protection of mine workings, it is advisable to use a heterogeneous (in terms of particle size) source material. Keywords: crushed rock, backfill material, stiffness, particle size distribution, compaction, deformation, compression.

Two‐phase flow behavior in CO2 geological storage considering spatial parameter heterogeneity

AbstractSaline aquifer rocks exhibit significant spatial randomness due to geological sedimentation processes. To address the issue of the heterogeneity of rock formations in numerical simulations, it is common practice to homogenize rock layers with similar lithologies. However, the acceptability of the errors generated during homogenized computations is a major concern and should be investigated. Therefore, to study the influence of heterogeneity at the storage site on the CO2 migration behavior, the Monte Carlo simulation–random finite element method (MCS‐RFEM) was combined with a CO2 two‐phase flow model to compare the effects of the coefficient of variation (Cv) and correlation length (λx) of random reservoir permeability fields on the migration distance and extent of CO2 storage under the same mean conditions. The results showed that higher Cv and λx values significantly reduced the CO2 migration distance while increasing the spread extent. Compared to the homogeneous model, at a λx value of 100 m, the CO2 migration distance decreased by 5.05%, while the profile sweep area increased by 6.20%. Concurrently, with increasing Cv, the area with a CO2 volume fraction higher than 0.75 decreased by 20.22%, while an increase in λx resulted in a 42.35% increase in the area with a CO2 volume fraction higher than 0.75. Therefore, reservoirs with high Cv and low λx values are more suitable for safely storing CO2. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd.

Study on the influence of different rock/coal mixture ratio on thermal storage and low temperature oxidation of coal

Coal mines in the goaf are formed by the collapse and accumulation of coal rock, and the process of oxidizing and heat storage of singular coal does not reflect the real environmental conditions within the airspace. In this study, coal and rock mixing on coal spontaneous combustion (CSC) is experimentally investigated, and the bituminous coals and typical siltstones, mudstones and shales in the overlying rock layers of the goaf are selected. The different rock/coal blending ratios and real low oxygen conditions in the goaf are considered. The results show that in addition to coal, shale also contains some substances such as graphite and fixed carbon, which would participate in oxidization and heat storage processes. The thermal conductivity and thermal diffusivity of the rock/coal mixtures increased with the increase of the rock blending ratio. The heat storage capacity of the three rocks is shale > mudstone > siltstone. After blending rocks in bituminous coal, the contents of functional groups –OH, –CH3, –CH2, CC, etc. is decreased, and the degree of decrease is greater with the increase of blending ratio, and the degree of decrease of shale/coal mixture is relatively small compared with the others. As the proportion of rock in the rock/coal mixture increases, all oxidized combustion stages are delayed to varying degrees. Under the same oxygen concentration, the activation energy of rock/coal mixtures is higher than bituminous coal, and the activation energy of siltstone/coal, mudstone/coal, and shale/coal increased by 25.28 %, 20.12 %, and 14.84 %, respectively. The degree of CSC inhibition by the three rock/coal mixtures is siltstone/coal > mudstone/coal > shale/coal. The research results are of great significance to the prevention and control of CSC in the real environment of goaf.

Study on Meso-Structural Evolution of Bedrock Beneath Offshore Wind Turbine Foundation in Pressurized Seawater

In recent years, offshore wind turbine technology has been widely developed, making a significant contribution to the advancement of renewable energy. Due to the predominant subsurface geological composition characterized by rocky formations in some marine areas, rock-socketed piles are commonly applied as offshore wind turbine foundations. Generally, rock-socketed piles need to be driven into rock layers that have not undergone significant weathering or erosion for optimal load-bearing capacity. This design is essential to ensure structural support for offshore wind turbines. However, during the long-term operation period of offshore wind turbines, the contact surface between the rock-socketed pile and the rock is prone to be detached under multiple dynamic loads. The generated channel makes seawater seep into the unweathered rock layer, resulting in the erosion of rock meso-structure and deterioration of mechanical properties. The reduced load-bearing capacity will adversely affect the operation of the offshore wind turbine. In this study, the meso-structural evolution of bedrock in pressurized seawater is investigated by X-ray CT imaging using tuff samples from the marine areas of an offshore wind farm in China. A cellular automata model is proposed to predict the long-term evolutionary process of tuff meso-structure. Results indicate that the porosity of the tuff sample in the pressurized seawater shows an upward trend over time. Based on the erosion rate of pores obtained from the CT scanning test, the proposed cellular automata model can predict the evolutionary process of tuff meso-structure and corresponding failure strength of the bedrock in the long term.

Estimating Thermal Impact on Groundwater Systems from Heat Pump Technologies: A Simplified Method for High Flow Rates

This research delves into the potential thermal effects on underground water systems caused by the use of thermal technologies involving extraction and injection wells. We developed a unique approach that combines straightforward calculations with computer-based modeling to evaluate thermal impacts when water flow rates exceed 2 L/s. Our model, based on a system with two wells and a steady water flow, was used to pinpoint the area around the thermal technology where the temperature varied by more than 1 °C. Our findings suggest that the data-based relationships we derived from our model calculations provide a cautious estimate of the size of the affected area, or ‘thermal cloud’. However, it is important to note that our model’s assumptions might not fully account for the complex variables present in real-world underground water systems. This highlights a need for more research and testing. A key contribution of our study is the development of a new method to assess the thermal impact of operations involving heat pumps. In conclusion, while our proposed method needs more fine-tuning, it shows promise in estimating temperature changes within water-bearing rock layers, or aquifers. This is crucial in the effective use of thermal technologies while also ensuring the protection and sustainable management of our underground water resources.

Identification of Geothermal Potential in Block Ciasmara Sector II, Mount Salak Area, Based on the Correlation of the Active Directory Magnetotelluric (ADMT) and Self-Potential Methods

Indonesia possesses significant geothermal potential, with the largest share located in West Java, accounting for up to 21.7% distributed across 44 locations in 11 regencies. One such location with geothermal potential is in Block Ciasmara Sector II, the Mount Salak area, Bogor Regency, characterized by manifestations such as hot spring bathing pools. This research aims to understand the distribution of geothermal reservoirs in the study area, where these reservoirs contain hot fluids that can be harnessed for renewable energy generation. The methodology used in this research involves a correlation between the Active Directory Magnetotelluric (ADMT) and Self-Potential (SP) methods. A total of 3 ADMT measurements were conducted along tracks ranges from 5-8 meters, while the SP method involved 7 measurement points with coordinates distributed around the geothermal manifestations in the Mount Salak area. The data obtained were then visualized in 2D and 3D to gain insights into the distribution and orientation of the reservoir layers in the study area. The results indicate a correlation between the ADMT and Self-Potential methods. In Line 01 of the ADMT, located in the western part, there is a correlation with high potential difference values on the SP map ranges from 47.6-82.1 mV, suggesting the presence of tuff layers rich in alteration minerals. This is confirmed by the 2D ADMT modeling, which shows that the clay cap is thicker compared to Line 02 and Line 03, associated with the presence of alteration minerals in the clay cap. This correlation also applies to Line 03, which has low potential difference values ranges from 4.9-25.3 mV, indicating a response from lapilli rocks. This is corroborated by the 2D model, which reveals thickening of the lapilli rock layer on Line 03.Keywords: ADMT, Geothermal, Mount Salak, Reservoir, Self-Potential.