Salt Dome Research Articles

Monitoring Salt Domes Used for Energy Storage With Microseismicity: Insights for a Carbon‐Neutral Future

AbstractUnderground storage in geologic formations will play a key role in the energy transition by providing low‐cost storage of renewable fuels such as hydrogen. The sealing qualities of caverns leached in salt and availability of domal salt bodies make them ideal for energy storage. However, unstable boundary shear zones of anomalous friable salt can enhance internal shearing and pose a structural hazard to storage operations. Considering the indistinct nature of internal salt heterogeneities when imaged with conventional techniques such as reflection seismic surveys, we develop a method to map shear zones using seismicity patterns in the US Gulf Coast, the region with the world's largest underground crude oil emergency supply. We developed and finetuned a machine learning algorithm using tectonic and local microearthquakes. The finetuned model was applied to detect microearthquakes in a 12‐month long nodal seismic dataset from the Sorrento salt dome. Clustered microearthquake locations reveal the three‐dimensional geometry of two anomalous salt shear zones and their orientations were determined using probabilistic hypocenter imaging. The seismicity pattern, combined with borehole pressure measurements, and cavern sonar surveys, shows the spatiotemporal evolution of cavern shapes within the salt dome. We describe how shear zone seismicity contributed to a cavern well failure and gas release incident that occurred during monitoring. Our findings show that caverns placed close to shear zones are more susceptible to structural damage. We propose a non‐invasive technique for mapping hazards related to internal salt dome deformation that can be employed in high‐noise industrial settings to characterize storage facilities.

Identifying the origin, recharge, and salinity sources of the Romqan saline spring, causing intense salinization of the Shirinrud River in southern Iran

Salinization of originally freshwater rivers by saline springs is a growing threat to availability of water resources in the semiarid region of southern Iran. The problem is further complicated by persistent drought of recent years, which has resulted in prolonged periods of reduced streamflow. This issue has prompted research on possibility of finding practical techniques for flow stoppage of saline springs by investigating their recharge and salinization mechanisms as well as emergence time. To this end, the Shirinrud river in southern Iran is selected as a case study. While this river contains freshwater flow, it is intensively salinized due to annual discharge of ∼110000 tons salt from the Romqan saline spring. Study area streamflow gauges, water sampling, plus field observations and measurements have been used to provide the required data and information. Data analyses included evaluation of temperature variations of study area groundwaters, long-term salinity of the Shirinrud River, and isotopic and hydrochemical compositions of water samples. Results of thermal, isotopic, and hydrochemical tracing methods together with hydrogeological evidences in the Romqan spring site indicated that although the Romqan saline spring is recharging from a fresh groundwater flow, it becomes intensely salinized due to passage of ∼1.7 km of its recharging water pass inside the Romqan salt diapir. Furthermore, sudden drying of a freshwater spring at border of Romqan salt diapir just after the 1999 earthquake in spring site area, resulted in redirection of the fresh groundwater flow of the dried spring into the Romqan salt diapir, followed by emergence of the Romqan saline spring in the Shirinrud River bed. For flow stoppage of the Romqan saline spring, an interceptor drainage system is suggested, which would divert the spring fresh recharging groundwater flow at border of Romqan salt diapir and finally desalinize the Shirinrud River from Romqan saline spring.

Geochemical evolution of the Dead Sea brine during the last glacial cycle from chemical compositions of interstitial soluble salts

The chemical evolution of the brines that filled the Dead Sea Basin during the final phase of the last interglacial and throughout the last glacial period is constructed from the temporal variations in the Na/Cl, Mg/Cl, Br/Cl, and Br/Mg ratios of soluble salts that extracted from cores that were drilled at the modern Dead Sea floor and from sediments of the last glacial Lisan Fm. that are exposed at the high terraces above the modern Dead Sea (covering the ∼ 100–13 ka period).The main observations are: (1) Variations in the Na/Cl ratios reflect processes of halite precipitation/dissolution during arid/wet periods in the drainage basin, respectively, and exchanges between the upper and the lower brines; (2) Ions of Na + and Cl-were supplied to the brines by the dissolution of halite from the Mount Sedom salt diapir, and of halite deposits, which precipitated in the lake during the hyper-arid periods of the last interglacial; (3) The upper brine of Lake Lisan was sensitive to the hydroclimatic conditions in the lake’s drainage basin, since being directly exposed to the atmosphere, and to variations in flows of freshwater and groundwater brines, which had distinct influence on its chemical record. At the same time, the lower brine was isolated from the surroundings, by the overlying brine and received chemical inputs only by restrict mixing between the brines which buffered the intensity of regional hydro-climatic events.Temporal patterns in the Na/Cl ratios indicate that between ∼ 100–30 ka, the deep brine evolved through a moderate but steady “enrichment” by Na + and Cl-ions due to continuous dissolution of halite by the upper brine of the lake. Towards the end of this period, between ∼ 43–30 ka, the Amiaz plain, a marginal basin, comprised a semi-isolated water-body that witnessed frequent episodes of halite precipitation/dissolution with temporal patterns that resemble millennial temperature (δ18O) variations in the Greenland ice core.Between ∼ 30–18 ka (MIS 2), when Lake Lisan reached its highest stands and maximumspatialexpansion, the soluble salts from the deepest basin and from the high sections of the Lisan Fm. indicate on centennial dissolution cycles of the Mount Sedom salt diapir that took place in the upper brine and sank down to the lower brine. During the ∼ 18–14 ka decline of the lake to its low levels of the Holocene, the elemental ratios reveal several episodes of enhanced supply of freshwater to the shrinking lake, causing intensified halite dissolution and supply of Na + and Cl- ions to the deep basin, setting the grounds for massive halite precipitation, which initiated after a sharp level decline at ∼ 14 ka.The long-term (∼100–13 ka) temporal pattern in the elemental ratios of the lower brine resembles global CO2concentrations and sea surface temperature trends, while the short-term fluctuations in the upper brine are correlated with short warm/cold cycles in the Greenland ice core δ18O data, indicating a strong impact of the global climate.

Underground Hydrogen Storage: Comparison of High-pressure Hydrogen, Liquid Hydrogen, and Ammonia

One of the alternatives for effective storage of irregularly produced renewable energy is hydrogen energy. In order to realize a hydrogen-based society, not only environmentally friendly production of hydrogen but also effective storage is very important. Underground hydrogen storage technology is a technology that has evolved from the technology for storing natural gas underground, and includes waste gas fields, salt domes, aquifers, and rock cavities. When stored underground, hydrogen is converted into high-pressure gaseous hydrogen, liquefied hydrogen, and ammonia. Liquefied hydrogen requires extremely low storage temperatures, and ammonia is a toxic substance that requires separate handling, and energy loss occurs during the conversion process. To compensate for this, research on liquefied hydrogen, such as multilayer insulation technology, is being conducted. Ammonia has successfully extracted high-purity hydrogen by developing a membrane reactor. Ammonia toxicity can be prevented by strengthening leak detection and blocking facilities. Among these, ammonia was found to be the most suitable for underground storage in terms of economic feasibility, environment, and commercialization.

Salt dome identification using incremental semi-supervised learning and unsupervised learning-based label generation

Salt domes represent distinctive geological anomalies in seismic data, crucial for pinpointing hydrocarbon reservoirs and strategizing drilling paths. Conventional seismic attributes or computer vision methods usually fail to capture the intricate details of salt domes, resulting in interpretation results marred by noise. While deep learning presents a promising approach for intelligent 3D salt dome interpretation, its effectiveness is heavily dependent on the availability of labeled samples. To facilitate accurate interpretation, we propose an innovative workflow that integrates an unsupervised label generation component with an incremental semi-supervised learning framework utilizing the U-Net architecture. To generate salt dome labels, we prioritize both the root mean square (RMS) amplitude attribute and variance attribute (VA) as foundational data. Utilizing convolutional autoencoders (CAE), we establish a relationship between the input RMS attribute and the output reconstructed attribute. The intermediate features extracted by CAE are transformed into the salt boundary feature via principal component analysis and K-Means clustering. Concurrently, we employ K-Means clustering on VA to ascertain the salt internal feature. We further propose a feature aggregation method to consolidate the salt boundary feature and the salt internal feature for label generation of the salt dome. For 3D salt dome interpretation, we begin by predicting adjacent test datasets using labels generated by the unsupervised salt dome label generation module. The prediction results of these test datasets are then integrated into the training datasets to enhance the interpretation performance of U-Net, steering it towards an incremental semi-supervised learning method for salt dome interpretation. Additionally, we extend this research by applying transfer learning techniques for identifying mound-shoals using the same semi-supervised model parameters initially developed for interpreting salt domes. This method is validated using datasets from the Netherlands F3 block for salt domes and the North China block for mound-shoals. The results demonstrate that this innovative process only requires a minimal number of labels from unsupervised methods to precisely interpret salt domes across 3D seismic data. Furthermore, the low-level features of salt domes learned from neural network can be seamlessly transferred to mound-shoal identification. This automated approach significantly streamlines the interpretation process, reducing the time and resources traditionally necessary for reservoir analysis.

Shortening a mixed salt and mobile shale system: A case study from East Breaks, northwest Gulf of Mexico

The coexistence of two low-shear strength layers in a continental margin, such as salt and shales, conditions the resulting structural style and also constitutes a challenge for seismic imaging and energy resource exploration. We have analyzed the 3D structure of a mixed salt-shale system in the western Gulf of Mexico, in the East Breaks foldbelt, by interpreting a depth-migrated seismic data set. Overlying the allochthonous Sigsbee canopy and pierced by isolated salt diapirs, the Oligocene shale-prone sequences were shortened during the Miocene through pervasive deformations, developing a major suprasalt detachment system associated with duplexes below and different fold and thrust systems above. Oligocene shales locally reach a critical state and flow, resulting in: (1) inflated shale-cored detachment anticlines, with the stacking of allochthonous mobile shale domains; (2) detached lift-off anticlines with shale bulbs and fishtail thrusted welds; (3) allochthonous shale sheets at the upper tip of thrusts, fed by fluidized material migrating along associated fault zones; (4) hourglass shale diapirs; and (5) Christmas trees and vertical mud pipes connected to small mud volcanoes. The salt diapirs deformed simultaneously, as did the shales. Salt accommodated the shortening through localized subvertical welds that isolated them from the allochthonous Sigsbee canopy and through weld thrusts formed by fault-bounded blocks with highly sheared salt and mobile shales. Mobile shale structures wrap around the squeezed salt diapirs, presenting a unique pattern that has not yet been documented in experimental models with precursor salt diapirs deformed under contraction. Mixed salt-shale systems are a new challenge for structural analysis and experimental models, as well as for seismic model building in situations where there is a high dispersion of seismic energy due to the unique properties of mobile shales.

Structural evolution of the Handun salt diapir, Zagros fold and thrust belt, southern Iran

The Fars region, in the Zagros fold and thrust belt, hosts a wide range of diapirs piercing over 10 km of stratigraphic sequence. Comprising Precambrian to Early-Cambrian Hormuz Salt, these diapirs exhibit a prolonged history of evolution. Outcrop evidence for understanding the diapir deformation history is mostly limited to the Cenozoic contractive phase, and the seismic data lacks the necessary quality for an exhaustive understanding of the deepest structure's geometries. Through regional and field evidence we unravel the Handun salt structure evolution and propose a sequential restoration to describe the key deformational events. Our study presents a field-based novel regional balanced cross-section and a 3D-geological model, and addresses the role of structural inheritances and the position of the Handun diapir with respect to the decupled basement. The performed field studies describe folds and unconformities related to Cenozoic halokinetic sequences with exceptional clarity. It was possible to observe changes of the diapir activity along the structure and provide field evidence for the relative timing and kinematics of primary and secondary welding. Finally, our data suggest that the Handun diapir formed in the early Paleozoic above the shoulder of a basement extensional fault, and was partially translated above its southern hanging-wall during the shortening. In the Paleocene a sustained ratio of salt rise rate was enhanced by the Zagros/Oman contraction. In response to the Oligocene continental collision, the diapir was profusely supplied with salt, which flared upward to form overhangs. Since the middle Miocene the salt supply slowly depleted, with the diapiric walls remaining near the surface but tapering upward, probably due to primary welding or increased sedimentation. Secondary welding occurred post-Pliocene in the last stages of the diapir evolution with consequent development of a secondary minibasin.

Палеотектонический анализ отложений нижнеапшеронской литофациальной пачки Астраханского Прикаспия

The paleotectonic analysis of the Apsheron deposits of the Astrakhan Caspian Sia is considered. The main at-tention is paid to the analysis of the deposits of the lower Apsheron lithofacies unit, which includes the study of the thickness of the deposits, the construction of maps of thicknesses and trend values, as well as the analysis of the wave pattern of seismic works carried out in the territory of the Astrakhan Caspian Sia. The results of the study showed that during the Lower Apsheron time, significant tectonic processes took place in the region, including the growth of salt domes and the formation of alluvial fans. These processes had a significant impact on sedimentation and the distribution of sediment thicknesses. The conclusions about the influence of salt dome tectonics on sedimentation, as well as the role of paleorelief in the formation of local thickness anomalies are presented as well. The results obtained are important for understanding the geological history of the region and assessing its oil and gas potential. The data presented in the article are based on the analysis of geological data, including seismic data, and the use of paleotectonic analysis methods. The article describes in detail the research methods and provides examples of specific results obtained during the work.

Comprehensive Basin Analysis and Petroleum Potential Evaluation of Ayoluengo Oil Field, Basque-Cantabrian Basin, Spain

This study presents a comprehensive basin analysis and petroleum potential evaluation of the Ayoluengo oil field in the Basque-Cantabrian Basin, Spain. Using an integrated approach combining geological, geophysical, and geochemical data, we analyzed the basin's evolution and petroleum system elements. The dataset included 2D and 3D seismic data, well logs, formation tops, and geophysical maps. Our analysis revealed a complex structural framework characterized by salt diapirism and halokinetic structures. Well log interpretation and sequence stratigraphic analysis identified two genetic sequences with associated systems tracts. Four reservoir units were mapped, with the main structural traps related to salt diapirs. Seismic facies analysis highlighted high-amplitude convergent (CBH) and high- and low-amplitude convergent (CBHL) facies as the most promising for reservoir quality. The study identified one play (Jurassic) and two prospects: Lias Limestone (80% geologic chance of success) and Carniolas Dolomite (85% geologic chance of success). Volumetric calculations estimate significant hydrocarbon potential, with STOIIP (Stock Tank Oil Initially In Place) ranging from 3.4 to 4.2 x 10^16 barrels for the Lias Limestone reservoir and 1.26 to 1.56 x 10^16 barrels for the Carniolas Dolomite reservoir.

Accurate identification of salt domes using deep learning techniques: Transformers, generative artificial intelligence and liquid state machines

AbstractAcross various global regions abundant in oil and natural gas reserves, the presence of substantial sub‐surface salt deposits holds significant relevance. Accurate identification of salt domes becomes crucial for enterprises engaged in oil and gas exploration. Our research introduces a precise method for the automatic detection of salt domes, leveraging advanced deep learning architectures such as U‐net, transformers, artificial intelligence generative models and liquid state machines. In comparison with state‐of‐the‐art techniques, our model demonstrates superior performance, achieving a stable and validated intersection over the union metric, indicating high accuracy and robustness. Furthermore, the Dice similarity coefficient attaining underscores the model's proficiency in closely aligning with ground truth across diverse scenarios. This evaluation, conducted on 1000 seismic images, reveals that our proposed architecture is not only comparable but often surpasses existing segmentation models in effectiveness and reliability.

Active strike-slip faulting, diapirism and seismic hazards. The case of the Kareh Bas fault and the associated Dandenjan salt extrusion in the zagros Mountains, SW Iran

Strike-slip salt diapir systems have been scarcely investigated and have probably been underrecognized. The western Fars Arc of the Zagros Mountains hosts the most remarkable example of salt extrusions associated with seismogenic strike-slip faults within an oblique collisional setting. This study, mainly based on field mapping and observations carried out in the Kareh Bas fault system and the Dandenjan Diapir, explores several issues with practical implications related to these active fault-salt systems: (1) role of precursor diapirs on the initiation of shortening structures; (2) fault segmentation controlled by precursor diapirs, emergence of diapirs, and the development of pull-apart basins; (3) the relative timing of emergence of salt extrusions associated with a propagating strike-slip fault; (4) Quaternary deformation and paleoseismic evidence associated with the Kareh Bas fault; (5) the impact of the salt detachment depth on the seismogenic potential of the segmented Kareh Bas fault system; and (6) clustering of large potentially coseismic landslides in the vicinity of the Kareh Bas fault system.

Active and passive salt diapirs: a numerical study

Summary Salt diapirs dominate the structure in many sedimentary basins and control the preservation and migration of hydrocarbon. The formation of salt diapirs generally falls into two endmember models: active (up-building) and passive (down-building) diapirism. In the active model, salt diapirs rise from salt buoyancy to pierce through the sedimentary overburden, whereas in the passive model, salt diapirs result from differential loading of sediments during deposition. These endmember models are mostly conceptual or kinematic, the mechanics of active and passive diapirism, and their relative roles and interactions in the formation of salt diapirs, remain uncertain. Here, we use two-dimensional high-resolution numerical models to investigate the primary factors and critical conditions for active and passive diapirism. Our results indicate that it is improper to use driving mechanisms to classify salt diapirs, because the buoyancy-driven active salt diapirism involves differential loading, while the passive diapirism requires salt buoyancy. The rise of salt diapirs is more sensitive to the effective viscosity of the overburden than to the salt viscosity. Stiff overburdens could prevent the rise of salt diapirs, but they could be pierced by salt diapirs if plastic yield of the overburden is allowed. During deposition, the coupled salt-sediment deformation, driven by both salt buoyancy and differential loading of sediments, can lead to various diapiric salt structures and minibasins. Regional tectonic stress generally promotes salt diapirism by enhancing strain weakening of salts and overburdens. We suggest that the classification of active and passive salt diapirism is an oversimplification in most cases. We propose a general model of the formation of salt diapirs that usually begins with dome initiation driven by salt buoyancy, followed by syndepositional down-building controlled by sedimentation and differential loading, and ends with canopy formation when sedimentation stops.

Mixed Potential Sensors for the Detection of Hydrogen Leaks from Geologic Reservoirs

Large-scale hydrogen (H2) geologic storage presents a viable alternative to surface storage that is both safer and more economical. One option being considered by DOE is H2 storage in salt formations. These formations have been successfully used for gas storage for decades due to their extremely low permeability and may see significant investment as the US ramps up its R&D efforts in this field. New Mexico has a unique advantage in that bedded salt formations are located strategically in areas where excess energy production can be harnessed for hydrogen production. However, bedded salt is more permeable than domal salt, necessitating sensor deployment to monitor H2 containment. Robust sensors that can provide early leakage detection will be an essential component of the safety of H2 operating facilities. In a LANL-funded Mission Foundations Research (MFR) project, we prepared several zirconia-based mixed potential hydrogen sensors utilizing a tin-doped indium oxide electrode for H2 leak detection to test its stability in subsurface environments. Previous electrochemical sensor work has shown this type of sensor in a hydrogen safety sensor role represents a significant improvement over currently available sensors as it has an extremely stable baseline and limited cross sensitivity to other gaseous compounds.1 The feasibility of this technology will be demonstrated through a hydrogen permeation experiment to measure rates of underground hydrogen permeation between boreholes drilled underground at the DOE Waste Isolation Pilot Plant (WIPP) site. This experiment will (1) establish the use of this novel sensor in geologic H2 storage applications and (2) investigate the feasibility of H2 storage in bedded rock salt. Acknowledgement This research is supported by the Los Alamos National Laboratory, Laboratory Directed Research and Development (LDRD) Office, Missions Foundation Research Charter (Debora Wagner Program Manager). References E. L. Brosha, C. J. Romero, D. Poppe, T. L. Williamson, C. R. Kreller, R. Mukundan, R. S. Glass, and A. S. Wu, “Field Trials Testing of Mixed Potential Electrochemical Hydrogen Safety Sensors at Commercial California Hydrogen Filling Stations,” Journal of the Electrochemical Society 164 (13) B681-B689 (2017).

Recovering 3D salt dome by gravity data inversion using ResU-Net++

In geophysical research, gravity-based inversion is essential for identifying geologic anomalies, mapping rock structures, and extracting resources such as oil and minerals. However, traditional gravity inversion methods face challenges, such as the volumetric effects of gravity fields and the management of large complex matrices. Unsupervised learning techniques often struggle with overfitting and interpreting gravity data. This study explores the application of various U-Net-based network architectures in gravity inversion, each offering distinct challenges and advantages. Nested U-Net, although effective, requires a high parameter count, leading to extended training periods. The recurrent residual U-Net’s implicit attention mechanism restricts its dynamic adaptability, whereas the attention U-Net’s lack of residual connections raises concerns about gradient issues. This research comprehensively analyzes the training processes, core functionalities, and module distribution of these networks, including the residual U-Net++. Our synthetic studies compare these networks with traditional focused regularized gravity inversion for reconstructing density anomalies. The results demonstrate that the nested U-Net closely approximates the actual model despite some redundancy. The recurrent residual U-Net indicates an improved alignment with minimal redundancies, and the attention U-Net is effective in density prediction but encounters difficulties in areas of low density. Notably, the residual U-Net++ excels in inversion modeling, achieving the lowest misfit percentage and accurately replicating density values. In practical applications, the residual U-Net++ impressively reconstructs the F2 salt diapir in the Nordkapp Basin with well-defined boundaries that closely match seismic data interpretations. These results underscore the capabilities of the residual U-Net++ in geophysical data analysis, structural reconstruction, and inversion, demonstrating its effectiveness in simulated settings and real-world scenarios.

An automatic new approach to gravity anomaly’s profile separation, inversion and interpretation, using an infinite horizontal slab model

ABSTRACT The goal of this research is to develop a new, fast-applying, non-conventional 2D semi-inversion technique that uses data from a previously known control point (e.g. a borehole). The method successfully separated a digitised profile over the Bouguer gravity anomaly map into its components, each of which corresponded to a rock formation being prior chosen from a borehole or control point. The importance of this technique stems from its capacity to automatically analyse the shape of the Bouguer gravity anomaly, as well as its propriety, approximation and given accepted equivalent geological cross-section, utilising an infinite slab model. A preliminary synthetic guidance model (SGM) in this proposed new method is being created from borehole data to simulate the homogeneous density distribution of the rock formations that fill a hypothetical sedimentary basin so that it represents to far extent the history of the region’s sedimentation process. The theoretical gravitational effect for each rock formation is estimated using the infinite horizontal slab model for all rock formations of such a hypothetical basin model. The total of these gravitational effects is utilised to invert any gravity profile that crosses the Bouguer gravity anomaly map. The gravity anomalies of the Bouguer profile are then separated and inverted into the comparable rock formation thicknesses or/and depths tracked along the gravity’s profile using a simple method. The technique was tested on a synthetic model, a synthetic noisy contaminated model, and real data from two different field cases with different geological and lithological characteristics. The first was in the Tucson Basin in Southeast Arizona, USA, and the second on the Mors Salt Dome in North Jutland, Denmark. The method has demonstrated results comparable with prior known information of the borehole existing in the study areas.

Value of abstraction in performance assessment – When is a higher level of detail necessary?

In this study, different approaches in performance assessment (PA) of the long-term safety of a repository for radioactive waste were examined. This investigation was carried out as part of the DECOVALEX-2023 project, an international collaborative effort for research and model comparison. One specific task of the DECOVALEX-2023 project was the Salt Performance Assessment Modelling task (Salt PA), which aimed at comparing various models and methods employed in the performance assessment of deep geological repositories in salt. In the context of the Salt PA task, three distinct teams from SNL (United States), Quintessa Ltd (United Kingdom), and GRS (Germany) examined the consequences of employing different levels of abstractions when modelling the repository's geometry and implementing various features and processes, using the example of a simple hypothetical repository structure in domal salt. Each team applied their own tools: PFLOTRAN (SNL), QPAC (Quintessa) and LOPOS (GRS). These differ essentially regarding numerical concept and degree of detail in the representation of the underlying physical processes. The discussion focused on when simplifications can be appropriately applied and what consequences result from them. Furthermore, it was explored when and if a higher level of fidelity in geometry or physical processes is required.

Mechanical Properties of Rock Salt from the Kłodawa Salt Dome-A Statistical Analysis of Geomechanical Data.

Rock salt is a potential medium for underground storage of energy resources and radioactive substances due to its physical and mechanical properties, distinguishing it from other rock media. Designing storage facilities that ensure stability, tightness, and safety requires understanding the geomechanical properties of rock salt. Despite numerous research efforts on the behaviour of rock salt mass, many cases still show unfavourable phenomena occurring within it. Therefore, the formulation of strength criteria in a three-dimensional stress state and the prediction of deformation processes significantly impact the functionality of storage in salt caverns. This article presents rock salt's mechanical properties from the Kłodawa salt dome and a statistical analysis of the determined geomechanical data. The analysis is divided into individual mining fields (Fields 1-6). The analysis of numerical parameter values obtained in uniaxial compression tests for rock salt from mining Fields 1-6 indicates an average variation in their strength and deformation properties. Upon comparing the results of Young's modulus (E) with uniaxial compressive strength (UCS), its value was observed with a decrease in uniaxial compressive strength (E = 4.19968·UCS2, R-square = -0.61). The tensile strength of rock salt from mining Fields 1-6 also exhibits moderate variability. An increasing trend in tensile strength was observed with increased bulk density (σt = 0.0027697·ρ - 4.5892, r = 0.60). However, the results of triaxial tests indicated that within the entire range of normal stresses, the process of increasing maximum shear stresses occurs linearly ((σ1 - σ3)/2 = ((σ1 + σ3)/2)·0.610676 + 2.28335, r = 0.92). A linear relationship was also obtained for failure stresses as a function of radial stresses (σ1 = σ3·2.51861 + 32.9488, r = 0.73). Based on the results, the most homogeneous rock salt was from Field 2 and Field 6, while the most variable rock salt was from Field 3.

Surface displacement measurement and modeling of the Shah-Gheyb salt dome in southern Iran using InSAR and machine learning techniques

Salt domes play a crucial role in hydrocarbon storage, underground construction, solution mining, and mineralization. Therefore, deformation monitoring is essential for analyzing the kinematics and impact of salt domes. This study aims to measure the temporal displacements of the Shah-Gheyb salt dome from 2016 to 2019 and from 2020 to 2022 using the New Small Baseline Subset (NSBAS) Interferometric Synthetic Aperture Radar (InSAR) technique and to predict future displacements through machine learning models. A total of 14 data layers, including topography, remote sensing, hydrology, and geology group were used in Machine Learning (ML). Random Forest Regression (RFR) and Support Vector Regression (SVR) models were employed to project displacements in both the East-West (E-W) and Up-Down (U-D) components through 29 scenarios.In the E-W direction, the salt dome exhibits a displacement rate of 39 mm/year, while in the U-D direction, it varies between −18 and +6 mm/year. ML predictions and SAR interferometry data processing results for the period 2020–2022 were validated using Root Mean Square Error (RMSE) and the correlation coefficient (R). The RFR model demonstrated the lowest RMSE of 1.9 mm for the E-W component, achieving a maximum R-value of 97.3 %. For the U-D component, the RMSE was 2.8 mm, with an R-value of 55.8 %. Evaluation of the predictive performance of the ML models and a comparison of InSAR and ML outcomes indicated that the RFR model predicted displacement along the E-W and U-D directionsbetween 2020 and 2022 with greater accuracy than the SVR. Furthermore, comparing the displacement predictedby the RFR model using SAR interferometry along two perpendicular profiles confirmedthe model's precision.

Impact of salt diapir geometry and caprock composition on gravity survey results

With respect to difficulties seismic and magnetotellurics may have in accurate definition of exact salt diapir geometry, we performed various gravity simulations and calculations to investigate such exploration targets. Our motivation included the fact that not much has been done on caprock impact on the gravity signal. A very significant favorable condition is the high contrast of rock density between salt and basin sedimentary formations, especially carbonates. However, this can be more complicate if caprock formation is present. Therefore we defined approximate bulk density of typical caprock formation based on its usual composition, resulting in density values 2.45–2.70 g/cm3.We modelled by forward and inverse procedures the gravity signal Gz of salt diapirs with caprock of variable thickness to demonstrate to which extent the salt diapir negative gravity anomaly may be reduced by the impact of caprock formation. In the tested cases the gravity anomaly was reduced by more than 30% depending on respective caprock composition and thickness. Significant contribution to the delineation of salt diapirs themselves, as well as diapirs hidden under caprock, came from the application of horizontal gravity gradients Gzx. We showed the difference of Gzx spikes indicating the edges of density contacts according to the type of gravity survey – land or airborne. It was also proved by calculating the gravity effect of laboratory analogue models of salt deformation and extrusion.We demonstrated that gravity is still a valuable and relatively cheap tool for in-detail investigations of the salt structures within exploration projects.

Textural and mineralogical characteristics of sediments originated from salt domes in the northern part of the Hormuz Strait

Textural and mineralogical characteristics of sediments originated from salt domes in the northern part of the Hormuz Strait