Geological Bodies Research Articles

Characteristics and Connectivity Analysis of Hidden Karst in Jurong Pumped Storage Power Station Area, China

Based on the hidden karst exposed in Jurong Pumped Storage Power Station, combined with the field exploration data, the temporal and spatial development characteristics of hidden karst in the power station area are analyzed using the methods of specific solubility and specific corrosion, water chemical composition analysis, borehole television imaging, tracer test, and water pressure test. The results show that the karst development in the study area can be divided into three periods: pre-Cretaceous, Pleistocene, and modern karst. Karst development is controlled by soluble rock, non-soluble rock, and their combination, and the development direction is basically consistent with the fault strike. Karst caves are mainly distributed below the elevation of 100 m, with different shapes and scales and randomness. Non-soluble rocks and impure carbonate rocks are widely distributed in the study area, and surface karst is not developed. The underground karst caves are filled with red clay, and the rate of groundwater circulation is slow. The existence of geological bodies such as rock veins causes the groundwater levels to have obvious double-layer characteristics, which results in weak connectivity between karst caves. Although the karst in the power station area has a certain hydraulic connection with the surface water outside the area, the hydraulic connection of karst in the power station area is generally weak. The research results provide a scientific basis for the anti-seepage measures of underground powerhouses.

A Facies Proportional Determination Method Based on the Theory of Confidence Intervals: A Case Study in the M Gas Field in the East China Sea

A reservoir is the space and gathering place of underground oil and gas reservoirs. Lithofacies proportion is the key parameter of a reservoir. Due to the heterogeneity of geological bodies, the multi-solution of seismic data and the limited and uneven distribution of logging data, it is unclear how to determine the lithofacies proportion in the study area directly from the available data. The mean is a way to make a quick estimate, but the mean cannot quantify the uncertainty of the lithofacies proportion using the available data. In this paper, a new method for quantifying uncertainty and determining the value of the three levels of the facies proportion is proposed. Taking sandstone proportion as an example, a normality test was carried out to verify the applicability of the sandstone proportion data to this method, and then the mean and variance of samples were calculated. Based on the confidence interval theory, the uncertainty of the mean value and the range of sandstone proportion were determined, that is, the optimistic value and the pessimistic value of the sandstone proportion. The results show that this method provides a new reference for quantifying values for the three levels of the uncertainty, and it uses the petrographic proportion as an example to provide the data basis for subsequent modeling and reservoir research.

Crystallization blockage damage in tunnel drainage system and suggestions for its prevention and control

The functionality of drainage systems in highway tunnels is of paramount importance for the structural safety and efficient operation of the tunnels. This study investigated the operation, management and maintenance of tunnels on Renxin Expressway and Yinghuai Expressway in Guangdong Province, and conducts tunnel disease statistics and analyzes the types of tunnel diseases under different geological bodies, and proposes prevention and control suggestions. The results showed that (1) water leakage at the linings and construction joints accounted for over 90% of all pathological conditions, (2) water samples collected from the sites had an alkaline pH level greater than 7, with 74% of samples exceeding 9, and (3) the dominant components of the crystalline substances collected from the sites were calcite and aragonite (CaCO3 crystals), accounting for 97% of the total. Based on the field investigation and data analysis, this paper presents many effective measures to control crystalline blockages for tunnels’ drainage systems.

Metallogeny and exploration indicators of Sn and Ag deposits in the Southern Great Xing'an Range, China: Application of knowledge-driven CoDA based on geology and geochemistry

There have been recent breakthroughs in exploration for tin (Sn) and silver (Ag) mineral resources in the Southern Great Xing'an Range, making this region a world-class Sn and Ag metallogenic area. However, thick surface coverage and hidden deposits make exploration difficult, and conventional geological and geochemical prospecting methods have severely limited efficacy. In order to further extract geological and geochemical information on the basis of the existing research, to serve the regional mineral exploration, the knowledge-driven CoDA method is used to identify geochemical associations for inferring matallogenic information. Meanwhile, the fractal C-A model is used to determine geochemical anomalies, the catchment basin geochemical method is used to delineate anomaly boundary. Especially, the data-driven CoDA method is employed for comparison analysis with the knowledge-driven one. As a result, seven groups of compositional balances are proposed and verified, and geological bodies closely related to Sn and Ag mineralization are identified. These occurred in Dashizhai Formation strata, being calcareous rocks and granites, especially A-type granite, which is most closely related to mineralization. Meanwhile, Sn and Ag mineralization areas were identified and found to be consistent with known deposits. Finally, this paper proposes a novel model of regional porphyry Sn–Cu metallogenic systems and delineates exploration targets for Ag–Zn–Pb–Cu deposits and Sn–polymetallic deposits based on the analysis of catchment basins.

High-precision computational modeling of soil-rock mixtures considering realistic shape of rock blocks

Soil-rock mixtures (SRMs) are heterogeneous geological bodies with complex spatial structures and peculiar mechanical properties. This paper proposes a high-precision computational modeling method to realistically simulate the shape of rock blocks in the SRMs as well as the mesostructure of SRMs. The precise control theory of the rock blocks is first described. Then, acceleration measures such as bounding volume hierarchies and position culling are introduced to increase the computational efficiency while retaining the model accuracy. Practical examples and comparisons with the existing methods are provided to demonstrate the advantageous features of this method. In the end, the modeling method is successfully integrated into the DEM platform to create engineering models involved in SRMs, which lays the foundation for further DEM analysis to understand the effects of the mesostructure on the mechanical properties of SRMs.

Multiple-Point Geostatistical Simulation of Nonstationary Sedimentary Facies Models Based on Fuzzy Rough Sets and Spatial-Feature Method

Summary 3D simulation of sedimentary facies using seismic data is vital for reservoir evaluation and estimation of oil and gas reserves. As a result of the high nonstationarity of sedimentary facies and the highly nonlinear characteristics of seismic attributes, the mapping relationship with sedimentary facies has certain ambiguities and uncertainties that affect the modeling results of sedimentary facies. Multipoint geostatistics (MPS) has proven to be an effective technique for modeling subsurface geological bodies. However, the conventional MPS only deals with stationary applications, and its capability of revealing the distribution of sedimentary facies is thereby limited. In addition, the task of seismic attributes selection, which significantly affects the performance of the modeling method in simulating the distribution of sedimentary facies, is difficult because the relationship between sedimentary facies and seismic attributes is complex. This article presents a nonstationary modeling method for simulating the distribution of sedimentary facies, which is featured by the multiscale spatial feature of patterns. In particular, the spatial location of the patterns is introduced as auxiliary information in the classification and simulation processes. The method incorporates multiscale results during the modeling procedure. Patterns from the multicategory training images (TIs) are classified by the optimized workflow. The seismic attribute selection is achieved by using fuzzy-rough sets. The proposed simulation method is verified by two typical TIs, followed by applications to predict the actual distribution of sedimentary facies. Compared with the filter-based pattern simulation (FILTERSIM) approach, the proposed simulation method is applicable for revealing detailed subsurface models, especially under complex geological conditions and limited information.

A new Bayesian-based brittleness prediction method for the Pingdiquan formation in the Eastern Shiqiantan depression of the East Junggar Basin

This paper presents a novel Bayesian-based method for predicting brittleness. The method involves synthesizing petrophysical data from multiple well cores to establish a joint Gaussian distribution function for shale facies and non-shale facies. Furthermore, Bayesian facies classification is applied to seismic data. The proposed method combines non-shale facies data with Rickman brittleness data to obtain a new brittleness index. The joint Gaussian distribution function and Bayesian classification are utilized to enhance the differentiation of brittleness among different geological bodies. Practical data analysis demonstrates that the new brittleness index effectively increases the contrast in brittleness values between various geological bodies, highlighting target areas of interest. The presented method offers a promising approach for brittleness prediction, leveraging the integration of petrophysical and seismic data through Bayesian techniques. The results suggest its potential applicability in enhancing the characterization and understanding of geological formations.

In-situ stress analysis in the Chang 7 reservoir of northern Shannxi region

The Shaanbei Chang 7 shale oil reservoir in the Ordos Basin develops vertically with multiple lithologic superimpositions. The interlayer stress of sand-mud-shale thin interbeds is different, and the stress within the small layer is variable, resulting in high hydraulic pressure fractures and short extension distances. The effective retrofit volume did not meet expectations. Based on the in-situ stress of key layers tested by the Kaiser in-situ stress test, the in-situ stress distribution law of vertical multi-interbedded layers with different lithologies was obtained by finely interpreting the single-well in-situ stress logging results, combined with the geological, structural and sedimentary characteristics of the block, established a three-dimensional in-situ stress regional model of complex lithologic reservoirs based on fine geological bodies, simulated the regional in-situ stress distribution law of sand-mud-shale multi-thin interbedded lithology, and mastered the geological The spatial lateral and vertical differences of the stress field. The calculation results show that the overall three-dimensional stress of the block is σV>σH>σh, the maximum principal stress range of the longitudinal upper interlayer is 35∼58 MPa, the minimum principal stress range is 28∼55 MPa, and the horizontal stress difference range is 6∼8 MPa, the stress value of sandstone in the lateral upper layer is greater than that of shale and that of mudstone, and the difference of horizontal stress in the vertical direction increases with the increase of depth. By analyzing the in-situ stress distribution of different interlayer depths and bedding lithologies, it provides parameter guidance for the fracturing design of complex lithologic reservoirs in the Chang 7 Member in northern Shaanxi, Ordos Basin.

Controlling factors for oil production in continental shales: A case study of Cretaceous Qingshankou Formation in Songliao Basin

Continental shale oil is widely distributed in the Cretaceous Qingshankou Formation of the Songliao Basin in Northeast China. In the Qijia-Gulong sag and the Changling sag in the Songliao Basin, breakthroughs of shale oil exploration and development have been made in the first and second members of the Qingshankou Formation, and several wells represented by Well GYYP1 have achieved high and stable shale oil production. However, some horizontal wells in shale oil development pilot test (Well groups A and D) were characterized by low shale oil production, high flowback rate and rapid production decline. Therefore, controlling factors of the shale oil production were investigated. The results show that shale oil enrichment area and optimal sweet spots are fundamental for high shale oil production, improving horizontal length and drilling ratio of sweet spots is a technical guarantee for enhancing shale oil production of single well, and artificial fracture network (incl. scale, complexity, and coupling with pre-existing geological bodies) created by fracturing is a direct factor for controlling the shale oil production. For subsequent exploration and development of the shale oil, the heterogeneity of sweet spot distribution should be carefully considered, the shale oil enrichment areas and optimal sweet spots also need be optimized, and the wellbore trajectory control and fine geological modeling techniques should be figured out. Moreover, the fracturing techniques suitable for the shale with high clay mineral content and weak brittleness should be developed, and the personalized and differentiated staged fracturing also needs to be performed, to effectively enhance single-well shale oil production and estimated ultimate recovery.

Original visual imaging in Marsili’s (1658–1730) geology and mapping

Bologna was the birth place of the word Geology by Aldrovandi (1522–1605) in 1603, and of visual imaging of geologic outcrops and landscape by Marsili’s (1658–1730) works, having forerunner in Leonardo (1452–1519). Wide use of visual graphics and imaging characterizes Marsili’s geologic production, under the influence of a tradition beginning with Aldrovandi and peaking with Malpighi’s (1628–1694) teaching and anatomical works, ending in detailed drawings, as done also by Malpighi’s friend Steno (1638–1686), a (re)founder of geology. Marsili’s early visual geologic representations, such as the gypsum structures in the quarries and caves of the Bologna hills (1698), the profiles across the Swiss Alps (1705), the subterranean bedding and an early geological map in the Romagna sulphur mines (1717–1718) show his intent to. dissect geological bodies observed through Europe, as he was thought by Malpighi to do with human bodies. Such original aesthetic scientific design in geology grew in Marsili’s maturity far beyond Steno’s teaching, as shown in Marsili’s major treatises on Danube and oceanography and in his monumental archive, at the Bologna Institute.Marsili’s cartographic skill is highlighted by his manuscript Oreographic Map of Europe, which is the first example of structural map at continental level, as shown by physical connections across seas and alluvial plains of major European mountain belts: Donets through Volga Heights to Karelid chains and Cola Peninsula, Harz Mountains to Norvegian chain, Pyrenees to Provencal chain, Balkan chain to Crimea and Caucasus chain, Bethic to Rif chain (Gibraltar arc), Sicily Apennine to Maghrebian chain, Apulia to Hellenic belt. Relevance of the selected case histories demonstrate that this is not a geographic but a geological map by which Marsili aimed at unravel subsurface structures and trends.

2D Inversion of DC Resistivity Method to Detect High-resistivity Targets inside Dams

As the first barrier of flood control, the integrity and continuity of dams are of the utmost importance. However, with the influence of natural weathering, running water erosion, and humanistic factors, various degrees of damage are prone to occur inside and outside dams. Therefore, it is necessary to detect the integrity of dams and evaluate their flood control capacity. Different from the previous detection of water-filled imperfect areas, we used numerical simulation and measured data analysis and considered the influence of actual noise to conduct DC resistivity detection and 2D inversion research on the high-resistivity imperfect areas existing in dams. The research results show that both the calculated apparent resistivity and the resistivity obtained by 2D inversion deviate from the real resistivity of the dam. A dam with a height less than 5 m has a relatively small influence on the 2D inversion results of the DC resistivity method, and the inversion results can accurately show the spatial information of the high-resistivity imperfect areas. The distance between the river and dam has a major influence on the inversion results, but the influence on the inversion results can be ignored when the distance is greater than 20 m in the model of this paper. The 2D inversion of the DC resistivity method can be used to detect high-resistivity imperfect areas of dams, and the 2D spatial information of the 3D geological bodies can be accurately obtained.

Comparison of short-offset and long-offset grounded-wire transient electromagnetic responses based on the 3D model

In this study, a recently developed time-domain electromagnetic method called the short-offset grounded-wire transient electromagnetic (SOTEM) method, which is a near-source observation method, was adopted to obtain strong signals and great detection depths. The responses of the SOTEM and long-offset transient electromagnetic (LOTEM) methods were compared to further guide and promote the SOTEM method. Currently, the comparison between SOTEM and LOTEM methods is primarily based on one-dimensional (1D) models. However, most geological bodies are three-dimensional (3D) structures. We investigated the responses of a grounded-wire transient electromagnetic method based on 3D models using the 3D finite-difference time-domain method. In addition, the signal strengths, detection sensitivities and detection depths of the SOTEM and LOTEM methods were compared. The results revealed that the field amplitudes of Ex (electrical component parallel to the transmitting source) and ∂By/∂t (magnetic component perpendicular to the transmitting source horizontally) were higher at the short offsets than at the long offsets. For the ∂Bx/∂t (magnetic component parallel to the transmitting source) and the vertical magnetic component ∂Bz/∂t, at initial times, the responses received would be stronger when closer to the transmitting source, whereas at later times, the responses would be stronger when farther from the source. Ex detection sensitivity increased with an increase in the offset at initial times, and increased with a decrease in the offset at later times. The detection sensitivities of the three magnetic field components at short offsets were higher than those at long offsets. The ∂By/∂t effective detection depth was the greatest. Generally, the effective detection depths of the three magnetic field components increased with decreasing offset. The range of the ratio of the horizontal distance, r, between the transmitting source and the target body to the effective detection depth H was 0.5-1.1.

Application of Aeromagnetic Data Analysis and Interpretations to Investigate Solid Mineral Potential in Part of Bauchi, Northeast Nigeria

Abstract: The distribution of surface and subsurface magnetic materials within the study area, the delineation of geologic lineaments, and an estimate of the depth to magnetic sources were all determined by interpreting high resolution aeromagnetic data that covered a portion of Bauchi, northeastern Nigeria, lying between Latitudes 9040'00"N to 10010'0"N and Longitudes 900'0"E to 9040'0'E. The Aeromagnetic map, analytical signal, and horizontal derivative filters used on total magnetic intensity data after reduction to the magnetic equator (RTE) show that the Toro and its environs contain highly magnetic minerals thought to be potential deposits of iron ore. The lithological map and the lineament maps have a good connection. Further examination of the findings reveals that the research area has varying degrees of Ferro-, para-, and diamagnetic mineralization (of the iron and non-iron varieties). The geological source bodies are thought to be located between 177.389 and 991.626 meters deep, according to the Euler depth solution. This shows that during the orogenic process, a sequence of strong deformations were present alongside the Toro.

Automated identification and mapping of geological folds in cross sections

Abstract Cross sections carry information on the spatial distribution of rock strata and the development of geological structures, and it is an important data source for three-dimensional (3D) geological modeling. However, the interpretation and mapping of geological structures in sections by means of manual interpretation are inefficient and costly, and the performance varies greatly with the experts’ ability and experience. The objective of this article is to develop an automatic recognition and mapping method for folds in cross sections. This method mainly includes identifying folds based on stratigraphic sequence characteristics (symmetrical and repetitive), classifying fold types based on geometric attributes of folds (interval scheduling, strike, and section morphology), optimizing strata based on the superposition principle and area conservation principle, and constructing the polygon features of folds. Based on experiments in the Parallel Fold Belt of Eastern Sichuan and the central Appalachian fold-thrust belt in the Appalachian Mountains, the method presented in this article can effectively be used for automatic recognition and high-quality mapping of folds in the cross sections. The method provides a good source of geological cross-sectional data for the 3D modeling of geologic bodies.

Seismic Facies Recognition of Ultra-Deep Carbonate Rocks Based on Convolutional Neural Network

Seismic facies is a seismic reflection unit defined by specific seismic reflection characteristics, that is, the seismic responses of sedimentary facies or geological bodies, whose accuracy will directly affect the reliability of oil and gas exploration results. Currently, seismic facies is generally recognized depending upon the differences between certain single trace seismic attributes (waveform, frequency spectrum, and amplitude, etc.) and adjacent units to conduct cluster analysis. Such methods, however, have ambiguity in identifying special reflective structures with continuous waveforms (e.g. massive carbonate deposits). In order to solve this problem, this paper incorporates artificial intelligence (AI) technology into automatic recognition of seismic facies with special reflection structures. Firstly, a 2D seismic facies classification sample label set is designed and formed. Then, a seismic facies prediction model is designed and constructed using a multi-layer convolutional neural network (CNN). Finally, the trained model is used to automatically track the seismic facies in the study area. This method was applied to seismic facies recognition for the Sinian Dengying Formation in an area of the Sichuan Basin, and the seismic facies recognized were compared with artificially interpreted ones. It is confirmed that the proposed method provides a better effect than artificial interpretation, with greatly improved accuracy and efficiency.

Mapping structural lineaments using the edge filters of the potential field: a case study of the Rizhao–Lianyungang area, East China

Background: Edge enhancement plays an important role in potential field data processing and interpretation, which facilitate regional tectonic studies, mineral and energy exploration. This is because edges on potential field often indicate linear geological structures such as fractures, edges of geological bodies and so on. With the development of meticulous edge enhancement on potential field, the phenomenon of false edges caused by the associated anomalies when detect ing edges from magnetic field cannot be ignored.Methods: Aiming at this problem, we proposes a modified magnetic edge detection method (SP Mag) based on the second order spectral moment. This method has been tested on both synthetic and field data. The synthetic test show that SP Mag cannot only balanced edges no matter from strong or weak anomalies, but also eliminates those false edges caused by the associated anomalies in magnetic field, which provide more effective information for subsequent interpretation.Results: We apply this new method to the RTP aero magnetic field and gravity field of Rizhao Lianyungang area. The lineaments recognized by the SP Mag method correspond well with geologic structures through comparing with geological maps.Discussion: The results illustrate the usefulness of the method for potential field interpretation. Furthermore, more geological and geophysical data should be still combined for comprehensive interpretation in the actual interpretation, though the SP Mag method can recognize lineaments effectively.

Inversion of potential fields by interactive optimization of 3D subsurface models using a spring-based space warping and evolution strategy

The rapid development of dynamic data-integrative modeling of geologic processes and subsurface structures is an important factor for the sustainable utilization of natural resources. One of the current gaps in data-integrative modeling is the interactive construction of realistic 3D models of the earth’s underground. We have developed here a methodology of 3D interactive processing of potential fields — gravity and magnetics — as well as their potentials and derivatives, combining forward and inverse modeling. Forward computations are based on the approximation of geologic subsurface structures by polyhedra with triangulated surfaces. Inverse computations for the model geometry are performed by means of the covariance matrix adaptation evolution strategy (CMA-ES), which is proved to be efficient in the case of a strongly nonlinear problem and high-dimensional parameter space, as in potential field models. The main disadvantage is related to triangulation, as certain algorithmic constraints must be applied during the approximation of geologic body shapes. To avoid topology distortions, we use a concept of warping the space containing the model, rather than the model itself. However, the optimized lengths of grid sides are dependent on each other, which degrades the self-adaptation of the CMA-ES. The elegant solution is to introduce a system of virtual elastic springs connecting the grid nodes. We develop a numerical formulation of this system and provide a proof of the concept rather than an overview of the theoretical concepts of the inversion schemes. The new workflow is tested on the 3D SEG Advanced Modeling Program model and applied to a real case study of salt dome modeling in the Northwest German Basin. In the context of the inversion procedure described here, we determine how an interpreter can visually control and influence the quality of the inversion on a timeline.

Simulation Experiment Study on Impacting the δD Value of Aromatic Compounds

Little is known about the effects of sedimentary environment and maturity on δD values of aromatic compounds deposited in geological bodies. Our simulation experiments showed that the δD value of pyrolytic polycyclic aromatic hydrocarbons (PAHs) was significantly different between the studied samples from high and low latitude regions. Comparative studies showed that the δD values of PAHs produced by pyrolysis were related to those of water in the two regions. With increasing maturity, the δD value of the PAHs becomes higher. Additionally, it was observed that some PAHs exhibited a propensity to increase the δD value upon demethylation. The thermodynamic fractionation of hydrogen isotopes between the PAHs produced by pyrolysis and both the n-alkanes and methane produced by pyrolysis indicated that the hydrogen isotopic value of the PAHs was higher than that of the n-alkanes or methane. The long-chain alkylbenzene produced by pyrolysis has a higher mean δD value compared with the n-alkanes produced by pyrolysis, but it is lower than that of the PAHs in the same sample. The lowest δD value among the aromatics was found in the ring A monoaromatic steroids produced by pyrolysis. The low δD values of these steroids should originate from isotopic fractionation during isoprenoid lipid biosynthesis.

Research on Scale Improvement of Geochemical Exploration Based on Remote Sensing Image Fusion

Both remote sensing and geochemical exploration technologies are effective tools for detecting target objects. Although information on anomalous geochemical elemental abundances differs in terms of professional attributes from remote sensing data, both are based on geological bodies or phenomena on the Earth’s surface. Therefore, exploring the use of remote sensing data with high spatial resolution to improve the accuracy of small-scale geochemical data, and fusing them to obtain large-scale geochemical layers could provide new data for geological and mineral exploration through inversion. This study provides a method of fusing remote sensing images with small-scale geochemical data based on a linear regression model that improves the resolution of geochemical elemental layers and provides reference data for mineral exploration in areas lacking large-scale geochemical data. In the Xianshuigou area of Northwest China, a fusion study was conducted using 200,000 geochemical and remote sensing data. The method provides fused large-scale regional chemical data in well-exposed areas where large-scale geochemical data are lacking and could provide potential data sources for regional mineral exploration.

Zircon as a pathfinder for ore exploration

Despite its wide application in dating geological events like magmatism, diagenesis, and metamorphic processes, zircon morphological, geochronological, and geochemical implications in ore systems have hitherto received little attention. In this study, we used textural, chemical, and isotopic data of zircons from variable granite-related deposits and other deposit types to emphasize zircon robustness as a pathfinder for ore exploration. The results show that zircons from W–Sn-related granites are rich in U, P, Ti, Y, Nb, Ta, Pb, Hf, Th, and REE compared to Cu–Mo-related granite. For the vein-type deposits, ore-bearing veins have significant zircons captured from geological bodies through which ore-forming fluid originated and migrated (e.g., basement rocks), whereas ore-free veins possess fewer zircons and are mostly from country rocks. Finally, in skarn-type deposits, ore-bearing skarns have zircons from granitic rocks and country rocks, whereas ore-free skarns have zircons only from one end member, either from granitic rocks or from country rocks. The variability in zircon abundance in these deposit types results from differences in the degree of magmatic differentiation of granitic rocks, variable zircon incorporation processes during veining and degree of contact-metasomatism during skarnization. We proposed a series of diagrams and employed partial least square discrimination analysis (PLS-DA) to differentiate the metallogenetic potential of granite-related, vein-type, and skarn-type deposits. The zircon criteria summarized by this study can be applied to similar ore deposits worldwide, which are significant for exploring economic minerals.