Magnetic Survey Research Articles

Estimating Perspectives of Oil and Gas in New Strata in the Southern and Surrounding Dayangshu Basin

On the basis of elaborating on the regional geological background, this paper analyzes the lithological and sedimentary characteristics and explorative prospects of new strata with oil and gas in the southern and surrounding areas of Dayangshu Basin. Based on the latest high-precision airborne gravity and magnetic comprehensive survey data, combined with the latest data from geological explorations, physical surveys, and drilling, and the use of basin structure layering combination methods, we clarified the characteristics of the bottom of the Jurassic–Cretaceous and the occurrence characteristics of the Upper Paleozoic in the study area and revealed the determinative effect of multi-period structures on the most important sedimentary layers. Then, we summarized the accumulation conditions and prediction methods of hydrocarbons and proposed the oil and gas prospects of these deep new strata. The results show that the Liuhe Sag in Dayangshu Basin, the depression in the northeast of Longjiang Basin, and the northern parts of the Taikang swell have good source–reservoir–cap combination conditions and favorable structural characteristics for oil and gas, where there is a high potential for exploration.

Results of geophysical research on the Zmiyinyy island

The article presents the results of geophysical observations by the Dnepropetrovsk geophysical expedition «Dneprogeofizika» on Zmiyinyy Island, which performed a full cycle of work from prospecting and surveying studies to providing the island with drinking water.
 In structural and tectonic conditions, the island is considered as the Zmiyinyy insular block of the Danubian horst megablock. The geodynamics of the region is determined by the position and inclination of the collision sutures within the zone of interaction between the Eurasian and African lithospheric plates. Comprehensive geological and geophysical studies included magnetic prospecting, gravity prospecting and electric sounding (Dipole-axial sounding induced polarization DAS-IP) with geological routes along all rock outcrops on the Zmiyinyy island. Detailed integrated geophysical studies were: gravimetric observations over a network of 20×10 m, magnetometric — 10×5 m and electrometric (DAS-IP) — 40×5 m. For the first time on the island, gravimetric stations were set up, which will later become a support for gravimetric surveys. According to the results of magnetic field survey and DAZ-OP electrical exploration observations, an anomalous area was identified, which is perspective for archaeological research. Based on a comprehensive interpretation of geological and geophysical materials, a well was drilled to a depth of 120 m, which confirmed the constructed predictive stratigraphic section of about. Zmiyinyy. Based on the results of the search for sources of drinking water, three wells were drilled, with a fresh water flow rate of up to 10 m3 per day (each). Subsequently, fresh water with minor purification is used as drinking water.

Comparing the spatial domain and frequency domain algorithms for upward continuation of marine magnetic anomaly

Space potential field continuation is a method frequently used for the spatial transformation of magnetic anomaly in the sea area, and is the key technology for constructing three-dimensional marine magnetic field model and the application of marine magnetic survey data. In this study, we analyze the principle of upward continuation of potential field from plane to plane, demonstrate the spatial domain algorithm and frequency domain algorithm, and propose the standards for evaluating the accuracy of the two algorithms. Using the theoretical data of the multi-dipole sphere model, we employ the two algorithms to continue the magnetic anomaly of the observation plane at the height 0 m to 100 m, 200 m, and 300 m, for noisy and noise-free conditions. The results show that the continuation error of the two methods is extremely small at the plane center, but large on the edge; the spatial domain algorithm has obviously better accuracy than the frequency domain algorithm, so it should be preferentially selected in high-precision applications, such as magnetic anomaly detection in the sea area.

Magnetic constraints and susceptible inversions of Balapur Fault at central Kashmir Basin, NW Himalaya

Research subject. Subsurface investigations of the Balapur Fault at central Kashmir Basin, NW Himalaya through groundmagnetic surveys and data interpretations. Materials and methods. The total magnetic intensity data was obtained using ground magnetic surveys carried out by proton precession magnetometers at 15 m spacing. The magnetic constraints and inversions of the Balapur fault in the central Kashmir basin of NW Himalaya were analyzed. Results. The total magnetic intensity was found averaging at 97.7 with 45.8 nT as magnetic minima and 140.9 nT as magnetic maxima. The minima’s ranging from 45.8 and 55.8 nT in the gridded profile are inferred at the Balapur fault. Further, the fault-related susceptibility index was recorded from 0.0035 SI to 0.0015 SI, and the observed and predicted response values were found ranging between 67.1 to 87.7 and 67.4 to 86.6 nT respectively. Conclusion. The study suggests that the Balapur fault in the central Kashmir has produced high subsurface hydraulic activities and, therefore, evident low magnetic anomalies. The analysis reveals a thick minima region related to the fault and also indicated the presence of associated structures with the main Balapur fault segment.

New Insights into the Seamount Structure of the Northern Part of the Ninetyeast Ridge (Indian Ocean) through the Integrated Analysis of Geophysical Data

The linear Ninetyeast Ridge (NER) is the longest oceanic intraplate volcanic edifice and main feature in the Eastern Indian Ocean. Many seamounts are located on the ridge, whose origin and age remain unclear due to the lack of samples of the bedrock of which they are composed. Carbonate sedimentary caps on these seamounts prevent their direct geological sampling by dredging, therefore indirect geophysical methods are an alternative. Such integrated geophysical studies (the main methods are multibeam bathymetry and magnetic surveys) were carried out in cruise #42 of the R/V Akademik Boris Petrov in 2017 on a large seamount at the base of the NER’s western slope near 0.5° S. The collected data also includes seismic reflection data that reveal morphology, fault tectonics, depth structure, and an assumed origin of this volcanic feature. The Ninetyeast Ridge was formed by the Kerguelen plume magmatism at 50° S in the giant N-S fault. The seamount studied in cruise #42 of the R/V Akademik Boris Petrov was formed mainly to the north as a result of two-stage magmatism in a transverse strike-slip fault. The first stage (47 Ma) formed the main western part of the seamount at 20° S. The second stage (23 Ma) formed its eastern part at 8° S. The time intervals between the formation of the main massif of the Ninetyeast Ridge and the stages of subsequent magmatism that formed the western and eastern parts of the seamount are approximately 31 and 55 Ma, respectively.

Amygdala Grey Matter Volume and Face Activation Compared to Social Network Size

Amygdala volume and face activation activity have been linked to social network size. In the current study, these relationships were examined through analysis of Magnetic Resonance Imaging and survey data of 116 subjects, with a more detailed analysis of a smaller sub-sample of 20 subjects. Amygdalae structural volumes were analyzed using Freesurfer, functional activation was analyzed using Statistical Parametric Mapping, and ultra-high-resolution susceptibility-weighted images were analyzed using in-house MATLAB scripts. Mean amygdala volumes obtained in this experiment are in line with those reported in previous research. Left amygdala volume was correlated with social network scores in males, and both left and right hippocampus volume were correlated with the square root of the size of one’s social network in females. Significant correlations were also observed between left amygdala face activation levels and social network measures in the smaller sub-sample (n = 20).

Reconstruction of archaeological contexts through the integrated use of airborne LiDAR and geophysical survey: The case study of San Pietro Infine (Caserta, southern Italy)

San Pietro Infine (Caserta, southern Italy) is an archaeological area of significant historical interest as it is in the vicinity of the Roman site of Ad Flexum. Based on historical sources, the site would correspond to the junction of a road axis that, during the Roman colonization (3rd century BCE), was crossed by the Via Latina. At the intersection of these two roads, which coexisted for a time, a post station was built, most likely later replaced by an early medieval village near the religious building of S. Pietro, of which only the apse portion is preserved. However, the archaeological evidence is too scarce to allow a reliable historical reconstruction of the site and to direct any excavation work. In this paper, we present the integration of LiDAR and geophysical surveys with the aim of advancing the archaeological interpretation of the San Pietro Infine site over the-state-of-the-art while providing a cutting-edge example in archaeological investigation. In particular, LiDAR data analysis was addressed to recognize and characterize topographic micro-reliefs presumably correlated to buried archaeological structures, while subsurface geophysical prospecting, consisting of magnetic and electromagnetic surveys, was aimed at defining their possible location and extent in depth, due to the expected contrasts in the magnetic and electric properties between the targets (e.g., limestone materials, paving roads) and the host geological setting (mainly marshy deposits). The integrated study allowed us to identify a structure whose characteristics (i.e., location, shape and nature) could well match the hypothesized Ad Flexum junction. In addition, LiDAR micro-reliefs and geophysical anomalies individuate structures that, by location and extent, suggest the presence of a village developed around the religious building of San Pietro.

Гравитационные и магнитные аномалии, порождаемые сдвиговыми структурами в верхней части земной коры

The paper considers the geophysical anomalies computer modeling from the structures obtained by analog physical modeling of shear deformations. Based on the results of physical modeling of slip-strikes (performed by other authors), a generalized petrophysical model was built, and then direct tasks of gravity and magnetic surveys were solved. The features of the resulting fields are presented, which can help in the interpretation of geophysical data over structures where shear faults are developed — these are chains of anomalies of different signs extended along the general fault. The applicability of experimental geotectonics results for digital modeling of geophysical anomalies is confirmed and the corresponding methodological approach is tested.

Paleo-Asian oceanic crust trapped by irregular continental margin contributes to continental growth: Evidence from airborne gravity and magnetic imaging across the Alxa tectonic belt, Central Asia

Unsubducted, and trapped or accreted oceanic crust contributes greatly to continental growth. The Alxa tectonic belt (ATB) is located at the critical intersection of the Central Asian Orogenic Belt (CAOB) and the North China Craton. However, little attention has been paid to the influence of the evolution of the Beidashan-Langshan arcuate tectonic belt in the ATB on the closure of the Paleo-Asian Ocean, the formation of the CAOB, and the growth of continental crust. Here we report new integrated airborne gravity and magnetic surveys in the ATB that image a high-amplitude magnetic anomaly zone distributed across the Quagan Qulu ophiolite belt. The three-dimensional magnetic structure inversion reveals that the Quagan Qulu magnetic anomaly zone consists of mid-lower crustal high-value magnetic susceptibility. Gravity-magnetic forward modeling reveals that the Quagan Qulu magnetic anomaly zone may have been generated by a crustal mafic pluton characterized by high magnetism and density, approximately same to the magnetic susceptibility and density of the exposed Late Paleozoic gabbros measured in the field, which are consistent with those of the Yueyashan-Xichangjing ophiolite belt in the Beishan orogenic belt adjacent to the ATB. We argue that the mafic pluton beneath the Quagan Qulu zone may be the trapped oceanic crust derived from the Late Paleozoic-Triassic Paleo-Asian Ocean (i.e., the Quagan Qulu Ocean). In conjunction with the integrated petrologic, chronologic and geochemical observations, we argue that the Beidashan-Langshan arcuate tectonic belt dominated the differential subduction of the Paleo-Asian Ocean and finally trapped partial Quagan Qulu oceanic crust. Therefore, we propose that, in addition to oroclines, the irregular continental margins could alternatively provide tectonic space for trapping oceanic crust, contributing to the lateral growth of the continental crust and serving as an important means of continental accretion in the CAOB.

Опыт применения неинвазивных методов геофизики при решении задач археологии

На сегодняшний день в мировой практике применение неинвазивных геофизических методов при решении археологических задач является неотъемлемой частью работ на начальном этапе исследований. В статье рассматривается опыт применения малоглубинной геофизики на различных археологических объектах Наманганской, Джизакской и Сурхандарьинской областей Республики Узбекистан. Целью работ являлось изучение древних погребений курганного типа, выделение культурного слоя на местах стоянок древних людей, а также исследование построек и объектов жизнедеятельности городищ Кушанского периода территории Северной Бактрии. Исследования проводились лабораторией «Геофизики и наноминералогии» Центра передовых технологий комплексом геофизических методов, включающем в себя магниторазведку, георадиолокационную съемку и электротомографию (ЭТ). Магнитная съемка проводилась с помощью протонных магнитометров Geometrics 856АХ (США), при этом расстояние между датчиками составляло 50 см, таким образом шаг между точками измерений и профилями составлял 50 см. Георадарные измерения выполнялись георадаром PulseEKKO PRO компании Sensors & Software (Канада) по системе сеточных профилей с шагом между профилями 1 м и антенной с центральной частотой 100 МГц. При электроразведочных измерениях методом ЭТ использовался 72 электродный георезистивиметр M.A.E. X-612EM (Италия) различными расстановками с учетом глубины и размеров объекта исследований. Применение геофизических методов позволяет определять различные археологические объекты в соответствии с изучаемым физическим полем, тем самым комплексирование методов дает возможность получить объектно-направленную информацию, при этом не нарушая целостность изучаемых объектов. В результате обработки и интерпретации полевого материала были получены карты, схемы, разрезы и глубинные срезы по геофизическим данным в пределах исследованных площадок с выделением аномалий, которые могут быть связаны с археологическими объектами. Результаты проведенных раскопок, подтверждают достоверность исследований.To date, in world practice, the use of non-invasive geophysical methods in solving archaeological problems is an integral part of the work at the initial stage of research. In the article the experience of using near-surface geophysics on different archaeological sites of Namangan, Djizak and Surkhandarya regions of the Republic of Uzbekistan is considered. The aim of the work was to study ancient burials of kurgan type, to identify cultural layer at the sites of ancient people standing and to study constructions and objects of vital activity of the Kushan period sites in the territory of Northern Bactria. Researches were carried out by the laboratory “Geophysics and nanomineralogy”of the Center of Advanced Technologies by a complex of geophysical methods including magnetic surveying, georadiolocation surveying and electrotomography (ET). The magnetic survey was carried out using Geometrics 856AX proton magnetometers (USA), with a distance of 50 cm between the sensors, so the step between the measurement points and the profiles was 50 cm. GPR measurements were carried out with a PulseEKKO PRO georadar of Sensors&Software company (Canada) using a grid profile system with a step between profiles of 1 m and an antenna with a central frequency of 100 MHz. During the electrical prospecting measurements by ET method a 72-electrode M.A.E. georesistivity meter was used. X-612EM (Italy) was used with different formations taking into account depth and size of the investigation object. Application of geophysical methods allows to determine different archaeological objects in accordance with the physical field under study, thereby the combination of methods makes it possible to obtain object-directed information, while not violating the integrity of the objects under study. As a result of processing and interpretation of field material were obtained maps, diagrams, sections and depth sections on geophysical data within the investigated sites with the allocation of anomalies that may be associated with archaeological objects. The results of the excavations, confirm the reliability of the research.

Historical geomagnetic observations from Prague observatory (since 1839) and their contribution to geomagnetic research

Abstract. Shortly after the introduction of the physical unit for the magnetic field in 1832 and the invention of the bifilar apparatus in 1837, both being extraordinary scientific achievements that took place in Göttingen, the Clementinum observatory in Prague became one of the first places where systematic observations of the horizontal intensity of the geomagnetic field began. Karl Kreil was decisively responsible for this. In this paper, we focus on the very beginnings of geomagnetic observations in Prague, dating from the middle of 1839. We describe the archival materials with data that exist from that time, how the main instrument for observing magnetic storms – the bifilar magnetometer – worked and how it was calibrated, and the first magnetic survey in Bohemia. This study indicates the importance of historical geomagnetic observation materials to modern science, such as space weather research.

Geophysical architecture of tectonized volcanic bodies near flysch thrust fronts (Outer Western Carpathians)

Teschenite association rocks (TAR) represent a specific type of mostly alkaline igneous rocks which form an almost 100 km long belt of discontinuous rock bodies within the Outer Western Carpathians (OWC) in the territory of Czechia and Poland. At present, a detailed mineralogical, geochemical, and stratigraphic analysis or dating of the volcanic formations is available, but basic structural and spatial relations characterizing TAR bodies and their origin are missing due to the poor exposure of TAR and lack of borehole data. A drill-hole- and outcrop-data-calibrated geophysical survey has proven to be a powerful tool for the interpretation of spatial extent and subsurface structure of TAR. At two type localities of TAR in Czechia (sites Staré Město and Bruzovice), a geophysical investigation combining ground conductivity mapping (CM) with profile measurement of electrical resistivity tomography (ERT), gravity survey, and magnetic survey was performed. A joint interpretation of the geophysical data served to determine the spatial extent (up to 500 m long and 40 m deep), geometry, and structural features (often fault-bounded with highly anisotropic heterogeneous structure of mélange character) of the studied TAR bodies. The interpreted magmatism of the study area included a stage of intrusion and extrusion of magmatic bodies in the Early Cretaceous, followed by a phase of fold-thrust deformation during the tectonic shortening of the area from the Late Cretaceous to Oligocene times. The resulting highly anisotropic rock mass consisting of TAR and its country rocks structurally controls the subsequent post-tectonic gravity-driven deformation.

Newly Acquired Data on the Geologic Structure and Hydrocarbon Potential in the Eastern Part of the East Siberian Sea Shelf

Abstract —We report results of an integrated interpretation of geophysical data (2D CDP seismic acquisition and gravity and magnetic survey) conducted by Gazpromneft Science and Technology Center in the North Wrangel lease block on the East Siberian Sea shelf. The newly obtained geophysical data have allowed us to update the geological model of the sedimentary cover within the North Wrangel lease block, to clarify the limits of the Drem-Khed Trough, to reconstruct the conditions under which sedimentary complexes formed, and to identify possible promising oil and gas accumulation zones. We were able to determine the position of the main stratigraphic unconformities, to propose several approaches to their interpretation, and to identify the clinoform architecture of the Aptian–Albian and Cenozoic complexes within the Drem-Khed Trough. The integrated review of geological and geophysical data has been helpful in refining the framework of the main structures adjoining the trough and predicting the extent of potential reservoirs and oil and gas source rocks throughout the sedimentary cover. The Upper Cretaceous and Cenozoic complexes are regarded as oil and gas exploration targets.

Integrated approach using petrophysical, gravity, and magnetic data to evaluate the geothermal resources at the Rahat Volcanic Field, Saudi Arabia

It is necessary to develop and explore geothermal resources to achieve sustainable development and clean renewable energy around the Globe. Geothermal energy is crucial to the future energy supply to meet the environmentally friendly energy demand of the World. The Rahat Volcanic Field (Kingdom of Saudi Arabia) is the oldest and lengthiest Cenozoic Volcanic Field in the World. It is a dominantly a mature mafic Volcanic Field that holds three major geological events; the historic eruption (1256 C.E.), the five fingers (∼4500–1500 BP), and the seismic swarm (1999 C.E.). These incidents were studied by utilizing geological information and geophysical data sets. Geophysical and geostatistical research includes gravity and magnetic survey data, including different log curves and major elements, obtained from water samples as well as of volcanic rocks obtained by X-ray fluorescence (XRF). To gain an understanding of the subsurface thermal structure, these datasets were analyzed. The primary goal of this study is to identify the prominent potential geothermal resources with the help of an available data set. Findings suggest that beneath the historic eruption site along with the fissure eruption, on the western side, there is a geothermal anomaly with a surface footprint of about 35 km2. Analyzing gravity and magnetic data as well as density and magnetic susceptibility variations in rock samples led to the mapping of this anomaly. It has been inferred through integrated study that statistical analysis of major elements will be helpful to validate the results of the outcome.

Classification of UXO and non-UXO from magnetic anomaly data: a case study on inversion of drone magnetic data from Rømø, Denmark

SUMMARY A test site containing 24 targets of various disarmed unexploded ordnance (UXO) and non-UXO items were placed on a beach on the island of Rømø (Denmark) in a 600 m × 100 m area. Scalar magnetic anomalies were measured at 3–5 m altitude using an uncrewed aerial vehicle (UAV), towing a bird with a three-sensor triangular configuration to achieve a dense coverage with flight lines of 2 m spacing. The triple-sensor data set is utilized in a probabilistic inversion setup to infer the magnetic moments of the 24 targets. The purpose of the study, is to try and distinguish between different types of ferromagnetic objects (UXO, non-UXO) using magnetic anomaly data. The inversion methodology uses different forward models (prolate spheroids, rectangular prisms) to infer target shape, size and orientation in an attempt to discriminate between UXO and non-UXO items. Stochastic inversions are carried out using different prior assumptions of remanent magnetization strength (10, 50 and 80 per cent) of the induced dipole moment. Among the three levels of remanent magnetization strength in the prior, only some cases of discrimination seem evident for the lowest strength of remanence. One item is correctly classified as a true-negative (i.e. non-UXO) when assuming low remanent magnetization strength (10 per cent of the induced moment). However, at low remanent strength, one false-negative classification emerges, making any discrimination unreliable when assuming such low remanent magnetization. In addition to the discrimination study, different covariance models are utilized to optimize the inversion by addressing correlated errors and noise in the triple-sensor data set. Three covariance models are tested to try and account for spatially correlated noise and potential errors among the three sensors of each overflight. In many cases, the covariance models presented show a potential increase in sampling efficiency and consistency between data and the noise model, suggesting a more robust approach to a noise model in magnetic anomaly inversions. If the noise model is poor, however, it may bias the results by addressing the anomaly signal as noise. The inversions with correlated noise models are compared with inversions using a simple uncorrelated noise model. For several cases of data anomalies, differences between the inversion estimates when using correlated and uncorrelated noise models were evident, indicating that some bias may appear when assuming uncorrelated noise. Due to the general high presence of correlated signals in magnetic survey data, correlated noise models can significantly improve the overall uncertainty estimate of the estimated dipole moment. The study demonstrates, in terms of the 24 targets considered, that discrimination between UXO and non-UXO using magnetics is difficult. However, when using scalar magnetic data of high quality and resolution, the estimated dipole moments are often well resolved and uniquely defined in magnitude and position. This could provide valuable posterior information for future inversion studies by building a library of inferred magnetic moments from targets that have been found and inspected.

The Gondwanide deformation along the southwestern border of the Río de la Plata Craton: Geochemical and geochronological constraints on ductile shear zones from the Ventania System basement, Argentina

This work deals with the study of Gondwanide ductile shear zones developed in Neoproterozoic–middle Cambrian basement rocks of the Ventania System and possibly related to the reactivation of the Sierra de la Ventana Shear Zone. This reactivation was caused by the northeastward migration of the Gondwanide deformation from the North Patagonian Massif. The crustal shortening related to the Gondwanide Orogeny gave rise to thrusting of the Ventania System basement over Paleoproterozoic rocks of the Río de la Plata Craton. This work focuses on the study of muscovite ± quartz phyllonites of the Ventania System basement and quartz ± muscovite veins crosscutting basement and Paleozoic cover rocks of the system. Structural and magnetic surveys were performed in order to characterize the Gondwanide structures of the basement, while petrographic, X-ray diffraction, geochemical, and geochronological studies were carried out in order to investigate the nature, P-T conditions, element mobility, and age of these shear zone-related rocks. In the Sauce Chico Inlier, mylonitized basement rocks crop out along the western edge of the system, near the basement–Paleozoic cover interface, where the main structures are top-to-NNE reverse ductile shear zones with related phyllonites. Ductile shearing under greenschist-grade conditions (125–340 MPa and 300–400 °C) promoted major and trace element mobility. Phyllonites are the result of extreme hydrolysis of feldspars from the acidic igneous rocks of the basement, producing muscovite and releasing aqueous SiO2 later redeposited as quartz veins. These phyllonites developed in connection with reactivated contacts between basement units and also the basement–Paleozoic cover interface. New Rb–Sr quartz-muscovite and Ar/Ar muscovite ages for phyllonites and a quartz vein indicate a protracted tectono-metamorphic history mainly restricted to the Cisuralian (ca. 287 Ma), comprising regional folding and metamorphism, shear zone activity, vein-type mineralization, and syntectonic deposition of the Tunas Formation. Subsequent reactivations during the Lopingian (ca. 256 Ma) and probably in Late Triassic times (ca. 227 Ma) resulted from localized shearing along mylonitic belts.

Magnetization distribution and susceptibility inversions of the Balapur fault in the northern region of Kashmir basin, NW Himalaya

Ground magnetic surveys were carried out in the northern region of the Kashmir basin, NW Himalaya to calculate the total magnetic intensities and subsurface constraints at the Balapur fault. The susceptibility index of -0.020 SI to 0.001SI was found associated with the strike of the Balapur fault. Further, the susceptibility index of the associated Gulmarg fault was recorded as -0.01SI to 0.001 SI. The present study implies that the Balapur fault has produced well-developed magnetic constraints throughout its strike. The 3D inversion modeling implies that the Balapur fault in north Kashmir has developed enough subsurface strain features and can lead to high earthquake intensity. Little or no variation was found between the observed and predicted databases and the analysis recorded an accuracy factor of 0.002 with 20 iterations. The study suggests that ground magnetic surveys are very useful in understanding the subsurface fault characteristics based on the Magnetization factor.

UAV-towed scalar magnetic gradiometry: A case study in relation to iron oxide copper-gold mineralization, Nautanen (Arctic Sweden)

Scalar magnetic surveying using unmanned aerial vehicle (UAV) platforms is slowly gaining momentum within geophysical applications. So far, only a handful of studies have dealt with UAV-towed scalar field measurements, while even fewer have considered towed scalar difference measurements (or gradients). In this paper, we demonstrate the possibilities and benefits of deploying precisely positioned noise-minimized UAV-towed scalar transverse horizontal difference (THD) measurements for mineral exploration purposes. UAV-towed gradiometry bird data are presented from the Nautanen area in northern Sweden and compared with ground magnetic surveys. This area is known for its iron oxide copper-gold mineralizations. The UAV survey spans a total area of 2.5 km2. It was covered using an average line spacing of 30 m and a constant flight altitude above ground level of 30 m. High-quality scalar total-field and THD data were collected with a dynamic noise level of the raw scalar data of about ±0.05 nT. Comparison with the ground magnetic data shows a strong correlation between magnetic anomaly lows and highs across the survey areas. A map with new structural information is presented based on subtle magnetic structures identified in discrete derivatives of the total magnetic intensity anomaly and THD data. Such systems may replace high-quality heliborne systems and reduce costs of the geophysical exploration phase. However, mapping with UAV-towed systems is not straightforward. With typical UAV flight speeds of only 10–12 m/s, the wind often disturbs the 3D attitude of the bird during flights. Hence, advanced processing is required to obtain the intended gradients. Similar challenges are less important in surveying, where the survey speed often greatly exceeds the wind speed.

Excitation Circuit With Negative Feedback for a Borehole 4He Optically Pumped Sensor Based on an ELM–Hammerstein Model

Stability in the emission intensity of a spectral lamp is an essential factor determining the performance of a4He optically pumped sensor (He-OPS). However, in an He-OPS, the stability of the lamp drive signal source is greatly affected by temperature. This is a huge obstacle to its application in borehole magnetic surveys, which have harsh conditions such as a confined environment and high temperatures. Hence, a real-time control excitation circuit with proportional integral derivative (PID) feedback regulation to enhance the stability of the emission intensity is proposed in this article. The instability of the luminous intensity was first analyzed theoretically and an extreme learning machine (ELM)–Hammerstein model was established. Then, instability was regulated in real-time using a programmable PID controller. Experimental results indicate that the designed excitation circuit can work at environment temperatures up to 75 °C and magnetic drift of up to 1.3 nT is suppressed. Therefore, the excitation circuit with PID feedback regulation is an effective and reliable way to improve measurement stability and has potential for utilization in extreme environment applications such as borehole magnetic field measurement to detect resources and monitor seismic activity.

Geophysical data interpretation technologies in the study and exploration of oil-and-gas deposits

The article presents the results of scientific research on the creation of computer technology for the interpretation of geophysical field data in the exploration of oil-and-gas deposits of Ukraine. The theoretical, informational, technological and methodical foundations for increasing the efficiency of geological exploration work due to the in-depth extraction of information from geological and geophysical data based on their complex interpretation within the framework of new mathematical models have been developed. Three-dimensional gravity and magnetometric modeling can be directed to the detection of densification zones and the tracing of tectonic disturbances in the consolidated crust, without which the existence of hydrocarbon transportation channels is impossible. The practical application of examples of quantitative interpretation of three-component magnetic survey data is given, which will significantly help in the detection and localization of hydrocarbon deposits. Development and expansion of the software complex for the interpretation of magnetotelluric data based on the use of impedance-type boundary conditions. The technique is intended for visualization of MTS data at the stage of qualitative interpretation in parallel with the method of the impedance tensor and Wiese vectors. The absolute advantage of this approach is its independence from the condition of a plane incident wave and the use of all six components of the electromagnetic field (including the Z component of the electric component of the MT field). The integration of statistical and deterministic methods during the inversion of geophysical data will increase the re-liability of the obtained geological results. The relevance and importance of the results presented in the work is determined by the conceptual novelty of methods and tools for forecasting new promising areas, as well as the reassessment of reserves of known deposits.