Rafael M. Magalhães, Thiago J. Machado, Moisés D. Santos
et al.
Abstract Optimizing strategies in the Oil and Gas Industry, particularly within reservoir engineering and management, remains a significant challenge due to the prohibitive computational time costs and high resource demands of current simulation methods, even for medium-sized reservoirs. Notably, existing scientific approaches have not leveraged Deep Neural Networks (DNNs) for fine-grained predictions at the grid-cell level. This thesis introduces a novel approach that integrates DNNs with a Design of Experiments framework to develop a proxy model for reservoir simulation software. The methodology includes a robust feature selection process, model design, and training strategy, supplemented by comprehensive statistical evaluations and graphical tools. The proposed proxy models are validated using four distinct industrial scenarios based on the SPE9 black oil benchmark, incorporating production and injection wells across diverse temporal samples. The results demonstrate a significant improvement in computational efficiency without compromising accuracy, achieving over 80% accuracy across all scenarios, and reaching up to 99.9% under specific conditions. These findings highlight the potential of DNN-based proxy models to transform reservoir management practices, offering a scalable and resource-efficient alternative to traditional numerical simulations.
This study investigated the pedogenesis, nutrient availability and toxic element contamination in soil developed over the Kopili shale in Garampani area of Dima Hasao District, Assam, India using geochemistry. Examining soil formation over shale, this research addresses environmental risks of toxic elements, the sustainability of agricultural practices, and the development of soil management strategies. Soil samples collected from pits and trenches were analyzed for major oxide, trace and Rare Earth Element (REE) geochemistry and examined using Pearsons’ correlation coefficient, Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA). The soil has a Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW) and Index of Compositional Variation (ICV) values of 87.40 ± 0.37, 97.96 ± 0.07 and 0.86 ± 0.49, respectively, indicating intense chemical weathering. Mineralogy was dominated by quartz and kaolinite, with notable enrichment in TiO₂, Fe₂O₃, Vanadium (V) and Arsenic (As), while CaO, Na₂O, MgO, Sr, Cu, Mo and Ba were depleted. PCA revealed that soil chemistry is governed entirely by geogenic factors, with no evidence of anthropogenic inputs. Acidic leaching, weathering of heavy minerals and precipitation of iron hydroxides contribute to the overall chemical profile of the soil. Pedogenesis occurs under hot and humid conditions, driven by physical, chemical and biogenic processes. The loss of macro- and micronutrients and high Fe₂O₃, which can potentially hinder nutrient uptake in plants, reduces soil fertility, while elevated As (17.5–145.7 ppm) and V (191–391 ppm) levels pose health risks. The study highlights that in soil with low pH, the concentration of macro-nutrients decreases while toxic elements, such as As increase. Poor soil fertility drives shifting jhum cultivation, contributing to forest loss and increasing landslide risks. Additionally, elevated As levels in the soil significantly contribute to groundwater As contamination in Northeast India.
Abstract This study addresses the critical challenge of incomplete downhole drilling tool attitude data in rotary steerable drilling systems, a significant issue impacting drilling trajectory control, efficiency, and safety. Attitude data loss often occurs due to sensor malfunctions, communication errors, and harsh drilling environments, posing risks to accurate geological modeling and decision-making. Traditional interpolation methods struggle with the nonlinear, time-dependent nature of drilling data, resulting in poor accuracy and reliability. To overcome these limitations, a Long Short-Term Memory (LSTM) model, a type of deep learning algorithm known for capturing complex time-series dependencies, is proposed for data completion. This model was trained and validated using a dataset collected from a rotary steerable system laboratory test platform, including acceleration, magnetic flux, and Hall sensor pulse signals under varying inclination and rotational speeds. Experimental results show that the LSTM model achieves superior performance, with a coefficient of determination (R2) exceeding 0.95 and significantly lower mean squared errors compared to Fully Connected Neural Networks (R2 = 0.88) and other regression-based methods. The completed attitude data closely replicates original signal trends, accurately reconstructing gravitational acceleration, magnetic flux, and TICK signals despite noise and data loss. This work goes beyond previous studies by applying deep learning specifically to downhole drilling tool attitude data completion, a novel approach not previously explored in petroleum exploration literature. The demonstrated accuracy and robustness of the LSTM model provide a reliable, data-driven solution for enhancing drilling path optimization, reducing non-productive time, and minimizing operational risks. This research contributes a scalable method to improve drilling efficiency and resource recovery rates, with potential applicability to broader data-driven drilling automation systems.
Rita Mwendia Njeru, Akhmad Sofyan, Matthias Halisch
et al.
In the context of global efforts to transition toward renewable energy and reduce greenhouse gas emissions, geothermal energy is increasingly recognized as a viable and sustainable option. This paper presents a comprehensive assessment derived from a subset of a larger sample collection within the Dunántúli Group of the Pannonian Basin, Hungary, focusing on optimizing micro-computed tomography (µ-CT) resolution for analyzing pore structures in sandstone formations. By categorizing samples based on geological properties and selecting representatives from each group, the study integrates helium porosity and gas permeability measurements with µ-CT imaging at various resolutions (5 µm, 2 µm, and 1 µm). The findings reveal that µ-CT resolution significantly affects the discernibility and characterization of pore structures. Finer resolutions (2 µm and 1 µm) effectively uncovered interconnected pore networks in medium- to coarse-grained sandstones, suggesting favorable properties for geothermal applications. In contrast, fine-grained samples showed limitations in geothermal applicability at higher resolutions due to their compact nature and minimal pore connectivity, which could not be confidently imaged at 1 µm. Additionally, this study acknowledges the challenges in delineating the boundaries within the Dunántúli Group formations, which adds a layer of complexity to the characterization process. The research highlights the importance of aligning µ-CT findings with geological backgrounds and laboratory measurements for accurate pore structure interpretation in heterogeneous formations. By contributing vital petrophysical data for the Dunántúli Group and the Pannonian Basin, this study provides key insights for selecting appropriate µ-CT imaging resolutions to advance sustainable geothermal energy strategies in the region. The outcomes of this research form the basis for future studies aimed at developing experimental setups to investigate physical clogging and enhance geothermal exploitation methods, crucial for the sustainable development of geothermal resources in the Pannonian Basin.
Abstract There are limited comparative studies on modeling fluid transport in fractured porous media. Hence, this paper systematically compares the steady-state creeping flow Stokes–Brinkman and Darcy–Darcy models for computational efficiency and accuracy. Sensitivity analyses were also conducted on the effect of fracture orientations, fracture sizes, mesh resolution, and fractures with Local Grid Refinement (LGR) under the FEniCS computational framework. Both models were validated numerically, and the accuracy of their solution is compared using the R-squared metric and L2 norm estimates. Key results showed that both models have similar pressure and velocity field solutions for a given fracture orientation. The computational time required for solving the Stokes–Brinkman models for a single fracture case was unusually lower than that of the Darcy–Darcy model when the pressure and velocity terms in the Darcy–Darcy model were solved simultaneously using two equations, contrary to where only one equation solves for the pressure and the velocity is obtained by projecting the gradient of pressure onto a vector space. The Stokes–Brinkman model is more sensitive to mesh resolution, and as a result, the Darcy–Darcy model tends to be more accurate than the Stokes–Brinkman model at low resolutions. Local Grid Refinement (LGR) can improve the Stokes–Brinkman model's accuracy at low mesh resolution. Furthermore, both models showed similar results when compared for complex fracture systems such as multiple fracture cases: interconnecting and isolated fractured porous media systems under low-velocity and steady-state creeping flow conditions. The FEniCS code in this paper is shared for future researchers to reproduce results or extend the research work.
The Eocene Kopili Formation in the Assam foreland basin records sediment sources, tectonic activity and depositional environments following the India-Eurasia collision. Mineralogical and geochemical analysis of these shales exposed near Garampani, Assam, NE India was conducted to study the diagenesis, palaeoweathering, palaeosalinity, redox conditions, tectonic settings and provenance. The Kopili Formation is composed of mainly shale with thin beds of limestone, black shale and sandstone and these units overlie the Upper Sylhet Limestone. The presence of goethite-rich phosphatic nodules, secondary precipitation within the fissile planes of shale and the occurrence of anatase, talc, smectite and chlorite suggest diagenesis. The prevalence of kaolinite and mean Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), Al2O3/MgO and Rb/Sr values of 86.73, 97.26, 16.36 and 1.32, respectively indicates extensive source rock weathering in humid tropical climate. The Index of Compositional Variation (ICV) values ranging between 0.47 and 2.38 also signify high weathering and tectonically active basin. The Sr/Ba ratio 0.34 ± 0.27 (mean±2σ) suggest overall freshwater basin. The Ni/Co (2.84 ± 2.29), V/Cr (1.65 ± 0.45) and Ce/Ce∗ (0.97 ± 0.63) suggest fluctuating redox environment. The samples predominantly cluster in continental island arc domain on the Th-Sc-Zr/10, La-Th-Sc and Th-Co-Zr/10 discriminant diagrams. Elemental ratios of Th/Sc, La/Sc, Cr/Th with average 0.91, 3.18, 10.13 respectively and La/Th-Hf plot suggest a felsic source rock. The Kopili shale was deposited in freshwater, continental island arc basin with fluctuating redox conditions, receiving sediments from weathered Himalayan granites and gneisses under a warm and humid climate. Subsequently, they underwent diagenetic alteration by low-pH fluid(s).
Slađana Popović, Danijela Vidaković, Zlatko Levkov
et al.
Research of cave-dwelling diatoms is lacking. In these extreme environments, diatoms are restricted to illuminated zones, and are found at the entrance zone and in the lampenflora community. However, the number of identified species is constantly increasing, and new species are being discovered. The genus Luticola is one of the most widely studied genera worldwide and many representatives are characterized as aerophilous and are found in terrestrial habitats. For the first time, Luticola species identified from phototrophic subaerial biofilms of 10 caves in Serbia (cave entrances and lampenflora) based on detailed light microscopy (LM) and scanning electron microscopy (SEM) observations were summarized and discussed. In total 11 representatives of the genus were identified at the species level, and morphological features of Luticola acidoclinata, L. angusta, L. frequentissima, L. dismutica, L. nivalis, L. triundulata, and L. quinquenodis were characterized in detail. For Luticola angusta, electron microscopy images are shown for the first time. Additionally, four new taxa (L. angusta, L. frequentissima, L. kopanjae, and L. poulickovae) were recorded for the diatom flora of Serbia. The study fills an important gap regarding the occurrence and characteristics of Luticola representatives in subaerial habitats.
Abstract Fluid wave code communication is used in layered water injection intelligent monitoring system, but model of fluid transient flow wave signal transmission is still unknown. Based on the fluid energy equation of steady flow, a transmission mathematical model of fluid transient flow wave signal in intelligent layered water injection system was established. The model can accurately describe the transient flow wave transmission characteristics in the tubular string of water injection wells. The transient flow wave signals and influencing factors generated by the ground electric control valve and the downhole water distributor were studied, and the transmission mechanism of the signal in the water injection tubular string was revealed. Studies show that ground and downhole transient flow wave signals are generated by discharge changes caused by changes in the opening degree of the ground valve and the downhole water distributor. The length of the water injection tube has no effect on the downlink transmission of the wellhead signal, but has a certain influence on the uploading of the downhole signal. Numerical calculations show that the flow rate of the water injection tube has a great influence on the amplitude of the pressure signal. The larger flow rate can generate larger signal amplitude, which is beneficial to the signal transmission, signal detection and processing. It was verified by the experiments and simulations that the pressure and flow changes in the downhole and wellhead had good consistency during the transmission of transient flow waves. It is found that the greater the variation of opening degree, the greater the amplitude of transient flow wave signal, which is beneficial to the wave signal transmission. The optimal settings for the valve opening are selected as $$100\% \rightleftarrows 0\%$$ 100 % ⇄ 0 % . This study has theoretical guiding significance for the design and performance improvement of fluid wave code communication systems.
The sandstone composition of foreland basin has a wide range of provenance signatures, reflecting the interplay between flexed underplate region and abrupt growth of the accreted upper plate region. The combination of contrasting detrital signatures reflects these dual plate interactions; indeed, several cases figure out that the earliest history of older foreland basin infilling is marked by quartz-rich sandstones, with cratonal or continental-block provenance of the flexed underplate flanks. As upper plate margin grows over the underplate, the nascent fold-and-thrust belt starts to be the main producer of grain particles, reflecting the space/time dependent progressive unroofing of the subjacent orogenic source terranes. The latter geodynamic processes are mainly reflected in the nature of sandstone compositions that become more lithic fragment-rich and feldspar-rich as the fold-thrust belt involves the progressive deepest portions of upper plate crustal terranes. In this context sandstone signatures reflect quartzolithic to quartzofeldspathic compositions.
<p>Diverse types of bricks from monuments in the city of
Padua (northeastern Italy) were studied using a multi-analytical approach
based on spectrophotometry, X-ray fluorescence (XRF), X-ray powder
diffraction (XRPD), polarized-light optical microscopy (POM) and/or
high-resolution scanning electron microscopy with coupled energy-dispersive X-ray spectroscopy (HRSEM-EDS). The most
representative bricks were yellow or beige and in well-preserved condition.
The results showed that they were made of Mg- and Ca-rich illitic clays,
were fired at high temperatures (from 900 to over 950 <span class="inline-formula"><sup>∘</sup></span>C), and
achieved an incipient vitrification. Two main processes took place during
firing: (i) the development of a Ca-aluminosilicate amorphous phase where
very abundant pyroxene-type crystals were nucleated and (ii) the
transformation of the pristine Mg-rich clayey grains into Mg-silicate
mineral phases. The analyses suggest a firing dynamic within a highly
reactive and supersaturated unstable system, particularly rich in calcium
and magnesium. There are also signs of the rapid heating and/or soaking of
the bricks and the irregular heat distribution and/or different residence
times inside the kilns. The formation of zeolite and calcite secondary
phases was also observed. The former was largely promoted by the high
calcium content of the bodies and the very humid conditions, while the
latter was mainly precipitated from Ca-rich solutions. The preservation of
the bricks was enhanced by processes that took place both during and after
firing. Firstly, the significant development of a Ca-rich amorphous phase
and of high-temperature pyroxene-type crystals has provided strength to
the bricks. Secondly, the porosity yielded by the firing of the
carbonate-rich clays was almost filled by secondary calcite, which acted as
a cementing agent. The information attained has increased the knowledge of
(i) the mineralogical and microstructural changes that take place during the
firing over 900 <span class="inline-formula"><sup>∘</sup></span>C of Ca- and Mg-rich illitic clays and (ii) the
formation of secondary phases within highly calcareous bricks laid in very
humid environments and affected by Ca-rich solutions. The key role of the
Ca- and Mg-rich raw clays and of the high firing temperatures, in producing
high-quality bricks, and of the secondary calcite, which increased their
durability, is highlighted. All these factors have contributed to the better
preservation of the built heritage of the city.</p>
Abstract In order to improve the validity of bottom hole pressure model, and simplify its calculation process, a mathematical model of instantaneous pressure for unsteady flow was established by considering the crossflow between the fractures and matrix. Different conditions, including the reservoir top has constant pressure, were considered. The basis for obtaining bottom hole pressure is to solve diffusivity equation with the integration of axisymmetric transformation and similar methods, which is presented for the first time. Different from the traditional method of using the Green’s function and source solution, this paper uses Laplace transformation, axisymmetric transformation and similar methods, separation of variables to obtain the analytical solution of Laplace domain. Then, the Stephenson Numerical method was used to obtain the numerical solution in a real domain. The results of this method agree with the numerical simulations and actual test data, suggesting the validity and accuracy of this method. Finally, the sensitivity analysis revealed that the pressure curve can be divided into eight stages, namely, early linear flow, continuous flow transition section, fracture linear flow, formation linear flow, crossflow, transitional flow, pseudo-radial flow and boundary control flow. The advantage of the analytical solution utilized in this paper is to incorporate exchange coefficient and skin factor efficiently, providing a theoretical basis for optimizing production pressure difference and determining the reasonable productivity.
Для верификации представлений о неотектонических и современных напряжениях Сахалина анализируются структурно-геоморфологические признаки напряженного состояния этого региона, обнаруженные в ходе полевых работ 2019–2020 гг. Наряду с новыми полевыми замерами структурно-геоморфологическим методом представлены данные о деформации земной коры на основе GPS/ГЛОНАСС-измерений. Приводятся данные геофизических исследований (сейсмологических и скважинных методов). Подтверждено выделение трех типов областей с различной геодинамической обстановкой растяжения, сжатия и чистого сдвига. Отмечены вариации современного поля напряжений на границах областей с различной геодинамической обстановкой формирования новейших разломов. Северный Сахалин имеет специфические направления осей сжатия неотектонических напряжений, выраженные в северо-восточных ориентировках, в отличие от преобладающих субширотных ориентировок на всем острове. Проведенные исследования показали, что на юге Сахалина граница между Амурской и Охотской микроплитами проходит, скорее, по Западно-Сахалинскому, а не по Центрально-Сахалинскому разлому.
Abstract The increasing energy demand has to be met while we transitioned to a decarbonized energy future. Heavy oil and bitumen reserves are urgently needed to be developed to ensure that a smooth transition is provided. In this work, field-scale kinetics parameters are used to study the effect of reservoir pay thickness on the performance of toe-to-heel air injection (THAI) process. Air was injected at constant rate into three different models with the thicknesses of 24 m, 16 m, and 8 m, respectively. The oil produced is slightly affected by the reservoir thickness. It is found that the lower the reservoir thickness, the larger the cumulative air-to-oil ratio (cAOR), indicating that heat loss increases with the decrease in the reservoir thickness. This trend is similar to steam-based processes. At constant air injection flux, it is found that both the cumulative oil produced and the cAOR decrease with the decrease in the reservoir thicknesses. This decrease is attributed to the decrease in the rate of heat generation in the thinner reservoirs, which in turn results in lower combustion zone temperature and thus lower temperature gradients between the reservoir and the overburden and the reservoir and the underburden. Consequently, a more general conclusion is that decreasing the air injection rate by the same factor the reservoir thickness is decreased (i.e. keeping the air injection flux constant) results in a more economical THAI process operation compared to when the air injection rate is kept constant (i.e. allowing increase in air injection flux).
Shams Kalam, Teslim Olayiwola, Mohammed M. Al-Rubaii
et al.
Abstract Carbon dioxide has gradually found widespread usage in the field of science and engineering while various efforts have focused on ways to combat the menace resulting from the release of this compound in the atmosphere. A major approach to combating this release is by storage in various geological formations ranging from depleted reservoir types such as saline aquifers to other carbon sinks. In this research study, we reviewed the experimental, modeling, and field studies related to the underground storage of CO2. A considerable amount of research has been conducted in simulating and modeling CO2 sequestration in the subsurface. This review highlights some of the latest contributions. Additionally, the impact of CO2 sequestration on its surroundings due to chemical reactions, adsorption, capillarity, hysteresis, and wettability were reviewed. Some major challenges associated with CO2 injection have also been highlighted. Finally, this work presents a brief history of selected field scale projects such as Sleipner, Weyburn, In Salah, Otway Basin, Snøhvit, Alberta, Boundary Dam, Cranfield, and Ketzin. Thus, this study provides a guide of the CO2 storage process from the perspectives of experimental, modelling, and existing field studies.
Abstract A bimetallic nickel–molybdenum catalyst supported on γ-alumina was synthesized by the two-step incipient wetness impregnation technique. The activity of the prepared Ni–Mo/γ-alumina catalyst was evaluated in a down flow fixed-bed micro-reactor. In this way, hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions of the main distillate fractions of crude oil were assessed. XRD, SEM, TPR, ICP-OES, BET–BJH and nitrogen adsorption/desorption methods were used for characterizing the synthesized Ni–Mo/γ-alumina catalyst. The active metals with Ni/Mo mass ratio of 0.23 and total metal of 13.7 wt% were loaded on the support, similar to the commercial industrial catalyst. The performance tests were conducted at 3.0 MPa (for light naphtha and heavy naphtha) and at 4.5 MPa (for kerosene and gas oil). The results revealed that the total sulfur conversion of the light naphtha, heavy naphtha, kerosene and gas oil fractions was 98.3%, 95%, 91.7% and 90.1% (after 24 h), respectively.
Jon Errandonea-Martin, Fernando Sarrionandia, Josu Junguitu
et al.
The Sierra Bermeja Pluton (∼60 km2 surface area) exemplifies a type of controversial granites of the Iberian Massif (European Variscan Belt), the cordierite-bearing ‘Serie Mixta’ (mixed series) monzogranites. The pluton is included almost completely in the Cornalvo Natural Park (Badajoz, Spain), a relevant target area in Roman times. The geological mapping summarised in the presented map at 1:10,000 scale has revealed a complex intrusive assemblage. Three main cordierite-bearing monzogranite types that show local varieties constitute most of the massif. Monzogranite intrusions are younger towards the centre of the pluton and gave rise to outstanding mappable mingling/mixing zones in some areas. A NE–SW trending reduced dyke complex composed by vaugnerite series rocks, lamprophyres, aplites and quartz dykes, completes the lithological assemblage of the pluton. An inventory of Geologic Points of Interest to promote the geological knowledge of this remarkable protected area and its geoconservation is also presented.
Abstract The stability of petroleum coke water slurry (PCWS) is currently a hot topic. The inherent relationship between yield stress and stability of bubble-PCWS was studied through orthogonal experiments and range analysis in this work. The results showed that the stability of bubble-PCWS was positively related to the yield stress and that the yield stress could be greatly impacted by the operation conditions during preparation of bubble-PCWS. The main factors affecting the yield stress of bubble-PCWS were solid concentration, aeration time and dosage of frother. However, the effects of aperture size of air distribution plates and type of frother on the yield stress were slight within the experimental range. The optimal conditions for the greatest yield stress were as follows: aeration time of 30 min, solid concentration of 65 wt%, frother dosage of 0.030 wt% of the air-dried pulverized petroleum coke, aperture size of air distribution plate of 2–5 μm and AOS frother. The yield stress and the pour rate of bubble-PCWS under this optimum operation condition could reach maxima of more than 0.4 Pa and 96%, respectively.
Abstract The ability of a novel nonionic CO2-soluble surfactant to propagate foam in porous media was compared with that of a conventional anionic surfactant (aqueous soluble only) through core floods with Berea sandstone cores. Both simultaneous and alternating injections have been tested. The novel foam outperforms the conventional one with respect to faster foam propagation and higher desaturation rate. Furthermore, the novel injection strategy, CO2 continuous injection with dissolved CO2-soluble surfactant, has been tested in the laboratory. Strong foam presented without delay. It is the first time the measured surfactant properties have been used to model foam transport on a field scale to extend our findings with the presence of gravity segregation. Different injection strategies have been tested under both constant rate and pressure constraints. It was showed that novel foam outperforms the conventional one in every scenario with much higher sweep efficiency and injectivity as well as more even pressure redistribution. Also, for this novel foam, it is not necessary that constant pressure injection is better, which has been concluded in previous literature for conventional foam. Furthermore, the novel injection strategy, CO2 continuous injection with dissolved CO2-soluble surfactant, gave the best performance, which could lower the injection and water treatment cost.