Core Analysis Research Articles

Delayed environmental pollution caused by transient landscape storage - An example from the Lesser Antilles.

The strong pest pressure on intensive banana cultivation in the French West Indies led to the intensive use of chlordecone (an organochlorine insecticide) between 1972 and 1993. Due to its high toxicity for the population and the environment, many studies were conducted on the transfer of chlordecone over the last 20 years. However, most studies focused on the dissolved fraction of chlordecone, while the particle-bound fraction was understudied. Therefore, this study reconstructs pluri-decadal erosion rates (i.e. 1980-2023) and associated chlordecone particle-bound transfers from soil and sediment cores sampled in a cultivated headwater catchment (Saint-Esprit, Martinique). Based on sediment accumulation analysis in an agricultural reservoir, high erosion rates (i.e. 10 t ha-1 yr-1) were found in the investigated catchment during the study period, with values exceeding the estimated tolerable soil loss rate in tropical context (i.e. 2.2 t ha-1 yr-1). Based on the analysis of soil cores sampled along a banana plantation hillslope, this study highlights the formation of colluvial deposits with high levels of chlordecone contamination. When these areas are affected by erosion processes, this leads to massive remobilization of particle-bound chlordecone to water bodies. Indeed, in sediment sampled in the downstream reservoir, we observed a drastic increase in these transfers since 2006, synchronous with changes in agricultural practices. This study therefore highlighted the occurrence of legacy contamination at toeslope positions, which was estimated to potentially persist for 4000 to 11,000 years. Such a residence time highlights the need to implement changes in land management to effectively reduce agricultural soils erosion, particularly in areas identified as "temporary deposition zones" for chlordecone contamination, in order to protect downstream water bodies from chlordecone transfer. To achieve this, agricultural practices that may increase soil erosion, such as herbicide application or intensive ploughing, should be minimized. Overall, this study improved our understanding of erosion and associated chlordecone transfers in tropical environments.

CoralCT: A platform for transparent and collaborative analyses of growth parameters in coral skeletal cores

AbstractWe present CoralCT, a software application for analysis of annual extension, density, and calcification in coral skeletal cores. CoralCT can be used to analyze computed tomography (CT) scans or X‐ray images of skeletal cores through a process in which observers interact with images of a core to define the locations of annual density bands. The application streamlines this process by organizing the observer‐defined banding patterns and automatically measuring growth parameters. Analyses can be conducted in two or three dimensions, and observers have the option to utilize an automatic band‐detection feature. CoralCT is linked to a server that stores the raw CT and X‐ray image data, as well as output growth rate data for hundreds of cores. Overall, this server‐based system enables broad collaborations on coral core analysis with standardized methods and—crucially—creates a pathway for implementing multiobserver analysis. We assess the method by comparing multiple techniques for measuring annual extension and density, including a corallite‐tracing approach, medical imaging software, two‐dimensional vs. three‐dimensional analyses, and between multiple observers. We recommend that CoralCT be used not only as a measurement tool but also as a platform for data archiving and conducting open, collaborative science.

Novel Variant of New Delhi Metallo-Beta-Lactamase (blaNDM-60) Discovered in a Clinical Strain of Escherichia coli from the United Arab Emirates: An Emerging Challenge in Antimicrobial Resistance

Background/Objectives: Carbapenem resistance poses a significant health threat. This study reports the first detection and characterization of a novel variant of New Delhi metallo-β-lactamase (blaNDM-60) in Escherichia coli from the United Arab Emirates (UAE), including its genetic context and relationship to global strains. Methods: NDM-60-producing E. coli was isolated from a rectal swab during routine screening. Characterization involved whole-genome sequencing, antimicrobial susceptibility testing, and comparative genomic analysis with 66 known NDM variants. Core genome analysis was performed against 42 global E. coli strains, including the single other reported NDM-60-positive isolate. Results: The strain demonstrated extensive drug resistance, including resistance to novel β-lactam/β-lactamase inhibitor combinations, notably taniborbactam. NDM-60 differs from the closely related NDM-5 by a single amino acid substitution (Asp202Asn) and two amino acid substitutions (Val88Leu and Met154Leu) compared to NDM-1. NDM-60 is located on a nonconjugative IncX3 plasmid. The strain belongs to sequence type 940 (ST940). Phylogenetic analysis revealed high diversity among the global ST940 strains, which carry a plethora of resistance genes and originated from humans, animals, and the environment from diverse geographic locations. Conclusions: NDM-60 emergence in the UAE represents a significant evolution in carbapenemase diversity. Its presence on a nonconjugative plasmid may limit spread; however, its extensive resistance profile is concerning. Further studies are needed to determine the prevalence, dissemination, and clinical impact of NDM-60. NDM evolution underscores the ongoing challenge in managing antimicrobial resistance and the critical importance of vigilant molecular surveillance. It also highlights the pressing demand to discover new antibiotics to fight resistant bacteria.

Coupled simulation for pin-wise reactor core analysis using subchannel analysis code CUPID and fuel performance code GIFT

Recent efforts to develop high-fidelity, multi-physics safety analysis methodologies aim to assess realistic safety margins. However, they remain conservative using initial conditions based on the hot rod with maximum power for the whole reactor core. This study presents the development and verification of a coupled code for pin-wise reactor core analysis using the subchannel analysis code CUPID and the fuel performance code GIFT. The goal was to generate accurate pin-wise fuel rod conditions during normal operation for safety analysis. CUPID was applied for thermal–hydraulic analysis considering fuel behavior, and GIFT was extended to multiple fuel rods. The coupled code was verified for a single assembly to examine subchannel geometry deformation, followed by a practical simulation for a quarter reactor core during the first cycle. Key parameters for safety analysis were examined, revealing that maximum stored energy occurred in a specific fuel rod rather than the hot rod with maximum power.

Deformation of the void space of pores and fractures of carbonates: comprehensive analysis of core and field data

Deformation of the void space of pores and fractures of carbonates: comprehensive analysis of core and field data

The learning strategy for biodiversity concept: Pedagogical analysis based on technological pedagogical and content knowledge

Sustainable Development Goals (SDGs) emphasize quality education and environmental protection. Biodiversity education in Phase E requires students to solve problems related to biodiversity. However, complex terminology and limited learning tools create challenges. This research aims to analyze effective learning strategies for teaching biodiversity using a TPACK framework. The method used in this research is a literature review carried out systematically by PRISMA. The analysis will map pedagogical approaches, content based on CoRes analysis, and technological aspects. Findings will inform the development of effective learning strategies for high school biodiversity education, contributing to achieving SDGs, particularly SDG 15 on terrestrial ecosystems. The finding shows that The use of CoRes to narrow down the information is required to instruct students and promote the attainment of the 15th SDG goal. Based on the findings of the analysis, the pedagogical review of the approach used, namely local wisdom, the field trip method, and the discovery learning model, as well as the use of technology to assist students in identifying PlantNet, Picture This, and iNaturalist, is considered effective to be implemented in learning biodiversity material.

Otolith chemistry reveals painted notie (Nototheniops larseni) juvenile stocks differed between southern Bransfield Strait and South Georgia shelf

The painted notie Nototheniops larseni is a link between the lower and upper levels of food web as one of the most abundant and widespread fish species in the Southern Ocean. Otolith chemistry is a well-established approach for studying fish life histories and differentiating stock structure, and chemical analysis of otolith core can be used to distinguish fish stocks. This study demonstrates that the N. larseni juvenile stocks in the southern Bransfield Strait are sourced from the same environment, but the stocks in the southern Bransfield Strait and at South Georgia shelf are separated geographically using chemical data from otolith core, hatching and feeding checks, and edge. The ratios of 7Li to 42Ca across otolith sections of N. larseni juveniles in the southern Bransfield Strait are lower significantly than those at the South Georgia shelf, indicating the Li in fish otolith may act as a chemical tag for reflecting sea ice dynamics in the Southern Ocean.

Late holocene vegetation succession and climate change in the Central Plains of China: Evidence from a high-resolution pollen record

Changes in the East Asian summer monsoon precipitation will have a significant impact on China’s politics, economy, and social development. To explore the controls and drivers of the Late Holocene (∼3350–2560 cal. yr. BP) vegetation succession and East Asian summer monsoon precipitation changes in the Central Plains of China, we conducted pollen analysis of the Pu Tian core collected from Zhengzhou, China. The results showed three periods of vegetation and East Asian summer monsoon variation: coniferous and broad-leaved mixed forest between ∼3350–3025 cal. yr. BP, increasing forest vegetation dominated by broadleaf Betula between ∼3025–2930 cal. yr. BP, decreasing forest vegetation and increasing herbaceous plants dominated by Artemisia and Poaceae between ∼2930–2560 cal. yr. BP. Weighted Averaging Partial Least Squares Regression was used to quantitatively reconstruct the average annual precipitation variation in the Central Plains of China. Our precipitation reconstruction and its comparison to other reconstructions and forcing show that it was influenced by internal (intertropical convergence zone and El Niño-Southern Oscillation) and external (Northern Hemisphere Summer Insolation) forcing. Specifically, average annual precipitation decreased significantly between ∼2980–2680 cal. yr. BP, and tree pollen (such as Betula) also decreased significantly during this period, possibly related to the “2.8 ka” event (a weak monsoon event in the Holocene). Our comparison of the published climate and environmental records of the East Asian monsoon region suggests that the 2.8 ka event exhibiting a “W” structure of “dry-wet-dry” and may have been caused by the weakening of solar activity, which affected the climate of the East Asian monsoon region through oceanic and terrestrial atmospheric circulation such as El Niño-Southern Oscillation.

Oral azacitidine maintenance after intensive chemotherapy versus venetoclax and azacitidine: real world outcomes in newly diagnosed acute myeloid leukemia

Oral azacitidine (Oral-AZA) is recommended as maintenance therapy for patients with newly diagnosed acute myeloid leukemia (ND AML) achieving remission with intensive chemotherapy (IC) but not transplant candidates; venetoclax plus injectable azacitidine (VEN-AZA) is recommended for patients ineligible for IC. Some patients may be considered candidates for either regimen. This retrospective study used Flatiron Health’s database to compare treatment patterns and clinical outcomes with Oral-AZA maintenance after IC (IC🡪Oral-AZA) versus frontline VEN-AZA. Relapse-free survival (RFS) and overall survival (OS) were analyzed at 4 different time points, including from Oral-AZA initiation (IC🡪Oral-AZA cohort) or from remission (VEN-AZA cohort) in the Core Analysis. Median RFS was 14.9 and 8.1 months for IC🡪Oral-AZA and VEN-AZA propensity score-matched cohorts, in the Core Analysis (n = 32 in each; p = 0.027); median OS was 18.7 and 15.2 months (p = 0.034). In patients with AML, IC🡪Oral-AZA significantly improved RFS and OS compared with VEN-AZA.

Technical note: High-resolution analyses of concentrations and sizes of refractory black carbon particles deposited in northwestern Greenland over the past 350 years – Part 1: Continuous flow analysis of the SIGMA-D ice core using the wide-range Single-Particle Soot Photometer and a high-efficiency nebulizer

Abstract. Ice cores can provide long-term records of refractory black carbon (rBC), an important aerosol species closely linked to the climate and environment. However, previous studies of ice cores only analyzed rBC particles with a diameter of < 500 nm, which could have led to an underestimation of rBC mass concentrations. Information on the size distribution of rBC particles is very limited, and there are no Arctic ice core records of the temporal variation in rBC size distribution. In this study, we applied a recently developed improved technique to analyze the rBC concentration in an ice core drilled at the SIGMA-D site in northwestern Greenland. The improved technique, which uses the modified Single-Particle Soot Photometer (SP2) and a high-efficiency nebulizer, widens the measurable range of rBC particle size. For high-resolution continuous analyses of ice cores, we developed a continuous flow analysis (CFA) system. Coupling of the improved rBC measurement technique with the CFA system allows accurate high-resolution measurements of the size distribution and concentration of rBC particles with a diameter between 70 nm and 4 µm, with minimal particle losses. Using this technique, we reconstructed the size distributions and the number and mass concentrations of rBC particles during the past 350 years. On the basis of the size distributions, we assessed the underestimation of rBC mass concentrations measured using the conventional SP2s. For the period 2003–2013, the underestimation of the average mass concentration would have been 12 %–31 % for the SIGMA-D core.

Thermal-Hydraulic Network Model for steady-state thermal analysis and design of power transformer magnetic cores

The safe operation of power transformers is related to their internal temperatures, which increase due to the heat generated in their active part. The core is subjected to hysteresis, eddy current and stray losses, which lead to its heating and the temperature rise. This paper presents a TH model for determining temperatures along the magnetic cores of power transformers. The inclusion of the transformer’s magnetic core in thermal modeling is of paramount importance due to its significant impact on the overall thermal performance and reliability of the transformer. Traditional thermal models predominantly focus on the oil flow and windings, overlooking the core’s contribution to heat generation and dissipation. Based on the constructive and operational data, the model determines the complete oil flow and temperature distributions over the columns, yokes, and joints by iteratively solving an algorithm composed of hydraulic and thermal resistance networks. The constructive characteristics, as the stacking sheets forming different steps and the anisotropy for heat transfer in different directions, are considered. The analytical results are compared to experimental measurement using an optical fiber sensor allocated in the core of a prototype transformer, indicating that the model can satisfactorily predict the hydraulic and thermal behaviors of magnetic cores.

Experimental Study on Fluid Dissipation Effects in Core Samples by NMR Measurement

Laboratory core nuclear magnetic resonance (NMR) relaxation measurements offer geological information, including rock porosity and oil saturation, relevant to logging. When core samples drilled from wells are exposed to air, the fluids within their pores inevitably dissipate. This phenomenon may lead to discrepancies between the results of nuclear magnetic resonance relaxation experiments and the actual situation underground. To deeply explore the impact of fluid dissipation on NMR core analysis experimental results, a series of simulated dissipation experiments were designed under constant temperature and humidity conditions. Variations in one-dimensional and two-dimensional NMR measurement results of oil-saturated samples were examined under varying crude oil viscosities and dissipation times. The experimental results indicate that as exposure time increases, the T2 distribution of oil-saturated cores decreases, and the amplitude of the T2 distribution peaks decreases. Both oil and water relaxation components show a decreasing trend; however, the dissipation rate of the bounding water component significantly exceeds that of the crude oil component. By employing two-dimensional NMR relaxation time distribution fluid quantitative analysis technology, the relationship between the dissipation rates of various phase fluids and exposure time during the stable dissipation stage was analyzed. This offers a reference for adjusting the oil saturation of exposed cores based on NMR measurements.

Seismic modeling and simulation of the graphite core in gas-cooled micro-reactor

To evaluate the structural safety of the graphite core in a gas-cooled micro-reactor and to assess its structural response under seismic loads, a study was conducted. By comparing the acceleration and velocity curves obtained from small-sized graphite block collision experiments and collision simulations, it was determined that the simulation results accurately represent the real collision behavior of graphite blocks. The collision stiffness and damping parameters were derived from these curves. Subsequently, simulations of graphite components in the core were performed to establish the stiffness and damping parameters of the graphite blocks, which were then incorporated into the core analysis calculations. To validate the accuracy of the core numerical model and simplify the vibration form, the core model was divided into in-plane and axial models. A full-core model calculation was then carried out to determine the forces between graphite components. The final results confirm that the graphite core adheres to the ASME design specifications under seismic loads.

Prevalence, transmission and genomic epidemiology of mcr-1-positive colistin-resistant Escherichia coli strains isolated from international airplane waste, local resident fecal and wastewater treatment plants.

The emergence and dissemination of mcr-1-positive Escherichia coli (MCRPEC) represent a critical public health threat. Here, we conducted a prospective analysis of MCRPEC isolates from wastewater treatment plants (WWTPs), local residents' fecal (LRF), and international airplane waste (IAW) to investigate their genetic characteristics and transmission patterns circulating in human-environment domains. The MCRPEC prevalence was 2.43 % in WWTPs, 1.37 % in IAW and 0.69 % in LRF. MCRPEC showed substantial genetic diversity, encompassing 61 sequence types (primarily ST1011, ST101, and ST2705), 7 plasmid types (primarily IncI2), 8 phylogroups (primarily A and B1), 9 mcr-1-flanked lineages (primarily L5), 6 clusters (primarily C2 and C4), diverse serotypes, and 61.95 % transposon-containing strains. The mcr-1 gene co-existed with 46 antibiotic resistance genes (ARGs) and 19 virulence factor genes (VFGs). Notably, 6 IncI2 plasmids carried the blaCTX-M, IS1380, and mcr-1 genes. MCRPEC from WWTPs harbored a greater number of ARGs (56.95 ± 5.99) but fewer VFGs (15.03 ± 6.40) compared to those from human-associated sources (LRF and IAW). ST1011, ST2705, IncHI2, and L7 were prevalent in WWTP-derived MCRPEC, whereas IncX4 and L3 were more common in human-derived MCRPEC. Genetic features such as ST101, ST48, IncI2, L4, L5, C2, and C4 were simultaneously present in strains from LRF, IAW, and WWTPs. Core genetic analyses also showed genetically similar MCRPEC strains across various geographic locations. The findings underscore the extensive dissemination, strong environmental adaptation, and clonal transmission of MCRPEC across diverse reservoirs, reinforcing the urgent need for coordinated multisectoral surveillance of human and environment interfaces to effectively mitigate further transmission.

Predicting trends in atmospheric CO2 across the Mid-Pleistocene Transition using existing climate archives

Abstract. During the Mid-Pleistocene Transition (MPT), ca. 1200–800 000 years ago (ka), the Earth's glacial cycles changed from 41 to 100 kyr periodicity. The emergence of this longer ice age periodicity was accompanied by higher global ice volume in glacial periods and lower global ice volume in interglacial periods. Since there is no known change in external orbital forcing across the MPT, it is generally agreed that the cause of this transition is internal to the Earth system. Resolving the climate, carbon cycle, and cryosphere processes responsible for the MPT remains a major challenge in Earth and palaeoclimate science. To address this challenge, the international ice core community has prioritised recovery of an ice core record spanning the MPT interval. Here we present results from a simple generalised least-squares (GLS) model that predicts atmospheric CO2 out to 1.8 Myr. Our prediction utilises existing records of atmospheric carbon dioxide (CO2) from Antarctic ice cores spanning the past 800 kyr along with the existing LR04 benthic δ18Ocalcite stack (Lisiecki and Raymo, 2005; hereafter “benthic δ18O stack”) from marine sediment cores. Our predictions assume that the relationship between CO2 and benthic δ18O over the past 800 000 years can be extended over the last 1.5 million years. The implicit null hypothesis is that there has been no fundamental change in feedbacks between atmospheric CO2 and the climate parameters represented by benthic δ18O, global ice volume, and ocean temperature. We test the GLS-model-predicted CO2 concentrations against observed blue ice CO2 concentrations, δ11B-based CO2 reconstructions from marine sediment cores, and δ13C of leaf-wax-based CO2 reconstructions (Higgins et al., 2015; Yan et al., 2019; Yamamoto et al., 2022). We show that there is no clear evidence from the existing blue ice or proxy CO2 data to reject our predictions or our associated null hypothesis. A definitive test and/or rejection of the null hypothesis may be provided following recovery and analysis of continuous oldest ice core records from Antarctica, which are still several years away. The record presented here should provide a useful comparison for the oldest ice core records and an opportunity for further constraints on the processes involved in the MPT.

Correlation of Seismic Data and Sediment Cores From the Seabed in the Medieval Harbour at Avaldsnes, Norway

ABSTRACTThis interdisciplinary study demonstrates the successful integration of non‐destructive geophysical methods and sediment core analyses for mapping the seabed in the historical harbour at Avaldsnes in south‐west Norway. In the Medieval Period, this was a royal manor, with the harbour as a central hub for the Hanseatic League in the 14th to 15th centuries. The use of an Autonomous Surface Vehicle (ASV) mounted with two distinct sub‐bottom profiler (SBP) systems facilitated the acquisition of high‐resolution seismic data, providing efficient imaging of the seafloor and subsurface layers. Sequence of fifteen sediment cores allowed for the description and dating of stratigraphy and the depositional environment. In combination, these methods provided a multidimensional understanding of the distribution of subsea sediments in the harbour, while preserving most of the archaeological context. The analysis revealed organic‐rich sediments, primarily consisting of fine detritus gyttja, accumulated over the last 1700 years, trapping certain archaeological features. Deposition of the soft sediments likely commenced due to a lower relative sea level, possibly accompanied by intensified land‐use and harbour activity. The study identified several minor anomalies in the seismic data, potentially representing artefacts of archaeological importance. An anomaly of significant size might correspond to a buried shipwreck or harbour structure. By providing a comprehensive understanding of sediment dynamics and human‐environment interactions in the harbour, the research contributes to the preservation and management of an important cultural heritage site.

Developing a geomechanical model to predict breakdown pressure in a vertical borehole using failure analysis: a case study

Breakdown is an important process in geomechanics; a very complex process in hydraulic fracturing which has been the subject of extensive research in the literature. There exist several models in the literature for predicting the breakdown pressure. In this research, the breakdown pressure for hydraulic fracturing in a vertical borehole was modeled using 2D and 3D failure analysis. In the geomechanical model constructed in this case study, elastic moduli were obtained using petrophysical data as well as data extracted from core analysis. The in-situ stress state of the reservoir was obtained by poroelastic horizontal strain model and was then validated by field data. To test the accuracy of the horizontal strain model, several models were used to obtain the minimum horizontals stress. At the end, the induced principal stresses inside the borehole were modeled by Kirch Equations. Four failure criteria, namely Mohr–Coulomb, 2D Hoek–Brown, Hubbert-Willis and 3D Mogi-Coulomb were used to obtain the breakdown pressure for the target reservoir. Based on the prediction results of these failure criteria, it was obtained that 2D Hoek–Brown, Hubbert-Willis, and 3D Mogi-Coulomb criteria resulted in seemingly unrealistic breakdown pressures with respect to the minimum horizontal stress gradient. The Mohr–Coulomb criterion produced lower breakdown pressure gradients, yet closer to the minimum horizontal stress values, even though it neglects the effect of intermediate stress.

Laser ablation inductively coupled plasma mass spectrometry measurements for high-resolution chemical ice core analyses with a first application to an ice core from Skytrain Ice Rise (Antarctica)

Abstract. Conventional methods of inorganic impurity analysis do not provide high enough depth resolution for many scientific questions in ice core science. In this study, we present a setup of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for high-resolution glacier ice impurity analysis to the sub-millimetre scale. This setup enables ice core chemical impurity analysis to a depth resolution of ∼182 µm while consuming only very small amounts of ice. The system performs simultaneous analysis of sodium, magnesium and aluminium incorporated in the ice matrix. In this case study within the framework of the WACSWAIN (WArm Climate Stability of the West Antarctic Ice Sheet in the last INterglacial) project, our method is applied to a selection of samples from the Skytrain ice core (West Antarctica) over a total length of 6.7 m consisting of about 130 single samples. The main goal of this study is to use the new LA-ICP-MS method to extract meaningful climate signals on a depth resolution level beyond the limits of continuous-flow analysis (CFA). A comparison between low-resolution CFA data and the high-resolution LA-ICP-MS data reveals generally good agreement on the decimetre scale. Stacking of parallel laser measurements together with frequency analysis is used to analyse the high-resolution LA-ICP-MS data at millimetre resolution. Spectral analysis reveals that despite effects of impurity accumulation along ice crystal grain boundaries, periodic concentration changes in the Skytrain ice core on the millimetre scale can be identified in ice from 26.8 ka (kiloyears before present, i.e. 1950 CE). These findings open new possibilities for climate data interpretation with respect to fast changes in the last glacial period and beyond, for example within the Beyond EPICA oldest-ice project.

Characterizing the Namorado Sandstone in southern Brazil through the analysis of a multi-borehole database and utilizing a contemporary workflow

The petrophysical characterization of reservoirs requires the identification of sedimentary facies based on the integration of geophysical well logs and rock analyses in the laboratory, which is one of the significant challenges for the petroleum industry. In this work, laboratory analysis results were linked to quality controls of data pre-processing in a new workflow by integrating several techniques. The wells studied were zoned and laterally correlated based on electrofacies characteristic core analysis and petrographic descriptions. This integration resulted in a modeled geologic section for the Namorado Sandstone in the Campos Basin of southeastern Brazil, created based on various data from each well. The borehole NA2 was selected as the key wellbore after creating this section. The logs from this borehole were then analyzed to separate the permo-porous (reservoirs) and non-porous (non-reservoirs) horizons. The zones containing water and hydrocarbons in the permo-porous sections of interest were split along the wells. Subsequently, the identified sectors were interpreted using petrophysical techniques to confirm the preliminary categorization. After combining all quantitative products to quantify the porous layers capable of producing mobile oil, the cut-off factors were introduced. The next step was determining the parameters of the Archie equation, the amount of clay present, and the water saturation from core descriptions, which led to the discovery of deep laminated sandstones. The results strongly correlate with lithology, geological facies, borehole logs, and petrophysical laboratory data. Based on these findings, it is evident that the clay concentration is the primary factor influencing the oil saturation in this reservoir.

Study on offshore sandstone reservoir classification method based on cuttings digitization technology

Abstract Reservoir classification research is of great significance for improving the accuracy of oil and gas exploration and development, reducing risks, and enhancing economic benefits. Traditional reservoir classification methods are primarily based on macroscopic geology and core analysis, lacking descriptions of reservoir pore structure characteristics and microscopic geological features, with very limited data dimensions obtained. This study uses sandstone cuttings samples from a well in an offshore sandstone reservoir as an example and employs digital core technology to conduct reservoir classification research. First, high-resolution micro-CT scanning was performed, and the microscopic lithological characteristics of different blocks were observed based on the scanned images. The diagenesis and particle contact relationships were qualitatively analyzed. Next, digital methods were used to quantitatively analyze pore structure characteristic parameters such as porosity, permeability, and connectivity. Then, the qualitative analysis results of the images were combined with the quantitative analysis results of the digital cuttings to form a set of classification evaluation standards for a certain sandstone reservoir in the eastern South China Sea. Finally, based on the characteristic parameters obtained from the digital quantitative analysis of the cuttings and the on-site pressure-flow data, a big data analysis method was used to screen out the reservoir characteristic parameters with high correlation, providing data support for the rapid evaluation of reservoir mobility. The reservoir classification evaluation standards and flow prediction models formed in this study can provide technical support for accurately formulating reservoir development plans in oil fields in the eastern South China Sea and have significant reference value for the fine evaluation of similar reservoirs. In addition, reservoir classification methods based on digital core analysis exhibit efficiency and multidimensionality, which are crucial for well placement selection, wellbore design, stability assessment of well walls during drilling, interpretation of logging data, and accurate prediction of production capacity.