Thin Sections Research Articles

Detecting the presence of different Retzius periodicities at the population level from repetitive linear enamel hypoplasia among Lufengpithecus lufengensis and Pongo pygmaeus

AbstractObjectivesReconstruction of life histories for fossil and living primates draws on rate of enamel layering, termed Retzius periodicity (RP in days) expressed as surface perikymata, during dental crown formation. Disclosure of RP through thin sectioning is destructive; consequently, sample sizes are inadequate to detect the range of RPs present in discrete taxa. We propose an additional method to detect RPs at the population level based on twice‐yearly average recurrence of linear enamel hypoplasia (rLEH) in apes shown by prior studies.Materials and MethodsCasts of teeth from orangutans (Pongo pygmaeus) (n = 40) and Lufengpithecus lufengensis (n = 57) from Late Miocene Shihuiba, China, (133 and 138 LEH, respectively) were recorded with scanning electron microscope (SEM) and confocal microscopy to yield perikymata counts between episodes of LEH. Frequency distributions of aggregated perikymata counts between LEH were compared to frequency distribution of tooth‐specific ratios of perikymata counts between successive LEH (this latter step removes effects of RP differences within a sample).ResultsDrawing on prior research, two successive intervals between LEH span 1 year on average. Ratios of successive to previous intervals between LEH show that orangutans and Lufengpithecus exhibit two asymmetric intervals centered on 5.3 and 6.7 months, likely reflecting the effect of axial tilt insolation on phenology. Estimated RPs are not unimodal but show a range from 7 to 12 in Lufenpithecus and 8 to 11 in Pongo, comparable to published values.DiscussionRepetitive LEH is sufficiently regular to detect additional RPs which, in the case of Lufengpithecus, have yet to be demonstrated histologically.

Preparation and Sectioning of Paraffin-Embedded Tissue for Histology and Histochemistry.

Cutting thin sections of plant tissues enables observation of internal structures and inner cell layers, and it facilitates various histochemical staining methods. Paraffin embedding gives the tissues a uniform stiffness that is sufficient for sectioning with a microtome. Here, we describe the procedures for preparation of paraffin-embedded tissues and the techniques for sectioning with a microtome. This method is applicable to various types of tissues, including rice shoot apex and immature inflorescence.

Relationship between bone union and degree of bone marrow fibrosis at resection margins of advanced mandibular ORN

BackgroundThe pathological evaluation of cancellous bone at resection margins of mandibular osteoradionecrosis (ORN) has not been well elucidated. Here, we developed a unique classification system for evaluating the degree of bone marrow fibrosis, one of most common pathological features, in patients with mandibular ORN, based on which we investigated its relationship with treatment outcome.MethodsThis study included 15 patients who underwent mandibulectomy and free fibula osteocutaneous flap reconstruction. The extent of mandibulectomy was determined, with safety margins of approximately 10 mm from the apparent osteolytic areas on preoperative computed tomography image. Special staining was performed on thin sections from center of the osteolytic areas (medial area) and bilateral resection margins, and the degree of bone marrow fibrosis was evaluated and investigated its relationship with presence of bone union as a treatment outcome.ResultsThe degree of bone marrow fibrosis of medial area was significantly higher than those of resection margins. Although most resection margins had collagen fibers which indicate severe fibrosis, all transferred fibula flaps achieved bone union.ConclusionWhen mandibulectomy is performed with safety margins of approximately 10 mm from the apparent osteolytic areas, all transferred fibula flaps achieved bone union regardless of the degree of bone marrow fibrosis at resection margin. In other words, the association between severe bone marrow fibrosis at resection margins and treatment outcome was not seen.Clinical RelevanceSetting safety margins of approximately 10 mm may achieve bone union, but further study is needed.

Precontouring as a Tool to Improve the Laser Powder Bed Fusion Printability of Inconel939 Thin Walls

This work investigates the influence of adding a contour scan prior to hatching (precontouring) on the printability of Inconel 939 thin‐wall sections produced by laser powder bed fusion. Walls with thicknesses ranging from 500 to 1500 μm, manufactured with two hatch scanning parameter sets that give rise to different microstructures and very high density in bulk samples of the same alloy, are investigated. It is shown that, while the texture as well as the grain size and shape is only influenced moderately by the contour scanning strategy, precontouring does lead to a significant reduction of the melt pool depth, an effect that is increasingly pronounced with decreasing wall thickness. This work highlights the role of the precontour scan as a heat sink, shifting the normalized enthalpy input toward lower values and thus limiting the accumulation of excess heat. Precontouring is put forward as a scanning strategy to improve the manufacturability of thin sections.

Facies Analysis and Depositional Environment of the Euphrates Formation in Selected Sections, Southwestern Iraq

The current study aims to investigate the microfacies, diagenetic processes, and depositional environments of the twenty-three rock samples from the Lower Miocene Euphrates Formation of two outcrops collected at Bahar-Najaf in Najaf governorate and Al-Shinafiya in Diwaniyah governorate, southern Iraq. Thin sections of these samples were prepared; hence, the nature of microfacies and related depositional environments was established. The formation contains abundant benthonic foraminifers and other fossils like miliolids, echinoderm, coral, gastropods, and pelecypods. Seven distinct microfacies were identified: lime mudstone, miliolid packstone, Pelletal Grainstone, Lime Wackestone, Peloidal Grainstone, Oolitic grainstone Microfacies, and fossiliferous packstone packed with bioclasts. Diagenetic processes evidenced in this study are dissolution, neomorphism, cementation, micritization, and dolomitization. The Euphrates Formation was deposited in a shallow marine setting with fluctuating energy levels, ranging from low-energy lagoons to moderate and high-energy shoals and fore-reef environments. Various microfacies indicate a complex depositional environment on a carbonate platform influenced by biota and sedimentary processes. These observations support the inference that the Euphrates Formation accumulated in shallow open marine, inner barrier, and shoal settings, providing a detailed interpretation of its para-depositional and diagenetic development.

Giant plagioclase in the Steens Basalt, southeast Oregon, USA: Tracking the balance of differentiation processes in continental flood basalt evolution

Giant plagioclase basalts (GPBs), flows that contain abundant and conspicuous plagioclase crystals ≥1 cm in length, exist at many continental flood basalt provinces, and their presence can provide a window into the crustal differentiation processes and storage conditions that produced the magmas prior to eruption. GPB flows occur in the Steens Basalt of southeast Oregon, USA, one of the earliest members of the Columbia River Flood Basalt Group, but their origin in this province has not been studied in detail. We conducted quantitative textural analysis utilizing crystal size distributions (CSDs) at the outcrop and thin section scale, as well as in situ plagioclase trace element and isotopic compositional analysis, in order to elucidate the processes responsible for generating two end-member textural types of GPB found in the Steens Basalt: daisy stone glomerocryst clusters composed of radiating plagioclase laths and single isolated plagioclase. CSD patterns suggest a changing balance of multiple differentiation processes affected the magmas that created each GPB textural type. In the daisy stone plagioclase, crystals rarely exhibit resorption textures, trace element abundances are comparatively low with minimal variability, and Sr isotopes are commonly in equilibrium with groundmass. In the single isolated plagioclase, resorption textures are common, trace element abundances are generally higher and display within crystal variation, and Sr isotopes are typically not in equilibrium with groundmass. These distinctive characteristics require separate mechanisms to generate each end-member GPB texture. Daisy stone GPBs form by growth of large crystals following mafic recharge events that completely resorb entrained cumulate plagioclase. A large amount of plagioclase may then grow with minimal cooling following recharge due to saturation in plagioclase components. In contrast, single isolated GPBs are the result of partial resorption of both entrained and resident plagioclase following less voluminous and less primitive recharge events; regrowth then occurs on the partially resorbed cores when cooling resumes. Both GPB types are formed by thermal cycling, but each texture reflects the differentiation processes that were prevalent during different eruptive stages of the Steens Basalt, as the balance between recharge, crystal fractionation, and assimilation varied in time.

INFLUENCE AND PREDICTION OF SINTERED AGGREGATE SIZE DISTRIBUTION ON THE PERFORMANCE OF LIGHTWEIGHT ALKALI-ACTIVATED CONCRETE

The most effective method for mitigating the adverse environmental impacts of traditional concrete involves substituting cement and natural aggregate with waste and byproduct resources. Utilizing sintered lightweight aggregate (fly ash) in geopolymer concrete emerges as an efficient solution for managing and disposing of significant amounts of fly ash. The influence of sintered aggregate size distribution on the performance of alkali-activated concrete, focusing on compressive strength improvement. The study employs sintered fly ash aggregate (SFA) as coarse aggregate, aiming to optimize packing density through proper particle distribution. The highest compressive strength is achieved with a mix featuring 75% 4-8mm and 25% 8-12mm SFA. Regression-based strength models are developed, exhibiting good alignment with conventional concrete models. Thin section techniques reveal enhanced aggregate-matrix interaction due to the porous structure of SFA. The study emphasizes the potential of SFA in geopolymer concrete for sustainable construction. Lightweight geopolymer concrete, owing to its lower density, significantly reduces the overall structural load.

Quantitative characterization of porosity evolution in the Triassic Chang 8 tight sandstone reservoir during hydrocarbon accumulation in the Maling area, Ordos Basin, China

The Maling area in the Ordos Basin is characterized by delta front deposits. The principal oil-bearing layer, Chang 8 Member (the 8th member of the Triassic Yanchang Formation), manifests low-to-ultra-low porosity and permeability due to the interplay of depositional, diagenetic, and burial processes. The reservoir exhibits pronounced heterogeneity and diagenetic alterations, which limit the efficacy of hydrocarbon exploration. Methodologies employed for this research encompass grain size imaging, physical property assays, petrographic thin sections, scanning electron microscopy, high-pressure mercury intrusion, and X-ray diffraction. These techniques facilitated a comprehensive investigation into the diagenetic attributes and compaction mechanisms of the reservoir. A porosity evolution simulation equation tailored to the Chang 8 tight sandstone reservoir was formulated based on diagenetic evolution traits and geological influences. Interdependencies and correlations among various diagenetic processes were analyzed. During diagenesis, compaction, cementation, and replacement led to a reduction in primary porosity, whereas dissolution-induced secondary pores served as high-permeability channels. A quantitative model for porosity evolution was developed alongside qualitative assessments, achieving a deviation of 3.18% when compared to gas porosity measurements. Evaluation of four representative samples revealed that compaction-induced diagenetic alteration predominates, with burial depth, formation age, and cement types playing critical roles in the evolution of reservoir porosity. This differential diagenetic evolution elucidates the underlying causes of variability in reservoir properties and heterogeneity in pore structure, providing valuable insights for future exploration strategies.

A refined TTC assay precisely detects cardiac injury and cellular viability in the infarcted mouse heart

Histological analysis with 2,3,5-triphenyltetrazolium chloride (TTC) staining is the most frequently used tool to detect myocardial ischemia/reperfusion injury. However, its practicality is often challenged by poor image quality in gross histology, leading to an equivocal infarct-boundary delineation and potentially compromised measurement accuracy. Here, we introduce several crucial refinements in staining protocol and sample processing, which enable TTC images to be analyzed with light microscopy. The refined protocol involves a two-step TTC staining process (perfusion and immersion) and subsequent Zamboni fixation to differentiate myocardial viability and necrosis, and use of Coomassie brilliant blue to label area-at-risk. After the duo-staining steps were completed, the heart sample was embedded and sliced transversally by a cryostat into a series of thin sections (50 µm) for microscopic analysis. The refined TTC (redTTC) assay yielded remarkably high-quality images with striking color intensity and sharply defined boundaries, permitting unambiguous and reliable delineation of the infarct and area-at-risk. In the same animals, the redTTC assay showed good agreement with the in-vivo gold standard measurements (LGE and MEMRI). Meanwhile, redTTC imaging allows tracking of viable cardiomyocytes at cellular resolution, and with this enhanced capability, we convincingly demonstrated the pro-survival action of stem cells based-therapy. Therefore, the redTTC assay represents a significant technical advance that permits precise detection of the true extent of cardiac injury and cardiomyocyte viability. This approach is cost-effective and may be adapted for use in diverse applications, making it highly appealing to many laboratories performing ischemia/reperfusion injury experiments.

Mineralogical Characteristics and Their Usability as Gemstones of Jaspers in Altered Metavolcanics Belonging to the Topçam Formation, Tokat, Turkiye

The jaspers located in the Topçam Mountain, Tepeyurt region (Tokat, Turkey), were formed at green-colored metavolcanic levels within Permian–Triassic schists. The sizes of the jaspers generally vary from a few cm to 1.5 m, and their colors vary from grayish–reddish–brownish/blackish tones depending on the increase in the amount of Fe and Mn elements they contain. According to thin section and X-ray Diffraction (XRD) analysis examinations, it was determined that the composition of jaspers includes quartz, hematite, calcite, and pyrite. As stated by the Wavelength Dispersive X-ray Fluorescence (WDXRF) analysis results, it was observed that the amount of SiO2 in jaspers was 82.5%, and the amount of Fe2O3 was 15.5%. According to Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) analysis results, Fe and Mn impurities, which are thought to cause the color of jaspers, as well as the amount of Fe (6975.5 ppm–46,893.9 ppm–96,431.1 ppm) and the amount of Mn (935.9–3219.7–6040.4 ppm), caused a darkening in color tones (grayish–reddish–brownish/blackish). Cabochon cutting applications were made of jaspers taken from the study area. As a result of these applications, it has been determined that jaspers can be used as gemstones due to their properties, such as their workability, polish retention, and color and light reflection.

Multiscale Characterization of Fractures and Analysis of Key Controlling Factors for Fracture Development in Tight Sandstone Reservoirs of the Yanchang Formation, SW Ordos Basin, China

Tight sandstone reservoirs, despite their low porosity and permeability, present considerable exploration potential as unconventional hydrocarbon resources. Natural fractures play a crucial role in hydrocarbon migration, accumulation, and present engineering challenges such as late-stage reformation in these reservoirs. This study examines fractures in the seventh member of the Triassic Yanchang Formation’s tight sandstone within the Ordos Basin using a range of methods, including field outcrops, core samples, imaging and conventional logging, thin sections, and scanning electron microscopy. The study clarifies the characteristics of fracture development and evaluates the relationship between dynamic and static rock mechanics parameters, including the calculation of the brittleness index. Primary factors influencing fracture development were quantitatively assessed through a combination of outcrop, core, and mechanical test data. Findings reveal that high-angle structural fractures are predominant, with some bedding and diagenetic fractures also present. Acoustic, spontaneous potential, and caliper logging, in conjunction with imaging data, enabled the development of a comprehensive probabilistic index for fracture identification, which produced favorable results. The analysis identifies four key factors influencing fracture development: stratum thickness, brittleness index, lithology, and rock mechanical stratigraphy. Among these factors, stratum thickness is negatively correlated with fracture development. Conversely, the brittleness index positively correlates with fracture development and significantly influences fracture length, aperture, and linear density. Fractures are most prevalent in siltstone and fine sandstone, with minimal development in mudstone. Different rock mechanics layer types also impact fracture development. These insights into fracture characteristics and controlling factors are anticipated to enhance exploration efforts and contribute to the study of similar unconventional reservoirs.

Advanced three-dimensional X-ray imaging unravels structural development of the human thymus compartments

BackgroundThe thymus, responsible for T cell-mediated adaptive immune system, has a structural and functional complexity that is not yet fully understood. Until now, thymic anatomy has been studied using histological thin sections or confocal microscopy 3D reconstruction, necessarily for limited volumes.MethodsWe used Phase Contrast X-Ray Computed Tomography to address the lack of whole-organ volumetric information on the microarchitecture of its structural components. We scanned 15 human thymi (9 foetal and 6 postnatal) with synchrotron radiation, and repeated scans using a conventional laboratory x-ray system. We used histology, immunofluorescence and flow cytometry to validate the x-ray findings.ResultsApplication to human thymi at pre- and post-natal stages allowed reliable tracking and quantification of the evolution of parameters such as size and distribution of Hassall’s Bodies and medulla-to-cortex ratio, whose changes reflect adaptation of thymic activity. We show that Hassall’s bodies can occupy 25% of the medulla volume, indicating they should be considered a third thymic compartment with possible implications on their role. Moreover, we demonstrate compatible results can be obtained with standard laboratory-based x-ray equipment, making this research tool accessible to a wider community.ConclusionsOur study allows overcoming the resolution and/or volumetric limitations of existing approaches for the study of thymic disfunction in congenital and acquired disorders affecting the adaptive immune system.

Bone microstructure analyses in ontogenetic series of Mesosaurus tenuidens from the early Permian of Brazil.

Osteohistological evidence is widely used to infer paleobiological traits of fossil vertebrates, such as ontogeny and growth rates. Mesosaurs, an enigmatic group of aquatic reptiles from the early Permian, are the most well-known Paleozoic amniotes from Africa and South America. Their fossils are abundant in South America, ranging from the central-west region of Brazil to the southernmost areas, as well as parts of Paraguay and Uruguay. In this contribution, we examined the bone microstructure of Mesosaurus tenuidens by analyzing thin sections of axial and appendicular elements of several specimens collected from various Brazilian sites. The microstructure of the bones showed minimal histological variability among elements, predominantly composed of parallel-fibered tissues, indicating slow growth rhythm, along with increased bone density attributed to pachyosteosclerosis. The cortical area consists of poorly vascularized parallel-fibered bone tissue, which was interrupted by multiple cyclical growth marks, some of them being supernumerary, suggesting a strong influence of seasonality. Moreover, the organization of growth marks suggests distinct life history trajectories among individuals collected from different outcrops, reflecting environmental heterogeneity throughout the basin. Internally, the endosteal domain exhibits greater vascularization compared to the cortices and frequently contained calcified cartilage. In the ontogenetic series, there was a progressive filling of the medullary region from small to large individuals. The presence of the External Fundamental System (a proxy indicating somatic maturity) was observed in femora and ribs, suggesting that determinate growth was already occurring in Permian mesosaurs and may not be an exclusive specialization of crown amniotes.

Research on improving permeability of granite reservoir: Polyhydrogen chelating acid acidizing

ABSTRACT Acidization is a highly effective technique for increasing oil well productivity. Therefore, it is critical to study effective stimulation of low-permeability granite reservoirs using acidification. Using the granite reservoir of Baobab oilfield in Chad as the research object, the properties of reservoir rocks were tested using XRD and rock thin section analysis. Dissolution experiments, core flooding experiments, and CT scanning were used to investigate the increased permeability and changes in the pore structure of the cores during acidification. The minerals in the rocks are primarily plagioclase, kalifeldspar, and quartz, with trace amounts of calcite, chlorite, magnetite, illite, biotite, hornblende, sphene, and sericite. At 80°C and 10 mL of main acid injection, polyhydrogen chelating acid (6% HCl + 5% SA601 + 7% SA701) improved granite permeability more than mud acid (8% HCl + 2% HF) and fluoroboric acid (8% HCl + 8% HBF4), with permeability increase of 3.68. The CT three-dimensional images of the rocks show that both the cores acidified with polyhydrogen chelating acid and mud acid formed continuous acid-etched wormholes, while the cores acidified with fluoroboric acid did not. Compared to the mud acid, the core acidified by the polyhydrogen chelating acid produced more visible acid-etched wormholes. Meanwhile, the polyhydrogen chelating acid was more effective at improving the pore throats and expanding the flow channels in the core. This study serves as a reference for the application of acidification and increasing production in low-permeability granite reservoirs.

Study on the Impact of Porous Media on Condensate Gas Depletion: A Case Study of Reservoir in Xihu Sag.

During the depletion and pressure reduction process in condensate gas reservoirs, the precipitation of condensate oil transforms the single-phase gas flow into a two-phase gas-liquid flow, significantly reducing the permeability. Currently, microscopic studies of the phase behavior of condensate gas in porous media mainly focus on observing and describing the occurrence of condensate oil, lacking quantitative calculations and direct observations of condensate oil throughout the entire depletion cycle. This paper uses a microvisualization method to simulate the depletion process of condensate gas reservoirs. Condensate gases with oil contents of 175.3 and 505.5 g/cm3 were prepared by mixing methane, ethane, hexane, and decane in specific proportions. Pore structures were extracted from thin sections of real core casts, and microfluidic chips with a minimum pore diameter of 20 μm and an areal porosity of 20.75% were fabricated by using a chemical wet etching method. Subsequently, microfluidic condensate gas depletion experiments were conducted with chip images recorded during the depletion process. Grayscale analysis of the depletion images was performed using ImageJ software to quantitatively calculate condensate oil saturation and recovery rates, analyzing the effects of different condensate oil contents on condensate gas depletion, and comparing the differences between depletion in porous media and in a PVT cell. The conclusions drawn are as follows: the dew points of high and low in the porous media are 3.15% and 1.85% higher than those in the PVT cell, respectively. In the early stages of depletion, condensate oil saturation in porous media is higher than that in the PVT cell, while in the middle to late stages, condensate oil saturation in porous media is lower than that in the PVT cell. The condensate oil recovery rate in porous media is significantly higher than the depletion recovery rate in the PVT cell. Condensate oil tends to precipitate and disperse at blind ends and corners, while it easily forms patches in mainstream large pores.

Unique bone histology of modern giant salamanders: a study on humeri and femora of Andrias spp.

The osteohistology of Andrias spp. is a pivotal analogue for large fossil non-amniotes (e.g., Temnospondyli), and the endangered status of this taxon underlines the importance of gathering information on its growth. We here present the first osteohistological study by petrographic thin sections of an ontogenetic series of humeri and femora of eight individuals of varying sizes (28.5–104 cm) and ages (2.5–32 years) of Andrias japonicus from the Hiroshima City Asa Zoological Park, Japan. In addition, two individuals of A. cf. davidianus of unknown age but of different size (62 cm and 94 cm) were studied. All samples of Andrias spp. show a primary avascular periosteal cortex made of parallel-fibred tissue around the ossification center in the petrographic thin sections. Mainly in small individuals, the fibers forming this tissue are very coarse and loosely organized. With increasing size and age, the coarse tissue is irregularly intermixed and later replaced with finer and better organized fibers. This histologic change is accompanied by a change from diffuse annuli in the inner cortex to distinct lines of arrested growth (LAGs) in the outer cortex. We interpret these changes in tissue and the appearance of distinct growth marks as indicating the onset of active reproduction. The lack of primary vascularization around the ossification center in our Andrias spp. sample is striking and contradicts other observations. Vascularity may be prone to plasticity and further studies are necessary. We hypothesize that the large osteocyte lacunae and the dense networks of canaliculi observed in our sample may have nourished the tissue instead of primary vascular canals. We measured the size of osteocyte lacunae of Andrias spp. in comparison to other Lissamphibia, and found them to be significantly larger throughout ontogeny. The periosteal cortex contains a high amount of thick Sharpey’s fibers all around the midshaft cross sections. The two samples of Andrias cf. davidianus show tissue and growth mark distribution similar to that observed in A. japonicus. However, the large individual of A. cf. davidianus differed in its extremely osteosclerotic condition and the retention of a small layer of calcified cartilage in the endosteal region of the femur. It remains unclear whether these differences are related to plasticity, taxonomy, sex, exogenous factors, or attributable to a regenerated but fully regrown leg. Although the present study is based on zoo-kept and not wild, animals, it yields important insights into osteohistological plasticity and growth patterns in giant salamanders.

Experimental Evaluation of Blockage Resistance and Position Caused by Microparticle Migration in Water Injection Wells

Offshore oil field loose sandstone reservoirs have high permeability. However, during the water injection process, water injection blockage occurs, causing an increase in injection pressure, making it impossible to continue injecting water on site. Current research mainly focuses on the factors causing water injection blockage, with less attention given to the blockage locations and the pressure increase caused by water injection. There is a lack of research on the change in the law of injection capacity. This paper establishes a simulation experiment for water injection blockage that can accommodate both homogeneous and heterogeneous cores. The experimental core is 1 m long and capable of simulating the blockage conditions in the near-well zone during water injection, thereby analyzing the core blockage position and blockage pressure. The study clarifies the influence of water quality indicators, heterogeneity, and core length on the blockage patterns in reservoirs during water injection. The research findings are as follows: I. The reservoir blockage samples were characterized using scanning electron microscopy (SEM), casting thin sections, and X-ray diffraction (XRD) analysis. The results indicate that the main factors causing blockage are clay, silt, and fine particulate suspensions, with the fine particles mainly consisting of hydrated silicates and alkali metal oxides. The primary cause of blockage in loose sandstone is identified as the mechanism of migration and accumulation of clay, fine rock particles, and suspended matter in the injected water. II. By monitoring pressure and permeability changes in the core flooding experiments, the impact of reservoir heterogeneity on water injection capacity was evaluated. The evaluation results show that the blockage locations and lengths in heterogeneous cores are twice those in homogeneous cores. III. For heterogeneous reservoirs, if the initial permeability at the inlet is lower than in other segments of the core, significant blockage resistance occurs, with the final resistance being 1.27 times that of homogeneous cores. If the initial permeability at the inlet is higher than in other parts, the final blockage resistance is close to that of homogeneous cores. This study provides theoretical support for the analysis of blockage locations and pressures in loose sandstone water injection and offers technical support for the design of unplugging ranges and pressures after blockage in heterogeneous formations. At the same time, it provides a theoretical basis for selecting the direction of acidizing after blockage occurs in loose sandstone.

Formation mechanism and oil-bearing properties of gravity flow sand body of Chang 63 sub-member of Yanchang Formation in Huaqing area, Ordos Basin

Abstract Gravity flow sand body is an important reservoir for deep water deposition. The in-depth study of its formation mechanism and oil enrichment law can provide important guidance for oil and gas exploration in deep water areas. In this article, taking the deep-water gravity flow sand body of the Triassic Chang 63 sub-member in the Huaqing area as an example, the identification characteristics, formation mechanism, and oil-bearing characteristics of the gravity flow sand body are systematically discussed. The results show that sandy debris flow, turbidite flow, and mixed event flow present different superposition combination modes on vertical gravity flow deposition. The lithofacies of the gravity flow sandstone complex are mainly affected by lake level fluctuation, provenance supply, and hydrodynamic conditions. According to the formation conditions, sedimentary types. and distribution characteristics of deep water gravity flow sand bodies, a three-dimensional sedimentary mode of deep water gravity flow sand bodies is established. It is found that the physical and oil-bearing properties of the sandy debris flow sand body are better than those of the turbidity flow sand body. The reason is that the proportion of debris in the sand body of sandy debris flow is high, and the content of debris particles is generally greater than 70% according to the statistics of thin sections, which is conducive to the formation of pores. Second, sandy debris flow belongs to block transport, and the mixing of lithology is not sufficient in the process of block flow transport, so some pores will be preserved. Finally, gravity flows, which are dense at the beginning, become less dense later as detrital sediments unload, allowing them to be transported to distant regions. Therefore, the monolayer thickness of the sandy debris flow sand body is large (generally greater than 0.5 m), and the particle size of the debris ranges from 0.03 to 0.3 mm. Finally, the physical and oil-bearing properties of the sandy clastic flow sand body are better than those of the turbidity flow sand body.

Pore size classification and prediction based on distribution of reservoir fluid volumes utilizing well logs and deep learning algorithm in a complex lithology

Pore size analysis plays a pivotal role in unraveling reservoir behavior and its intricate relationship with confined fluids. Traditional methods for predicting pore size distribution (PSD), relying on drilling cores or thin sections, face limitations associated with depth specificity. In this study, we introduce an innovative framework that leverages nuclear magnetic resonance (NMR) log data, encompassing clay-bound water (CBW), bound volume irreducible (BVI), and free fluid volume (FFV), to determine three PSDs (micropores, mesopores, and macropores). Moreover, we establish a robust pore size classification (PSC) system utilizing ternary plots, derived from the PSDs.Within the three studied wells, NMR log data is exclusive to one well (well-A), while conventional well logs are accessible for all three wells (well-A, well-B, and well-C). This distinction enables PSD predictions for the remaining two wells (B and C). To prognosticate NMR outputs (CBW, BVI, FFV) for these wells, a two-step deep learning (DL) algorithm is implemented. Initially, three feature selection algorithms (f-classif, f-regression, and mutual-info-regression) identify the conventional well logs most correlated to NMR outputs in well-A. The three feature selection algorithms utilize statistical computations. These algorithms are utilized to systematically identify and optimize pertinent input features, thereby augmenting model interpretability and predictive efficacy within intricate data-driven endeavors. So, all three feature selection algorithms introduced the number of 4 logs as the most optimal number of inputs to the DL algorithm with different combinations of logs for each of the three desired outputs. Subsequently, the CUDA Deep Neural Network Long Short-Term Memory algorithm(CUDNNLSTM), belonging to the category of DL algorithms and harnessing the computational power of GPUs, is employed for the prediction of CBW, BVI, and FFV logs. This prediction leverages the optimal logs identified in the preceding step. Estimation of NMR outputs was done first in well-A (80% of data as training and 20% as testing). The correlation coefficient (CC) between the actual and estimated data for the three outputs CBW, BVI and FFV are 95%, 94%, and 97%, respectively, as well as root mean square error (RMSE) was obtained 0.0081, 0.098, and 0.0089, respectively. To assess the effectiveness of the proposed algorithm, we compared it with two traditional methods for log estimation: multiple regression and multi-resolution graph-based clustering methods. The results demonstrate the superior accuracy of our algorithm in comparison to these conventional approaches. This DL-driven approach facilitates PSD prediction grounded in fluid saturation for wells B and C.Ternary plots are then employed for PSCs. Seven distinct PSCs within well-A employing actual NMR logs (CBW, BVI, FFV), in conjunction with an equivalent count within wells B and C utilizing three predicted logs, are harmoniously categorized leading to the identification of seven distinct pore size classification facies (PSCF). this research introduces an advanced approach to pore size classification and prediction, fusing NMR logs with deep learning techniques and extending their application to nearby wells without NMR log. The resulting PSCFs offer valuable insights into generating precise and detailed reservoir 3D models.

Exploring comparative heterogeneity management for precise water saturation assessment in carbonate formations: Dean-Stark measurements and beyond

Accurate determination of water saturation is a critical aspect of reservoir characterization and development potential of a hydrocarbon field. The inherent heterogeneity in carbonate reservoirs significantly influences the Archie equation coefficients and, consequently, water saturation calculations. In this study, 160 direct core sample water saturation measurements using the Dean-Stark method have been used. The primary goal was to identify the most suitable reservoir heterogeneity management approach for water saturation calculation. The research focuses on the Dalan and Kangan formations (equivalent to Khuff Formation), known as some of the most hydrocarbon-rich (gas) reservoirs globally, located in the western part of the Persian Gulf. To manage reservoir heterogeneity, we employed various techniques, including Winland R35, flow zone indicator, Lucia, pore types, and electrofacies, utilizing porosity and permeability core data, thin section studies, and well-logging data to classify the studied intervals into more homogeneous categories. Subsequently, we measured Archie parameters and, for the first time, water saturations derived from Dean-Stark measurements were compared with Archie saturations from various heterogeneity management methods. Additionally, the influence of geological and petrophysical parameters on the accuracy of water saturation calculations in different rock types is discussed. Our results highlighted the significance of geometrical attributes of pore types, pore throat radius, and permeability as key factors affecting the precision of water saturation calculations. Moreover, our investigation revealed that Lucia's rock typing methodology exerted a substantial influence on the control of permeability and the distribution of water saturation within the reservoir. Our analysis revealed that the electrofacies method provided the most precise estimates for water saturation, with a mean difference of 0.07 (v/v) units compared to the Dean-Stark method. Subsequently, the accuracy of predicted water saturation in rock types determined by the Lucia method, with a mean error of 0.09 (v/v), ranked second among the rock typing methods. Winland R35 and flow zone indicator methods exhibited the highest uncertainty in water saturation estimation, with mean differences of 0.23 and 0.21 (v/v), respectively, compared to the Dean-Stark method.