Presence Of Microporosity Research Articles

Petrophysics of Low Resistivity Reservoir

Low resistivity reservoirs have long been known in the oil and gas industry as reservoirs that have significant potential and contribution to oil and gas production. This reservoir is very unique because of its relatively low resistivity readings (< 5 Ohm) and often other log responses do not show the way carbonate-containing reservoirs do, so they are often overlooked and not considered as potential carbon reservoirs. The low resistivity reading also causes the Water Saturation (Sw) value to be too high, which contributes to why the reservoir is overlooked. Theoretically, the factors that cause low resistivity readings are high clay/shale content, fine grain size, high salinity air formation, presence of microporosity and presence of conductive minerals which affect resistivity log readings in addition to other things such as low structured reservoirs. and there is a significant slope of the layers. Based on statistic reports, generally in low resistivity reservoirs there is a combination of two or more of the causal factors mentioned. This study aims to identify the characteristics of low resistivity reservoirs in the Upper Cibulakan Formation, West Java Basin, especially from log readings and recognition of what factors support reservoir formation both from the results of core and log analysis as well as selecting combinations for calculating water saturation. From the low resistivity reservoir characteristics, it is hoped that it can be used to find and identify the distribution of similar reservoirs so that potential reservoirs that have been overlooked so far can be identified, discovered and developed which in the end are expected to provide additional contributions both in terms of education and for the oil and gas industry in finding new reserves for oil and gas production in Indonesia.

Imaging and Modeling the Impact of Multi‐Scale Pore Connectivity on Two‐Phase Flow in Mixed‐Wet Rock

AbstractThe wetting properties of pore walls have a strong effect on multiphase flow through porous media. However, the fluid flow behavior in porous materials with both complex pore structures and non‐uniform wettability are still unclear. Here, we performed unsteady‐state quasi‐static oil‐ and water‐flooding experiments to study multiphase flow in two sister heterogeneous sandstones with variable wettability conditions (i.e., one natively water‐wet and one chemically treated to be mixed‐wet). The pore‐scale fluid distributions during this process were imaged by laboratory‐based X‐ray micro‐computed tomography (micro‐CT). In the mixed‐wet case, we observed pore filling events where the fluid interface appeared to be at quasi‐equilibrium at every position along the pore body (13% by volume), in contrast to capillary instabilities typically associated with slow drainage or imbibition. These events corresponded to slow displacements previously observed in unsteady‐state experiments, explaining the wide range of displacement time scales in mixed‐wet samples. Our new data allowed us to quantify the fluid saturations below the image resolution, indicating that slow events were caused by the presence of microporosity and the wetting heterogeneity. Finally, we investigated the sensitivity of the multi‐phase flow properties to the slow filling events using a state‐of‐the‐art multi‐scale pore network model. This indicated that pores where such events took place contributed up to 19% of the sample's total absolute permeability, but that the impact on the relative permeability may be smaller. Our study sheds new light on poorly understood multiphase fluid dynamics in complex rocks, of interest to for example, groundwater remediation and subsurface CO2 storage.

LINEAR AND NONLINEAR CONVECTIVE INSTABILITIES OF A MAXWELL-CATTANEO BIDISPERSIVE LAYER IN LOCAL THERMAL NON-EQUILIBRIUM

The linear and nonlinear instabilities of a horizontal Nield-Kuznetsov bidispersive layer in local thermal non-equilibrium subject to the Maxwell-Cattaneo (MC) effect is studied. In the absence of the MC effect, we prove that only a steady mode can exist. The presence of the MC effect, which introduces a fundamental change to the heat equation, gives rise to oscillatory motions. The linear stability of the layer can then take the form of steady or oscillatory motion. The stability boundary shows that the oscillatory stability boundary bifurcates from that of the steady mode to develop a situation of lower energy for instability. The presence of microporosity tends to inhibit the instability of oscillatory motions and introduces a mean flux that is uniform across the layer. A formal nonlinear analysis leads to two coupled evolution equations of the Landau-Stuart form, for two linearly preferred oscillatory waves propagating in opposite directions. The equations reduce to one for the steady mode. It is shown that the linearly unstable modes can take one of four types of nonlinear growth: supercritical stability, nonlinear instability, subcritical instability, or stability, depending on the relative values of the medium parameters. Although the two amplitudes start to grow interactively, the supercritical solutions always occur in the form of one amplitude, while the other dies out. However, the solution is different from that obtained by considering each wave separately.

Evaluation of the Isomerization of α-Pinene Epoxide to Campholenic Aldehyde Using a Catalyst Obtained from Orange Peels (Citrus sinensis)

Orange peels (Citrus sinensis) are an abundant lignocellulosic residue that can be used as a carbon source to obtain solids with catalytic potential in the transformation of terpenes and their oxides into value-added products. This research seeks to evaluate the isomerization of α-pinene epoxide to campholenic aldehyde using a catalyst obtained from orange peels. The material OAC-Zn was obtained by activation of orange peel with ZnSO4.7H2O followed by thermal treatment at 500 °C; an additional solid was obtained from orange peel by pyrolysis at 500 °C (OC-500). XRD revealed the presence of ZnO and ZnS in OAC-Zn; TGA analysis indicated thermal stability in OAC-Zn and OC-500 materials; SEM images showed porous surfaces of different morphology, and the presence of microporosity in OC-500 and mesoporosity in the OAC-Zn that was confirmed by physical nitrogen adsorption. The elements C, O, Zn and S was identified in OAC-Zn by EDX analysis. The results of TPD-NH3 showed that the solids contained medium and weak acidity. Campholenic aldehyde was synthesized with a 96 % selectivity over a mesoporous carbonaceous material obtained from orange peels using ZnSO4.7H2O as activating agent

Prospective carbon nanofibers based on polymer of intrinsic microporosity (PIM-1): Pore structure regulation for higher carbon sequestration and renewable energy source applications

Polymer of intrinsic microporosity (PIM-1) is characterized by a developed microporous structure. Needle-free Nanospider™ electrospinning of the PIM-1 solution with subsequent pyrolysis either under vacuum or in argon-hydrogen medium (7 vol% H2) at 900–1200 °C results in PIM-1 based carbon nanofibers (CNF) self-supporting mats. The samples were thoroughly characterized by N2 and CO2 adsorption using the BET, BJH, Dubinin-Radushkevich (DR), NLDFT and GCMC methods, CO2 uptake, and by Raman spectroscopy, elemental analysis, electrical conductivity, SEM. Since the N2 adsorption is found to be inapplicable, the presence of microporosity in the CNF is confirmed by CO2 adsorption (273 K) by the DR, NLDFT and GCMC methods. The CNF reach micropore specific surface area of 919 m2 g−1, micropore volume of 0.257 cm3 g−1 and CO2 uptake of 4.01 mmol g−1, which is higher than for initial PIM-1. Pt/PIM-1 CNF self-supporting mat, was successfully tested as anode for HT-PEM fuel cell.

Mechanical and stress corrosion cracking behavior of welded 5059H116 alloy

5059H116 alloy is welded by friction stir welding (FSW) and gas metal arc welding (GMAW). Both welded specimens exhibited inferior strength and percent elongation as compared to base alloy. Soundness of the weld, passivating tendency of finer grains, and depletion of dissolved magnesium from the nugget zone due to discontinuous precipitation of Al3Mg2 phase at the Al6Mn/matrix interface contributed to the superior corrosion resistance of FSW alloy. Slow strain rate tests showed shorter time to failure for GMAW sample, which is attributed to the formation of microcells from chemical heterogeneities and iron-containing second phase dispersoids, and presence of micro-porosity. Data availability statementThe raw/processed data required to reproduce these findings cannot be shared at this time due to technical or time limitations.

Screening of Surfactants for Flooding at High-Mineralization Conditions: Two Production Zones of Carbonate Reservoir

The selection of effective surfactants potentially can mobilize oil up to 50% of residuals in mature carbonate oilfields. Surfactants’ screening for such oilfields usually is complicated by the high salinity of water, high lipophilicity of the rock surface, and the heterogeneous structure. A consideration of features of the oilfield properties, as well as separate production zones, can increase the deep insight of surfactants’ influence and increase the effectiveness of surfactant flooding. This article is devoted to the screening of surfactants for two production zones (Bashkirian and Vereian) of the Ivinskoe carbonate oilfield with high water salinity and heterogeneity. The standard core study of both production zones revealed no significant differences in permeability and porosity. On the other hand, an X-ray study of core samples showed differences in their structure and the presence of microporosity in the Bashkirian stage. The effectiveness of four different types of surfactants and surfactant blends were evaluated for both production zones by two different oil displacement mechanisms: spontaneous imbibition and filtration experiments. Results showed the higher effect of surfactants on wettability alteration and imbibition mechanisms for the Bashkirian cores with microporosity and a higher oil displacement factor in the flooding experiments for the Vereian homogeneous cores with lower oil viscosity.

A comprehensive perspective on pore connectivity and natural fracture analysis in Oligo-Miocene heterogeneous carbonates, southern Iran

Ascertaining the pore connection criterion has always been a challenge for geoscientists. In the framework of this research, an attempt was made to study the pore connectivity in a heterogeneous carbonate rock by combining several techniques. Pore types and rock facies were investigated for 321 thin sections. The abundance of connected porosities, cementation type and intensity which significantly control the matrix pore connectivity were specified on thin sections and finally a connectivity log was extracted that showed an accurate result on poro-perm cross-plots. Most of the porosity volumes were related to interparticle, vuggy and moldic porosities which are microscale. The velocity deviation log, estimated in four wells, indicates the presence of micro-porosity, which is consistent with the results of thin-sections. Zero velocity deviation is usually associated with the predominant presence of micro-pores. Different permeability values in identical lithological facies, as well as micro-fracture markers, prompted us to conduct more extensive research on fractures. FMI analysis proved that the studied reservoir is intensively fractured. The recorded high permeability in a sample with low matrix connectivity is specifically a fracture indication. Fracture apertures vary from microscale (<50 μm) to 12.5 mm and calculated fracture density is raised up to 2 fractures per meter. Determined fractured intervals are very consistent with mud-loss information, for instance, a complete loss has been reported in the fault zone identified in well B. The detected fractures somewhat follow the main Zagros fault trend (NW-SE). Eventually, calculated connectivity was predicted in other wells using Artificial Neural Network (ANN) and a 3D model was constructed with respect to seismic attributes which gives a precise perspective of pore connection distribution throughout the studied field.

How Nanopores Influence Dry-Frame VP Pressure Sensitivity

This paper investigates how nanopore size distribution influences dry-frame P-wave velocity (VP) pressure sensitivity. The study uses a set of twenty-three samples belonging to a single vertical core from the Mississippian-age Meramec formation of the mid-continent US. Individual samples had their facies interpreted, composition estimated, He-gas porosity (ΦHe) determined, and P-wave and S-wave transit times systematically measured for dry core-plugs in a 5–40 MPa loading and unloading cycle. Data from the unloading cycle were linearized in the log scale, and the slope of the best fitting line was considered as a representative of the dry-frame VP pressure sensitivity. A series of photomicrographs from each sample were analyzed using image processing methods to obtain the shape and size of the individual pores, which were mostly in the nanopore (10−6–10–9 m) scale. At the outset, the pore-shape distribution plots were used to identify and discard samples with excessive cracks and complex pores. When the remaining samples were compared, it was found that within the same facies and pore-shape distribution subgroups VP pressure sensitivity increased as the dominant pore-size became smaller. This was largely independent of ΦHe and composition. The paper postulates that at the nanopore scale in the Meramec formation, pores are mostly isolated, and an increase in the confining pressure increased the bulk moduli of the fluids in the isolated pores, which in turn increased the VP pressure sensitivity. The study proposes incorporating this effect quantitatively through a dual-fluid model where the part of the fluid in unconnected pores is considered compressible while the remaining is considered incompressible. Results start to explain the universal observation of why the presence of microporosity quintessentially enhances VP pressure sensitivity.

Experimental Investigation of Friction Pressure Influence on the Characterizations of Friction Welding Joint for AISI 316

This study focuses on the effect of friction pressure on the welding joint strength of AISI 316. Single factor method was used to evaluate the influence of friction pressure, whilst the other conditions kept constant. The experimental data were achieved by temperature measurement using infrared thermometer and thermometer by touch, where hardness Hv10 and micro-hardness Hv0.1 realized along the axial direction, tensile test specimen with 8 mm effective diameter, scanning electronic microscopy (SEM) to observe tensile fracture surface and x-ray diffraction (XRD) to analyze the concentration of gamma iron. The results by high friction pressure provide increased temperature during friction and forging phase, elevated hardness and micro-hardness values at the welding center, improved ductility and ultimate tensile strength (UTS). Whilst the central region of tensile fracture seemed most ductile mode and presence of micro-porosities with different forms and dimensions, hence concentration of face centered cubic (FCC) structure of gamma iron clearly revealed at level of 111.

Effect of Chemical Vapor Infiltration Induced Matrix Porosity on the Mechanical Behavior of Ceramic Matrix Minicomposites

Abstract Ceramic matrix composites (CMCs) exhibit process-induced defects such as matrix porosity at multiple length scales that have a considerable influence on their mechanical and failure behavior. This work focuses on the microscale mechanical behavior of single tow CMCs in the presence of microporosities that exist within fiber bundles of the composite. Microporosities in a single tow C/boron nitride (BN)/SiC CMC minicomposite fabricated by chemical vapor infiltration (CVI) have been characterized by X-ray microcomputed tomography. The porosity distribution in the scanned region has been represented by probability distribution functions (PDFs) that serve as an input to numerical homogenization. Effective elastic properties in the presence of matrix micropores have been obtained by a two-step numerical homogenization approach considering the statistical distributions of pore parameters obtained from experimental characterization. A variation of the approach has been utilized to investigate the severity of pores with respect to their location and orientation relative to the fiber reinforcement.

Conductive Carbon Materials from the Hydrothermal Carbonization of Vineyard Residues for the Application in Electrochemical Double-Layer Capacitors (EDLCs) and Direct Carbon Fuel Cells (DCFCs).

This study investigates the production of bio-based carbon materials for energy storage and conversion devices based on two different vineyard residues (pruning, pomace) and cellulose as a model biomass. Three different char categories were produced via pyrolysis at 900 °C for 2 h (biochars, BC), hydrothermal carbonization (HTC) (at 220, 240 or 260 °C) with different reaction times (60, 120 or 300 min) (hydrochars, HC), or HTC plus pyrolysis (pyrolyzed hydrochars, PHC). Physicochemical, structural, and electrical properties of the chars were assessed by elemental and proximate analysis, gas adsorption surface analysis with N2 and CO2, compression ratio, bulk density, and electrical conductivity (EC) measurements. Thermogravimetric analysis allowed conclusions to be made about the thermochemical conversion processes. Taking into consideration the required material properties for the application in electrochemical double-layer capacitors (EDLC) or in a direct carbon fuel cell (DCFC), the suitability of the obtained materials for each application is discussed. Promising materials with surface areas up to 711 m2 g−1 and presence of microporosity have been produced. It is shown that HTC plus pyrolysis from cellulose and pruning leads to better properties regarding aromatic carbon structures, carbon content (>90 wt.%), EC (up to 179 S m−1), and porosity compared to one-step treatments, resulting in suitable materials for an EDLC application. The one-step pyrolysis process and the resulting chars with lower carbon contents and low EC values between 51 and 56 S m−1 are preferred for DCFC applications. To conclude, biomass potentials can be exploited by producing tailored biomass-derived carbon materials via different carbonization processes for a wide range of applications in the field of energy storage and conversion.

Preparation and evaluation of nitrogen-tailored hierarchical meso-/micro-porous activated carbon for CO2 adsorption

ABSTRACT In this study, nitrogen-tailored hierarchical meso-/micro-porous activated carbons were successfully fabricated from cypress sawdust by H3PO4 activation with further nitrogen modification using three kinds of nitrogen source (i.e. nitic acid, urea and melamine). The produced carbons were used as adsorbents for CO2 capture. The physic-chemical properties of the produced carbons were characterized by N2 adsorption-desorption, fourier-transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The effects of pore structure and nitrogen content on CO2 adsorption were investigated. It was found that H3PO4 activation would turn cypress sawdust into mesoporous carbon (AC), nitrogen doping could induce the development of microporosity and also increase the basicity of the carbon framework, which favoured for CO2 adsorption. Among the nitrogen-tailed carbons, HNO3-treated activated carbon (AC–N) showed the highest V mic (0.127 cm3/g), the largest CO2 adsorption capacity (2.8 mmol/g at 273 K, 1 bar) and the best CO2/N2 selectivity as compared to urea and melamine treated ones. The adsorption experiments showed that the presence of microporosity and pyrrolic-N on the carbons were responsible for CO2 adsorption, the oxygen functional groups on AC–N might also contribute to higher CO2 uptake, and the mesoporous structure could favour for the fast mass transfer of CO2. The results of CO2 adsorption heat confirmed the high affinity of the prepared carbons to CO2. This study provides a strategy to produce hierarchical meso-/micro-porous activated carbons with enriched nitrogen functional groups, which favoured for CO2 adsorption.

New approach towards the classification of microporosity in Miocene carbonate rocks, Central Luconia, offshore Sarawak, Malaysia

Microporosity is recognized as a significant concern in limestone reservoirs throughout the world because it presence can highly complicate the hydrocarbon estimation and production. Numerous studies around the globe emphasises on the physical appearance, occurrence, and abundance of microporosity, but no published study has been emphasises on the presence of microporosity in Miocene carbonate reservoirs. Miocene carbonates from Central Luconia, offshore Sarawak, Malaysia, contains a significant amount of micropores, which occurs in grain, matrix, and cement. For a better understanding of the presence of micropores, it is necessary to consider grains, matrix, cement, and pore types. Based on the qualitative and quantitative knowledge of these components a classification of micropores is proposed and their effect on reservoir quality. These results can reduce the number of the assumption made about the internal rock connectivity and quality.For quantitative analysis, 32 high-resolution images of each thin sections were taken under the transmitted light microscopy. Succeeding these 32 images were stacked together as a photo panel to enable quantifying the amount of grain, matrix, cement, pore types and macroporosity using Digital Image Analysis and J.Microvision software. Furthermore, Field Emission Scanning Electron Microscopy images were also used for the measurement of crystallometry of micrite particles, classification of micrite particles and the micropores.Eight facies scheme is introduced based on the detailed lithofacies study of five wells. The qualitative observation of thin sections unveiled that corals, red algae, green algae, foraminifera, echinoderms, sponge, bivalve, and bryozoans are the most dominant components. Foraminifera, red algae, and corals are the far most dominant components covering almost 50% of the total intervals. Regarding porosity types, the mouldic porosity is the far most dominant pore types with converting the total 50% of the interval. Lithofacies observed in these wells indicate a good reservoir quality, but diagenesis plays a vital role in enhancing or reducing their porosity and permeability. Most of the depositional textures of the reservoir are leached, making this location unique to study facies distribution and diagenetic history.Result exhibits that the micrite particles are classified into five classes, which are very fine, fine, medium, coarse and very coarse, with a diameter of 0.1–2 μm, 2–4 μm, 4–6 μm, 6–8 μm and 8–10 μm respectively. The texture and morphology of micrite microtexture are classified into six classes. Among these six classes, rounded, subrounded, trigonal, rhombic (micro-sub)-polyhedral micrite are representing porous micrite particles, whereas fitted bounded subhedral, and fitted fused anhedral are interpreted as tight micrite particles. Furthermore, five micropores classes are introduced based on the size of these particles. The empirical porosity-permeability relationship is affected by the presence of microporosity and its influences the assessment of ultimate recovery of hydrocarbons in Central Luconia, offshore Sarawak, Malaysia.

Presence of microporosity in Miocene carbonate platform, Central Luconia, offshore Sarawak, Malaysia

The Luconia Province—offshore Sarawak—is a key hydrocarbon province in Malaysia. However, the gas reservoirs in Central Luconia pose unique problems and challenges as they have partially water-filled microporosity that overprint wireline logs. Microporosity in Central Luconia occurs throughout the Miocene carbonates and is a crucial element that influences fluid flow properties and ultimately the recovery of hydrocarbons. Quantification of macroporosity was achieved using petrographic analysis of thin sections and the FESEM images. The point counting technique was used to estimate the amount of macroporosity from the thin section, which was then subtracted from the total porosity to derive microporosity. The qualitative investigation of the Miocene carbonates indicates the presence of three different types of microporosity namely grain-based microporosity, matrix-based microporosity, and cement-based microporosity. Quantification of microporosity showed that the microporosity varies from sample to sample, ranging from 10 to 60% of the total measured porosity. The depositional texture, mineralogy, and microtexture control this microporosity variation including its abundance and type. The microporosity in Central Luconia is diagenetically controlled based on four major diagenetic mechanisms namely (1) mechanical process/endolithic grains/marine diagenesis; (2) leaching/meteoric diagenesis; (3) cementation/shallow diagenesis; and (4) deeper diagenesis environment.

Evaluation of the accuracy of a modified microtensile test using micro-specimens

Purposeto evaluate the accuracy of a modified method of microtensile test (μTBS) through the performing of micro specimens (cross section 0.09 mm2) and to evaluate the interfacial integrity by confocal laser microscopy (CLSM). Material and methodstwo bond agents, Clearfil SE Bond and Scotchbond Multipurpose Plus were applied to flat dentin substrate of 32 human premolars and composite crowns were built up with Charisma Opal. The restored teeth were sectioned to produce beam-shaped specimens by diamond saw. For display in CLSM, 0.16 mg/ml of Rhodamine B was incorporated into adhesives thus forming two groups for each adhesive (n = 8) groups of teeth restored with adhesives stained and unstained. The presence of microporosities was recorded in CLSM before testing μTBS. The failure patterns were analyzed using SEM. Data of bond strength was submitted to two-way ANOVA. Resultsthe results showed bond strength data with low rate of premature failure, high percentage of failures at the actual interface (90%) and low coefficient of variation. No significant difference were observed between the specimens mean values of stained and unstained adhesives (p > 0.05). The CLSM revealed detailed information of the adhesive interface, showing low percentage of microporosities for both bonding agents. Conclusionbased on the results of different test parameters it can be inferred that the modified microtensile test performed with micro specimens, shown reliable and could be considered a valid method.

Solidification microstructure of centrifugally cast Inconel 625

Centrifugal casting is a foundry process allowing the production of near net-shaped axially symmetrical components. The present study focuses on the microstructural characterization of centrifugally cast alloys featuring different chemical compositions for the construction of spheres applied in valves made of alloy IN625 for operation at high pressure. Control of the solidification microstructure is needed to assure the reliability of the castings. Actually, a Ni-base superalloy such as this one should have an outstanding combination of mechanical properties, high temperature stability and corrosion resistance. Alloys such as IN625 are characterised by a large amount of alloying elements and a wide solidification range, so they can be affected by micro-porosity defects, related to the shrinkage difference between the matrix and the secondary reinforcing phases (Nb-rich carbides and Laves phase). In this study, the microstructure characterization was performed as a function of the applied heat treatments and it was coupled with a calorimetric analysis in order to understand the mechanism ruling the formation of micro-porosities that can assure alloy soundness. The obtained results show that the presence of micro-porosities is governed by morphology and by the size of the secondary phases, and the presence of the observed secondary phases is detrimental to corrosion resistance.

Geochemical and textural characterization of phosphate accessory phases in the vein assemblage and metasomatically altered Llallagua tin porphyry

Petrographic and geochemical characterization of phosphate accessory minerals represents a powerful tool in understanding the mineralization and metasomatic history of one of the world’s biggest tin deposits, the Siglo XX mine, Salvadora stock, Llallagua, Bolivia. The Llallagua tin deposit lies in a hydrothermally altered porphyry stock that is part of the subduction-related Bolivian tin belt. Despite numerous studies, there is still a debate over the timing and characteristics of mineralization history of the deposit. Primary igneous fluorapatite and monazite (for the first time) were recognized in the altered porphyry. The igneous monazite is enriched in Th, unlike the hydrothermal monazite that is recognized for its low Th concentration. Fluorapatite, monazite, and xenotime also coexist with cassiterite within the hydrothermal vein assemblage. Fluorapatite and xenotime are essentially pristine. Monazite, however, shows various degrees of alteration in the form of regenerative mineral replacement (RMR). This exemplifies differential reactivity and selective mineral replacement/alteration of three accessory phosphate minerals, that are all important geochemical tracers of magmatic and hydrothermal processes, and which can all be used as geochronometers. Mineral textures and composition in the altered porphyry and vein assemblages have been evaluated. Monazite-xenotime geothermometry indicates monazite crystallization beginning around 550 °C. Monazite continues to grow as temperatures gradually decrease to about 300 °C, when most of cassiterite precipitation occurred in the samples studied. The primary mechanism of phosphate alteration has been identified as a coupled dissolution-reprecipitation process, which led to REE exchange in the igneous fluorapatite and hydrothermal monazite. In Type I local alteration, La and Pr-Nd show continuity across the pre- and post- alteration concentric zones indicating that they were not affected by alteration. This is an example of a selective elemental exchange during coupled dissolution-precipitation. Type II, pervasive post-growth alteration, is evident by the presence of micro-porosity and the formation of secondary, reaction induced minerals. Release of HREE from the monazite goes into the formation of void filling xenotime inclusions; the first documentation of this metasomatic alteration product in monazite. A well-documented discrepancy exists among ages determined from the zircon, fluorapatite, monazite, and altered porphyry minerals. These observations, regarding selective alteration of fluorapatite and monazite, may help to elucidate the reasons for this discrepancy.

A cohesive approach at estimating water saturation in a low-resistivity pay carbonate reservoir and its validation

Carbonate reservoir characterization and fluid quantification seem more challenging than those of sandstone reservoirs. The intricacy in the estimation of accurate hydrocarbon saturation is owed to their complex and heterogeneous pore structures, and mineralogy. Traditionally, resistivity-based logs are used to identify pay intervals based on the resistivity contrast between reservoir fluids. However, few pay intervals show reservoir fluids of similar resistivity which weaken reliance on the hydrocarbon saturation quantified from logs taken from such intervals. The potential of such intervals is sometimes neglected. In this case, the studied reservoir showed low resistivity. High water saturation was estimated, while downhole fluid analysis identified mobile oil, and the formation produced dry or nearly dry oil. Because of the complexity of Low-resitivity pay (LRP) reservoirs, its cause should be determined a prior to applying a solution. Several reasons were identified to be responsible for this phenomenon from the integration of thin section, nuclear magnetic resonance (NMR) and mercury injection capillary pressure (MICP) data—among which were the presence of microporosity, fractures, paramagnetic minerals, and deep conductive borehole mud invasion. In this paper, we integrated various information coming from geology (e.g., thin section, X-ray diffraction (XRD)), formation pressure and well production tests, NMR, MICP, and Dean–Stark data. We discussed the observed variations in quantifying water saturation in LRP interval and their related discrepancies. The nonresistivity-based methods, used in this study, are Sigma log, capillary pressure-based (MICP, centrifuge, and porous plate), and Dean–Stark measurements. The successful integration of these saturation estimation methods captured the uncertainty and improved our understanding of the reservoir properties. This enhanced our capability to develop a robust and reliable saturation model. This model was validated with data acquired from a newly drilled appraisal well, which affirmed a deeper free water level as compared to the previous prognosis, hence an oil pool extension. Further analysis confirmed that the major causes of LRP in the studied reservoir were the presence of microporosity and high saline mud invasion. The integration of data from these various sources added confidence to the estimation of water saturation in the studied reservoir and thus improved reserves estimation and generated reservoir simulation for accurate history matching, production forecasting, and optimized field development plan.

Acidic mesostructured silica-carbon nanocomposite catalysts for biofuels and chemicals synthesis from sugars in alcoholic solutions

Sulfonated mesostructured silica-carbon nanocomposites with varying carbon content, acidic site density and porosity, obtained via the one-pot evaporation induced self-assembly (EISA) synthesis, were used here to convert sugars into useful chemicals and biofuel components in alcoholic solvent. The nanocomposites show a remarkable catalytic performance in ethanol, yielding up to 80%, predominantly ethyl levulinate, 5-ethoxymethylfurfural and 2-(diethoxymethyl)-5-(ethoxymethyl)furan. Fructose is the sugar substrate of choice, but the sulfonated composites are also able to convert di- and polymeric forms of fructose. Due to a lack of a glucose-to-fructose isomerization ability, the composites are unable to form the above products from the glucose resources (glucose and cellulose), ethyl glucoside being the dominant product from these feedstocks. The composite has a peculiar hierarchical pore architecture, which is stable on shelf in ambient for at least six years. While the mesoporosity facilitates entrance and fast transport (even of soluble poly-carbohydrates like inulin and cellulose polymers), the presence of microporosity is beneficial to attain fast sugar catalysis. Since the microporosity is associated with voids in the carbon phase (preferably pyrolyzed at 400°C), composites with high carbon contents are preferred. Due to the fast transport, reactions with fructose in ethanol run in the chemical regime in the applied thermal conditions. Kinetic inspection of the reaction further clarifies the complex network of consequent and parallel reactions, demonstrating that HMF is the main precursor of humins, while the formation of EL directly from HMF should also be considered. While this observation corroborates the protective role of alcohols like ethanol, this work also concludes based on a series of reactions in different alcohols and water, that the presence of water plays a crucial role in the HMF-to-humins formation. While alcohols are known to stabilize HMF, the unprotected HMF is fairly stable in non-aqueous reaction circumstances like in tert-butanol solvent.