Interparticle Porosity Research Articles

Experimental Study on Factors Affecting Fracture Conductivity

The conductivity of propped fractures following hydraulic fracturing is crucial in determining the success of the fracturing process. Understanding the primary factors affecting fracture conductivity and uncovering their impact patterns are essential for guiding the selection of fracturing engineering parameters. We conducted experiments to test fracture conductivity and analyzed the effects of proppant particle size, closure pressure, and fracture surface properties on conductivity. Using the orthogonal experimental method, we clarified the primary and secondary relationships of the influencing factors on conductivity. The results indicate that proppant particle size, formation closure pressure, and fracture surface properties significantly affect fracture conductivity, with the order of influence being closure pressure > fracture surface properties > proppant particle size. Using large-particle-size proppants effectively increases interparticle porosity and enhances fracture conductivity. However, large-particle-size proppants reduce the number of contact points between particles, increasing the pressure on individual particles and making them more prone to crushing, which decreases fracture conductivity. Proppants become compacted under closure pressure, leading to a reduction in fracture conductivity. Proppant particles can embed into the fracture surface under closure pressure, further impacting fracture conductivity. Compared to non-laminated fracture surfaces, proppant particles are more likely to embed into laminated fracture surfaces under closure pressure, resulting in a greater embedding depth and reduced conductivity.

Microfacies and Depositional Environments Analyses of the Hartha Formation at Balad Oil Field, Central Iraq

The Hartha Formation (Late Campanian-Maastrichtian) has been recognized as a potential reservoir for hydrocarbons in various oilfields within the Mesopotamian basin in central Iraq. The formation has conformable upper contact with the overlying Shiranish Formation but unconformable lower contact with the underlying Mushorah Formation. This formation has been stratigraphically divided into two main parts. The lower part is particularly significant as it is recognized as an important stratigraphic unit due to the presence of oil shows. Five subsurface sections and many thin sections of the Hartha Formation (Late Campanian-Maastrichtian) were studied to unravel the depositional facies and environments. The sedimentary microfacies of the Hartha Formation in the Balad oil field include mudstone, wackestone, wackestone to packstone, packstone, Packstone to Grainstone, and Rudstone. These depositional microfacies have been subdivided according to their primary and diagenetic constituents into six sub-microfacies. The microfacies have been deposited in deep shelf margin, open shelf, and foreslope of varying salinities and energy levels. Cementation, dolomitization, compaction and pressure solution (stylolitization ), and dissolution are observed affecting variably both ground mass and particles. These diagenetic processes have both positive and negative effects on porosity types, causing fluctuations in porosity levels. The primary pore types identified within the study wells include interparticle porosity, intercrystal porosity, moldic porosity, vuggy porosity, channel porosity, and fracture porosity.

A microstructural insight into the compression behaviour of scaly clays

Scaly clays are intensely fissured clays with lens-shaped elements of millimetre size and they show a complex compression behaviour that poses challenges to the design and construction of geostructures (excavations, retaining diaphragms and tunnels). Scaly clays show a normal compression line (NCL) where plastic deformation accumulates, as typically observed in non-scaly clays. Yet the response observed upon unloading and subsequent reloading is very peculiar, (a) the unloading–reloading cycle is typically a closed loop with relatively large hysteresis; (b) the compressibility recorded at high overconsolidation ratio of the unloading or reloading branches is close to the NCL compressibility. This paper presents a microstructural study on an Italian scaly clay where scanning electron microscope observations are integrated with mercury intrusion porosimetry analyses and X-ray computed tomography images. The mechanism associated with the closing of inter-scale porosity and the generation of new intra-scale porosity was identified as the process responsible for the plastic deformation. Experimental observation of reconstituted clay showed a ‘quasi-reversible’ behaviour upon loading and unloading and a pore size distribution characterised only by interparticle porosity. The observation that unloading and reloading curves are parallel in natural and reconstituted clays, led to the postulation that the interparticle porosity is controlling the elastic response.

Influence of salinity gradients on the diffusion of water and ionic species in dual porosity clay samples

Most of the available data on diffusion in natural clayey rocks consider tracer diffusion in the absence of a salinity gradient despite the fact that such gradients are frequently found in natural and engineered subsurface environments. To assess the role of such gradients on the diffusion properties of clayey materials, through-diffusion experiments were carried out in the presence and absence of a salinity gradient using salt-diffusion and radioisotope tracer techniques. The experiments were carried out with vermiculite samples that contained equal proportions of interparticle and interlayer porosities so as to assess also the role played by the two types of porosities on the diffusion of water and ions. Data were interpreted using both a classical Fickian diffusion model and with a reactive transport code, CrunchClay that can handle multi-porosity diffusion processes in the presence of charged surfaces. By combining experimental and simulated data, we demonstrated that (i) the flux of water diffusing through vermiculite interlayer porosity was minor compared to that diffusing through the interparticle porosity, and (ii) a model considering at least three types of porous volumes (interlayer, interparticle diffuse layer, and bulk interparticle) was necessary to reproduce consistently the variations of neutral and charged species diffusion as a function of salinity gradient conditions.

Monoliths for gas storage manufactured with precision pore engineering using 3D-printed templates

A fast, customizable, and systematic route for producing activated carbon monoliths for gas storage with low interparticle porosity (9 % to 24 %) containing tailored macro channels is disclosed. The production uses a three-dimensional (3D)-printed polymeric lattice, rich in oxygen, as a sacrificial template. Its interstitial voids are filled with a phenolic resin that is carbonized and activated at 1173 K under carbon dioxide (CO2). Sequential pyrolysis occurs via thermal treatment with the 3D-printed lattice removed first, rendering macro channels with the same shape as the template in accurately placed positions. Resulting in adsorbents with interparticle porosities ranging from 10 % to 23 %, calculated from X-ray micro-computed tomography (micro-CT) images. The axial resolution of these macro channels was similar to the SLA printing layer thickness used of 100 µm. Making it the best resolution attained to date in fabricating monoliths via a 3D-printed sacrificial templating method. Breakthrough experiments indicated healthy macro channel connectivity due to the reduced mass transfer zone. Moreover, excellent mechanical integrity was displayed, with a monolith withstanding 900 N before excessive fracturing occurred despite the presence of macro channels. Therefore, this method emphasizes its use for gas storage applications by enabling the adsorbent material to efficiently utilize the volumetric space while allowing a fast rate of adsorption over the entire structure.

New insights into estimating the cementation exponent of the tight and deep carbonate pore systems via rigorous numerical strategies

One of the main constituents of any reservoir characterization is an accurate forecast of water saturation, which is highly dependent upon the cementation exponent. Even though there have been a lot of studies, the most common correlations depend on total porosity. This means that they do not work as well in heterogeneous carbonate reservoirs, especially tight formations with total porosities less than 10%. This study aims to develop accurate and universal models for estimating the cementation exponent in deep and tight carbonate pore systems located in West Asia. Two heuristic algorithms, including the radial basis function neural network optimized by ant colony optimization (RBFNN-ACO) and gene expression programming (GEP), were employed to calculate the cementation exponent. To do this, we prepared a databank incorporating cementation exponents, total porosity, and various pore types. Then, the databank is classified into the test subset (for model prediction checking) and the train subset (for model construction). The reliability of the new recommended models is inspected by applying several statistical quality measures associated with graphical analyses. So, the consequences of the modeling disclose the large precision of the above-mentioned RBFNN-ACO, GEP Model-I, and GEP Model-II by average absolute percentage relative deviations (AAPRD%) of 6.28%, 6.39%, and 7.45%, respectively. Based on the outliers analysis, nearly 95% of the databank and model estimations are, respectively, valid and reliable. Additionally, the three input variables, including moldic porosity (with a + 70% impact value), non-fabric-selective dissolution (connected) porosity (with a -30% impact value), and interparticle porosity (with a -23% impact value), exhibit the main affecting parameters on the cementation exponent. Comparing current results with traditional literature correlations demonstrates the supremacy of the RBFNN-ACO model (AAPRD = 6.28% and root mean squared error (RMSE) = 0.17) over the examined literature correlations such as Borai’s equation (AAPRD = 12.30% and RMSE = 0.41). In addition, RBFNN-ACO can give better results than Borai’s Eqn. for tight (porosity less than 10%) and deep carbonate samples.

Automated processing of well logging data to monitor the position of the gas-water contact in underground gas storage facilities

Natural oil and gas deposits in most fields include some fluid contacts, such as oil–water, gas–water, or gas–oil. Monitoring the position of the gas–water contact in underground gas storage (UGS) facilities is crucial for monitoring the safety of the subsurface environment. As UGS facilities are geological features of long-term operation, the condition of these features must be regularly monitored for possible gas leaks due to various reasons, whether geological or technical. Periodic surveys of production wells using geophysical methods make it possible to timely detect the reasons for abnormal technical conditions and higher-than-normal water cuts of reservoirs, and to assess shifts in gas–water contact. The suite of production logging methods for surveying and monitoring underground gas storage facilities includes nuclear logging with the use of steady radiation sources (i.e., gamma ray logging and neutron logging). Analysis and interpretation of these methods make it possible to track the shift over time of the gas–water contact in gas-saturated sandstones with an interparticle porosity of >15%. Data from nuclear logging, temperature logs, and composition-based and flow-based surveying are processed and interpreted with the use of known methods and diagnostic indicators to achieve the following goals: to determine the intervals of inter-reservoir and behind-the-casing fluid movement on the base of the well log, to assess the technical condition of the wellbore, to monitor the position of the gas–water contact in the reservoir, to assess the gas saturation of the reservoir, and to monitor the thickness and integrity of the clay caprocks of UGS facilities [1]. This paper discusses the results of automated processing and interpretation of well data recorded during the survey of an UGS facility to determine the current position of the gas–water contact in the reservoir and the gas–water interface in the well. Quantitative interpretation of the neutron logging data with the use of steady radiation sources was performed, and the current gas saturation factor was estimated. Keywords: gas–water contact (GWC); gas saturation; underground gas storage; processing algorithm; gas–water interface (GWI).

Mobility of water and ions in partially water-saturated compacted MX-80 bentonite in relation with swelling pressure

Many countries are planning to host long-lived high- and intermediate-level radioactive waste in disposal facilities sited in deep argillaceous formations. Bentonite, as a swelling material, is often chosen as engineered buffers due to its low permeability and high swelling capacity. However, its properties can be influenced by the hydraulic/gas conditions prevailing in-situ that are expected to change throughout the duration of the repository. The objective of this work is to estimate the effect of partially water-saturated conditions on the mobility of water and ions in compacted MX-80 bentonite in relation to the evolution of its swelling pressure. For that purpose, (i) diffusion of water and ions (I− and Na+) and (ii) the swelling pressure of compacted bentonite samples partially water-saturated were studied by means of the osmotic technique that allows controlling the suction from 9 to 0 MPa.Results showed that (i) water diffusivity remained unchanged independently of the degrees of saturation (70, 84 and 100%) and (ii) iodide diffusivity decreased by a factor of 12 (from 100 to 70%), while (iii) Na+ diffusion was reduced by a factor of more than 70 (from 100 to 70%), associated to a drop of the distribution factor by a factor of 16. Comparison of these results with diffusion data already acquired in clayey materials whose porous structure evolves little with suction (i.e. compacted kaolinite and intact Collovo-oxfordian clay-rocks) underlined how the bentonite porous structure whose organization evolved with the degree of saturation is a key parameter. This statement is supported by mechanical tests, which indicated a distinct evolution of the swelling pressure curves depending on the degree of saturation. At 70% saturation, mechanical tests indicate (i) a preservation of the large inter-aggregate porosity where water can diffuse in both vapor and liquid phases, and (ii) a final swelling pressure 1.5 to 2 times lower than at full water saturation, meaning that a part of swelling clay particles was not accessible to water ingress and so to 22Na+. Conversely, at 84 % and 100 % saturation, change in swelling pressure curves was explained by a collapse of bentonite inter-aggregate porosity, in favor of expanding the inter-particle and interlayer porosities where 22Na + diffusion is enhanced by surface diffusion phenomenon.

Quantitative Scrolling into Microporous Nanotubes of the Hydrous Layered Silicate Ilerite

AbstractThe synthetic hydrous layered silicate ilerite was quantitatively converted into microporous nanoscrolls (NS). Delamination of ilerite that was ion‐exchanged for N‐Methyl‐D‐glucaminium (Meg+), through one‐dimensional (1D) dissolution initially yields lamellar liquid crystalline (nematic) suspensions. Subsequent protonation with acetic acid of tangling Si‐O− to silanol groups reduces the pH‐dependent charge of the basal surfaces. Complete NS formation is then triggered by diluting the nematic suspension below 0.05 wt%. As scrolling commonly has been attributed to hydrophobic interaction of organic counterions, Meg+ was replaced by lithium ions but this showed no detrimental effect on the scrolling efficiency. The resulting NS have a typical length of 2–4 μm that corresponds well with typical diameters of the parent nanosheets. Ar‐physisorption isotherms showed a bimodal micropore size with maxima around 0.8 and 1.9 nm. We attribute the first to the tubular hollow inner diameter of the NS and the latter to wedgelike interparticle porosity. The material showed a large specific surface area of 226 m2 g−1.

Petrographical and petrophysical characterization of pre-salt Aptian carbonate reservoirs from the Santos Basin, Brazil

Reservoir quality in carbonates is influenced by various factors such as the depositional environment, burial history and diagenesis processes. Understanding these geological heterogeneities is essential for successful petroleum exploration. This study characterizes Brazilian pre-salt reservoirs and aims to understand how their heterogeneity impacts reservoir quality. We analysed carbonate samples from the Barra Velha Formation (Santos Basin) through an integration of petrographical and core plug descriptions, petrographical facies characterization, porosity and permeability measurements, and image analysis to identify the principal controls on porosity and permeability, pore-size distribution, and groups with similar petrophysical properties using the hydraulic flow unit (HFU) concept. Five facies groups were recognized: Spherulitestone (F1); Shrubstone (F2); Intraclastic Grainstone (F3); Intraclastic Packstone, Spherulitestone with mud and Shrubstone with mud (F4); and Shrub–Spherulite Intercalations and Bioclastic Grainstone (F5). The analysis of porosity and permeability showed that their variations are associated with pore type and cementation rate. Greater contributions of inter-aggregate, interparticle and vugular porosity, combined with a reduced amount of cement, results in higher porosity and permeability but an increase in cement tends to reduce the porosity and permeability. Among the facies groups, F2 and F3 exhibited the best porosities and permeabilities, followed by F1, F4 and F5. From image analysis, small pores (1.5 × 10 −5 –0.01 mm 2 ) are the most common in all rocks. However, these small pores contributed significantly to total porosity only in F4 and some samples of F3. For F2 and F3, the large pores (from 0.01 mm 2 to a maximum of 19.62 mm 2 ) are the main contributors, while F5 has a homogeneous contribution. Finally, the data were grouped into five HFUs: HFU1 and HFU2 represent the zones with the best reservoir quality, primarily composed of F2 and F3.

Diagenetic effect on reservoir quality of siliciclastic and volcaniclastic sandstones from a Paleogene volcanic rifted margin, East Greenland

ABSTRACT Siliciclastic and volcaniclastic sediments in a volcanic rifted-margin succession may experience a complex diagenetic history during burial that can have a large impact on sandstone reservoir properties. To understand such changes, variations in initial sediment composition and succeeding diagenetic changes have been studied for a Paleogene outcrop analogue in the Kangerlussuaq area, East Greenland. The nature of the mafic volcanics-bearing succession, which consists of intra-volcanic sandstones, accommodated over quartz-rich pre-volcanic fluvial sandstones, are comparable to the settings of recently discovered hydrocarbon-producing sandstones in the Faroe–Shetland Basin on the conjugate Atlantic margin. Our petrographic and provenance investigations of the pre- and intra-volcanic sandstones are supported by geochemical and X-ray diffraction analyses. The intra-volcanic sandstones were deposited in shallow marine environments with mixed siliciclastic and volcaniclastic input, the latter rich in felsic to mafic volcanic rock fragments and feldspar grains. Similar zircon age distributions of pre- and intra-volcanic sandstones support a continued supply from the same siliciclastic sediment source after the onset of volcanism. Variations in initial detrital grain and pore-fluid (fresh to marine) compositions resulted in different diagenetic changes in the pre- and intra-volcanic sandstones. However, where siliciclastic sandstones were overlain by volcaniclastic rocks rather than massive lava flows, the diagenetic changes resemble those of the intra-volcanic sandstones. The cementing phases are typically quartz, illite (probably illitized kaolinite), and rare anatase in the pre-volcanic sandstones. Chlorite, calcite, zeolite/feldspar, opal/quartz, and titanite are characteristic authigenic phases in the intra-volcanic sandstones. Precipitation of different minerals in the pre- and intra-volcanic sandstones show that the detrital composition (and to a lesser extent depositional environment) played a major role during early and late diagenesis after deep burial (up to 6–8 km). Inter-eruptive siliciclastic units may prove to form highly valuable reservoirs when they are composed of mixed siliciclastic and volcaniclastic material. In the stratigraphically youngest intra-volcanic sandstones and pre-volcanic sandstones overlain by hyaloclastite or tuff, there is a high potential for preservation of interparticle porosity during burial (< 5 km) due to early chlorite rims and the generation of secondary porosity after the dissolution of early zeolite cement.

Fast time-resolved micro-CT imaging of pharmaceutical tablets: Insights into water uptake and disintegration

We use dynamic micro-computed tomography (micro-CT) with a high temporal resolution to visualize water penetration through the porous network of immediate-release pharmaceutical solid tablets and characterize dynamic swelling and disintegration mechanisms. We process the micro-CT images using two theoretical scenarios that reflect different paths of pore structure evolution: a scenario where tablet porosity remains constant during the swelling process and a scenario where the tablet porosity progressively diminishes and eventually closes during the swelling process. We calculate the time evolution of the volume of water absorbed by the tablet and, specifically, absorbed by the excipients and the pore structure, as well as the formation and evolution of cracks. In turn, the three-dimensional disintegration pattern of the tablets is reconstructed. Restricting attention to the limiting scenario where tablet porosity is assumed fixed during the swelling process, we couple liquid penetration due to capillary pressure described by the Lucas–Washburn theory with the first-order swelling kinetics of the excipients to provide a physical interpretation of the experimental observations. We estimate model parameters that are in agreement with values reported in the literature, and we demonstrate that water penetration is dominated by intra-particle porosity rather than inter-particle porosity.

Carbonate Ramp Facies and Porosity Recognition: Case Study of the Late Albian-Early Cenomanian Mauddud Formation in Ratawi Oilfield, Southern Iraq

The carbonate ramp facies of the Late Albian-Early Cenomanian Mauddud Formation were studied in the Ratawi Oilfield, Basra Governorate, south of Iraq using integrated borehole data set that included, core and cutting samples in three drilled wells to analyze the petrography of the Mauddud Formation, two hundred and eighty-one (281) thin sections were prepared and examined for the three selected wells. The results show that the formation is composed of light grey dolomitized limestone and pseudo-oolitic creamy limestone with green to bluish shale. The petrographic observations results show four facies’ associations in the Mauddud Formation. These include: Mid–Ramp environment which is represented by Argillaceous mudstone microfacies, Argillaceous wackestone microfacies and orbitolinid wackestone microfacies; the shallow open marine environment which is assimilated by foraminiferal wackestone microfacies and foraminiferal packstone microfacies; a restricted marine environment that represented by bioclastic fossiliferous wackestone microfacies and miliolid wackestone microfacies and Shoal environment is represented by bioclastic packstone microfacies, bioclastic grainstone microfacies, peloidal foraminiferal pack-grainstone microfacies, and peloidal packstone-grainstone microfacies with diverse skeletal grains. The porosity includes Vuggy, Interparticle, Intraparticle and Fracture porosity.

Anisotropy in particle orientation controls water diffusion in clay materials

Clay minerals are used in a wide number of natural or artificial materials for municipal or nuclear waste management in which water diffusion is the principal transfer process. However, a quantitative assessment of the impact of the preferred orientation of lamellar clay particles on water diffusion is still lacking. Using 3D Brownian dynamics simulation on representative virtual clay porous media, a systematic study of water diffusion for single-porosity (illite or kaolinite) and dual-porosity (vermiculite) systems was conducted. The simulated water diffusion coefficients were validated through comparison with experiments and were used to build an Archie model including the degree of anisotropy in particle orientation. The results showed that water diffusion can be predicted based on a correct description of the solid phase organization and that clay particle orientation, such as interparticle porosity, is a primary parameter governing water mobility. Moreover, the anisotropy of water diffusion can be linked to the degree of particle preferred orientation, irrespective of the porosity value. The modified version of the Archie model for water diffusion in clay systems proposed here has many potential applications where decoupling of porosity and preferred orientation is needed, including better prediction of water transfers or improved designs of clay liners with sustainable use of natural mineral resources.

Image processing of computed tomography scanned poly-dispersed beds for computational fluid dynamic studies

Achieving our emission reduction goals requires the bulk production of carbon-neutral fuels and chemicals, which are catalytically produced through heterogeneous fixed bed chemical reactors. To optimise and scale-up these reactors, accurate and validated Computational Fluid Dynamics (CFD) models are crucial. Of especial importance to CFD simulations is the accurate depiction of the 3D bed structure used during the experimental setup. A direct one-to-one coupling between experiments and simulations can be achieved by scanning the experimental bed using computed tomography and reconstructing the scanned images as a 3D geometry for CFD simulations. However, processing of the scanned images is necessary to minimise highly coarse features that could impact the overall mesh size. A highly poly-dispersed lab-scale fixed bed reactor, previously scanned and analysed, is processed using various image-processing operations. Depending on the number and the crudeness of the processing operations, the bed is progressively deformed, which impacts both its porosity and its interparticle pore connectivity. The impact of image-processing becomes more evident when the hydrodynamic behaviour, i.e., X-, Y-, and Z-velocity and static pressure, of the beds is explored. CFD simulations revealed highly heterogeneous flow profiles, with the maximum velocity reached being 16-times higher than the average superficial velocity within the bed. Moreover, small modifications in local topological features introduce significant changes to the flow profiles, while the 3D pore interconnectivity was seen to play an equally important role as the interparticle porosity. A particle size study revealed that large particles form less interconnected networks with higher pore volumes, which significantly reduce the flow velocity and the pressure drop experienced by the flow. The generated results yield key insights towards a deeper understanding of the behaviour of fixed bed chemical reactors, highly valuable for catalyst and reactor engineering.

Effect of ceria particle size as intermediate layer for preparation of composite Pd-membranes by electroless pore-plating onto porous stainless-steel supports

The use of H2-selective membranes for ultra-pure H2 production has been assigned as an attractive technology, particularly those based on Pd-films deposited onto porous stainless-steel (PSS) supports. The ability to incorporate thin Pd-films with enough adherence on any internal or external surfaces becomes essential to minimize their complexity and cost while improving their performance. The modification of original PSS substrates with diverse intermediate layers, especially those made of ceria, is presented as a promising alternative. In this context, the current study addresses for the first time the use of different CeO2 particle sizes to generate an intermediate layer and facilitate the subsequent generation of a thin Pd-film by electroless pore-plating (ELP-PP). The membrane containing the smallest CeO2 particle size (membrane S) demonstrated the lowest performance, which was assigned to the high compaction of the material and generation of cracks on its surface during calcination that consequently led to the deposition of a greater amount of Pd. On the other hand, the morphology of membranes M (medium CeO2 particle size) and L (large CeO2 particle size) were very similar, although the first one demonstrated a slightly smaller interparticle porosity, which led to the deposition of a more homogeneous and thinner Pd-film. Therefore, an outstanding performance in terms of H2 permeance (5.98 × 10−4 mol·m−2·s−1·Pa−0.5 at 400 °C) was obtained for this membrane. Permeation tests with binary mixtures (H2-N2, H2-CO2, or H2-CO) revealed a concentration-polarization effect in all cases, as well as a certain inhibition effect in the presence of CO. Finally, it should be highlighted the high stability of the membranes during the entire set of experiments, independently of the considered particle size. Thus, enough mechanical and thermal resistances can be assured for future applications.

Application of unsupervised learning and deep learning for rock type prediction and petrophysical characterization using multi-scale data

This study integrates well log data, routine core analyses, microcomputed X-ray tomography (μCT) images, and sedimentary petrography to accurately characterize and evaluate the carbonate reservoirs of the Barra Velha formation (Aptian) of the Santos Basin within Brazilian pre-salt region. In these carbonate reservoirs, the porous system is extremely diverse and variable, making it challenging to establish rock typing with comparable petrophysical properties. Based on this integrated study, the reservoir sequences were characterized and a precise definition of four reservoir rock types (RRTs) was performed by integrating the petrophysical values from the plugs and their corresponding well log data of two cored wells using K-means unsupervised classification algorithm. The classification results were combined with various conventional techniques to evaluate the quality and geological characteristics of the studied sequence. This evaluation encompassed different parameters such as flow and storage capacity, reservoir quality index, flow zone indicator, pore spaces interpretation, and average pore and throat radius. The study involved a detailed analysis of thin sections to identify various facies, including shrubstones, reworked, and spherulitestone, and to classify various forms of porosity such as interparticle, intraparticle, intercrystalline, vug, moldic, fracture, and growth framework porosity. Pore Network Modeling from μCT analysis of plugs was used specifically for the characterization of pores and throats of plug samples from each RRT. These datasets were utilized as supporting evidence to offer a more accurate and inclusive knowledge of reservoir quality. The study aimed to develop predictive models by implementing deep learning and machine learning algorithms trained on well log data to estimate plug porosity and rock type. Two deep learning models, ResNet and 1D CNN, were trained and evaluated for plug porosity prediction, with the 1D CNN model showing superior performance. Additionally, the XGBoost algorithm was applied to predict rock type, achieving high accuracy on both the training and validation datasets. The predicted results were compared with actual data to evaluate the effectiveness of the models and were then utilized to estimate plug permeability values. The results demonstrate the potential of deep learning and machine learning approaches in reservoir characterization and management, enabling the evaluation of subsurface reservoir properties even with incomplete datasets, which could lead to an improved understanding of the reservoir properties and better management of the reservoir. This integrated study provides deeper insight into the complex reservoir properties and can help improve decision-making processes and optimize management and production strategies in the challenging pre-salt carbonate reservoirs or similar complex reservoirs.

Effects of K2CO3 addition on the physicochemical properties of goethite composite pellets with different basicities (CaO/SiO2)

In this study, the effects of K2CO3 addition (0, 1, 2 wt%) on the physicochemical properties (moisture content, liquid saturation, plastic deformation degree, drop number, compressive strength) of green and (crystalline phase, fraction of melt phase, morphology, compressive strength and reduction behavior) of sintered composite pellets with varying basicities (CaO/SiO2 = 0.04, 0.40, 0.83, 1.24) were examined. The moisture content of cured green pellet with higher K2CO3 addition was greater at the same basicity. The corresponding results had a positive effect on the development of capillary state, which enhance the drop number and compressive strength up to approximately 14, 28.40 N/Pellet respectively above moisture content of 12.41 wt%. However, it was also confirmed that excessive moisture content (above 13.22 wt%) induced over liquid saturation and has negative effects on physical properties. The magnetite phase predominantly observed with increasing K2CO3 addition at fixed basicity of 0.40–1.24. Intraparticle porosity (pore size = 6.4 nm to 5 μm) decreased with higher K2CO3 addition and showed below 5% at 0.40–1.24 basicity. Interparticle porosity (pore size = 5–1100 μm) showed various behavior with K2CO3 addition at a basicity 0.04–0.40 but increased up to approximately 30% at a basicity 0.83–1.24. Compressive strength of sintered pellet tends to have negative effect on porosity. However, reduction behaviors have positive effects on higher fluxed sintered pellet due to advantageous reduction condition by impurities (alkali and alkaline earth metal cations). Obtained results help elucidate the physicochemical properties of composite pellet-containing alkali metal oxides with varying basicities.

Coupled Hydromechanical Modelling of a Vertical Hydraulic Sealing System Based on the Sandwich Principle

For the shaft sealing of a repository for radioactive waste, a Sandwich sealing system was developed by KIT-CMM consisting of bentonite-based sealing segments (DS) and sand mixture-based equipotential segments (ES). To demonstrate the functionality of the Sandwich sealing system, various laboratory tests (MiniSandwich tests and semi-technical scale experiments) have been carried out before a large-scale experiment has been implemented in situ at the Mont Terri Rock Laboratory (CH). An important coupled process in the Sandwich system is the swelling deformation of the DS while aqueous fluid penetrates into the system. Consequently, the interparticle porosity (effective porosity) of the DS decreases by swelling strain, resulting in a reduction in the permeability of the DS. Pore space of the ES also decreases slightly due to swelling stress in the adjacent DS, which also leads to a reduction in the permeability of the ES. To understand the coupled hydromechanical processes of the Sandwich sealing system, a numerical model was developed to interpret the experimental observations from the MiniSandwich tests and to parameterize different components. A linear swelling model for DS and empirical functions for the swelling deformation-induced permeability change for both DS and ES segments were introduced into the coupled model with Richards’ flow and elastic model. Sensitivity analysis with parameter variations of the most important parameters reduces the uncertainty in the system behavior.

Formation evaluation and rock type classification of Asmari Formation based on petrophysical- petrographic data: A case study in one of super fields in Iran southwest

The Oligo-Miocene Asmari Formation is one of the most important hydrocarbon reservoirs in the Middle East. The oilfield under study is one of the largest oilfields in the Zagros basin with the Asmari Formation being the major reservoir rock. In this study, petrographic analyses, petrophysical data and neural network clustering techniques were used for identifying rock types in the Asmari reservoir. Facies analysis of the Asmari Formation in the study area has resulted in the definition of 1 clastic lithofacies and 14 carbonate microfacies types. Using petrophysical logs from 43 wells and their correlation with capillary pressure ( P c ) curves, led to the recognition of 7 electrofacies (EF1-EF7). Microscopic evidence of Electrofacies group C1 and S1 show that the sedimentary facies of these electrofacies are most commonly found in restricted and shoal facies belts zone. Also, petrographic studies show that the sedimentary facies of C2, C3, C4, S2 and S3 were formed in the open marine, Lagoon, and Tidal flat facies belt zone of homoclinal ramp sedimentary environment during the Oligo-Miocene based on relative sea level changes respectively. The link between electrofacies and geological data indicated that both sedimentary and diagenetic processes controlled the reservoir quality of the Asmari Formation. Porosity, permeability and water saturation were used to estimate the reservoir quality of each electrofacies. EFs 1 and 2 with high porosity and permeability, low water saturation is considered as the best reservoir with regard to sedimentary textures (dolowackestone and dolograinstone) and the effect of diagenetic processes such as dolomitization processes. Vuggy, growth framework and interparticle porosities are major in EF-2, while the intercrystalline porosity is the major type in EF-1. EFs 3 and 4 show low values of porosity, permeability and high percentage of water saturations, which characterizes them as poor reservoir rocks. Finally, EF-5 is the only electrofacies in the siliciclastic parts of the Asmari reservoir, which is composed of rounded and well-sorted quartz grains that are slightly cemented. In sandstone electrofacies, electrofacies EF- 5 (S1), is the best type of sandstone reservoir rock and to move towards electrofacies EF-7 (S3), will reduce reservoir quality. In carbonate electrofacies, also, electrofacies no 1, the best type of carbonate reservoir rock can be observed and move towards electrofacie number 4, lower quality of reservoir rocks is seen. • This research can be useful in the development of the field and determining oil production in the future of similar fields.