Search Results (210)

Petrological knowledge on weathering processes controlling the mobility of chemical elements is still limited in the dry tropical zone of Cameroon. This study aims to investigate the mobility of major and trace elements during rhyolite weathering and soil formation in Mobono by understanding the mineralogical and elemental vertical variation. The studied soil was classified as Cambisols containing mainly quartz, K-feldspar, plagioclase, smectite, kaolinite, illite, calcite, lepidocrocite, goethite, sepiolite, and interstratified clay minerals. pH values ranging between 6.11 and 8.77 indicated that hydrolysis, superimposed on oxidation and carbonation, is the main process responsible for the formation of secondary minerals, leading to the formation of iron oxides and calcite. The bedrock was mainly constituted of SiO₂, Al₂O₃, Na₂O, Fe₂O₃, Ba, Zr, Sr, Y, Ga, and Rb. Ce and Eu anomalies, and chondrite-normalized La/Yb ratios were 0.98, 0.67, and 2.86, respectively. SiO₂, Al₂O₃, Fe₂O₃, Na₂O, and K₂O were major elements in soil horizons. Trace elements revealed high levels of Ba (385 to 1320 mg kg⁻¹), Zr (158 to 429 mg kg⁻¹), Zn (61 to 151 mg kg⁻¹), Sr (62 to 243 mg kg⁻¹), Y (55 to 81 mg kg⁻¹), Rb (1102 to 58 mg kg⁻¹), and Ga (17.70 to 35 mg kg⁻¹). LREEs were more abundant than HREEs, with LREE/HREE ratio ranging between 2.60 and 6.24. Ce and Eu anomalies ranged from 1.08 to 1.21 and 0.58 to 1.24 respectively. The rhyolite-normalized La/Yb ratios varied between 0.56 and 0.96. Mass balance revealed the depletion of Si, Ca, Na, Mn, Sr, Ta, W, U, La, Ce, Pr, Nd, Sm, Gd and Lu, and the accumulation of Al, Fe, K, Mg, P, Sc, V, Co, Ni, Cu, Zn, Ga, Ge, Rb, Y, Zr, Nb, Cs, Ba, Hf, Pb, Th, Eu, Tb, Dy, Ho, Er, Tm and Yb during weathering along the soil profile. Full article

The aim of this study was to improve the efficiency of in situ uranium leaching by developing a specialized methodology for selecting rational parameters for the chemical treatment of production wells. This approach was designed to enhance the filtration properties of ores and extend the uninterrupted operation period of wells, considering the clay content of the productive horizon, the geological characteristics of the ore-bearing layer, and the composition of precipitation-forming materials. The mineralogical characteristics of ore and precipitate samples formed during the in situ leaching of uranium under various mining and geological conditions at a uranium deposit in the Syrdarya depression were identified using an X-ray diffraction analysis. It was established that ores of the Santonian stage are relatively homogeneous and consist mainly of quartz. During well operation, the precipitates formed are predominantly gypsum, which has little impact on the filtration properties of the ore. Ores of the Maastrichtian stage are less homogeneous and mainly composed of quartz and smectite, with minor amounts of potassium feldspar and kaolinite. The leaching of these ores results in the formation of gypsum with quartz impurities, which gradually reduces the filtration properties of the ore. Ores of the Campanian stage are heterogeneous, consisting mainly of quartz with varying proportions of clay minerals and gypsum. The leaching of these ores generates a variety of precipitates that significantly reduce the filtration properties of the productive horizon. Effective compositions and concentrations of decolmatant (clog removal) solutions were selected under laboratory conditions using a specially developed methodology and a TESCAN MIRA scanning electron microscope. Based on a scanning electron microscope analysis of the samples, the effectiveness of a decolmatizing solution based on hydrochloric and hydrofluoric acids (taking into account the concentration of the acids in the solution) was established for the destruction of precipitate formation during the in situ leaching of uranium. Geological blocks were ranked by their clay content to select rational parameters of decolmatant solutions for the efficient enhancement of ore filtration properties and the prevention of precipitation formation. Pilot-scale testing of the selected decolmatant parameters under various mining and geological conditions allowed the optimal chemical treatment parameters to be determined based on the clay content and the composition of precipitates in the productive horizon. An analysis of pilot well trials using the new approach showed an increase in the uninterrupted operational period of wells by 30%–40% under average mineral acid concentrations and by 25%–45% under maximum concentrations with surfactant additives in complex geological settings. As a result, an effective methodology for ranking geological blocks based on their ore clay content and precipitate composition was developed to determine the rational parameters of decolmatant solutions, enabling a maximized filtration performance and an extended well service life. This makes it possible to reduce the operating costs of extraction, control the geotechnological parameters of uranium well mining, and improve the efficiency of the in situ leaching of uranium under complex mining and geological conditions. Additionally, the approach increases the environmental and operational safety during uranium ore leaching intensification. Full article

Smectite clay minerals are known to readily form thixotropic physical gels in aqueous media, even at low volume fractions. Although the rheological properties of these gels are closely related to the microstructure of the network, the influence of the clay’s physicochemical characteristics remains insufficiently understood. In this study, we systematically investigated the relationships between particle size, cation exchange capacity, and zeta potential, and the rheological behavior of aqueous dispersions of four synthetic smectites. After thorough deionization, dispersions were prepared at controlled NaCl concentrations. We found that the zeta potential strongly correlates with the fineness of the network structure and governs macroscopic rheological responses such as viscosity, yield stress, and gelation behavior. Even under identical conditions, gel transparency and structural coarseness varied significantly among clay types. Furthermore, the storage modulus was influenced not only by network density but also by the intrinsic stiffness of the clay branches. These findings demonstrate that zeta potential serves as a unified indicator of structure and function in smectite dispersions and offer useful insights for gel design in colloidal and soft matter systems. Full article

Clays are fundamental raw materials in the ceramics industry due to their plasticity, mineralogical composition, and thermal behavior. This study characterizes four clay samples from Bustos (Portugal), aiming to assess their suitability for ceramic applications through granulometric, geochemical, mineralogical, and technological assays, looking at aspects such as their plasticity and sintering behavior. A textural analysis of the samples revealed distinct granulometric profiles, being dominated by silty–clayey fractions and low amounts of coarse particles, indicating high plasticity potential. Three samples showed an alkaline pH (8.17–8.63), and one an acidic pH (5.11), which can significantly influence the rheology and firing behavior of the ceramic body. Samples had a predominance of phyllosilicate minerals, followed by quartz and magnetite–maghemite, and trace amounts of feldspars, anatase, bassanite, and siderite. In the clay fraction, smectite, illite, and kaolinite were identified. By combining classical analysis techniques with ceramic technology principles, this study contributes to the sustainable development of local ceramic industries, emphasizing the importance of characterizing natural raw materials for industrial applications. The plasticity tests showed strong workability in two samples, which exhibited high values of plasticity and moldability, making them suitable for shaping processes in ceramic production. Also, sintering behavior tests revealed that the same clays exhibited good densification during firing, with relatively low shrinkage. Full article

The Carajás Mineral Province hosts one of the world’s most extensive sulfide-bearing copper belts. These deposits are typically covered by thick regolith, including gossans, laterites, colluviums, and soil, which can be used as important exploration indicators. In some cases, these covers can be mined alongside the parent hypogene ore. Therefore, accurate identification of copper-bearing minerals is essential for selecting the most appropriate metallurgical techniques. This study investigated the saprolite horizon overlying the Alvo 118 deposit, where the parent rocks are chloritites hosting copper-bearing hypogene sulfides, partially altered to an immature gossan. Saprolite formation was primarily controlled by the weathering of chlorite, mostly converted into kaolinite, with smectite and vermiculite serving as intermediates, forming a typical lower saprolite association. During weathering, iron released from chlorite and indirectly by vermiculite and smectite contributed to the formation of ferrihydrite, goethite, and hematite. Magnetite octahedrons, relics of the hypogene ore, pseudomorphic phases, are embedded in the clay mineral matrix. While FTIR analysis of kaolinite showed no evidence of copper retention, Mössbauer spectroscopy enabled the quantification of iron-bearing minerals, revealing a strong correlation between CuO contents and goethite and ferrihydrite. These results suggest that goethite and ferrihydrite may be the main copper carriers in the deposit, consistent with findings from similar deposits. Weak acid leaching is proposed as the most effective technique for copper extraction from this mineralization type. Full article

Authigenic minerals in shale are products of the co-evolution of organic and inorganic components, affecting the heterogeneity of shale reservoirs. However, due to their fine granularity and complex rock composition, studies on these minerals in shale are still insufficient. This research focuses on the lacustrine shales from the upper sub-member of the fourth member in the Eocene Shahejie Formation, Dongying Sag, East China. Utilizing core samples, thin sections, scanning electron microscope, X-ray diffraction, elemental geochemistry, and organic geochemistry, we systematically characterized the features and origins of authigenic minerals. The results identified several typical authigenic minerals, including authigenic quartz, framboidal and euhedral pyrite, ferroan dolomite, kaolinite, chlorite, and albite. Authigenic quartz is predominantly diagenetic silica formed through smectite illitization, acidic dissolution of K-feldspar, and alkaline dissolution of detrital quartz. Pyrite is a product of microbial sulfate reduction, with framboidal pyrite forming during an early diagenetic stage under conditions with sufficient solute supply and euhedral pyrite forming during a later stage under conditions with insufficient solute supply. Ferroan dolomite originates from the precipitation of Fe and Mg during smectite illitization, with slight contributions from the acidic dissolution of chlorite and calcite. Kaolinite stems from the acidic dissolution of K-feldspar, while chlorite results from the transformation of kaolinite. Albite primarily arises from the alkaline alteration of anorthite and K-feldspar. Most non-clay authigenic minerals likely enhance reservoir quality by slightly reducing the effects of compaction, whereas authigenic clay minerals typically exert detrimental effects on reservoir properties. This study constrains the genesis of authigenic minerals to assess their influence on reservoir quality in lacustrine shale. Full article

In recent years, the exploration of the Baibei Sag, located in the west of the Erlian Basin, has remained relatively underdeveloped. The Lower Cretaceous of the Baibei Sag hosts multiple tight sandstone reservoirs; however, research on the macro- and micro-characteristics, as well as the controlling factors of these reservoirs, is relatively limited. This study selected 105 Lower Cretaceous sandstone samples from the Baibei Sag for core observation, casting thin sections, scanning electron microscopy, X-ray diffraction, and high-pressure mercury intrusion analysis. The reservoir’s physical properties, pore throat structure, and diagenesis process were studied. The results indicate that the reservoir lithology is mainly composed of feldspar lithic sandstone, with an average composition of 44.3% lithic, 34.6% quartz, and 21.2% feldspar. The clay minerals in the interstitial material are primarily illite (69.3%) and illite–smectite mixed layers (12.7%), with smaller amounts of chlorite (10.9%) and kaolinite (7.2%), while smectite content is very low. The physical property analysis results indicate that the average effective porosity of the Tengger Formation sandstone is 3.3%. The average permeability is 0.01 × 10⁻³ μm². The average effective porosity of the Aershan Formation sandstone is 0.86%, and the average permeability is 0.05 × 10⁻³ μm². The Tengger Formation and Aershan Formation are both tight sandstone reservoirs. The analysis of pore throat structure shows that the reservoir space is mainly composed of dissolution pores. Three types of pore throat structures were identified, and corresponding pore models were established. Based on burial history and organic matter evolution characteristics, this study establishes a diagenetic evolution sequence of the Lower Cretaceous sandstone reservoir. Analysis suggests that the pore throat structure of different reservoir types is mainly controlled by material composition. In the process of diagenetic evolution, the Tengger Formation and Aershan Formation are in the Middle diagenetic stage A. Compaction and cementation are the main reasons for low porosity, while the dissolution improves reservoir performance. The intergranular and intragranular dissolution pores formed by dissolution are the main storage spaces of the reservoir. The early tectonic fractures are filled with calcite, and the residual small-scale fractures play a role in improving permeability. Full article

Novel geothermal power generation systems are being developed that use supercritical CO₂ as the heat transfer medium. In this technology, some CO₂ injected into the underground reacts with surrounding water and rocks to form secondary minerals, such as carbonate minerals and clay minerals; however, the reaction mechanism in the vicinity of the injection well, the subject of this study, has not been clarified. As the first laboratory test, Rishiri Island basalt was reacted with distilled water at 250 °C for 15 days at four different CO₂ concentrations to investigate the difference in reaction depending on the CO₂ concentration. Na, K and Ca increased rapidly until 5 days of the reaction, with higher values at higher CO₂ concentrations; Mg showed characteristic behavior with higher values in the test without CO₂ (using Ar gas). The saturation index of each secondary mineral was calculated, and it was found that carbonate minerals were unsaturated and clay minerals, such as smectite, were supersaturated under all test conditions, which was in agreement with the experimental results. It is concluded that a small amount of clay minerals was formed in this test due to the low pH of the reaction solution caused by the high CO₂ concentration, indicating that dissolution was the main reaction for the rocks in the vicinity of the injection well. Full article

With the rapid development of the coalbed methane (CBM) industry in China, coal seam No. 8 of the Benxi Formation in the Ordos Basin has emerged as a key target for CBM development due to its abundant deep reserves. However, wellbore instability during deep CBM extraction has become increasingly problematic, with the degradation of coal mechanical strength caused by drilling fluid invasion being identified as a critical factor affecting drilling safety and operational efficiency. This study focuses on coal seam No. 8 of the Benxi Formation in the Sulige Gas Field, Ordos Basin. Through experimental analyses of the coal’s mineral composition, microstructure, hydration expansion properties, and mechanical strength variations, the mechanism underlying drilling fluid invasion-induced mechanical strength degradation is elucidated. The experimental results reveal that coal seam No. 8 of the Benxi Formation exhibits a high carbon content and a low absolute clay mineral content (approximately 6.11%), with minimal expansive minerals (e.g., mixed-layer illite–smectite accounts for 26.4%). Consequently, the coal demonstrates a low linear expansion rate and weak hydration dispersion properties, indicating that hydration expansion is not the dominant mechanism driving mechanical strength degradation. However, drilling fluid invasion significantly reduced coal’s Young’s modulus (from 1988.1 MPa to 1676.1 MPa, a 15.69% decrease) and compressive strength (from 7.9 MPa to 6.5 MPa, a 17.72% drop), while markedly affecting its internal friction angle. Friction coefficient tests further demonstrate that the synergistic action of water molecules and additives decreases microcrack sliding resistance by 19.22% with simulated formation water and by 25.00% with drilling fluid, thereby promoting microcrack propagation and failure. This process ultimately leads to a degradation in mechanical strength. Hence, the enhancement of sliding effects induced by drilling fluid invasion is identified as the primary factor contributing to coal mechanical strength degradation, whereas hydration expansion plays a secondary role. To mitigate these effects, optimizing the design of drilling fluid systems and selecting suitable anti-collapse additives to reduce sliding effects are critical for minimizing wellbore instability risks in coal seams. These measures will ensure safer and more efficient drilling operations for deep CBM extraction. Full article

Clays deposited in marine evaporite sequences are strongly altered, and the most important factor determining their transformation is brine concentration. An X-ray diffraction study of clay minerals associated with the Lower and Middle Miocene evaporite formations of the Ukrainian Carpathian Foredeep indicated that the clay mineral assemblages in the gypsum facies are composed of smectite and illite, and, in some samples, mixed-layer chlorite–smectite and illite–smectite, as well as chlorite. In the halite facies, illite, chlorite, and mixed-layer illite–smectite occur in rock salt of Eggenburgian age (Vorotyshcha Suite); in addition to those minerals, smectite, corrensite, and mixed-layer chlorite–smectite occur in the Badenian rock salt (Tyras Suite); and in the potash facies, illite and chlorite were recorded. Such clay mineral assemblages resulted from the aggradational transformation of unstable and labile minerals and phases (kaolinite, smectite, and mixed-layer phases) that finally pass into illite and chlorite, minerals that are stable in an evaporite environment. In addition to brine concentration control, another important factor in the transformations of clay minerals was the sorption of organic components on the mineral structure, which slows the transformation processes. The assemblage of clay minerals in the weathering zone of the evaporite deposits, besides inherited illite and chlorite, also contains mixed-layer illite–smectite and kaolinite. The appearance of those clay minerals in hypergene deposits is the consequence of two processes: degradational transformation (illite–smectite) and neoformation (kaolinite) in conditions of decreased ionic concentrations during desalination. Full article

This study focuses on the Hailijing sandstone-hosted uranium deposit in the Songliao Basin. Through a combination of petrographic analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and geochemical analysis, the epigenetic alteration of the deposit was systematically investigated, and the alteration zonation was delineated. On this basis, the metallogenic mechanisms were further explored. The results indicate that six major types of alteration can be identified in the ore-bearing strata of the Hailijing uranium deposit: hematitization, limonitization, carbonatization, pyritization, clay mineralization (including kaolinite, illite, and illite-smectite mixed-layer), and baritization. The mineral assemblages at different stages of alteration vary: during the sedimentary diagenetic stage, the assemblage consists of “hematite + clay minerals + II-type pyrite (framboidal pyrite) + III-type pyrite (euhedral granular pyrite)”; during the uranium mineralization stage, it transitions to “ankerite + barite + I-type pyrite (colloidal pyrite) + minor kaolinite”; and in the post-ore stage, alteration is characterized by calcite cementation in red sandstones. Based on petrological, mineralogical, and geochemical characteristics, as well as the spatial distribution of the host gray sandstones, it is inferred that during uranium mineralization stage, the ore-bearing strata underwent reduction by uranium-rich reducing fluids sourced from the Lower Cretaceous Jiufotang Formation. The primary red sandstones of the Lower Yaojia Formation, formed under arid to semi-arid conditions, experienced varying degrees of reduction, resulting in a color transition from light red, brownish red, and yellowish brown to grayish-yellow and gray. Accordingly, four alteration zones are distinguished in the Hailijing uranium deposit: the primary red zone, weakly reduced pink zone, moderately reduced grayish-yellow zone, and strongly reduced gray zone. Furthermore, as the uranium-rich reducing fluids migrated from a high-temperature, high-pressure deep system to the low-temperature, low-pressure ore-bearing sandstone strata near the surface, uranium was unloaded, precipitated, and enriched, ultimately forming multi-layered and tabular-shaped uranium orebodies within the gray sandstone. This study elucidates the epigenetic alteration processes and metallogenic mechanisms of the Hailijing uranium deposit, providing a critical theoretical basis for further uranium exploration in the southern Songliao Basin. Full article

The sandstone sections in the Upper Jurassic red beds of the Yongjin area in the central Junggar Basin are important oil and gas reservoirs. The debate over whether red beds are of primary depositional or secondary diagenetic origin persists, leading to uncertainties in the interpretation of reservoir sedimentary facies. This study uses core samples and employs thin section microscope observations, scanning electron microscopy, X-ray diffraction, and major and trace element analyses to investigate the formation period and paleoclimate conditions of red beds and explore the origin of red sandstone. The Upper Jurassic red beds are mainly deposited in arid delta plain environments. The framework grains of the red sandstone are composed of quartz (averaging 22.6%), feldspar (averaging 16.3%), and rock fragments (averaging 36.7%). The rock fragments in the sandstone are mainly composed of intermediate basic volcanic rocks and cryptocrystalline acid volcanic rocks, which are rich in mafic silicate minerals such as olivine, pyroxene, ilmenite, and magnetite. In situ hematitization of ilmenite is observed in the rock fragments, suggesting that the in situ alteration of mafic silicate minerals in the parent rock is the main source of iron ions for hematite. Tiny hematite crystals (2.1 μm) are observed in clay mineral micropores via SEM. Abundant mixed-layer illite/smectite clay indicates early smectite transformation, providing a minor source of iron ions for hematite. Hematite in the red sandstone occurs as a grain-coating type, predating quartz overgrowth, feldspar overgrowth, and (ferroan) calcite and (ferroan) dolomite precipitation. Residual hematite coatings between detrital grain point contacts indicate that hematite is a product of syn-sedimentary or very early diagenetic precipitation, ruling out the possibility that red sandstone formation was caused by later atmospheric water leaching during the fold and thrust belt stage. The average chemical index of alteration (CIA) for the red sandstone is 52.2, whereas the CIA for the red mudstone averages 59.5, and the chemical index of weathering (CIW) reached a maximum of 69. These values indicate that the rocks have undergone mild chemical weathering in arid climates. Additionally, the ratios of trace elements indicate that the water bodies were in an oxidizing state during the sedimentary period. The arid climate and oxidative water conditions were ideal for hematite preservation, thus facilitating red bed formation. The red bed sediments in the study area represent a direct response to the Late Jurassic aridification event and can be compared to global climate change. The results have important implications for stratigraphic correlation and interpretation of reservoir sedimentary facies in the study area while also providing a valuable case study for global research on red beds. Full article

The diagenetic transformation of detrital clay minerals significantly influences sandstone reservoir quality, with fluid chemistry and temperature playing key roles in dictating transformation pathways during burial diagenesis. While these processes are well-documented in basinal settings, the diagenetic alterations of sediments in dynamic environments like estuaries remain underexplored. This study investigates the impact of fluid composition on the transformation of modern estuarine sediments through hydrothermal experiments using sediments from the Gironde estuary, SW France. A range of natural and synthetic solutions including seawater (SW), 0.1 M KCl (SF1), 0.1 M NaCl, KCl, CaCl₂·2H₂O, MgCl₂·6H₂O (SF2), estuarine water (EW), and 0.1 M Na₂CO₃ (SF3) were used under temperatures from 50 °C to 250 °C for 14 days, with a fixed fluid-to-sediment ratio of 10:1. The results revealed distinct mineralogical transformations driven by fluid composition. Dissolution of detrital feldspars and clay materials began at lower temperatures (<100 °C). The authigenic formation of smectite and its subsequent illitization in K-rich fluids (SW, SF1) occurred between 150 °C and 250 °C, replicating potassium-driven illitization processes observed in natural sandstones. Additionally, chlorite formation occurred through the conversion of smectite in SF2 and EW. Geochemical analysis showed that SF2 produced Mg-rich chlorites, while EW yielded Fe-rich chlorites. This aligns with diagenetic trends in coastal environments, where Fe-rich chlorites are typically associated with estuarine systems. The resulting authigenic illite and chlorite exhibited morphological and chemical characteristics similar to those found in natural sandstones, forming through dissolution-crystallization and solid-state transformation mechanisms. In contrast to illite and chlorite, SF3 produced entirely different mineral phases, including halite and analcime (zeolite), attributed to the high alkalinity and Na-rich composition of the solution. These findings provide valuable insights into the role of fluid chemistry in the diagenetic alteration of modern sediments and their implications for the evolution of sandstone reservoirs, which is critical for energy exploration and transition. Full article

Routine core permeability and porosity are crucial in assessing flow units within a reservoir because they define a reservoir’s storage and flow capacities. A limited amount of work has been conducted on the lower cretaceous (Barremian to Valanginian) sandstones in the Bredasdorp Basin, offshore South Africa, focusing on the flow zones and the possible effect of diagenetic minerals on the individual flow zones, limiting understanding of reservoir quality and fluid flow behavior across the field. Nine hundred routine core analysis datasets were used to determine the flow units within the reservoir from three wells (F-A10, F-A13, and F-O2) from independent methods, namely: the Pore Throat Radius, Flow Zone Indicator, Stratigraphic Modified Lorenz Plot, and Improved Stratigraphic Modified Lorenz Plot. The results showed six flow units: fracture, super-conductive, conductor, semi-conductor, baffle, and semi-barrier. The super-conductive flow units contributed the most flow, whereas the semi-barrier and baffle units contributed the least flow. Petrography analyses revealed that the diagenetic minerals present were smectite, illite, glauconite, siderite, micrite calcite, and chlorite. The pore-filling minerals reduced the pore spaces and affected pore connectivity, significantly affecting the flow contribution of the baffle and semi-barrier units. Micrite calcite and siderite cementation in FU5 of F-A13 and FU9 of F-O2 significantly reduced the intergranular porosity by filling up the pore spaces, resulting in tight flow units with impervious reservoir quality. It was noted that where the flow unit was classified as super-conductive, authigenic clays did not significantly affect porosity and permeability as they only occurred locally. However, calcite and silica cementation significantly affected pore connectivity, where the flow unit was classified as a very low, tight, semi-barrier, or barrier. Full article

Glycerin-based fluids are proposed as a promising alternative to inhibited fluids in the drilling of highly-reactive formations. However, even with the use of these fluids, it is still possible to observe the occurrence of problems related to the balling of drill bits and drill pipes, such as the agglomeration and accretion of cuttings. This study aims to analyze how the interaction between expandable minerals from reactive formations and glycerin-based drilling fluids affects the stability of oil wells, focusing on the occurrence and extent of the accretion phenomenon. For this purpose, bentonite pellets were characterized regarding their mineralogical composition and plastic behavior. In addition, accretion tests were performed in order to evaluate the interaction between bentonite pellets and glycerin-based drilling fluids containing different types of inhibitors. The results revealed that the pellets were predominantly composed of interstratified illite–smectite (IS) clay minerals and presented highly plastic properties with a high degree of expansion. Furthermore, it was found that the accretion percentages were significant for all the fluids studied, at higher than 58%. Therefore, it was found that using glycerin in drilling fluids did not stabilize expandable minerals in reactive formations, even with different expansion inhibitors, which were ineffective in reducing the rock expansibility. Full article