Analysis Of Mineralogical Composition Research Articles

The occurrences and mobility of shale oil in the pore space of terrestrial shale

Movable oil, the critical factor for shale oil enrichment and effective production, is influenced by the pore structure and shale oil occurrence state. However, the pore spaces storing movable oil, the occurrence state of shale oil, and the lower flowing pore size for shale oil remained unclear. To address this knowledge gap, we chose the lacustrine organic-rich Chang7 shale of the Ordos Basin as the research target. By combining gas adsorption techniques (nitrogen and carbon dioxide) with Soxhlet Extraction, we investigated the pore structure alteration of Chang7 shale after Soxhlet Extraction. Based on a comprehensive analysis of mineralogical composition, TOC, and shale oil components, we discussed the pore space in which shale oil exists. Then, we established a slit-shaped clay model and clarified the occurrence state of multi-component shale oil in the pore space with the help of molecular simulation. Our investigation revealed that (1) Chang7 shale can be categorized into three distinct types. Type I, characterized by a high clay mineral content, possesses the greatest SSA and PV and has the highest abundance of movable oil, partially filling the “ink-bottle”-type pores. Shale oil in Type II and III shales mainly exists within slit-type pores. (2) The pore space of Chang7 shale is primarily comprised of mesopores rather than micropores. Moreover, mesopores’ PV and SSA are predominantly governed by clay minerals rather than organic matter. (3) A threshold pore size of 10 nm significantly impacts the occurrence state of shale oil in the Chang7 shale. Beyond this threshold, free oil accounts for over 80% of the total. Chang7 shale oil within micropores (<2 nm) is predominantly asphaltene, existing in an adsorbed state. Within pores sized 2 to 10 nm, shale oil is present in both adsorbed and free states, and the proportion of free-state shale oil increases with the pore size. Free-state shale oil prevails in pores exceeding 10 nm, with a smaller fraction adsorbed onto organic matter and mineral surfaces. Thus, we recommend adopting 10 nm as the lower flowing pore size limit for Chang7 shale.

Research on characteristics and geological genesis of large-scale deep-seated landslide in tuff formation

In engineering practice, engineers generally treated tuff as a lumpy material with a poorly defined laminated structure and a rock group that was not susceptible to slide failure. Most studies of tuff landslides had focused on small clastic landslides in shallow strata with weathering boundaries and lithologic interfaces as slip surfaces. This paper takes a large-scale, deep-seated tuff landslide on the southeast coast of China as the research project. We used borehole TV imaging and exploration tunnels to confirm the material composition and structural characteristics of the tuff stratum and used exploration tunnels to expose the slip soil directly. Microscopic identification, mineralogical composition analysis, zircon U-Pb isotope dating, and Hf isotope analysis of slip soils collected from the exploration tunnels elucidated the geologic background and genesis of the large-scale deep-seated landslides in the tuff stratum. It was found that the formation of a tuff stratum in the landslide area was caused by multi-volcanic orogeny and multi-phase tectonics. The timing of the melting of the original magma from these volcanic events also differs. During these intervals between eruptions, deposition occurred, and this sedimentary material formed the slip soil.

Sedimentary evidence of paleovegetation and human activity at Pope manor in the 17th – 19th centuries

Sediments are an important archive, containing evidence of natural events and human activity in a given place. For this reason, a 49-cm-long sediment monolith of a section from the slope of an elevation at Pope, where the hunting castle is situated, was taken during archaeological excavations with the aim of finding out the environmental conditions during formation of the cultural layer. Samples were studied using a multidisciplinary approach, including sediment composition, granulometric and mineralogical composition analysis, as well as paleobotanical analysis of plant macroscopic remains and pollen analyses. The results obtained in all analyses complement each other and give the impression that naturally accumulated sediments were mixed by human activity. This is evidenced by their similar composition throughout the section. The results of analyses of macroscopic plant remains and pollen contained in the sediments indicate the environmental conditions at the time during the existence of the hunting castle at Pope. According to the data of paleobotanical analyses, and the considerable amount of grasses, especially weeds, the landscape was relatively open and cultivated.

CO2–Brine–rock interaction and sequestration capacity in carbonate reservoirs of the Tahe Oilfield, Xinjiang, China

AbstractThe characteristics of each carbonate reservoir are greatly different, and current databases are insufficient to support engineering scheme design and optimization of carbon dioxide (CO2) sequestration and enhanced oil recovery. In this paper, the behavior of CO2‐brine‐rock interactions was investigated under supercritical CO2 (50°C and 8.5 MPa) conditions. Five experiments were carried out, including CO2 solubility in brine, mass loss analysis by static reaction of CO2–brine–rock, mineralogical composition analysis by X‐ray diffraction (XRD), core surface morphology analysis by scanning electron microscopy (SEM), and wettability alteration by contact angle analysis. The experimental results showed that: (a) the CO2 solubility in brine increases with increasing pressure, but it increases slowly and gradually reaches equilibrium; (b) the mass loss of carbonate increases with reaction time, but its increments decrease with reaction time; (c) the calcite content gradually decreases and the quartz content slightly increases with reaction time, as evidenced by XRD analysis; (d) based on SEM image analysis, calcite was dissolved into brine by carbonic acid to make the pores larger, and then subsequent precipitation made the pores smaller; and (e) the carbonate rock surface became more water‐wet after CO2–brine–rock interaction experiments due to surface corrosion and increased quartz content. Using the experimental results, a mathematical model was developed to predict CO2 sequestration capacity under reservoir conditions. The results suggest that CO2 solubility in brine was the main aspect compared with mineral trapping in carbonate reservoirs, and CO2 sequestration capacity increased with increasing temperature and pressure. © 2022 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

Influence of the mold growth on the crystallographic composition of hemp mortar

The use of hemp mortar as a bio-based insulation composite is widely promoted in the construction sector in France due to its environmental and hygrothermal advantages and the availability and low price of hemp fibers. Nevertheless, the use of such materials claims the consideration of the microbiological contamination that could lead to its degradation. Molds are known for their ability to modify locally the composition of hemp mortar by decreasing the pH level. That’s why the main objectives of the present work are, first, to expose the hemp mortar favorable conditions for mold growth, secondly, to investigate the proliferation of the mold filaments inside the hemp mortar sample and, then, to analyze the crystallographic composition. Experimentally, hemp mortar samples were exposed to high level of relative humidity during one year until the mold growth. The SEM observation allowed to follow the internal growth and identify the depth of the mold growth. Finally, the composition of the contaminated hemp mortar was studied by X-ray diffraction. The obtained results reveal that molds growth occurs not only on the surface but also in the depth. Nevertheless, as the mold growth started only after one year of high humidity exposure, a good resistance of studied hemp mortar towards molds was noted. Furthermore, the mineralogical composition analysis of the contaminated samples shows that the hydrates responsible for durability remained. These results provide data to better predict the durability of hemp mortars.

Performance evaluation of regenerated clinker from completely recyclable mortar

This study aims to characterize the performance of recycled clinker prepared from more sustainable concrete that can preserve natural resources. A completely recyclable mortar (CRM) was designed with a composition similar to that of the raw cement materials. Then, recycled cement generated from CRM was used to prepare another CRM and further recycled. The XRD patterns, free calcium oxide content, and mechanical strength of the recycled clinker after each cycle were studied. The results showed that as the number of cycles increased, the strength and hydration activity of the recycled cement clinker gradually decreased. Mineralogical composition analysis showed the weakening of the C3S diffraction peak and decrease in C3S content as well as strengthening of the C2S diffraction peak and increase in C2S content with an increase in cycle number. The degradation of the recycled clinker performance may be attributed to the presence of unhydrated cement particles in the heat-cured mortar. Although the hydration activity of the recycled cement clinker decreased, its carbonization strength increased significantly, which could be attributed to its high C2S content.

Krystalizacja simonkolleitu (Zn5Cl2(OH)8 · H2O) w preparatach proszkowych do analizy ilościowej składu mineralnego (QXRD)

The analysis of mineralogical composition by quantitative X-ray diffraction (QXRD) is one of the standard research methods used in hydrocarbon exploration. In order to improve it and to obtain better results, the methodology of quantitative analysis used at Well Logging Department is being periodically (more or less) modified. After the introduction of the improvements, comparative analyses were performed on archival samples. Reflections from an unidentified phase which did not occur in the tested Rotliegend sandstone samples were noticed on X-ray diffractograms of archival samples. Reflections of a mineral called simonkolleite were identified in the X-ray diffraction database. Chemically it is a hydrated zinc chloride of the formula: Zn5Cl2(OH)8 × H2O. Analysis of the composition of samples in which simonkolleite crystallised, indicated that the mineral is being formed in the result of the slow reaction of zinc oxide with halite (NaCl) and water vapour. An attempt was made to determine the influence of the presence of this mineral on the results of the quantitative analysis of mineralogical composition. The above methodology was applied on a group of ten samples. The results of the quantitative analysis conducted for archival samples stored with added zincite standard containing simonkolleite and for new, freshly grinded (without artifact) samples were compared. The comparison of the obtained results showed a slight influence of this mineral on the quantitative composition of the remaining components. The difference between the results usually did not exceed the method error. At the same time a significant difference in the calculated content of the internal standard was noted – on average 1% less in archival than in new samples. This shows that the reaction occurring in the archival samples will affect the evaluation of the quality of the obtained quantitative analysis, at the same time excluding the possibility of determining the rock’s amorphous substance content with the internal standard method.

Evidence of the middle Miocene paratethys transgression from Jurkowice-Budy site (SE Holy Cross Mountains, Poland

&nbsp;Identifying ancient shores may provide valuable information concerning sea-level fluctuations and environmental changes, since they serve as a reliable marker of palaeoshorelines. This paper deals with deposits that display features of a nearshore zone. In the Jurkowice-Budy quarry (southern slopes of the Holy Cross Mountains) a sequence of clastic sediments and littoral structures linked to the transgression of the Paratethys Sea in the middle Miocene has been recognised. The discovery of bio-erosional assemblages (borings of lithophags) in Devonian limestone boulders helped to determine the littoral nature of the examined deposits and to layout a palaeocliff wall. The samples of sandy sediments were analysed by sieving procedure and interpreted using statistical parameters calculated by graphic and moment methods. Moreover, morphometric analysis of gravels and analysis of mineralogical composition under binocular microscope were performed. The results showed well-developed beach assemblages composed of pebbles, coarse-to-medium sands and silty sands derived from eroded Cambrian strata (sand-stones) located to the north of the study site.

Adsorption of bentazone in the profiles of mineral soils with low organic matter content.

The current laboratory adsorption study aimed at determination of the values of adsorption distribution coefficient (Kd) of bentazone in the profiles of Arenosols, Luvisols, and Cambisols, which are the most common arable mineral soils in Poland. The study attempted to identify the soil components that bind bentazone and the principal adsorption mechanisms of this compound as well as create a model capable of predicting its adsorption in soils. The Kd values determined in batch experiments after 24 h of shaking were very low, and ranged from 0.05 to 0.30 mL/g for the Ap horizon and 0 to 0.07 mL/g for subsoils. The results indicated that the anionic form of bentazone was adsorbed on organic matter, while in acidic soils the neutral form of bentazone was adsorbed on organic matter and sand. The detailed analyses of mineralogical composition revealed that the principal mineral that was responsible for the adsorption of bentazone was quartz, which content was strongly positively correlated with the sand fraction. In soils with pH < 5 and an organic carbon content of < 0.35%, quartz exhibited much greater affinity for the neutral bentazone form than organic matter. Fourier transform infrared photoacoustic spectroscopy analyses supported by computational methods have shown the most probable mechanisms behind the adsorption of bentazone on quartz. The created model, assuming the adsorption of bentazone on organic matter and on sand and using the spectrophotometrically determined dissociation constant of bentazone, very well explained the Kd variance in the 81 examined soils, while correctly predicting the adsorption based on soil properties described in the published data.

Strength Development in Bio Mineralised Steelslag Bricks using Micp Process

Steel slag annual production in India is about 12 million tonnes per annum. Steel slag is one of the industrial residue came out from steel industries. The amount of steel slag produced from different steel industries is 150-200kg per tonnes of steel produced These steel slag is dumped in land and pollute the environment. Paper mills produce the large amount of lime sludge is about 5 lakh tonnes per annum. These steel slag used as binder material and coarse aggregate also in different sieve sizes. These both steel slag and lime material contains large amount of calcium mineral compared than other waste materials. The conventional burnt clay brick manufacturing firing process develops the 750 million tonnes of co2 emissions per year. The Bio mineralised steel slag bricks developed by using these waste materials and bacillus bacteria. These microbes generates the calcium carbonate precipitation in the steel slag bricks. The strength development of these BMSS bricks were achieved by addition of NBU medium supply and carbonation process. The scanning electron microscope (SEM), mineralogical composition analysis, X-ray diffraction analysis, compressive strength and water absorption test are conducted to support the strength development in bio mineralised steel slag bricks.

Characterization of Coals and Coal Ashes with High Si Content Using Combined Second-Derivative Infrared Spectroscopy and Raman Spectroscopy

The organic and mineral components in two coals and resulting high-temperature ashes with high silicon content were characterized by second-derivative infrared spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD). The infrared spectra of raw coals show weak organic functional groups bands but strong kaolinite bands because of the relatively high silicates content. In contrast, the Raman spectra of raw coals show strong disordered carbon bands but no mineral bands since Raman spectroscopy is highly sensitive to carbonaceous phases. The overlapping bands of mineral components (e.g., calcite, feldspar, and muscovite) were successfully resolved by the method of second-derivative infrared spectroscopy. The results of infrared spectra indicate the presence of metakaolinite in coal ashes, suggesting the thermal transformation of kaolinite during ashing. Intense quartz bands were shown in both infrared and Raman spectra of coal ashes. In addition, Raman spectra of coal ashes show a very strong characteristic band of anatase (149 cm–1), although the titanium oxides content is very low. Combined use of second-derivative infrared spectroscopy and Raman spectroscopy provides valuable insight into the analyses of mineralogical composition. The XRD results generally agree with those of FTIR and Raman spectroscopic analyses.

Elemental and Mineralogical Composition of the Western Andean Snow (18\xb0S\u201341\xb0S)

The snowpack is an important source of water for many Andean communities. Because of its importance, elemental and mineralogical composition analysis of the Andean snow is a worthwhile effort. In this study, we conducted a chemical composition analysis (major and trace elements, mineralogy, and chemical enrichment) of surface snow sampled at 21 sites across a transect of about 2,500 km in the Chilean Andes (18–41°S). Our results enabled us to identify five depositional environments: (i) sites 1–3 (in the Atacama Desert, 18–26°S) with relatively high concentrations of metals, high abundance of quartz and low presence of arsenates, (ii) sites 4–8 (in northern Chile, 29–32°S) with relatively high abundance of quartz and low presence of metals and arsenates, (iii) sites 9–12 (in central Chile, 33–35°S) with anthropogenic enrichment of metals, relatively high values of quartz and low abundance of arsenates, (iv) sites 13–14 (also in central Chile, 35–37°S) with relatively high values of quartz and low presence of metals and arsenates, and v) sites 15–21 (in southern Chile, 37–41°S) with relatively high abundance of arsenates and low presence of metals and quartz. We found significant anthropogenic enrichment at sites close to Santiago (a major city of 6 million inhabitants) and in the Atacama Desert (that hosts several major copper mines).

ИССЛЕДОВАНИЕ МИНЕРАЛОГИЧЕСКОГО СОСТАВА ОСАДКООБРАЗОВАНИЙ В УСЛОВИЯХ СКВАЖИННОЙ ДОБЫЧИ УРАНА

ИССЛЕДОВАНИЕ МИНЕРАЛОГИЧЕСКОГО СОСТАВА ОСАДКООБРАЗОВАНИЙ В УСЛОВИЯХ СКВАЖИННОЙ ДОБЫЧИ УРАНА

Applications of Calcium Hydrosilicates and Amorphous Aluminosilicates in Lime Dry Mixes

Information is given on the possibility of using additives based on calcium hydrosilicates synthesized using diatomite and amorphous aluminosilicates as modifying dry mortar in the formulation. The data of the analysis of mineralogical composition of the investigated additives are given, the influence of additives on the change in the plastic strength of the lime test and the content of free lime is revealed. The kinetics of the change in the strength of lime samples was studied, which confirmed that the investigational additives possess a structuring effect and can be used as modifying agents.

Mineralogical Features of Chalcopyrite and Sphalerite in Copper–Pyrite Ore Tailings in the Light of Prospects for the Purposeful Formation of Man-Made Deposits

The purposeful formation of man-made deposits is connected with the creation of such conditions under which a waste material acquires preset process properties while stored. This will enable future environmental clean processing of waste. Aiming to determine general mechanisms of formation of process properties in copper-pyrite ore tailings, the comprehensive analysis of mineralogical composition of tailings from three concentration plants processing ore from six large copper-pyrite deposits in the South Ural was performed. The crystal-chemical formulas of the basic ore minerals are studied and systematized. The morphological varieties of ore minerals are identified. It is found that even in case of deposits of the same genetic type, processing regimes and parameters of current mill tailings depend on the initial mineralogical features of waste based on which man-made deposits are formed. These features have influence on the mechanisms and stages of the secondary minerogenesis in the man-made deposits.

A difficulty to process a low quality titano-ferrite concentrates

The essential technological criteria interfering with the implementation of titano-ferrite concentrate accumulated in the amount of 4.5 thousand tones at the Obukhov deposit were determined by means of certified methods of chemical, fractional, granulometric and mineralogical composition analysis. A poor quality and unacceptable processing of the concentrate by applying the standard method of restoring electric smelting used to produce titanium slag is established to be stipulated by a high chromium trioxide (more than 8 wt.%) content, iron trioxide (over 29 wt.%); silicon dioxide (3.9 wt.%) and inconsistency with the regulated requirements for the mass fraction of titanium dioxide (about 52%). The great number of rutile insoluble in acids to 17 wt.% within the sand fraction and about 27 wt.% within the titano-ferrite fraction eliminates opportunity to involve leucoxenized high chromium concentrate into the processing by means of sulfuric dissolution method used to obtain pigmental titanium dioxide. Besides, an obstacle to process the concentrate is connected with the extreme dissemination and close assemblage of rutile and pseudomorphic varieties of leucoxenized titano-ferrite (arizonite, pseudo-brookite) with metal and nonmetal minerals that predetermine joint concentration of the bulk of titanium, iron, chromium, other accompanying elements and just a little smaller half of the total amount of silicon (44.35 wt.%) in aggregate of mineral flakes with a size of –0.063+0.044 mm. The most preferable conditions of mineral flakes disintegration were selected to ensure an increase in the granulometric composition of the concentrate to 90-95 % of –0.063+0.044 mm class in the process of short-term, for 10-15 minutes, mechanical activation, caused by the rapid destruction of large aggregates of mineral individuals. An exploratory research has shown that, despite the fineness of grinding, the significant leukoxenization of titano-ferrite causes a low, only 47-50 %, degree of dissection of the activated concentrate by the sulfuric acid dissolution method.

Porosity characteristics of the Eocene mixed-sediment reservoirs in the saline lacustrine basin, Qaidam, China

In recent years, significant progress has been achieved in the field of deep exploration in the Yingxi area of the Qaidam Basin. The Eocene was characterized by mixed sediments in the lacustrine basin. The area consists of lacustrine carbonate, detrital material, and mud. All rocks contain numerous salt minerals. Via core observation, physical property analysis, capillary pressure tests, image logging, and field emission scanning electron microscopy, results reveal that the rocks contain a double porosity system. The first are fractures and salt mineral dissolution pores possessing a large pore radius, and the second are cracks between the salts and dolomite intercrystalline pores with a small pore radius. These two types of pores caused the double-platform feature with a lower narrow portion and upper wide portion on capillary pressure curves. Overall, the physical properties of the rocks are deficient, with low porosity-ultra-low permeability. Moreover, pores and throats are generally acceptable. Mineralogical composition analysis based on electronic probe shows that the rocks possess a high content of both silicon and aluminum, but low content of iron and manganese. The average FeO content in the dolomicrite is 1.322%, and that of MnO is 0.060%, both of which are lower than average Fe or Mn content in hydrothermal dolomite. It is believed that the dolomicrite possesses a penecontemporaneous metasomatic formation mechanism. The dolomitization process produces a large number of shrunken intercrystalline pores. These kinds of matrix pores, functioning as storage space, constitute an important support factor for the sustained and stable production of oil and gas in the study area.

Characterization of Residues Involved in the Ash Quenching System: A Material Recycling Perspective

The Ash Quenching System has been widely used in the municipal solid waste incineration plant to cool down the bottom ash and to control the dust pollution. In this study, residues that were transferred to the ash quenching system, including the grate siftings and the unquenched bottom ash were investigated, as well as, the quenched bottom ash from the discharge point of the system. The characterization included particle size distribution analysis, chemical composition and mineralogical composition analyses. The results showed that the grate siftings, the unquenched bottom ash and the quenched bottom ash were made up of different proportions of slag, relic metal, glass, ceramics and unburnt organic matter. All residues resembled to natural sand and fine aggregates with content of CaO, SiO2, Al2O3 and Fe2O3 of about 37-52%, 17-28%, 10-16%, and 4-13% by mass, respectively. The quenched bottom ash had the potential to be used as a raw material for the engineering applications such as road construction and cement production likewise grate siftings and the unquenched ash. However, the grate siftings and the unquenched bottom ash contained Cl up to 2.3 % by mass, and the quenched bottom ash was essentially dominated by hydrate phases such as Friedel’s salt/hydrocalumite, thus further treatment is significantly required prior to any applications.

Quantifying local-scale dust emission from the Arabian Red Sea coastal plain

Abstract. Dust plumes emitted from the narrow Arabian Red Sea coastal plain are often observed on satellite images and felt in local population centers. Despite its relatively small area, the coastal plain could be a significant dust source; however, its effect is not well quantified as it is not well approximated in global or even regional models. In addition, because of close proximity to the Red Sea, a significant amount of dust from the coastal areas could be deposited into the Red Sea and serve as a vital component of the nutrient balance of marine ecosystems.In the current study, we apply the offline Community Land Model version 4 (CLM4) to better quantify dust emission from the coastal plain during the period of 2009–2011. We verify the spatial and temporal variability in model results using independent weather station reports. We also compare the results with the MERRA Aerosol Reanalysis (MERRAero). We show that the best results are obtained with 1 km model spatial resolution and dust source function based on Meteosat Second Generation Spinning Enhanced Visible and InfraRed Imager (SEVIRI) measurements. We present the dust emission spatial pattern, as well as estimates of seasonal and diurnal variability in dust event frequency and intensity, and discuss the emission regime in the major dust generation hot spot areas. We demonstrate the contrasting seasonal dust cycles in the northern and southern parts of the coastal plain and discuss the physical mechanisms responsible for dust generation.This study provides the first estimates of the fine-scale spatial and temporal distribution of dust emissions from the Arabian Red Sea coastal plain constrained by MERRAero and short-term WRF-Chem simulations. The estimate of total dust emission from the coastal plain, tuned to fit emissions in MERRAero, is 7.5 ± 0.5 Mt a−1. Small interannual variability indicates that the study area is a stable dust source. The mineralogical composition analysis shows that the coastal plain generates around 76 ± 5 kt of iron oxides and 6 ± 0.4 kt of phosphorus annually. Over 65 % of dust is emitted from the northern part of the coastal plain.

Water vapour sorption on mudrocks

Abstract High-resolution water sorption isotherms were measured on 13 representative mudrock samples in order to assess the mechanisms of water vapour sorption and their relationship to the pore structure of mudrocks. The isotherm measurements were performed at 303 K on a gravimetric, dynamic vapour sorption device. Experimental data were interpreted by traditional physisorption models for which the validity was evaluated by relating model parameters to those obtained from nitrogen physisorption measurements. No direct relationships with the pore structure were observed, except for the Gurvich total pore volumes and the corresponding porosity data. Specific surface areas from Brunauer–Emmett–Teller theory are ambiguous and do not relate to nitrogen data, suggesting that water molecules do not adsorb as (multi-) layers covering pore walls. The volume filling theory (Dubinin–Astakhov equation) fits the water sorption data well but no relationship to the nitrogen data was observed in the studied sample set. A lower affinity of water for micropores was evident from the higher filling pressures of N 2 -based micropore volumes. The Barret–Joyner–Hallenda theory combined with N 2 physisorption measurements on moist mudrocks revealed that capillary condensation prevails close to saturation but not below about 0.94 relative pressure ( p / p 0 ). A distinct low-pressure hysteresis was observed from hysteresis scanning that was attributed to surface chemistry since capillary condensation occurs only at very high relative pressures. Analysis of mineralogical composition, total organic content (TOC) and organic maturity in relation to water sorption revealed only a weak correlation with the total clay content. In contrast, cation-exchange capacity (CEC) strongly correlates with water uptake, which evidences a surface-chemistry-controlled sorption mechanism. Tests of the influence of the exchangeable cation were inconclusive because pore system alteration due to cation-exchange probably superimposed the effect. To further assess the sorption mechanisms of water, nitrogen physisorption isotherms were measured on moisture-equilibrated mudrocks (11, 52, 75, 94% relative humidity at 298 K). Micropore analysis and cumulative pore-size distributions denote that water blocks pore throats rather than fills pore volumes at lower relative humidities. Over the entire humidity range, no direct relationship between water sorption and pore size was observed. These findings imply that water adsorption does not sequentially fill pores with increasing radii in mudrocks as relative humidity increases, as would be expected from water sorption by capillary condensation. This conclusion has important implications for the interpretation and measurement of geomechanical and petrophysical properties of mudrocks. Capillary pressures, particularly at low water saturations, are often calculated from water saturation using a concept based on the Kelvin equation for capillary condensation. Since water sorption in mudrocks seems to be controlled by surface chemistry rather than pore size, this approach is questionable. The observations reported here suggest that the water distribution in mudrock pore systems resulting from vapour equilibration differs from that obtained by fluid displacement (i.e. capillary drainage or imbibitions). A further consequence is that water vapour equilibration is a convenient, but not necessarily representative, method to obtain partially water-saturated mudrock samples for laboratory measurement of saturation-dependent geomechanical or petrophysical properties.