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The swelling and softening of mudstones caused by water often lead to serious geological disasters. In petroleum exploration and development, the hydration expansion of mudstone can also lead to serious wellbore instability hazards. The swelling of smectite clays is the main reason for this hydration expansion in mudstones. It is generally recogniz...
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In this study, the engineering properties such as physical, optical and textural properties of the raw and processed black gram, moth bean, green gram, brown lentil, and red gram were evaluated. The evaluation of the engineering properties can help to design the appropriate processing equipments. Among different species, the significant variation i...
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... Clay minerals typically have negatively charged surfaces that repel one another, and this repulsion causes swelling when the clay exposes to water. It is worth noting that the addition of salts to a solution containing clay minerals can prevent the clay from swelling, thus the swelling effect in the experiments would be negligible [67][68][69][70] . The positively charged ions in the salt can disrupt the electrostatic forces and neutralize some of the negative charges on the clay particles that cause the clay to swell in the presence of water. ...
The study of the properties of engineered rocks is of great importance to researchers in engineering sciences such as petroleum, mining, and civil engineering owing to their wide application in these fields. In the present study, a physico-chemical and geomechanical investigation was carried out on the effects of different clay minerals on porous rocks. Various chemical products formed during chemical interactions between cement, clay minerals, and water can change the pore structure and thus the rock characteristics. The results of the current study showed that increasing the clay content could remarkably reduce the porosity and permeability of the rock by an average of 86% and 6.76%, respectively. In this regard, samples containing kaolinite were further influenced due to their new pore structure. Moreover, a power relationship was found between sonic velocity and porosity, which can be used to predict rock properties. Chemical analysis indicated an amplification in quantities of chemical products, particularly calcium silicate hydrate and portlandite, due to an increase in clay content. The impacts of porosity and cementation quality as two main factors on rock strength have also been studied. The outcomes revealed that a reduction in porosity could compensate for detrimental effects of poor bond quality and consequently improved UCS by up to 30% in samples containing kaolinite, while decreasing the degree of cementation prevailed over the porosity reduction in specimens including illite and resulted in a 14% decrease in UCS. The effects of porosity and bond quality on UCS would cancel each other out in samples containing bentonite. It is worth noting that when it comes to changes in geomechanical characteristics, the dominant factor (i.e., porosity reduction or cementation quality) determines the ultimate effect of clay minerals on the properties of engineered porous rocks.
... The structural characteristics and strength characteristics of the same kind of mudstone vary significantly with different moisture contents [10]. In addition, acidic liquid can relatively promote the disintegration of mudstone, while an alkaline environment can relatively inhibit its disintegration [11,12]. Laying polymer cement on the surface of mudstone can relatively inhibit the disintegration characteristics of mudstone when it meets water and temperature differences [13]. ...
Mudstone, whose significant characteristic is water-weakening, widely exists in all kinds of geotechnical engineering, which brings great security risks to engineering safety. In this paper, through a series of macro and meso test methods, the macro and meso action mechanism of water on the weakly consolidated plane of mudstone was studied. In the uniaxial compressive strength test, the mudstone cementation plane was the main part of the fracture derived. Under the moist state, the strength of mudstone would decrease significantly, which was inversely correlated with relative moisture content. In the case of flooding, mudstone cracking occurred only along the cementation plane. Through ESEM+mapping test, results showed the humidification curing caused obvious damage to the cemented plane, where sodium and calcium were lost without a certain cause. The cemented plane was rich in kinds of clay minerals in mesoscale and presented an inhomogeneous state. The surface hardness data obtained from nanoindentation were discrete and difficult to quantitatively evaluate the mesomechanical properties. However, compared with the dry state, the data set of the moist state had a significant decline, showing a weakening effect. The mudstone is prone to fail along these weakly consolidated planes. Moisture intrudes into the bedding plane further deteriorating their consolidation.
... 2 (9 g KCl) 10 2 (6 g KCl) in KCL mass in drilling fluid decreases the swelling capacity of clay (Chen et al. 2020). During this study, it was observed from Fig. 3 that as the mass of KCL in the drilling fluid increases the volume of filtrate loss decreases. ...
Drilling fluids are the most imperative element during drilling activity. Apart from their significance during drilling operations, they are also responsible for causing formation damage within reservoir through invasion. The invaded volume of drilling fluid in both flushed and transition zones not only damage the permeability of the reservoir, but can also significantly change the characteristics of the reservoir fluid through contamination. The contaminated crude oil will eventually lead to erroneous valuation of the reservoir fluid properties, which will directly impact the overall estimation of the operational cost. Understanding and examining the influence of drilling fluid contamination on reservoir fluid properties is the primarily objective of this study. During the preliminary stage, five samples of water-based drilling fluid having different concentrations of salt (i.e., KCL) ranging from 6 to 18 g were prepared. The samples were analyzed in terms of filtration and rheological properties. As the concentration of KCL increases till 12 g, an improvement in rheological properties and filtration volume was observed. Further increase in salt concentration degrades the drilling fluid. This degradation occurs because of poor performance of filtrate control material and segregation of KCL as concentration increases. Moreover, these five samples were than mixed in varying ratios of 8:2 and 6:4 (crude oil/drilling fluid) in crude oil, which was obtained from Northern region of Pakistan. Initially, the uncontaminated crude oil has the characteristics of heavy oil with high viscosity and lower API gravity. Measurement conducted on contaminated crude oil samples indicates the alteration of fluid properties with increase in viscosity and density. These variations in properties will eventually affects the flowing capabilities of the oil through the production system and will increase the overall cost of the project.
... Because of rock saturation, the strength was decreased. Similarly, Chen et al. 31 that means the dicationic surfactant does not change the internal structure of the rock. 3.5. ...
The interactions of clays with freshwater in unconventional tight sandstones can affect the mechanical properties of the rock. The hydraulic fracturing technique is the most successful technique to produce hydrocarbons from unconventional tight sandstone formations. Knowledge of clay minerals and their chemical interactions with fracturing fluids is extremely vital in the optimal design of fracturing fluids. In this study, quaternary ammonium-based dicationic surfactants are proposed as clay swelling inhibitors in fracturing fluids to reduce the fractured face skin. For this purpose, several coreflooding and breakdown pressure experiments were conducted on the Scioto sandstone samples, and the rock mechanical properties of the flooded samples after drying were assessed. Coreflooding experiments proceeded in a way that the samples were flooded with the investigated fluid and then postflooded with deionized water (DW). Rock mechanical parameters, such as compressive strength, tensile strength, and linear elastic properties, were evaluated using unconfined compressive strength test, scratch test, indirect Brazilian disc test, and breakdown pressure test. The performance of novel synthesized surfactants was compared with commercially used clay stabilizing additives such as sodium chloride (NaCl) and potassium chloride (KCl). For comparison, base case experiments were performed with untreated samples and samples treated with DW. Scioto sandstone samples with high illite contents were used in this study. Results showed that the samples treated with conventional electrolyte solutions lost permeability up to 65% when postflooded with DW. In contrast, fracturing fluid containing surfactant solutions retained the original permeability even after being postflooded with DW. Conventional clay stabilizing additives led to the swelling of clays caused by high compression and tensile strength of the rock when tested at dry conditions. Consequently, the rock fractures at a higher breakdown pressure. However, novel dicationic surfactants do not cause any swelling, and therefore, the rock fractures at the original breakdown pressure.
... The ceramic properties of clays depend on their chemical and mineralogical compositions and their texture (Norton, 1974;Ngun et al., 2011). For example, the smectite clays generally show high sensitivity upon drying and firing than kaolinitic and illitic clays because of the finer size and higher swelling capacity of smectite than both kaolinite and illite (Grim, 1962;Chen et al., 2020). The clays suitable for brickmaking require relatively low sensitivity to drying and low total linear shrinkage upon drying and firing. ...
Dry saturation of clays from the Maastrichtian-Danian Dakhla Formation, comprising high smectite clays, using 3 % potassium bromide (KBr) at 300oc resulted in a partial transformation of the original Ca-smectite to mixed-layer illite-smectite like structure. The clays’ wet saturation mentioned above with 0.5, 1.0, 2.0, and 9.0 % potassium chloride (KCl) at room temperature causes a full transformation of smectite layers to a mixed clay-like structure. The rate of transformation is directly proportional to K⁺ ion concentration. The K⁺ ions are fixed in smectite by filling vacancies left by Ca⁺⁺ ions. The change of temperature from room temperature to 80oC slightly reduces the original smectite’s transformation rate, while the increase of maturation time shows no effect. The transformation of smectite to mixed clay layer like structure is accompanied by a decrease in the linear shrinkage and drying sensitivity coefficient of the original clays. The Dakhla clays’ wet saturation with 1.0% KCl at room temperature is the most suitable treatment to enhance the studied clays’ ceramic properties as raw material for brickmaking. The linear shrinkage and drying sensitivity coefficient of the treated clay samples under these conditions results in new properties similar to those exhibited by Nile River-silts, which are the traditional raw material for brickmaking in Egypt.
A rainfall-induced catastrophic landslide occurred at 03:50 local time UTC + 8 on August 21, 2020 in Zhonghaicun (29°20′30″ N, 102°41′40″ E), Hanyuan County, China. Approximately 1.1 million cubic meters of debris failed instantly along the interface between the overlying soil and the Xigeda mudstone, destroying six buildings and causing nine casualties. The Xigeda stratum near the landslide consists of poorly lithified mudstone, which is characterized by weak cementation and unfavorable dip angle. The Xigeda stratum, as a locally distributed special formation in southwest China, is well known for the feature of “being prone to failure”. In this paper, the mineral composition tests and mechanical strength tests were conducted to determine the physical and mechanical properties of the soil and rock-like stratum. In addition, numerical calculations were carried out to analyze the evolution of the Zhonghaicun landslide. The test results show that the Xigeda mudstone is a weakly swelling rock containing a large amount of clay minerals. The water content of the mudstone plays a significant role in its physico-mechanical properties. The heavy rainfall lasting approximately one week caused the water table to rise and the mudstone to soften, which eventually triggered the Zhonghaicun landslide.
