Clay Interlayer Research Articles

Updated stratigraphic correlations due to lithological composition at the M-II-4 horizon, Aksai field

The results of laboratory-based core analysis and log interpretation are presented in the paper to justify separation of various lithological reservoir types of the productive horizon M-II-4 within limits of the Aksai field. The geological section under study is composed of sandstones, gravelstones, conglomerates with carbonate-clayey cement with clay and sandstone interlayers. According to the results of the work, taking into account all geological and geophysical data, aleuritic-sandy, gravelite-conglomerate with carbonate cement and gravelite-conglomerate with carbonate-clay cement with layers of clays and sandstones types of reservoirs are identified. The results obtained were taken into account when reservoir characterization, recommendations were given for further areas of research work.

Molecular simulation of polyether amines intercalation into Na-montmorillonite interlayer as clay-swelling inhibitors

Polyether amines (PEA) have been widely used in water-based drilling fluids (WBDFs) to prevent the clay swelling and maintain the wellbore stability during the drilling process due to its excellent inhibition performance and low toxicity towards the environment. Understanding the intercalation behavior of PEA within clay interlayer is of great significance to disclose the inhibition mechanism and design high-performance drilling fluid additives. In this work, molecular dynamic (MD) simulations are applied to investigate the arrangement and dynamic properties of neutral PEA (N-PEA) and protonated PEA (P-PEA) within Na-montmorillonite (MMT) interlayer in the presence of one, two and three layer water content. We found that the N-PEA molecules tend to interact with clay surface with the –NH2 groups and a stronger interaction between –NH3+ groups and clay surface is observed when 33% Na+ is replaced by P-PEA molecules. While for the scenario with 66% Na+ is substituted by P-PEA molecules, the –NH3+ groups prefer to distribute in the middle of the pore hydrating with water molecules. The N-PEA molecules are likely to form a crown-like structure wrapping Na+ inside which is detrimental for the water invasion into clay layer. Based on the analysis of Na+ distribution in MMT layer, it is observed that the introduction of P-PEA molecules replace the Na+ in the middle of the pore first and followed by the surface Na+. Both of the N-PEA and P-PEA molecules are capable of forming hydrogen bonding (H-bonding) with MMT surface reducing the propensity of MMT to attract water. Furthermore, the minimum H-bonding number between MMT and P-PEA molecules is observed when 66% Na+ is exchanged due to strong water-PEA interaction. In addition, the inhibition mechanisms of neutral PEA molecules by forming PEA-Na+ complexes to cut off the connection between Na+ and water molecules is similar for different water contents. Our study provides important insights into the structural properties of PEA molecules within MMT interlayer and clay inhibition mechanism of PEA.

APPLICATION OF A MULTIDIMENSIONAL DETERMINISTIC-STATISTICAL NUMERICAL CORRELATION MODEL TO REFINE THE STRUCTURE OF THE AS11 HORIZON OF THE ZAPADNO-KAMYNSKOYE FIELD

One of the primary and significant tasks in the construction of geological models of oil and gas reservoirs and development facilities is the problem of correlation of productive layers. This task, as a rule, is reduced to the identification and areal tracing of presumably even-aged oil and gas strata, horizons, and layers characterized by clear boundaries between sand strata and clay layers overlapping them. The practice of work related to modeling the structure of oil and gas horizons, layers and strata indicates that the correlation is not always unambiguous. The ambiguity is especially noticeable when correlating strata characterized by a clinoform structure, one of the examples is the Achimov strata. The most reliable basis for well correlation is GIS materials and lithological features of the interlayers forming individual layers. Clay interlayers and clay strata separating productive deposits provide valuable information when choosing a correlation model in sedimentary sections. These interlayers are characterized by the greatest consistency in area and are most clearly displayed on geophysical diagrams by the nature of the drawings of GIS curves. However, even in this case, i. e. when using the entire accumulated volume of the most diverse lithological and field-geophysical information, the correlation models of the sections turn out to be different and often even opposite. In this paper, the authors had to face a similar situation when correlating the horizon AS11 of the Zapadno-Kamynskoye field. The paper describes a method for clarifying the position of the chops of the productive horizon of oil and gas deposits using a multidimensional deterministic-statistical numerical model of the correlation of sedimentary strata. The proposed approach allows us to uniquely determine the positions of the chops in the conditions of a complex geological structure of the object, high thin-layered heterogeneity. A concrete example shows the advantages of the proposed approach in comparison with the traditional one.

A sensitive voltammetric analysis and detection of Alizarin Red S onto a glassy carbon electrode modified by an organosmectite

A low-cost, simple and ultra-sensitive voltammetric sensor for the determination of Alizarin Red S (ARS) in aqueous solution using a glassy carbon electrode modified by drop coating of organosmectite film is reported. Various proportions of dimethyldioctadecylammonium (DODA+) cations have been intercalated by cation exchange in the interlayer of the natural clay. Physico-chemical characterization techniques were used to confirm the effectiveness of the intercalation. Electrochemical characterization techniques have been used to determine the surface charge, the permeability, the charge transfer resistance and the real surface of elaborated electrodes. Differential pulse voltammetry (DPV) was used for the reduction of anthraquinone function of ARS, and under optimized conditions, the calibration curve was plotted in the concentration range from 0.01 ​μM to 0.1 ​μM, revealing a detection limit of 3.8 ​nM. The interfering effect of some ions and compounds was evaluated to highlight the selectivity of elaborated sensor. The designed sensor was applied successfully in real samples.

Estimating the influence of the technological interlayer lamination on stability of the goaf supporting elements

Within the Verkhnekamskoye salt deposit, productive sylvinite layers are mined using chambers supporting the overlying strata with pillars of various sizes, which stability is determined by mechanical properties of rocks, mining depths, a mining plan of layers, sizes of chambers, etc. The bearing capacity of the interchamber pillars is largely influenced by conditions of the roof and soil of the chambers and, especially, by the technological interlayer. The presence of thin clay interlayers reduces the rocks stability of the roof of underground structures and causes its intense lamination and caving of the interlayer rocks, thus, increases the height of the interchamber pillars and decreases their bearing capacity. The paper presents estimates of changing loads of the pillars during the lamination of the roof of the stoping of the lower productive layer, which is obtained by the multivariate mathematical modeling of the stress-strain state of the two-layer chamber block taking into account the main features of the geological structure and geometry of the mines. The calculations were carried out for the conditions of the plane strain state. The stress state of the chamber block was described by an ideal elastoplastic medium. The thin-layered medium was described using Goodman joint elements.

ХАРАКТЕРИСТИКА ГИДРОГЕОЛОГИЧЕСКИХ МАССИВОВ БОЛЬШОГО, МАЛОГО КАВКАЗА И ТАЛЫША (АЗЕРБАЙДЖАН) С УЧЕТОМ ГЛОБАЛЬНЫХ ИЗМЕНЕНИЙ КЛИМАТА

Issues of global warming lead to dramatic changes in hydrological and hydrogeological conditions. The Caspian Sea and mountain ranges have a great influence on the formation of the climate. Many believed that climate models and predictions are probabilistic in nature, but some will think that global climate change is important today. It is necessary to take into account that climate change is global, it occurs everywhere on our planet and affects every state and every person. Purpose: Clarification of the influence of the relief and the proximity of the Caspian Sea which determines the differences and distribution of air temperature, precipitation and other climate elements. The annual amount of precipitation falls in the cold half of the year in the form of snow, the melting of which causes violent spring floods on the rivers, evaporation and sufficient relative moisture. The characteristics of climatic zones show their close relationship with the nature of the relief and with the hypsometric position of the terrain above sea level. Ground waters within the Greater, Lesser Caucasus and Talysh are distributed everywhere. In the Greater Caucasus, there are mainly distributed gravels of the Kusar Formation (QIV), and within the Khvalynskaya, Khazar, Bakinskaya and Kusarskaya formations, clay interlayers divide the general flow of groundwater into several horizons of pressure water, the same pattern also takes place in the Lesser Caucasus and Talysh. Climate change, the nature of precipitation distribution, the growing season of plants, pH-pH, an increase in the average global temperature causing various side effects, the frequency of extreme weather events, a rise or decrease in the water level, ultimately all this affects all elements of the hydrological river systems and calculated industrial reserves of groundwater. Deforestation contributes to global warming and one of the main reasons for the intensification of the greenhouse effect, negatively affects the water cycle, the transpiration process stops. We should participate in the process of reducing CO2 emissions, pay attention to the increase of forest areas, reduction of water pollution, transfer to unconventional renewable solar and wind power, accelerate the introduction of alternative energy deposits of thermal waters.

Effect of occurrence states of fluid and pore structures on shale oil movability

The occurrence states of oil in the kerogen and structural characteristics of shale are unfavorable for the production of shale oil. Understanding the movability of oil and water at different occurrence states or in different pore structures is important for the development of shale oil reservoirs. Therefore, a high-speed centrifugation experiment based on the nuclear magnetic resonance technique was conducted for shale samples saturated with oil and water to test the movability of oil and water in the shale. To describe the effect of nanopores and the direction of capillaries on the movability of oil and water in the shale, a mathematical model based on the variational diameter capillary model was developed. The results indicated that a larger amount of bound oil (the adsorption-dissolution oil in the kerogen and the oil in the nanopores) was present in the shale, which is 3.12–5.44 times the amount of bound water (the adsorption oil on the interlayer of clay and the oil in the nanopores). The movability of free water (up to 88.8%) in the shale was larger than that of free oil (up to 68.1%) and the movability of free fluid (up to 88.8%) in the shale was significantly larger than that of bound fluid (up to 12.4%). According to the model, most of the capillary diameters of the shale gradually increased in the direction of the centrifugal force and weakened as the lamination developed. The movability of bound oil and water in the nanopores was larger than the theoretical value.

Dynamics of Soil Water Content Across Different Landscapes in a Typical Desert-Oasis Ecotone

An understanding of soil water content dynamics is important for vegetation restoration in an arid desert-oasis ecotone under different landscapes. In this study, the dynamics of soil water content under three typical landscapes (i.e., desert, sand-binding shrubland, and farmland shelter woodland) were investigated in the Hexi Corridor, northwest China, during the growing season from 2002 to 2013. The results showed that the soil water content in the deep layers decreased from 20–30% to a stable low level of 3–5% in the desert and shrubland. For the farmland shelter woodland, the soil water content at the deep layers also decreased, but the decrease rate was much smaller than the desert and shrubland. The decrease of soil water content in the deep soil layers among desert–shrubland–woodland was strongly associated with the increase of groundwater depths. The greatest increase of groundwater depths mainly occurred during 2008–2011, while the largest decrease of soil water content took place during the years 2009–2011, with a time-lag in response to increase in groundwater depths. This study provides new insight into the long-term dynamics of soil water content in a typical desert oasis ecotone under different landscape components from the influence of overexploiting groundwater that cannot be inferred from a short-term study. The findings demonstrate that the sharp increase of groundwater depths could be the main reason behind the reduction of soil water content in the clay interlayers, and sustainable development of groundwater resources exploitation is very important for the management of desert-oasis ecotone from a long-term perspective.

Fast Advective Water Flow Through Nanochannels in Clay Interlayers: Implications for Moisture Transport in Soils and Unconventional Oil/Gas Production

Water flow in nanometer or sub-nanometer hydrophilic channels bears special importance in diverse fields of science and engineering. However, the nature of such water flow remains elusive. Here, we...

Experimental and numerical investigation of supercritical CO2 migration in sandstone with multiple clay interlayers

CO2 enhanced water recovery (CO2-EWR) is one of the most promising technologies for geologic carbon sequestration. The migration characteristics and displacement efficiency of supercritical CO2 (SC-CO2) after injection into a saline aquifer directly affect the feasibility and economy of a CO2-EWR project. Multiple clay interlayers often develop in the target sandstone reservoir and combine in different expansive ways, which could influence the SC-CO2 migration. In this study, core flooding experiments were conducted using a special sandstone with multiple thin clay interlayers and the fluid behavior was monitored by an X-ray computed tomography (X-CT) scanner. Based on the porosity matrix obtained from X-CT images, a two-dimension model based on Darcy flow was developed to simulate the fluid behavior under the experiment conditions. The experimental results show that SC-CO2 pathways were developed in the sand part of the sample, while the clay interlayers were fluid-proof. Comparing the experimental and simulation results, it is evident that the porosity distribution, clay interlayers directionality/extent and flooding direction were the main factors that affected the fluid behavior in the sample. There were positive correlations between porosity and SC-CO2 saturation after drainage processes. Flooding directions and clay interlayers were combined to affect the fluid migration. The clay interlayers had functions of barrier and collection when the flooding direction pointed towards the opening of a wedge-shaped semi-open area formed by clay interlayers. While this area was almost free of SC-CO2 when the injection direction reversed, resulting a smaller SC-CO2 saturation in sample during the backward drainage process.

Enhanced adsorption of per- and polyfluoroalkyl substances (PFAS) by edible, nutrient-amended montmorillonite clays

Humans and animals are frequently exposed to PFAS (per- and polyfluoroalkyl substances) through drinking water and food; however, no therapeutic sorbent strategies have been developed to mitigate this problem. Montmorillonites amended with the common nutrients, carnitine and choline, were characterized for their ability to bind 4 representative PFAS (PFOA, PFOS, GenX, and PFBS). Adsorption/desorption isothermal analysis showed that PFOA, PFOS (and a mixture of the two) fit the Langmuir model with high binding capacity, affinity and enthalpy at conditions simulating the stomach. A low percentage of desorption occurred at conditions simulating the intestine. The results suggested that hydrophobic and electrostatic interactions, and hydrogen bonding were responsible for sequestering PFAS into clay interlayers. Molecular dynamics (MD) simulations suggested the key mode of interaction of PFAS was through fluorinated carbon chains, and confirmed that PFOA and PFOS had enhanced binding to amended clays compared to GenX and PFBS. The safety and efficacy of amended montmorillonite clays were confirmed in Hydra vulgaris, where a mixture of amended sorbents delivered the highest protection against a PFAS mixture. These important results suggest that the inclusion of edible, nutrient-amended clays with optimal affinity, capacity, and enthalpy can be used to decrease the bioavailability of PFAS from contaminated drinking water and diets.

Imidazolium-Based Ionic Liquids as Clay Swelling Inhibitors: Mechanism, Performance Evaluation, and Effect of Different Anions.

Clay swelling is one of the challenges faced by the oil industry. Water-based drilling fluids (WBDF) are commonly used in drilling operations. The selection of WBDF depends on its performance to improve rheology, hydration properties, and fluid loss control. However, WBDF may result in clay swelling in shale formations during drilling. In this work, the impact of imidazolium-based ionic liquids on the clay swelling was investigated. The studied ionic liquids have a common cation group, 1-allyl-3-methyllimidozium, but differ in anions (bromide, iodide, chloride, and dicyanamide). The inhibition behavior of ionic liquids was assessed by linear swell test, inhibition test, capillary suction test, rheology, filtration, contact angle measurement, scanning electron microscopy, and X-ray diffraction (XRD). It was observed that the ionic liquids with different anions reduced the clay swelling. Ionic liquids having a dicyanamide anion showed slightly better swelling inhibition performance compared to other inhibitors. Scanning electron microscopy images showed the water tendency to damage the clay structure, displaying asymmetrical cavities and sharp edges. Nevertheless, the addition of an ionic liquid to sodium bentonite (clay) exhibited fewer cavities and a smooth and dense surface. XRD results showed the increase in d-spacing, demonstrating the intercalation of ionic liquids in interlayers of clay. The results showed that the clay swelling does not strongly depend on the type of anion in imidazolium-based ILs. However, the type of anion in imidazolium-based ILs influences the rheological properties. The performance of ionic liquids was compared with that of the commonly used clay inhibitor (sodium silicate) in the oil and gas industry. ILs showed improved performance compared to sodium silicate. The studied ionic liquids can be an attractive alternative for commercial clay inhibitors as their impact on the other properties of the drilling fluids was less compared to commercial inhibitors.

Amine- and alcohol-functionalized ionic liquids: Inhibition difference and application in water-based drilling fluids for wellbore stability

Shale hydration is the main cause of wellbore instability during drilling using water-based drilling fluids (WBD). In this work, NH2- and HO-functionalized ionic liquids (ILs) were investigated for their performances on inhibiting the shale hydration, as well as their influences on the properties of WBD, using immersion and sedimentation tests, linear swelling test, hot-rolling dispersion test, rheological and filtration experiments. The mechanisms were identified by X-ray diffraction (XRD), zeta-potential and particle size distribution analyses, scanning electron microscopy (SEM) and related theoretical analysis. Evaluation experiment results showed that the NH2-functionalized IL had the best inhibition performance, followed by poly(propylene glycol)bis(2-aminopropyl ether), HO-functionalized IL and KCl. NH2-functionality was more favorable to shale inhibition than HO-functionality. When used in WBD, ILs could prevent viscosity building-up at high temperature, but cause filtration and inhibition failure, which could be mitigated when polyanionic cellulose (PAC) was added in WBD prior to inhibitors. Three critical observations helped elucidate the inhibitive mechanisms: the intercalation of cationic groups of ILs into the clay interlayers, the decrease of both interlayer spacing and double layer thickness. The NH2-functionalized IL allowed the smallest interlayer spacing and double layer thickness and therefore performed best in inhibition. The inhibition failure in WBD with ILs depended on two aspects: the consumption of ILs untimely and the filtration failure of WBD. PAC could decrease both of ILs’ loss within WBD and water loss toward shale, mitigating the WBD’s inhibition failure. Our work will facilitate the rational design of efficient and environmentally acceptable inhibitors and their rational applications in WBD for drilling shale formation.

Technical and technological solutions for trouble-free production casing run in hole while completion in the Jurassic sediments of West Siberia oilfields

The article considers causes of complications and accidents occurring while drilling in the Jurassic deposits in the intervals of Bazhenov, Georgievski and Abalakski formations at the fields of West Siberia. It proposes technical and technological solutions for their trouble-free drilling and production casing RIH. The measures developed provide for preventing instability of wellbore in the interlayers of clay and mudstone, removal of drill cuttings in the wells with zenith angles exceeding 50 degrees and in extended reach wells, avoiding tight hole and stuck pipe problems, ensuring RIH to the bottom hole and good quality of cementing jobs.

Compression of Na-Montmorillonite Swelling Clay Interlayer Is Influenced by Fluid Polarity: A Steered Molecular Dynamics Study.

The compressive responses of an interlayer of the dry sodium-montmorillonite (Na-MMT) swelling clay as well as the clay intercalated with organic fluids of a wide range of dielectric constants from 110 (formamide) to 20 (acetone) are quantitatively evaluated using steered molecular dynamics simulations. Representative dry clay and clay with fluid (clay-fluid) molecular models are constructed, and the stress-strain relationships upon compression of these models are studied using constant force steered molecular dynamics (SMD) simulations. Our results show that the polarity of the fluids and the amount of the fluid molecules in the clay interlayer play a significant role in the interlayer spacing, interlayer volume, interlayer strain, interlayer modulus, nonbonded interactions, and conformation of the fluid molecules upon externally applied stresses. The clay interlayer responses upon compression are essential for the development of multiscale modeling of swelling clays and prediction of the reliable compressive behavior, which are critical for the accurate analysis and economical design of the infrastructures in swelling clay areas and the densification of clays for ceramics manufacturing.

Synthesis, characterisation and electrochemical application of hybrid nanocomposites of polyaniline with novel clay mineral

Clay mineral obtained from Tuticorin in Tamilnadu, India (Indian Clay- IC) was purified and used to synthesise polyaniline-Indian clay nanocomposites (Pani-IC NCP) by polymerising aniline with the clay by chemical oxidation method using potassium perdisulphate as oxidant and by varying the aniline to clay ratio. The formation of composite in nanoscale was confirmed by XRD and TEM analysis. The in situ intercalative polymerization of monomer within the clays was ascertained by FTIR, UV–visible, XRD, SEM and TEM studies. The analyses of UV visible and FTIR spectroscopy demonstrated that aniline has been polymerized to Pani in its conducting emeraldine form. The conformation adopted by Pani Chains in the clay interlayer depended on the molar ratio of aniline to clay. SEM analysis showed the variation in morphology from granular agglomerate to layered flaky structure as the clay concentration was increased. Thermal stability of the nanocomposites was studied using TGA/DTA and DSC studies and it was found that they showed better thermal stability than their pristine polymers indicating the enhanced barrier property of the nanoclay. XRD showed that the clay host used accommodates higher amount of emeraldine salt than MMT. The Cyclic voltammetry studies of the synthesized nanocomposites showed the one with 0.5 g clay showed better electrochemical response. It exhibited good adherent behaviour on electrode surface at pH 1.0 with two oxidation peaks at 463 and 672 mV and two reduction peaks at 360 and 126 mV. By varying the atmosphere it was found that the nanocomposite modified electrode exhibited oxygen reducing capacity than their Bentonite counterpart. Chronoamperometric and Chronocoulometric studies were also carried out at inert as well as oxidising atmosphere which confirmed the above fact. EIS studies of the modified electrodes showed double layer capacitance value of 5.95 × 10−8 Fcm−2 with the bode phase angle of 70°.

Approbation of the technology for displacing residual gas with nitrogen for the conditions of a depleted gas reservoir in the VS-9 horizon of the Lyubeshivske gas field

Most natural gas reservoirs of Ukraine are depleted to some extent; still they contain significant tail gas reserves. A promising direction for increasing gas recovery from depleted gas reservoirs is the displacement of tail gas from the porous medium with nitrogen which is easily accessible and does not cause corrosion of the down-hole equipment. This article characterizes the technologies for increasing gas recovery from depleted gas reser-voirs by injecting nitrogen into them. The technology of replacing tail gas with nitrogen is tested on the example of the depleted reservoir of ND-9 horizon of Lyubeshivskyy gas field, the productive deposits of which are composed mainly of sandstones with interlayers of limestone and clay. The authors consider fifteen options of injecting ni-trogen into the reservoir, including options of treating the bottom-hole of low-production wells at the beginning of the process of further reservoir development and at the beginning of the injection of nitrogen into the reservoir. In all cases, the reservoir is first redeveloped in the depletion mode until the reservoir pressure decreases to 0,1 from the initial value. After that, nitrogen is injected into one of the producing wells which is transferred to the injection well. The injection of nitrogen into the reservoir continues until the nitrogen content in the last produc-ing well is less than 5 % vol. All options are characterized by high values of the gas recovery coefficient and close values of the dura-tion of the reservoir further development. The positions of the front of the displacement of natural gas by nitrogen at various time points are given. According to the research results, the gas recovery coefficient for tail gas for var-ious options varies from 14,12 to 34,58 %. With the introduction of the technology of injecting nitrogen into the reservoir, the overall gas recovery coefficient increases from 72,25 % (at present development system) to 80,28 % when the residual gas is displaced by nitrogen.

Specific elevated adsorption and stability of cations in the interlayer compared with at the external surface of clay minerals

Clay minerals in soils contain ubiquitously abundant interlayer spaces; however, the vital role the interlayer plays in determining the adsorption and stability of aqueous species is still enigmatic. The aim of this work is to systematically address the specific elevated adsorption characteristics and underlying mechanism in the clay interlayer by carefully comparing with those at the external surface. A series of cations (Na+, K+, Cs+, Ca2+, Pb2+, Cd2+, Ba2+, and Zn2+) are considered and the molecular dynamics methods are conducted. The interlayer of clay minerals is highly compacted, and the electric double layer (EDL) structures of neighboring surfaces extensively overlap. This results in specific elevated adsorption and stability of cations confined in the interlayer, as compared to the external surface. The adsorption modes remained the same whereas the interfacial distributions clearly changed, and the adsorption numbers increased. The local structure alteration was obviously more pronounced for divalent (M2+) rather than monovalent (M+) cations, and M2+ ions were coordinated stably to approximately six surface oxygens on each side of the interlayer surface. Extremely condensed time-evolution trajectories of the interlayer cations predicted an enhanced stability, which was further evidenced by the generally increased averaged residence time with surface oxygens and substantially reduced diffusion coefficients. These results address the vital role of the clay interlayer in determining the adsorption and retention of metal ions in a soil solution, which may further help to manage radioactive and heavy metal ion pollution.

Synthesis of Palladium Chloride Impregnated on Al<sub>2</sub>O<sub>3</sub>- Pillared Clay for Reduction of Nitrobenzene

Palladium chloride impregnated on Al2O3-pillared clay (Pd/Al-PILC) was synthesized by intercalation of aluminium (III) chloride into clay interlayers and calcined at 500°C for 1 h. Subsequently, impregnated with PdCl2 and calcination at 450°C for 4 h. The modified clay catalyst was characterized by X-ray diffraction (XRD) for investigated atomic spacing of catalysts and N2 adsorption and desorption method (BET) for investigated surface area and pore volume of catalysts. The catalytic activities of Pd/Al-PILC was utilized for the reduction of nitrobenzene for synthesis aniline. The effect of various reaction factors, such as reaction time, reaction temperature, solvent system and the amount of catalyst were studied in order to optimize the reaction conditions. Aniline was prepared conveniently and efficiently via the reduction of nitrobenzene in the presence of a catalytic amount 40%Pd/Al-PILC of substrate in reflux temperature at 70°C for 4 h under extremely mild conditions.

Experimental investigation into methane production from hydrate-bearing clayey sediment by CO2/N2 replacement

The replacement of gas hydrate in clayey sediment by a CO2/N2 (20:80) gas mixture injection was experimentally studied to explore the influence of clay on the gas exchange behaviours in the gas hydrate. Clay (montmorillonite) and silica sand were mixed in three different proportions (clay mass ratios of 10%, 30% and 50%) to simulate the host sediments of natural gas hydrate while pure silica sand sediment was selected for comparison. Experimental results showed that clay hindered gas diffusion during the initial replacement stage and thus reduced the methane recovery rate. In the later stage, the gas exchange between CO2/N2 and methane in the hydrate structure might be subject to thermodynamic inhibition and geometric constraints of the clay interlayer. Moreover, the CO2 sequestration ratio was lowered significantly in the sediment with a 50% clay mass ratio. Therefore, it was determined that clay has an inhibitory effect on gas hydrate replacement by CO2/N2.