Clay Swelling Research Articles

Clay swelling mechanism in tuff stones: an example of the Hilbersdorf Tuff from Chemnitz, Germany

Hydric expansion is considered an important factor for the weathering behavior and deterioration of tuffs, which are utilized as building stones and typically associated with the presence of swellable clay minerals. Two types of swelling mechanisms are discussed when swellable clay minerals are present: stepwise intracrystalline swelling and continuous osmotic swelling. A mechanism that can cause expansion in the absence of swellable clay minerals, which is characterized by interaction of surface forces, is the disjoining pressure. The identification of the primary mode of swelling is important for understanding and finally preventing the swelling damage in tuff stones. The hydric expansion of the Hilbersdorf Tuff can exceed the values of typical volcanoclastic materials by multiples, but partly shows the absence of swellable clay minerals. In this study, extensive mineralogical and petrophysical investigations on five varieties of the Hilbersdorf Tuff were performed. Swelling experiments demonstrated that intracrystalline swelling plays a major role when swellable clay minerals are present. Furthermore, the importance of the structure and location of the clay minerals in the rock fabric is highlighted. The investigation suggests that the disjoining pressure plays an important role for the hydric expansion of two varieties, which are free of swellable clay minerals but show high microporosity and pores smaller than 2 nm.

Clay Swelling in Dry Supercritical Carbon Dioxide: Effects of Interlayer Cations on the Structure, Dynamics, and Energetics of CO2 Intercalation Probed by XRD, NMR, and GCMD Simulations

In situ X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) experiments combined with molecular dynamics simulations using the grand canonical ensemble [grand canonical molecular dynamics (GCMD)] show that the cation size, charge, and solvation energy play critical roles in determining the interlayer expansion of smectite clay minerals when exposed to dry supercritical scCO2 (scCO2) under conditions relevant to petroleum reservoirs and geological CO2 sequestration conditions. The GCMD results show that the smectite mineral, hectorite, containing interlayer alkali and alkaline earth cations with small ionic radii and high solvation energies (e.g., Na+ and Ca2+) does not intercalate CO2 and that the fully collapsed interlayer structure is the most energetically stable configuration. With Cs+ and Ba2+, the monolayer structure is the stable configuration, and CO2 should spontaneously enter the interlayer. With Cs+, there is not even an energy barrier for CO2 intercalation, in agreement with the XRD a...

Assessing the carbon sequestration potential of basalt using X-ray micro-CT and rock mechanics

Mineral carbonation in basaltic rock provides a permanent storage solution for the mitigation of anthropogenic CO2 emissions in the atmosphere. 3D X-ray micro-CT (XCT) image analysis is applied to a core sample from the main basaltic reservoir of the CarbFix site in Iceland, which obtained a connected porosity of 2.05–8.76%, a reactive surface area of 0.10–0.33 mm−1 and a larger vertical permeability (2.07 × 10−10 m2) compared to horizontal permeability (5.10 × 10−11 m2). The calculations suggest a CO2 storage capacity of 0.33 Gigatonnes at the CarbFix pilot site. The XCT results were compared to those obtained from a hydromechanical test applied to the same sample, during which permeability, electrical resistivity and volumetric deformation were measured under realistic reservoir pressure conditions. It was found that permeability is highly stress sensitive, dropping by two orders of magnitude for a −0.02% volumetric deformation change, equivalent to a mean pore diameter reduction of 5 μm. This pore contraction was insufficient to explain such a permeability reduction according to the XCT analysis, unless combined with the effects of clay swelling and secondary mineral pore clogging. The findings provide important benchmark data for the future upscaling and optimisation of CO2 storage in basalt formations.

Characterization of shale\u2013fluid interaction through a series of immersion tests and rheological studies

This paper presents qualitative techniques for evaluating shale–fluid interaction. Undesirable shale–fluid interactions lead to wellbore instability, formation damage and other problems that cost the petroleum industry millions of dollars annually. A simple desktop test method, such as immersion testing, can help production engineers choose the appropriate shale inhibitors such as salt, tetramethylammonium chloride (TMAC) and polymers that can effectively reduce the impact of oilfield fluids invading shale and causing it to swell or disperse. The swelling tendency of shale is highly dependent on clay mineralogy and other properties, such as porosity and permeability. A series of immersions tests was performed to study the combined and isolated effects of salt, TMAC, and polyacrylamide on preventing shale from becoming unstable. The merit of each fluid system in shale inhibition is probed for Woodford, Chattanooga and Pride Mountain shale. Rheology of bentonite slurries is studied with different salts and TMAC to probe their efficiency in preventing the swelling of bentonite clay. Additionally, rheology of bentonite with anionic and cationic polyacrylamide and salt is investigated.

Diffusion of Water through the Dual-Porosity Swelling Clay Mineral Vermiculite.

Prediction of water and solute migration in natural clay-based materials requires a detailed understanding of the roles played by different porosity types (around or inside clay particles) on the overall transfer process. For smectite, a reference material for the design of migration models, this discrimination is complex because of osmotic swelling of the structure under water-saturated conditions. Diffusion experiments with a water tracer (HDO) were conducted on 0.1-0.2, 1-2, and 10-20 μm size fractions of Na-vermiculite, a swelling clay mineral with no osmotic swelling. Results obtained for the two finest fractions suggest that osmotic swelling and the associated impact on pore structure are responsible for the low De values reported in the literature for smectite compared to those of vermiculite. When considering only interparticle porosity, De values for vermiculite are similar to those reported for nonporous grains (Na-kaolinite and Na-illite). This indicates that interparticle porosity has a primary effect on the overall water diffusion process, whereas interlayer porosity is shown to imply a small proportion of HDO adsorption. This study provides evidence that vermiculite is a promising reference mineral for the understanding of the roles played by pore structure and mineral-water interaction in the transport properties of water in claystones and for associated refinement of dual-porosity diffusion models.

Re-injection feasibility study of fracturing flow-back fluid in shale gas mining

Fracturing flow-back fluid in shale gas mining is usually treated by re-injecting into formation. After treatment, the fracturing flow-back fluid is injected back into the formation. In order to ensure that it will not cause too much damage to the bottom layer, feasibility evaluations of re-injection of two kinds of fracturing fluid with different salinity were researched. The experimental research of the compatibility of mixed water samples based on the static simulation method was conducted. Through the analysis of ion concentration, the amount of scale buildup and clay swelling rate, the feasibility of re-injection of different fracturing fluid were studied. The result shows that the swelling of the clay expansion rate of treated fracturing fluid is lower than the mixed water of treated fracturing fluid and the distilled water, indicating that in terms of clay expansion rate, the treated fracturing flow-back fluid is better than that of water injection after re-injection. In the compatibility test, the maximum amount of fouling in the Yangzhou oilfield is 12mg/L, and the maximum value of calcium loss rate is 1.47%, indicating that the compatibility is good. For the fracturing fluid with high salinity in the Yanchang oilfield, the maximum amount of scaling is 72mg/L, and the maximum calcium loss rate is 3.50%, indicating that the compatibility is better.

Alteration characteristics of granite contact zone and treatment measures for inrush hazards during tunnel construction – A case study

Several large-scale mud and water inrush events occurred during excavation of the Denghuazhai Tunnel at a depth of 175 m in the contact zone between geodic granite and tuff. By analyzing the inrush process, the characteristics of the inrush hazards, such as high pressure, abundant water, high mud and sand content and strong destructive power, were revealed. In addition, the inrush hazards were intermittent, uncertain and sudden. An intrusive contact zone between geodic granite and tuff was revealed by regional geological investigation. Large-scale alteration occurred both in geodic granite and tuff near the contact zone. Petrographic analyses indicated that alteration to albite, sericite and kaolinite occurred in geodic granite, and alteration to quartz and montmorillonite took place in tuff gradually toward the contact zone. Furthermore, the changes were gradational within and between various alteration grades. The closer to the contact zone, the higher degree of alteration, the less the primary minerals including quartz, K-feldspar and plagioclase, the more the secondary minerals such as sericite and clay minerals. Tests on porosity, saturated water content and uniaxial compressive strength indicated that alteration led to significant deterioration of physical and mechanical properties of rocks (except for silicified tuff). Especially, for the zonal clay in the central area of contact zone, the physical and mechanical properties were poor and obvious swelling, disintegration and argillation were observed. Tunnel excavation triggered swelling, disintegration and argillation of clay, leading to several large-scale inrush events. In terms of treatment of inrush hazards, first of all, a comprehensive exploration method based on petrographic analyses, geophysical detection and borehole drilling was established according to the alteration characteristics, so as to identify the scale and composition of the altered zone. The principle of “consolidation before removal” was adopted to deal with the inrush deposits for breach sealing and reinforcement. Energy release and stress reduction during tunnel construction and regular drainage during operation were achieved by dewatering measures, namely, “drainage supplemented by sealing, water drainage and solids remaining”. Reinforcement measures, including full-face curtain grouting and double-layer pipe sheds, were adopted to reinforce and seal the highly disturbed rock and soil in advance. Finally, technical measures, including “bench excavation, enhancement of support stiffness and timely installation of secondary support”, were employed to effectively prevent large deformation in disturbed rock masses. With the above measures, the left and right tunnels of the Denghuozhai Tunnel have passed through the altered zone successfully.

Viscosity reduction mechanism in high temperature of a Gemini viscoelastic surfactant (VES) fracturing fluid and effect of counter-ion salt (KCl) on its heat resistance

In the past several decades, Gemini viscoelastic surfactant has been applied for many cases due to its specific properties, including clean fracturing fluid. As we know that counter-ions can greatly promote the micelle aggregation of VES and show important effect on its heat resistance. Potassium chloride, as a normal additive for fracturing fluids to control the clay swelling, was investigated as such counter-ions in the context. Thus, a clean fracturing fluid with good heat resistance could be obtained by studying the viscosity reduction of the fluid prepared from a novel Gemini VES. The results of molecular structure characterization showed that potassium chloride has no effect on the surfactant molecular structure in rheological tests at high temperature. Based on the rheological tests, it can be concluded that the viscosity reduction at the test conditions is mainly of the micelle dissociation. Analysis results, such as microstructure comparison and the dynamic light scattering, suggested that potassium chloride can facilitate the micelles aggregation and entanglement, especially making the micelles tighter. In this way, the fluid could keep higher viscoelasticity at higher temperature and certain shear rate. Based on this mechanism, an improved VES fracturing fluid could be achieved via iterative formation adjustment, whose final viscosity could be maintained about 40 mPa s at 160 °C during 120 min.

Evaluation of enhanced oil recovery fromclay-rich sandstone formations

ABSTRACTIn the last few years, there has been a growing interest in smart water (SW) flooding as economically and environmentally friendly method to Enhanced Oil Recovery (EOR) in sandstone and carbonated reservoirs. Formation damage especially fines migration and clay swelling by lowering salinity and changing the ionic environment, causes the significant decrease in permeability of the sandstone reservoirs. In this study, an experimental study has been undertaken to illuminate the effect of formation damage during smart water injection as the function of clay types. The state of the art procedure has been established in direction of sandpack construction containing favorable clay content. Injection of smart water was performed in sandpacks with different clay types (montmorillonite and kaolinite). The results show that the presence of montmorillonite augments formation damage and enhances oil recovery. Analyzing Interfacial Tension (IFT) experimental data showed that interaction of oil/SW had no great influence on increasing oil recovery. The results have been achieved based on extensive experiments including Differential Pressure (DP) measurements, Zeta potential, and Recovery Factor (RF). Two mechanisms were proposed to interpret permeability reduction and amount of oil produced values which are clay swelling, and detachment/re-attachment for montmorillonite and kaolinite, respectively.

Experimental study on the gas phase permeability of montmorillonite sediments in the presence of hydrates

Permeability is a key parameter influencing fluids flow capacity and the gas production rate of the marine hydrate-bearing sediments. In this study, a series of experiments were carried out to find out the dependence of the gas phase permeability of montmorillonite on different hydrate saturations at effective axial stresses of 1 MPa, 3 MPa. And an experimental study of the decomposition of methane hydrate (MH) by depressurization was carried out. It is found that with the increase of gas hydrate saturation, the gas phase permeability of montmorillonite shows a trend of decreasing first and then increasing, due to the effect of blockage of hydrate particles and the increase of pores in inter-aggregate zones during methane hydrate formation. Furthermore, the gas phase permeability of clay clearly decreases gradually with the increasing decomposition time under different hydrate saturations, due to the formation of the bound water and the swelling of clay. The magnitude of CH4 coefficient of permeability Ka and that of transmission D∗ reache 10−7and 10−8, respectively. Ka is also known as hydraulic conductivity in the Darcy law. It is defined as the unit flow rate under the unit hydraulic gradient, indicating the difficulty of the fluid passing through the pore skeleton. And D∗is the coefficient of transmission based on a modified form of Fick's law, which is a function of the volume-mass properties of the soil and the gas density. After the complete decomposition of the hydrate, the permeability coefficient Ka decreases with the increase of initial hydrate saturation when 4.02%≤Sh≤15.15%. However, 15.15%≤Sh≤27.26%, the values of Ka increase with the increase of initial hydrate saturation. These experiments helped us understand some important aspects of MH behavior such as saturation of hydrate formation, effective stress, and permeability change during decomposition. This work could be useful to research on the production efficiency of marine gas hydrate reservoir.

Effect of water on methane adsorption on the kaolinite (0 0 1) surface based on molecular simulations

CH4 adsorption isotherms of kaolinite with moisture contents ranging from 0 to 5 wt% water, the effects of water on maximum adsorption capacity, kaolinite swelling, and radial distribution function were modelled by the implementing combined Monte Carlo (MC) and molecular dynamics (MD) simulations at 293.15 K (20 °C) and a pressure range of 1–20 MPa. The simulation results showed that the absolute adsorption of CH4 on both dry and moist kaolinite followed a Langmuir isotherm within the simulated pressure range, and both the adsorption capacity and the rate of CH4 adsorption decreased with the water content increases. The adsorption isosteric heats of CH4 on kaolinite decreased linearly with increasing water content, indicating that at higher water contents, the interaction energy between the CH4 and kaolinite was weaker. The interaction between kaolinite and water dominates and was the main contributing factor to kaolinite clay swelling. Water molecules were preferentially adsorbed onto oxygen and hydrogen atoms in kaolinite, while methane showed a tendency to be adsorbed only onto oxygen. The simulation results of our study provide the quantitative analysis of effect of water on CH4 adsorption capacity, adsorption rate, and interaction energy from a microscopic perspective. We hope that our study will contribute to the development of strategies for the further exploration of coal bed methane and shale gas.

Impairment of Fracture Conductivity in the Eagle Ford Shale Formation

Summary Fracture conductivity in shale formations can be greatly reduced because of water/rock interactions depending on the properties of formation rock and reservoir/fracture fluids. The mechanisms of water damage to fracture conductivity include clay swelling, surface softening, excessive proppant embedment, and fines migration caused by fracture-surface spalling and failed proppant particles. Fracture conductivity is influenced by closure stress, bulk and surface rock mechanical properties, fracture-surface topography, fracture-surface elemental composition, rock mineralogy, and proppant type and concentration, among other factors. This paper presents a study considering several of the aforementioned factors, centered primarily on saline-water-induced fracture-conductivity impairment of the Eagle Ford Shale Formation and its five vertical lithostratigraphic units. Laboratory experiments were conducted to investigate and quantify the effect of flowback water on fracture conductivity for samples of Eagle Ford Shale. The majority of test samples were obtained from an outcrop in Antonio Creek, Terrell County, Texas, while the remaining samples were obtained from downhole core provided by an industry partner. The different lithostratigraphic units present in the Eagle Ford Shale formation were accounted for. Saline water with a chemical composition similar to that of the typical field flowback water was used. Fracture-conductivity measurements were conducted in three stages. In the first stage, dry nitrogen was flowed to ascertain the undamaged initial fracture conductivity. In the second stage, the saline solution was injected into the fracture until steady-state behavior was observed. In the third and final stage, dry nitrogen was once again flowed to quantify the recovered fracture conductivity. Reported mechanical properties from the same outcrop-rock samples, consisting of Poisson's ratio and the Brinell hardness number (BHN), were considered in this study. In addition, reported mineralogy obtained by use of X-ray-diffraction (XRD) microscopy was taken into consideration. The elemental composition along the fracture surface was obtained by use of X-ray-fluorescence (XRF) microscopy, and fracture-surface topography was obtained by use of a laser surface scanner and profilometer. Results support findings that bulk and surface mechanical properties influence fracture conductivity, as well as surface topography and related attributes such as fracture surface area. Furthermore, the bulk mineralogical composition of the rock and the elemental composition of the rock fracture surface have a significant effect on fracture conductivity when flowing saline water to simulate flowback. Clay content was observed to directly influence fracture conductivity. The results of this study show a loss of fracture conductivity for the Eagle Ford Formation ranging from approximately 4 to 25% after flowing saline water, compared with the initial conductivity measured by flowing dry nitrogen before saline-water exposure. This is not a large loss in conductivity caused by water damage, and suggests that water damage may not be the major cause of the large early decline rates observed in most Eagle Ford Shale producing wells.

Preparation and Application of a New Crosslinked Polyammonium as a Shale Inhibitor.

Despite the fact that a number of traditional shale inhibitors have been utilized widely in drilling operations, the same additive may be unfavorable for different drilling due to environmental protection requirements which limit scales of use. Hence, a series of polyammonium compounds was prepared from dimethylamine, epichlorohydrin, and melamine (DEM). To concentrate our efforts, we used both standard and extra methods to investigate the inhibitive properties of a melamine crosslinking agent using mud balls immersion tests, linear expansion measurements, laser particle distribution measurements, thermogravimetric analysis, and scanning electron microscopy. The anti-swelling rate of DEM-8 reached up to 92.3% when its concentration reached 0.8%. DEM-8 has strong inhibitive capability to bentonite hydration swelling. DEM-8 can affect the bentonite particle size at a large scale. It may adsorb on the surface of clay through hydrogen bonds and electrostatic interaction by an anchoring effect and a hydrophobic effect. Compared with a blank solution, DEM-8 displays high inhibitive ability against the hydration and swelling of clay. The mud ball is more stable in DEM-8 solution and its swelling degree is very low compared with that of the control test. The inhibition mechanism of DEM-8 to shale can be deduced in that hydrogen bonding, ion exchange, and anchoring effect help to control the hydration and swelling.

Comparative analysis of the EOR mechanisms by using low salinity and low hardness alkaline water

This paper discusses the application of low hardness alkali water compositions (LHAW) as a secondary and tertiary displacement agent for EOR. A comparative analysis of the impact of low salinity water (LSW) and LHAW water on interfacial tension, contact angle on rock, adsorption of ions, emulsion stability and clay swelling is presented. LHAW application contributes to the formation of stable water in oil (w/o) emulsions and a decrease in clay swelling compared to LSW. Adsorption values for both fluids are similar. Contact angle measurements show that both LSW and LHAW reduce interfacial tension compared to Synthetic Caspian Sea water (SCSW), by up to 17% and 94% respectively. Similar results were observed for contact angle measurements. Flooding experiments were conducted in secondary and tertiary modes. In secondary flooding the two water compositions LHAW-2 and LHAW-1 increased the oil recovery (%OOIP) in comparison with SCSW at water breakthrough, by 29% and 25% respectively. The final oil recovery increases were 21% and 15% respectively. In tertiary flooding, tests showed that LHAW-2 and LHAW-1 oil recoveries (%OOIP) compared to LSW were 13% and 10% respectively. The oil recovery rate for LHAW solutions was not linear versus lnt as was that for LSW. This was proposed as a consequence of emulsions generation while water-cut is below 50% however, above 50% water cut the rate stabilizes.

Study of the Influence of a Young Synthetic Leachate on the Hydromechanical Properties of a Swelling Clay

Study of the Influence of a Young Synthetic Leachate on the Hydromechanical Properties of a Swelling Clay

Mechanistic Modeling of Clay Swelling in Hydraulic–Fractures Network

SummaryHydraulic fracturing is the most effective technique used in the oil industry for economical production of hydrocarbon from very-low-permeability reservoirs. Recent experimental studies have indicated a change in hydraulic-fracture (HF) conductivity as the result of the interactions between fracturing fluid and shale matrix. Clay swelling is one of the well-known undesirable interactions of this kind. If clay swelling occurs on the surface of the HF, it can cause major damage to the overall performance of the fracture network. Thus, a detailed understanding of the clay-stability issue is essential for fracturing-fluid selection and operation planning.Clay-swelling-induced conductivity damage is primarily a function of rock mineralogy, fracturing-fluid composition, and formation-brine salinity. Thus, various levels of clay/water interaction are expected in different shale formations. In this study, we present a mechanistic approach to model clay swelling in various rock mineralogies including Barnett (clay-rich), Eagle Ford (calcite-rich), and Marcellus shales. Subsequently, we investigate the production loss caused by clay swelling in a realistic complex HF network. We used UTCOMP-IPhreeqc, a coupled multiphase reactive-transport simulator developed at the University of Texas at Austin, to comprehensively model this process. The ion hydration and the expansion of electrostatic double layer (EDL) were assumed to be the main clay-swelling mechanisms. Surface complexation and ion-exchange reactions were considered to capture the ion diffusion into the electrostatic double layer expansion. In each timestep of the simulation, the calculated volume expansion of clay materials exposed on the fracture surface was used to modify the fracture aperture. To evaluate the performance of a complex HF network after clay-swelling damage, the embedded discrete fracture model (EDFM) was applied.The simulation results indicated that the degree of clay swelling varies in different shale formations. On the basis of the clay content and the mineralogies that were considered in this work, a significant expansion in electrostatic double layer expansion was observed for the Barnett Shale when fresh water was injected. However, this effect was much lower in Eagle Ford and Marcellus shales. Similarly, the production loss in the HF network was substantial in the Barnett example. The contribution of the fractures far from the producing well in gas production significantly decreased after clay-swelling damage. The pressure-depletion profiles clearly showed the adverse impact of conductivity damage on fracture-network performance. The presented approach provides the capability to mechanistically model the clay stability and to approximate its impact on transport properties of HFs.

The role of the stress-path and importance of stress history on the flow of water along fractures and faults; an experimental study conducted on kaolinite gouge and Callovo-Oxfordian mudstone

The flow of water along discontinuities, such as fractures or faults, is of paramount importance in understanding the hydromechanical response of an underground geological disposal facility for radioactive waste. This paper reports four experiments conducted on kaolinite gouge on a 30° slip-plane and on realistic fractures created in Callovo-Oxfordian mudstone (COx) from France. Test histories were conducted that initially loaded the gouge material in step changes in vertical stress, followed by unloading of the sample in similar steps. This loading-unloading history showed considerable hysteresis in hydraulic flow, with only partial recovery of fracture transmissivity. This demonstrates the importance of stress history on fracture flow; consideration of just the current stress acting upon a fracture or fault may result in inaccuracies of predicted hydraulic flow. The stress dependency of fracture flow in both kaolinite and COx can be described by a power-law or cubic relationship, which is likely to be dependent on the fracture roughness, thickness of gouge material, saturation state, permeability of the host material, and clay mineralogy (i.e. swelling potential). The observed response of fracture transmissivity to normal stress in COx is a complex superposition of mechanical response of the fracture and the swelling of clay in the fracture surface. The stress-dependency of flow was also seen to be dependent on orientation with respect to bedding. A fracture perpendicular with bedding accommodates greater compression and results in a lower transmissivity. The orientation dependence is related to the anisotropic swelling characteristics of COx.

Effect of Cement on the Drying–Wetting Paths and on Some Engineering Properties of a Compacted Natural Clay from Oran, Algeria

The purpose of this paper is to study the effect of cement on the consistency limits, drying–wetting paths, hydraulic conductivity measured by oedometer and triaxial tests in the short and long terms, and durability during wetting and drying cycles on untreated and treated samples. The compressive strength of the soil was also measured at the end of the durability tests. The study was carried out on samples of the natural swelling clay of Mers El Kebir (Algeria) compacted under Standard Optimum Proctor conditions and treated with different percentages of cement. The results show that the liquid limit decreases, and the plastic limit increases with the amount of cement. In the case of the drying–wetting path, a decrease in the shrinkage limit suction and an increase in the shrinkage limit water content were observed when the percentage of added cement increased. The tests conducted to evaluate the hydraulic conductivity of the treated soil show an increase in permeability just after the treatment, followed a decrease as a function of the curing time. From the durability tests, it could be observed that the clayey soils stabilized by cement exhibit high performance and survive 12 cycles of wetting–drying testing.

A triterpenoid saponin as an environmental friendly and biodegradable clay swelling inhibitor

The drilling industry is motivated to develop high performance clay swelling inhibitors with good biodegradability and low toxicity. In this study, the non-ionic surfactant glycyrrhizin was obtained as Glycyrrhiza glabra root extract (GGRE) as a clay swelling inhibitor. The swelling inhibitive property of the biosurfactant was systematically evaluated through various experiments including mud making, filtration, shale cuttings recovery, sedimentation, scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA). We compare the performance of our surfactant with a synthetic surfactant (TX-100) and a commonly used clay inhibitor (KCl). Compared to the baseline swelling test without inhibitors, the aqueous solution of GGRE shows much more montmorillonite (Mt) loading capacity and fluid loss, less shale cuttings disintegration, unstable Mt dispersion, larger aggregated Mt particles, and lower Mt mass loss. The inhibitive performance of the GGRE was found to outperform that of the KCl. The results show that TX-100 does not provide inhibition. The compatibility with the drilling fluid formulation was investigated through the rheological and fluid loss analysis. GGRE is found to be compatible with the commercial drilling fluids additives. The inhibition mechanism was also investigated through wettability investigation and FT-IR analysis. The results show that GGRE can strongly reduce the hydrophilicity of Mt. From FT-IR spectra, the interaction between Mt and GGRE is obvious. Our results imply that GGRE possesses good inhibitive characteristic in hindering Mt swelling. The molecule of glycyrrhizin—the main component of GGRE—consists of a hydrophobic triterpenoid backbone, connected by glycosidic bonds to a hydrophilic group. The inhibition mechanism is hypothesized through the formation of a hydrophobic shell on Mt's surfaces; the hydrophilic group of the glycyrrhizin interacts with the oxygen atoms available on Mt's surfaces, while the hydrophobic part orients toward the aqueous phase. The results obtained from this research will be beneficial to enhanced oil recovery studies in Mt-rich formations.

Modelling clay–fluid interactions in montmorillonite clays

This study shows that flow properties and degree of swelling of sodium (Na) montmorillonite (MMT) clay depend significantly on the polarity of solvents. The behaviour of sodium MMT clays intercalated with fluids with a range of dielectric constants, from highly polar formamide (110) to very low-polarity toluene (2·4), using molecular dynamics simulations. These fluids are commonly found in landfill leachates and are identified as highly toxic by the Environmental Protection Agency. Typically, the higher the polarity of fluids, the lower is their mobility, resulting in retention inside clay interlayer, causing greater swelling and swelling pressure. From interaction energy calculations, it is observed that clay–clay electrostatic interactions contribute only 1–6% of the total clay–fluid or sodium ion–fluid interactions. This study suggests that hydration of clay surfaces and counter-ions are the dominating factors of clay swelling, rather than the interaction between negatively charged clay sheets. Also, at lower fluid concentrations, interlayer fluids show organised orientation. This study also provides insight into molecular mechanisms that lead to the macro-scale behaviour of swelling clays. Significant variation in flow properties and swelling of clays with fluids of different polarities are important considerations for landfill liner designs, as well as other geotechnical and geoenvironmental applications.