The development of ultrahigh-performance geopolymer concrete (UHPGC) has attracted considerable attention owing to its low carbon emissions and sustainable development. However, its rheological properties are affected by complex factors, which are difficult to control, limiting its engineering applications. Therefore, improving the rheological properties of UHPGC is critical. This study employed response surface methodology (RSM) to investigate the effects of granulated blast furnace slag (GBFS), alkali activator modulus (AAM), and water-to-geopolymer binder (W/B) on the rheological properties (plastic viscosity, yield stress) and compressive strength of UHPGC. The results confirmed the suitability of RSM for multi-objective optimization: at the optimal mix (60.9 % GBFS, AAM=1.44, W/B=0.33), plastic viscosity, yield stress, and compressive strength reached 3.15 Pa·s, 20.60 Pa, and 128.5 MPa, respectively. GBFS and AAM, along with their interaction, significantly influenced the rheological properties, providing a practical mix design reference for engineering application of UHPGC.

The rheological properties of cement slurries play a crucial role in the identification and mitigation of gas-migration issues in oil field applications. Rheological properties give for more fundamental investigation, more precise phenomenological description of flow properties and serve as datum for numerical simulations. Standard commercially available rheometers are typically utilized to implement those measurements. This work presents the constitutive modelling of cement slurries use cement type G as defined by the API. The categorisation established by the American Petroleum Institute is conducted at varying rates. Ground-grained blast furnace slag (GGBS) at 15% intervals ranging from 15% to 75%. Continued. Cement slurries often display multifaceted non-linear fluid behaviour, including viscoelasticity, yield stress, shear-thinning effects, thixotropy, and other related phenomena. Two crucial rheological properties of cement, the shear viscosity and the yield stress, have been intensively investigated. We found the optimal percentage of partial replacement of cement type G with GGBS, water/cement ratio, mixing methods, temperature, shear rate, pressure, and the thixotropic behavior of cement with GGBS. The result shows that when increase the partial replacement of GGBS the plastic viscosity and yield point increase with increase the percentage of GGBS and the optimal percentage is 45% and then decrease until reaching the percentage 75%.

Despite continuous advancements in drilling fluid technology, achieving a balance between operational efficiency, environmental compatibility, and effective filtration control remains a persistent challenge. In this study, two novel chitosan-based nanocomposites—magnetic and silica nanoparticles functionalized with a triazine–chitosan network crosslinked by glutaraldehyde (Fe3O4@SiO2@melamine–chitosan and SiO2@melamine–chitosan)—were synthesized and systematically evaluated as additives for water-based drilling fluids. The performance enhancement is attributed to the synergistic interactions between the chitosan backbone, triazine-rich melamine units, and the nanoparticle cores, which collectively promote strong interfacial bonding, improved dispersion stability, and effective fluid–solid interactions. Rheological and filtration evaluations demonstrated a pronounced reduction in both American Petroleum Institute and high-pressure/high-temperature fluid loss with increasing nanocomposite concentration, with SiO2@melamine–chitosan exhibiting superior filtration control. At a nanocomposite concentration of 3000 ppm, the standard filtration loss decreased from 13 to 7 mL per 30 min, while the HPHT filtration loss was reduced from 30 to 16 mL per 30 min. These improvements are associated with enhanced wellbore stability and reduced formation damage through the formation of thinner, less permeable filter cakes. The filter cake thickness decreased from 2.5 to 1.5 mm. Moreover, the incorporation of the nanocomposites led to a notable increase in yield point—particularly in systems containing functionalized magnetic nanoparticles—indicating improved suspension capacity and flow control, while plastic viscosity remained largely unaffected. The yield point increased from 16 to 30 lb per 100 ft2, while plastic viscosity remained within the range of 16–20 cP. Overall, the combined benefits of enhanced rheological performance, effective filtration regulation, together with the environmentally favorable characteristics associated with chitosan-based materials, underscore the potential of these surface-engineered nanocomposites as potentially environmentally compatible and efficient additives for advanced water-based drilling fluid formulations.

In the face of challenging downhole conditions, the fresh state behavior of cement grouts employed for well cementation is as crucial as their mechanical properties. If not properly formulated, their primary purpose of providing zonal isolation of the steel casing from the surrounding formation may not be fulfilled. This study presents a rheological analysis of innovative lightweight slurry formulations utilizing finely ground seashell waste powder as a complete substitute for metakaolin. Replacing metakaolin with seashell waste powder aims to mitigate the environmental impact of well cementation and improve the fresh state behavior. Investigations are conducted using powders derived from various seashell wastes( Crassostrea gigas , Pinctada maxima , Pecten maximus , and Crepidula fornicata ) without the addition of chemical additives. The influence of elevated temperature on gelation, Yield Stress (YS), and Plastic Viscosity (PV) of the seashell slurries is compared with that of a conventional geothermal formulation containing metakaolin. The development of strength under elevated pressure and temperature conditions, similar to those found in downhole environments, is also examined using the ultrasonic cement analyzer (UCA) technique. All slurries demonstrated shear-thinning behavior, with apparent viscosity decreasing as shear rates increase. The findings further reveal a reduction in PV and YS of all seashell waste powder-based slurries relative to the traditional formulation. Moreover, gelation of the slurries formulated with seashell powder occurred more slowly at both ambient temperature and 55 °C. At 85 °C temperature and 18 MPa confining pressure, the compressive strengths obtained from UCA results meet the minimum industrial requirement of 24 h, and the ultimate UCA compressive strength of the seashell slurries surpasses that of the conventional formulation. • The rheology of slurries with seashell waste powder for geothermal cementation was studied. • Seashell waste powder reduces the yield stress and plastic viscosity of slurries. • Gel strength in seashell powder slurries developed gradually at both room temperature and 55 °C. • At 18 MPa and 85 °C, the seashell slurries develop strength beyond the 24-hour minimum requirement. • Seashell waste powder helps maintain slurry pumpability without the use of chemical additives.

Effects of gypsum type, content and slag on the performance of sleeve grouting materials

ABSTRACT The present study investigates the potential of widely used supplementary cementitious materials (SCMs) such as fly ash (FA) and ground granulated blast furnace slag (GGBS) to improve the rheological and environmental performance of low-carbon cementitious pastes. Three binders consisting of 100% OPC, 25% FA, and 70% GGBS were tested at water-to-binder ratios of 0.4 and 0.45. The dynamic shear rheometer was employed to analyze shear-thickening behavior of various cementitious suspensions. Subsequently, the environmental life cycle assessment (LCA) was conducted within a “cradle-to-gate” framework, evaluating six environmental impact categories and proposing a novel approach to converting these impacts into a single environmental cost (USD). The results revealed that OPC suspensions exhibit the earliest and most pronounced shear-thickening onset, while 70% GGBS suspensions reduce global warming potential but increase acidification impact. In contrast, 25% FA suspensions minimize acidification impact. Moreover, the rheological behavior is significantly influenced by solid volume fraction (SVF) and particle morphology; 70% GGBS pastes demonstrate the highest yield stress (140 Pa) and plastic viscosity (1.61 Pa. s) at a w/b ratio of 0.4, attributed to their angular particle shape. The environmental cost of suspensions (100% OPC) is estimated at $13.92/m3, with OPC being the primary contributor. The findings highlight the potential of SCMs to enhance performance and reduce environmental impacts, supporting greater use of FA and GGBS for sustainable, low-carbon infrastructure development. Future research should focus on optimizing the combined use and dosage of FA and GGBS in low-carbon cementitious pastes to achieve a more effective balance among rheological performance, environmental sustainability, and economic viability. Equally important is the need to extend the assessment framework beyond the present scope by incorporating long-term performance and durability assessment, broader system boundaries, and more rigorous environmental cost evaluation should be incorporated to enable the development of robust and sustainable cementitious systems. Implications: India has set an ambitious goal of achieving carbon neutrality by 2070. In the coming years, a substantial increase in building construction is anticipated to accommodate the country’s growing population. However, this expansion threatens to hinder progress toward national sustainable development goals (SDGs) and commitments to the Paris Climate Agreement. Indian thermal power plants and steel plants produce substantial amounts of fly ash and slag, which are solid waste byproducts. To mitigate the environmental impact and reduce cement consumption, it is essential to utilize these materials in construction. By incorporating fly ash and slag as cement replacement materials, we can significantly decrease the carbon footprint of the construction industry, contributing to both sustainability and resource efficiency. The paper uniquely integrates the rheological properties of cementitious suspensions with a comprehensive environmental assessment, offering a dual perspective on performance and sustainability. A novel methodology has been proposed to consolidate environmental impacts into a single environmental cost, expressed in US dollars, providing a practical decision-making tool.

This research aims to evaluate the potential of kepok banana peel as a raw material for carboxymethyl cellulose synthesis and to assess its effects on the rheological properties and filtration of bentonite-based drilling mud. CMC is synthesized through a process of delignification, bleaching, alkalization, and carboxymethylation. CMC characterization includes alpha cellulose content, degree of substitution, purity, pH, FTIR, SEM, and EDS. The obtained CMC was added in drilling mud at concentrations of 3 g, 6 g, and 9 g, and the resulting mud was tested for mud rheology and filtrate volume. The results showed that the alpha-cellulose content was 91.60%, the degree of substitution was 1.0, and the purity was 88.17%, meeting the SNI CMC grade II standard. The application of CMC increased plastic viscosity (12–14 cP), yield point (19–21 lb/100 ft²), and gel strength (8–13 lb/100 ft² for 10 seconds; 12–17 lb/100 ft² for 10 minutes) as the concentration increased. The filtrate volume decreased from 15 ml to 13 ml/30 minutes, and the mud cake thickness decreased from 0.5 mm to 0.3 mm. The pH value was stable in the range of 9. It was concluded that CMC derived from kepok banana peel has the potential to serve as an environmentally friendly drilling mud additive.

HighlightsThe relationship between mixed aggregate particle size distribution and slurry rheological parameters was established.Tailings particle size distribution significantly affects slurry transport resistance, whereas flow velocity is relatively insensitive to particle size distribution.Particle segregation occurs under long-distance transport conditions, and particle size distribution significantly influences particle distribution.The particle size distribution of backfill aggregate is a key factor affecting the performance of the -long-distance pipeline transport of backfill slurry. However, the understanding of its impact on slurry flow behavior, transportation resistance, and particle distribution mechanisms remains incomplete and calls for further investigation. This study first obtained the rheological parameters of slurry and their variation laws under the influence of particle size distribution through rheological experiments. Subsequently, CFD numerical simulations are used to investigate the flow characteristics of slurry under long-distance transportation conditions. The findings demonstrate that a reduction in the mixed aggregate particle size leads to a significant increase in both the yield stress and plastic viscosity of the backfill slurry. The conveying distance shows a positive correlation with the slurry transportation resistance. Furthermore, the slurry exhibits plug flow behavior in both the horizontal and vertical pipe sections, whereas this plug flow pattern is no longer observed in the bend section. The tailings particles exhibit a distinct stratified distribution within the pipeline. In the horizontal pipe section, the graded tailings predominantly settle at the bottom, whereas the fine tailings remain suspended near the top. In contrast, in the vertical pipe section, the graded tailings tend to accumulate in the central zone of the pipe, while the fine tailings are dispersed along the pipe wall. As the content of graded tailings increases from 30% to 50%, both the zones with increased and decreased particle volume fractions expand, while the steady flow zone correspondingly shrinks. Meanwhile, the volume fraction of graded tailings at the bottom of the pipe rises significantly from 0.12 to 0.61. This research provides important theoretical support for the optimized matching and rational application of tailings particle size distribution in the design of long-distance pipeline transportation systems for mine backfill.

The use of supplementary cementitious materials (SCMs) and carbon capture, utilization, and storage (CCUS) technologies has become important for reducing CO2 emissions. This study explores the feasibility of using cement kiln dust (CKD) as a partial replacement for cement and CO2 mixing as an in situ carbon sequestration strategy in 3D concrete printing (3DcP) applications. The synergistic effects of CKD and CO2 mixing on the fresh and hardened properties of 3D printable mixes were investigated, including workability, yield stress, plastic viscosity, compressive strength, microstructural properties, and pH. Results showed that the static yield stress increased by more than 100% in the mixes with CKD and CO2 compared to the control. While CKD reduced compressive strength, CO2 injection mitigated this loss through early carbonation. The scanning electron microscopy images revealed increased ettringite formation in CKD samples, and thermogravimetric analysis confirmed up to 2.2% of CO2 uptake upon CO2 integration with CKD.

Effective cementing in deep and weak formations is crucial for maintaining good integrity, particularly when the fracture pressure margin is minimal. This work explores both experimental and practical applications of various lightweight cements and presents key findings. The achieved slurry densities range from 1000 to 2200 kg/m3, with compressive strengths reaching up to 72 MPa. The inclusion of zeolite at levels of 5% to 25% by weight of cement (BWOC) consistently reduces the clinker content by at least 30%. Additionally, zeolite increases water demand, enhances the gel structure, and facilitates the rapid development of strength. Metakaolin, utilized at concentrations ranging from 10% to 20%, improves mechanical properties and durability; however, higher dosages may prolong thickening time, requiring optimization of cobinders. Vermiculite retains strength at high temperatures (up to 1650 °F), reduces thermal conductivity, and enhances plugging efficiency in fractured rock. Gilsonite provides waterproofing, stability, and long-term durability with minimal water requirements. Using perlite at approximately 4% BWOC reduces plastic viscosity by about 30%, increases yield point by around 330%, and can enhance compressive strength by up to 88%. Furthermore, waste expanded perlite can boost strength by roughly 50% while decreasing CO2 emissions. Ground granulated blast-furnace slag (GGBS) at 30% BWOC optimizes the density-strength balance and reduces the permeability by approximately 50%, with field trials reporting a 33% reduction in CO2 emissions. Hollow glass microspheres and cenospheres achieve densities of about 1200-1600 kg/m3, with a moderate strength reduction (10-15%) beyond 30% inclusion. Silica fume (5-15%) enhances long-term strength and resistance in CO2-rich or marine environments. Foamed cement systems allow for extreme lightweighting (approximately 1000-1300 kg/m3), decreasing gas migration rates by about 60%. Cross-comparisons identify optimal blends such as SF + GGBS or MK + zeolite for creating stable, lightweight matrices. The adoption of these additives supports sustainability by reducing cement use and CO2 emissions by 25-40%, aligning lightweight cementing practices with both performance and environmental objectives.

Background: Water-based drilling fluids (WBDFs) remain the most widely used drilling fluids because they are less expensive and more environmentally acceptable than oil-based and synthetic-based fluids. Their performance depends heavily on rheological and filtration characteristics, which are highly sensitive to the chemical additives incorporated into the mud. This study explores the influence of manganese dioxide (MnO₂) nanoparticles on the rheological behavior and filtration performance of WBDF. Materials and Methods: MnO₂ nanostructures were synthesized using a modified chemical route and characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) to confirm their crystalline phase, bonding structure, and morphology. WBDF samples were then prepared with and without MnO₂ nanoparticles. Key parameters, including plastic viscosity, yield point, density, filtrate volume, and mud cake thickness, were measured to assess the effect of nanoparticle incorporation. Results: XRD analysis confirmed the formation of crystalline MnO₂, while FTIR spectra revealed strong Mn–O vibrations characteristic of MnO₂ structures. SEM imaging showed well-defined nanostructures suitable for fluid modification. Compared with the base WBDF, MnO₂ enhanced fluids demonstrated improved rheological stability, higher yield point and viscosity consistency, and a notable reduction in fluid loss. Additionally, mud cakes formed in the presence of MnO₂ exhibited reduced thickness and signs of structural modification, indicating improved sealing efficiency. Conclusion: The addition of MnO₂ nanoparticles significantly enhances the rheological and filtration properties of WBDF. These improvements suggest that MnO₂-modified WBDF can effectively minimize filtrate invasion into formations and provide more stable drilling performance.

In order to promote the high-quality utilization of solid waste-steel slag-this study prepared ground steel slag powder with specific surface areas of 400 m2/kg, 500 m2/kg and 600 m2/kg respectively. Different fineness levels of steel slag powder were used to replace cement to prepare ultra-high performance concrete (UHPC), with replacement rates of 20%, 30% and 40% respectively. The effects of fineness and dosage of steel slag powder on the workability, mechanical properties and microstructure of UHPC were further investigated. The results show that the incorporation of steel slag powder can significantly reduce the yield stress and plastic viscosity of UHPC, thereby increasing its fluidity, but also decreasing its thixotropy. The tensile properties of UHPC mixed with steel slag powder were all superior to those of the reference group. The compressive strength of UHPC prepared by using steel slag powder with a specific surface area of 400 m2/kg or 600 m2/kg instead of 20% cement was higher than that of the reference group. The compressive strength of UHPC mixed with 600 m2/kg specific surface area steel slag powder was generally stronger at the same dosage. At the same fineness, the mechanical properties of UHPC decreased gradually with the increase in steel slag powder content. The recommended dosage for the steel slag powder with a specific surface area of 400 m2/kg is 20%, which results in the best comprehensive properties in UHPC. At this time, compared with the reference group, the compressive strength increased by 3.35%, and the tensile strength increased by 20.73%. Moreover, adequate fineness of the steel slag powder can be achieved without excessive grinding energy, which contributes to sustainability.

The rheological performance of oil-based drilling fluids was enhanced using graphene nanosheets and graphene–boron nitride hybrid nanoparticles. Optimized rheology is critical for efficient cuttings transport, wellbore stability, and cost-effective drilling. Graphene nanosheets (100–1500 mg/L) increased apparent viscosity (AV) by up to 90% and plastic viscosity (PV) by up to 106% compared to the base mud across 140–240 °F, with negligible density change. The graphene–boron nitride hybrid system exhibited concentration-dependent nonlinear behavior: viscosities decreased at low concentrations (100–500 mg/L) but rose markedly at higher concentrations (1000–1500 mg/L), achieving up to 164% increase in AV and 71% in PV at 1500 mg/L and 240 °F relative to the base fluid. This synergistic effect arises from graphene’s lubricating properties combined with boron nitride’s structural reinforcement, enabling formation of a robust nanoparticle network that resists thermal thinning. These findings demonstrate that hybrid nanoparticles offer a tunable, effective strategy to customize drilling fluid rheology, improve hydraulic efficiency, reduce torque and drag, and lower operational costs in high-temperature environments.

Abstract The transport of Omani heavy crude oil poses significant thermal–hydraulic challenges due to its high viscosity, yield-stress characteristics, and sensitivity to desert ambient conditions. To address these complexities, a non-Newtonian COMSOL Multiphysics model was developed using the Bingham–Papanastasiou formulation. The system considered three serially connected AISI 1020 steel pipeline segments with fixed diameters of 0.106m, 0.1524m, and 0.2032m under non-isothermal conditions. A total of 647 simulations were conducted, varying geometric, thermal, and rheological parameters to capture velocity, temperature, pressure, head loss, heat loss, and power loss. The outputs were processed through feature engineering to derive normalized indices for heat and power losses, alongside an Efficiency Index and composite performance scores for systematic evaluation. Results revealed distinct trade-offs: some designs achieved minimal heat loss but demanded higher pumping power, while others minimized power loss at the expense of increased thermal dissipation. Designs maintaining stable mean transport temperatures within 296.5–297.1 K were identified as robust performers. Importantly, Design 8 is consistently the best choice when power efficiency is prioritized, while Design 1 proves superior under heat-focused operations. Together, they represent the two most robust and versatile pipeline configurations for sustainable and cost-efficient long-distance transport of Omani heavy crude oil. The optimal rheological window was determined as plastic viscosity ≈ 0.0018–0.0028 Pa·s and yield stress ≈ 10–10.7 Pa, enabling reduced pumping requirements and stable thermal gradients, thereby supporting balanced thermal–hydraulic performance under realistic operating conditions.

Impact of grinding technology and particle size on rheological behavior and tribological properties of chocolate compound matrices.

As a representative digital additive construction material, three-dimensional printed concrete (3DPC) imposes a synergistic rheological requirement on fresh cementitious mixtures, namely “pumpability–extrudability–buildability,” throughout the forming process. Rheological parameters and their temporal evolution not only govern the stability of the material during pumping, nozzle extrusion, and layer-by-layer deposition, but also directly determine interlayer interfacial integrity, geometric fidelity, and the development of macroscopic mechanical performance. This paper provides a systematic review of the regulation strategies and evolutionary characteristics of 3DPC rheology, with particular emphasis on how raw material composition, printing parameters, and multiscale evolution mechanisms influence yield stress, plastic viscosity, and thixotropic behavior. The time-dependent evolution of rheological properties is elucidated across multiple length scales, encompassing microscopic particle interactions and hydration-induced bridging, mesoscopic aggregate force-chain networks and particle migration, and macroscopic shear stimulation coupled with temperature–humidity effects. On this basis, it is further highlighted that existing models and characterization frameworks remain insufficient to capture the time-dependent structural evolution under realistic printing conditions. Therefore, the establishment of unified characterization standards, together with in situ rheological measurements and multiscale simulations, is urgently required to enable the coordinated optimization of material design and printing processes and to facilitate engineering-scale implementation.

This study aims to investigate the influence of clay mineral content on the rheological properties and long-term deformation stability of clays, and to establish a unified model capable of quantitatively describing the nonlinear rheological behavior of clays with different mineral compositions. Direct shear rheological tests were conducted on specimens prepared with different mixing ratios of bentonite, kaolin, and quartz. Combined with micro-mechanism analysis, the controlling factors of clay rheological behavior were explored. The experimental results show that the creep stress threshold, elastic viscosity, and average plastic viscosity decrease significantly with increasing clay mineral content. The rheological deformation exhibits distinct nonlinear characteristics, and clay mineral content plays a controlling role in the rheological behavior. Based on experimental and mechanistic analysis, a unified rheological model was established, which reflects the material origin of rheology and captures nonlinear rheological characteristics. This model can predict the entire time-history mechanical behavior of clays with different mineral compositions across the three stages of instantaneous deformation, decay rheology, and steady-state rheology under different shear stress levels using a single set of parameters. Validation was performed through direct shear rheological tests under 50 working conditions for five types of clay specimens, demonstrating good consistency between the model calculations and experimental results. The unified rheological model reveals the material origin and physical essence of clay rheology, demonstrates high universality, and advances the understanding of the influence of mineral composition on rheology from the current phenomenological qualitative description to quantitative calculation for the first time, significantly enhancing its engineering application value. This provides a more reliable tool for predicting long-term deformation and assessing the stability of clay foundations.

As global oil and gas exploration extends to deep and ultra-deep wells, high bottom-hole temperature is prone to deteriorating the gelation and rheological properties of water-based drilling fluids, which manifests as undesirable thickening or thinning at elevated temperatures. Therefore, the development of high-temperature resistant and stable drilling fluids is crucial for ensuring safe and efficient drilling operations, and the enhancement of high-temperature performance is typically achieved by adding drilling fluid treatment agents. The main objective of this study is to apply sodium acetate (SA) to drilling fluid systems, developing an economical and efficient non-polymer treatment agent with dual functions as a composite sodium-modifier and a rheological regulator. By-product sodium acetate (TRSA) is adopted to provide better cost-effectiveness while maintaining equivalent performance, and its universality across seven types of bentonites is verified. Three grades of sodium acetate were added to the bentonites as either composite sodium-modifiers or rheological regulators. After high-temperature aging, rheological parameters, including mud density, plastic viscosity (PV), yield point (YP), and gel strength, were measured in accordance with standard API methods. The results indicate that adding 2 wt.% TRSA to drilling fluid and subjecting it to hot rolling at 180 °C for 16 h keeps the viscosity at a high shear rate (1022 s-1) nearly unchanged (from 36 mPa·s to 37.5 mPa·s), while increasing the viscosity at a low shear rate (5.11 s-1) from 250 mPa·s to 1400 mPa·s, thereby effectively improving the shear thinning effect of the sodium-modified calcium-based bentonite water-based drilling fluid. Although TRSA increases the filtration loss from 21.8 mL to 30 mL, this can be reduced to 20-25 mL by co-extrusion sodium modification with sodium carbonate or by adding additional TRSA to sodium-modified bentonite. This study provides a novel perspective for significantly improving the gelation characteristics and rheological properties of bentonite suspensions at high temperatures through a special inorganic substance, while realizing resource reuse and cost reduction.

High-pressure and high-temperature (HPHT) drilling operations demand oil-based drilling fluids (OBDFs) with robust rheological stability, strong suspension capacity, and reliable filtration performance. This study investigates the mechanistic and performance advantages of a dual-organoclay (OC) formulation composed of Claytone-SF and Claytone-IMG 400, benchmarked against the individual components and the commercial additive MC-TONE. Comprehensive mineralogical and morphological characterization (XRD, XRF, PSD, SEM) was combined with density, electrical stability, sagging, viscoelastic, rheological, and HPHT filtration testing. The 1:1 dual-OC system increased electrical stability by 17.5%, increased yield point (YP) by 25%, improved the YP/PV ratio by 18.5%, and reduced filtrate volume and filter cake thickness by 17.5% and 12%, respectively. In practical drilling operations, the enhanced YP promotes efficient cuttings transport and Barite suspension, the moderated plastic viscosity (PV) improves hydraulic efficiency by limiting excessive pressure losses, and the reduced filtration loss enhances wellbore stability and reduces formation damage under HPHT conditions. These improvements are hypothesized to arise from a multiscale colloidal network formed by complementary interactions between the plate-like montmorillonite-rich Claytone-SF and the finer, clinochlore-bearing Claytone-IMG 400, leading to tighter particle packing, greater structural resilience, and more stable gel development in the nonaqueous medium. This mineralogical mechanism offers a distinct pathway that complements emerging biobased and surfactant-based shale stabilization strategies. The findings provide new insight into clay–clay interaction behavior in invert emulsions and demonstrate that tailored dual-OC systems can consistently improve OBDF performance under HPHT conditions. These results highlight the potential for mechanistically guided additive design to advance drilling fluid development for complex and thermally stressed wells.

The bulk density of the injection grout is an important factor, as its additional weight could cause damage to hardened decorative plasters. This can be particularly noticeable on larger surfaces. This study used five types of lightweight filler as a density-reducing component in hydrated lime-based grouts. The commonly used limestone filler was completely replaced by an expanded or granulated filler with a loose bulk density of up to 900 kg m − ³; the rheological properties of the prepared grouts were then studied using a hybrid rheometer. The lime grouts were non-Newtonian, shear-thickening fluids exhibiting rheopectic behaviour (i.e. they stiffened over time). The type of filler dramatically affected the flowability of the grouts. The yield stress and plastic viscosity of the grouts decreased when lightweight fillers were used. As the filler density decreased, the grouts became expectantly less stiff. However, they showed a higher proportion of elastic behaviour than viscous behaviour, indicating that they have a strong microstructure that is resistant to external influences. There was no increase in loss factor values at higher frequencies, indicating that there was no separation of the liquid from the grout structure. From a rheological point of view, expanded glass appeared to be the most effective of the lightweight fillers used.