Search Results (535)

Carbon fiber-reinforced polymer (CFRP) composites are increasingly used in lightweight structures; however, their poor thermal conductivity poses challenges during drilling, where excessive heat degrades the epoxy matrix. This study investigates the individual and combined effects of wax (0–2%) as a solid lubricant and graphene nanoplatelets (0–2%) as a heat dissipation enhancer on cutting temperature during CFRP drilling. A data-driven modeling approach based on response surface methodology (RSM) with dummy variables was developed using a full factorial design comprising 225 unique experimental conditions (9 formulations × 5 cutting speeds × 5 feed rates) with three replicates per condition, resulting in 675 individual drilling tests. The RSM model was fitted to the 225 condition means. The global RSM model achieved high predictive accuracy (R² = 0.9250, RMSE = 2.83 °C). Results show that increasing the feed rate reduces temperature by up to 29% and improves process stability, contrary to conventional metal cutting behavior. The addition of 2% wax reduced mean temperature by 11.3% and decreased thermal variability by 26%. Graphene exhibited an optimal concentration at 0.25%, yielding a 4.3% reduction in cutting temperature, with higher concentrations providing no additional benefit due to agglomeration. The combined effects of wax and graphene resulted in an optimal formulation containing 2% wax and 0.25% graphene, which provided the most favorable balance between low cutting temperature (46.1 °C) and enhanced thermal consistency (standard deviation = 3.53 °C). These findings provide practical guidelines for designing thermally regulated CFRP composites for high-performance drilling operations. Full article

In ultra-deep well drilling, directly measuring the static formation temperature (SFT) is highly time-consuming, as it requires extended shut-in periods for the wellbore to reach full thermal equilibrium, making it impractical for routine engineering operations. To overcome this challenge, this paper establishes a wellbore–formation transient temperature model (WFTM) and proposes an SFT inversion method based on the Improved Grey Wolf Optimizer (IGWO) and Radial Basis Function (RBF) neural network. The RBF network serves as a surrogate model to replace the WFTM during iterative optimization, avoiding the prohibitive computational cost of repeated WFTM evaluations and enabling rapid prediction of the transient wellbore temperature field. Meanwhile, the IGWO algorithm uses the measured bottomhole circulating temperature (BHCT) as a constraint to optimize the geothermal gradient in SFT inversion. Multi-well validation shows that the RBF surrogate predicts BHCT with relative errors consistently below 1%, demonstrating its effectiveness as a substitute for the WFTM. Compared with the direct iterative approach (IGWO-WFTM), the IGWO-RBF method yields slightly lower SFT inversion accuracy, but this deviation remains within engineering tolerances, and the computational time is reduced by approximately 18 times. Requiring only surface temperature and routinely measured BHCT, the proposed approach offers a practical and efficient pathway for real-time assessment of formation temperature during ultra-deep oil well drilling. Full article

The Hailijin uranium (U) deposit is one of the super-large U-deposits recently discovered in the Qianjiadian ore field, southwestern Songliao Basin. The ore bodies are mainly hosted in the lower member sandstones of the Upper Cretaceous Yaojia Formation and occur as multilayered tabular bodies. The nature and source of the ore-forming fluids remain unclear, limiting the understanding of the genetic type of the deposit. This study integrated drill-core observation, mineralogy, whole-rock geochemistry, in situ pyrite trace elements and sulfur isotopes, fluid-inclusion, and Raman spectroscopy to constrain ore-forming fluids. The host sandstones experienced hematitization, limonitization, carbonate cementation, clay alteration, sulfidation and bleaching. Pitchblende and coffinite occur as submicron grains in dissolution pores of quartz and feldspar, on clay-mineral surfaces and within mobile organic matter (OM), commonly associated with pyrite and sphalerite. The ores and gray mineralized sandstones are enriched in U, Mo, Re, Co, Ni, Zn and Pb, and syn-ore pyrite shows positive correlations between U and As, Mo, Cu, Zn, Se and Sb. Mineralization-related fluid-inclusion assemblages occur mainly in syn-ore dolomite/ankerite cements and in secondary trails along microfractures in detrital quartz; they yield homogenization temperatures of 130–190 °C and salinities of 3–8 wt.% NaCl eq., higher than the normal burial temperature of the basin (80–90 °C), especially meteoric fluid. Raman and gas-chromatographic analyses indicate carbonaceous matter, CH₄, CO₂, H₂ and minor O₂. Pyrite δ³⁴S values of −49.24‰ to −23.1‰ indicate isotopically light reduced sulfur ultimately related to microbial sulfate reduction and/or thermal decomposition of sulfur-bearing OM, whereas thermochemical sulfate reduction was unlikely to be dominant. Therefore, the ore-forming fluid is interpreted as a low-temperature, low-salinity organic-rich fluid, most likely derived from U-enriched source rocks at depth, and the uranium mineralization is closely associated with the exudation of such deep-derived organic fluids. Full article

Post-welding vibratory stress relief (VSR) has been studied extensively for its capability of decreasing welding residual stresses (RS). This study examines the effectiveness of VSR applied on butt-welded thick sheets of high-strength low-alloy steel. The effect of thermal stress relief (TSR) was examined simultaneously. X-ray diffractometry (XRD), hole drilling method (HDM), and instrumented indentation technique (IIT) were employed for evaluating RS distribution. Global mechanical properties of the weld joint were assessed using tensile tests, bending tests, and Charpy impact tests. Hardness was employed to assess local variation in mechanical properties. The microstructure was observed through light optical microscopy (LOM) and electron back-scatter diffraction (EBSD). It was found that RS redistributed after VSR. The overall decrease in RS could be seen after VSR; however, the scatter in RS increased. TSR, on the other hand, resulted in the decrease in both magnitude and scatter of RS. Peak values of the post-welding RS were evaluated in the range of −200 to 200 MPa; meanwhile, the mean RS was within the range of −100 to 100 MPa. After TSR, RS was mostly within the range of −50 to 50 MPa. After VSR, RS was found to lie mostly within the range of −100 to 200 MPa with peak values being close to the yield strength. VSR had no adverse effect on the structural integrity of the weld joint. No significant differences in the microstructure were seen among as-welded, TSR, and VSR conditions. Full article

Material extrusion additive manufacturing, commonly implemented as fused deposition modeling (FDM) or fused filament fabrication (FFF), has evolved into a manufacturing route for reinforced thermoplastic composites, including particle-filled, short-fiber-reinforced, and continuous-fiber-reinforced systems. The process is governed by a layer-by-layer thermal cycle. Deposited roads cool rapidly, are repeatedly reheated by subsequent material deposition, and finally cool non-uniformly as part of the growing structure. This thermal history generates residual-stress that may cause warpage, build–platform detachment, delamination, dimensional error, and reduced mechanical performance. This review synthesizes residual-stress formation, measurement, modeling, parameter effects, and mitigation in material-extruded reinforced thermoplastic composites, with emphasis on short and continuous-fiber systems. Stress formation is discussed in terms of constrained thermal contraction, crystallization shrinkage, anisotropic stiffness, fiber-constrained deformation, porosity, and fiber–matrix thermal expansion mismatch. Experimental methods, including hole drilling, layer removal, curvature methods, embedded fiber Bragg gratings, digital image correlation, photoelasticity, and warpage metrology, are critically compared for anisotropic and porous printed composites. Analytical and numerical models are reviewed from layerwise shrinkage formulations to crystallization-coupled thermo-viscoelastic finite element simulations. Finally, mitigation strategies are evaluated. A central conclusion is that reinforcement can suppress visible distortion while increasing stress retained in a stiffer structure. Therefore, warpage alone is not a sufficient residual stress metric. Full article

Wellbore fluid flow and heat transfer are strongly coupled during drilling and well construction, where temperature, pressure, rheology, gas behavior, transient operations, and cementing displacement jointly affect pressure-window control and wellbore safety. This review synthesizes advances in coupled wellbore thermal–hydraulic numerical simulation, emphasizing governing equations, discretization strategies, coupling algorithms, rheology and turbulence closures, verification and validation, computational efficiency, uncertainty quantification, and AI-assisted deployment. A bibliometric-guided critical review was conducted using an 841-record Web of Science corpus, 79 screened technical records, 86 screened OnePetro field-facing records, and representative prior reviews. CiteSpace was used to identify knowledge structure and thematic evolution, while screened records were coded by governing physics, numerical method, closure assumption, model output, validation evidence, and deployment relevance. The literature is organized into five model families: wellbore temperature and heat transfer; annular non-Newtonian flow, rheology, turbulence, and CFD; pressure-window and transient hydraulics; cementing displacement and well-construction flow; and AI-assisted calibration and deployment. The synthesis shows that field-deployable simulation requires consistent state variables, transparent closure hierarchies, benchmark validation, uncertainty reporting, CFD-to-well-scale transfer, reduced-order implementation, and physics-constrained AI updating. Full article

Deep coal reservoirs are characterized by abundant microfractures and cleats, resulting in frequent wellbore instability during long horizontal drilling operations. To address this issue, a biodegradable gel plugging agent (XZ) was synthesized from acrylamide (AM) and carboxymethyl cellulose (CMC) via an orthogonal crosslinking strategy. The gelation behavior, swelling capacity, rheological properties, mechanical strength, thermal and salt resistance, plugging performance, self-degradation characteristics, reservoir protection capability, and drilling-fluid compatibility of XZ were systematically evaluated. The results showed that XZ formed a stable three-dimensional crosslinked network with good thermal stability (T₀ = 116 °C, T₁/₂ = 445 °C). The synergistic effects of covalent and ionic crosslinking endowed the gel with high swelling capacity, mechanical strength, and plugging ability. XZ exhibited excellent temperature and salinity tolerance, with a degradation rate exceeding 90% after 5 days. After degradation, the filter cake became significantly thinner and core permeability recovery reached approximately 80%, demonstrating effective reservoir protection. Moreover, XZ significantly increased drilling-fluid viscosity, reduced fluid loss, and enhanced plugging performance. The XZ-based drilling fluid system integrates efficient plugging, self-deplugging, and reservoir protection functions, providing a promising solution for safe and efficient drilling in deep coalbed methane reservoirs. Full article

The aim of the presented study is to verify the possibility of forming hybrid adhesive-mechanical joints between aluminum sheet and PP matrix composites reinforced with carbon and glass fibers using thermal drilling technology. The research responds to weight reduction trends in the automotive and aerospace industries, seeking joining methods that preserve the continuity of reinforcing fibers. The methodology included applying an experimental organosilicate agent to the aluminum, sequential thermal drilling, and an innovative modification of bushing geometry using a 9.3 mm diameter tool. Joint quality was evaluated via tensile shear testing and non-destructive analysis using computed tomography (CT). Results showed that the organosilicate layer significantly increased the load-bearing capacity and adhesion of glass fiber joints. Hybrid joints exhibited higher energy absorption than purely adhesive joints. The proposed bushing geometry modification led to a statistically significant increase in total dissipated energy (by 28% to 37%) and a desired change in the failure mechanism from composite pull-out to bushing shear. CT analysis confirmed the preservation of fiber integrity through radial deflection. Consequently, hybrid joining via thermal drilling with modified geometry effectively utilizes the mechanical properties of metallic materials in multi-material structures. Full article

2.5D C/SiC composites are characterized by high hardness and brittleness. These properties render the composites prone to fiber fracture, burr formation and matrix damage during grinding for hole-making. This study systematically investigates the material removal mechanism, tool wear behavior and machining quality evolution process during diamond core drill grinding for hole-making. Through experiments, the effects of grinding angle and grinding force and the thermal effects on material removal characteristics and hole wall machining quality were analyzed, and the stagewise characteristics of tool wear and the correlation between processing parameters and machining quality were clarified. The results indicate that the wear of diamond core drills undergoes a three-stage evolution: slight abrasive grain shedding at the initial stage, local damage and wear loss at the middle stage, and large-scale abrasive grain peeling followed by tool failure at the late stage. As wear aggravates, the machining axial force increases remarkably and the grinding temperature rises drastically. Hole wall defects gradually develop from minor initial fiber fracture into complex failure modes including burrs, fiber pull-out and matrix damage. In particular, the morphological degradation at the hole exit is the most severe. This study verifies that the optimization of process parameters and tool design can improve machining quality, and provides theoretical guidance and an experimental basis for the efficient and precise machining of high-performance composites. Full article

Background/Objectives: Thermal injury during implant osteotomy is a recognized complication of guided surgery. Closed guide architectures and metallic sleeves restrict coolant access to the drill–bone interface, reducing the effectiveness of conventional external irrigation. This study aimed to describe the design and fabrication of a 3D-printed surgical guide system with integrated internal irrigation channels and to evaluate its technical and clinical feasibility in guided implant surgery. Methods: The system was developed by integrating CBCT and IOS data into BlueSky Bio planning software. Irrigation channels were generated by CAD subtraction. Guides were fabricated by additive manufacturing—digital light processing (DLP) in biocompatible Asiga DentaGuide resin and, in one case, selective laser melting (SLM) in Mediloy metal—with metal auxiliary components incorporated where required. Channel patency was confirmed by flow equivalence testing and visual inspection. The design was evaluated for compatibility with the BioHorizons Pro Surgical Guide Kit and the Ticare Fidelis Kit. Clinical feasibility was assessed in two cases: maxillary All-on-6 rehabilitation and immediate implant placement in the esthetic zone. Results: Both guides were successfully fabricated with confirmed patent irrigation channels. Guide seating was verified through occlusal fenestrations and secured with fixation pins. Irrigation flow remained unobstructed throughout all osteotomy steps, and no guide-related or irrigation-related complications were observed. The system was integrated into standard drilling protocols without modification for either implant platform. Conclusions: This proof-of-concept study demonstrates the technical feasibility of an internally irrigated surgical guide across two implant systems and distinct clinical scenarios. The proposed design was successfully integrated into standard guided surgery workflows and maintained functional irrigation. Further in vitro thermal studies and prospective clinical investigations are required to evaluate its effect on temperature control. Full article

Accurate characterization and prediction of drilling fluid rheological properties under high-temperature and high-pressure (HTHP) conditions are core prerequisites for safe and efficient deep well drilling operations. To systematically clarify the thermobaric rheological laws and intrinsic coupling mechanism of high-density drilling fluids, this study takes 2.0 g/cm³ oil-based drilling fluid (OBDF) and water-based drilling fluid (WBDF) as research objects, and carries out full-scale rheological tests via a Fann iX77 HTHP rheometer under temperatures ranging from room temperature to 200 °C and pressures from atmospheric pressure to 200 MPa. The results show that the shear stress of both fluids is positively correlated with pressure and shear rate and negatively correlated with temperature. 150 °C is identified as the critical thermal thickening temperature for WBDF: above this temperature, polymer degradation and solid precipitation cause abnormal viscosity growth, and high shear rates can effectively alleviate this thickening effect by promoting the dispersion of precipitates. There are significant differences in rheological sensitivity between the two systems: WBDF rheology is dominated by temperature dependence, while OBDF exhibits high sensitivity to both temperature and pressure due to the compressibility of the oil continuous phase; temperature and pressure exert a mutual inhibitory effect on fluid rheology. The proposed Arrhenius–Powell one-step global coupled prediction model achieves favorable prediction accuracy for both OBDF and non-thickened WBDF, with the coefficient of determination (R²) no less than 0.96. The model can provide reliable basic parameters for HTHP wellbore hydraulic calculation and pressure loss prediction, fully meeting the accuracy requirements of field engineering applications. Full article

To address the potential ecological risks and environmental persistence of organosilicon-fluorine viscosity reducers in conventional silicone-fluoride drilling fluid systems, this work designs and synthesizes a non-organosilicon-fluorine, high-temperature, comb-shaped zwitterionic polymer viscosity reducer, AD-XSJ. The viscosity reducer is prepared via aqueous free-radical polymerization of acrylic acid (AA), acrylamide (AM), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and dimethyl diallyl ammonium chloride (DADMAC), and it exhibits low molecular weight, uniform molecular weight distribution, and excellent thermal stability. Analyses by FT-IR, thermogravimetry, particle size, zeta potential measurements and Electrostatic potential (ESP) demonstrate that AD-XSJ dismantles the bentonite network structure through the synergistic combination of hydrogen-bonding adsorption and electrostatic repulsion, releasing trapped free water and thereby substantially reducing viscosity and gel strength. Compared with conventional organosilicon-fluorine viscosity reducers, AD-XSJ exhibits superior viscosity reduction capability under high-solid, high-temperature, and high-salinity calcium-contamination conditions, achieving viscosity reduction rates of 33.3% and 50.0% in fluids contaminated with 10.0% NaCl and 1.0% CaCl₂, respectively. In field applications under conditions of high bentonite content and calcium contamination, the viscosity reduction rates reach 57.7% and 62.5%, accompanied by markedly improved rheological properties and an average borehole enlargement rate of only 5.7%, indicating effective shale inhibition and anti-sloughing performance. Integrating efficient viscosity reduction, dispersion stabilization, and inhibition capabilities, this viscosity reducer can replace traditional organosilicon-fluorine products, reduce potential hazards to aquatic ecosystems at the source, and holds considerable promise for engineering and environmentally conscious deployment. Full article

Under high-temperature and high-salinity drilling conditions, maintaining the stability of water-in-oil emulsions is critical for oil-based drilling fluids, while the roles of auxiliary emulsifiers with different ionic characteristics remain unclear. In this study, Span 80 was used as the primary emulsifier, and nonionic OP-4, anionic SDBS, zwitterionic EAB40, and cationic CTAB were introduced as auxiliary emulsifiers to construct blended emulsifier systems. The HLB value was controlled at 5.2–5.4, and the total emulsifier concentration was fixed at 6.0 wt%. The effects of auxiliary emulsifier type on interfacial tension, rheological behavior, electrical stability, droplet morphology, and thermal stability were systematically investigated. The Span80/OP-4 system exhibited the lowest interfacial tension, smallest droplet size, and best overall emulsion stability. In contrast, the Span80/SDBS system showed poor electrical stability due to weakened effective interfacial adsorption in Ca²⁺ brine. After aging at 120 °C, EAB40 promoted interfacial rearrangement, whereas CTAB weakened interfacial order. Further verification in 1.50 g/cm³ weighted oil-based drilling fluids showed that the Span80/OP-4 system maintained high electrical stability, low HTHP filtrate volume, and good sedimentation stability after aging at 140 °C. Full article

Maintaining effective fluid-loss control in water-based drilling fluids under coupled high-salinity, high-temperature, and high-density conditions remains a critical challenge in deep and ultra-deep drilling operations. In this study, a low-molecular-weight polymer fluid-loss additive (LM-ASQF) was synthesized via redox-initiated copolymerization of acrylamide, dimethyldiallylammonium chloride, and sodium allyl sulfonate. The synthesis route and proposed polymer structure were further illustrated to clarify the incorporation of amide, quaternary ammonium, and sulfonate functional units within the LM-ASQF molecular architecture. The polymer exhibited a controllable number-average molecular weight of 18.2–29.4 kDa with a unimodal distribution. Thermal analysis confirmed that no main-chain-dominated degradation occurred below 220 °C, indicating structural stability under high-temperature conditions. In drilling-fluid systems containing NaCl, CaCl₂, and mixed salts (0–20%), LM-ASQF maintained stable rheological properties, with apparent viscosity ranging from 26.1 to 41.6 mPa·s, while the API fluid loss was controlled within 5.8–11.2 mL. After thermal aging at 220 °C for 16 h, the API fluid loss remained below 13 mL in both freshwater and mixed-salt systems. In high-density systems (1.80–2.40 g/cm³), the drilling fluids preserved continuous rheological structures and showed no abrupt increase in filtration. Mechanistically, fluid-loss control was primarily attributed to synergistic interfacial adsorption of amide groups, hydration stabilization induced by sulfonate functionalities, and particle rearrangement-driven filter-cake densification, rather than viscosity enhancement through long-chain entanglement. This mechanism enables effective filtration control without excessive viscosity increase, thereby maintaining rheological compatibility under complex conditions. These results demonstrate that the low-molecular-weight design strategy provides a reliable approach for achieving stable fluid-loss control in water-based drilling fluids under high salinity, elevated temperature, and high-density conditions. Full article

Geothermal energy is a locally available, low-carbon resource that may support heat supply, building decarbonisation and regional energy diversification in non-volcanic crystalline settings. This study proposes an exploratory GIS-based approach for geothermal favourability mapping in the Guarda District, Central Portugal, where Hercynian granites, major fault systems and thermal and mineral water occurrences define a structurally controlled hydrogeothermal framework. Hydrogeochemical data from 54 groundwater abstraction points were integrated through silica-derived apparent geothermometric indicators, classical hydrothermal-parameter estimation and Empirical Bayesian Kriging Regression Prediction (EBKRP). Apparent silica-derived temperature indicators, circulation depth, geothermal gradient and theoretical thermal power were estimated, with log₁₀ transformed thermal power used as the dependent variable and distance to major mapped faults as the structural covariate. Apparent silica-derived temperature indicators range from 21.3 °C to 121.2 °C, with a mean of 64.6 °C, while estimated geothermal gradients range from 20.3 °C/km to 92.1 °C/km. Higher estimated values occur preferentially near NE–SW and NNW–SSE fault systems, suggesting that structural permeability may influence deep groundwater circulation. The interpretation explicitly acknowledges that, in low-temperature systems, dissolved silica may be influenced by chalcedony or amorphous silica control, as well as by cooling, mixing and incomplete re-equilibration during fluid ascent. The resulting map is interpreted as a screening-level favourability product, not as a definitive assessment of exploitable geothermal resources, and supports the prioritisation of future structural mapping, geophysical surveys, exploratory drilling, borehole temperature logging and applied geothermal assessment in fractured granitic terrains. Full article