Search Results (95)

Developing ultra-high-temperature geothermal resources is challenging, as traditional drilling fluids, including foam systems, lack thermal stability above 160 °C. To address this key technical bottleneck, this study delves into the screening principles for high-temperature-resistant foaming agents and foam stabilizers. Through high-temperature aging experiments (foaming performance evaluated up to 240 °C and rheological/filtration properties evaluated after aging at 200 °C), specific additives were selected that still exhibit good foaming and foam-stabilizing performance under high-temperature and high-salinity conditions. Building on this, the foam drilling fluid system formulation was optimized using an orthogonal experimental design. The optimized formulations were systematically evaluated for their density, volume, rheological properties (apparent viscosity and plastic viscosity), and filtration properties (API fluid loss and HTHP fluid loss) before and after high-temperature aging (at 200 °C). The research results indicate that specific formulation systems exhibit excellent high-temperature stability and particularly outstanding performance in filtration control, with the selected foaming agent FP-1 maintaining good performance up to 240 °C and optimized formulations demonstrating excellent HTHP fluid loss control at 200 °C. This provides an important theoretical basis and technical support for further research and field application of foam drilling fluid systems for deep high-temperature geothermal energy development. Full article

Badminton is an intermittent sport with a diverse exercise profile that stresses both aerobic and anaerobic energy systems. The aim of this study was to compare the internal and external load profiles of multi-feeding (MF) drills and simulated match play (SMP) in elite junior badminton players, and to explore potential sex-based differences. Forty-two players (24 males (age 17.4 ± 2.6 years, training experience 9.9 ± 1.8 years) and 18 females (age 16.9 ± 2.9 years, training experience 9.4 ± 2.1 years)) completed MF and SM sessions while external load (e.g., relative distance, explosive distance, relative jumps) and internal load (heart rate [HR], session rating of perceived exertion [sRPE]) variables were recorded using inertial measurement units and HR monitors. Two-way ANOVA revealed that MF induced significantly greater external (p < 0.05) and internal (p < 0.001) loads compared to SM, with large effect sizes. Male players showed markedly higher jump frequency (1.60 n/min vs. 0.80 n/min) and maximum speed (19.80 km/h vs. 15.80 km/h), although HR and sRPE values were similar between sexes (p > 0.05), suggesting that female athletes may experience greater relative physiological load. These findings highlight the importance of using MF drills to target specific conditioning goals and reinforce the need for individualized training strategies considering sex differences. Full article

Rock-breaking cutters are critical components in tunneling, mining, and drilling operations, where efficiency, durability, and energy consumption are paramount. Traditional cutter designs and empirical process optimization methods often fail to address the dynamic interaction between heterogeneous rock masses and tool structures, leading to premature wear, high specific energy, and suboptimal performance. Topology optimization, as an advanced computational design method, offers transformative potential for lightweight, high-strength cutter structures and adaptive cutting process control. This review systematically examines recent advancements in topology-optimized cutter design and its integration with rock-cutting mechanics. The structural innovations in cutter geometry and materials are analyzed, emphasizing solutions for stress distribution, wear/fatigue resistance, and dynamic load adaptation. The numerical methods for modeling rock–tool interactions are introduced, including discrete element method (DEM) simulations, smoothed particle hydrodynamics (SPH) methods, and machine learning (ML)-enhanced predictive models. The cutting process optimization strategies that leverage topology optimization to balance objectives such as energy efficiency, chip formation control, and tool lifespan are evaluated. Full article

Coalbed methane (CBM), a significant unconventional natural gas resource, holds a crucial position in China’s ongoing energy structure transformation. However, the inherent low permeability, high brittleness, and strong sensitivity of CBM reservoirs to drilling fluids often lead to severe formation damage during drilling operations, consequently impairing well productivity. To address these challenges, this study developed a novel low-damage, plugging, and anti-collapse water-based drilling fluid gel system (ACWD) specifically designed for coalbed methane drilling. Laboratory investigations demonstrate that the ACWD system exhibits superior overall performance. It exhibits stable rheological properties, with an initial API filtrate loss of 1.0 mL and a high-temperature, high-pressure (HTHP) filtrate loss of 4.4 mL after 16 h of hot rolling at 120 °C. It also demonstrates excellent static settling stability. The system effectively inhibits the hydration and swelling of clay and coal, significantly reducing the linear expansion of bentonite from 5.42 mm (in deionized water) to 1.05 mm, and achieving high shale rolling recovery rates (both exceeding 80%). Crucially, the ACWD system exhibits exceptional plugging performance, completely sealing simulated 400 µm fractures with zero filtrate loss at 5 MPa pressure. It also significantly reduces core damage, with an LS-C1 core damage rate of 7.73%, substantially lower than the 19.85% recorded for the control polymer system (LS-C2 core). Field application in the JX-1 well of the Ordos Basin further validated the system’s effectiveness in mitigating fluid loss, preventing wellbore instability, and enhancing drilling efficiency in complex coal formations. This study offers a promising, relatively environmentally friendly, and cost-effective drilling fluid solution for the safe and efficient development of coalbed methane resources. Full article

The pore degree prediction method based on well logging interpretation for tight sandstone reservoirs cannot meet the requirements of timeliness and rapidity for well exploration decisions. This paper utilizes the logging parameters during drilling, combined with acoustic time difference experiments, dynamic and static parameter experiments, and full-scale drill bit rock-breaking simulation, to reveal the response characteristics of reservoir properties to the feedback information from logging and rock-breaking and establishes a pore degree prediction method. The results show that as the pore degree decreases, the dynamic and static elastic modulus increases, the rate of penetration decreases, the torque increases, the mechanical specific energy increases, and a mathematical relationship model between pore degree and mechanical specific energy is established, achieving real-time drilling prediction of pore degree. The new method has been applied in the NB block, and the coincidence rate with the well-logging interpretation results reaches over 83%. The research results have provided real-time predictions of reservoir pore degrees and improved the efficiency of exploration decisions. Full article

The growing demand for rare earth elements (REEs) in high-tech and green energy sectors has prompted renewed exploration of unconventional sources. Drill cuttings, which are commonly discarded during subsurface drilling, are increasingly recognized as a potentially valuable, underutilized secondary REE reservoir. This review adopts a mineral-first lens to assess REE occurrence, extractability, and recovery strategies from drill cuttings across various lithologies. Emphasis is placed on how REEs associate with specific mineral host phases ranging from ion-adsorbed clays and organically bound forms to structurally integrated phosphates, each dictating distinct leaching pathways. The impact of drilling fluids on REE surface chemistry and mineral integrity is critically examined, alongside an evaluation of analytical and extraction methods tailored to different host phases. A scenario-based qualitative techno-economic assessment and a novel decision-tree framework are introduced to align mineralogy with optimal recovery strategies. Limitations in prior studies, particularly in characterization workflows and mineralogical misalignment in leaching protocols, are highlighted. This review redefines drill cuttings from industrial waste to a strategic resource, advocating for mineralogically guided extraction approaches to enhance sustainability in the critical mineral supply chain. Full article

With the increasing depth of mining operations and the emergence of complex geological conditions, pneumatic down-the-hole (DTH) hammers have become an efficient drilling technology. This method utilizes high-pressure air to drive hammering actions for rock fragmentation. However, the layout and durability of tungsten carbide buttons significantly affect the rate of penetration (ROP). This study focuses on optimizing the button arrangement for large-diameter reverse circulation pneumatic DTH hammers to improve drilling efficiency. A numerical model incorporating zero-thickness cohesive elements was developed to simulate rock fracturing. A comparative analysis of 16 mm and 22 mm buttons under varying drilling pressures (1–1.8 kN) and impact energies (20–40 J) was conducted. Key metrics, including penetration depth, fragmentation range, stress-affected zone, and specific energy consumption, were analyzed. The results indicate that 22 mm buttons under 35 J impact energy and 1.4 kN drilling pressure exhibit superior performance, with optimal circumferential (47.2 mm) and radial (51.2 mm) spacing determined through stress superposition analysis. This configuration enhances the weakened rock strength zone, providing critical guidance for DTH hammer design. Full article

Aiming at the problem that drilling parameters are difficult to adjust in time for the driller due to the complex geological environment in underground coal mines, a drilling parameter control method based on online identification of drillability and multi-objective optimization of drilling parameters is proposed. A drillability grade identification model is established, with rotational speed and torque as input parameters, which can accurately identify the current drilling state. A multi-objective optimization model of the optimal drilling parameters is established with the mechanical specific energy and drilling speed prediction model as the objective functions, and the NSGA-II algorithm and TOPSIS algorithm are used for solutions and decision-making. A fuzzy PID controller is established. For the control of rotational speed parameters and drilling pressure parameters, the advantages and disadvantages of the fuzzy PID control method and the traditional PID control method are compared through simulation and experiments. A control method based on the drillability identification model and the multi-objective optimization model is established. According to the different drillability grades, the drilling parameters are adjusted in time to ensure the normal drilling state. By constantly approaching the optimal parameters through the drilling parameters, the drilling efficiency is improved. Through experimental verification, this control method effectively prevents the occurrence of drilling speed reduction and intermittent sticking and can adjust the drilling parameters to continuously optimize. Full article

Nowadays, the exploration of different deep subsurface energy-related natural resources (oil/gas, natural hydrogen, geothermal, among others) is gaining importance. The exploration of these deep subsurface resources can present several challenges, such as complex lithology to be drilled, high depth to be reached, and considerable rock hardness, among others. In this context, the implementation of methodologies focused on real-time operational efficiency improvement has gained attention. Mechanical specific energy (MSE), rate of penetration (ROP), and even vibrations are key indicators that can be combined and used for drilling process optimization and efficiency improvement. These indicators are linked to operational drilling mechanic parameters, such as weight on bit (WOB), rotary speed (RPM), torque (TOR), and flow rate (FLOW). Despite this, multi-objective research considering both MSE and torsional vibration (stick–slip) has been largely overlooked in drilling optimization studies. Therefore, the main objective of this paper is to analyze field data from carbonate reservoirs using a multi-objective optimization approach based on torsional vibration, by means of stick–slip and MSE analyses. The focus is to minimize MSE values and mitigate stick–slip using self-developed decision matrices which consider WOB, RPM, and FLOW as key elements. The research results demonstrated that FLOW is a crucial parameter for minimizing torsional vibrations and should be prioritized in drilling operations, also for mitigating undesirable events. The optimization process yielded optimal WOB values for each RPM range (from 100 to 180 [rev/min]) and FLOW range (from 2200 to 3900 [L/min]). The decision matrix revealed that regions with high desirability correspond to high RPM (above 120 [rev/min]), with WOB varying from 5 to 13 [tf], and FLOW rates above 2300 [L/min]. Critical drilling conditions occur when low RPM, low FLOW, and high WOB (above 13 [tf]) are applied, as these conditions and this combination of parameters are most susceptible to release severe torsional vibrations, indicating a higher risk of operational problems. Full article

Optimizing the drilling process is critical for the exploration of natural resources. However, there are several mechanic parameters that continuously interact with formation properties, hindering the optimization process. Rate of penetration (ROP) and mechanical specific energy (MSE) are considered two key performance indicators that allow the identification of ideal conditions to enhance the drilling process. Thus, the goal of this research was to analyze field data from pre-salt layer operations, using a 2D analysis of parameters as a function of depth, response surface methodology (RSM), and multi-objective optimization. The results show that the RSM method and multi-objective optimization provide better results when compared with 2D analysis of parameters as a function of depth. The RSM method can be used as a tool to analyze the effects of the independent drilling mechanical parameters (WOB, RPM, FLOW, and TOR) on the response variables (ROP and MSE) with a 95% confidence level. Through multi-objective optimization, it was possible to concomitantly achieve an ROP of approximately 22 ft/h and MSE of nearly 11 kpsi using the values of WOB, RPM, FLOW, and TOR of about 11 klb, 109 rev/min, 803 gpm, and 3 klb-ft, respectively. Using high WOB values, i.e., from the mean value up to the maximum value of approximately 43 klb, reflects a low ROP and most likely indicates an operation beyond the foundering point. High FLOW promotes a more efficient hole cleaning and higher rates of cuttings transport, thus preventing eventual in situ drill-bit sticking. Flow adjustment also ensures an adequate balance of dynamic bottom hole pressure, in addition to controlling the force impact force of the drilling fluid in contact with the rock being drilled, expressing importance in terms of efficiency and rock penetration. Finally, it is important to mention that the results of this research are not only applicable to hydrocarbon exploration but also to geothermal and natural hydrogen exploration. Values analyzed and presented with decimal precision should be logically focused as integers when in industrial application. Full article

The high initial cost of ground heat exchanger (GHE) systems, particularly in applications with significant annual building thermal load imbalances, remains a major barrier to their adoption. In traditional rectangular grid patterns of boreholes, thermal saturation in cooling-dominated buildings mainly affects the central zone, rendering central boreholes less effective. This study investigates an innovative approach to enhance the thermal performance of vertical GHEs by removing these central boreholes using the pygfunction Python package. The central borehole removal design (CBRD) was implemented across various building thermal loads and ground conditions, resulting in reduced borehole interaction and a substantial decrease in total GHE length. Specifically, the CBRD approach achieved up to 51% savings in total GHE length compared to traditional rectangular grid patterns, significantly lowering the initial cost without additional expenses. Although energy consumption savings over a 30-year period were modest (up to 2.2%), the initial cost savings were substantial. Further optimizations indicated that additional reductions in borehole length could be achieved by removing boreholes beyond the central ones, while still maintaining the maximum entering fluid temperature (EFT). Yet, additional optimizations are needed as achieving optimal configurations requires detailed information on factors such as available land area and drilling depth limits, which are site-specific. Full article

The story of the rise of “energy” usually centers on the Industrial Revolution and the coal-powered steam engine in nineteenth-century Western Europe. Although it often escapes notice, the Caribbean was actually the site of the first known use of a steam engine to power industrial manufacturing (on a sugar plantation) and the world’s first oil well (drilled by a US company in southern Trinidad). These “firsts” point toward energy’s roots in colonial and imperial projects of extraction in the Caribbean, revealing the centrality of race and the plantation in understanding energy capitalism and the current climate crisis. This article traces a Caribbean-attuned genealogy of “energy”. Today, energy is taken for granted as an abstract universal, but the concept was bound to specific forms of racial governance during the transition from sugar to fossil fuels as apex capitalist commodities. In tracing this genealogy, I rewrite the first two “laws of energy” as ethico-political statements on racial governance rather than descriptions of a pre-existing natural order. Adding to scholarship that has laid bare the relationship between biological sciences and race, I argue that energy sciences have also been central to sustaining (while occluding) racialized hierarchy. I then look at conceptions of energy in perhaps the world’s oldest petro-state (Trinidad, with brief comparisons to neighboring Venezuela) to elaborate Caribbean-attuned, speculative alternatives to the “laws of energy”. Full article

Pultruded carbon fiber-reinforced composites are attractive to the wind energy industry due to the rapid production of highly aligned unidirectional composites with enhanced fiber volume fractions and increased specific strength and stiffness. However, high volume carbon fiber manufacturing remains cost-prohibitive. This study investigates the feasibility of a pultruded low-cost textile carbon fiber-reinforced epoxy composite as a promising material in spar cap production was undertaken based on mechanical response to four-point flexure loading. As spar caps are primarily subjected to flexural loading, large-span four-point flexure was considered, and coupon testing was restricted to tensile modulus and compression strength assessment. High-resolution spatial fiber optic strain sensing was utilized to determine spatial strain distribution during four-point flexure, revealing consistent strain along the length of the part and proved to be an excellent option for process manufacturing quality examination. Additionally, holes with diameters of 2.49 mm, 5.08 mm, and 1.93 mm were drilled through the thickness of full-width parts to determine the feasibility of structural health monitoring of pultruding parts internal to wind blades via fiber optic strain sensing. Full article

This study investigates the intricate relationship between bit rock interactions and drilling parameters for multiple-diameter hole drilling scenarios. Two sets of experiments were conducted in the Drilling Technology Laboratory at Memorial University of Newfoundland (DTL-MUN) using a fully instrumented Large-scale laboratory Drilling Simulator (LDS). The study contained two critical stages. Pre-coring operations using various diameter coring bits were completed to ensure thorough analysis. Next, drilling using a 5-cutter Polycrystalline Diamond Compact (PDC) bit with a larger diameter than all pre-cored holes, at constant Weight on Bit (WOB) and Revolution per Minute (RPM), was performed. The type of rock used in the experiments is a high-strength gabbro formation. Results indicate that pre-cored holes exhibited higher Rates of Penetration (ROP) than un-pre-cored holes, reflecting improved drilling performance and higher torque due to reduced bit–rock interaction area. A distinct relationship was observed between bit–rock interactions, torque, ROP, Mechanical Specific Energy (MSE), and applied WOB in multi-diameter drilling. ROP decreased as the pilot hole diameter decreased due to increased bit–rock interaction. The recorded data of WOB and the torque responses showed a decrease in amplitude as the bit–rock interface area increased, suggesting a positive interaction between drilling efficiency and downhole conditions. The modified Maurer model found a correlation between increased pilot hole diameter and decreased effective rock strength. These results highlight the significance of conducting a thorough drilling parameter analysis and the need for additional study to clarify the underlying mechanisms influencing drilling performance in multi-diameter hole drilling scenarios. Full article

During roadway excavation, the presence of roof deterioration zones, such as layered spaces and weak interlayers, significantly affects the stability of the surrounding rock. To achieve timely and effective support for roadways, it is essential to utilize drilling measurement signals obtained during the construction of anchorage holes for the identification and prediction of these deterioration zones. This study systematically investigates the response characteristics of thrust, torque, and Y-direction vibration signals to different combinations of rock layers through theoretical analysis, laboratory experiments, ABAQUS dynamic numerical simulations, and field measurements. The results indicate that these drilling parameters effectively characterize variations in rock structure and strength, with distinct signal features observed particularly in roof deterioration zones. Based on these findings, this paper proposes a deep learning algorithm that employs Long Short-Term Memory (LSTM) recurrent neural networks for classification prediction, along with a random forest algorithm for regression prediction, aimed at the intelligent identification and prediction of roof deterioration zones. The algorithm demonstrates outstanding performance in both laboratory experiments and field tests, achieving a 100% recognition rate for layered spaces and a 96.6% accuracy for identifying deterioration zones, with high accuracy at lower values of mechanical specific energy (MSE). The proposed method provides significant insights for real-time monitoring and control of roof deterioration zones, enhancing the safety and stability of roadway excavations, and serves as a valuable reference for future research and practical applications. Full article