Search Results (10)

In recent years, polycrystalline diamond compact (PDC) drill bits have seen significant advancements. They have replaced over 90% of the workload traditionally handled by roller cone bits and have become the predominant choice in energy drilling due to their superior efficiency and durability. However, PDC drill bits are susceptible to adhesion of rock cuttings during drilling in muddy formations, leading to mud accumulation on the bit surface. This phenomenon can cause drill bit failure and may contribute to downhole complications, including tool failure and borehole instability. The adhesion issue between PDC drill bits and mud rock cuttings underground is primarily influenced by the normal adhesion force between the drill bit surface and the mud rock cuttings. Therefore, biological non-smooth surface technology is applied to the prevention and control of drill bit balling. It is an optimal selection of biomimetic non-smooth surface structures with reduced adhesion and detachment properties. A non-smooth surface model for the PDC drill bit body is established through the analysis of the morphological characteristics of natural biological non-smooth surfaces. An experimental platform is designed and manufactured to evaluate the adhesion performance of non-smooth surface specimens. Indoor experiments are conducted to test the normal adhesion force of non-smooth surface specimens under varying morphologies, sizes, and contact times with clay. Finally, the anti-adhesion performance of the non-smooth surface unit structures is then analyzed. The normal adhesion force with a contact time of 12 h is as follows: 340 Pa of big square raised, 250 Pa of middle square raised, 190 Pa of small square raised, 315 Pa of big circular groove, 280 Pa of middle circular groove, 200 Pa of small circular groove, 225 Pa of big dot pit, 205 Pa of middle dot pit, and 130 Pa of small dot pit. Compared with the normal adhesion force of 550 Pa for smooth surface specimens with a contact time of 12 h, the anti-adhesion properties of the three non-smooth surface unit structure specimens designed in this paper were verified. We analyzed the anti-adhesion performance of non-smooth surface unit structures. At the critical contact time when the adhesion force tends to stabilize, the adhesion forces of different specimens are as follows: 330 Pa of big square raised, 237.5 Pa of middle square raised, 175 Pa of small square raised, 290 Pa of big circular groove, 250 Pa of middle circular groove, 160 Pa of small circular groove, 210 Pa of big dot pit, 185 Pa of middle dot pit, and 115 Pa of small dot pit. The results indicate that the anti-adhesion effect of small dot pit structures is the most effective, while the anti-adhesion effect of large square convex structures is the least effective. As the size of the unit structure decreases, it becomes more similar to the surface size of the organism. Additionally, a shorter contact time with clay leads to a better anti-adhesion effect. These findings provide new insights and research directions for the effective prevention and control of mud wrapping on PDC drill bits. Full article

Nowadays, brain–computer interface (BCI) systems are frequently used to connect individuals who have lost their mobility with the outside world. These BCI systems enable individuals to control external devices using brain signals. However, these systems have certain disadvantages for users. This paper proposes a novel approach to minimize the disadvantages of visual stimuli on the eye health of system users in BCI systems employing visual evoked potential (VEP) and P300 methods. The approach employs moving objects with different trajectories instead of visual stimuli. It uses a light-emitting diode (LED) with a frequency of 7 Hz as a condition for the BCI system to be active. The LED is assigned to the system to prevent it from being triggered by any involuntary or independent eye movements of the user. Thus, the system user will be able to use a safe BCI system with a single visual stimulus that blinks on the side without needing to focus on any visual stimulus through moving balls. Data were recorded in two phases: when the LED was on and when the LED was off. The recorded data were processed using a Butterworth filter and the power spectral density (PSD) method. In the first classification phase, which was performed for the system to detect the LED in the background, the highest accuracy rate of 99.57% was achieved with the random forest (RF) classification algorithm. In the second classification phase, which involves classifying moving objects within the proposed approach, the highest accuracy rate of 97.89% and an information transfer rate (ITR) value of 36.75 (bits/min) were achieved using the RF classifier. Full article

Glycerin-based fluids are proposed as a promising alternative to inhibited fluids in the drilling of highly-reactive formations. However, even with the use of these fluids, it is still possible to observe the occurrence of problems related to the balling of drill bits and drill pipes, such as the agglomeration and accretion of cuttings. This study aims to analyze how the interaction between expandable minerals from reactive formations and glycerin-based drilling fluids affects the stability of oil wells, focusing on the occurrence and extent of the accretion phenomenon. For this purpose, bentonite pellets were characterized regarding their mineralogical composition and plastic behavior. In addition, accretion tests were performed in order to evaluate the interaction between bentonite pellets and glycerin-based drilling fluids containing different types of inhibitors. The results revealed that the pellets were predominantly composed of interstratified illite–smectite (IS) clay minerals and presented highly plastic properties with a high degree of expansion. Furthermore, it was found that the accretion percentages were significant for all the fluids studied, at higher than 58%. Therefore, it was found that using glycerin in drilling fluids did not stabilize expandable minerals in reactive formations, even with different expansion inhibitors, which were ineffective in reducing the rock expansibility. Full article

Down-the-hole (DTH) hammer drilling has high rock-breaking efficiency and a decisive advantage in hard rock drilling, which can reduce the cost of geothermal drilling. However, when the drill bit rotation speed and the DTH percussion frequency do not match properly, especially when the drill bit diameter is large and the ball button diameter is small, while drilling a high-strength formation, the edge buttons of the drill bit are prone to fracture and break, leading to the failure of the drill bit and a significant reduction in its lifespan. This paper investigates the failure modes firstly, then analyzes the failure mechanism of the large-diameter DTH bit, and finally proposes a novel method of cluster edge buttons of the DTH hammer drill bit in a large-diameter geothermal well with high-strength rock. The drill bit has been tested in a high-compressive-strength formation, and we will continue to do more testing and research in various geological conditions. Field application shows that this technology significantly improves the bit life and drilling efficiency and reduces the drilling costs. Full article

Growing global energy demand and limited reserves of traditional energy resources are causing a growing energy shortage. In order to meet future energy needs, new energy resources must be continuously explored. Deepwater drilling research has emerged as one of the key ways to address this issue, and well structure slimming is an effective way to increase drilling speed and reduce costs. The hole size of the second section of deepwater wells decreases from a conventional 660.4 mm to 444.5 mm and increases from 500–800 m to 800–1200 m, creating problems where the conventional 660.4 mm cone bit cannot be used, the rate of penetration (ROP) of the cone bit is low, and the service life is short. To solve these problems, a 444.5 mm artificial polycrystalline diamond compact (PDC) was designed for the first time for use at home or abroad, and according to the characteristics and operation requirements of the 914.4 mm conductor jetting process, a unique anti-collision gauge protector was designed, an innovative bypass nozzle was configured, and a hydraulic design to prevent bit balling in shallow soft mudstone was formulated. PDC jetting bit-drilling technology based on well structure slimming was successfully applied to eight deepwater wells in the eastern South China Sea, which successfully jetted a 914 mm conductor and greatly improved the ROP of their second-section holes. When the below-mudline depth of the second-section hole increased by 37.01%, the average ROP increased by 227.84%. These technical achievements have successfully realized deep drilling with seawater, increased speed and efficiency, achieved good application results, and accumulated valuable experiences that can be used for reducing the cost and increasing the efficiency of offshore drilling operations. Full article

Fruit is often bruised during picking, transportation, and packaging, which is an important post-harvest issue especially when dealing with fresh fruit. This paper is aimed at the early, automatic, and non-destructive ternary (three-class) detection and classification of bruises in kiwifruit based on local spatio-spectral near-infrared (NIR) hyperspectral (HSI) imaging. For this purpose, kiwifruit samples were hand-picked under two ripening stages, either one week (7 days) before optimal ripening (unripe) or at the optimal ripening time instant (ripe). A total of 408 kiwi fruit, i.e., 204 kiwifruits for the ripe stage and 204 kiwifruit for the unripe stage, were harvested. For each stage, three classes were considered (68 samples per class). First, 136 HSI images of all undamaged (healthy) fruit samples, under the two different ripening categories (either unripe or ripe) were acquired. Next, bruising was artificially induced on the 272 fruits under the impact of a metal ball to generate the corresponding bruised fruit HSI image samples. Then, the HSI images of all bruised fruit samples were captured either 8 (Bruised-1) or 16 h (Bruised-2) after the damage was produced, generating a grand total of 408 HSI kiwifruit imaging samples. Automatic 3D-convolutional neural network (3D-CNN) and 2D-CNN classifiers based on PreActResNet and GoogLeNet models were used to analyze the HSI input data. The results showed that the detection of bruising conditions in the case of the unripe fruit is a bit easier than that for its ripe counterpart. The correct classification rate (CCR) of 3D-CNN-PreActResNet and 3D-CNN-GoogLeNet for unripe fruit was 98% and 96%, respectively, over the test set. At the same time, the CCRs of 3D-CNN-PreActResNet and 3D-CNN-GoogLeNet for ripe fruit were both 86%, computed over the test set. On the other hand, the CCRs of 2D-CNN-PreActResNet and 2D-CNN-GoogLeNet for unripe fruit were 96 and 95%, while for ripe fruit, the CCRs were 91% and 98%, respectively, computed over the test set, implying that early detection of the bruising area on HSI imaging was consistently more accurate in the unripe fruit case as compared to its ripe counterpart, with an exception made for the 2D-CNN GoogLeNet classifier which showed opposite behavior. Full article

One of the foremost causes of wellbore instability during drilling operations is shale swelling and hydration induced by the interaction of clay with water-based mud (WBM). Recently, the use of surfactants has received great interest for preventing shale swelling, bit-balling problems, and providing lubricity. Herein, a novel synthesized magnetic surfactant was investigated for its performance as a shale swelling inhibitor in drilling mud. The conventional WBM and magnetic surfactant mixed WBM (MS–WBM) were formulated and characterized using Fourier Transform Infrared (FTIR) and Thermogravimetric analyzer (TGA). Subsequently, the performance of 0.4 wt% magnetic surfactant as shale swelling and clay hydration inhibitor in drilling mud was investigated by conducting linear swelling and capillary suction timer (CST) tests. Afterward, the rheological and filtration properties of the MS–WBM were measured and compared to conventional WBM. Lastly, the swelling mechanism was investigated by conducting a scanning electron microscope (SEM), zeta potential measurement, and particle size distribution analysis of bentonite-based drilling mud. Experimental results revealed that the addition of 0.4 wt% magnetic surfactant to WBM caused a significant reduction (~30%) in linear swelling. SEM analysis, contact angle measurements, and XRD analysis confirmed that the presence of magnetic surfactant provides long-term swelling inhibition via hydrophobic interaction with the bentonite particles and intercalation into bentonite clay layers. Furthermore, the inhibition effect showed an increase in fluid loss and a decrease in rheological parameters of bentonite mixed mud. Overall, the use of magnetic surfactant exhibits sterling clay swelling inhibition potential and is hereby proffered for use as a drilling fluid additive. Full article

The friction calibration curve (FCC) is normally constructed to indirectly approximate the friction value for any simulative friction test based on sensitive friction indicators (i.e., forming load or final geometry) by finite element modeling (FEM). For calculation, these indicators are highly dependent on flow stress data and the techniques to extrapolate them. A universal FCC is preferable with the independence of these factors. In this paper, the sensitivity of the material data and our proposed extrapolation techniques for the ball ironing test (BIT) were studied to construct a new universal FCC. A specific load was proposed as a new friction indicator for this universal FCC. It was used to approximate the friction value for different materials and lubricants. This friction value was also validated to determine the maximum load and geometry for pulley forming. The results obtained from the simulation were in good agreement with the experiment. Full article

This paper measures bit error rate degradation in DDR4 due to crack in fine pitch ball grid array (FBGA) package solder ball. Thermal coefficient mismatch between the package and printed circuit board material causes cracks to occur in solder balls. These cracks change the electrical model of the solder ball and introduce parallel capacitance in the electrical model. The capacitance causes higher frequency attenuation and closes the data eye. As the data rate of the DDR4 increases there are more data eye closures. The data eye closure causes bit error rate (BER) degradation as the timing margin and voltage margin decreases. This degradation reduces the reliability of the system and causes more intermittent errors. DDR4 data line is loaded with a parallel capacitive element to mimic a crack in solder ball. The measured data eye shows a decrease in eye width. Bathtub plots are created for comparison of cracked solder ball and intact solder ball. The bathtub plots show the BER degradation due to crack in solder ball. Full article

Sn-0.7Cu-0.075Al solder alloy adding with Ce and La had been successfully prepared by applying ball-milling and vacuum arc remelting. The influence of Ce and La on microstructure and corrosion behavior of Sn-0.7Cu-0.075Al solder alloy was investigated. The results showed that Ce (La)-containing solders had refined grains and obvious directional tendency due to the dispersive refiner (CeO₂ and La₂O₃). Electrochemical potentiodynamic curves revealed three different stages of the reaction, including anodic and cathodic processes, prepassivation section, and stable passivation stages. The self-corrosion potential (E_corr) of alloys with Ce and La addition were a little bit more negative, hardly making a difference on corrosion occurrence. However, the corrosion current density (I_corr) and passivation current density (I_p) decreased by two-thirds and one-half respectively, which indicated a better corrosion resistant after adding rare earths. The recorded micrographs of corroded surface at different polarized points witnessed the formation of corrosion product film both on prepassivation and passivation stage. Moreover, the cross section of corrosion product film showed the coarse, loose film in Sn-0.7Cu-0.075Al solder and adherent, compact film in Ce (La)-containing solders, which further indicated an excellent anti-corrosion property. Full article