Simulation and Experimental Study on Cuttings-Carrying for Reverse Circulation Horizontal Directional Drilling with Dual Drill Pipes

In the past decades, horizontal directional drilling (HDD) has been successfully used to install various pipelines in different strata. However, construction accidents such as drill-burying and drill-sticking occur occasionally when pipelines installed by HDD method in an unstable stratum such as sand cobble stratum. Recently, HDD with dual drill pipes was used to install pipelines in unstable stratum, and the effect is significant. The law of cuttings migration for HDD with dual drill pipes is still unclear. Therefore, it is necessary to study the law of cuttings migration in reverse circulation with dual drill pipes. This study performs numerical simulations and experimental research on the cuttings-carrying process in reverse circulation directional drilling with dual drill pipes. Based on the assumption of dual concentric pipes, simulations of fluid-solid two-phase flows are conducted in different flow channels between the inner and outer drill pipes. An experimental cuttings-carrying model is then established. By combining the results of the numerical simulations and experimental investigation, the hydraulic parameters of the dual drill pipe system are optimized, and the rationalities of the drill tool design and the grading selection are validated. The results of this study provide a reference cuttings-carrying model during reverse circulation HDD with dual drill pipes. Document type: Articl

Uneven wear behavior of downhole tool clearance material under slurry erosion

Slurry erosion of clearance fits is one of the primary reasons for the decline in the performance of downhole tools. In this study, slurry erosion experiments and computational fluid dynamics simulations were performed to understand the effect of particle impact velocity as well as the erosion mechanisms on the surface of 38CrMoAlA steel. The results indicated that uneven erosive wear occurred along the flow direction on the surface of clearance material. The uneven erosive wear can be attributed to the variation of particle impact angle affected by fluid streamlines. The site and the area of the most severe erosion changed arising from the particle impact velocity. The failure of the clearance material was mainly due to the aggravation of localized erosion wear. To extend the service life of downhole tools, the region downstream of the clearance inlet (10 mm from the inlet) should be prioritized

Design Optimization for the Thin-Walled Joint Thread of a Coring Tool Used for Deep Boreholes

Threaded joints are key components of core drilling tools. Currently, core drilling tools generally adopt the thread structure designed by the API Spec 7-1 standard. However, fractures easily occur in this thread structure due to high stress concentrations, resulting in downhole accidents. In this paper, according to the needs of large-diameter core drilling, a core barrel joint was designed with an outer diameter of Φ135 mm and a trapezoidal thread profile. Subsequently, a three-dimensional simulation model of the joint was established. The influence of the external load, connection state and thread structure on the stress distribution in the joint was analyzed through simulations, from which the optimal thread structure was determined. Finally, a connection test was carried out on the threaded joint. The stress distribution in the joint thread was indirectly studied by analyzing gas leaks (i.e., the sealing effect) under axial tension. According to the test data and the simulation results, the final joint thread structure was optimized, which lays a good foundation for the design of a core barrel

Wear Behaviors of AISI 4145H Drilling Tool Steel under Drilling Fluid Environment Conditions

4145H steel is a commonly used material for downhole tools. However, up to now the wear behavior of 4145H drilling tool steel under real drilling fluid environment conditions is still not clear. In this work, this was investigated using a modified ASTM B611 rubber ring wet grinding test system, in which six kinds of abrasives (talc, dolomite or fluorite, as well as their mixed abrasive with quartz) with metal hardness-to-abrasive hardness ratios (H/HA) ranging from 0.25 to 6.25 were used in the drilling fluid for experiments. The results show that the H/HA value determined the wear mechanism of 4145H steel. When a single soft abrasive was used (with H/HA higher than 1.3–1.5), polishing was the dominantly observed mechanism. While mixed abrasives were applied, a microcutting mechanism due to the ploughing of hard abrasive particles on the steel surface was also observed. The increase in mass fraction of the soft abrasives has little effect on the wear rate of 4145H steel, but its wear rate will significantly increase as the mass fraction of hard abrasives increases. Therefore, in order to extend the life of drilling tools and reduce downhole accidents, the mass fraction of hard particles in the drilling fluid should be reduced as much as possible

Medium-Sized Lake Water Quality Parameters Retrieval Using Multispectral UAV Image and Machine Learning Algorithms: A Case Study of the Yuandang Lake, China

Water quality monitoring of medium-sized inland water is important for water environment protection given the large number of small-to-medium size water bodies in China. A case study was conducted on Yuandang Lake in the Yangtze Delta region, with a surface area of 13 km2. This study proposed utilising a multispectral uncrewed aerial vehicle (UAV) to collect large-scale data and retrieve multiple water quality parameters using machine learning algorithms. An alternate processing method is proposed to process large and repetitive lake surface images for mapping the water quality data to the image. Machine learning regression methods (Random Forest, Gradient Boosting, Backpropagation Neural Network, and Convolutional Neural Network) were used to construct separate water quality inversion models for ten water parameters. The results showed that several water quality parameters (CODMn, temperature, pH, DO, and NC) can be retrieved with reasonable accuracy (R2 = 0.77, 0.75, 0.73, 0.67, and 0.64, respectively), although others (NH3-N, BGA, TP, Turbidity, and Chl-a) have a determination coefficient (R2) less than 0.6. This work demonstrated the tremendous potential of employing multispectral data in conjunction with machine learning algorithms to retrieve multiple water quality parameters for monitoring medium-sized bodies of water

Identification and Characterization of miR164-NAC Regulatory Modules in Banana

【Objective】This study aims to understand the roles of MIR164, NAC gene families and miR164-NAC regulatory modules in banana ripening and response to low temperature stress, so as to provide a theoretical basis for banana variety improvement and molecular breeding.【Method】'Brazil banana' was used as test material. Through high-throughput sequencing and bioinformatics analysis using miRBase, NCBI database and Clustal, TBtools, MCScanX and iTOL softwares, miR164 and NAC family members in banana were characterized, including their chromosomal location, structure, physical/ chemical properties, phylogenetic relationships, etc. Multiple miR164-NAC regulatory modules in bananas were identified through degradome sequencing and experimental validation combining transcriptome data. Next, the expression patterns of miR164-NAC regulatory modules during ripening and under cold stress were analyzed by small RNA northern blot and qRT-PCR.【Result】A total of six miR164 family members were identified in banana, of which four were located within the coding genes and two in the intergenic region. Phylogenetic analysis showed that several banana MIR164 precursors with high abundance were clustered together with papaya, suggesting that the origin of banana MIR164 gene family was closer to dicotyledonous plants. The banana genome encodes a total of 222 NAC members, unevenly distributed across all 11 chromosomes. A total of 134 homologous gene pairs were identified in these banana NACs, including 4 tandem repeats and 130 segment-replicating repeats, indicating that the main driving force of banana NAC genes evolution came from segmentreplicating events. Comparative phylogenetic analysis of all NAC proteins in banana, Arabidopsis thaliana and Oryza sativa divided this family into 23 subgroups, and transcriptome data revealed extensive redundancy and expression specificity of banana NAC genes. Physicochemical analysis showed that almost all banana NAC proteins were hydrophilic, and less than 15% were stable proteins. The miR164-NAC176/165 regulatory module in banana was verified, and the accumulation of miR164 in banana was induced by ethylene and gradually increased with fruit ripening, while the expression of MaNAC176/165 negatively regulated by miR164 in this module was gradually decreased during fruit ripening. Under the cold stress, miR164 was also obviously induced, resulting in the downregulation of its targets MaNAC176 and MaNAC165.【Conclusion】This study suggested that MaNAC176 and MaNAC165 may be transcriptional repressors of banana fruit ripening, while miR164 promotes ripening by negatively regulating MANAC176/165. This module may also be a key regulatory pathway of banana chilling injury. This study identified key miR164-NAC candidate modules in banana fruit ripening and cold stress response, which laid a foundation for subsequent gene cloning and functional analysis

Plant Prenylflavonoids and Prenyltransferases Related to their Biosynthesis

As the most widely distributed phenolic compounds in the plant kingdom, flavonoids play an integral role in plant reproduction and defense. Also, they represent many important quality traits of edible plants like color and antioxidants, and have a variety of biological activities beneficial to human health. To diversify the functions of synthesized flavonoids, plants have evolved various enzymes to perform structural modifications on different flavonoid backbones. One of these modifications is prenylation, which refers to the attachment of an isoprenoid moiety, most commonly a prenyl (C5) group. Numerous structure-activity analyses of prenylflavonoids have shown that isopentenyl substitutions at specific sites can significantly expand and enhance their chemical properties, bioactivities and potential health benefits. This review summarizes prenylflavonoids reported so far in all plant species and highlights the current knowledge on naturally occurring prenyltransferases from different biological sources that can act on plant flavonoids to synthesize prenylflavonoids. Most of them have strict flavonoid substrate- and regio-specificities, and they provide a valuable gene repository to facilitate the efficient scale-up production of flavonoids with specific prenylation patterns in cell factories. To truly achieve this goal, it is necessary to explore more diversified natural prenyltransferases, and to optimize the bioreactors system such as pathway regulation and modular co-culture engineering in the future.</p