To maintain gas hydrate stability, low-temperature drilling fluids and high drilling speeds should be used while drilling in gas hydrate-bearing sediments. The effect of the drilling fluid on downhole rock surfaces at...To maintain gas hydrate stability, low-temperature drilling fluids and high drilling speeds should be used while drilling in gas hydrate-bearing sediments. The effect of the drilling fluid on downhole rock surfaces at low temperatures is very important to increase the drilling rate. This paper analyzed the action mechanism of the drilling fluid on downhole rock surfaces and established a corresponding evaluation method. The softening effect of six simulated drilling fluids with 0.1 wt.% of four common surfactants and two common organic salts on the downhole rock surface strength was evaluated experimentally using the established method at low temperature. The experimental results showed that the surfactants and organic salts used in the drilling fluids aided in the reduction of the strength of the downhole rock surface, and the established evaluation method was able to quantitatively reveal the difference in the softening effect of the different drilling fluids through comparison with water. In particular, the most common surfactant that is used in drilling fluids, sodium dodecyl sulfate（SDS）, had a very good softening effect while drilling under low-temperature conditions, which can be widely applied during drilling in low-temperature formations, such as natural gas hydrate-bearing sediments, the deep seafloor and permafrost.展开更多
基金supported by the National Natural Science Foundation of China(11974182,12374257)the Fundamental Research Funds for the Central Universities(NC2022008)+1 种基金the Funding for Outstanding Doctoral Dissertation of Nanjing University of Aeronautics and Astronautics(NUAA)(BCXJ22-14)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX22_0326)。
文摘高灵敏度的自驱动紫外探测器在许多应用中都大有可为.本研究提出了一种一维ZnO基同结光电探测器,它包括表面覆盖着Ag纳米线的锑掺杂ZnO微米线(AgNWs@ZnO:Sb MW)、MgO缓冲纳米层和ZnO薄膜.该探测器在0 V偏压下对紫外光非常敏感,其性能参数包括约7个量级的开关比、292.2 mA W^(-1)的响应度、6.9×10^(13)Jones的比探测率,以及微秒量级的快速响应速度(上升时间16.4μs,下降时间465.1μs).特别是10μW cm^(-2)的微弱紫外光时接近99.3%的外量子效率.此外,本文系统研究了MgO纳米薄膜和表面修饰AgNWs对探测器件性能增强的机理.作为自驱动光接收器,该光电二极管被进一步集成到能够实时传输信息的紫外通信系统中.此外,基于AgNWs@p-ZnO:Sb MW/i-MgO/n-ZnO的同质结9×9阵列显示出均匀的光响应分布,可用作具有良好空间分辨率的成像传感器.这项研究有望为设计高性能紫外光检测器提供一条具有低功耗和可大规模建造的途径.
基金supported by the National Natural Science Foundation of China(Nos.41502346,51274177)the Fundamental Research Funds for the Central Universities(No.CUGL140819)+2 种基金the Open Research Fund Program of Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring(Central South University)Ministry of Education(Nos.2016YSJS005,2016YSJS011)the Open Research Fund Program of Key Lab of Drilling and Exploitation Technology in Complex Conditions(Jilin University)(No.DET201610)
文摘To maintain gas hydrate stability, low-temperature drilling fluids and high drilling speeds should be used while drilling in gas hydrate-bearing sediments. The effect of the drilling fluid on downhole rock surfaces at low temperatures is very important to increase the drilling rate. This paper analyzed the action mechanism of the drilling fluid on downhole rock surfaces and established a corresponding evaluation method. The softening effect of six simulated drilling fluids with 0.1 wt.% of four common surfactants and two common organic salts on the downhole rock surface strength was evaluated experimentally using the established method at low temperature. The experimental results showed that the surfactants and organic salts used in the drilling fluids aided in the reduction of the strength of the downhole rock surface, and the established evaluation method was able to quantitatively reveal the difference in the softening effect of the different drilling fluids through comparison with water. In particular, the most common surfactant that is used in drilling fluids, sodium dodecyl sulfate（SDS）, had a very good softening effect while drilling under low-temperature conditions, which can be widely applied during drilling in low-temperature formations, such as natural gas hydrate-bearing sediments, the deep seafloor and permafrost.
