| With the rapid progress of human society and the rapid development of the global economy, the concomitant energy consumption is increasing, resource requirements gradually increased, which causes all kinds of problems have become increasingly prominent, such as:environmental pollution, global warming, resource scarcity, etc.. In order to investigate and address these challenges, the world is gradually increased emphasis on polar science. Polar has a very rich resources of storage, in addition to being the world’s largest freshwater storage sites, particularly in the Antarctic ice under its reserves may have very substantial reserves of oil and gas and mineral resources. Also, the conduct of polar science are of great significance to understanding the global environment and climate change, the evolution of continental plates as well as other subjects of study. During the polar scientific investigation process, to get the old Bing ice samples and rock samples under ice shale is one of the important ways of scientific research. Therefore, ice core drilling method has become widely used around the world in the Antarctic.Beginning in 2010, our country implemented the drilling for deep ice core and bedrock under ice in the Antarctic GanBurtsev Mountains. Ice depth is expected 1000m, and it is needed to get core bedrock around 10m. But also it is carried out at Dome A to drill at more than 3000m deep ice, so as to get the oldest sample. In implementing this program, in addition to the polar drilling equipment to carry out in-depth research, as drilling to obtain samples of bedrock under the ice is essential, it is core technologies to carry out drilling under ice-rock. Due to the special geographical environment of the Antarctic, we can not use conventional drilling methods. Based on past drilling experience of Russia and the United States, armored cable electric-mechanical coring drill is an important one of the coring tool which has its unique technical advantages. But research on how to safely and effectively improve the efficiency of the drill coring is little, we need further research to resolve.Drill lifting process in the hole is an important part of the armored cable electric mechanical coring drill when drilling. Due to extremely harsh environment, complex case under ice, and the actual drilling time is short and other special problem, we need as much as possible to improve the drilling efficiency. The purpose of this study is to guide reasonable rate of lifting the drill, in order to reduce the hole pressure changes, maintain the stability of the cell wall and protect the safe and smooth drilling. Research achievement have important theoretical and practical significance to reduce the auxiliary time when actual drilling, improve drilling efficiency and guide the actual drilling work. And lay an important theoretical basis for the success of the Antarctic ice drilling work to be completed.For a correct understanding of the characteristics of drill-down movement in the hole, in 2014, the Polar Research Center of Jilin University made experimental study on early, which starting from the borehole hydraulics angle, according to the traffic balance of the drilling fluid in the hole and the balance relationship between the pressure of drilling fluid and friction, derived the lift rate formula of drill in a hole. Then by falling speed testing for three kinds drills of same length, diameter of 123 mm,125 mm and 127 mm in the two-component drilling fluid, reached the following conclusions:(1) When the tool is completely submerged in the drilling fluid, during the process of drilling tools accelerated motion, the size of the acceleration has nothing to do with the length;(2) the retention layer thickness is mainly affected by the decentralization of the drill rate;(3)When the annular clearance increases, rate of drill down increases rapidly, the growth rate is gradually reduced;(4) With certain conditions of the length of the drill, the annular clearance, drilling fluid viscosity and density, the rate of decentralization mass increases linearly of quality of drilling tools. When annular clearance is 4.5mm, the quality of drill increases lkg, drill decentralization rate increases linearly 0.023m/s.But because we use cameras as equipment for preliminary test, test accuracy is limited by the personnel operation in the recording process, which is easy to prone to error. Additionally constrained by experimental conditions, we only tested three different lengths of the same diameter drill, so test variable is less and the data is not perfect. Therefore, this article improves test methods to improve test accuracy on the basis of preliminary experimental research, increases the test variables and tests falling speed of different lengths and quality of drill in two kinds of drilling fluid, so as to make more precise depth study of drill-down movement characteristics in the bore.Gaining control of the motion characteristics of the drill in the hole, not only can greatly increase drilling efficiency, but also can reduce the incidence of hole accidents during drilling. By analyzing the existing research results at home and abroad, starting from the perspective of drilling hydraulics to make further expand research on drill lifting process in the hole. And by theoretical analysis to identify effects on the drill movement characteristics from quality drilling viscosity, length, drilling fluid density and other factors. Theoretical analysis shows that:the speed and acceleration of drill down are subject to shear rate, the diameter of the drill, drill the equivalent density, drilling fluid viscosity and density. Drill fall faster, the acceleration time will be shorter. The rate of drill down is proportional to equivalent density, with the increase of the viscosity of the drilling fluid, speed of drill down decreases a curved. And drop rate is inversely proportional to the density of drilling fluid.Based on the theoretical analysis and on the application of drill lifting test rope which is from independent research and design and cable-pull displacement sensor, for four drill with length of 400mm,600mm,800mm and 1000mm, change the quality respectively and test its movement in two different drilling fluids. For the chosen two kinds of ultra-low temperature drilling fluid, butyl butyrate and ethyl butyrate, at a test temperature-20℃, the viscosity and density respectively are 2.8mpas,908kg/m3 and 1.8mpas,920kg/m3 and show no color transparent state. There is well fluidity at low temperature. The viscosity, density, environmental protection and low temperature performance are in line with the requirements of the polar deep ice core drilling. In testing we use displacement sensor for data acquisition. Drill falling distance unit is set to mm, and every 50 seconds, record data, that is, each 0.02s collect data to ensure accuracy and richness of the data and all the data will eventually be converted into a chart to show different trends of impact on the speed of the drill down from intuitive factors. By combining experimental test results and theoretical analysis, determine the impact of drill length, mass, density and viscosity of the drilling fluid on the rate of drill movement. Come to the following conclusions:(1) According to the theoretical derivation, the falling speed is proportional to equivalent density of drill; With a certain length of drill, the falling speed of the drill and the quality is directly proportional relationship; And with a constant quality of the drill, the falling speed of drill is inversely proportional to the length; falling speed of drill decreases with the increase of drilling fluid viscosity and the drilling fluid density; The time of drill falling acceleration mainly has something to do with the drilling fluid viscosity, density, shear rate.(2) According to the experimental test, with the increase of the quality of the drill and the shorten of the length, the time of variable accelerated motion becomes shorter, the speed which has reached a uniform one becomes faster. The time of variable accelerated motion greatly influenced by the drilling fluid viscosity. When falling speed is between 0.296m/s-0.409m/s range in butyl butyrate, its acceleration time is 0.34s-0.96s. When falling speed is between 0.335m/s-0.481m/s range in ethyl butyrate, its acceleration time is between 0.26s-0.90s.(3) According to the experimental test, the falling speed and quality of drill hole show a proportional relationship. In butyl butyrate drilling fluid, quality of the drill along with various lengths increases each 1kg, falling speed drill increases 0.015m/s. In ethyl butyrate drilling fluid, quality of the drill along with various lengths increases each 1kg, falling speed drill gets an increase of 0.020m/s.(4) The impact of the drilling fluid on drilling falling speed is much larger than the density of the drilling fluid. Falling speed of drill decreases as the viscosity increases. According to experimental data, falling speed of the same drill in ethyl butyrate drilling fluid is 1.27 times in butyl butyrate.(5) Falling speed of drill and drill are inversely proportional relationship. In butyl butyrate and ethyl butyrate, when the quality of drill is the same, falling speed of drill increase 1.107 times and 1.081 times in average, with length shorter each 200mm. |
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