Experimental Study On Hydraulic Characteristics Of Polar Ice Hole Drilling When Lifting And Lowering Drills

With the rapid development of the national economy and the accelerated pace ofeconomic globalization, the demand for resources is increasing. Meanwhile, problemssuch as resources crisis, environmental pollution and climate change were alsobrought. In order to investigate and solve the sustainable development issues that thehuman being faces, many countries in the world pay more and more attention to thePolar scientific research. Polar ice is the largest freshwater storage in the world, andfurthermore, there are rich mineral and hydrocarbon resources beneath the ice sheet.In Antarctica, there are more than200kinds of mineral resources with considerablereserves, such as petroleum, coal, iron and so on. And just in the west Antarctica, thepetroleum reserve is about2to3times of the world’s annual petroleum production. Inaddition, research on the Polar ice sheet has an important significance to the study ofglobal climate and other scientific researches. Both of the exploration anddevelopment of the polar resources and the study of global climate variation cannot besuccessfully made without the ice core drilling. During the "12th Five-Year" period,China plans to drill a depth of more than3000m borehole and obtain the oldestAntarctica ice core which is more than100million years old in Dome A, the highestplace of the Antarctica ice sheet. In addition, the next task is to drill through the icesheet and pierce into the boundary of ice sheet-bedrock in Gamburtsev Mountains.The study of this paper can ensure the safety and achievement of the polar scientificdrilling project.It is important to get the subglacial bedrock core in order to research theformation and evolution of crust in Antarctica, the collision and extrusion process ofcontinent in history, the impact of internal deformation in Antarctica on the basis ofthe theory of plate tectonics and the ancient climate change on Earth. According to thefour practice attempts to get subglacial bedrock drilling core, armored cableelectromechanical coring drill has potential advantages. But how to improve drillingefficiency under the premise of ensuring safety remains to be studied.The lifting and dropping process of armored cable electromechanical coring drillis an important part of ice core drilling. The movement features and controls has animportant impact on improving drilling efficiency, reducing the occurrence ofaccidents in the hole. On the basis of comprehensive analysis of domestic and foreignresearch, we take hydraulics features in the hole as an entry point. In order to knowthe impact of drilling structures, drilling quality and rheological properties of drilling fluids to the speed of lifting and dropping pipes in theory, we research the movementprocess and the retention layer on the surface of the pipes. The research shows that themagnitude of acceleration when dropping pipes has nothing to do with the length ofthe pipes. The thickness of retention layer showed a cubic equation relationship withthe annular clearance. The percentage of retention layer thickness and annularclearance is linearly growth when the annular clearance increases. The averagevelocity of dropping pipes grows in curve when annular clearance grows. The surgepressure and annular clearance showed a linear relationship in growth.On the basis of theoretical calculations, we developed a method and a testplatform for testing the dropping speed of armored cable electromechanical coringdrill pipes in simulations. We tested the impact of pipes weight and annular clearanceto the dropping speed through testing the dropping speed of three different diametersand weight pipes. We got the following conclusions that the annular clearance hasgreat influence on the dropping speed. When the diameter of pipes is fixed, the fallingspeed showed a linear relationship with the weight of the pipes. When the otherfactors are fixed, the falling speed is0.239m/s,0.331m/s,0.457m/s when the annularclearance is3.5,4.5,5.5mm respectively.The ice drilling in Antarctica has problems such as the duration shortage, icesheet creep leading to accidents in hole, the harsh polar environment and other issues.This study can be used to guide drilling process of lifting and dropping pipes. It isused to reduce pressure in the hole, ensure the wall of the hole to be stable, safe andsmooth drilling process. The research result shows important theoretical and practicalsignificance for improving the efficiency of the Antarctic ice drilling, reducingauxiliary work time and guiding the actual work. And the research laid an importanttheoretical foundation of the polar ice drilling project.