Ice cores contain an abundance of information about the Earth's climate in the past,and recovered from shallow drilling down to 300--350 m give sufficient information for reconstructing of the last climatic change...Ice cores contain an abundance of information about the Earth's climate in the past,and recovered from shallow drilling down to 300--350 m give sufficient information for reconstructing of the last climatic changes and for monitoring of pollution from human being. Cable-suspended core auger drills use an armored cable with a winch to provide power to the down-hole motor system and to retrieve the down-hole unit. Because of their lightweight,convenient transportation and installation,high penetration rates and low power consumption,core auger drills are widely used for shallow drilling in ice. Nowadays at least 14 types of auger electromechanical drills were designed and tested in different foreign and national glaciological laboratories. However,auger options were usually determined by experience,and the main parameters( helix angle of the fights and rotational speed) are varied in a wide range from drill to drill. If parameters of auger are not chosen properly,poorly engineered drills had troubles with low efficiency of cuttings transportation,jam of ice cuttings,repeated fragmentation,cutters icing and stop penetration,abnormal power consumption,high rotation torques,and so on.Thus,this paper presents the method of optimization of ice cuttings transportation of cable-suspended core auger drill on the base of the theory of rotary auger. As the result,the optimal helix angle was determined corresponding to the rotational speed from the transportation efficiency point of view.展开更多
Inadequate hole cleaning is one of the main reasons for inefficient operations in extended-reach drilling.The mechanism of cuttings transport under the back reaming operation,which is frequently adopted to remove the ...Inadequate hole cleaning is one of the main reasons for inefficient operations in extended-reach drilling.The mechanism of cuttings transport under the back reaming operation,which is frequently adopted to remove the cuttings,has been investigated in this study.To this end,a coupled layering-sliding mesh method with the Eulerian-Granular approach has been established innovatively.The dynamic layering method has been employed to simulate the axial motion of the pipe,whereas the sliding mesh method has been used to simulate the pipe rotation.The back reaming operation of a connector-furnished pipe has been simulated,and the sensitive parameter analysis has been conducted.The results thus obtained demonstrate that the increase in the initial bed height,inclination,and the diameter and length of the connector causes a significant increase in the cuttings concentration.In addition,the cuttings concentration is observed to decrease significantly with the pipe rotation speed.Furthermore,two main factors contribute towards the cuttings accumulation around the connector,namely,the difference in the cross-sectional area and the pushing effect of the connector—like a“bulldozer”.The“bulldozer”effect of the connector dominates when the tripping velocity is significant compared to the velocity of the cuttings.Conversely,the effect of the difference in the cross-sectional area becomes the leading factor for cuttings accumulation.The“bulldozer”effect of the connector causes a more severe impact on hole cleaning.In both cases,increasing the tripping velocity only mildly affects the cuttings concentration.It is therefore suggested that the tripping velocity should be slower than that of the sand during the back reaming operation.Furthermore,increased fluid velocity might lead to a higher accumulated cuttings concentration around the connector when the cuttings bed has not entirely passed through the connector.A significant flow rate can be safely applied after the cuttings have passed through the connector furnished with a large diameter,such as the bottom hole assembly.This exploration serves as an essential guide to predicting and controlling tight spots while back reaming.展开更多
With a clear understanding of the drilling fluid techniques and the cutting taking mechanism, a new advanced model is set up for analyzing field data and quantitative forecast of cutting taking mechanism. Therefore,...With a clear understanding of the drilling fluid techniques and the cutting taking mechanism, a new advanced model is set up for analyzing field data and quantitative forecast of cutting taking mechanism. Therefore, a number of values affecting the drilling rate and the hole cleaning are studied over a wide range of parameters. Drilling data obtained under high borehole pressure conditions are analyzed to determine the causes of the reduction in rate of penetration (ROP) as the borehole pressure increases, which in some cases is caused by the buildup of rock debris under the bit. The theoretical achievement and testing conclusions can be very instructional for horizontal well drilling. Much higher annular velocities are required for effective hole cleaning in directional wells than in vertical wells. High viscosity muds are observed to provide better transport than low viscosity muds.展开更多
基金Supported by Project of the National Science Foundation of China(No.41327804)
文摘Ice cores contain an abundance of information about the Earth's climate in the past,and recovered from shallow drilling down to 300--350 m give sufficient information for reconstructing of the last climatic changes and for monitoring of pollution from human being. Cable-suspended core auger drills use an armored cable with a winch to provide power to the down-hole motor system and to retrieve the down-hole unit. Because of their lightweight,convenient transportation and installation,high penetration rates and low power consumption,core auger drills are widely used for shallow drilling in ice. Nowadays at least 14 types of auger electromechanical drills were designed and tested in different foreign and national glaciological laboratories. However,auger options were usually determined by experience,and the main parameters( helix angle of the fights and rotational speed) are varied in a wide range from drill to drill. If parameters of auger are not chosen properly,poorly engineered drills had troubles with low efficiency of cuttings transportation,jam of ice cuttings,repeated fragmentation,cutters icing and stop penetration,abnormal power consumption,high rotation torques,and so on.Thus,this paper presents the method of optimization of ice cuttings transportation of cable-suspended core auger drill on the base of the theory of rotary auger. As the result,the optimal helix angle was determined corresponding to the rotational speed from the transportation efficiency point of view.
基金support from the Natural Science Foundation of China(Grant Nos.52222401,52234002,51904317 and 52174012)Science Foundation of China University of Petroleum,Beijing(Grant No.ZXZX20230083)other projects(ZLZX2020-01-07-01).
文摘Inadequate hole cleaning is one of the main reasons for inefficient operations in extended-reach drilling.The mechanism of cuttings transport under the back reaming operation,which is frequently adopted to remove the cuttings,has been investigated in this study.To this end,a coupled layering-sliding mesh method with the Eulerian-Granular approach has been established innovatively.The dynamic layering method has been employed to simulate the axial motion of the pipe,whereas the sliding mesh method has been used to simulate the pipe rotation.The back reaming operation of a connector-furnished pipe has been simulated,and the sensitive parameter analysis has been conducted.The results thus obtained demonstrate that the increase in the initial bed height,inclination,and the diameter and length of the connector causes a significant increase in the cuttings concentration.In addition,the cuttings concentration is observed to decrease significantly with the pipe rotation speed.Furthermore,two main factors contribute towards the cuttings accumulation around the connector,namely,the difference in the cross-sectional area and the pushing effect of the connector—like a“bulldozer”.The“bulldozer”effect of the connector dominates when the tripping velocity is significant compared to the velocity of the cuttings.Conversely,the effect of the difference in the cross-sectional area becomes the leading factor for cuttings accumulation.The“bulldozer”effect of the connector causes a more severe impact on hole cleaning.In both cases,increasing the tripping velocity only mildly affects the cuttings concentration.It is therefore suggested that the tripping velocity should be slower than that of the sand during the back reaming operation.Furthermore,increased fluid velocity might lead to a higher accumulated cuttings concentration around the connector when the cuttings bed has not entirely passed through the connector.A significant flow rate can be safely applied after the cuttings have passed through the connector furnished with a large diameter,such as the bottom hole assembly.This exploration serves as an essential guide to predicting and controlling tight spots while back reaming.
文摘With a clear understanding of the drilling fluid techniques and the cutting taking mechanism, a new advanced model is set up for analyzing field data and quantitative forecast of cutting taking mechanism. Therefore, a number of values affecting the drilling rate and the hole cleaning are studied over a wide range of parameters. Drilling data obtained under high borehole pressure conditions are analyzed to determine the causes of the reduction in rate of penetration (ROP) as the borehole pressure increases, which in some cases is caused by the buildup of rock debris under the bit. The theoretical achievement and testing conclusions can be very instructional for horizontal well drilling. Much higher annular velocities are required for effective hole cleaning in directional wells than in vertical wells. High viscosity muds are observed to provide better transport than low viscosity muds.
