In ultra-deep well operations,severe lateral vibration of drill string is a major factorin tool failure and decreased drilling efficiency.To investigate the vibration mechanisms and identify effective mitigation appro...In ultra-deep well operations,severe lateral vibration of drill string is a major factorin tool failure and decreased drilling efficiency.To investigate the vibration mechanisms and identify effective mitigation approaches,a dynamic model for lateral vibration in ultra-deep well drill strings was established using Cosserat geometrically exact beam theory.The model systematically examined the effects of rotational speed,WoB,andstabilizer position andsize on the vibration behavior.Key findings were validated against downhole measurement data from ultra-deep wells.Additionally,two control strategies leveraging modal competition and transverse wave disturbance were proposed.Results indicate that the bottom hole assembly(BHA)is particularly prone tointense lateral vibrations,with its vibrational modes governed by rotational speedand WOB.When the WOB isbelow the critical bucklingload,increasing either the rotational speed or WOBpromotes backward whirling of the BHA,thereby intensifying the vibration severity and bending stress.Conversely,when theWOB exceeds the critical buckling load,the system transitions into a buckling-whirling competition mode,resulting in a significant reduction in the vibration intensityand bending stress.This trend was reasonably verified through field data.Artificially inducingthis low-risk modal competition by adjusting theWOB and rotational speed can effectively reduce the probabilityof drill stringfailure.The motion of stabilizers shifts from forward whirling to backward whirling as the diameter decreases,which considerably alters the vibration-propagation patterns.The vibration-damping effects of both full-gauge and under-gauge stabilizers initially increase and then decrease as their installation position moves upward.Undergauge stabilizers exhibit less consistent behavior under non-severe vibration conditions;nevertheless,they can suppress severe whirling by interfering with adjacent drill string vibrations through lowfrequency transverse waves.They also demonstrate lower sensitivity to the installation position and enhance drill string safety through stress dispersion.Considering comprehensive vibration suppression,drill string integrity,and engineering applicability,installing under-gauge stabilizers can be a viable BHA optimization measure with significant practical value.This study provides a theoretical basis for vibration control in ultra-deep well drill strings,and the proposedstrategy offers valuable insights for improvingdrilling efficiency and ensuring operational safety.展开更多
We investigate the dynamics of a two-level quantum system driven by a laser pulse characterized by Lorentzian frequency and sub-Lorentzian amplitude modulations.Complete analytical solutions,expressed via confluent He...We investigate the dynamics of a two-level quantum system driven by a laser pulse characterized by Lorentzian frequency and sub-Lorentzian amplitude modulations.Complete analytical solutions,expressed via confluent Heun functions,are derived.Our analysis reveals that explicit exact analytical solutions exist under infinite sets of specific parameter conditions.The effects of modulation parameters and initial conditions on the final transition probabilities are examined analytically and numerically.Furthermore,the method is demonstrated to be directly applicable to two closely related models with Lorentzian pulses.展开更多
For uncertain strict-feedback systems under the prescribed performance control(PPC)problem,an innovative adaptive prescribed-time tracking control method is proposed.This method combines a novel error transformation f...For uncertain strict-feedback systems under the prescribed performance control(PPC)problem,an innovative adaptive prescribed-time tracking control method is proposed.This method combines a novel error transformation function with the prescribed-time stability theory,thereby achieving exact tracking of desired trajectories within a prescribed time while ensuring that the tracking error stays within predefined boundaries globally.By integrating a newly-designed Lyapunov-like energy function with dynamic surface control,it resolves the error surface issues that result in the semi-global boundedness of tracking error in traditional approaches.Furthermore,through a generalized Filippov solution definition,this approach overcomes the issue of non-existence of the system solution,which arises during the prescribed-time stability analysis due to the discontinuous control input.Simulation results validate the effectiveness of the proposed method.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52404014)Petro China Tarim Oilfield Companyresearch project(Grant No.671023115016)Natural Science Foundation of Shandong(Grant No.ZR2025QC495).
摘要In ultra-deep well operations,severe lateral vibration of drill string is a major factorin tool failure and decreased drilling efficiency.To investigate the vibration mechanisms and identify effective mitigation approaches,a dynamic model for lateral vibration in ultra-deep well drill strings was established using Cosserat geometrically exact beam theory.The model systematically examined the effects of rotational speed,WoB,andstabilizer position andsize on the vibration behavior.Key findings were validated against downhole measurement data from ultra-deep wells.Additionally,two control strategies leveraging modal competition and transverse wave disturbance were proposed.Results indicate that the bottom hole assembly(BHA)is particularly prone tointense lateral vibrations,with its vibrational modes governed by rotational speedand WOB.When the WOB isbelow the critical bucklingload,increasing either the rotational speed or WOBpromotes backward whirling of the BHA,thereby intensifying the vibration severity and bending stress.Conversely,when theWOB exceeds the critical buckling load,the system transitions into a buckling-whirling competition mode,resulting in a significant reduction in the vibration intensityand bending stress.This trend was reasonably verified through field data.Artificially inducingthis low-risk modal competition by adjusting theWOB and rotational speed can effectively reduce the probabilityof drill stringfailure.The motion of stabilizers shifts from forward whirling to backward whirling as the diameter decreases,which considerably alters the vibration-propagation patterns.The vibration-damping effects of both full-gauge and under-gauge stabilizers initially increase and then decrease as their installation position moves upward.Undergauge stabilizers exhibit less consistent behavior under non-severe vibration conditions;nevertheless,they can suppress severe whirling by interfering with adjacent drill string vibrations through lowfrequency transverse waves.They also demonstrate lower sensitivity to the installation position and enhance drill string safety through stress dispersion.Considering comprehensive vibration suppression,drill string integrity,and engineering applicability,installing under-gauge stabilizers can be a viable BHA optimization measure with significant practical value.This study provides a theoretical basis for vibration control in ultra-deep well drill strings,and the proposedstrategy offers valuable insights for improvingdrilling efficiency and ensuring operational safety.
基金supported by the National Natural Science Foundation of China under Grant No.11965011。
摘要We investigate the dynamics of a two-level quantum system driven by a laser pulse characterized by Lorentzian frequency and sub-Lorentzian amplitude modulations.Complete analytical solutions,expressed via confluent Heun functions,are derived.Our analysis reveals that explicit exact analytical solutions exist under infinite sets of specific parameter conditions.The effects of modulation parameters and initial conditions on the final transition probabilities are examined analytically and numerically.Furthermore,the method is demonstrated to be directly applicable to two closely related models with Lorentzian pulses.
基金supported by the National Natural Science Foundation of China(62503335,92267101,62573301)。
摘要For uncertain strict-feedback systems under the prescribed performance control(PPC)problem,an innovative adaptive prescribed-time tracking control method is proposed.This method combines a novel error transformation function with the prescribed-time stability theory,thereby achieving exact tracking of desired trajectories within a prescribed time while ensuring that the tracking error stays within predefined boundaries globally.By integrating a newly-designed Lyapunov-like energy function with dynamic surface control,it resolves the error surface issues that result in the semi-global boundedness of tracking error in traditional approaches.Furthermore,through a generalized Filippov solution definition,this approach overcomes the issue of non-existence of the system solution,which arises during the prescribed-time stability analysis due to the discontinuous control input.Simulation results validate the effectiveness of the proposed method.