During drilling operations,cyclic loading is exerted on the wellbore wall by the vibrations of the drill string.This loading could lead to rock fatigue,which in turn might result in wellbore failure.In this study,a nu...During drilling operations,cyclic loading is exerted on the wellbore wall by the vibrations of the drill string.This loading could lead to rock fatigue,which in turn might result in wellbore failure.In this study,a numerical model is developed to simulate the effects of repeated loading on rock fatigue and failure.The simulation is based on an elasto-plastic constitutive model coupled with a damage mechanics approach,which allows us to examine the wellbore instability due to drill string vibrations.The model is verified with the existing data in the literature related to experiments on impact of a steel ball against a curved wall.The findings indicate that cyclic loading increases the development of plastic strain around the wellbore significantly compared to static conditions,promoting rock fatigue.Furthermore,the cyclic loading expands the radius of the yielded zone substantially,a critical factor for maintaining wellbore integrity.The proposed model can be used to evaluate the wellbore stability under repetitive loading caused by the drill string action.展开更多
To optimize the bit selection for large-diameter wellbore in the upper section of an ultra-deep well S-1,a full-well dynamic model integrating drill string vibration and bit rock-breaking was established and then veri...To optimize the bit selection for large-diameter wellbore in the upper section of an ultra-deep well S-1,a full-well dynamic model integrating drill string vibration and bit rock-breaking was established and then verified using measured vibration data of drilling tools and actual rate of penetration(ROP)from Well HT-1 in northern Sichuan Basin.This model was employed to calculate and analyze drill string dynamic characteristics during large-diameter wellbore drilling in the Jurassic Penglaizhen Formation of Well S-1,followed by bit optimization.Research results show that during the drilling in Penglaizhen Formation of Well S-1,considering both the ROP of six candidate bits and the lateral/axial/torsional vibration characteristics of downhole tools,the six-blade dual-row cutter bit with the fastest ROP(average 7.12 m/h)was optimally selected.When using this bit,the downhole tool vibration levels remained at medium-low values.Field data showed over 90%consistency between actual ROP data and dynamic model calculation results after bit placement,demonstrating that the model can be used for bit program screening.展开更多
The vibrating string pressure sensor is designed according to the working surroundings and conditions. this sensor is used for the weighing of the fixed-quantity bucket loader in the main shaft lifting systems of coal...The vibrating string pressure sensor is designed according to the working surroundings and conditions. this sensor is used for the weighing of the fixed-quantity bucket loader in the main shaft lifting systems of coal mines. The design of the sensor has been introduced in detail. Calibrations and errors of the sensor theoretical fornada have also been analyzed.展开更多
This paper deals with the spatial vibration of an elastic string with masses at the endpoints. The authors derive the corresponding quasilinear wave equation with dynamical boundary conditions, and prove the exact bou...This paper deals with the spatial vibration of an elastic string with masses at the endpoints. The authors derive the corresponding quasilinear wave equation with dynamical boundary conditions, and prove the exact boundary controllability of this system by means of a constructive method with modular structure.展开更多
Resonances are usually associated with finite systems—the vibrations of clamped strings in a guitar or the optical modes in a cavity defined by mirrors.In optics,resonances may be induced in infinite continuous media...Resonances are usually associated with finite systems—the vibrations of clamped strings in a guitar or the optical modes in a cavity defined by mirrors.In optics,resonances may be induced in infinite continuous media via periodic modulations of their optical properties.Here we demonstrate that periodic modulations of the permittivity of a featureless thin film can also act as a symmetry-breaking mechanism,allowing the excitation of photonic quasi-bound states in the continuum(qBICs).By interfering two ultrashort laser pulses in the unbounded film,transient resonances can be tailored through different parameters of the pump beams.We show that the system offers resonances tunable in wavelength and quality-factor,and spectrally selective enhancement of third-harmonic generation.Due to a fast decay of the permittivity asymmetry,we observe ultrafast dynamics,enabling time-selective near-field enhancement with picosecond precision.Optically induced permittivity asymmetries may be exploited in on-demand weak to ultrastrong light-matter interaction regimes and light manipulation at dynamically chosen wavelengths in lithography-free metasurfaces.展开更多
For a class of mixed initial-boundary value problem for general quasilinear hyperbolic systems, this paper establishes the local exact boundary controllability with boundary controls only acting on one end. As an appl...For a class of mixed initial-boundary value problem for general quasilinear hyperbolic systems, this paper establishes the local exact boundary controllability with boundary controls only acting on one end. As an application, the authors show the local exact boundary controllability for a kind of nonlinear vibrating string problem.展开更多
基金funded by the Research council of Norway,Equinor and Sekal with NFR(Grant No.308826).
文摘During drilling operations,cyclic loading is exerted on the wellbore wall by the vibrations of the drill string.This loading could lead to rock fatigue,which in turn might result in wellbore failure.In this study,a numerical model is developed to simulate the effects of repeated loading on rock fatigue and failure.The simulation is based on an elasto-plastic constitutive model coupled with a damage mechanics approach,which allows us to examine the wellbore instability due to drill string vibrations.The model is verified with the existing data in the literature related to experiments on impact of a steel ball against a curved wall.The findings indicate that cyclic loading increases the development of plastic strain around the wellbore significantly compared to static conditions,promoting rock fatigue.Furthermore,the cyclic loading expands the radius of the yielded zone substantially,a critical factor for maintaining wellbore integrity.The proposed model can be used to evaluate the wellbore stability under repetitive loading caused by the drill string action.
基金Supported by the National Natural Science Foundation of China(52225401)。
文摘To optimize the bit selection for large-diameter wellbore in the upper section of an ultra-deep well S-1,a full-well dynamic model integrating drill string vibration and bit rock-breaking was established and then verified using measured vibration data of drilling tools and actual rate of penetration(ROP)from Well HT-1 in northern Sichuan Basin.This model was employed to calculate and analyze drill string dynamic characteristics during large-diameter wellbore drilling in the Jurassic Penglaizhen Formation of Well S-1,followed by bit optimization.Research results show that during the drilling in Penglaizhen Formation of Well S-1,considering both the ROP of six candidate bits and the lateral/axial/torsional vibration characteristics of downhole tools,the six-blade dual-row cutter bit with the fastest ROP(average 7.12 m/h)was optimally selected.When using this bit,the downhole tool vibration levels remained at medium-low values.Field data showed over 90%consistency between actual ROP data and dynamic model calculation results after bit placement,demonstrating that the model can be used for bit program screening.
文摘The vibrating string pressure sensor is designed according to the working surroundings and conditions. this sensor is used for the weighing of the fixed-quantity bucket loader in the main shaft lifting systems of coal mines. The design of the sensor has been introduced in detail. Calibrations and errors of the sensor theoretical fornada have also been analyzed.
基金supported by the National Natural Science Foundation of China(No.11831011).
文摘This paper deals with the spatial vibration of an elastic string with masses at the endpoints. The authors derive the corresponding quasilinear wave equation with dynamical boundary conditions, and prove the exact boundary controllability of this system by means of a constructive method with modular structure.
文摘Resonances are usually associated with finite systems—the vibrations of clamped strings in a guitar or the optical modes in a cavity defined by mirrors.In optics,resonances may be induced in infinite continuous media via periodic modulations of their optical properties.Here we demonstrate that periodic modulations of the permittivity of a featureless thin film can also act as a symmetry-breaking mechanism,allowing the excitation of photonic quasi-bound states in the continuum(qBICs).By interfering two ultrashort laser pulses in the unbounded film,transient resonances can be tailored through different parameters of the pump beams.We show that the system offers resonances tunable in wavelength and quality-factor,and spectrally selective enhancement of third-harmonic generation.Due to a fast decay of the permittivity asymmetry,we observe ultrafast dynamics,enabling time-selective near-field enhancement with picosecond precision.Optically induced permittivity asymmetries may be exploited in on-demand weak to ultrastrong light-matter interaction regimes and light manipulation at dynamically chosen wavelengths in lithography-free metasurfaces.
基金Project supported by the Special Funds forMajor State Basic Research Projects ofChina.
文摘For a class of mixed initial-boundary value problem for general quasilinear hyperbolic systems, this paper establishes the local exact boundary controllability with boundary controls only acting on one end. As an application, the authors show the local exact boundary controllability for a kind of nonlinear vibrating string problem.
