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Excessive stick–slip vibration of drill strings can cause inefficiency and unsafety of drilling operations. To suppress the stick–slip vibration that occurred during the downhole drilling process, a drill string torsional vibration system considering the torsional vibration tool has been proposed on the basis of the 4-degree of freedom lumped-parameter model. In the design of the model, the tool is approximated by a simple torsional pendulum that brings impact torque to the drill bit. Furthermore, two sliding mode controllers, U1 and U2, are used to suppress stick–slip vibrations while enabling the drill bit to track the desired angular velocity. Aiming at parameter uncertainty and system instability in the drilling operations, a parameter adaptation law is added to the sliding mode controller U2. Finally, the suppression effects of stick–slip and robustness of parametric uncertainty about the two proposed controllers are demonstrated and compared by simulation and field test results. This paper provides a reference for the suppression of stick–slip vibration and the further study of the complex dynamics of the drill string.

Erosion resistance is the evaluation indicator of the performance parameter of wall-attachment jet component, which is the key component of jet oscillation tool. For the erosion wear problem, the e...

In order to improve the ROP (rate of penetration) of complex structure and deep wells and reduce the energy consumption of rock breaking during the drilling process, a core drill bit with negative ...

In the drilling process of a horizontal well, the large drilling friction between the drill string and the wellbore wall can cause the phenomenon of backing pressure and reduce drilling efficiency....

Internal motion and dynamics mechanism studies of a new composite percussion drilling tool aim at reducing stick-slip phenomenon and improving rock breaking efficiency. In this study, experiments are performed using composite percussion drilling tools to investigate its torsional and axial composite impact performance. According to the experimental results, a six degrees-of-freedom (6DOF) rigid body motion model was established to study the passive motion of a torsional hammer. The obtained results, including the tangential acceleration, were verified with experimental data, and the small pressure differences between the high and low pressure areas, which mainly determined by the inlet structure, is the main reason for the poor torsional impact effects. Based on these discoveries, the improved design increases the inlet flow to 17.2% of the total, the pressure differences to 0.05 MPa, and the instantaneous tangential acceleration to 0.198 m/s2, which results in increased tangential acceleration fluctuation amplitude by 1137.5% and greatly improved torsional impact performance. This research can provide a baseline for stick-slip reduction technology optimization.

This work presents an electromechanical finite element analysis for a proposed MEMS piezoelectric vibration energy harvester. The structure of the MEMS energy harvester consists of a basic cantilever beam with a clamped end mass and a spring net which can enhance the reliability of the device. Aluminum nitride thin film is applied as the piezoelectric function material. The proposed MEMS device is also fabricated, packaged and characterized to determine its performance. The spring net structure design is proven to increase the yield of the MEMS energy harvester chips during transportation. Three dimensional electromechanical finite element model coupled the solid mechanics physics and electrostatics physics is built to simulate the piezoelectric effect. The simulated results and the experimental measured data are in close agreement, which verified the prediction of the finite element model. The validation of the model indicate that the finite model can instruct the design of an ideal MEMS piezoelectric device in short period at a low cost.

For reducing the sticking or stick–slip phenomenon, this paper proposed a new torsional oscillator which could produce a circumferential torque vibration in the drilling process. Based on the working principle and fundamental structure, the generation mechanism of torsional vibration and the relationships of the mechanical parts are derived. Then, the dynamic model is established according to the drilling operation condition. With this, the further analysis of changing relationship between the inlet flow and torque is studied. The angular displacement and velocity of the valve body are analyzed according to the dynamics theory models. With the combination of the theoretical analysis model, the parameter studies are carried out by numerical example calculation. Finally, experiment test is conducted to identify the accuracy and reliability of the calculation method under the corresponding working conditions. The results show that with the constant pressure the average torque is proportional to the inlet flow. However, while the inlet pressure is invariable, the collision period is inversely proportional to the inlet flow, and the angular displacement and velocity are proportional to the inlet flow. The research results can provide references for the design and application of the torsional vibration tools, which is potential and significant in drilling engineering.

Gas blowout occurred during drilling may cause catastrophic environmental hazards and economic losses. It is thus one of the important tasks to accurately determine the gas blowout volume so that an effective rescue plan can be worked out in case of gas blowout. In this paper, a numerical method for estimating the gas blowout volume was presented based on the Bernoulli Equation and the corresponding software was programmed. In the process of numerical estimation, the velocity distribution of the blowout flame characterized by the axisymmetric laminar flow was investigated through an analysis of the dynamic flowing features of the gas gusher, and the relationship between the gas production of a well and the height of the blowout flame was then analyzed with the Bernoulli Equation to obtain the numerical results of the gas blowout volume. The results were then compared with those laboratory measurements, and the software was revised based on the comparisons. Some conclusions were drawn. First, when the spout shape of a gusher is constant, the gas production is proportional to the height of the blowout flame, and inversely proportional to the gas kinematic viscosity, the stoichiometric ratio factor and the oxygen concentration. Second, the errors between the results estimated using the revised software and the laboratory measurements are within the allowable range, and the software can automatically generate a report. In a word, the method and software presented in this paper can be an effective technique for preparing a sound and safe rescue plan in case of gas blowout, and is of great significance in relieving the hazards of a well with uncontrolled blowout. Keywords: Gas well, Well with uncontrolled blowout, Estimation of gas blowout volume, Gas production, Axisymmetric, Laminar flow, Gas gusher, Flame height, Software

For the nonlinear vibration of the drill string in the drilling process, vibration characteristics analysis and experimental study of the drill string are conducted, which are to analyze the drill string dynamic characteristics with wellbore random friction force on the basis of the horizontal well. Firstly, considering the wellbore random friction force, the analysis models of the drill string vibration and the drilling efficiency of the horizontal well are established. Then, the establishment method of the random wellbore friction field is also obtained. With the combination of solution expressions of each force in the vibration equation, the discrete method of the dynamic model is established. According to the experimental test, the key input parameters are determined, and then, the example analysis of the vibration model is conducted. With the comparison of the experimental test and theoretical calculation, the influences of key parameters on the dynamic characteristics of the drill string are analyzed to verify the accuracy of the analysis model. The results can provide a new insight to the researches of the drill string dynamics, especially for the complex well, such as ultra-deep well, branch well and directional well, in which the wellbore friction has a significant influence on the result of the drill string kinetics. Moreover, the results can offer an important guidance for the design and application of new downhole tools.

Drill string dynamics research is one of the important research directions in modern oil and gas drilling technology. Aiming at axial vibration, radial vibration, nonlinear vibration with the consideration of stochastic friction and the tooth wear under the action of torsional loads during the drilling process, theoretical analysis, and example calculation are carried out to obtain the parameter influence result of the drilling dynamics research.

In this paper, we proposed a novel non-solenoid structure to realize high Q on-chip inductor based on MEMS techniques. It aims to reduce the resistance loss by parallel turns while increase the inductance by the self-inductance of the inner and outer copper wire columns and the mutual inductance between the same flow directions. The inner and outer copper wire columns are spaced apart as much as possible without the reverse flow mutual inductance subtraction. Finite element method was applied to analyze the performance of the designed inductor. The novel inductor can significantly improve the Q value (peak Q= 39 @ 2.03 GHz) which nearly 180% higher than that of traditional 8-turns solenoid inductor, and nearly 450% higher than that of a planar spiral inductor at the same feature size. We also raised several solutions to solve the low inductance problem due to the parallel connection. In addition, the self-resonant frequency is greater than 15 GHz which makes our inductor adaptable to a wider spectrum of applications.

In this paper, we proposed a vertical spiral structure to realize high performance (high Q and high L) on-chip inductor based on MEMS technology. It aims to reduce the substrate loss by the approach of 3D vertical integration so that the quality factor of the on-chip inductors could be improved. In order to verify and explore the improvement of the quality factor of the vertical spiral solenoid structure, finite element method was used to analysis the performance of designed inductor, and an optimal solution was raised through modeling and simulation by commercial software HFSS. Combining the thermal oxidation process level, we tried to isolate silicon by 10um silicon dioxide isolation layer. Simulation results show that more than 10um silicon dioxide isolation layer no longer improves the inductive performance. The simulation results show that the same scalar-isolated vertical spiral inductors provide superior performance (peak Q = 32 @ 7 GHz, L=4nH). Compared with ordinary silicon planar inductors, the quality factor Q increased 30%, inductance L increased 100%. In addition, self-resonant frequency is greater than 10 GHz which makes our inductor could adapt to a wider spectrum of applications.