A while-drilling energy harvesting device is designed in this paper to recovery energy along with the longitudinal vibration of the drill pipes, aiming to serve as a continuous power supply for downhole instruments during the drilling procedure. Radial size of the energy harvesting device is determined through the drilling engineering field experience and geological survey reports. A piezoelectric coupling model based on the selected piezoelectric material was established via COMSOL Multiphysics numerical simulation. The forced vibration was analyzed to determine the piezoelectric patch length range and their best installation positions. Modal analysis and frequency response research indicate that the natural frequency of the piezoelectric cantilever beam increased monotonously with the increase of the piezoelectric patch’ thickness before reaching an inflection point. Moreover, the simulation results imply that the peak voltage of the harvested energy varied in a regional manner with the increase of the piezoelectric patches. When the thickness of the piezoelectric patches was 1.2–1.4 mm, the designed device gained the best energy harvest performance with a peak voltage of 15–40 V. Works in this paper provide theoretical support and design reference for the application of the piezoelectric material in the drilling field.

Wellbore drilling parameters optimization is one of the most important issue in drilling engineering. Rate of penetration or mechanical specific energy was usually utilized as the optimization objective. The rate of penetration directly relates to the drilling cycle, while mechanical specific energy reflects the drilling efficiency. In this paper, except for rate of penetration and mechanical specific energy, the drilling life of bit is also summarized as a comprehensive assessment indicator in wellbore drilling parameters optimization problem. The drilling life of bit is taken into consideration for the design and manufacturing cost of bit compose a significant part of the drilling cost and the bit drilling life greatly influences the drilling efficiency. However, those objectives are usually related in a highly nonlinear relationship and in conflict with each other. Thus, a multi-objective cellular particle swarm optimization (MOCPSO) is developed to solve the three-objective drilling parameters optimization problem. Moreover, the radius basis function (RBF) method is employed into the formation parameters identification for rate of penetration model. Performance of MOCPSO is investigated by taken a comparison with multi-objective PSO and non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ). Effect of the four commonly used neighborhood function is also investigated by making contrasts with each other. It can be inferred that MOCPSO is statistically superior to both multi-objective PSO, NSGA-Ⅱ at the 0.05 level of significance on the wellbore drilling parameters optimization problem. And the four commonly used neighborhood templates perform comparable with each other, and are not statistically different for the drilling parameters optimization problem.

Design optimization and performance analysis of natural gas hydrates (NGH) coring tool is a complex engineering system that involves several disciplines, such as structural, hydraulics, thermology and mechanism kinematics. An adaptive metamodel-based analytical target cascading (A-ATC) method is developed to efficiently deal with the NGH coring tool design problem. The NGH coring tool design problem is decomposed into three subsystems through the proposed A-ATC approach; namely, the core tube subsystem, ball valve mechanics subsystem and hydraulic subsystem. Moreover, a parameterized lower confidence bounding (PLCB) scheme-based adaptive metamodel is introduced into A-ATC to replace the analysis module to alleviate the intensive computational burden. Optimization results of the NGH tool are compared with those of kriging-based ATC. The effectiveness of PLCB is investigated through comparisons with other commonly used infill strategies. The results show that the proposed PLCB-based A-ATC method is more appropriate for the NGH coring tool design optimization problem.

The mechanical dithered ring laser gyro (RLG) effectively overcomes the lock-in effect and ensures the sensitive accuracy of the low angular rate for the gyro. However, in the inertial measurement unit (IMU) system, the dither excitation of three RLGs causes the coupled vibration of the IMU structure, which could seriously limit the measuring accuracy of RLGs. In this paper, the vibration frequency response characteristic of laser gyro IMU is taken as the focus point, and the method of multi-rigid body dynamics is used to establish the dynamic model of IMU suitable for vibration frequency response analysis. On the basis of the model, the multi-degree-of-freedom coupling vibration of IMU with the gyro dither excitation is clearly described. A new IMU dynamic decoupling optimization method is proposed to minimize the coupled vibration frequency response, and compared with the previous optimal design method. The prototype experimental test results show that the coupled vibration of IMU is restrained more effectively by the proposed new method than by the previous optimal design method. Finally, on the basis of this new method, the measuring accuracy of the RLGs in the IMU system is improved, which is quite useful for practical engineering application.