Chaotic Vibration Analysis of the Bottom Rotating Drill String

Qilong Xue,Feng Sun,Ruihe Wang,Zhiyuan Huang

doi:10.1155/2014/429164

Abstract

Drill string vibration is a widely studied topic. This paper developed a real-time measurement system near the drilling bit and extracted the lateral vibration, longitudinal vibration time series of bottom rotating drill string. In order to reconstruct the phase space, we estimated the delay time with mutual information and calculated the embedding dimension through Cao’s method. Finally, the chaotic characterization of the system is analyzed by calculating the correlation dimension and the largest Lyapunov exponent. The results show that such system can exhibit positive finite-time Lyapunov exponents and a clear convergence toward the correlation dimension, which is a strong indicator for the chaotic behavior of the system. It is expected that the new dynamics found in this paper could be of potential implication to the control methods of the drill string vibration.

Highlights

In oil and gas drilling engineering, the well is created by drilling a hole 5 to 50 inches (127.0 mm to 914.4 mm) in diameter into the earth with a drilling rig that rotates a drill string with a bit attached
Lateral and longitudinal vibrations of the drill string have been undertaken extensive research since it proposed from mid-1960s, The main reason that caused the fatigue failure of the bottomhole assembly (BHA) [2] was considered to be the vibration of the drill string
The first minimum of the mutual information calculated for the lateral vibration and longitudinal vibration time series is obtained at τ = 172 (Figure 3(a)) and τ = 160

Summary

Introduction

In oil and gas drilling engineering, the well is created by drilling a hole 5 to 50 inches (127.0 mm to 914.4 mm) in diameter into the earth with a drilling rig that rotates a drill string with a bit attached. Severe drill string vibration is a major contributor to downhole tool failure. It may cause hole damage and increase the need for more frequent rig repair. The drilling string vibration can be divided into three types or modes: lateral, longitudinal, and torsional. Many studies of the drill string focused on the determination of natural frequencies [3, 4], bending stress calculation [5, 6], stability analysis [7], lateral displacement prediction [8], and so forth. Spanos et al [9] established the finite element model of drill string lateral vibration and analyzed nonlinear random vibration

Methods

Results

Conclusion