Simulation and Testing of an Isolator Tool for High-Frequency Torsional Oscillation

Abstract

During downhole drilling, severe vibration loads can occur that affect the reliability and durability of tools in bottom-hole assemblies (BHA). These high-frequency torsional oscillations (HFTO) can cause premature damage to tools or their subcomponents. This paper presents dynamic simulations, prototype testing, and field test results of a BHA component that isolates the upper part of the BHA from HFTO. This isolation increases the performance and reliability of BHA components through reduction of the vibration load. The paper provides a brief summary of the theoretical background for predicting the critical torsional eigenfrequencies, mode shapes, and susceptibility of BHA design to HFTO. Finite-element (FE) models were used to simulate the effect and efficiency of the isolation. The isolator tool was tested in a full-scale laboratory test setup that emulated the critical mode shapes to analyze the torsional dynamics and the expected isolation effect. A BHA with the isolator tool positioned between a rotary steerable system (RSS) and measurement while drilling (MWD) tools was excited in the critical HFTO mode shapes with an electrodynamic shaker. Vibration response was measured using triaxial accelerometers. Later, the tool was tested in the field in a BHA configured to log the vibration below and above the tool at sufficiently high sample rates to validate the isolation effect of the tool. The laboratory results showed the isolating effect between BHA components above and below the isolator tool, in particular for the critical HFTO-frequencies and mode shapes as predicted by the finite-element simulation. The torsional deflection shapes from testing using distributed triaxial accelerometers showed a high correlation with the predicted mode shapes from the FE model. The measurements from the field test also identified the isolation effect between the BHA sections. The measurement data showed that as predicted only the lower part of the BHA below the isolator tool oscillated at non-critical torsional eigenfrequency. The isolator tool reduced torsional vibrations and improved tool reliability, tool lifetime and service delivery, especially while drilling in formations that are susceptible to excite HFTO.

A Review of the Research and Development of High‐Frequency Measurement Technologies Used for Nonlinear Dynamics of Drillstring

“…Further investigation on detailed mechanical components in the BHA and geophysical/geomechanical parameter changes in lithology will be required. In fact, obtaining accurate Figure 30: e isolator tool comprised in a typical field BHA and its effect [75,76].…”

“…Although HFTO can be measured and its effect is modeled and predicted, little can be done to mitigate HFTO while still maintaining efficient drilling, a string component with certain mass and stiffness properties could be used to isolate a portion of the BHA from HFTO. Based on restricting potential damaging HFTO vibrations to a part of the BHA that is designed strong enough to survive HFTO, tools for isolating HFTO from the lower to the upper part of the BHA have been developed by Heinisch et al [75] and Carpenter [76]. By using this isolator tool, the BHA is modified so that critical HFTO mode shapes only have significant amplitudes in the section below the isolator tool, preventing the propagation of higher-frequency torsional vibrations upward the BHA and string, as shown in Figure 30.…”

A Method for the Design and Optimization of Nonlinear Tuned Damping Concepts to Mitigate Self-Excited Drill String Vibrations Using Multiple Scales Lindstedt-Poincaré

“…It has been shown that, for the torsional dynamic of the drill string, the energy input can be modeled using a nonlinear torque characteristic at the bit [8]. Due to improved and new measuring tools, high-frequency oscillations have been identified as the cause of numerous drill string failures and have been intensively investigated over the last years with studies [9,10], simulations [8,11] and experiments [12,13]. Especially drilling in hard and dense formations leads to highfrequency torsional oscillations (HFTO) with frequencies between 50 Hz and 500 Hz [14,15].…”

“…As neither the parameters nor the design of the drill string can be changed arbitrarily, new downhole tools must be developed to reduce critical vibrations. An isolator tool based on the principle of mechanical low-pass filtering is analyzed in testing, simulation and operation [13] and reduces the amplitude in specific areas of the BHA. As the isolator does not mitigate the critical vibration along the entire drill string, further mitigation strategies are necessary.…”

Design and Investigation of a Nonlinear Damper Based on Energy Dissipation through Shock and Dry Friction to Suppress Critical Self‐Excited Vibrations in Drilling Systems

“…Since the drilling parameters cannot be adjusted arbitrarily, further concepts have to be investigated. In downhole drilling systems, concepts based on isolation [14], energy transfer [15], and additional damping [12,13] have been discussed in the literature. Additional tools that are placed within the drill string have been investigated to reduce critical torsional vibration.…”