Drilling Optimization using High Frequency Data Measuring Torsional Oscillations (HFTO) and Corresponding Frequencies Provided by Downhole Tools, Supported by Extensive Scientific Pre-Job BHA Modeling Allows to Reduce Downhole Tool Failures and Improve Performance
Authors: de Souza Ricardo L. B. , Fadhel Hussain Al , Malik Kashif A. , Zapata Jose 
Published: February 2024

Abstract
High Frequency Torsional Oscillation (HFTO) in recent years have been a greater topic of discussions in the drilling and measurements industry. It has been a common and frequent subject of studies from different companies and groups as it has been a damaging factor in different equipment failure. As of recently, the industry has been able to collect data from different downhole tools to implement in HFTO pre-run modelling. This is done mostly with data collected from tools’ memory. However, this approach has its limitation as different HFTO frequencies are triggered and depending on the mode-shape of it, the sensor will read different g loads. The sensor might be close to a node and it will show low readings, where in reality the loads are much higher at different areas of the BHA. As a result, HFTO pre-modeling is time consuming and involves studying previous cases to have a model with good accuracy since there are many different possible frequencies with multiple mode-shapes that could be triggered. Today, the industry has evolved to have down-hole tools with the ability to transmit HFTO drilling dynamics in real time.
One of the accomplishments with advanced tools is the ability to transmit triggered HFTO frequencies in real time in addition to g loads at sensor position. These values are used to calibrate the pre-run HFTO model and extrapolate the g loads at any point on the BHA prone to failure in real time. With real time HFTO modeling, a comprehensive HFTO management and a mitigation course of action can be implemented while drilling. This approach has resulted in increasing downhole tools’ reliability and minimizing non-productive time for client.
For the work presented in this study, 13 cases were investigated to create HFTO pre run model. The study came after several and similar RSS failures while drilling similar well profile and formations. All failures were found to be root caused to HFTO vibrations since vibration related damage was found inside the Steering Unit (SU) electronic boards. The objective was to simulate the g loads on different parts of the BHA to optimize its design and set boundary limits.
To validate and fine tune the model, two downhole tools measuring HFTO levels and frequencies at different points of the BHA were utilized. While drilling we observed that the actual dominant HFTO frequency with g load levels, were close to the simulated in the model, thus validating the effectiveness of the model. Furthermore, based on this real time data, parameter optimization was done in real-time to reduce the severity of HFTO vibrations in the electronics for all of the directional, MWD and LWD tools as the section was drilled. This resulted in reducing the component failures that had happened in the earlier wells and allowed to drill the well without any failures from these high frequency torsional vibrations.
Overall the real time parameter optimization using downhole drilling dynamics tool supported by the prejob BHA modeling allowed a considerable reduction of downhole tool failures that was seen in the past from high frequency torsional oscillations. The learnings are being used for further optimization and this has also allowed to validate the modeling of vibrations on similar application & under the similar downhole environment.