Advanced Technology Upgrades in Downhole Torsional Dysfunctions Mitigation to Improve Rotary Steerable System (RSS) Reliability

Abstract High frequency torsional oscillations (HFTO) are detrimental to Rotary Steerable Systems (RSS) which are extremely costly to be fixed. This paper will describe some innovative upgrades in downhole torsional mitigation tools and will evaluate their performance in a field case study. The paper will showcase the development of a downhole technology aiming to alleviate the torsional vibrations and increase downhole drilling equipment reliability. The overall approach of the project consisted of first, identifying the magnitude and frequency of the torsional dysfunctions in three wells utilizing high-frequency downhole sensors in the bottom hole assembly (BHA) which is placed below the mud motor. Secondly, after identifying the main causes of the downhole failures in the RSS and measurement while drilling (MWD) tools, a solution was created to address these dysfunctions. Lastly, two different downhole torsional technologies were designed for field trials and performance evaluation to confirm the anticipated performance of the upgraded tools. Before performing the three wells study to identify the main types of vibrations, the operator believed that stick-slip was the only dysfunction causing the downhole tools failures, but the findings from the downhole sensors’ study showed high levels of HFTO as well. Based on the identified source of vibrations, the study came up with two technology modifications (Technology A and B), both aimed to mitigate stick-slip and HFTO and they were deployed for field trials after the design and manufacturing stages. Both technology upgrades tackle torsional dysfunctions but have different working mechanisms; technology A introduces mud lubrication to specific elements in the tool while technology B has internal upgrades for extra vibration dampening. Both downhole torsional technologies were trialed each in four wells drilling in the same formations to compare the effects of deploying both technologies in mitigating stick-slip and HFTO. Downhole torsional technology B showed significant improvements in decreasing stick-slip and HFTO, reaching as high 50% when compared with downhole torsional technology A which showed improvement not exceeding 15%. This paper introduced, for the first time, an innovative technology that can introduce remarkable improvement in the performance of Rotary Steerable System (RSS) as shown in the case study. The paper discusses two technology upgrades to the RSS and compares them in terms of field deployment and efficiency.