The Axial Agitation System Effect on Rotary Steerable Drilling: ADNOC Offshore Mature Field Case Study

Abstract

Abstract The drilling industry faces several challenges related to downhole vibration; amongst the solutions introduced to alleviate those challenges, a unique Axial Agitation System is often considered. This paper qualitatively analyses the effect of the Axial Agitation System in directional drilling and quantifies how it addresses the above challenges observed in Rotary Steerable System (RSS) Bottom Hole Assembly (BHA) used in the 8.5 in. section in different wells of the ADNOC Offshore mature field. The Axial Agitation System consists of Axial Oscillation Tool which generates a pressure pulse from a valve driven by mud flow converted to axial motion by The Shock Tool. The system complements the rotational movement of the string by introducing gentle and consistent axial oscillating motion. The drill string moves around its rotational axis, oscillating along its axial axis reducing kinetic frictional losses from interaction with the wellbore, especially in directional and long lateral sections. The analysis consisted in comparing drilling dynamics metrics between wells with AAS in the drill string and offset wells without it, in the 8.5in hole section. As a pilot project, the system was introduced into Well A. Based on the successful tests in the pilot well; the system was also utilized in Wells B & C. The metrics include, but are not limited to, drilling activities, surface mechanical indicators, downhole data from the RSS as well as mathematical modelled algorithms. The results of the analysis of wells clearly indicate an enhancement into the drilling dynamics in terms of overall reduction in kinetic friction, improved weight transfer, less hanging and levels of torsional dynamics, shocks and vibration. The collateral benefits also included performance improvement, reduced non-productive time (NPT) and lower mechanical specific energy (MSE) to drill the section. The Axial Agitation System complemented very well with the rotary steerable system as well as other BHA components and delivered consistent performance in all three wells. High amplitude fine-tuned Axial Agitation System paired with RSS BHA creates a combination of a highly efficient directional system. The results are consistently performance with reduction in the shock and vibration levels in the environment. This also benefits in improving tool reliability, directional control while also optimizing the repair and maintenance costs for the downhole tools.