Theoretical Estimation of the Drilling Rates Comparing the Evans and Nishimatsu Models in Relation to the Offshore Piles

Abstract

Driven piles are the main foundation system for offshore oil and gas facilities. They are installed through the jacket legs or at the bottom of the structure. Driven piles can, however, experience premature refusal. In this case, drilling solutions may be needed, such as drilling to remove the plug ahead and below the pile toe. Because time is important during offshore operations, offshore bored piles are rarely used. Unlike pile drivability analysis, which is based on wave analysis and hence reliable, there is no established pile-drillability assessment. This paper extends the findings of previous research in which the specific excavation energy (SEE) was estimated in subsoils from Turin, Italy, at a small scale. Two subsoil classes were considered and compared in this study. The SEE was linked to different friction-angle and cohesion values, and using the Nishimatsu and Evans cutting models, preliminary theoretical net drilling penetrations were estimated. The results should be considered as theoretical values.