Development of a New Advanced Multiple Activation System for Concentric Underreamers

Abstract

Hole Enlargement While Drilling (HEWD) using a concentric underreamer is a widely used technique for efficient wellbore construction. Most underreamers are fitted with lock-out systems to provide a means of drilling out the shoe-track with the cutters close before enlarging the borehole below casing. Several vendors also provide a system to lock the tool closed after reaching total depth (TD) to enable full flow while pulling out of the hole for best possible wellbore cleaning. However, most available underreamers cannot be reactivated after deactivation. Another limiting factor is that the tools must be placed on top of the Bottom Hole Assembly (BHA) due to the ball drop activation method. To solve the problem, a new system has been developed that makes it possible to perform multiple activation/deactivation of the underreamer. The most obvious advantages are infinite open/close cycles for selective underreaming and the more flexible placement opportunities within the BHA due to the activation method. Other advantages are time saving through the elimination of several runs, shorter activation time and higher flow rate capabilities. Several successful tests in realistic drilling environments were performed prior to starting the field testing program. Through the field testing stage the system has performed as planned under normal drilling conditions and has a significant cost saving potential for the operator. The authors will discuss the application challenges, benefits, features and engineering efforts including field testing, that led to a commercial Ream on Demand (ROD) system.