Underreamer Block with Conical Diamond Elements – Concept, Design, Optimization, and Field Tests

Trunk, Philip (Schlumberger) | Nasief, Mary (Schlumberger) | Shi, Kevin (Schlumberger) | Long, Wiley (Schlumberger) | Terracina, Dwayne (Schlumberger) | White, Allen (Schlumberger) | Tocantins, João Pedro (Schlumberger) | Costa, Edson (Schlumberger) | Louback, Leonardo (Schlumberger) | Hird, Jonathan (Schlumberger) | Aguiar, Romulo (Schlumberger)


The function of an underreamer is to enlarge an existing wellbore below frequently encountered restrictions such as drift diameter of casing or the wellhead (Figure 1). This can be done by underreaming while drilling (URWD), also known as hole enlargement while drilling (HEWD), where the reamer in the BHA enlarges the pilot hole created by the bit while the hole is being drilled.