Aug 17 Fireside Chat with JRI and Scott Macmillan, page-405

"If I remember correctly the fracturing was early on in M1 prior to the sidetrack and caused them to add something to plug the holes they’d made"

Okay that's to do with loss of drilling mud into the formation due to high permeability within the formation. I got the impression this was due to naturally occurring fractures rather than fractures induced by the mud itself. The material added to the mud to plug the loss zone is called Lost Circulation Material or LCM. LCM can consist of a wide range of ingredients varying from mica to nut hulls...to sized calcium carbonate. In a worse case scenario cement can be pumped into the formation.