Activating Shale Can Create Well Barriers

This paper discusses shale creep and other shale-deformation mechanisms and how an understanding of these can be used to activate shale that has not contacted the casing yet to form a well barrier. The authors then explore methods of activating shale for this purpose, concluding that inducing a pressure drop in the annulus is the most-promising such method.

Introduction

Creep is a well-known phenomenon in engineering in many materials. In rocks, it is related typically to grain rotation, grain sliding, cement cracking, and, in some cases, even grain cracking. The rock matrix has a viscous behavior wherein time is required to achieve new stress equilibrium at the grain-contact level as the bulk rock volume is exposed to an altered stress state.