The complete paper presents the results of an investigation into the creep behavior of North Sea shales and their ability to form effective annular barriers. The large-scale laboratory results show that Lark-Horda shales will form competent low-permeability annular barriers when left uncemented, as confirmed using pressure-pulse-decay measurements. Experimental conditions were found to influence the rate of barrier formation. Higher effective stress, higher temperature, and beneficial manipulation of annular fluid chemistry all have a significant effect.
Introduction
An alternative to traditional plug-and-abandonment techniques presented itself more than a decade ago, with observations that formations such as mobile salts and shales could creep into uncemented annular spaces and form competent annular barriers that could be identified on sonic and ultrasonic bond logs and verified using pressure testing.
