This book gives background information why shale formations in the world are important both for storage capacity and enhanced gas recovery (EGR). Part of this book investigates the sequestration capacity in geological formations and the mechanisms for the enhanced storage rate of CO2 in an underlying saline aquifer. The growing concern about global warming has increased interest in geological storage of carbon dioxide (CO2).  The main mechanism of the enhancement, viz., the occurrence of gravity fingers, which are the vehicles of enhanced transport in saline aquifers, can be visualized using the Schlieren technique. In addition high pressure experiments confirmed that the storage rate is indeed enhanced in porous media.  The book is appropriate for graduate students, researchers and advanced professionals in petroleum and chemical engineering. It provides the interested reader with in-depth insights into the possibilities and challenges of CO2 storage and the EGR prospect.