This vade mecum is not designed to be a user's manual. It is intended to provide a simple account of both key arguments which underlie the concept and the terminology in use, its practical applications, limits and outlook. It explains how sequence stratigraphy is just a further development of classical stratigraphy. It shows how sequence stratigraphy allows to integrate sediment volumes, specific surfaces and the time value of both. This is to facilitate our understanding of the spatial arrangement of reservoirs, seals and source rocks, in order to forecast their extension and petrophysical parameters; in short, to improve out practice of petroleum geology.