“My concept of reservoirs has completely changed.” I actually
heard an engineer say these words – last summer, while attending
a technical conference of geologists and engineers – and he was
referring to the rapidly evolving concepts of reservoirs
generated from shale gas reservoir research. At the time it
struck me that it was very unusual for an engineer to say this
because, in my experience, engineers are sometimes more
resistant to change than geologists. Thinking of shales (or more
correctly, mudstones) as reservoirs, however, is an example of a
significant evolution of thinking – a progression also known as
a paradigm shift. For example, geologists of my generation
learned that shales can act as source rocks when they contain
abundant organic matter and as seals when they cover porous and
permeable sandstones or carbonates. Thinking of a shale as a
reservoir, then, is a sometimes-difficult paradigm shift for
geologists of my age. Paradigm shifts occur from time to time –
and, clearly, they can profoundl