When Is Unconventional Conventional?

Have you noticed?

If you have a pulse and have been to an AAPG Annual Convention and Exhibition (ACE) over the past couple of years or so, or a recent AAPG International Convention and Exhibition (ICE) such as those held in Calgary or Milan, you would have noticed.

Standing room only crowds at sessions focused on gas shales have become the norm.

It’s not limited to oral sessions, either – try finding a spot to view a poster or talk to the author(s). Overcrowding is a sign of the times.

And to add to what I perceive as good news, exploration for gas, oil and liquids in shale reservoirs is no longer restricted to the United States or even North America. These so-called unconventional reservoirs are now the focus of exploration on virtually every continent in the world.

It is not surprising that many AAPG members are actively involved in shale exploration or production, of which many are EMD members who have been instrumental in organizing technical sessions – and running short courses and field trips – at the ACE and ICE meetings, and in supporting Geosciences Technology Workshops (GTWs).


Defining unconventional may not be as easy as one would think – and we are not alone in our metaphysical thoughts about what is conventional and what is not.

The bank and loan industry, and medical and military strategists have these discussions all the time. Discussions as to what is conventional and unconventional have been an ongoing part of their respective dialogues.

Generally speaking, conventional things are of the ordinary while unconventional things would be out of the ordinary.

However, what you may think is ordinary could be completely different from my ordinary.

Natural gas enthusiasts divide unconventional gas into six main categories:

  • Deep gas.
  • Tight gas sands.
  • Gas-containing shales.
  • Coalbed methane.
  • Geopressurized zones.
  • Arctic and sub-sea hydrates.

Whether these gas deposits are unconventional or not changes over time, and from deposit to deposit, with economics dictating whether a particular deposit is unconventional or not.

If a natural gas deposit is too costly to extract, it is unconventional.

For those who prefer Wikipedia, unconventional oil is defined as petroleum produced or extracted using techniques other than the conventional oil well method.

The growing interest in unconventionals is credited in large part to technological advances and innovative new processes – or a cheaper way of doing something. That is all that is needed to turn what was once deemed unconventional to conventional.

Regardless, to make sure we all know what the chatter is about, unconventionals from EMD’s perspective are:

Those energy resources that do not occur in discrete oil and gas reservoirs held in structural or stratigraphic traps in sedimentary basins.

Think gas shales, shale oil, tight gas sands, oil (tar) sands, coalbed methane, oil shales, gas hydrates, etc.


Conversation about shale reservoirs – as demonstrated at the 2010 ACE in Houston and 2011 ICE in Milan – has evolved from that of just a few years ago. Instead of looking for a talk about the next “hot” shale prospect in the United States, technical sessions are now about revising our understanding of the processes under which organic-rich shales are deposited and subsequently evolve into prolific unconventional reservoirs.

And all these new and innovative ideas about shales have spawned a host of additional questions that are being addressed by bringing new technologies into the shale discussions. The use of advanced SEM imaging to view porosity in shales, sometimes the only means to view porosity, is just one example.

New terms also are being spawned. Understanding the nature and distribution of pore types in shales is evoking terms like “nanoporosity” and “organic porosity.”

And even though the concept of unconventionals such as gas shales are becoming more mainstream, understanding flow in shales is anything but conventional. Formulating new models focused on fluid flow in rocks characterized by low porosity and permeability remains challenging.

These topics, among many others, were the subject of much discussion and debate at a recent Hedberg Conference on shales, of which EMD was a co-sponsor.

As we move forward in what is a dynamic energy landscape, topics pertaining to unconventional resources are at a premium.

The organizing committee for both this year’s ACE (April 22-25 in Long Beach, Calif.) and ICE (Sept. 16-19 in Singapore) is committed to incorporating presentations on shales and other unconventional reservoirs. Much is happening throughout the world in the area of unconventional resources.

For a comprehensive overview of current research and stages of development, check out “Unconventional Energy Resources: 2011 Review,” published in Natural Resources Research (Volume 20, Number 4, December 2011, pages 279-327). This gem contains nine unconventional energy resource commodity summaries prepared by various committees of EMD.

In the meantime, EMD remains committed to bringing pertinent information to the AAPG membership about these so-called conventional unconventionals.

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Division Column-EMD Stephen M. Testa

Stephen M. Testa is EMD President-Elect. He is currently serving as Executive Officer of the California State Mining and Geology Board since August, 2005. Testa is a Past-President of the American Geosciences Institute (AGI), the AIPG and the Los Angeles Basin Geological Society.

Division Column-EMD

The Energy Minerals Division (EMD), a division of AAPG, is dedicated to addressing the special concerns of energy resource geologists working with energy resources other than conventional oil and gas, providing a vehicle to keep abreast of the latest developments in the geosciences and associated technology. EMD works in concert with the Division of Environmental Geosciences to serve energy resource and environmental geologists.

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The Energy Minerals Division (EMD), a division of AAPG, is dedicated to addressing the special concerns of energy resource geologists working with energy resources other than conventional oil and gas, providing a vehicle to keep abreast of the latest developments in the geosciences and associated technology. EMD works in concert with the DEG to serve energy resource and environmental geologists. 

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