Conventional/Unconventional Reservoir


I am looking at The Application for Multiunit Horizontal well I received and they list reservoirs as conventional and unconventional. What does this mean?



Conventional reservoirs are those reservoirs such as sandstones and limestones with reasonable porosity and permeability. Typical old wells of Oklahoma with vertical wells with some directional or horizontal wells.

Unconventional reservoirs are formations such as shales with low porosity and permeability that cannot produce without special completion techniques such as high pressure and proppant frac’ing. Examples are the Woodford, Hunton, Mississippian Shales, Goddard Shales.

I can get you an exact definition, but is that close enough for now?


That is close enough, Martha. Thank you.


The Shale act allowed for the multi-unit drilling of the shales in order to save money by drilling one long well across one or more sections instead of two shorter wells-one in each section and having to abide by the easements on the edges of the sections and not draining them. That is why they mention the “unconventional”. Recently, the legislature also approved long laterals for conventional reservoirs. When they use “unconventional” pretty much means the tight shales or tight limestones.