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Permalink Reply by Area Man on October 7, 2011 at 6:49am

Wet gas means the produced hydrocarbon has a higher amount of heavier chains - methane (CH4) is the smallest, lightest hydrocarbon chain, but as you build the chain longer and heavier (ethane C2H6, propane C3H8, butane, pentane, hexane....) the molecules become heavier and have different properties.  In fact, at surface conditions (that is, not in the well) ~pentane and heavier condense out of the gas phase.

SO, a dry gas means a higher percentage (nearing 100%) of methane where no liquids will drop out.

A wet gas has some fraction of heavier hydrocarbon molecules that will drop out of the gas once on the surface.

 

The biggest distinction to note is this wet gas/condensate/natural gas liquid (all more or less analogous) is NOT oil.  Oil is further down the chain still and has much different properties.

HOWEVER, the natural gas liquids as a commodity can be sold more or less as oil.

 

Hope that helps!

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Permalink Reply by Melissa on October 8, 2011 at 5:31am

Area Man...thank you for the explanation.  Makes sense.

Does this mean that Utica......is only in the wet zone?   Or is it also under the Marcellus?  Also, is it possible to be oil under the dry gas?  If I'm understanding right.......Oil is in Utica?

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Permalink Reply by Area Man on October 8, 2011 at 9:26am

As far as I know, there is no oil at all in either the Utica or Marcellus.  There seems to be significant quantities of NGLs (natural gas liquids) though.  I know it may be semantics for some, but it is an important distinction.  So yes, there are spots of both shales that are in the "wet" zone.

Generally speaking, wet versus dry gas is a matter of maturity, which is primarily based on temperature.  As temperature increases with depth in the earth, the deeper things are the more mature.  Thus, when you see maps of wet/dry gas, the main component there is depth.  As the Marcellus/Utica becomes more shallow/closer to the surface, it is less mature and more likely to produce liquids.

And to answer your other question, yes in general there can be oil underneath gas - this is very common in more conventional reservoirs.  You can have a large oil reserve and any associated gas will rise to the top (as it is more buoyant).

Hope all of that makes sense!

Cheers.

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