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Sanchez + Wet Sands Beneath the TMS

Posted by bernell on October 24, 2014

The 3rd quarter operational report by Sanchez Oil and Gas released yesterday, October 23, mentioned the company had drilled above the “rubble zone” or in the upper portion of the Tuscaloosa Marine Shale.

The reason given, basically, is due to a possible water encroachment into the TMS production…something no one wants to see.  The cost of disposing of an excessive amount of water would run the cost of production to a likely prohibitive level.

 Here is the direct quote:

Both of these wells targeted the area above the rubble zone in order to avoid fracking into wet sands mapped immediately below the TMS.

Now, I vaguely recall an area of Wilkinson County being mentioned to me at one time as an area of concern for water encroachment, but I’ve not seen it mentioned as an issue in Amite County.  The two wells above refer to the Dry Fork East #1 in Wilkinson County and the St. Davis #1 in Amite County.

So, I’m hoping someone out there can further explain this “wet sand” and water encroachment issue to me.

I inquired of someone about this yesterday and here is my paraphrase of the response I got:

The Tuscaloosa A and B sands lie under the TMS.  There are some oil production fields utilizing this sand in the area.  Those oil sands are likely present in some areas, while in other areas this sand may be filled with water instead and in other areas the sand is non-existent.

(My source is unaware of any maps addressing the possibility of fracing into water.)

Water encroachment, by definition, implies production of water from the formation that is oil productive, that is, water native to the producing formation.  Water from other formations, up-hole or down-hole, can be caused by:

  1. A poor cement seal in the production casing/formation annulus between the producing interval and the water formation.
  2. Fracture propagation up and down to a water formation.  The possibility of this happening is dictated by rock mechanics in the various formation, fracture stimulation rates and volumes and who knows what else. 

(My source here indicated this was not an area of expertise.) 


Surely some of you out there who can expound upon the subject for us poor ignorant souls out in TMS land. 

Inquiring minds here!

Please give us any help you can. 

What do you think about it?