"Current lithology is evaporites comprising anhydrite and salt."
For those of you who don't know, the below extract comes from the Kansas University Geology of Petroleum (gas) publication.
"Evaporites are formed by the direct precipitation of minerals by evaporation of seawater. Resulting rocks are ordinary salt (halite-sodium chloride), gypsum (calcium sulfate with some water), and various forms of potash salts. When gypsum is buried to considerable depths, the water is expelled from the crystals and "anhydrite" (meaning simply "without water"), a harder crystalline rock, results. Evaporites are not porous, although they are readily dissolved by water and are not source rocks for petroleum. However, they may be formed in highly stagnant water where black mud, rich in organic matter, may also be deposited, and so are commonly associated with good source rocks. Because they are impermeable, evaporates often form seals on other reservoir rocks. Evaporites of the Sumner Group form the upper seal of Chase Group carbonate reservoirs in the giant Hugoton gas area in southwestern Kansas."
It goes on to explain that the faults where we are drilling in PB2 are natural structural 'traps' for petroleum and gas.
Cheers, Pie :)
GDN Price at posting:
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