of a reducing agent does not favor the formation or the maintenance of the 

 nitrates and also, to a lesser degree, of the nitrites; whereas it permits the 

 formation and the maintenance of NH 4 , which can attain extremely high values. 



Phosphates (PO ; ) 



The lime phosphates also are much less soluble than the alkaline phosphates. 

 Calcium also regulates the concentration in the phosphoric ion of the water. 

 In the connate waters, the concentration in phosphate is not especially high. 

 More often it is absent or does not exceed about 10 milligrams of P0 4 . Where 

 high values are found, the waters generally contain high concentrations of 

 sodium. Perhaps the high concentrations in C0 2 of petroleum water are also 

 contributing causes. There does not seem to be a direct relationship between 

 these very high concentrations and the presence of petroleum. 



In the underground waters charged with C0 2 and humic acids, such as 

 peat bogs, phosphorus is found frequently in very high concentrations. 



Acids and Carbonic Gas (HCO , CO , CO ) 



The connate waters are characterized by a high concentration in free 

 carbonic gas which reflects in a strong concentration in HC0 3 ions. The greater 

 part of the gases of petroleum beds have higher concentrations of C0 2 than 

 the atmosphere or the atmosphere above the underground waters. 



Sodium (No) 



Sodium is extremely variable in formation waters, as it has different 

 origins. It can come either from soluble sodium salts, enclosed in the sedimentary 

 rocks, Na 2 C03, Na 2 S0 4 , NaCl, but more particularly NaCl (because the first 

 are more rare) , or from the decomposition of the silicates, particularly the 

 feldspars. The latter decomposition is difficult, much more difficult than the taking 

 in solution of the free sodium salts in the rocks. Another source of sodium is 

 in the exchange of bases. The solution of soluble salts brings chlorine into the 

 water, little S0 4 , little C0 3 , because of all the soluble sodium salts in the rocks, 

 NaCl is most abundant. 



Potassium (K) 



The potassium content in connate waters varies considerably, but some- 

 times it is much less than that of sodium. It is generally missing in the waters 

 of weak concentrations. The ratio K/Na is a function of the concentration in 

 sodium (Schoeller, 1955). 



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