Table 2: Chemical differences between Gachsaran formation water and drilling fluid that used in Gachsaran section.

Chemical properties Drilling fluid Formation fluid
Density variable 1.2 (gr/cm3)
pH 9-10.5 6.1
Salinity 320,000 296,000(mg/l)
Calcium(from anhydrite/CaCl2) <400 28,100(mg/l)
Magnesium(from MgCl2) <100 7,600(mg/l)
Sulfate(from anhydrite) NIL 2,000(mg/l)
Carbonate NIL 125(mg/l)
Bicarbonate NIL 75(mg/l)

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