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FORMATIONAL WATER CHARACTERISTICS AS AN INDICATOR FOR THE PROCESS OF OIL MIGRATION AND ACCUMULATION AT THE AIN ZALAH FIELD, NORTHERN IRAQ
Author(s) -
EIzarka Mohamed Hossny,
Ahmed Walid Abdel Majid
Publication year - 1983
Publication title -
journal of petroleum geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.725
H-Index - 42
eISSN - 1747-5457
pISSN - 0141-6421
DOI - 10.1111/j.1747-5457.1983.tb00414.x
Subject(s) - geology , capillary pressure , oil field , wetting , fault block , petroleum engineering , oil in place , geochemistry , water injection (oil production) , fault (geology) , petroleum , geotechnical engineering , paleontology , composite material , materials science , porous medium , porosity
Formational water characterization denotes a chloride‐calcium type in the S 1 S 2 A 2 class. It indicates a hydrodynamic zone unfavourable for hydrocarbon preservation in the eastern block of the field. These waters have an index of base exchange (IBE) greater than 0.129, indicating connate oil reservoir waters, migrating with oil from the oil source‐beds at the southern parts of the field through connected openings and fault planes. The entrapment of oil took place at the crestal parts of the folded structure to the west and NW of the field. The water moved down‐dip along the eastern flank, creating capillary pressure, forcing the oil to accumulate in subcapillary pores at the top‐most parts of the upper pay‐zone. The latter section became oil‐wet. The oil wettability led to entrapment of a quantity of oil in the subcapillary pores that was then left behind during oil production operations, necessitating secondary recovery methods. The occurrence of more lighter constituents in crudes of the upper pay‐zone than in the lower one is due to fractionation and differentiation during migration.