THE BAHAR OIL AND GAS-CONDENSATE HELD IN THE SOUTH CASPIAN BASIN

The Bahar Field was discovered in 1968 and contains oil and gas-conden sate in sandstones and sandy siltstones belonging to the middle Plioce ne Productive Series. This has a total thickness of 3600 m. It consist s of alternating sandstones, sandy siltstones and shales, with thickne sses between 5 m and 50 m and is of deltaic origin. The reservoir rock s have porosities of 13-18% and permeabilities of 45-250 mo. Biomarker geochemical analyses of onshore and offshore fields show that the Pli ocene oil and gas fields in the South Caspian Basin have been charged primarily from epigenetic hydrocarbons. The hydrocarbons have migrated vertically along faults from older source rocks, probably including o rganic-rich shales of Oligocene to early Micocene age. The Bahar Field is quite mature. Of the original hydrocarbons in place, 72% of the ga s has been produced, 39% of the condensate and 11% of the oil. The mai n oil-bearing horizons, the Pereriv Suite (SP) and Balakhany X, are de veloped with reservoir pressure maintenance by longitudinal and margin al (up-dip) flooding of surfactant-added sea water.