イラクの石油ポテンシャル―石油地質概要と南部の大規模未開発油田―

Abstract

Geological Survey Department of Japan National Oil Corporation has been conducting in-house studies on petroleum geology and undeveloped giant fields of Iraq, and this paper gives an outline of the results of the studies. Iraqi oil fields have the following characteristics: i) Main reservoirs are the Cretaceous carbonate and sandstone rocks in southern oil fields and the Tertiary carbonate rocks in northern oil fields, ii) Typical structures are gentle anticline in southern oil fields and steep anticline with reverse fault in northern oil fields, iii) Oil fields have multiple reservoirs. In southern Iraq, there are many undeveloped giant fields including Majnoon, West Qurna and Bin Omar fields, which have reserves of more than 5 billion barrels. Main reservoirs of the fields are the early Cretaceous Yamama formation, Zubair formation, Nahr Umr formation and the late Cretaceous Mishrif formation. The area where each formation shows good reservoir properties are restricted and this can be explained by the difference of depositional environment of the formation in the area. Development costs of the undeveloped fields in southern Iraq are estimated to be from hundreds of millions of dollars to billions of dollars although unit costs($/bbl) for the development are fairly low. Difference in productive formations and/or operation environments(desert or swamp) affect the development costs.