Oil Exploration in Southeast Turkey Thrust Belt: ABSTRACT

Abstract

The southeast Turkey thrust belt forms the foothills zone of the Late Cretaceous to late Tertiary Alpine orogenic belt, which frames the Arabian craton in southern Turkey and Iran. The thrust belt is characterized by imbricate structures and disharmonic folding. It comprises a northern inner belt in which Late Cretaceous and Tertiary tectonic phases are superimposed, and a southern outer belt in which Late Cretaceous thrusts underlie gently deformed Tertiary sediments. To the south lies the folded foreland. In southeast Turkey, oil has been found in middle Cretaceous carbonate rocks in the frontal overthrusts of the outer thrust belt and in middle and Upper Cretaceous limestones in faulted anticlines of the foreland. Over 300 exploration wells in this area have resulted in the discovery of about 40 oil fields of which 26 lie in the outer thrust belt. Two oil types can be distinguished: (1) low-sulfur, light crude, mainly confined to the thrust belt and thought to have been derived from Silurian source rocks, and (2) heavy, high-sulfur crude, produced from the foreland fields, probably derived from Lower Mesozoic source rocks. Oil prospects in the thrust belt are limited by reservoir deterioration toward the highly deformed inner thrust belt and by the distribution of Silurian source rocks. Exploration tools applied to locate the oil traps in the overthrusts include field gravity, bore-hole gravity, seismic reflection and refraction shooting, and structural trend studies based on subsurface data and theoretical models. End_of_Article - Last_Page 724------------