Detachment Tectonics and Its Implication for the Hydrocarbon Exploration In Western Kohat Foreland Basin, Northwest Himalayas, Pakistan

Khan, Mohammad I.¹; Ahmad, Sajjad ²; Khan, Moin R.³
(1)Exploration, MOL Pakistan Oil & Gas, Islamabad, Pakistan. (2) Geology, University of Peshawar, Peshawar, Pakistan. (3) Exploration, Pakistan Petroleum Limited, Karachi, Pakistan.

This study presents the outcome of structural mapping and modeling conducted in the western Kohat foreland basin located in northwest Himalayas, Pakistan and have better constrained the structural events, the quantification and nature of multiple detachments and the geometric relationship between surface and subsurface hydrocarbon bearing rocks. The structural style of the western Kohat foreland basin is typical of thin-skinned deformed terrains and is mainly controlled by a couple of regional scale structural detachments, confined to base-Precambrian and Eocene rocks. These detachments divide the stratigraphic sequence of the Kohat foreland basin into two structural-stratigraphic domains. The lower domain consists of a mechanically rigid succession of Cambrian to Paleocene rocks fabricated by a series of south-verging, fault-propagation folds which constitute the main hydrocarbon play of the region. The upper structural-lithologic domain is relatively more ductile and is comprised of Eocene to Pliocene rocks fabricated by tightly folded, internally thrusted and doubly overturned anticlines separated by broad synclinal lows. The east west trending surface structures developed in the upper domain are related to detachment thrusting in the Eocene rocks. The total amount of shortening is found to be 36% for the lower domain and 25% for the upper domain, suggesting shear along the base-Eocene detachment. The two domains have deformed disharmonoically; hence the geometry of surface anticlines does not imitate the geometry of subsurface hydrocarbon bearing anticlines.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.