--> Stages of Development of Jaccobabad-Khairpur High and Its Impact on Petroleum Plays of the Region, Southern Indus Basin, Pakistan – An Overview Based on Well Data

AAPG ACE 2018

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Stages of Development of Jaccobabad-Khairpur High and Its Impact on Petroleum Plays of the Region, Southern Indus Basin, Pakistan – An Overview Based on Well Data

Abstract

Jacobabad-Khairpur High (JKH), a part of Sukkur Rift Zone, trending NNW-SSE is a part of Lower Indus Basin and evolved during Jurassic rifting when Indian Plate separated from Australian-Antarctic plate. At that time fractures developed due to upwelling of magma and resulted in the development of detached blocks that dropped relative to other ones. JKH represents probably one of those blocks which maintained its original position. This study works out the causes of failure of exploration wells drilled at and in the vicinity of JKH and comprehends the tectonics, structural trends and subsurface geology of the region to delineate role of JKH in distribution of source, reservoir and seal rocks for future prospects. This work is based on construction of stratigraphic cross sections along and across JKH, isopach, depth and isocore maps to delineate paleo and present shapes of JKH and its impacts on the petroleum system of the region for further exploration.

This study indicates that JKH developed in three stages from Jurassic to Early Eocene time. Initially JKH developed after the deposition of middle Jurassic Chiltan Limestone and remained uplifted. This interpretation is supported by the absence of main source rock, Cretaceous Sembar Formation, of the basin on the northern and southern crest of the JKH and absence of entire Cretaceous succession on the northern part of the JKH indicating subaerial conditions. Moreover, Cretaceous reservoir rock, Lower Goru Sand, is also absent in the northern portion of the high as Paleocene Dunghan Formation is directly overlying the Chiltan Limestone. Furthermore, due to absence of marl and shale of upper Cretaceous Goru Formation (seal rocks) proper seals are absent in the area. It resulted in the dry holes like Kandra-01, Khairpur-01, Khairpur-02 and Jhatpat-01. However rocks of petroleum system were deposited all around JKH. At the same time presence of Cretaceous source (Sembar Formation), reservoir (Lower Goru Sand) and seal (Goru Shale) rocks around JKH resulted in many discoveries of oil and gas in Middle and Lower Indus Basins. JKH submerged again during Paleocene when the Indian Plate passed over Kerguelen Hot Spot and became a part of the carbonate shelf to deposit Dunghan Formation over Chiltan Limestone in the northern part of the high. Finally JKH again reactivated and uplifted to the present position, after the deposition of early Eocene Ghazij Formation when Indian Plate collided with Eurasian Plate.