Hydrocarbon Potential of the Jurassic Carbonates - An Emerging Play in the Sulaiman Foldbelt, Pakistan

Khan, Gulzeb N.¹; Anwar, Muhammad Kaleem ¹; Daud, Farrukh ¹
(1)Exploration & Reservoir Management, OMV Pakistan (Exploration) GmbH, Islamabad, Pakistan.

The objective of this paper is to provide an extensive evaluation of the hydrocarbon prospectivity of an emerging Jurassic Carbonate play of the Sulaiman Foldbelt of Pakistan, through a comprehensive study based on structural analysis, petroleum systems modeling and source & reservoir quality determination. The first high BTU commercial discovery in Jurassic carbonates (Chiltan) has been made at Dewan-5 in 2008 in Salsabil D&PL (ex Rodho structure). The input data for the study includes 2D seismic, digital elevation model, well logs, outcrop data, and geological maps. The Sulaiman fold belt, a proven petroleum province, has so far delivered 15 Tcf of gas, primarily from Eocene reservoirs; however, it is still not fully explored with a YTF potential of about 5 Tcf in the province.

This tectonically active foldbelt was initiated during the collision of the Indian and Eurasian plates throughout the Tertiary time. The peculiar shape of the Sulaiman Lobe is developed as a result of left lateral and right lateral strike slip movements along the eastern and western Sulaiman wrench zones respectively. Sequential restorations of the balanced cross sections, constrained by the seismic, challenges the Passive Roof Duplex Models presented earlier by Banks and Warburton, 1986 & Jadoon etal,1992.

In order to better understand the reservoir quality of the Jurassic carbonates, facies maps along with paleo-geomorphological maps have been constructed. The petroleum systems modeling study concluded that in order to achieve the observed maturity levels, an increase in the paleotemperature distribution should have occurred prior to structuration and that the thermal regime was not constant throughout the geological time. The above conclusion was drawn based on the burial history and maturity profiling for the Jurassic & Cretaceous source rocks. As a critical input data, the geo-thermal gradient map has been generated using the corrected bottomhole temperatures (BHTs) of nearly 100 wells in the fold belt and the foreland basin.

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