Abstract: Structural
Traps
in the Potwar Basin, Pakistan
NIZAMUDDIN, MOHAMMAD. PAKISTAN PETROLEUM LTD., KARACHI, PAKISTAN
Surface structural
and stratigraphic data have been integrated with seismic and well information
to understand the mechanics and geometry of the Potwar Basin
structural
traps. Three representative structures are described briefly as examples
of the
structural
styles.
The Potwar Basin is an active frontal fold and thrust belt, formed as a result of late convergence of the Indian and Eurasian plates. The fold and thrust belt shows a thin skinned north to south deformation style, over a decollement provided by Infracambrian salt overlying crystalline basement of the Indo-Pakistan shield which dips 1 to 4 degrees towards the north.
The structural
growth in the
region commenced in the Oligocene Epoch. The main deformation occurred
during late Pliocene and Pleistocene. An average of about 22 km north to
south shortening was measured using
cross
sections
.
The structures within the basin
are generally East-West trending and asymmetrical with their steeper limbs
on the south. They were formed by compression from the north and were subsequently
modified by the flow of the Infracambrian salt and anhydrite. However,
the salt flow itself was not responsible for the creation of the structures.
The north-dipping major faults which control the anticlinal development
are imbrications from the main detachment surface, the Infracambrian Salt
Range Formation. The south-dipping faults, which also control many structural
traps, are present as secondary pressure-release back-thrust features.
They often obscure the evidence of original movement from the north.
About 100 exploration wells have been drilled resulting in 20 hydrocarbon discoveries. Potential exists for more success.
AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria