Abstract:
Minwal is situated in the Punjab province of Pakistan. This thesis contains the
study of 2D seismic reflection data interpretation of selected seismic lines (MN-02,
MN-04, MN-05 and MN-11) of Minwal, Potwar Plateau and Upper Indus Basin, for
delineation of subsurface structures favorable for hydrocarbon accumulation. Two
prominent reflectors (yellow and red) were marked on the basis of their reflection,
which represent Chorgali Formation and Sakesar Limestone respectively. Reflectors
were identified with the help of well top data, after conversion of time to depth with
the help of average velocity. Two-way time (TWT) from the seismic sections and
average velocities were used to create TWT and depth contour maps. Pop-up structure
bounded by two thrust faults was observed from the time and depth surfaces of two
formations. Chorgali Formation is of Early Eocene age and consists of shale and
limestone. The Sakesar Limestone is of Early Eocene and consists of nodular
limestone with chert. The Patala shale of Paleocene age is the source rock but
Precambrian Salt Range Formation also contains some potential. Reservoir rocks
include fractured limestone of Chorgali formation and Sakesar Limestone. Khewra
Formation of Cambrian age is the main potential reservoir. Clays and shales of the
Murree Formation act as traps. Petrophysical analysis shows two zones, Zone 1 for
Chorgali formation and Zone 2 for Sakesar Limestone. In Zone 1 average of shale is
20%; saturation of water is 21%; effective porosity is 0.17(v/v); fracture porosity is
0.4(v/v) and shale volume is 45%. Whereas in Zone 2 average value of shale is 55%;
saturation of water is 100%; effective porosity is 0.26(v/v), fracture porosity is
0.007(v/v) and shale volume is 32%. Hence Zone 1 seems to be a better reservoir
because it has less shale volume, good effective porosity and low saturation of water.
Whereas in Zone 2 shale volume is high, effective porosity is low and saturation of
water is 100%. In Zone 1 maximum value of hydrocarbon saturation is around 90%
whereas average hydrocarbon saturation is 20%. In Zone 2 hydrocarbon saturation
shale volume, effective porosity and saturation of water the Zone 1 seems to be more
promising hydrocarbon prospect zone.
