Abstract:
Geologically Tajjal Gas Field (Gambat Block) lies in Lower Indus Basin -a proven
Geological Province in the Islamic Republic of Pakistan. The field was discovered by
OMV Pakistan and is one of the productive fields. The dominant structural styles in Lower
Indus basin is normal faulting due to its extensional tectonic regime. The stratigraphic
sequence is composed of Jurassic to most recent age rock formation. Based on the synthetic
seismogram two horizons Top Lower Goru and B-interval are marked. Time and depth
maps define the dip of the area. Faults marked at the reservoir level B-interval has less dip
as compared to fault marked on the Top lower Goru. Structural interpretation carried out, is
confirmed through post stack seismic attributes. Reservoir properties are estimated through
Petrophysical analysis using borehole log data. B-interval sands are clean and show good
porosity at the well location. Petrophysical properties namely Porosity and volume of shale
are also computed at the seismic level, through post stack seismic inversion using Model
based inversion and Band limited inversion. The aim of post stack inversion is to evaluate
the sands of B-interval in terms of its porosity and volume of shale distribution. An
inversion result proves that there is presence of Shaly sands and porosity also tends to
decrease in the south east direction. The average porosity value evaluated with model based
inversion and band limited inversion is 8% and 7%.
