Abstract:
The research area for the Zamzama gas field is located in Sindh's Dadu district,
within the Zamzama block. The investigation region lies in Pakistan's Southern Indus
basin's Kirthar foredeep. The geologic succession ranges from Jurassic to modern
times. The Zamzama structure is a massive north-south thrusting anticline with an
eastward trending. To interpret its structure and tectonic regime, seismic and borehole
data are presented. The general geology, stratigraphy, and tectonics of the area is
thoroughly investigated in order to better comprehend the tectonic evolution since
Pangea's formation. Two horizons of interest are marked, and no fault is encountered
in the given 3D seismic cube, then interpreted to determine the depth, extension, and
orientation of subsurface structure. The petrophysical analysis is run to investigate
reservoir formation in order to determine rock type and hydrocarbon potential.
Different logs, such as LLS and LLD form various cross overs, indicating the presence
of fluid in porous and permeable rocks. Porosities, shale volume, water saturation, and
hydrocarbon saturation are estimated, indicating that the reservoir rock has sufficient
conventional reservoir rock potential for oil and gas production. Seismic post stack
inversion is applied on a seismic line integrated with well data to understand the
reservoir response on large scale. Model-based inversion is used which shows the low
impedance at the depth of reservoir indicating presence of porous and permeable rock.
Rock physics modeling is performed to distinguish the facies by plotting
different cross plots between various rock parameters. Hence, Zamzama is a potential
gas-producing field in the lower Indus basin, where the Pab sandstone in Zamzama -
03 is a producing field. Bayesian classification is run on 3D seismic data cube to predict
the lithologies and fluid present in the reservoir. For Bayesian classification different
cross plots are used for the prediction of lithology and fluid, with density plotted on Z
axis. The cross-plots clearly separated and delineated the Litho-fluid classes
(hydrocarbon sand, gas sand, and brine sand) with specific orientation/patterns.
