Abstract:
The basic objective of research is to get preliminary understanding of the
subsurface structural trend and reservoir characterization of study area. Reservoir
characterization is a process of describing various reservoir properties using all the
available data to provide reliable reservoir models for accurate reservoir performance
prediction. Gambat block lies in lower Indus basin which is an extensional regime
resulting extensive horst and graben geometry that may be considered as hydrocarbon
bearing zone. The producing reservoirs in this area of Lower Goru Formation are shallow
marine sandstones. This research aimed to find and locate such prospects in the sand of
Lower Goru Formation in Gambat area. Four reflectors namely Lower Goru, A interval,
B interval and C interval were marked on seismic sections on the basis of depth and
velocity of these depth and time contour maps of selective horizons were prepared to see
the depth variation of these reflectors in the study area. Petrophysical analysis was done
to evaluate the properties of reservoir (effective porosity, hydrocarbon saturation and net
pay) for prospect zone in Tajjal wells. Gassmann Fluid Substitution analysis provides
information about impact of depleting reservoir on seismic properties. Low impedance
sand is difficult to image, AVO modeling carried out in this research to tackle this
problem. Horst and graben structures were marked on seismic data along with probably
stratigraphic traps which contains gas bearing sand as confirmed by petrophysical
analysis and AVO modeling. These studies nominate Tajjal structure as a probable
prospect for future exploration.
