Abstract:
The area under study is Sawan Gas Field which was discovered in 1998 by
OMV (Pakistan) Exploration. Geographically the area lies in Thar Desert, Khairpur
District Sind province of Pakistan. Geologically Sawan field lies on the southeastern
flank of the Khairpur High which is considered as platform slope area in Middle Indus
Basin. The area is characterized by normal faulting with strike slip component, with
structural trap and bright spot anomaly with small four way dip closure structure.
Seismic interpretation involves identification of major horizons, faults, and trap in
study area.
Lower Goru “C” sand interval sand having shallow marine depositional
environment and restricted to the northeast–southwest trending fairway. Low
impedance sandstone always difficult to image. Seismic inversion and AVO
modelling study is carried out in this research to tackle this problem. Seismic
inversion converts seismic amplitudes into acoustic impedance which enable us to
identify low impedance individual sand packages. Model based inversion is
performed and it start with an initial guess of impedance model. Initial model usually
comes from wells and extrapolated away from well using horizons. The key to using
AVO identification is comparison of real with a standard in this case, modelled AVO
response. This is an artificial trace manufactured by assuming that some pulse through
an earth model containing rock layers of given thicknesses, velocities and densities
and returns to be recorded.
