2-0 SEISMIC REFLECTION DATA INTERPRETATION OF MlANWALl AREA "PAKISTAN"

Abstract

Oil & Gas Development Corporation (OGDC) carried out seismic reflection survey in East Mianwali and a processed seismic time section was provided. This dissertation pertains to the interpretation of seismic time section in term of average velocity variations with time and depth. Three reflectors named as (R I, R2 and R3) have been marked on the seismic time section on the basis of observed reflection events. For the depth calculation two methods namely Dix average velocity method and velocity function method have been used. In the Dix average velocity method, the velocity and depth of the reflectors were calculated; iso-velocity map and depth section were prepared using Dix average velocities, in the iso-velocity map lateral and vertical velocity variations can be observed. While in the veloc ity function method a velocity function was obtained by plotting the given CDP data and depth section was prepared by usi ng this velocity function. The depth section shows that the area is structurally deformed due to tectonic forces and salt uplifting, therefore reverse faults are present there and reflectors are not horizontal through out the line. There is an abrupt change in the velocity at CDP 850, which may be due to compaction. On the basis of Dix interval velocity assigning a velocity of < 4000m/sec to clastic rocks and > 4000mlsec to non-clastic rocks, the strata can be divided into clastic and non-clastic zone