2-D Seismic Data Interpretation of Qadirpur Area, Pakistan

Abstract

Aim of the study is to interpret 2D-Seismic Reflection time section of the Qadirpur Area (Sindh Province) Pakistan. This seismic section is a Pre-stacked time migrated section and was provided by the Department of Earth Sciences, Bahria University Islamabad and this line bears the title 985-QPR-03 It is about 40 Kms in length and is oriented in SW-NE direction. OGDC acquired data in October 1998 and processed it in January 1999. The velocity information is in the form of RMS. DIX interval and DIX average at different times is given, and is provided at selected S.P. RMS velocity varies from 1500 m/s to 5000 m/s Interpreted part of this line from S.P. # 460 to S.P # 720, with CDPs from 920 to 1440 Length of this part of seismic section is 13 Kms. For interpretation of this part of Seismic section, four reflectors and 2 faults are marked on the basis of prominent reflections from subsurface horizons due to changes in lithology and diffractions. Using the RMS velocity given in the velocity panels on seismic section for selected shot points, calculate the time on constant velocity interval of 100m/sec Then using these calculated time and velocity values prepare the Iso-velocity graph and Iso-time graph (for mean line method) by taking constant velocity and time respectively, In Mean line Method of velocity estimation, a velocity vs time graph is prepared. From this graph, a mean average velocity is determined. From Seismic Section, arrival times (two ways) of each marked reflector are determined, Using these arrival times, Time Section is prepared. Also using these arrival times, calculate the average velocity for these times on mean line graph and then the depth of each reflector has been calculated using s(vt)/2 and is represented in Depth Section. Depth Section provides a reliable picture of reflectors and structures present in the subsurface of the area. Well correlation is also done, which satisfy the calculated depths, so horizons have been marked Interpretation of the Project Area shows that, extensional regime and calm environment prevails in the area. Reflectors are almost flat-lying, whereas Horst and Graben structures have been found.