Determination of Interval Depth of Subsurface Layers by Velocity Analysis of Seismic Reflection Data, in Part of Niger Delta Basin, Nigeria

Abstract

Seismic reflection data obtained from 3 – D survey in part of the Niger delta basin, Nigeria was processed using Velocity Computation (VELCOM), an interactive velocity analysis interpretation program. The application uses the principle of Apparent Velocity Picking, Normal Moveout (NMO) Correction and Stacking. Velocity intervals and stacking velocity for 8 Common Depth Points (CDPs) were obtained. Interval velocity ranges between 1814 - 5579 ms^-1 and Stacking velocity (V_s) ranges between 1814 – 3639 ms^-1. Both velocities increase with depth, with interval velocity more steeply than Stacking velocity within the same interval depth. The corresponding depths to the reflecting surfaces, ranging from 554 – 10033m, were obtained, which led to the interval depths of layers ranging from 31 – 1180m. The result of this velocity analysis can be applied in NMO correction, calculating depths from reflection times, horizons identifications, the recognitions of lithology, detection of high pressure zone and migration.

Keywords: Seismic reflection, Normal move -out, Velocity, Depth of layer