The Use Of Seismic Velocities For The Prediction Of Abnormal Pressures: A Case Study Onshore Niger Delta, Nigeria.

Abstract

Ninety (90) velocity control points derived from seismic data processing were examined and analyzed to evaluate abnormal pressure zones in parts of onshore western Niger - Delta. Compaction trend graphs and a map showing the distribution of top of overpressure were produced. The graphs show that compaction increases with depth and deviation from normal trend lines connote overpressured zones. The depth range at which overpressure was encountered is from 1000m to 4500m. The magnitude of interval transit times derived from seismic data was used for the calibration of the subsurface into minimum (750μs/m), normal (613μs/m) and mixed (528μs/m) compaction zones. A map depicting the distribution of depths to the top of abnormal pressure also complemented the compaction trend graphs. The depth to the top varies within the study area and has a range of 2000m to 4000m. This study is relevant in predicting overpressure zones, which will serve as an asset to the petroleum industry during drilling of deep wells for oil exploration and exploitation.

Key words: Seismic, velocity control, overpressure, abnormal pressure

Nig. J. of Pure & Appl. Physics Vol.3 2004: 64-67