Bright Spot Validation from 3-D Seismic Data: A Study of Naso-Field, Niger Delta Province, Nigeria

Abstract

Onyemenam I, Ugwu SA and Nwankwoala HO

The validation of identified bright-spots A, B and C on 3D seismic data as Direct Hydrocarbon Indicator (DHI) in Naso field, Niger Delta was achieved through the integration of four surface attributes. These attributes include root mean square, average reflection strength, total energy, and total amplitude which are all amplitude dependent, where region of high value in every attribute indicated possible hydrocarbon prospects. Seismic data and check-shot data were used, which provided positive input for velocity extraction and structural mapping interpretation. A series of NW-SE trending normal growth faults A, B & C were interpreted defining the reservoir structural framework while fault D, E, F & G are post-depositional minor faults which also supported the trapping mechanism. Bright-spot A was mapped between 2,400-2550 milliseconds, while bright-spot B was mapped between 2,600-2,720 milliseconds and bright-spot C between 2,750-3,050 milliseconds. Two hydrocarbon prospects were identified. Prospect-1 was estimated to cover about 907.17, 1323.59 and 1075.44 acres, with subsurface total vertical depth of 9514.3ft, 10499.6ft, 10963ft in BS_A, B & C respectively. Prospect-2 covered about 653.49, 1080.33 and 493.77 acres with subsurface total vertical depth of 8650ft, 9525ft, and 10120ft, respectively. Hence, prospect-1 is considerably more prolific in hydrocarbon yield than prospect-2. The total area of the hydrocarbon prospects in-place has been estimated to about 5,533.79 acres which is likely to yield a prolific reserve for commercial purpose. The gas Chimney and push down highlight the subsurface leakage of gas from a poorly sealed cap rock and show a deep petroleum migration process. The study has been able to validate bright spot during exploration studies in effect to evaluate hydrocarbon reservoir, prospect identification and reservoir prediction.

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