C. Shafe Alexander1,
Laura E. Maley1,
(1) BP Amoco, Houston, TX
(2) Sonangol, Luanda, Angola
(3) Shell Angola, The Hague, Netherlands
Abstract: The Plutonio discovery, Block 18, Angola - A 3D visualization and multi-attribute approach to exploration success
3D seismic visualization and multi-attribute analysis have revolutionized petroleum exploration. These interpretation tools have been applied to exploration in Block 18 Angola to reduce exploration risks and cycle time.
Blockwide 3D coverage (5300 sq. km) was acquired in 1996 and 1997. Full-, near-, far-offset, and AVO volumes were generated. These were interpreted using visualization hardware and software capable of handling multi-gigabyte data volumes.
The Plutonio discovery is located on a large turtle structure initially identified during first pass structural mapping. An amalgamated channel system with associated sheet facies was identified as potentially hydrocarbon bearing based on the far-offset amplitude response. Rock property trend data indicated that oil should produce a positive AVO response. A comparison of near and far volumes supported the rock property model, and the area of positive AVO conformed to structure. A flat event was identified using visualization. Voxel picking the flat event defined complex channel geometries, which were used to constrain n optimal traverse down the main channel axis. Flat spot enhancement along this traverse confirmed the presence of a robust, continuous flat event.
The Plutonio well was located using geological and geophysical criteria, including positive AVO, differential compaction, and the flat event. Well results indicate that: positive AVO was a highly accurate predictor of pay, differential compaction indicated sand, and the flat event was an Oil Water Contact. Future work with calibrated AVO data, well control, and seismic-based geologic models should improve accuracy in predicting net-to-gross, connectivity, and drainage issues during appraisal and development.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana