Porosity and compaction trend in Okan field (Western Niger Delta) based on well log data.

Abstract

Porosity and compaction trends in Okan Field have been highlighted based on the interpretation of well log data within the productive interval of 5000 to 10,000 ft. Six Porosity Zones have been delineated based on the interpretation of gamma – ray log from the representative wells. The zones that occurred between 5000 ft. and 8000 ft. appeared to be tectonically controlled whereas the deeper zones result mainly from diagenetic changes associated with the burial history of the sediments. Regionally, these zones represent from bottom to top, cyclic deposition of clays and sands which become increasingly sandy upward through the sequence. Porosity values are in the range of 15 and 25% and this is good enough to enhance hydrocarbon accumulation in the area. Sedimentation pattern is normal in most parts of the field except for a local zone of overpressure observed at a depth of 8300 ft. in the northeastern section of the field. The main hydrocarbon trap results from vertical stacking of porous reservoirs sands while the stratigraphic trap is evident from reservoir Pinchouts.

Global Journal of Pure and Applied Sciences Volume , No 1 January (2001) pp. 91-96



KEY WORDS:

Porosity, Reservoir, Sedimentation, Overpressure, Hydrocarbon.