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Facies Interpretation from Well Logs: Applied to SMEKS Field, Offshore Western Niger Delta

Odundun, Olumuyiwa; Nton, Matthew
Geology, University of Ibadan, Ibadan, Nigeria.

The Niger Delta basin has spectacularly maintained a thick sedimentary apron and salient petroleum geological features favorable for petroleum accumulation from the onshore through the continental shelf and to the deepwater terrains. The onshore and continental shelf Niger Delta are being explored for more than half a century now. However, exploration activities are gradually being shifted to the deep offshore to unveil its hydrocarbon potential. The deep sea channel sands are the main exploration target in this section of the Niger Delta. The study aims at using well log approach in establishing the sedimentary facies, their successions and environments of deposition in the SMEKS Field, offshore western Niger Delta. Also carried out was a well to well correlation and determination of the quality of the reservoirs detected.

The sedimentary facies in the study area was determined by interpreting data from well logs; gamma ray, effective porosity and resistivity logs obtained from four wells.

The environments of deposition in the field were deduced by combining the gamma ray log trends with core data. This lead to the recognition of four log facies: Irregular log trends representing deep marine clay; a funnel-shaped facies representing a crevasse splay; a cylindrical-shaped facies representing slope channel-fills and turbidite fans, and a bell-shaped facies representing transgressive marine shelf.

Four reservoir bodies were discovered in the field. Sand bodies are 50 m thick or less and are characteristically poorly sorted to well sorted, fine clayey sands-with some conglomerate and shale pebbles. A qualitative reservoir evaluation shows that porosity values range from 20 to 37% while the permeability range from 524 to 9600 md. The porosity and permeability are better developed in areas of sand bodies deposited in the slope channel environment.

The results show the good hydrocarbon bearing potential of the deep sea channel sands coupled with the complex fault system of which the distal Niger Delta province is associated.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012