SEISMIC FACIES ANALYSIS WITHIN A SYSTEM OF STRATIGRAPHIC FRAMEWORK

ABSTRACT

A seismic facies analysis within a system of stratigraphic framework was carried out in an oil field in the Niger Delta to identify the relationship between seismic facies of stratigraphic units, reservoir and non-reservoir sands that could lead to the discovery of cost effective potential oil and gas reserves in the country’s most productive basin, the Niger Delta. The 3D seismic data of the field was loaded, quality controlled and assured to ascertain the quality of the data. The faults in the field were interpreted after which seismic to well tie was carried out to get a time to depth ratio that will enable the accurate movement of the 14 drilled wells to seismic. Chronostratigraphic ages and associated system tracts were delineated on the seismic with the aid of the Niger Delta chronostratigraphic chart, well logs and available literature. Seismic facies distribution within the system tracts was studied. The facies of reservoir and non-reservoir sands were also studied to ascertain similarities and dissimilarities.

Three sequence boundaries 10.6 Ma, 10.35 Ma and 8.5 Ma and their Maximum Flooding Surfaces (MFS) 11.5 Ma (Dodo shale), 10.4 Ma (Nonion-4) and 9.5 Ma (Uvigerina-8) within the Coastal Swamp depobelt of the Niger Delta were identified. Their respective system tracts of Lowstand, Transgressive, Highstand and Falling Stage were delineated and their seismic facies studied along with the seismic facies of reservoir and non-reservoir sands. It was seen that the system tracts, reservoir and non-reservoir sands can be found in any type of seismic facies. The Lowstand, Trangressive and Highstand system tracts of 10.4 Ma MFS and below offer good potential for oil and gas reserves.