The purpose of this paper is to compartmentalize the rock units that make up the reservoir into different compartments to identify units with hydrocarbon potential. Niger Delta Basin is a rift basin characterised with complex geological structures and lithological heterogeneity, thereby demanding careful and systematic approach for successful results. Integrated seismic attribute studies provide the needed platform for compartmentalizing the various reservoir units for optimum hydrocarbon production.
Attributes such as Extract Value (the raw amplitude of input seismic), Arc Length, Average Magnitude, Root Mean Square (RMS), Average Energy, Maximum Amplitude, Half Energy, Positive to Negative Ratio and Sum of Magnitudes were adopted to study the reservoirs for the purpose of understanding the interplay of all the elements of petroleum system. These attributes were derived through various mathematical and statistical manipulations on the seismic amplitude and each were linked to specific reservoir petrophysical parameters such as fluid content, porosity, thickness and sand/shale content. To resolve ambiguities in the interpretation of results, more than one attribute were used for single rock properties in order to address the problem of attribute limitation and interpretation ambiguities.
The result revealed different reservoir compartments with/without hydrocarbon and lithologic heterogeneity indicating that reservoir properties are not the same throughout the zone. Regions with high attribute values above the background level were interpreted as complex geological structures hosting hydrocarbon especially when they are in conformity with structures capable of habouring hydrocarbon. Further, the material parameters relating to changes in porosity, thickness and net-to-sand ratio were delineated using different seismic attribute maps. Understanding factors controlling reservoir compartmentalization is critical for identifying optimum well location and for executing secondary recovery of hydrocarbon in complex reservoirs.
The originality lies in the ability of the work to identify and recommend the most appropriate attributes for a specific reservoir property for the study of reservoir compartmentalization as most of the published studies did not use most of the attributes, or compare them with each other. The study applied at least two attributes to a particular reservoir property to reduce uncertainties in the results and to illustrate how one rock property may account for multiple seismic attribute changes. Therefore, the study concluded that integrating several attributes of significance are crucial tools for compartmentalizing reservoir units in the Niger Delta Basin and any other basin around the world.
