Rock Quality Prediction Using Crossplots and Seismic Lithology Inversion: An Example of XIN Field, Eastern Niger Delta Basin
Understanding subsurface reservoir sand quality, continuity and distribution is very important for optimum production of hydrocarbons in the Niger Delta region. Reservoir sand continuity across shelf regions of the Niger Delta Basin can be extremely complex and require techniques such as elastic attributes crossplots and seismic simultaneous inversion modeling in order to understand and unravel the depositional processes, sand distribution and quality variations. This study was aimed at achieving minimum error in the prediction of H-sand quality and continuity across the XIN field of Eastern Niger Delta with the specific objective of minimizing uncertainties associated with reservoir sand quality prediction during the search for hydrocarbons and infill drilling for optimum production. The study adopted elastic attribute crossplots and simultaneous inversion of Lithology Impedance to predict H-sand lateral continuity, distributions and quality across the XIN field. Analysis of Lithology Impedance results from log and simultaneous inversion showed that values greater than -100 ft/s*g/cc represent shale facies while values less than -500 ft/s*g/cc represent sand facies. The heterolithic lithofacies comprising of sandy-shale and shaly-sand units were also found to possess variable values of Lithology Impedance between -100 ft/s*g/cc to -500 ft/s*g/cc. The result of crossplots and seismic inversion of Lithology Impedance and porosity confirmed that the reservoir quality of the ‘H-sand’ increases with decreasing Lithology Impedance and increasing porosity. This technique was applied successfully to clearly determine reservoir quality variations and continuity in the XIN field, a major requirement for accurate location of infill wells and for maximizing production.
AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017