Hydrocarbon reservoir characterization and discrimination using well-logs over “AIB-EX” Oil Field, Niger Delta

A computerized advanced statistical analysis which involves the characterization of reservoir elements involving mapping of lithofacies and pore fluids through crossplots of basic seismic variables in both bi-variate and tri-variate domains and functional transformations including rotation of axes have been used as discriminant tools over “AIB-EX” Oil Field, Niger Delta. The methodology encompasses reconstruction of geologic lithofacies information from geophysical logs. Reservoir characterization, rock physics analysis and log inversion were carried out using IHS Kingdom Advanced and Origin software. Three reservoir zones namely A, B, and C were analyzed. The obtained results characterized the reservoir elements as: shale, sandy-shale, shaly-sand and sand (with respective GR counts and P-wave velocity of 105–125 API and 2400–3600 m/s, 75–105 API and 2100–5000 m/s, 45–75 API and 2200–4750 m/s, and 10–45 API and 2000–4600 m/s) which represents seismic scale sedimentary units called lithofacies. Also, the results of both the bi-variate crossplots (GR and P-wave velocity) and tri-variate crossplots (GR, P-wave velocity, and resistivity) have not only differentiated the different lithology but have discriminated the saturating fluid (water or hydrocarbon). The pore fluids were further characterized as either brine or oil based on powerful discriminant tools such as plots of acoustic impedance versus porosity and elastic impedance versus porosity. Conclusively, the result of the research confirmed that hydrocarbon reservoirs can be discriminated with varying degree of effectiveness in various domains using the adopted approach. The obtained result, which can also be used to calibrate seismic inversion, yielded a reliable seismic lithofacies map in the presence of high resolution 3-D seismic data.