RESERVOIR CHARACTERIZATION AND RESERVE ESTIMATION OF “AFONJA” FIELD, NIGER DELTA, USING WELL LOGS AND 3-D SEISMIC DATA

Abstract

The aim of this research is to characterize the reservoirs and estimate the hydrocarbon reserve of “Afonja” field, Niger delta using well logs and 3-D seismic data. Suite of well logs for six wells which comprises of gamma ray, resistivity, neutron, density and sonic logs, 3D seismic data and checkshot data were analysed with Petrel software for this study. The research methodology adopted involves delineation of lithologies and identification of reservoirs from well logs, well correlation, determination of petrophysical parameters, well seismic tie, horizon and fault mapping, time to depth conversion and reserve estimation. Five hydrocarbon reservoirs R1, R2, R3, R4 and R5, respectively, were revealed from well log analysis. Petrophysical parameters were evaluated with the gross thickness ranging from 13 m to 60 m, the Net / Gross ranges from 0.73 to 1.00, effective porosity ranges from 0.29 to 0.42, hydrocarbon saturation ranges from 0.52 to 0.94 and volume of shale ranges from 0.02 to 0.14. Wells were tied to seismic using both checkshot data and generated synthetic seismogram, faults were picked and the top of reservoirs mapped and were converted into depth structure maps. The reservoirs area extent has a range 1977-2965 acres across the field.Estimated gas initially in place (GIIP) was 483 billion standard cubic feet (SCF) and 60% recoverable gas reserve was 290 billion standard cubic feet (SCF). Similarly, estimated stock tank original oil in place (STOOIP) was 970 million stock tank barrel (STB) and 35% recoverable oil reserve was 339 million stock tank barrel (STB) oil.