Computer Processed Interpretation of Geophysical Logs of an Oil Field Niger Delta Sedimentary Basin, Onshore, Nigeria
L. I. Nwosu *
Department of Physics, University of Port Harcourt, Nigeria
G. O. Emujakporue
Department of Physics, University of Port Harcourt, Nigeria
*Author to whom correspondence should be addressed.
Abstract
The computer processed log interpretation allows analysing and evaluating numerous types of logs with ease and presenting the results as functions of depth in graphical forms for visualisation. Computer processed interpretation of geophysical logs from five deep oil wells has been carried out for Niger Delta Sedimentary Basin. The composite wire line logs consisting of gamma ray, resistivity, density and neutron have been used for the study. The qualitative interpretation of the gamma ray log showed alternation of sandstone and shale lithologies which is an indication that the interval logged is within Agbada Formation of the Niger Delta. Four reservoirs were delineated and correlated across the five oil wells. The density and neutron logs were used for differentiating the hydrocarbon fluid into oil and gas. The delineated reservoirs were labelled as R1, R2, R3 and R4. The R1 is a gas bearing reservoir while R2, R3 and R4 reservoirs are oil bearing. The results of the formation evaluation showed that porosity and water saturation of the reservoirs range from 19.0 to 22.7 percent and 0.19 to 0.286 respectively. The computed permeability ranges from 516 to 1662 milliDarcy (mD). The Net to Gross ratio for the four reservoirs ranges from 0.844 to 0.947. The computed values of the porosity, water saturation, Net to Gross ratio and permeability show that the four reservoirs have good to excellent quality.
Keywords: Computer processed interpretation, geophysical logs, porosity, water saturation, Niger Delta