Petrophysical and Sensitivity Analysis for Reservoir Characterization of Nias Basin, North Sumatra
Maulina (a*), Tumpal B. Nainggolan (b)
a) University of Lampung, Lampung
*maulln197[at]gmail.com
b) Marine Geological Institute, Bandung
Abstract
Petrophysical analysis of well log data have been crucial for determination of reservoir prospect zone with lithology and hydrocarbon types based on petrophysical parameters. In addition, sensitivity analysis is carried out to determine elastic parameters that are sensitive of lithology variability and pore-fluid type. Based on the crossplot results, parameters such as Lambda-Rho, Mu-Rho, and VpVs ratio can detect lithology and pore-fluid types because they are sensitive to porosity and rock matrix characteristics. This study focuses on reservoir characterization of ‘MS- well on Late-Miocene N17 rock formation which was classified as a shelf carbonate matrix. The petrophysical parameters are carried out such as porosity ( ), water saturation (Sw), shale content (Vshale), and formation water resistivity (Rw) using density and neutron logs calculation, Indonesian-s equation, and qualitative analysis approcach. Based on the results of petrophysical analysis it is known that the reservoir zone is at 5003-5297 ft with total thickness 101 ft netpay. The reservoir has a limestone lithology with Gamma Ray-s value between 15-55 API. The hydrocarbon prospect zone is indicated by the separation of NPHI and RHOB curves with low value, porosity 18.5%, water saturation 37%, and water resistivity shows 0.12-0.13. The reservoir zone is indicated by the cut-off of Lambda-Rho <25 GPa*gr/cc, Mu-Rho <70 GPa*gr/cc, and VpVs ratio <2. Finally, both the petrophysical and sensitivity analysis show indication of fresh water biogenic gas reservoir.
Keywords: petrophysical and sensitivity analysis; reservoir characterization; lithology; carbonate; Nias basin
Topic: Geophysics,Geomatics and Geochemistry