Petrophysical Calculation Analysis and Determination of Cut-Off in Betung Field, Jambi-Sub-Basin, South-Sumatera-Basin

Abstract

Petrophysical properties provide a comprehensive approach to reservoir characterization, in which reservoir quality is of paramount importance. The main controllers for reservoir quality are porosity, permeability and clay content. Petrophysical models are used by utilizing the correlation between tool response (logging) and rock and fluid properties. These petrophysical results will be cut-off to distinguish productive and unproductive parts of a reservoir. Petrophysical and cut-off calculations in the Betung Field are applied to determine the quality and productive zone of the Air Benakat Formation reservoir. The direction of field development (infill wells) is based on the quality of the reservoir and productive zone obtained based on the results of petrophysical and cut-off calculations. This research was conducted in Layer 5 (L-5) of the Betung Field using the main data, namely well logs (Gamma ray, density, neutron, resistivity). Well logs were processed to obtain petrophysical values using Interactive Petrophysic and Microsoft Excel software. Petrophysical results were then cut-off on clay content, porosity and water saturation, so that a productive zone was obtained from the Betung L-5 field. Petrophysical and cut-off results show L-5 is a Hydrocarbon prospect zone with an average petrophysic value for well 210 (Vclay: 32%, porosity: 25% and water saturation: 65%); well 220 (Vclay: 35%, porosity: 30% and water saturation: 38%); well 222 (Vclay: 8.2%, porosity: 31% and water saturation: 28%). The resulting cut-off values for well 210 (Vclay: 42.6%, porosity: 17% and water saturation: 98%); well 220 (Vclay: 26.6%, porosity: 22.4% and water saturation: 50.3%); well 222 (Vclay: 18%, porosity: 17% and water saturation: 70.4%).