Core-log Data Integration for Improved Formation Evaluation in the Dulang Field, Offshore Peninsular Malaysia

ABSTRACT One of the most challenging tasks of a log analyst is to understand log responses. In order to achieve this it is essential to establish an accurate Bulk Volume Model for the reservoir. This includes mineralogy, porosity and saturations. Unfortunately, in the case of Dulang field, log data alone cannot be used to derive accurately the Bulk Volume Model due to insufficient log data and the presence of special minerals. These minerals which affect log responses significantly are Potassium-Feldspar, Siderite and Fe-Dolomite. Dulang field is a complex shaly-sand reservoir situated 130 kilometres offshore Peninsula Malaysia. This paper illustrates how results of core analysis have helped us understand log responses in the Dulang field. A special core recovery program was carried Out in three wells, namely, Dulang-A17, B20 and B21, which penetrated all the major reservoirs that contributed the bulk volume of STOIIP in the Dulang field. A low toxicity oil-based mud was used in well Dulang-B21 to establish accurately the connate water saturation for quantitative calibration of log derived parameters. A bland water-based mud was used in the other two wells to preserve the rock wettability. The results of the core analysis enabled us to better refine our petrophysical model of the reservoir which led to a more accurate computation of reserves. Components of core analysis used in this study are Fourier Transform Infra-Red spectroscopy, Core Layering and conventional core measured petrophysical parameters (porosity, permeability, grain density and saturations).