IDENTIFICATION OF AVO ATTRIBUTE RESPONSE TO THE PRESENCE OF CO2 CONTENT USING AVO MODELLING METHOD IN LOWER TALANG AKAR FORMATION (LTAF), SOUTH SUMATRA BASIN

Abstract

The research area is an oil and gas field that is currently undergoing development, located in the South Sumatra Basin. Coal content, particularly within the Lower Talang Akar Formation (LTAF) interval, is frequently encountered in this field, with coal serving as the source of in-situ CO2 content formation. Consequently, CO2 content can be identified using the Amplitude Versus Offset (AVO) analysis method, allowing an assessment of its influence on the percentage presence of CO2. The data used in this study consist of well data, including log data (Density, Porosity, Vp & Vs Sonic/DT), Drill Stem Test (DST) data, well marker data resulting from stratigraphic sequence interpretation, and well reports. The AVO method to be employed encompasses a wide-angle range, approximately 0°-45°. The results obtained from this research using the AVO method, after AVO modelling on well data, indicate that the dominant AVO response within the LTAF interval is class 4 AVO. AVO analysis results regarding AVO presence indicate that reservoir intervals containing CO2 content will exhibit a class 4 AVO response, and an increase in fluid content percentage will result in a more positive intercept and a more negative gradient (towards class 2 AVO). In terms of facies and depth variations, the AVO attribute response consistently demonstrates an increase in intercept and a decrease in gradient with rising CO2 levels.