Electronic Theses and Dissertation

Cekungan Sumatera Tengah merupakan salah satu cekungan migas paling produktif di Indonesia dengan karakteristik geologi yang kompleks dan sistem petroleum yang lengkap. Namun, interpretasi zona prospek hidrokarbon di wilayah ini masih memerlukan pendekatan yang lebih akurat guna meningkatkan efisiensi eksplorasi. Penelitian ini bertujuan untuk menentukan zona prospek hidrokarbon di sumur NAB yang terletak di Cekungan Sumatera Tengah dengan memanfaatkan data open hole logging. Data log yang digunakan dalam penelitian ini meliputi log gamma ray, resistivitas, densitas, dan neutron dari dua sumur (NAB-1 dan NAB-2). Metode analisis dilakukan secara kualitatif dan kuantitatif dengan bantuan perangkat lunak Geolog 7.0. Evaluasi dilakukan untuk mengidentifikasi parameter petrofisika seperti volume shale, porositas efektif, dan saturasi air guna mengenali zona-zona yang berpotensi mengandung hidrokarbon. Hasil analisis menunjukkan bahwa pada sumur NAB-1, zona prospek utama terletak pada interval kedalaman 646–668 ft dengan karakteristik gamma ray 100 Ωm, porositas efektif sekitar 21–22%, dan saturasi air

The Central Sumatra Basin is one of the most productive hydrocarbon basins in Indonesia, characterized by complex geological features and a well-developed petroleum system. However, the interpretation of hydrocarbon prospect zones in this area still requires more accurate approaches to enhance exploration efficiency. This study aims to determine hydrocarbon prospect zones in the NAB wells located in the Central Sumatra Basin using open hole logging data. The log data utilized in this research include gamma ray, resistivity, density, and neutron logs from two wells (NAB-1 and NAB-2). The analysis was conducted both qualitatively and quantitatively with the aid of Geolog 7.0 software. The evaluation focused on identifying petrophysical parameters such as volume shale, effective porosity, and water saturation to recognize zones with hydrocarbon potential. The results indicate that in well NAB-1, the main prospective zone is located at a depth interval of 646–668 ft, characterized by a gamma ray value of less than 50 gAPI, resistivity greater than 100 Ωm, effective porosity around 21–22%, and water saturation below 50%, indicating the presence of gas and oil. In well NAB-2, the prospective zone was identified at a depth interval of 316–407 ft, with effective porosity of 23% and water saturation ranging from 28–69%, suggesting possible hydrocarbon accumulation within cleansand lithology. The presence of crossover between neutron and density logs further strengthens the interpretation of hydrocarbon presence. The benefit of this study is to provide a more accurate interpretive basis for identifying hydrocarbon prospect zones using well log data, thus improving exploration efficiency and serving as a methodological reference for similar studies in other basins. These findings are expected to support field development planning and enhance more targeted exploration strategies. Keywords: Hydrocarbon, Open Hole Logging, Prospect Zone, Well Log, Porosity, Resistivity