THE ANALYSIS OF OVERPRESSURE CHARACTERISTIC IN NWY FIELD, TARAKAN BASIN, NORTH KALIMANTAN

• Main Author: Adriandi, Febri
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi ekonomi
• Online Access: https://digilib.itb.ac.id/gdl/view/34393
• Institution: Institut Teknologi Bandung

The study is located in the NWY Field, Tarakan Basin, North Kalimantan, operated by PT. JOB Pertamina-Medco E&P Simenggaris. The stratigraphy of the NWY Field is divided into five formations, i.e. Tarakan, Santul, Tabul, Meliat, and Naintupo. The study is performed in these five formations which are Early Miocene – Pliocene in age. The purpose of this study is to estimate pore pressure, determine top of overpressure, analyse overpressure generating mechanism, and analyse the relationship between overpressure and geological condition in the study area. The analyses were performed in 7 drilling wells using wireline log data, mudlog data, formation pressure, temperature, well report, and vitrinite reflectance. The characteristic of overpressure is observed from the profile of stress/pressure and response of wireline log to depth. The result of the analysis shows that three out of seven wells penetrate overpressure zone. The top of overpressure ranges from 4700-9100 ft TVDSS, with the magnitude of overpressure around 2200-6100 psi. The distribution of top of overpressure relatively follows the top of Naintupo Formation. The overpressure generating mechanism is loading mechanism. Loading mechanism is caused by high rate of sedimentation, in the range of 117-686 m/million year. However, there is a possibility of limited contribution of non-loading mechanism due to clay diagenesis.