OVERPRESSURE ESTIMATION AND ITS GENERATING MECHANISM USING WIRELINE LOG AT CLUSTER A AREA, NORTH SUMATRA BASIN.

• Main Author: Mudastsir, Riyan
• Format: Theses
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/57820
• Institution: Institut Teknologi Bandung

Cluster A is located in northern part of the North Sumatra Basin. This study is conducted based on indications of overpressure from regional geology, drilling reports, and previous study in the study area and its surrounding. The objective of this study is to estimate pore pressure using Eaton’s method and to determine its gemerating mechanism in well R and Y. The data used consists of wireline logs, i.e., sonik and density logs, and drilling data consist of drilling event, mudweight, formation pressure, drilling rate, and leak-off test. Based on the result obtained, the overpressure is first found at Baong Formation with the pressure up to 3200 psi in well R and 7000 psi in well Y. The overpressure occurrence is associated with the increasing mudweight, deflection of the sonik log, and drilling events such as stuck pipe, tight hole, and kick. The effective stress on the pressure-depth plot and wireline logs response show that the overpressure generating mechanism in the study area is unloading due to smectite to illite transformation. To obtain the representative result, Eaton’s exponent used is 0.9 in well R and 0.6 in well Y.