THE ANALYSIS OF OVERPRESSURE CHARACTERISTIC IN SAHARAN FIELD, GHADAMES BASIN, EAST ALGERIA

• Main Author: Rahmi Chan, Aulia
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/53042
• Institution: Institut Teknologi Bandung

Saharan Field is located in Ghadames Basin that is a large intracratonic basin in Northern Algeria. The lithologies in Saharan Field are dominated by fine-grained and evaporite rocks which exhibit impermeable characteristic. These deposits will tend to form a closed system that will prevent the pore fluid from escaping from the pore resulting overpressure generation. The drilling process on this field can found some obstacles, such as the occurrences of blowout, kick and loss when it is carried out in the overpressure zone. If overpressure is not well estimated, technical and financial losses can be large when production is carried out. The aim of this study are to determine top overpressure, estimate pore pressure magnitude, analyse overpressure generating mechanisms, and analyse the relationship between geological condition in study area and overpressure. The research were performed in four wells (ARC-1, ARC-2, ARC-4, ARD-9) by using wireline log data, well report, temperature data, and pressure data. Based on the result, there are two pore pressure patterns in the study area, i. e. hydrostatic zone and overpressure zone with loading and lateral drainage mechanism. The overpressure zone in the Saharan Field is reached from a depth of 2400 - 3200 TVDSS which are found at the claystone, anhydrite and halite intervals of the Lias Salifer Formation untill TAG-I Formation. The magnitude of pore pressure in the overpressure zone ranges from 3800-5980 psi. Lateral drainage occurs in the TAG-S Formation which causes a decrease in pore pressure to near hydrostatic pressure.