FRACTURE CHARACTERISTIC AND DISTRIBUTION ON BASEMENT ROCK OUTCROP IN TANJUNG BATU - TANJUNG LAYANG AND TANJUNG PENGAIL, BANGKA DISTRICT

• Main Author: Satria Perwana, Jaka
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/28214
• Institution: Institut Teknologi Bandung

Naturally fractured basement reservoir exploration requires complete understanding about characteristic of fractures such as fracture orientation, nature of fractal for spacing, aperture, and length of fracture, distribution of intensity and density, Fault Damage Zone (FDZ) and controlling factors of natural fracture. Linear scanline and windows scanline are one of the methods which used to understand the characteristic of fracture. The field work was performed in granitic outcrop at Tanjung Batu – Tanjung Layang and metamorphic outcrop at Tanjung Pengail. A total amount of 3960 fractures in granitic rock and 1534 fractures in metamorphic rocks have been analyzed. The result shows N-S and E-W trending for shear fracture and NE-SW trending for extension fracture and vein. The ENE-WSW trending Tanjung Batu and the E-W trending Tanjung Layang fault in granitic outcrop have width of its FDZ is ?1100 m and ?800 m respectively and the N-S trending Tanjung Pengail fault in metamorphic outcrop has width of its FDZ is ?2600 m. Fracture intensity in granitic outcrop varies between 6.5 – 33.25 m-1 and 19.0 – 40.33 for metamorphic outcrop while fracture density in granitic outcrop varies between 0.05 – 0.32 cm-1 and 0,14 – 0,40 cm-1 for metamorphic outcrop. Distribution of fracture intensity and density shows a declining value as it moves away from the fault core and lithological composition affects distribution of fracture’s intensity and density. Spacing, aperture, and lenght of fracture are fractal and follow the power law distribution with dimension value in granitic rock range between 1.5 – 1.8 for spacing, 1.6 – 1.9 for aperture, and 1 - 1.8 for length. While in metamorphic rock dimension value varies between 1.3 – 1.8 for spacing, 1.3 – 1.9 for aperture, and 1.2 – 1.8 for length. Porosity value obtained from Lucia method in granitic rock varies between 0.7 - 2.6 % and in metamorphic rock varies between 0,8 – 1,7 %. Permeability value obtained from Lucia, Cubes, and Match Sticks method in granitic rock can reach up to 582 darcy, while in metamorphic rock can reach up to 242 darcy.