ANALYSIS OF NATURALLY FRACTURE CHARACTERISTICSIN CRYSTALLINE ROCKS IN THE LHOONG, ACEH BESARREGENCY, ACEH PROVINCE

• Main Author: Emil Fajri Kamil, Moch
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/70470
• Institution: Institut Teknologi Bandung

About 20% of the world's oil and gas reserves are stored in a naturally fractured reservoir. However, naturally fractured reservoirs have complex systems. Preliminary studies are required with a systemic approach consists of analysis in the basement and nonbasement rocks outcrop in the Lhoong, Aceh Province consisting of andesite and granodiorite. The collection of the data was done by linear and windows scanline methods that obtained 457 natural fractures on andesite and 252 natural fractures on granodiorite consisting of shear fracture, extension fracture, and joints. Andesite is dominated by systematic joints trending ESE-WNW and nonsystematic joints trending NE-SW, which are cut by shear fractures trending NE-SW and SE-NW and extension fractures trending WNW-ESE. There are shear fractures that are directed relatively W-E because of the joints movement that was formed in the past. Meanwhile, in granodiorite dominated by shear fractures trending NNE-SSW and SSE-NNW that formed simultaneously with the extension fractures trending NNE-SSW followed by the formation of the systematic joints trending WNW-ESE and NW-SE. The number of extension fractures as veins in the andesite causes the connectivity of andesite to be lower. The intensity of the fracture of andesite and granodiorite is 15.8 – 40.3/m and 8 – 56/m respectively and densities of fracture are 54.21 – 90/m2 and 39 – 248/m2, respectively. Different spatial arrangements can result different intensity values. The intensity and density will be greater if the distance to the fault gets closer. The width of the damage zone Suhom Fault is greater than 17 m and Upper Geunteut Minor Fault is 216.96 cm. The fracture’s attributes are fractal with a fractal dimension in the andesite for the spacing of 0.92, aperture 1.05, and length 1.2. While in granodiorite for the spacing with dimensions 0.78, aperture 1.04, and length 0.88. The estimated porosity in andesite and granodiorite is 1.81 – 7.41% and 1.23 – 10.97% respectively. Meanwhile, the estimated permeability is 9.94 – 33.62 darcy and 3.53 – 70.86 darcy.