ANALYSIS FRACTURE CHARACTERISTICS AND DISTRIBUTION IN BASEMENT ROCK OUTCROP IN AIR BATU, MERANGIN, JAMBI

• Main Author: Nababan, Chrisdiantoro
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/53012
• Institution: Institut Teknologi Bandung

The availability of oil and gas in Indonesia tends to decline, so the potential energy source in the form of oil in naturally fractured reservoirs is an optimal alternative. The widely exposed basement rocks in the Airbatu, Jambi can be used as an analog model to understand the characteristic of natural fractures in basement rocks, such as fracture orientation, fracture intensity and density distribution, estimated fault damage zone (FDZ), fractal properties of fracture attributes and estimated porosity and permeability. This research uses linear scanline and window scanline methods at 19 scanline points, with a total scanline length of 25,9 m and a total window area of 20,64 m2. Measurement of natural fracture data was carried out on granite and metamorphic basement outcrops. The total fracture is 2280 fractures, in the form of 1659 joints, 574 shear fractures, and 11 veins. The joint and shear fractures dominant orientation is northwest–southeast (NW– SE), west–east (W–E) and northeast–southwest (NE–SW). The vein orientation is northeast–southwest (NE–SW) and northwest–southeast (NW–SE). Fracture intensity in the research area ranged between 8–41 m-1 in granite rocks and 45–47 m-1 in metamorphic rocks, and intensity areal in research area ranged between 8– 46 m-1 in granite rocks and 38–65 m-1 in metamorphic rocks. Fracture density in the research area ranged between 26–303 m-2 in granite rocks and 293–332 m-2 in metamorphic rocks. Fracture intensity and density are influenced by distance from fault, lithology and grain size, and also fracture space. The width of the Fault Damage Zone (FDZ) in the Airbatu Fault is 346 meters, and the Batangmerangin Faults are 49,5 meters. Fracture attributes are fractal and follow the power-law distribution with fractal dimension (D) range between 0.69 – 1.55 for spacing, 0.55–1.18 for aperture, and 0.92 – 1.39 for fracture length. The fracture porosity values ranged from 0.002–0.01% (Cubes Method) and 0.008–0.41% (Lucia Method) and while the fracture permeability values ranged from 0.003–0.07 darcy (Matchsticks Method) 0.72–7.58 darcy (Lucia Method) and 0.005–0.1 darcy (Cubes Method).