ANALYSIS OF THE CHARACTERISTIC AND DISTRIBUTION OF NATURAL FRACTURES IN BASEMENT ROCK OUTCROP IN SUNGAIBAUNG, SAROLANGUN REGENCY, JAMBI

• Main Author: Naufal Valdiansyah, Rachdyan
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/53281
• Institution: Institut Teknologi Bandung

Demand for fuel as an energy in Indonesia is increasing, meanwhile the production rate is decreasing. Naturally fractured reservoir can be an exploration option to meet Indonesia’s demand for fuel. The widely exposed basement rocks in the Sungaibaung area, Jambi can be used as an analogue model to understand the characteristic of natural fractures in basement rocks in the subsurface. This research uses methods such as linear scanline and window scanline at 20 scanline stations, with a total scanline length of 56,45 m and a total window area of 27,8 m2. A total amount of 2.745 fractures data were collected from scanline stations in granite, andesite, and slate. The fractures are grouped into: N-S and NE-SW trending of 935 shear fractures; N-S, E-W, NE-SW and NW-SE trending of 1.777 extension fractures; and WNW-ESE to NW-SE trending of 9 veins. Fracture intensity ranged between 2 – 64 m-1 in igneous rocks and 7 – 46 m-1 in slate. Fracture density ranged between 0,0004 - 0,0387 cm-2 in igneous rocks and 0,007 - 0,02 cm-2 in metamorphic rocks. Fracture intensity and density are influenced by local stress, distance from fault, lithology, grain size, and also the deformation history of rocks Kasiro Fault with a length of 3,38 km has a fault damage zone (FDZ) width of 287,06 m. Sungaibaung Fault with a length of 2,42 km has a FDZ width of 287,06 m, while Atapseng Fault with a length of 469 m km has a FDZ width of 2,58 m. The fault length to the width of the FDZ follows the power-law distribution with the equation of y = 10-6x2,4 dan R2 = 0,99. Fracture attributes (spacing, length, and aperture) are fractal and follow the power-law distribution with fractal dimension (D) range between 0,51 - 0,95 for spacing, 1,23 - 1,72 for aperture, and 1,12 - 1,32 for fracture length. Fracture porosity range between 0,01 – 0,07 % using Matchsticks 0,01 – 0,1 % using Cubes method, while fracture permeability range between 1,12 – 17,16 darcy using Matchsticks method and 1,88 – 22,88 darcy using Cubes method.