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

• Main Author: Rama, Benito
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/70454
• Institution: Institut Teknologi Bandung

Indonesia’s high demand for fuel as an energy source until 2060 has led to the expansion of oil and gas exploration options toward natural fractured reservoirs. The widely exposed basement rocks in the North Muaracuban area, Jambi can be used as an analogue model to understand the characteristic of natural fractures in basement rocks in the surrounding basins. This research uses methods such as linear scanline and window scanline at 25 scanline stations, with a total scanline length of 49,15 m and a total window area of 24,325 m2. A total amount of 3.135 fractures data were collected from scanline stations in granite, slate, andesite, hornfels, and porphyry andesite. The fractures are grouped into: N-S and NE-SW trending of 1.262 shear fractures; NNW-SSE, E-W, and NW-SE trending of 1.862 extension fractures; and WNW-ESE to NW-SE trending of 11 veins. Fracture intensity ranged between 8 – 108 m-1 in igneous rocks and 9 – 55 m-1 in metamorphic rocks. Fracture density ranged between 47 – 832 m-2 in igneous rocks and 37 – 478 m-2 in metamorphic rocks. Fracture intensity and density are influenced by local stress, distance from fault, structural position of rocks in the fault block, lithology and grain size, and also the deformation history of rocks. NE-SW trending Batang Rengai Fault with a length of 9,88 km cuts through granite and slate, with an FDZ width of 167,7 m in granite and >231,87 m in slate in each block. NE-SW trending Pondok Atap Seng Fault with a length of 469 m cuts through granite, with an FDZ width of 2,7 m in each block, while NNW-SSE trending BR- 1.1A Minor Fault with a length of 3.54 m cuts through granite, with an FDZ width of 61 cm on the hangingwall block and 6,2 cm on the footwall block. The fault length to the width of the FDZ follows the power-law distribution with the equation of y= 0,0137x0,9752 and R2 = 0,97. Fracture attributes (spacing, length, and aperture) are fractal and follow the power-law distribution with fractal dimension (D) range between 0,8 – 1,22 for spacing, 1,46 – 2,7 for aperture, and 1,17 – 1,54 for fracture length. Fracture spacing to linear intensity follows the power-law distribution with fractal dimension (D) range between 0,92 – 1,07. Fracture porosity range between 0,01 – 0,08% using Cubes Method, while fracture permeability range between 2,01 – 14,01 darcy using Matchsticks Method and 2,68 – 18,69 darcy using Cubes Method.