The Analysis of Characteristic and Distribution of Natural Fracture on Basement Outcrop at Kedabang Cape, Batam Island, Kepulauan Riau Province
Geological exploration in Naturally Fractured Reservoirs (NFR) require in-depth understanding of natural fracture characteristics such as fracture orientation, fractal properties of fracture attributes, fracture intensity and density distribution in the Fault Damage Zone (FDZ), and the factors that control their distribution. The research area is administratively included in the Nongsa District, Batam City, Kepulauan Riau Province. The research area geographically stretches between 1˚8’21” - 1˚8’41” N and 104˚8’47” - 104˚9’8” E. Measurement of natural fracture data using the linear scanline and window scanline methods in the Kedabang Cape research area. Measurement of natural fracture data was carried out on granite and rhyolite basement outcrops. The total fracture is 769 fractures, in the form of 587 joints, 177 shear fractures, and 5 veins.
The joint orientation is NNW-SSE and ENE-WSW. The shear fracture orientation is NE-SW and ENE-WSW and the vein orientation is ENE-WSW. The fracture intensity in Kedabang Cape is 6-32 fractures/m, while the fracture density is 0,09-0,42 cm/cm². The width of the Fault Damage Zone (FDZ) in the Kedabang Cape Fault is between 23-90 m, while for the YFP-A4 outcrop-scale fault is 3,8 m. The width of the fault damage zone shows a linear relationship with the length and displacement of the fault plane. The intensity and density of fractures inside the damage zone are greater than background zone. Natural fractures in the research area are fractally distributed, following the power law distribution. The fracture porosity of basement outcrop in Kedabang Cape varied in the range 0,01-0,09%. The fracture permeability based on the Cubes Method varied in the range 0.53-83.82 darcy, while based on the Matchstick Method ranges from 0.40-62.86 darcy.