121 Indonesian Journal on Geoscience Vol. 4 No. 3 December 2017: 121-141 IJOG/JGI (Jurnal Geologi Indonesia) - Acredited by LIPI No. 547/AU2/P2MI-LIPI/06/2013. valid 21 June 2013 - 21 June 2016 How to cite this article: Sapiie, B., Nugraha, M.A., Wardana, R.K., and Rifyanto, A., 2017. Fracture Characteristics of Mélange Complex Basement in Bantimala Area, South Sulawesi, Indonesia. Indonesian Journal on Geoscience, 4 (3), p.121- 141. DOI: 10.17014/ijog.4.2.121-141 Fracture Characteristics of Mélange Complex Basement in Bantimala Area, South Sulawesi, Indonesia Benyamin Sapiie, Muhamad Aziz Nugraha, Rizky Kurniawan Wardana, and Arif Rifiyanto Geology Study Program, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung Jln. Ganesha No. 10, Bandung 40132, Indonesia Corresponding author: bsapiie@gc.itb.ac.id Manuscript received: June 8, 2017; revised: June 22, 2017; approved: July 3, 2017; available online: August 1, 2017 Abstract - A detailed geological mapping and fracture characterization had been performed in Bantimala area, South Sulawesi, Indonesia. The geology of the studied area is composed of pre-Tertiary metamorphic, sedimentary, and igneous rocks which tectonically mixed forming a mélange complex. Located on the southeastern margin of Sundaland, the tectonic strongly infuences the fracture occurrences in the studied area. A total of 3,841 fractures comprising shear fractures, extension fractures, veins, and joints have been measured and analyzed. The common fracture orientations are NW - SE, W - E, NNE - SSW, and ENE - WSW trends. Fractures developing in Bantimala have clearly been controlled by lithology and structure position (i.e. fault zones and fold hinge). The orientation of fractures in Bantimala area is different on each lithology, showing that the fracture system was complex. Fracture intensity in schist is higher compared to the other lithologies. The 3D fracture modeling through 3D geocellular modeling was generated using the result from feld data measurements and analyses. Discrete Fracture Network (DFN) was built by ffty-one fracture sets that were analyzed from feld measurement data. However, the estimation of average fracture porosity from modeling varies signifcantly depending on lithology. The value of fracture porosity is relatively small, varied from 0.0004 to 0.0029 %. A high fracture porosity number is observed in an area with a signifcant fracture intensity and most crosscutting of fracture which in turn is controlled by faults and lithology. A mélange complex can have high potential as a basement fractured reservoir target, where fracture distributions and their attributes will vary depending on the lithology as well as local deformation. Keywords: Bantimala Mélange Complex, basement fractured reservoir, Discrete Fracture Network, 3D Geocellular Modeling © IJOG - 2017. All right reserved Introduction Naturally, a fractured reservoir is proven as a productive reservoir in numerous oil felds. A basement is one of lithologies that performs as a naturally fractured reservoir. A number of frac- tured basement reservoirs have been discovered in the world (Koning, 1985; Koning and Darmono, 1989; Nelson, 2001; Sapiie et al ., 2014). A recent oil and gas exploration in the offshore of the north- ern Madura Island discovered gas within the base- ment rocks. The basement lithology was made of various rocks which are interpreted as part of the Cretaceous accretionary complex developed as mélange. Mélange complexes are widely distrib- uted in the Indonesian archipelago but exposed in INDONESIAN JOURNAL ON GEOSCIENCE Geological Agency Ministry of Energy and Mineral Resources Journal homepage: hĨp://ijog.geologi.esdm.go.id ISSN 2355-9314, e-ISSN 2355-9306 Accredited by: - LIPI, valid August 2016 - August 2021 - RISTEKDIKTI, valid May 2016 - May 2021 IJOG