Research Article X-Ray Computed Tomography Analysis of Sajau Coal, Berau Basin, Indonesia: 3D Imaging of Cleat and Microcleat Characteristics Ahmad Helman Hamdani Faculty of Geology, University of Padjadjaran, Jalan Raya Bandung Sumedang Km 21, Jatinangor, Bandung 45363, Indonesia Correspondence should be addressed to Ahmad Helman Hamdani; ahmad helman pgp@yahoo.com Received 24 March 2015; Revised 31 May 2015; Accepted 4 June 2015 Academic Editor: Robert Tenzer Copyright © 2015 Ahmad Helman Hamdani. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te Pliocene Sajau coals of the Berau Basin area have a moderately to highly developed cleat system. Mostly the cleat fractures are well developed in both bright and dull bands, and these cleats are generally inclined or perpendicular to the bedding planes of the seam. Te presence of cleat networks/fractures in coal seam is the important point in coalbed methane prospect. Te 3D X-ray computed tomography (CT) technique was performed to identify cleats characteristics in the Sajau coal seams, such as the direction of coal cleats, geometry of cleat, and cleats mineralization. By CT scan imaging technique two diferent types of natural fractures observed in Sajau coals have been identifed, that is, face cleats and butt cleats. Tis technique also identifed the direction of face cleats and butt cleats as shown in the resulting 3D images. Based on the images, face cleats show a NNE-SSW direction while butt cleats have a NW-SE direction. Te crosscutting relationship indicated that NNE-SSW cleats were formed earlier than NW-SE cleats. Te procedure also identifed the types of minerals that flled the cleats apertures. Based on their density, the minerals are categorized as follows: very high density minerals (pyrite), high density minerals (anastase), and low density minerals (kaolinite, calcite) were identifed flling the cleats aperture. 1. Introduction Coal is an important source of energy in many parts of the world. Coal is an important source and reservoir rock from which natural gas is formed. Coal is a sedimentary rock with complex polymeric material and dual porosity. Te perme- ability and producibility of coalbed methane reservoir are infuenced by distribution of pore and fractures/cleats. Te CBM accumulation, retention, and recovery involve mechanisms that are signifcantly diferent from those involved in the concentration of conventional gas reserves. Tus, the pore structure and cleats distribution are very important for gas fow pathway. Tere are three known gas fow mechanisms in coal [1, 2]: (1) desorption of gas from coal surface inside the microspores; (2) difusion of gas through microspores as governed by Fick’s law; and (3) Darcy fow through the cleat system, natural fracture network in the coal to the wellbore. However, it should be remembered that various types of minerals can fll cracks and when cracks are flled with minerals, CBM permeability and productivity will be reduced [3–5]. Cleats are one of the most important internal structures of coal. Cleats play an important role in CBM as they are responsible for determining cleats perme- ability networks, including cleat mineralization, morphology, and density, and how cleats are related to macroscale fracture permeability [6, 7]. Maceral type, rank, and mineral contents infuence cleats intensity in coals [8–10]. By nature, coals break easily into small pieces from core and outcrop samples. Terefore, to understand the coal cleat pattern at millimeter scale in coal samples, we need an efective and quick investigation tech- nique that will not destroy samples but can give maximum results. An investigative technique that is increasingly used today is the CT scan tomography [11, 12]. Te ability to perform 3D imaging without destroying samples is one of the advantages of the CT scan method. However, the CT scan method has a limitation as it produces noise and discretiza- tion that afect the imaging artifact and beam hardening and Hindawi Publishing Corporation International Journal of Geophysics Volume 2015, Article ID 415769, 8 pages http://dx.doi.org/10.1155/2015/415769