IOSR Journal of Applied Geology and Geophysics (IOSR-JAGG) e-ISSN: 2321–0990, p-ISSN: 2321–0982.Volume 6, Issue 3 Ver. III (May. – June. 2018), PP 09-17 www.iosrjournals.org DOI: 10.9790/0990-0603030917 www.iosrjournals.org 9 | Page Pore Systems Analysis of Posidonia and Wealden Shales of Lower Saxony Basin, Germany *M. Bukar 1 , F. A. Rufai 2 , A. Y. Kuku 1 , M. Halilu 2 and B. Shettima 1 1 Geology Department, University of Maiduguri, Nigeria 2 Geology Department, Modibbo Adama University of Technology Yola, Nigeria Corresponding Author: M. Bukar Abstract: As the global demand of natural gas increases, exploration for source of natural gas also increased in recent times, shale is being considered as gas storage facility. The aim of this research is to examine and characterise pores between organic and inorganic mineral grains from both Posidonia and Wealden shales of the lower Saxony Basin, Germany using the nanometer-scaled pore systems. This is to ascertain their gas storage capabilities as well as permeability pathways and to also compare mercury injection data with the measured porosity. Focused ion beam, broad ion beam, scanning electron microscope imaging and mercury intrusion porosimetry were used to study the porosity of these shale samples. Qualitative and quantitative description of microstructures and pores were carried out using Jmicrovision v.1.27 computer software. Pore system is found to be dominated by angular and ellipsoidal interparticle pores connected by narrow tube like pore-throats and subordinate poorly connected ellipsoidal intraparticle pores and no organic matter pores were identified probably due to immature nature of the samples. Some artefact pseudo-pores were introduced into the samples during sample preparations. Mercury intrusion porosimetry gave porosity of 6.5% and 5.9% which are higher than measured porosity of 2.5% and 0.5% for Posidonia and Wealden shales respectively. These pores could be the possible storage for natural gas accumulation when generated. Keywords: Broad ion beam (BIB), Focused ion beam (FIB), nanometre-scale, Posidonia, Wealden. --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 02-06-2018 Date of acceptance: 18-06-2018 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction The ability to economically produce gas and oils from rocks that have traditionally been considered both as source and seals has forced a paradigm shift in our understanding of the pore structure of low- permeability rocks. Understanding the pore system of these rocks has been hindered by our lack of tools to investigate their pore structure (Gareth et al., 2011). Porosity and permeability are two parameters to consider in oil and gas production. Porosity is the fraction or void (empty) spaces in a rock, this void spaces can be between grains or within cracks or cavity of rocks. The void spaces have the ability to store oil, gas or water. Permeability is a measure of ease with which a fluid or gas can move through a porous rock. Shale, an argillaceous material is characterized by its low macro porosity and permeability; it takes a lot of pressure to squeeze fluid through a rock that has low permeability. Shale research has recently gained popularity as a future source of gas storage. Its significance led to the scientific studies/investigations of several shale systems. Recent studies showed that a pore network may have one dominant pore type or a complex combination. Mudstones from the Barnett Shale for example have a pore network dominated by organic-matter intraparticle pores, whereas the Pearsall Shale appears to have a pore network dominated by interparticle and intraparticle pores (Loucks et al., 2011). Imaging of pore space in fine grained geological materials is a rapidly developing field since ion milling had shown to produce smooth and damage free surfaces (Holzer et al., 2007, 2010; Loucks et al., 2009). Measurement of porosity depends strongly on the method used, as different methods detect different classes of pores. Pores in mudrocks are not easily identified using conventional sample-preparation methods. This is due to the fact that artefacts are difficult to differentiate from real/true pores. Hence, to image pores accurately new approaches have been implemented (Reed and Loucks, 2007). With that pores can be recognized as small as 5nm. Loucks et al, (2009) stated that micropores are also associated with diagenetic minerals during its transformation to rock. These minerals may be quartz or pyrite which will eventually fill the moulds left by fossils such as algal spore and forming casts. Organic-matter pores and interparticle pores have better probabilities that may be connected and form a permeable pathway than isolated intraparticle pores (Loucks et al., 2011). Loucks et al., (2009) and Sondergeld et al., (2010) documented that pores identified using SEM and FESEM may really be remnant depressions of grains that were artificially plucked during sample preparation and polishing caused by mineral hardness. The artificially made pores are circular or ellipsoidal in shape and the