Characterizing Moisture and Gas Content of Coal by Low-Field NMR

• DOI: 10.2118/07-10-05
• Publication Date: 2010-03-15T14:23:48Z
• Authors: R. Guo; K. Mannhardt; A. Kantzas
• Keywords: Coalbed Methane

Abstract Coalbed Methane (CBM) shows great potential to be an important energy source. One key factor for the successful development of CBM processes is characterize coal on its moisture and gas content. Usually, content are determined from laboratory analysis. Low-field nuclear magnetic resonance (NMR) a relatively new technique used in logging analysis fluids contained reservoir rocks. This paper investigates characterization by low-field NMR. NMR detects hydrogen-bearing molecules and, rock samples, distinguishes between ‘free’ bulk fluid ‘bound’ surface fluid. Coal contains free water cleats as well that forms integral part structure. light hydrocarbon methane fractures adsorbed internal surfaces. implications moisture, adsorption isotherm measurements explored. Experiments moisture-free coal, moist coal/water mixtures indicated drastically different spectra. From these spectra, bound could estimated using methodology currently applied clay-rich formations. In this paper, two sets data presented. First, at ambient conditions provided reference other conventional cutoff data. Second, high-pressure cell measurement was comparisons were made. samples form powder chunk used. The focuses methods results date. Introduction has evolved into commercially profitable source natural gas. Canada vast resources it been total in-place reserves 36 ? 1012 m3. Over 60% Canada's assets Alberta(1). contributing significant portion Canadian production near future. proximate desorption laboratory. Nuclear occurs when nuclei certain atoms (i.e. hydrogen proton) immersed static field exposed second oscillating field(2). provides non-destructive analytical method detecting hydrocarbons reservoirs(3) characterizing gas(4). Generally, spectrum can provide three types information: quantities rock, mobility (viscosity) information about pores contain fluids. As same time large amounts methane. Water exists