Characterization of Coalbed Methane Reservoirs: A Unified Geoscience and Engineering Approach

Abstract

Once considered a dangerous nuisance in the mining industry, coal seam gas (CSG), or coalbed methane, is now seen as an abundant clean energy supply that will help replace other diminishing hydrocarbon reserves. The nature of the coal-bearing sequences, however, makes them difficult to drill and produce profitably. Major challenges include multiple thin-bedded zones, strong variations in quality of coals, and large volumes of formation water that must be removed before the gas can flow to the surface. This paper describes a new technology- and knowledge-driven approach to address these challenges in the exploration and development stages of a CSG field. During exploration, combining multiple data types in a single model reduces dramatically the uncertainty around coal seam distribution and gas-in-place estimation. In field development planning, the unification integrates static and dynamic data to enable a better understanding of the field's producibility. The exploitation of CSG requires analyses of many scenarios and uncertainties. In addition, it requires hundreds of wells to be drilled in a short period of time. Consideration of the high levels of uncertainty and the integration of large volumes of newly acquired data can be achieved efficiently only in a unified software environment that is associated with a strong knowledge management system. In fact, one of the key benefits of this new unified approach includes the ability to update models and test multiple scenarios at any stage of the field life cycle, and track the processes with a strong audit trail. Data used for demonstration in this paper are from the Surat basin in Central Queensland, Australia.