Techno-economics for coalbed methane production in the South Wales coalfield

Coalbed methane is the methane rich gas found naturally within coal seams. Such methane is held in place on the coal surface as a free or sorbed gas by the pressure of the surrounding rock and pore water. By controlling the release of this pressure, the methane can be harvested and burned for electricity generation or pumped to the national grid. The present study examines the economic potential of utilising coalbed methane from virgin coal seams at a study area in South Wales and selling that to a power station for electricity generation. The model takes into account several parameters the most important of which are the methane content of the coal, the permeability of the coal, the drainage area of the boreholes, the CAPEX and the OPEX. A decline curve analysis using the exponential decline technique for estimating the future gas production of the study area and the UK Navigant gas projection prices are used to estimate the economic potential of the operation. The results show that methane recovery from virgin coal seams can be considered as an economic option for power generation for the selected study area. 1.0 Introduction Despite the current trends towards shifting to renewable energy, fossil fuels and in particular coal, will continue to be a major source of energy for a period of time in the future. According to the IEA World Energy Outlook (2013), the global demand for coal will increase on average by 1.3% per year for the decades between 2010 and 2040. The tension between the use and the role of coal for power generation in the economic development on one hand, and the increasing demand for environmental protection on the other, has become a critical issue on the political agenda. The key to accommodate this tension is the development and application of clean coal technologies (CCT). One such technology is coal bed methane (CBM). Coal bed methane is produced by drilling into the coal seams, initially releasing water to lower the pressure in the coal seam and then allowing the desorption of the methane gas from the internal surfaces of the coal and the cleat, where it is able to flow (either as free gas or dissolved in water) towards the production well at the surface. By controlling the release of pressure in the coal seam, it is possible to capture the methane in the form of a free gas (EPA, 2004). Occasionally, CBM extraction may need to be enhanced by hydraulic fracturing due to insufficient natural permeability within the coal. The methane gas can then be collected, treated and used in a variety of applications including electricity generation (Figure 1). In 2010, the BGS estimated that the UK has total onshore CBM resources of 2,900 billion cubic meters (DECC 2010). Today, there are a number of active CBM productions in the United Kingdom, such as in Staffordshire and sites in Scotland (Jones et al., 2004). Current successes in the production of CBM in these areas show that it can be implemented in other parts of the UK including South Wales. This study presents the development and application of a techno-economic model to examine the potential and economic viability for employing coalbed methane recovery for power generation at a representative site in the South Wales