DEVELOPING COAL SEAM METHANE IN THE SYDNEY BASIN

Abstract

Sydney Gas Ltd (SGL) believes that the growth of the new and exciting coal seam methane (CSM) industry will certainly offer significant economic, social, and environmental benefits to the State of NSW within both the short and the long-term.

This paper overviews SGL’s CSM resource development program for the Sydney Basin in general. SGL’s acreage provides an extensive contiguous coverage of the Sydney Basin, and is ideal as it straddles the main gas transmission line from Wollongong to Newcastle.

Gas content is one of the most crucial parameters for CSM resource development. This paper also discusses the method adopted by SGL highlighting the pitfalls in the gas content measurements adopted by previous explorers that caused substantial under-estimation of the CSM resource in the Southern Sydney Basin. Gas content determination comprises three components, i.e. lost gas (Q1), desorbed gas (Q2) and residual gas (Q3). Evaluation of earlier data acquired under an ambient temperature rather than reservoir temperature, was the first source of error which resulted in under-estimating gas content calculation. Zero time for desorption measurements was previously set at core retrieval time rather than core cutting time generating an additional error. That is particularly significant in a highly stress-sensitive coal seam such as the Bulli which is the main target for the CSM resource development in the Southern Sydney Basin.

This paper has also addressed the commercial case for developing CSM as a new energy source in NSW, for so long dependent upon coal and interstate gas.