Biogenic gas accumulations in Canada and China: geological characteristics and new insights

Abstract

Generation of biogenic gas occurs under environmental conditions different from those of thermogenic gas (Rice and Claypool, 1981; Whiticar et al. 1986; Shurr et al., 2003). Microbial activity takes place at shallow depth in a semi-open system where sediments are not fully compacted, seal integrity is not well developed, and accumulation and leakage of microbial gas are competing processes. Thus the formation of a commercial biogenic gas field needs both sufficient microbial activity to maintain gas supply and an efficient entrapment mechanism to minimize gas leakage. This depends on not only the temperature and other microbial growth conditions, but also on the characteristics and internal architecture of both source and reservoir strata. A better understanding of the essential controls and optimal conditions for critical microbial activity, and for the efficient entrapment of gas generated, is important to successful exploration for biogenic resources. This Special Issue of the Bulletin of Canadian Petroleum Geology contains nine thematic research articles on microbial gas resources and their characteristics in the Western Canada Sedimentary Basin and selected Chinese basins. The nine articles are based on the results and findings from a comparative study of shallow biogenic gas resources in Canadian and Chinese basins conducted under a collaborative research agreement between PetroChina and the Geological Survey of Canada during 2010–2013. The agreement provided a unique opportunity to study shallow biogenic gas fields with different origins and characteristics in the two countries. The primary objective of the project is to better understand the critical geological controls on biogenically derived natural gas resources in shallow strata and their resource potential. The characteristics of the biogenic gas fields and available data for describing and quantifying the biogenic gas fields in the two countries are complimentary. The long production history and large amount of public data make the …