FROZEN HEAT | Volume 2

Box 2.1 The gas hydrate resource pyramid

For many years, gas hydrate resources were characterized by extremely large numbers, with perhaps the most commonly- cited value being 700 000 trillion cubic feet (roughly 20 000 trillion cubic metres). While such numbers are meaningful in the context of understanding the role of gas hydrates in carbon cycling and other global processes, they tended to significantly overstate the practical resource potential of gas hydrates by lumping together all manner of gas hydrate occurrences (Boswell and Collett 2011). Earlier attempts to dissect resources of all kinds according to potential productivity revealed a characteristic pyramid shape, with the most favourable elements (at the top) occurring in relatively small volumes, while those resources that pose greater technical challenges (at the bottom) commonly occur in far greater abundance (Masters 1979: Kuuskraa and Schmoker 1998). A pyramid devised for the specific case of gas hydrates (Figure TB2.1.1; after Boswell and Collett 2006) is no different. As with all resource pyramids, the gas hydrate pyramid only suggests the overall order in which production is expected to occur, with resources at the top of the pyramid likely to

be produced before those at the bottom. At present, the global energy industry has worked its way well down the total gas resource pyramid, having focused on shallow onshore deposits at the onset and beginning only recently – after more than a century of exploration – to seriously exploit larger elements at the base, such as shale gas. A similar progression can be expected for gas hydrates. However, the time intervals could well be shorter, given increasingly strong global demand for energy and, in particular, growing use of the relatively carbon-efficient natural gas. While gas hydrate in-place resources change – and change dramatically – over geologic time (see Volume 1 Chapter 2), it is safe to assume that the in-place gas hydrate resource is, for practical purposes, unchanging over human time scales. However, the ability to work through the resource pyramid means that resource recoverability is time-dependant, and the general nature of technological advance (which can be intermittently evolutionary and revolutionary) suggests that recoverable volumes can change dramatically and quickly. In addition, simply being recoverable does not mean a resource will be utilized. It must also be viable economically, which introduces a range of complex and locally varying economic, political, and societal factors.

Figure TB-2.1: The total in-place natural gas resources represented globally by methane hydrates are enormous, but they occur in a wide range of accumulation types. As with other petroleum resources, the accumulation types most favorable for production are the least abundant, creating a pyramidal resource distribution. A generalized resource pyramid for gas hydrates (right) is shown in relation to resource pyramid for all gas resources (left). Society continues to progress down through the global gas pyramid (left), aided by occasional technological breakthroughs that enable significant access to previously unrecoverable resources. Gas hydrates (right) may experience a similar progression with initial production most likely to occur within marine or Arctic sands. Given the vast scale of hydrate resources, however, potential volumes even at the apex of the hydrate pyramid are significant. Figure after Boswell and Collett, 2006. “The Gas Hydrates Resource Pyramid.”

FROZEN HEAT 30