Regional Geological Controls of the Methane Hydrate Occurrence, Beaufort-Mackenzie Basin, Canada
Methane hydrate is a potentially important strategic petroleum resource globally. The analysis of 250 digital well logs from petroleum exploration wells in the Beaufort-Mackenzie Basin (BMB) illustrate and provide new insight into the geological controls of methane hydrate occurrence and resource potential in the BMB. Analyses of the spatial distribution of the inferred methane gas hydrate occurrence in comparison to the conventional petroleum system elements indicates that conventional petroleum system elements exert a fundamental control on the occurrence of methane hydrate accumulations in the basin. The inferred high concentration gas hydrates are restricted to the central part of the study area, where combination of a favorable thermal regime, including specific aspects of the Pliocene and younger surface temperature history, the presence of a permeable network and abundant supply of thermogenic gases from hydrocarbon kitchens, provides favorable conditions for forming large accumulations of methane gas hydrate. Commonly high temperature anomalies and the presence of fault/fracture systems are closely associated with gas hydrate occurrence with high methane saturations, indicating that deep fluid flow systems are involved in the formation of gas hydrate accumulations. High saturation gas hydrate accumulations are less common in northeastern part of the study area, at least in part, if not primarily, because of the lack of effective migration network connecting the thermogenic gas kitchens and gas hydrate stability zone. Absence of gas hydrate deposits in the west Beaufort Sea is primarily due to an unfavorable thermal regime for formation of thick gas hydrate stability zone. This paper suggests that conventional petroleum systems exert a fundamental control on the distribution and richness of inferred gas hydrates. Our results are consistent with recent model studies that suggest that major BMB gas hydrate accumulations formed as a result of the transformation of previously trapped conventional gas in response to surface temperature forcing since Pliocene time. Together these results suggest both that: a) understanding the conventional petroleum system is a key to understanding gas hydrate resource distributions and b) that most high saturation gas hydrate accumulations are elements of the conventional petroleum system that were transformed in-place in response to surface temperature forcing history.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009