North America Unconventionals: What Have We Missed?

Abstract

With recent advances in technology, North American shale gas plays are now considered to be well defined. But, the relative lack of success elsewhere in the world, is a reminder that there are shales - and there are shales. By better defining depositional controls, can missed opportunities in North America be identified, and applied to reduce unconventionals risk globally? To identify new shale gas opportunities within North America, our methodology focuses on depositional factors, by reconstructing and modelling those processes which affect shale depositional systems. Fundamental to this is to reconstruct the sediment system, from source to sink. Reconstruction of the structural and tectonic framework of North America acts as a foundation for detailed paleogeographic reconstructions of the tectonic and depositional history of the North American Plate. This is important, as it relates to sediment supply (uplift, weathering, erosion and transport). The depositional environments are mapped according to their gross depositional environment, which, when combined with lithology, provides information on facies. These reconstructions are then converted to paleolandscapes, within which are reconstructed paleodrainage systems, derived from analysis of Present Day river networks, provenance data and paleocurrent directions. Earth Systems Modelling gives insight into contemporary climatic conditions, this is an important controlling factor on weathering in the hinterland. This affects the nature of the eroded sediments, the process of their transportation and their routing to the sink area. Ocean and tide models are then used to deduce the submarine sediment transport pathways. Through the integration of these data an informed interpretation of the nature and extent of deposition in the sink areas can be reached. By adding modelled outputs of processes including productivity, upwelling, oxygen saturation and calibrating these with measured geochemical source rock richness data, insight can be gained into not only the distribution of shales, but also a calibrated, quantitative prediction of the depositional quality of the shale can be achieved. Through the application of these methods, and integration of the knowledge that has been accrued through exploration over time, our aim is to establish a more effective method of shale gas exploration, which could then be applied on a global scale.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015