Reservoir Architecture and Tough Gas Reservoir Potential of Fluvial Crevasse-splay Deposits

摘要

Unconventional tough gas reservoirs in low-net-to-gross fluvial stratigraphic intervals may constitute a secondary source of fossil energy to prolong the gas supply in the future. To date, however, production from these thin-bedded, fine-grained reservoirs has been hampered by the economic risks associated with the uncertainties in their geometry, spatial distribution and reservoir properties. This study aims to provide a better insight into the reservoir architecture and tough gas reservoir potential of stacked and interconnected crevasse splays in a fluvial floodplain stratigraphy. Despite their thickness not exceeding decimetre scale, the surface area of individual crevasse splays may be up to several square kilometres and intervals of stacked and interconnected crevasse splays range up to several metres in thickness. Through incision of consecutive crevasse splays into underlying lobes and the channel fill of cut-through avulsed channels, sand-on-sand contact is established, effectively connecting individual splays. The net reservoir volume of single crevasse splays ranges up to several hundred thousand cubic metres, yielding GIIP estimations in the order of several million cubic metres. For intervals of stacked and interconnected crevasse splays, these figures are up to one order of magnitude higher, making them suitable as a secondary reservoir capacity.