The Potential for Gas Storage in Bioturbated Media: a Case Study from the Upper Cretaceous Alderson Member (Lea Park Formation) - Hatton Gas Pool, SW-Saskatchewan, Canada
The Alderson Member (Lea Park Formation) of western Canada is a sedimentologically complex clastic unit. The Alderson Member is an example of a giant gas-play that revolves around low permeability, non-associated reservoirs. The fields contained within this play produce from shallow zones (less than ~600m) from thin bedded, fine-grained sand within muddy units. In many cases the productive zones are interbedded with, or are, the source rock. Such intervals can be laterally extensive and continuous.
The presence of sand-rich burrows within otherwise fine-grained media, suggests that burrow fabrics within the Alderson Member may enhance the storativity and deliverability of gas. Using porosimetry and minipermeametry, the impact biogenic fabrics have on reservoir behaviour has been deduced. Mercury porosimetry shows that the pore-throat distribution of Phycosiphon-bioturbated sandy mudstone is similar to interlaminated silt and sand. These bioturbated zones can be several meters thick, and thus represent an estimable part of the deliverable resource. Moreover, burrow permeability is one to two orders of magnitude higher than matrix permeability. The impact of the permeability depends on the size of burrows and the burrowing intensity in a given unit.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009