Lion Canyon Sandstone: Stratigraphic Significance and Analog for Tight-Gas Marine Sandstone Reservoirs
The Maastrichtian Lion Canyon Sandstone of the upper Williams Fork Formation formed at the turnaround from a major transgression to a major regression of the Western Interior Seaway. Thus, the lower part of the Lyon Canyon Sandstone formed during the culmination of the Almond overall backstepping trend, whereas the upper part formed during the initial progradation that continued as the Lance-Fox Hills-Lewis Shale progradational trend. The dataset includes fifteen detailed stratigraphic sections measured across a 21 km long outcrop belt, and 11 well logs across a 273 km2 area in northwestern Colorado, USA. Twenty one identified sedimentary facies and nine facies associations show that the lower part of the Lion Canyon Sandstone consists of river-dominated deltaic clinothem sets with mouth bar and distributary channel deposits that stack in an overall backstepping manner. In contrast, the upper part of the Lion Canyon Sandstone is composed of wave-dominated deltaic clinothem sets with storm-dominated delta front and associated distributary channel deposits, with clinoform surfaces showing progradation to the north and east. Three main styles of macroscopic carbonate cementation are observed in the Lion Canyon Sandstone: (1) small spherical to elongate concretions; (2) large lens-shaped concretions; and (3) laterally extensive cemented zones. Lens-shaped concretions and laterally extensive cemented zones are associated with specific stratigraphic levels: major marine flooding surfaces, tops of clinothem sets, tops of individual clinothems, as well as with the top of the deltaic package. Carbonate cementation is more extensive in the upper wave-dominated part of the Lion Canyon Sandstone than the lower river-dominated part. Such cementation zones are predicted to have a higher impact on hydrocarbon reservoir properties than facies variability in reservoirs similar to the Lyon Canyon Sandstone. Carbonate cementation compartmentalizes the reservoir and has an effect on volumetric calculations and production aspects such as perforation intervals, well spacing, horizontal well orientation, and secondary recovery techniques. Timing of cementation is important as early diagenetic cementation will present a barrier to hydrocarbon migration into the reservoir. Carbonate cemented zones will not only act as major flow boundaries but also reduce porosity in the coarsest grained deltaic deposits.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California