--> --> Sequence Stratigraphy, Play Analysis and Reservoir Prediction within a Lacustrine Intracratonic Rift Basin, Western Snake River Plain, Idaho

AAPG Rocky Mountain Section Meeting

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Sequence Stratigraphy, Play Analysis and Reservoir Prediction within a Lacustrine Intracratonic Rift Basin, Western Snake River Plain, Idaho

Abstract

The western Snake River Plain (WSRP) of southwestern Idaho represents an emerging oil and gas producing region with upside potential; however, ongoing exploration and development is hampered by the lack of an integrated view on play types and their structural and stratigraphic setting. The WSRP is underlain by up to 2 km of lacustrine and perilacustrine related siliclclastic sediments that rest on top of a thick succession of mid-Miocene Columbia River Basalts (CRB), with a significant portion of the fill contained within a large Neogene-age intracratonic rift basin. In this study, data from 2D seismic, well logs, ash bed chemostratigraphy, diatom biostratigraphy, and analog outcrop exposures, were merged to construct a regional sequence stratigraphic framework for the northern portion of the WSRP. Results illustrate the presence of three play types that include in ascending stratigraphic order: 1) an early syn-rift fill composed of vertically stacked fluvial sands, 2) a succeeding syn-rift shoreline system associated with lake expansion and transgression, and 3) toe-of-slope fans associated with a post-rift, falling stage systems tract. Each play is distinct in its morphology, structural configuration, migration pathways, seal integrity, and reservoir quality. The syn-rift plays in particular display complex vertical and lateral facies relationships related to the interplay of fluvial and shoreline morphology with pre-existing topography and syndepositional tectonism. Sequence stratigraphic models such as this enhance future exploration and development activities by improving the link between regional observations and the success criteria of potential targets.