AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Characterizing Overbank Deposits for Use in Fluvial Reservoir Models
(1) Chevron Center of Research Excellence; Department of Geology and Geological Engineering, Colorado School of Mines, Golden, CO.
(2) Clastic Stratigraphy R&D, Chevron ETC, San Ramon, CA.
(3) Clastic Stratigraphy R&D, Chevron ETC, Houtson, TX.
(4) Clastic Stratigraphy R&D, Chevron ETC, Perth, WA, Australia.
Fluvial oil and gas reservoirs make up a large percentage of many oil and gas company reserves. The vast majority of the research in fluvial systems is focused on channel-belt processes, architecture, and geometries as these deposits are the target of fluvial reservoirs. Less research has been conducted on overbank strata. These strata which contain sands deposited in levees, crevasse splays, and by avulsion processes have the potential to be economically important reservoirs by themselves and by connecting adjacent channel belt deposits. Currently, the uncertainties in models of overbank sands include facies, architecture, geometry, width, thickness, volume, and the extent to which fluvial overbank sands connect stratigraphically adjacent channel belt sandstones. These uncertainties create challenges for building reservoir models and production strategies for fluvial oil and gas reservoirs.
In order to minimize uncertainties, new models and databases for overbank depositional processes and deposits are constructed from (1) field work in the Eocene Escanilla Formation (Spanish Pyrenees) and the Eocene Middle and Lower Wasatch Formation (Utah), and (2) from publically available data of both modern and ancient fluvial systems. Specifically, these new models and databases are used to:
(1) build a database for widths, thicknesses and lengths of both modern and ancient levee, crevasse splay, and avulsion belt deposits
(2) define lateral and downstream changes in grain-size, sorting, facies distribution and geometries within fluvial overbank deposits
(3) construct a hierarchical classification of overbank deposits in order to aid in understanding stratigraphic cyclicity
(4) understand differences in the frequency, size, and distribution of overbank deposits in relation to differences in fluvial style, climate, and tectonics
(5) understand the role overbank deposits play in connecting adjacent channel-belts
Improved models of fluvial reservoirs will result in more effective production strategies for fluvial reservoirs.