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Beyond Parasequences: Reservoir Characterization Using High-Resolution (Bedset-Scale) Physical Stratigraphy in Shallow-Marine Strata

 

Hampson, Gary1, Peter Sixsmith2, Oliver Jordan1, Richard Sech1, Sanjeev Gupta1, Matthew Jackson1, Howard Johnson1 (1) Imperial College London, London, United Kingdom (2) Chevron Energy Technology Company, San Ramon, CA

 

Shoreline-shelf deposits contain a high-resolution physical stratigraphy that is below parasequence scale, and which records the evolution of the shoreline-shelf system over short geological time-scales (100-105 years). This presentation aims: (1) to document outcrop and subsurface examples of this high-resolution stratigraphy, (2) to demonstrate its impact on rock-property distribution and fluid flow, and (3) to present generic correlation templates for use in reservoir characterization and modelling.

 

Physical stratigraphy at sub-parasequence scale is defined by discontinuity surfaces that bound packages of beds (“bedsets”). Discontinuity surfaces are marked by: (1) erosion or non-deposition, (2) small (typically <1 km) landward or basinward facies shifts, and/or (3) localized changes in the depositional process regime. The geometry of the surfaces approximates the shoreface-shelf profile, while “bedsets” are comparable in geometry and scale to geomorphic elements of analogous modern shoreline-shelf systems.

 

Insights from outcrop datasets of net-regressive, wave-dominated shoreface-shelf successions (Cretaceous Blackhawk Formation, Book Cliffs, USA) and net-transgressive, mixed wave- and tide-dominated shoreface-shelf successions (Cretaceous Hosta and Cliff House Sandstones, San Juan Basin, USA) allow construction of templates of detailed sub-parasequence-scale stratigraphy. Key aspects of these templates include: (1) the shoreface-shelf geomorphic profile, (2) depositional process regime (e.g. wave climate, which determines the depth of wave-base erosion), and (3) shoreline trajectory, which determines the preservation potential of “bedsets”. The templates can be used in the subsurface to guide well-log correlations and predict inter-well facies volumes and architectures, but their accurate incorporation into reservoir models requires a surface-based approach to reservoir model construction and flow simulation.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California