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PULHAM, ANDREW, Department of Geological Sciences, University of Colorado, Boulder, CO

ABSTRACT: Reservoir Performance and Reservoir Quality in a Sequence Stratigraphic Framework: Case Studies from Siliciclastic Reservoirs in the Americas and Europe

Understanding the production characteristics of oil and gas reservoirs is key to effective exploitation and intervention strategies. The overriding rock property of interest to reservoir management is permeability. One of many potential scales of heterogeneity that can influence distribution of permeability and thereby reservoir behavior is the stratigraphic architecture of the depositional system that is being produced. Key surfaces and events, such as sequence boundaries and transgressive episodes, can mark the most significant changes in lateral and vertical reservoir properties. The recognition of stratigraphic events within any reservoir is dependent on understanding the genesis of the sedimentology. In this respect, often-overlooked techniques such as ichnofacies analysis and quantitative biostratigraphy are critical in building a complete picture of the depositional history. In establishing the controls on permeability within a reservoir, simple sandstone textural analysis can supply most of the understanding needed to quantify the effects of various stratigraphic events.

Several case studies are offered on this lecture tour that examine how the high-resolution stratigraphic architecture of producing reservoirs compares with dynamic information such as pressure decline and well production data. The themes of each case study are the recognition of the stratigraphy surfaces and their hierarchy and a quantification of which stratigraphic events have the greatest significance to reservoir behavior. Some of the key conclusions based on the examples presented are that primary depositional fabrics are fundamentally important in explaining reservoir behavior despite the complexities of the post-depositional histories. In support of the producing reservoirs, additional case studies examine the distribution of reservoir quality in a stratigraphic framework. These also indicate that key stratigraphic events have a major control on how permeability is distributed within depositional systems.

Themes of the case studies include the importance of competing processes such as fluvial and tides during stratigraphic episodes, the utility of combining disciplines such as ichnology, biostratigraphy, and sedimentology and how simple descriptions can identify critical permeability fabrics.

AAPG Search and Discovery Article #90910©2000-2001 AAPG Distinguished Lectures