--> --> The value of detailed reservoir characterization and stratigraphic interpretation: An example from the San Joaquin Basin, California, U.S.A.

AAPG Pacific Section and Rocky Mountain Section Joint Meeting

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The value of detailed reservoir characterization and stratigraphic interpretation: An example from the San Joaquin Basin, California, U.S.A.

Abstract

The value of detailed reservoir characterization, stratigraphic interpretation and earth modeling is not always easy to assess: these disciplines are typically considered as fundamental for development studies; however assigning value to the workflow and products is often difficult. The impacts of detailed reservoir characterization and stratigraphic interpretation are explored in the context of a large siliciclastic reservoir within the San Joaquin Basin of central California that was in an early stage evaluation for waterflood potential. Initial regional mapping of the major units suggested sheet-like geometries yielding a 5-spot pattern waterflood development concept for the entire prospective reservoir acreage resulting in over 250 patterns. In order to better understand reservoir geometries, the decision was made to complete a detailed reservoir characterization and stratigraphic interpretation analysis. This study has utilized newly acquired log and core data that have been incorporated into an existing subsurface dataset consisting of several thousand wells to develop detailed 3-D structural property models. Well log, core and FMI, production, and mudlog data have all been integrated to develop a robust interpretation of reservoir body geometry, connectivity and continuity over the prospective area. We now interpret the formation to consist of reservoir facies assemblages characteristic of deposition within estuarine tidal systems. Major depositional facies recognized within prospective reservoir intervals include offshore, tidal flats and bars, and tidal channels. Channel bodies consist of single to multi-storey fining upward packages and are highly discontinuous and stratigraphically complex. Integration of the detailed stratigraphic interpretation of the complex reservoir geometries into the waterflood development concept resulted in high grading the prospective area of development to only the mapped channel sands which have reservoir properties conducive to waterflooding. The project scope has been greatly reduced to 80 patterns with focus now on geobodies having favorable waterflooding characteristics. While this study has reduced the prospective area of waterflood potential it allows a more focused approach to progress this opportunity to a successful execution. Recognition and distribution of the remaining marginal reservoir quality facies has initiated a new project to determine potential development concepts for these resources.