--> ABSTRACT: Hydrodynamic Analysis as an Aid in Exploration Within Mature Basins: Examples from Sawtooth and Sunburst Reservoirs, Northwestern Williston Basin, by Peter E. Putnam, Suzan Moore, Grant Ward; #91003 (1990).

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ABSTRACT: Hydrodynamic Analysis as an Aid in Exploration Within Mature Basins: Examples from Sawtooth and Sunburst Reservoirs, Northwestern Williston Basin

Peter E. Putnam, Suzan Moore, Grant Ward

Linking hydrodynamics to detailed stratigraphic and structural analyses is a powerful tool in hydrocarbon exploration in mature basins. In southernmost Canada straddling the Alberta-Saskatchewan border, significant petroleum reserves are encountered within Mesozoic units which are largely controlled by subsurface flow cells.

The Jurassic Sawtooth Formation is characterized by an eastward shift from lower shoreface quartzarenites to basinal coquinas. The Sawtooth is a blanket deposit and crops out along the flanks of several Tertiary uplifts in northern Montana. In the subsurface the Sawtooth is draped over several relatively young structures. Potentiometric mapping illustrates a northerly flow orientation within the Sawtooth, and oil pools under artesian conditions are located where flow paths cross steeply flanked structures.

The Lower Cretaceous Sunburst Formation is a series of valley-fill sandstones with mainly southwesterly paleoflow orientations. Hydrocarbon pools (e.g., Manyberries field) are located within a regional potentiometric low formed by three converging cells which recharge in the south, northwest, and east. This potentiometric low is characterized by systematic changes in oil and water compositions, with progressively lighter oils and NaCl-rich waters found toward the low's center. Stratigraphic variability controls pooling within the low, with hydrocarbons located on the updip flanks of valley fills which border nonreservoir rocks.

In the northwestern Williston basin regional hydrodynamic analysis, combined with standard subsurface approaches, allows operators to discern large new hydrocarbon-bearing trends within and between densely drilled areas characterized by complex structure and stratigraphy.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990