ROSS, WILLIAM C., DALE E. WATTS, and JEFFREY A. MAY, Marathon Oil Company, Littleton, CO; and E. CATHY GREENBERG, Marathon Oil Company, Houston, TX

ABSTRACT: Deep-Water Sand Distribution as a Function of Basin-Fill Geometry: An Empirical Relationship for Quantitative Model Calibration

Computer simulations of sedimentary basin fills are being developed to help predict reservoir facies in areas of little or no well control. To calibrate our model we studied empirical relationships between basin-fill geometries and lithology distributions. We analyzed regional stratigraphic cross-sections through the Maastrichtian-aged Fox Hills and Lewis formations of south-central Wyoming to test whether the quantity of sand bypassed into deep-water environments can be modeled by varying (1) sand:mud ratios in the topset setting and (2) the ratio of accommodation space versus the amount of sediment entering the basin per unit time (referred to as the basin-fill style, BFS).

Variations in basin-fill geometries can be related to BFS. A BFS >1 correlates to aggradational geometries whereas a BFS <1 corresponds to progradational geometries. With a constant topset sand:mud ratio, as BFS decreases greater percentages of sand bypass basinward. To quantify variations in basin-fill geometries from the Fox Hills-Lewis cross-sections we defined a proxy for BFS as the ratio of topset sediment area over the total sediment area.

From the cross-sections we also tabulated the amount of deep-water sand as a percentage of total sand for 16 stratigraphic intervals. There is a strong correlation between deep-water sand percentage and basin-fill style. This empirical relationship indicates that modeling schemes which match basin-fill geometry and utilize sparse sand:mud data from the basin can predict the quantity of sands distributed in deep-water environments.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.