Douglas E. Wyatt¹, Frank H. Syms², R. J. Cumbest³
(1) Westinghouse Savannah River Co, Aiken, SC
(2) Bechtel Savannah River Inc, Aiken, SC
(3) Westinghouse Savannah River Co

Abstract: Shallow marine, high resolution reservoir heterogeneity: A model using cone penetrometer data geostatistics

Evaluating heterogeneity is a critical component in reserve estimation and reservoir modeling. Intercalated layering, rapid facies changes and diagenetic modifications are all known in shallow marine reservoirs yet are often difficult to evaluate because of their rapidly varying lateral and vertical extent.

In the Upper Coastal Plain of South Carolina, the "Upland Unit" Tobacco Road and Dry Branch Formations are sediment packages deposited in a near shore, deltaic to fluvially dominated environment. These unconsolidated, late Eocene, (Priabonian) aged sediments are typically silty sands, silts, and sands with thinly laminated clays. As part of the geological characterization process for the construction of the DOE Linear Accelerator, a dense grid of cone penetrometer soundings was obtained to evaluate, in detail, these formations in the shallow subsurface. The area evaluated was approximately 300 by 1600 meters and oriented with the regional dip. CPT data were correlated to subsurface strata using a deep regional boring and seismic data.

The data from the CPT soundings were used to construct a three dimensional geostatistical model capable of imaging the rapid lateral and vertical sediment changes. To simulate potential burial conditions, the model was shear-compressed and re-calculated. Variations in the geostatistics were compared as a potential indicator of heterogeneity. The model demonstrates that there are lateral and vertical bedding and facies changes occurring over short distances. The rate, or dimension of change, may be predictable using a comparison of geostatistical values.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana