Abstract: Evaluating the Sealing Capacity of Two Cretaceous Marine Shales, Denver Basin, Colorado

EDWARDS, KIMBERLY K., Colorado State University, Dept. of Earth Resources, Fort Collins, CO

Quantifying sealing capacity has become increasingly important to the petroleum industry. Marine shales provide good seals and it is useful to correlate their physical characteristics with sealing capacity. The Skull Creek and Graneros shales (Cretaceous) were chosen for this study because outcrop, core and wireline logs are available for analysis. These shales have been proven to be source rocks, but they may also provide adequate seals.

Sealing capacity will be assessed by mercury-injection capillary pressure. Other shale characteristics that may effect sealing capacity include: pore throat geometry, ductility, compaction, cementation, mineralogy and position in the stratigraphic sequence. Pore throat shape will be analyzed by using SEM (Scanning Electron Microscopy). Ductility of shale is affected by the expandability of the clay and kerogen content. Kerogen content will be estimated by measuring the total organic carbon. Bulk density tests will be used to determine the compaction. The cement and texture of the shale will be concluded through optical petrography. XRD (X-Ray Diffraction) will be used to determine both the bulk and clay mineralogy. These analyses will thoroughly characterize the shales, in the context of sealing capacity.

Wireline logs will be correlated with the core samples to see if notable changes in the shale are detected within wireline logs. Likewise, outcrop gamma ray will be correlated with the outcrop samples. Detailed core descriptions and stratigraphic columns will be used to determine depositional environment and stratigraphic sequence. The significance of this study is to predict seal occurrence within a sequence stratigraphic context.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid