Early Mesozoic Buried Rift Basins in Delaware: A Review of Their Occurrence and An Assessment of Their Carbon Storage Potential
Date
2024
Authors
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Publisher
Newark, DE: Delaware Geological Survey, University of Delaware
Abstract
This report presents a review of the occurrence of early Mesozoic buried rift basins in the State of Delaware and a preliminary assessment of their carbon storage potential. The assessment includes projections of the possible stratigraphy of the basins and the volume of rocks available for carbon storage.
Analysis of available geophysical and geological data and comparison with analogous exposed and buried Triassic rift basins of the Eastern United States (Taylorsville, Culpeper, Gettysburg, and Newark Basins) suggest that rift basins occur in Delaware as previously postulated in the literature. However, a review of published interpretations, and integration with lithologic, stratigraphic, and recent geophysical data results in new insights into the basins’ extents, tectonic evolution, and geometry. New magnetics and gravity data confirm that a significant rift basin—the Queen Anne Basin—as well as several smaller basins (the Greenwood and Bridgeville Basins) underlie Delaware. The data suggest that the Queen Anne Basin occurs across Maryland, Delaware, and southern New Jersey and may be larger than previously recognized. Along-trend are the Greenwood and Bridgeville Basins, which may be arms of the Queen Anne Basin or stand-alone basins. The potential for possible rift basins offshore of Delaware, reported in previous studies, is also recognized in this review.
The deposits and successions reported from basins analogous to the proposed Queen Anne Basin are reminiscent of deposits associated with humid, rift basin lacustrine settings where fluvio-lacustrine successions consist of reservoir-quality conglomerates, sands, and silts interbedded with, and overlain by, shales, which serve as local and regional seals. Based on the comparisons and integration of the available data with information on the analogous basins, the Queen Anne Basin is expected to have a similar stratigraphic fill. This suggests that the Queen Anne Basin, as well as the Greenwood and Bridgeville Basins, may contain sufficient thicknesses of reservoir-quality, possibly fluvio-lacustrine, Triassic-Jurassic deposits, which may be suitable carbon storage targets. These deposits are likely sealed locally by interbedded shales and regionally by overlying shales. Thus, the potential for significant carbon storage resources likely exist within buried rift basins in Delaware.
Available data are, however, insufficient for complete and robust characterization of the Delaware buried rift basins. Storage capacity assessments are therefore based on generalized parameters such as uniform minimum and maximum thicknesses and porosities within units across the basins; variations within and across units are not accounted for. The thickness and porosity values used are extrapolated from the limited data available and understanding from analogs. Therefore, the storage capacity estimates presented here represent upper limits of the potential. The preliminary results show that promising carbon storage resource potential exists beneath Delaware in the Queen Anne Basin and the smaller Greenwood and Bridgeville Basins. Preliminary storage capacity calculations suggest that these basins have the combined potential to store between 0.9 Gigatonnes and 9.82 Gigatonnes of CO2 in Delaware. In addition to the previously identified Cretaceous Waste Gate Formation, this new potential extends the resources available for carbon storage in the region.
Further work is needed to define more precisely the distribution and character of these storage resources. Similarly, additional work on seal integrity and geomechanical characteristics is needed to assure the viability of these basins as storage areas. Only a qualitative assessment of the sealing capacity of the shales is carried out in this study. Additional storage opportunities may also exist in possible basins offshore Delaware waters, this also needs to be further assessed.
Description
Keywords
rift basin, carbon sequestration, gravity survey, seismic stratigraphy, geology, geophysics, stratigraphy, magnetic survey