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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 57 (1973)

Issue: 11. (November)

First Page: 2217

Last Page: 2244

Title: Cementation in Lyons Sandstone and its Role in Oil Accumulation, Denver Basin, Colorado

Author(s): D. W. Levandowski (2), M. E. Kaley (3), S. R. Silverman (3), R. G. Smalley (3)

Abstract:

Cementing materials modify the primary porosity and permeability of a reservoir sand and are therefore of vital importance to oil geology. Detailed petrographic study of the Lyons (Permian) Sandstone of the Denver basin, Colorado, indicates that many different cements resulted from depositional and post-depositional processes. The order of deposition of cementing and matrix materials was established as clay and/or iron oxide, secondary quartz, solid organic matter, and anhydrite and/or carbonate. A regional pattern of cementation shows a marked increase toward the western margin of the basin. Spectrochemical analyses of the anhydrite cement show that the SrO/CaSO4 ratio differentiates normal, leached, and enriched types of anhydrite. Their distribution indicate that the migration of the cementing fluids was vertical from below into the Lyons, and from east to west within the formation.

The relation of the cementing materials and fluid movements to the migration and accumulation of oil is considered. The solid organic matter noted in thin-section study appears to be related to the present occurrence of oil. In addition, carbon isotope analysis indicates that the carbonate cement is derived partly from reactions of petroleum constituents with sulfate and oxide minerals.

Following is an overall summation of the geologic history of the Lyons Formation.

1. Deposition of quartz sand with clay and iron oxide matrix.

2. Compaction of the sand and subjacent sediments causing vertical and lateral movement of formation waters with quartz solution and deposition.

3. Migration of oil or bitumen into the Lyons, probably into early, broad, low structures.

4. Further burial and compaction displacing sulfate-bearing waters upward and from the basin center toward the margin, with resulting anhydrite and carbonate cementation.

5. Development of present Lyons structures.

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