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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 63 (1979)

Issue: 3. (March)

First Page: 510

Last Page: 511

Title: Diagenesis in Hygiene and Terry Sandstones (Upper Cretaceous), Spindle Field, Colorado: ABSTRACT

Author(s): Karen W. Porter, Robert J. Weimer

Article Type: Meeting abstract


Recent research in the field of sandstone diagenesis suggests a relation between depositional fabric and the observed pore-filling sequence. An ordered paragenetic sequence representing an ordered decrease in energy-of-formation (^DgrF°f) values is reported for fine-grained, poorly sorted sandstones. Coarser grained, better sorted sandstones from the same depositional environment show unordered diagenesis with respect to ^DgrG°f, perhaps related to higher fluid flow and less influence of rock composition. A relation may also exist between diagenetic sequence and depositional environment;

End_Page 510------------------------------

chlorite is common as initial pore filling in marine rocks, whereas kaolinite and illite initiate pore filling in nonmarine rocks.

Spindle field, second largest oil field in Colorado, produces oil and gas from Hygiene and Terry sandstones deposited as offshore marine bars. Upward-coarsening lithofacies in both sandstones are: (1) bioturbated muddy sandstones (shelf and interbar); (2) very fine-grained, poorly sorted, weakly cross-stratified sandstone (bar margin); (3) fine-grained to medium-grained, moderately sorted, cross-stratified sandstone (central bar).

On the basis of known fabrics and environments, Hygiene and Terry sandstones were predicted by use of the reported diagenesis model to show a ^DgrG°f-related diagenesis in interbar and bar-margin facies, and an initial chlorite diagenesis in the central-bar facies. Preliminary thin-section and SEM investigations tend to confirm the prediction for the finer grained facies. The origin of kaolinite-rich pore filling in the central-bar facies is not clearly understood, but it may be related to abundant argillaceous clasts which provide in-situ material for continuous alteration of pore-fluid composition during diagenesis.

Modification of predicted diagenesis in the coarser grained facies provides an additional basis for anticipation of diagenetic sequences in other offshore-bar deposits.

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Copyright 1997 American Association of Petroleum Geologists