Deep-Water Clastic Sediments: A Core Workshop

This core workshop on deep-water clastic sediments was organized to provide participants with an opportunity to view cores from a variety of deep water depositional settings and to demonstrate the application of process sedimentology in the interpretation of depositional environments from the study of cores and associated subsurface data. The studies assembled for presentation in the workshop have dealt with sedimentary sequences which have been interpreted as having formed by deposition of non-calcareous, clastic sediment in relatively deep water and also have been concerned principally with coarser deep-water sediments of such stratigraphic sequences because of their potential as hydrocarbon reservoirs. The notes were organized to provide written discussions of the studies in which the cores were used. In addition it was a principal objective of the organizers that each contribution contain subsurface wireline logs and extensive photographic coverage of the whole-diameter core sequences.
Recommendations for the Proper Handling of Cores and Sedimentological Analysis of Core Sequences Available to Purchase
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Published:January 01, 1981
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CiteCitation
Charles T. Siemers, Roderick W. Tillman, 1981. "Recommendations for the Proper Handling of Cores and Sedimentological Analysis of Core Sequences", Deep-Water Clastic Sediments: A Core Workshop, Charles T. Siemers, Roderick W. Tillman, Charles R. Williamson
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Abstract
The detailed sedimentological analysis of whole-diameter cores is greatly enhanced by the core being in good condition; ideally, cores should be complete (100% recovery) and well labeled with all pieces in correct order. Considerable information loss occurs when cores are mishandled; therefore, specific procedures should be followed. At the well site care should be exercised to preserve correct orientation of individual core segments and the core should be properly marked. Hügel orientation grooves cut in the core will facilitate core reconstruction. Commercial core analysis laboratories usually generate the greatest amount of information loss; therefore, special care should be used during subsampling for fluid-saturation analyses and porosity-permeability measurements. A core gamma-ray scan should be obtained whenever possible to aid in later core-to-log correlation. Finally, prior to detailed examination, it is recommended that the core be slabbed, lapped and photographed. X-ray radiography may be needed to enhance subtle sedimentary structures in massive-appearing sandstones and mudrocks.
For proper sedimentological core analysis we recommend a process-sedimentology approach which emphasizes detailed lithologic description and the recognition of genetic units within the vertical sequence. A continuous, detailed sketch should be made and a description made using a check list of important lithologic features. An understanding of Walther’s Law is required for maximum use of the vertical sequence. At least four types of genetic units can be delineated to interprete the physical, biological and chemical processes responsible for generating the sedimentary rock product of the core. Those types are: sedimentation unit, ichnogenetic unit, soft-sediment-deformation (s-s-d) unit, and diagenetic unit.
Finally, the sedimentological core analysis should be used to calibrate the wire-line logs and associated sursurface data. The main steps in such calibration are to first determine the core-to-log depth correction and then to determine the level at which genetic units and lithofacies can be recognized on the logs. Such calibration leads to better correlation of sedimentological information to nearby non-cored wells and allows for lateral extension of predictive sedimentological models throughout the subsurface study area.