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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 5. (May)

First Page: 587

Last Page: 587

Title: Evidence for Migration Along Fractures Within a Fine-Grained Carbonate Rock: ABSTRACT

Author(s): Barry J. Katz

Article Type: Meeting abstract

Abstract:

A detailed geochemical investigation was undertaken to characterize both the soluble (bitumen) and insoluble (kerogen) organic components of DSDP Site 535. This work reveals an organically rich carbonate section of Valanginian to Hauterivian age. This stratigraphic interval contains as much as 11% organic carbon. The kerogen component is dominated by material with elevated atomic H/C ratios, and thus is oil-prone. However, the entire section is thermally immature and has not reached the principal stage of petroleum generation and expulsion. The bitumen component is dominated by nonhydrocarbons (asphaltenes and NSOs) typical of thermally immature sediments. Gas chromatograms of the saturate fraction are also characteristic of thermally immature sediments, revealing a bimod l distribution of components and an abundance of steranes and triterpanes.

Within this limestone section, numerous fractures are filled with a "tar-like" material. Preliminary chromatographic analyses suggest that the "tar-like" character of this material may be the result of post-migration alteration. Also within this interval, chromatographic evidence suggests the presence of thermally mature, unaltered hydrocarbons. Computer modeling of maturity indicates that these mature hydrocarbons seemingly have migrated several tens, if not hundreds, of kilometers updip. The uniformity of physical properties throughout the Cretaceous limestone sequence and the association of these hydrocarbons and "tars" with the fractured and brecciated horizons suggest that the migration occurred along the fracture system.

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Copyright 1997 American Association of Petroleum Geologists