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AAPG Bulletin

Abstract


Volume: 52 (1968)

Issue: 3. (March)

First Page: 534

Last Page: 534

Title: Asmari Oil Fields of Iran: ABSTRACT

Author(s): Cedric E. Hull, Harry R. Warman

Article Type: Meeting abstract

Abstract:

The Asmari oil fields of Iran are truly giants, most of them having recoverable reserves greater than 1 billion bbl, in many fields much more than that. The fields are closely packed in a region of relatively constant stratigraphy and structure, and have a common genetic relationship. The individual accumulations occupy very large rock volumes in large-amplitude folds and, although the reservoir properties of the Asmari are poor in terms of porosity and matrix permeability, very high production rates are possible because of extensive reservoir fracturing. These rates can be maintained for very long periods because of the great vertical extent of the oil columns. The Asmari fields are prime examples of anticlinal traps and of the effect of fracturing on reservoir performan e.

The Asmari reservoir is a limestone of Oligo-Miocene age and consists mostly of shallow-water but nonreefal carbonates with a significant sandstone member developing in the northwest part of the area. The Asmari is the uppermost wholly marine unit in a sequence of shelf carbonates interspersed with shale which was deposited, with only minor interruptions, from Carboniferous through Oligo-Miocene time. At the end of the time of Asmari deposition, increasing tectonic instability caused more varied sedimentation; this phase of instability terminated in a strong orogeny which formed the enormous anticlinal traps in this thick sequence of sediments.

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