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Influence of Pre-existing Basement Templates on the Deformation and Hydrocarbon Systems of the Zagros Simply Folded Belt

Burberry, Caroline *1
(1) University of Nebraska-Lincoln, Lincoln, NE.

Within the Zagros Simply Folded Belt (ZSFB), the majority of trap structures strike NW-SE, from the Fars Zone (Iran) in the southern portion of the belt, to the Mosul High (Iraq) in the north. Hydrocarbon presence within the ZSFB appears geographically constrained into regions where oil fields dominate, or where gas or condensate fields are dominant, frequently with only subtle changes in structural style.

Satellite image analysis is used to derive the trend and spacing of structures along the ZSFB and to identify regions of discontinuity within these trends. These surface maps are then compared to published maps of basement faults and gravity data, where available, in order to test the relationship between surface and deep-seated features. Where possible, the variation in mechanical stratigraphy is included in this analysis using facies maps and well data.

Key observations include the importance of N-S trending basement faults of the Najmah system, dividing the fold belt both structurally and stratigraphically. Such structures mimic the influence of the Kazerun and Izeh faults in the Iranian Zagros. In many cases, faults in this system separate zones of oil or gas fields. Secondly, NW-SE trending basement faults in the Najd system act as the localizing point for major thrust fault development, analogous to the development of the Mountain Front Flexure in Iran, or the location of the Kirkuk Field in Iraq. Thirdly, there is a set of basement-related faults trending NE-SW, which influence the development of structures such as the Mosul High. These three fault sets appear to derive from Precambrian extension of the Arabian Plate.

It is suggested that this previously extended basement behaves as a series of semi-independent blocks during subsequent sedimentation and deformation, causing local but predictable differences in sediment thickness, maturity and structural style. A clear understanding of the location and behavior of basement faults underneath this hydrocarbon province is therefore a valuable predictive tool in exploration.

 

AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain