Integrated Structural, Sedimentological and Diagenetic Evaluation of Fault Related Dolomite, Hammam Faraun Fault Block, Suez Rift, Egypt

Fluid flow along fault and fracture systems within carbonate reservoirs, particularly in the burial environment, is a complex process with the distribution of diagenetic products and secondary porosity often controlling reservoir heterogeneity. Predicting the distribution of these products is a major challenge, which requires the origin, composition and timing of fluid flux is understood within the context of the tectono-stratigraphic evolution of the basin.

The project is focussed on the Hammam Faraun Fault, a major block-bounding normal fault, associated with extension in the Suez Rift during the Miocene. Dolomite bodies occur in the footwall of the Eocene Thebes Formation, a Deepwater, carbonate succession that comprises debris flows, slope grain flows and turbidites embedded within pelagic wackestones and mudstones.

Dolomitisation appears to occur in three main bodies: (a) massive vertical to sub-vertical discontinuous sheets, (b) laterally extensive stratabound bodies, (c) dolomitised debris flows. Dolomite texture variability occurs both within and between the different dolomitised bodies. Integrating field and petrographical observations of the various dolomite bodies, the dolomitising fluid migration pathway can be attributed to the major fault trends within the study area. In some examples, pervasive dolomitisation is observed along the hanging-wall of NE-SW faults, with partial or no dolomitisation along the footwall. As well as the syn-tectonic related dolomite bodies, an earlier phase of dolomitisation is recognised, particularly within the clasts of the debris flows.

This presentation will focus upon the petrography and geochemistry of the dolomite within individual dolomite bodies, and preliminary data interpretations of the source of dolomitising fluids, the timing of dolomitisation and the mechanism for replacement of the host limestone. The relative timing of key diagenetic products within the context of the depositional and structural evolution of the fault block will be discussed and their effect upon porosity and permeability evaluated.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California