--> ABSTRACT: Analysis and Modeling of Fractures in Middle East Reservoirs, by Roy Nurmi, Martin Waterhouse, and Mahmood Akbar; #91030 (2010)

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Analysis and Modeling of Fractures in Middle East Reservoirs

Roy Nurmi, Martin Waterhouse, Mahmood Akbar

The primary approach for the detection and geometrical analysis of fractures in Middle East reservoirs is borehole electrical imagery. These images provide details of even very fine fractures and bedding, which help in distinguishing natural from induced fractures. The geometrical analysis of fractures defined by imagery is done either using plastic overlays for a quick approximation or using an interactive computer work station for a more accurate analysis.

Routine fracture characterization by borehole imagery is aiding optimum development of fracture reservoirs in the Middle East. Log summaries of fracture intensity and aperture width, which are correlated with lithology, porosity, and fluid evaluations, are used in the design of well completion programs. Geometrical analyses of fractures in images have allowed some companies to appropriately alter their well patterns and to determine what borehole trajectory will intersect the maximum number of open fractures. In addition, fracture logging and tectonophysical modeling provide a guide to well testing efforts which are used to quantify the large-scale effects of fractures in a reservoir.

Conceptual and tectonophysical models of probable fracture characteristics are needed in order to understand fracture distribution throughout a reservoir.

To assist model development, a map showing Middle East areas containing fractures of similar origin was constructed using the following classification: (1) Orogenic belts where fold-related fractures dominate with a lesser number of fault-related fractures. Stearn's classification of fracture types does not distinguish between fold and fault-related fractures. (2) Shear zones are dominated by fault-related fractures. (3) Platforms with gentle anticlines may have regional and/or tectonic fractures. (4) Deeply buried formations of reactivated anticlines are dominated by fold-related fractures. (5) Domes over deeply buried salt structures have radial and/or preferred fracture orientations. (6) Evaporite dissolution areas often have fractures and brecciated zones associated with collapse. Outcrop examination and case studies have also provided an insight into the nature of reservoir fracturing within each of these settings.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.