Abstract: Fracture Swarm in Field Analogues of Fractured Carbonate Reservoir (Foreland of the Central Oman Mountains)

DANIEL, J.M., J. LETOUZEY, J.M. MENGUS, J.M. GAULIER

Characterizing fracture patterns variability is a major issue for fractured reservoir simulation in the Middle East. The aim of our surveys in the foredeep of the central Oman Mountains is to study the natural fracturing of reservoir analogues. We gathered data to describe the fracture pattern in relation with faults and folds in the Natih and Shuaiba formations which correspond to major fractured reservoirs in the surrounding region.

In response to the polyphased tectonic of the Northern Arabic platform a complex fracture pattern is observed in anticlines rising through the fill of the foredeep. As a whole, this pattern reveals several preferred orientations that correlate well with core data in nearby reservoirs. Fracture densities are not uniformly distributed in space but fracturing is organized in linear fracture swarms. Their width ranges from 5 to 50 meters with internal fracture densities up to one fracture per centimeter. These geometrical characteristics are strongly controlled by the lithology. Swarms vertical extent critically depends on rheological contrasts between beds. Fault throws do not control their width but outcrop evidences show that they can sometimes be genetically related to faults and flexures. In most cases they are only reactivated by faulting as weakness zones.

Surprisingly, little attention is paid to such tectonic objects in the literature though confrontation with production difficulties indicates that they could be highways for fluids. Based on our field observations we propose some rules to detect and model them in fractured carbonate reservoirs.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria