Karst-Controlled Diagenesis and Reservoir Implications: Example from the Middle Cretaceous Sarvak Formation, Southwestern Iran

Elham Hajikazemi¹, Ihsan Al-Aasm¹, and Mario Coniglio^2
1Earth and Environmental Sciences, University of Windsor, Windsor, ON, Canada
²Earth and Environmental Sciences, University of Waterloo, Waterloo, ON, Canada

The Middle Cretaceous oil-bearing Sarvak Formation forms the main reservoir rocks in many of the oil fields in southern Iran. A wide range of reservoir characteristics in these carbonates resulted from extensive lateral and vertical facies variations that correspond to a greater extent to the effects of subaerial exposure associated with the regional Turonian unconformity. These effects include dissolution, brecciation, development of paleosols and significant bauxite deposits. These features do not extend much below the unconformity both in outcrops and in the subsurface. Field, petrographic and isotopic investigations of various diagenetic phases within these carbonate successions provided strong evidence on the role of karstification on the evolution of reservoir porosity. Geochemical evidence also signifies the lateral and vertical extents and duration of the Turonian paleo-exposure in the study area and the implications on the Sarvak reservoirs in southern Iran. In addition to the influence of paleoexposure on reservoirs characteristics within the Sarvak carbonates, other factors such as relative change in sea level, local salt tectonic effects and paleoclimate may also influenced porosity and permeability within the system.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas