An Overview of Heavy and Extra Heavy Oil Carbonate Reservoirs in the Middle East

John W. Buza
Kuwait Oil Company, Ahmadi, Kuwait

Global heavy oil resources in carbonate rocks have been estimated to be on the order of 1.6 trillion barrels, of which about one-third may occur in the Middle East. Owing to its vast light oil reserves, documentation in the public domain on Middle Eastern heavy oil accumulations is far from complete but enough information is available to assemble a reasonable picture of the geological setting, reservoir and oil quality issues and the status of cold and EOR production in the region. Productive heavy oil carbonate fields can be grouped into two categories: 1) low matrix permeability, fracture dependent and 2) matrix permeability dependent production. Fracture enhanced, low matrix permeability production is dominant and occurs in Oman, Iran, Iraq, Syria, Turkey and Egypt and includes producing fields such as Qarn Alam in Oman and Issaran and Bakr-Amer in Egypt. In Iran, several fractured carbonate fields have successfully cold tested oil qualities on the order of 10 degree API. Wafra, located in the Divided Zone of Kuwait and Saudi Arabia, is the most notable example of an accumulation that has ample matrix permeability to allow economic cold production without significant fracture enhancement. Several types of EOR have been implemented in the region. A CO₂ flood is in place at Bati-Raman in Turkey, a crestal steam injection at Qarn Alam and a pilot steam flood was initiated at Wafra in February 2006. These three fields, along with Issaran where steam is planned in the future, constitute the bulk of carbonate heavy oil production in the Middle East.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece