It is notable that over the past decade, proven reserves of natural gas have dramatically increased as higher prices and advances in technology have turned previously unrecoverable resources into major sources of domestic production. Moreover, the decline in crude oil reserves has significantly slowed over the past decade. Therefore, there would be an end to the conventional hydrocarbon resources sooner or later and, in the meantime, global natural gas consumption is projected to grow 52% from about 108 Tcf in 2009 to about 163 Tcf in 2030, which is an annual increase of almost 2%. In addition, since natural gas combustion produces less CO2 than coal and other petroleum products, governments are encouraged to use it as an alternative to other fossil fuels to reduce greenhouse gas emissions. Shale gas accumulations, with a unique all in one nature, where all petroleum system elements reside in just one lithology, have become the focus of gas exploration strategies after recent successes in the Barnett Shale gas production. Meanwhile, significant advances in drilling and stimulation technologies have made gas shale attractive for development in many countries including Iran. The unconventional gas resources such as coal bed methane and gas trapped in shale are growing in importance. Such estimated reserves account for approximately 18% of total proven gas reserves. Shale formations in particular offer enormous potential for future production. This study compares several shale gas resources in different areas and highlights the possible potential unconventional resources in Iran.
. Vanden Berg M.D., 2008a, Water-related issues affecting conventional oil and gas recovery and potentialoil shale development in the Uinta basin, Utah: Technology Status Assessment: Utah Geological Survey (http://www.netl.doe.gov/technologies/oilgas/ publications/EP/NT05671_TSA.pdf) (accessed October 22, 2009).
. USGS, Assessment of in-place oil shale resources of the Green River formation, Piceance basin, Western Colorado: USGS, 2009.
. Vanden Berg M.D., 2008b, Basin-wide evaluation of the uppermost Green River formation›s oilshale resource, Uinta basin, Utah and Colorado: Presentation at the 28th Oil Shale Symposium, November 2008 (http://geology.utah.gov/emp/oil shale/pdf/oil shale1108.pdf) (accessed October 22, 2009).
. Kamali M.R. and Ghorbani B., Organic Geochemistry- From Phytoplankton to Production, Ist Ed., Arianzamin Publication, 2006.
. Assereto R.: The Jurassic Shemshak formation in
Central Elburz (Iran). Riv. Ital. Paleont. Strat., 72, 1133-
. Rahimpour-Bonab H., Zamani Z. and Kamali M.R., Source Rock Evaluation of Shemshak Formation in the Central Alborz Basin: A Preliminary Investigation, Iranian Int. J. Sci. 3(2), pp. 235-262, 2002.
. Afshar A., Preliminary Geological Note on Oil Shale Deposits of Ghali Kuh, NIOC-G.N. No. 264, 1975.
. Kamali M.R. and Rezaee M., Unconventional Hydrocarbon Reserves, 14th Intl. Oil, Gas and Petrochemical Conference, Tehran, 2010.