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Abstract
The world has been faced with the most serious environmental issues which is the global warming of the earth and this is due to the accumulation of greenhouse gases (GHG: H2O, CO2, N2O etc.) generated by human activities (fossil fuel combustion).

Reducing man-made CO2 emission is a key element in mitigating greenhouse gas emission specially CO2. Among the different solutions for CO2 emission reduction such as energy management, use of renewable energies, forestation, the technologies of Carbon Capture and Storage (CCS) into the geological structures has high potential in mitigation of CO2 emissions from anthropogenic sources.

In this paper, after a brief introduction to CCS-EOR technology, the overall quantity of CO2 emission in Iran is introduced as a database. This involves different acid gas sources in petroleum industry and energy section and their high priorities.

Iran has many sour oil and gas reserves and Assalueh gas field is considered as one of the highest priority sources of CO2 in NIOC in terms of both amounts of emission and the possibility of CCS deployment. Carbon dioxide obtained from sweetening of natural gas is considered as a major CO2 source because of its low cost of capturing compare to the other sources.

According to this, assessment for a case study project is done in this field. Selecting optimal structures that match the CO2 underground storage criteria involve many factors like geological, geothermal and hydrodynamic conditions, emission source location, economic, legal issues etc.

Based on theses parameters, this paper investigates possibility of CO2 injection in 24 different geological structures in south of Iran

Introduction
Worldwide, in 2009, 43% of CO2 emissions from fuel combustion were produced from coal, 37% from oil and 20% from gas. Growth of these fuels in 2009 was quite different, reflecting varying trends that are expected to continue in the future.

Currently, coal is filling much of the growing energy demand of developing countries, where energy-intensive industrial production is growing rapidly and large coal reserves exist with limited reserves of other energy sources. Energy Technology Perspectives (ETP 2010) shows that intensified use of coal would substantially increase CO2emissions unless there was a very widespread deployment of carbon capture and storage (CCS).

Due to the fact that Iran is one of the biggest producers of oil and gas in the world, so that the most of CO2 produced is related to these sources of energy which are used in diverse industrial section such as power plants. According to statistical reports, CO2 emissions have increased in two past decades in Iran. Nonetheless, it has a little share of CO2 emission globally (1.7 %) and has a good enthusiasm to decrease emissions. For receiving this purpose, one of the best solutions is CCS.

CCS involves three main stages: Capture, transport and storage. CO2 is captured at large, fixed sources of emission, then concentrated and transported to a suitable storage zone.

The technology for CO2 storage has been in use by oil and gas industry in several locations since 1970s, and worldwide experiences with CO2 storage projects prove that CO2 can be stored safely without leakages.

However if CO2 is used simultaneously for increasing recovery factor and storage in oil and gas reservoirs, it would be the best option. CO2 miscible/immiscible injection can improve oil recovery because it can reduce the fluid and rock interfacial tension (IFT), reduction in oil viscosity and swelling of oil and finally Pressure maintenance.