Assessment of South Pars Gas Field Subsidence Due To Gas Withdrawal

Withdrawal of oil and gas from reservoirs causes a decrease in pore pressure and an increase in effective stress which results to a reservoir compaction. Reservoir compaction will result in surface subsidence through the elastic response of the subsurface. Usually in order to determine the subsidence above a hydrocarbon field, the reservoir compaction must be first calculated and then the effect of this compaction on the surface should be modeled. The use of the uniaxial compaction theory is more prevalent and an accepted method for determining the amount of reservoir compaction. But despite of the reservoir compaction calculation method, there are many methods with different advantages and shortcomings for modeling of surface subsidence. In this study, a simple analytical method and semi‌-analytical methods (AEsubs software) were used for modeling of the surface subsidence of the South Pars gas field at the end of the production period