Prediction of Subsidence Over Oil and Gas Fields with Use of Influence Functions (Case Study: South Pars Gas Field, Iran)

Withdrawal of oil and gas from reservoirs causes a decrease in pore pressure and an increase in the effective stress which leads to reservoir compaction. Reservoir compaction can be result in surface subsidence through the elastic response of the subsurface layers. To determine the subsidence above a hydrocarbon field, the reservoir compaction must first be calculated, and then, the effect of the reservoir compaction on the surface is modeled. The use of the uniaxial compaction theory is a more customary and accepted method for determining the amount of reservoir compaction induced by pressure depletion. Surface deformation above compacting reservoirs can be efficiently modeled using influence functions. In this paper, Knothe and Geertsma influence functions were used in a simple approach for subsidence modeling of the South Pars gas field. In this approach, we used circular network, called influence network, for determining the whole reservoir compaction effect on the field surface. In addition, the subsidence of the South Pars gas field is modeled using the AEsubs software, and the results are compared to the predicted subsidence by the influence functions.