1Department of Petroleum Engineering, Science and Research Branch, Islamic Azad University, Tehran, I.R. IRAN
2IOR Research Institute, National Iranian Oil Company (NIOC), I.R. IRAN
3Research & Technology Directorate, National Iranian Oil Company (NIOC), I.R. IRAN
Obtaining samples that represent original fluid of reservoirs optimizes reservoirs management. The optimized management increases recovery. Also, selecting and performing proper Improved Oil Recovery (IOR) or Enhance Oil Recovery (EOR) programs depend on collecting representative samples. Achieving accurate compositions of original in-situ fluid prevents overdesigning surface facilities. Representative samples cannot be collected from wells which are perforated at the gas / oil contact and are producing non-equilibrium gas. In some cases, samples must be or are collected, when gas coning occurs. There is no standard method for determining accurate original compositions in this situation. We want to discover a method that can estimate original in-situ compositions when gas coning is happened for the first time. Real fluid properties of Iranian oil reservoirs are imported to a synthetic reservoir model that is constructed by a compositional simulator for this purpose. Sampling is performed in the model and methods of determining original in-situ fluid compositions are modeled by detailed Equation Of State (EOS) characterization in the new scheme. In the result an accurate method is found. In this new approach gas coning is not a limitation in sampling even it is a benefit.