This study has been done on one the southwest Iranian oil field. The main purpose is to find some evidence in order to assess lateral/ vertical reservoir compartmentalization using in enhanced oil recovery (EOR) studies. The Bangestan reservoir in the studied field contains Ilam and Sarvak formations. The Sarvak formation has better reservoir features and its produced oil is much more than Ilam, that’s why the Sarvak is chosen for lateral compartmentalization assessment. In order to assess vertical compartmentalization, similarities and differences investigate between Sarvak and Ilam formations. So, the integration of several data including reservoir- fluid, geology, 3D seismic, petrophysics and geochemical assessment have been employed. First of all, the target wells were selected based on previous studies and data. Reservoir- fluid data including reservoir pressure, saturation pressure, API density and gas-oil ratio (GOR) indicate the significant differences between these two layers, whereas differences in lateral investigations (among Sarvak formation) are moderate. The geochemical analyses (elemental analysis, gas chromatography, gas chromatography-mass spectrometry and detailed hydrocarbon analysis), confirm the differences between the formations. Although, the biomarker data indicate oil samples of both formations derived from open marine environment source rock, the source rocks lithology of Sarvak and Ilam oil samples are shale and carbonate, respectively. On the other hand, the thermal maturity of Sarvak oil samples are considerably higher. When it comes to lateral assessment, there is an obvious similarity between Sarvak oil samples in the source rock lithology, however the maturity is various in some especial areas. According to the geology investigations, the differences in API and some maturity parameters in Sarvak are related to heat flow from basement fault(s) and paleo-high activity. There is a close correlation between the distribution of porosity, permeability which result from previous modelling studies and the distribution of maturation, API density, that this correlation confirm the heat flow. Elemental analysis indicates the kerogen of Sarvak oil samples is type ?and Ilam oil samples is generally type ?with a little tendency to type ?, and these results correlate strongly with biomarkers figures. Detailed hydrocarbon analysis as a complementary geochemical method to GC-MS has been used. Also, the mentioned analysis confirms the differences between oil samples of Ilam and Sarvak layers, in contrast it indicates low- moderate changes between Sarvak oil samples (lateral assessment) that it could be related to some reservoir alteration in Sarvak. These consequences prove the vertical compartmentalization between Sarvak and Ilam layers. Finally, in order to assess the connectivity between different parts of zone 6-1 from Sarvak, and suggest the proper areas to drill EOR wells, MRST simulation has been done. As a result of the simulation, it has determined the connectivity of the zone has fluctuated heavily. According to the non-fault reservoir (based on 3D seismic data), so it seems it is caused by stratigraphic heterogeneity. As regards the mentioned results in previous sections about some differences in Sarvak (lateral assessment), there is a suitable correlation between MRST consequences and them. In result, there is a lateral compartmentalization with a poor connection in some parts, particularly in northwest of Sarvak.