Resumen de Permeability variation modeling and reservoir heterogeneity of Bangestan carbonate sequence, Mansouri oilfield, SW Iran
Bahman Soleimani, M. Moradi, Ali Ghabeishavi, A. Mousavi
Reservoir permeability and other property variations were investigated in all nine zones of the Bangestan carbonate sequence in the Mansouri oil field located in the southwestern of Iran. The prepared permeability distribution models using RMS method indicated that there are two abnormal high-permeability zones located at the northwestern in Zone 2 and southeastern in Zone 6 of the reservoir. Core data analysis and petrographic thin-section study, electrofacies model, and fluid saturation measurements were used to verify the results of permeability models. Petrographically, the main constituents of the Bangestan carbonate sequence were wackestone and packstone facies. Based on five determined microfacies confirmed the environmental instability from open marine to semi-restricted lagoonal environments while understudied carbonate deposition. Diagenetic processes such as solution (pressure and chemical), dolomitization, and fracturing improved the reservoir quality. Electrofacies (EF) model was also done by gamma ray (GR), water saturation (Sw), acoustic log (DT), neutron porosity, and effective porosity (PHIE) data. Four EFs were determined and reservoir quality was decreased from EF-1 to EF-4. The results showed that the vuggy porosity abundances and electrofacies distribution, as the main controllers of the reservoir quality, are well coincident with the permeability model. The vuggy porosity type was found to be as a fabric selective pore and an individual character of rudist-rich zones. Fluid saturation data are consistent with the permeability model and related high reservoir quality and production zones. The detected anomalies of permeability in the model can be interpreted by three scenarios: (1) basement faults activities, (2) sedimentary environment changes, and (3) combinational effects of faults and sedimentary deposition. It is believed that the third scenario is more logic.
