Investigation of Porosity Effect to Determine Uncertainty in Archie's Water Saturation Equation Parameters, Case Study: Two Reservoir Formations from an Iranian Oil Field

Formation A and Formation B are main reservoir intervals in one of the Iranian oil fields which were considered for uncertainty study. Uncertainty in calculated water saturation has a direct economic impact on both exploration and development projects, yet is rarely quantified by petrophysicists.Cementation factor (cementation exponent) is one of the most important parameters in saturation equation to determine the water or hydrocarbon saturations. It acts as a power of porosity in the most of saturation equations which increases the importance of this parameter.Monte-Carlo Simulation and @Risk software was used for uncertainty analysis. Four different scenarios were assumed and different models were run for each zone. The results show that cementation factor is highly important in saturation calculations and small variation in cementation factor values can affect the results of water saturation determination considerably. Also in high porosity zone Shell formula is a suitable equation for calculation of cementation factor (m), but in low-porosity zone using a constant value for cementation factor is better than using Shell formula.

Keywords:

Cementation Factor , Monte-Carlo method , Porosity , Uncertainty analysis