A New Approach to Estimate Cementation Exponent in Carbonate Reservoirs

There are two approaches for measuring hydrocarbon saturation; well log interpretation and usual developed formulas. Archie’s equation is one of the most fundamental equations for water saturation calculation. Archie’s equation includes three factors Cementation factor, tortuosity and saturation exponent. Archie determines those factors based on lab results in sandstone and provides fixed value for them. Carbonate reservoirs have variety of texture, shape and distribution of pores, therefore mentioned factors, especially cementation are not considered constant. Several methods are presented for calculation of cementation factor continuously. In none of these methods, the Change in the lithology type and conversion of limestone to dolomite is not considered. In this study the relation between cementation factor and density log was examined. Because cementation factor can be defined as a parameter that have a close relation with density. By calculating matrix density and accordance factor between matrix density and cementation factor from core’s analysis, the log will be generated that estimate the variation of cementation factor around the borehole. The regression of calculated values with the core data is 84.09 percent, that shows this method is useable for calculation the cementation factor in carbonate rock.