A Variable Cementation Exponent, M, For Fractured Carbonates

This paper develops the theory and necessary equations to determine Archie's cementation exponent, M, for a carbonate reservoir containing vuggy porosity interconnected with a fracture system. The area of study is the Bluell section of the Mission Canyon formation in the Flaxton Field, Williston Basin, which is operated by Monsanto Oil Company. This study supports the work of R. Aguilera, 1980, who has shown M to decrease as the percentage of fracture porosity increases. This study is unique in that a method has been devised to measure a volume of interconnected vuggy and fracture porosity from conventional well logs. This allows a point-by-point calculation of M. This technique has been used to locate hydrocarbon-bearing intervals where conventional parameters in Archie's equation predict water. The results are supported with core and production data.