Investigation of cementation exponent (m) in heterogeneous carbonate reservoirs via integration of thin section analysis and well logging

摘要

Cementation exponent (m) is one of the most important parameters in calculation of water saturation from Archie's equation especially in heterogeneous carbonate reservoirs. The complexity and wide variations in the nature of pore systems in these reservoirs causes the cementation exponent to be variable with depth and ignoring this variation will lead to significant errors in calculation of water saturation and hydrocarbon in place. In this paper, cementation exponent is determined by using an improved triple porosity model developed by Aguilera (2004). Pore systems are characterised in a 150 metre interval by preparing 64 thin sections from the core plugs for petrographic analysis. Pore types are classified via microscopic analysis of sections followed by an image processing approach. Calculated m-values are used to predict water saturation and the results are compared to core data. It is observed that Archie's equation successfully predicts water saturation of this heterogeneous medium if appropriate m-values from improved triple porosity model are used.