Analyzing well logs from carbonate formations is difficult because of the problem in estimating the cementation exponent (m) and calculating correct porosities in complex lithologies. Generally, determining lithology can be accomplished using multiple porosity crossplots. If the pore type is known or can be determined from well logs, m can be calculated more accurately using variable m models based upon pore type. A series of logging crossplots can be used to determine the appropriate pore type. Whether the zone is wet or productive can be estimated through the use of several hydrocarbon indicating crossplots. This paper outlines the general analysis for carbonates including estimating lithology and pore type, determining hydrocarbon presence, and computing porosity, m, water saturation, and net pay. An example from the Montoya Lime illustrates the procedure.

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