Carbonate reservoirs present both opportunities and challenges, especially in rocks that contain multiple, heterogeneous porosities. This study addresses a large carbonate reservoir with complex porosity types including porous matrix, fractures, faults, and vuggy zones. A fracture-focused strategy considers how these porosities behave in oil production, and uses this understanding to improve reservoir productivity.

The subject of this work is a major carbonate reservoir that was initially developed by conventional methods. These approaches emphasized matrix properties using petrophysically-interpreted wireline logs. The early stages of production, which did not include pressure maintenance, found anomalous behaviors that were inconsistent with a matrix-only reservoir. The existing petrophysical data, which are valid only for porous rock, could not address fracture-based hypotheses.

A program of fracture studies supported a re-analysis of the production strategies in light of reservoir's observed behaviors. The fracture-focused strategy employed FMI image logs along with production logs (PLT surveys) and temperature surveys. These well-based tools identified the locations of flow and their associated geologic features, which are appeared to be mainly fractured and vuggy horizons. Coring activities validated the FMI interpretations.

A reexamination of well tests using supported a single-porosity, fracture flow model. Pressure derivative interpretations using fracture-based conceptual models associated well performance with geologic features, including both the vuggy zones and faults.

The fracture-focused characterization program has developed improved conceptual models of the reservoir to support evolving production approaches including well acidizing, and other. The paper provides examples of successful well operations performed after appropriate field research.

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