A structured approach for the diagnosis of formation damage caused by organic scale deposits and surface active agents, Part II: Expert system development

This paper (Part II) reports on the development of a Formation Damage Expert System (FODEX) for aiding in the preliminary diagnosis of formation damage types that consist of emulsions, water blocks, wettability reversal and the deposition of asphaltenes and wax in hydrocarbon reservoirs. The reasoning process is based on compiled rules that have been arranged in decision trees constructed using knowledge derived from standard industrial practices integrated with empirical models to assure vigorous expert opinion. The structured approach for formation damage diagnosis has been detailed in Part I of this work. FODEX automates the reasoning process embedded in the decision trees using logic blocks represented as four modules. Fuzzy logic has been used in handling incomplete and conflicting knowledge encountered in determining the likelihood of asphaltene and wax deposition. The developed formation damage expert system has been tested with three documented field cases of producing wells in the Rangely, Typhoon, and Magwa-Marrat oil reservoirs. FODEX decisions regarding the type of damage inflicted on these fields have been validated with compositional PVT simulation software. The expert system made a thorough diagnosis of damage types, in agreement with PVT simulations, field observations, PVT cell testing and special core analysis.