Automating sandstone acidizing using a rule-based system
Journal of Petroleum Exploration and Production Technology
An expert system for automating sandstone acidizing has been developed in this study. The system consists of six stages, which were built following an acidizing logic structure that is presented in the form of decision trees. The six stages consist of formation oil displacement, formation water displacement, acetic acid, HCl pre-flush, main acid, and over-flush stage. The acid blends recommended by the system are damage-type specific, and account for the compatibility between the injected acid
... the injected acid and the in situ crude in order to avoid formation of asphaltene sludge, or emulsions. The acidizing expert system has been implemented as an online web-based application. Applicability of this expert system to acidizing design has been illustrated using three documented actual field cases spanning the Niger Delta region, Algyo Oil field in Hungary, and the Dulang oil field in Malaysia. For Niger Delta field and the Algyo field cases the expert system produced an optimal main acid job design with recommended preand post-flushes that are in perfect agreement with successful field treatment. For the Dulang oil field, in actual practice, an organic clay acid was injected for removing problems of fines migration in a reservoir that has a high calcite content, with a moderate amount of feldspar and chlorite clay. The acidizing expert system recommended a chelant-based acid, which is a recent innovation that is considered a more cost-effective acid solution for dissolving fines in presence of calcite and other sensitive clay minerals.