Журнал нефтяной и экологической биотехнологии

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Rock Typing by Bulk Volume Water Method in the Carbonate Reservoirs

Zahra Riazi

Rock typing is a part of the reservoir characterization process that is carried out after the data acquisition stage of field development. Permeability, porosity, initial water saturation, and Mercury Injection Capillary Pressure (MICP) account as the main data, which are applied during this process depends on the method. Permeability is the most common input data in most rock typing methods and can distinguish different types of conduits in the sandstones. Despite this, its data source is limited to few reservoir intervals and wells, regardless of time and cost of its laboratory works. Moreover, feeding outcomes of rock typing to a static or dynamic model using either different correlations or neural network methods is challenging and imposes more uncertainties to the models, especially for carbonates.

At the same time, applying irreducible water saturation and porosity as the easily attainable data in the Bulk Volume Water (BVW) method makes it an adequate method for rock typing, while its outcome is straightforward to feed models for both carbonates and sandstones. This method was considered as an axillary method in the literature and this paper examined it as a standalone rock typing method for three carbonate fields using a MATLAB code. The Reservoir Quality Index (RQI) method was also applied for rock typing in these fields as a permeability-based approach and both were verified through MICP curves classification. Outcomes revealed a satisfactory match between categorized rock types by BVW method and their related grouped MICP curves. Comparing two methods, the BVW method classified carbonates to the fewer rock types and the grouped MICP curves presented less variations. Achieving satisfactory clustering for the MICP curves presented the BVW method as a suitable approach for rock typing in the three carbonate fields. Therefore, it can be an appropriate method for carbonates with low porosity and permeability correlation coefficient due to existing secondary porosity and different scales of heterogeneities in their nature.