Rock typing and reservoir zonation based on the NMR logging and geological attributes in the mixed carbonate-siliciclastic Asmari Reservoir

Determination of rock types in hydrocarbon reservoirs results in more accurate reservoir modeling and gridding. Most of rock typing methods restrict to some aspects of the studying rocks, by which minor attention is taken to factors such as multi-scale and multi- modal pore types and sizes, sedimentary textures, diagenetic modifications and integration of dynamic data. Rock typing of a mixed carbonate-siliciclastic reservoir by integration of its static and dynamic behaviors and sedimentary textures is practiced here as an effective technique for reservoir characterization. Porosity, permeability and pore size distributions are investigated as the static behavior and capillary pressure, water saturation and irreducible water saturation as dynamic behavior of the rocks. Results from the analysis of core data in available intervals and continuously NMR data through the whole well of the studying reservoir are involved in this study. Initially, based on the Flow Zone Index method, while considering geological attributes, 7 rock types are determined. Next, the petrophysical properties of the rock types including capillary pressure, water saturation and irreducible water saturation are combined into the rock types. Afterward, pore types, facies characteristics, texture and diagenetic overprints are involved in the rock type’s classification to capture spatial trends and relationships. Due to the close relationship between depositional sequences and diagenetic processes, the defined rock types are tracked in the sequence stratigraphic framework. Using the mentioned parameters, the rock types are defined in the cored intervals and then predicted in non-cored intervals by NMR data. The rock types are established to provide a clue on the high and low permeable zones and to apply for more accurate reservoir zonation.