Abstract

Seventy nine HPMI (high pressure mercury injection) derived saturation height function curves are used to create nine different capillary bundles for Minagish Oolite carbonate reservoir. Each capillary bundle is tied up with its sedimentological and petrophysical attributes to create a discrete pore type/porefacies. The best pore type (Type 0) has well connected pore throat with lesser tortuosity as represented by very low entry point, low irreducible water saturation (Swirr) and wide plateau of the function curve. The worst one (Type 8) is very fine pore throats with high restriction of flow due to high entry point and very high irreducible water saturation. Good porefacies (Type 0, 1 and 2) represent mostly intergranular pore dominated samples, not much affected by subsequent cementation and dissolution. Intermediate pore types (Type 3,4 and 5) are found to have both primary intergranular and secondary solution rich pore spaces. The bad porefacies (Type 6,7 and 8) are either mud dominated or highly cemented rocks with restricted pore spaces. HPMI based poro-perm clusters are also used to create porefacies in the uncored wells and subsequently populated in 3D grid using variogram. Saturation height function of each representative capillary bundle is then used to tie the saturation value of individual porefacies along the well path in more than 250 wells. The newly constructed saturation grid is well tied with specific pore type of each facies and thus suitable to explain the fluid flow behavior within the reservoir. Well wise production behaviour and certain issues of anomalous production rate as well as water cut are satisfactorily explained through this workflow.

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