Carbonate Reservoir Characterization: Part 03
1. In a typical carbonate reservoir, does the saturation of a non-wetting phase depend on any other function than (a) the interfacial tension between non-wetting and wetting phases; (b) the adhesive forces between the fluids and the minerals that make up the pore walls; (c) the pressure differential between the non-wetting and wetting phases; and (d) pore-throat size?
2. In general, the pressure differential between non-wetting and wetting phases (capillary pressure) is produced by the difference in density between non-wetting and wetting phases resulting from buoyancy effect (produces pressures in hydrocarbon column). If so, in a carbonate reservoir, whether the pressure in the wetting phase will remain to be equal to the difference between (a) the reservoir pressure @ zero capillary pressure; and (b) the height above the zero capillary pressure times water density?
3. Whether the pressure gradient in a carbonate reservoir (measured from repeat formation tester or a wireline formation tester) be used to estimate the distance above the zero capillary pressure level?
4. In a fractured carbonate reservoir, whether, the pressure difference between the oil phase and water phase would remain to be equal to the difference between the specific gravity of the two fluids multiplied by the height of the oil column @ any given height in an oil column?
5. Would it remain feasible to deduce the base of a carbonate reservoir either by using drainage curve or by using imbibition curve?
6. Which of the following geological conditions remain to be very sensitive in generating fractures along with fracture spacing, fracture width and fracture dip: (a) depth of burial; (b) thickness of beds; (c) changes in lithology; (d) local stress field including the amount of differential stress considering mechanical discontinuities; (e) physical/chemical/mechanical properties of rocks and fluids in the pores; (f) rate of over-burden loading/unloading; and (g) gravitational compaction?
7. Permeability being dependent upon both volume of the rock sample and orientation, how do we take into account the influence of fractures and stylolites – present in the core samples - during permeability measurement? How exactly a carbonate reservoir formation needs to be sampled before using it for experimental investigations @ laboratory-scale?
8. Feasible to have a direct relation between porosity and permeability in the absence of having pore-size distribution in a carbonate reservoir?
9. How exactly to treat a carbonate reservoir system having a distinct fracture permeability and a matrix permeability?
Suresh Kumar Govindarajan
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