Carbonate Reservoir Characterization: Part 09
1. Can we comfortably apply Archie’s second law for estimating water saturation in a carbonate reservoir as a function of water resistivity and porosity?
2. Can we comfortably make use of Pickett plot for estimating water saturation in a carbonate reservoir by establishing unit water saturation trend?
3. To what extent, the conventional porosity/lithology cross-plots used to determine lithology in a carbonate reservoir contains ‘gas’ also in the pore fluids, in addition, to the presence of mineralogy components including dolomite, limestone, anhydrite, gypsum, salt, and chert?
4. How easy a reservoir management plan in a carbonate reservoir will be – with reference to
(a) Whether the reservoir rock and fluid properties are accurately defined? (b) What is the maximum and optimum number of wells to be drilled?
(c) Where exactly the wells should be located?
(d) how exactly the wells need to be drilled – horizontal/vertical/inclined?
(e) how exactly the wells need to be completed?
(f) how exactly the recovery factors be optimized?
(g) how exactly the reservoir pressure will be maintained as a function of time?
(h) when exactly secondary recovery or water-flooding need to be introduced, if required?
(i) when exactly tertiary recovery processes need to be introduced?
(j) what will be the initial investment?
5. How easy would it remain to characterize a highly undersaturated carbonate oil reservoir (where, the saturation pressure remains to be lower, by an order of magnitude or more, than formation pressure with a low solution GOR)?
6. How easy would it remain to characterize a moderately undersaturated carbonate oil reservoir in the absence of any free gas gap?
7. How easy would it remain to characterize a moderately undersaturated carbonate oil reservoir with initial free gas gap?
How lower could the saturation pressure be than the formation pressure – for an efficient oil recovery?
8. How easy would it remain to characterize a saturated carbonate oil reservoir with initial free gas gap (where, initial reservoir pressure equals saturation pressure; and, where, no retrograde condensation occurs in the gas cap with the reduction in reservoir pressure)?
9. How easy would it remain to characterize a saturated carbonate oil reservoir in the absence of free gas gap (where, the reservoir pressure is initially at the bubble point pressure of oil)?
Suresh Kumar Govindarajan
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