Define wettability of a formation. Distinguish between water-wet and oil-wet roc
ID: 284342 • Letter: D
Question
Define wettability of a formation. Distinguish between water-wet and oil-wet rocks. Do rocks of different wettability affect oil production? Describe the significance of wettability in designing a waterflood operation for an oil reservoir. What is the preferred wetting phase during water injection? Define the relative permeability of various fluid phases (oil and formation water). How does it differ from the effective permeability? Why are relative permeability values always reported between 0 and 1.Explanation / Answer
(5) Wettability is the ability of a fluid phase to preferentially wet a solid surface in the presence of a second immiscible phase..it depends on the types of minerals present in the rocks and on the composition of fluids in the pores of rocks..
Wettability of a hydrocarbon-bearing rock has a profound effect on the flow of fluids and hence on the oil recovery..it governs not only the distribution of reservoir fluids in the porous media, but also the flow behaviour of oil,water and gas.The performance of reservoir is very much dependent on wettability...for eg. when reservoir is oil-wet as opposed to water-wet, ultimate recovery could be poor. The oil phase tends to adhere to the rock surface rather than flow through the wellbore during waterflooding..
(6) There are three types of permeabilities--
(a) Absolute Permeability defined as the capacity of the rock to transmit fluid, when the only fluid is present..
when there are more than one fluid in rock, Permeability to each phase is called ffective Permeability(measured in millidarcy)...Relative permeability is the ratio of effective to the reference permeability of the rock..
effective perm. is always less than or equal to absolute perm.So relative perm. varies between 0 and 1.
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