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Investigation of Low-Salinity Waterflooding in Secondary and Tertiary Enhanced Oil Recovery in Limestone Reservoirs
Ist Teil von
Energy & fuels, 2015-12, Vol.29 (12), p.7781-7792
Ort / Verlag
American Chemical Society
Erscheinungsjahr
2015
Link zum Volltext
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Improved oil recovery from oil-wet low-permeability limestone reservoirs is a great challenge by altering the reservoir rock wettability. The purpose of this study is to compare the results of low-salinity waterflooding in secondary and tertiary modes to decrease the residual oil saturation from limestone reservoirs. Three different stock-tank crude oils and limestone cores are used in this study. All of the coreflooding experiments were performed at 60 °C and 2000 psi by injection of actual formation and seawater, with brine solutions containing single-component salt, such as MgSO4, KCl, Na2SO4, CaCl2, MgCl2, and NaCl, with a wide range of salinity levels. During low-salinity flooding in secondary recovery, the dominant displacement-suggested mechanism is snap-off, which results in an oil recovery factor with different values for the various wettability conditions. The most interesting result is that tertiary low-salinity recovery was never observed in these coreflooding experiments. The measured effect of tertiary low-salinity waterflooding from limestone core experiments was rock dissolution, as a result of surface reactions, and an increase in water relative permeability.