Non-toxic and low-cost amines as wettability alteration chemicals in carbonates

摘要

It is possible to improve the oil recovery from low temperature, oil-wet, and fractured carbonate reservoirs by spontaneous water imbibition using non-toxic and low cost primary amines, R-NH_2, as wettability alteration chemicals added to the injection water. The present paper discusses limitations in the performance of the chemicals like: solubility, pH, carbonate dissolution, and temperature effects. It was observed that C10-amine was compatible with high salinity brine at pH < 7 in the temperature range of 20-70 ℃, but C12-amine was instable at similar conditions. 1.0 wt.% C10-amine dissolved in brine at pH = 6.5 imbibed spontaneously into oil-wet reservoir dolomite cores at 20 and 40 ℃, and the oil recovery varied between 50-75 % of original-oil-in-place (OOIP) depending on the core properties. The mechanism for the wettability alteration using C10-amine is believed to be similar to the previously studied C12TAB system, i.e., desorption of strongly adsorbed carboxylates from the carbonate surface by the formation of ion-pairs. At 70 ℃, C10-amine appeared to fail as a wettability-modifying chemical, probably due to the dissolution of carbonate rock. The concentration of the active component C10-NH_3~+ in the aqueous phase of the pores decreases in a dissolution process. Advancing contact angle measurements on oil-wet calcite crystals confirmed the potential of the C10-amine solution to make the surface strongly water-wet at pH = 6.5 in the temperature range of 20-90 ℃.