Selecting a potential smart water for EOR implementation in Asab oil field

摘要

The IFT and contact angle are believed to have direct impact on wettability alteration of crude oil/water/rock systems. In this work, extensive laboratory work was conducted to investigate the effect of these two key parameters on wettability alteration at elevated temperature (90?°C) and ambient conditions. Twenty-six brines representing various scenarios of dilution and sulphate spiking were prepared and tested to identify the smart water most effective in the alteration of wettability. Sea water (SW) was used a base brine. Diluted and sulphate-spiked versions of SW were synthetically prepared following the standard brine preparation procedures. Also standard procedures were followed for the measurement of IFT and contact angle measurements using Teclis tracker. Pendant drop method was implemented to measure the IFT at ambient and 90?°C conditions using a special software package that adopts the axisymmetric drop shape analysis and fits the Laplace equation. The same software package was used to take snapshots of oil drops at 90?°C, and contact angle was measured manually. The effects of dilution and/or sulphate spiking on the observed IFT and contact angle measurements were investigated using a proposed brine categories-based plotting technique. Natural SW and its sulphate-spiked versions have shown the least oil/brine IFT at ambient and 90?°C conditions. The sulphate-spiked SW and its dilutions have resulted in the reduction in oil/brine IFT, whereas the diluted SW showed an increase in oil/brine IFT. Further reduction in IFT was observed at the elevated temperature. SW and SW/50 (50 times diluted sea water) were the only two brines that could yield a contact angle of 113° and 114°, respectively, indicating the change in wettability from oil-wet to the border line of intermediate-wettability conditions. The natural SW that contains 3944?mg/L of sulphate ion has been found to be the most effective in promoting wettability change and thus represents the selected smart water for EOR implementation in Asab oil field. The contact angle measurements were made from the drops formed by the natural drainage process. These measurements are believed to duplicate contact angles in the selected reservoir because of the continuous change in fluids saturation.