Perpustakaan Digital ITB

This study investigates NaOH, Na2CO3 and their combination as salinity adjustment agents in a linear alkylbenzene sulfonate (LAS)-based surfactant system for low-TAN (0.13 mg KOH/g) crude oil recovery from the Tarakan Basin, Indonesia. Due to the low TAN, the alkaline function primarily via divalent-ion precipitation rather than in-situ saponification. Formulation screening and optimization were performed at 65.5 ?C in synthetic brine (TDS = 10,240 ppm). Although initial screenings of 22 formulations yielded interfacial tensions (IFTs) below the pure base brine (1.43 mN/m) but above the ultralow IFT threshold, subsequent salinity optimization with NaCl identified an optimum formulation (18B: 1.5 %wt Na2CO3 + 0.5 %wt LAS + 5,000 ppm NaCl, with TDS = 30,240 ppm). This system achieved an ultralow IFT of 4.95?10-3 mN/m and microemulsion Winsor Type III in phase behavior test with solubilization ratios (Vo Vs ? = Vw Vs ? = 1.96 mL/mL). Additionally, the blended alkaline system exhibited superior optimization robustness due to the complementary precipitation of Mg2+ and Ca2+ . Spontaneous imbibition tests on Berea sandstone cores increased the recovery factor from 16.97% to 42.73%, proving that alkaline- mediated salinity adjustment is an effective chemical EOR strategy for low-TAN, divalent-rich reservoirs.