INVESTIGATION OF CRUDE OIL-BRINE-ROCK INTERACTION USING LOW SALINITY WATER AND TIO 2 NANOPARTICLES: IMPLICATIONS ON THE SURFACE CHARGE AND THE INTERFACIAL PROPERTIES THESIS Submitted to partial fulfillment to obtain a master’s degree from Bandung Institute of Technology By SEKAR INDAH TRI KUSUMA Student ID Number: 22222001 (Master’s Program in Petroleum Engineer) BANDUNG INSTITUTE OF TECHNOLOGY January 2025 i ABSTRACT INVESTIGATION OF CRUDE OIL-BRINE-ROCK INTERACTION USING LOW SALINITY WATER AND TIO 2 NANOPARTICLES: IMPLICATIONS ON THE SURFACE CHARGE AND THE INTERFACIAL PROPERTIES By Sekar Indah Tri Kusuma Student ID Number: 22222001 (Master’s Program in Petroleum Engineering) The application of Low Salinity Water (LSW) as an injection fluid for enhanced oil recovery has attracted much attention due to its ease of application, environmental friendliness, and more economical cost. It became popular after previous studies discovered that low salinity conditions are more effective than high salinity conditions for recovering the remaining trapped oil in the reservoir. Through several mechanisms, LSW modifies the surface charge and interfacial properties of the crude oil-brine-rock (COBR), yielding more oil to be recovered. Combined with nanoparticles (NPs) as enhancing agents, the LSW-NPs nanofluid can improve the oil sweeping efficiency compared to LSW alone. Titanium Dioxide (TiO 2) as nanoparticles has various advantageous properties, including high stability, low cost, and environmentally friendly (non-toxic) properties. However, the experimental data discussing the compatibility between LSW and TiO 2 remains underreported, and the COBR interaction using the combination of LSW-TiO 2 has been quite unexplored. This study aims to investigate the COBR interactions at various brine salinity of NaCl single salt (LSW of 500, 2000, 8000 ppm brine and compared it to 32000 ppm high salinity water) and combined it with TiO 2 at low concentrations (0 ppm – 100 ppm). Each nanofluid is characterized by measuring its pH, conductivity, and zeta potential. The impact of salinity and TiO 2 concentration on the interfacial tension and contact angle are also investigated using the light crude oil from Tempino Oilfield and the thin sections of Berea Sandstone samples. The XRD (X-Ray Diffraction) and AFM (Atomic Force Microscope) analysis are first conducted before the contact angle measurement to characterize the rock's mineral composition and surface roughness of the thin sections. The results suggest that TiO 2 addition can reduce the contact angle from 63.5° using 32000 ppm NaCl brine to 27.9° using 500 ppm NaCl brine and 100 ppm TiO 2. On the other hand, the TiO 2 addition on LSW does not change the interfacial tension of crude oil-brine significantly. In terms of stability, TiO 2 NPs are more stable at low salinity compared to high salinity conditions. However, this study observed the linear correlation between the zeta potential and contact angle, at which the higher ii zeta potential value correlates to the higher contact angle. The zeta potential represents the surface charge of the nanofluid, whereas the contact angle represents the nanofluid-rock interfacial properties. These findings can increase our understanding of the mechanism behind TiO 2 addition to LSW and help us formulate the most beneficial concentration of LSW- TiO 2 nanofluids to maximize oil recovery from subsurface formations. Keywords: Low Salinity Water, Titanium Dioxide Nanoparticles, Interfacial Tension, Zeta Potential, Contact Angle. iii ABSTRAK INVESTIGASI INTERAKSI CRUDE OIL-BRINE-ROCK MENGGUNAKAN AIR BERSALINITAS RENDAH DAN PARTIKEL NANO TIO 2: IMPLIKASI TERHADAP MUATAN PERMUKAAN DAN SIFAT ANTARMUKA Oleh Sekar Indah Tri Kusuma NIM: 22222001 (Program Studi Magister Teknik Perminyakan) Aplikasi Low Salinity Water sebagai fluida injeksi pada peningkatan perolehan minyak lanjut telah menarik banyak perhatian karena aplikasinya yang mudah, ramah lingkungan dan harga yang lebih ekonomis. LSW menjadi populer setelah penelitian-penelitian sebelumnya menemukan bahwa kondisi salinitas rendah lebih efektif dibanding kondisi salinitas tinggi dalam menghasilkan sisa minyak yang terjebak di reservoir. Melalui beberapa mekanisme, LSW memodifikasi muatan permukaan dan sifat antarmuka pada crude oil-brine-rock (COBR), untuk menghasilkan lebih banyak pengangkatan minyak.