INVESTIGATION OF SURFACE CHEMISTRY, MICRO-TOPOGRAPHY, AND WETTABILITY ALTERATION OF SILICA-ASPHALTENE INTERFACE IN ABSENCE AND PRESENCE OF ZNO AND SIO2 NANOPARTICLES AND A NOVEL ZNO-SIO2-THIAZINE NANOCOMPOSITE USING ATOMIC FORCE MICROSCOPY AND X-RAY PHOTOELECTRON SPECTROSCOPY

Abstract

Silica is a primary component of sandstone reservoirs; a very important class of petroleum reservoirs. Presence of asphaltene can modify the surface chemistry of the silica made rocks leading to deleterious effects such as unfavorable wettability condition and deposition of asphaltene. There is insufficient experimental data on changes is silica surface chemistry, micro-topography, and wettability alterations with asphaltene deposition and in absence and presence of nanoparticles (NPs). Therefore, fundamental research is needed to address this research gap. To this end, a thorough experimental research plan was created in three stages: characterization of NPs, preparation of asphaltene deposited silica surfaces, and surface analysis using Atomic Force Microscopy (AFM), Contact Angle (CA) measurements, and X-Ray Photoelectron Spectroscopy (XPS) surveys. Asphaltene was extracted from a Kazakhstani crude oil in accordance with the ASTM D6560-00 standard. The novel ZnO-SiO2-Thiazine nanocomposite (NC) and its constituent NPs – ZnO and SiO2 – were characterized using FTIR, TEM, XRD, SEM, and EDX techniques. These techniques were used to determine the size and distribution of NPs, as well as their chemistry, and surface morphology. AFM was used to investigate surface micro-topography of the silica surface samples with asphaltene deposition in presence and absence of NPs/NC. CA measurements were conducted for each sample to assess alteration of wettability in each sample's surface. XPS was used to evaluate elemental composition of the samples to analyze the asphaltene adsorption and its alteration in absence and presence of NPs and NC. XPS Survey has identified C1s, O1s, N1s, S2p, Si2p, and Zn2p orbitals and their atomic ratio present in the samples. Surface images produced by the AFM allowed viewing asphaltene precipitates on a nanoscale and observe the decrease in precipitate quantity in presence of NPs and NC. The CA measurements validated the AFM results by indicating that NPs tend to reduce the CA of the surfaces from oil-wet to intermediate-wet. In contrast, NC has a tendency to decrease the CA from oil-wet to water-wet. High resolution XPS spectra confirmed alterations of the surface chemistry in presence of NPs/NC, and proved that the novel NC to be more effective. The findings of this research work provides more insight into the changes in surface chemistry, micro-topography, and wettability alteration of silica-asphaltene interface in absence and presence of NPs and NC. The findings have significance for design of effective asphaltene precipitation nano-inhibitors and nao-EOR agents. Keywords: Asphaltene, nanoparticles, silica-asphaltene interface, AFM, XPS, micro-topography, wettability alteration, surface chemistry, asphaltene adsorption.