A Zeta Potentiometric Study on Effects of Ionic Composition and Rock-Saturation on Surface-Charge Interactions in Low-Salinity Water Flooding for Carbonate Formation

As carbonate reservoirs are mostly oil-wet, the potential for the success of a waterflooding is lower. Therefore, a primary focus during waterflooding such reservoirs is on the ionic composition and salinity of injected brine which are able to impact the alteration of the rock wettability favorably by altering the surface charge towards a higher negative value or close to zero. The objective of this study is to employ zeta potentiometric studies comprising streaming potential and streaming current techniques to quantify the surface interactions and charges between the carbonate rock and fluid type as a function of the variations in its ionic state and rock saturation. Zeta potentiometric studies were conducted on carbonate rock samples to understand the behavior of different aqueous solutions by variation in the brine's salinity and ionic composition and the results were integrated with wettability studies. The concentrations of potential-determining ions (PDIs) such as SO42-, Mg2+ and Ca2+ in the injected brines are deemed responsible for altering the wettability state of the carbonate rocks. Several diluted brines (25%, 10% and 1% diluted seawater) and smart brines have been investigated. Smart brines were prepared by spiking the concentration of major PDIs. All zeta potential measurements were conducted using a specially designed zeta potentiometer sample-holding clamp capable of using the whole core plugs rather than pulverized rock samples. A major advantage of using the whole core sample is that the same core can be used in subsequent coreflooding tests, thus making zeta potentiometric results more relevant and representative for a particular rock-fluid system used in the study. The classical streaming potential and streaming current techniques were used for zeta potential measurement. The Fairbrother-Mastin approach was used where the streaming potential is measured against different pressure differentials. Measurements were also carried out for brines with rock samples of different states: oil-saturated, water-saturated and rock samples cleaned with organic solvents to determine any likely variations in surface charge interactions. The results of our experiments imply that the value of zeta potential either increases or becomes more negative with increasing percentage of dilution (25%, 10%, and 1%). This can be attributed to electrical double-layer expansion which is primarily caused by reduced ionic strength. Furthermore, with measurements done on smart brines, zeta potential value was also found to be increased when different diluted brines are spiked with ionic concentration of PDIs such as sulfate. This could have been caused by surface ion alteration mechanism where PDIs get adsorbed on rock surface causing possible detachment of oil droplets. Both the phenomena are known mechanisms for altering wettability towards more water wetness in carbonate rocks and are discussed in detail.

Synthesis, characterization, biological activity of Schiff bases derived from 3-bromo-4-methyl aniline and its potentiometric studies with Cu(II), Co(II) and Ni(II) ions

Schiff bases namely, 3-bromo-4-methyl-N-(2-nitrobenzylidene)aniline; 3-bromo-4-methyl-N-(2,4,5-trimethoxybenzylidene)aniline; 3-bromo-N-(4-methoxybenzylidene)-4-methylaniline and N-(3-bromo-4-methylphenyl)-1-(1H-indol-3-yl)methanimine have been synthesized and characterized by elemental analysis, FT-IR, Mass and 1H-NMR spectroscopy. Schiff bases have been screened for Antimicrobial activity against bacteria and fungi by using MIC determination. Binary complexes of Co(II), Ni(II) and Cu(II) with Schiff bases in solution have been studied potentiometrically in 60:40 % (V/V) 1,4-dioxane-water system at constant temperature 27˚±0.5˚C and at an ionic strength of 0.1 M KNO3. The order of stability constant of formed binary complexes in solution was examined.

Potentiometric Studies of Mixed Copper(II) Complexes with δ-Aminolevulinic Acid and Some Selected Peptides

Ternary complex formation in the system Cu(II)-ALA-L (ALA = δ-aminolevulinic acid drug; L = peptides) has been studied by pH-potentiometrically at 25 ± 0.1 ºC with I = 0.10 mol L-1 NaCl. The stability constants of binary and ternary complexes were calculated and interpretated. The concentration distribution of the complexes in solution was graphically presented using the HySS program. In addition, the values of Δlog K, log X and relative stabilization percentage (% R.S.) for the mixed-ligand complexes studied have been evaluated and discussed.