IN OIL Research Articles

Optimum demulsifier formulations for Nigerian crude oil-water emulsions

The formation of crude emulsion during oil production and processing is a challenge of significant proportions to the oil producers. Studies show that about two third of Nigerian crude oil production is in form of water in oil emulsion. For economic and operational reasons, it is necessary to separate the water completely from the crude oil before transportation or refining.Efficiency of separation of crude emulsions is of major importance to producers. To this end, this study primarily seeks to investigate the formulation of effective demulsifier that can be used to achieve this aim; and in so doing, the optimal separation efficiency attainable by this demulsification process is determined. Six different samples of water and oil soluble demulsifiers were used on two different samples of synthetic emulsion (sample I and II (both water in oil emulsion) from different Nigerian oil fields). The bottle test method was used to determine the percentage water separation for each crude oil emulsion/chemicals (demulsifiers) mixture. The concentrations of the combined six chemicals (demulsifier samples A–F) in the mixture were related to the percentage water separation using response surface methodology central composite design (RSMCCD).Results show that the optimum concentrations of demulsifiers A–F are 59 ppm/39 ppm/29 ppm/20 ppm/29 ppm/13 ppm respectively for crude oil sample I. While 54 ppm/40 ppm/25 ppm/21 ppm/29 ppm/8 ppm respectively were observed as optimum concentration for crude oil II. The combination of these chemical was observed to return better performance than the existing commercial demulsifiers with percentage water separation of 92% and 94% compared to percentage water separation of 87% and 90% returned by one of the currently available demulsifier used in the petroleum industry for crude oil A and B respectively. Hence, the need to carry out optimization analyses on different emulsified crude oil cannot be over-emphasize.

Study of Winsor I to Winsor II Transitions in a Lattice Model

Experiments show that with increasing temperature, microemulsion systems undergo Winsor transitions. The transitions occur from Winsor I (oil droplets in water media) to Winsor II (water droplets in oil media) via Winsor III (bicontinuous phase) with an increase in the temperature. In this paper, it has been shown, for the first time, how one can study the qualitative effects of temperature, head, tail, and oil chain lengths, on these transitions. Simple cubic lattice with excluded volume and periodic boundary conditions is used to mimic the box of the simulation as a bulk of solution. The simulations have been done using the standard traditional Metropolis algorithm in the canonical ensemble (N, V, T). Configurational bias Monte Carlo and reptation moves are used with an equal probability to relax the systems. A very simple interaction model, i.e., the repulsions of water (or heads of surfactants) with oil (or tails of surfactants), is used due to the main characteristic of oil-water mixtures or amphiphilic molecule that is the hydrophobicity. The interfacial tension between oil and water (gammaow) is related to the averaged total energy of the lattice. The model shows that the Winsor III has a minimum interfacial tension (gammaow) similar to experimental results. Changing the phase structure from Winsor III to Winsor I (or Winsor II), increases the interfacial tension which is in agreement with experiments. To relate interfacial tension with the interaction parameter, the simple theory of Bragg-Williams has been used. All of the results such as the effects of oil chain length, head and tail beads number are all similar to the experimental results. Using the Davies method for calculating hydrophilic-lypophilic Balance (HLB), similar to the experimental results, Winsor III phase is formed at HLB value nearly to 10.

Measurement of inter-particle forces from the osmotic pressure of partially frozen dispersions

When an oil-continuous dispersion is frozen two microdomains are formed: one, the pure oil solvent which is selectively solidified (I), the other, a concentrated `liquid' dispersion of particles in oil (II). These two domains are intimately mixed within the frozen colloid and exist in a state of equilibrium determined by the system pressure and temperature. The position of equilibrium controls the proportion of the solvent which is solidified, and thereby the concentration of particles within the fluid microdomains (II). Combined with SANS measurements, to determine the inter-particle separation in these microdomains, an analysis based on osmotic pressure provides a measure of the inter-particle repulsion forces presented by the surfactant layers.

Freeze–fracture electron microscopy of lyotropic lipid systems Quantitative analysis of cubic phases of space group Ia3d (Q230)

Abstract The cubic phases Q230 (space group Ia3d) of type I (oil in water) and type II (water in oil) have been studied by freeze-fracture electron microscopy. The preservation of the sample structure during cryofixation was verified by low temperature X-ray diffraction. Three types of fracture planes were clearly identified in the type I system and two in the type II system. These fracture planes showed two-dimensionally ordered domains, each subdivided into subdomains related to each other by displacements and rotations compatible with the symmetry of the space group. The images were filtered using correlation averaging techniques and the filtered images were compared with the corresponding sections of the electron density map. Several conclusions were drawn: (i) The structures of the samples had been preserved after quenching, fracturing and replicating processes, (ii) The electron microscope images were fully compatible with the postulated space group symmetries. (iii) The fracture planes coincide wit...