Effect of Nanoparticles on Viscosity and Interfacial Tension of Aqueous Surfactant Solutions at High Salinity and High Temperature

Surfactant flooding has widely been used as one of the chemically enhanced oil recovery (EOR) techniques. Surfactants majorly influence the interfacial tension, γ, between oil and brine phase and control capillary number and relative permeability behavior and, thus, influence ultimate recovery. Additives, such as nanoparticles, are known to affect surfactant properties and are regarded as promising EOR agents. However, their detailed interactions with surfactants are not well understood. Thus, in this work, we examined the influence of silica nanoparticles on the ability of surfactants to lower γ and to increase viscosity at various temperatures and salinities. Results show that the presence of nanoparticles decreased γ between n-decane and various surfactant formulations by up to 20%. It was found that γ of nanoparticles–surfactant solutions passed through a minimum at 35 °C when salt was added. Furthermore, the viscosity of cationic surfactant solutions increased at specific salt (1.5 wt.%) and nanoparticle (0.05 wt.%) concentrations. Results illustrate that selected nanoparticles–surfactant formulations appear very promising for EOR as they can lower brine/n-decane interfacial tension and act as viscosity modifiers of the injected fluids.     

Pore-scale simulation of NMR response

The random walk method is used to simulate magnetization decay in porous media. The simulations were performed on images of the pore space obtained using micro-CT scanning and in topologically equivalent networks extracted from these images using a maximal ball algorithm. The simulation results were validated through comparison with experimental measurements of T₂ distribution, absolute permeability and resistivity in two sand packs and from comparing predictions on images and networks of Fontainebleau sandstone. In all cases, the comparisons were good, although the networks gave a slightly narrower T₂ distribution, implying that some fine detail of the pore structure was lost. This work suggests that imaging, network extraction and pore-scale simulation can be used to predict single-phase transport properties successfully. It serves as a validation for pore-network models and the methods used to generate networks.     

Simulation and Experimental Validation of Two‐Phase Flow in an Aerosol Counter‐Flow Reactor using Computational Fluid Dynamics

A simulation of the hydrodynamic behavior of an aerosol‐counter flow reactor was conducted using an Euler‐Lagrange method. The simulation results were then verified with experiments. The process simulated was a separation process required during the production of biodiesel (fatty acid methyl ester). In this process, the liquid ester/glycerol phases are continuously injected through a hollow cone nozzle with an overpressure of 10⁶ Pa into the reactor, operated at 15000 Pa. The liquid is atomized because of the pressure drop and a liquid particle spray is generated with an inlet velocity of 44.72 m/s. Water vapor of temperature 333 K is injected tangentially through two side, gas inlets with an inlet velocity of 1.2 m/s. Excess methanol is subjected to a mass transfer from the liquid phase into the gas phase, which is withdrawn through the head of the reactor and condensed in an external condenser unit. The stripping of the methanol off the liquid leads to a sharp interface between the glycerol and the ester phase, which can then be easily separated by gravity or pumping. The gas velocity field, pressure field and the liquid particle trajectories were calculated successfully. Simulated dwell time distribution curves were derived and analyzed with the open‐open vessel dispersion model. Experimental dwell time distribution curves were measured, analyzed with the open‐open vessel dispersion model, and compared with the simulated curves. A good consistency between simulated and measured Bodenstein numbers was achieved, but 25 % of the simulated particles exited at the reactor's head, contrary to experimental observations. The difference between simulated and measured dwell times was within one order of magnitude.     

Investigating the mechanism of microbiologically influenced corrosion of carbon steel using X-ray micro-computed tomography

Journal of Materials Science - The mechanism of pitting corrosion of carbon steel by an oilfield microbial consortium was investigated using a combination of X-ray micro-computed tomography...     

A novel approach to determine the Biot’s coefficient using X-ray computed tomography

Linear poroelastic effective stress law is often used to relate in situ total stresses to pore fluid pressure in underground formations. The indirect estimations of effective stress coefficient (Biot coefficient) based on porosity relationships are often not accurate, and therefore the Biot coefficient measurements on retrieved samples using hydro-mechanical laboratory testing is considered. In this study, we propose a new indirect technique to infer the Biot coefficient from micro X-ray computed tomography (XRCT) images of porous granular samples whenever images are available using a simple principle of continuum mechanics. The performance of the method was assessed through a series of experiments conducted on sandstone and unconsolidated sand. The proposed method enables calculating the anisotropy of the Biot coefficient of the sample in three dimensions. We also conducted the conventional hydro-mechanical experiment to validate the obtained Biot coefficient results from the XRCT technique. The proposed technique shows promising results on estimation of the Biot coefficient. The analysis of the images confirms that the method performs well when the connectivity between grains (skeleton structure) can be extracted from XRCT images with enough resolution. The method is also able to (a) estimate the Biot coefficient of both consolidated and unconsolidated sand structure and (b) map the anisotropy of Biot coefficient in three dimensions.

     

Compressional wave velocity of hydrate-bearing bentheimer sediments with varying pore fillings

A potential alternative energy resource to meet energy demands is the vast amount of gas stored in hydrate reserves. However, major challenges in terms of exploration and production surround profitable and effective exploitation of these reserves. The measurement of acoustic velocity is a useful method for exploration of gas hydrate reserves and can be an efficient method to characterize the hydrate-bearing sediments. In this study, the compressional wave velocity (P-wave velocity) of consolidated sediments (Bentheimer) with and without tetrahydrofuran hydrate-bearing pore fillings were measured using the pulse transmission method. The study has found that the P-wave velocity of consolidated sediments increase with increasing hydrate formation and confining pressure. Of the two samples tested, the increase in wave velocity of the dry and hydrate-bearing samples amounted to 27.6% and 31.9%, respectively. Interestingly, at the initial stage of hydrate formation, there was no change in P-wave velocity, which was followed by a steady increase as the hydrate crystals began to agglomerate and then it increased rapidly to a constant value, suggesting that the test solution had converted to a hydrate solid.     

X‐ray micro‐computed tomography analysis of accumulated corrosion products in deep‐water shipwrecks

Accumulated corrosion products from two different shipwrecks which had lain on the seabed (2.5 km depth) for 73 years were systematically analysed by three‐dimensional imaging at high resolution using X‐ray micro‐computed tomography. Complementary surface and chemical characterization experiments were conducted to identify the morphological structure of the corrosion products. Goethite was observed as the main corrosion phase found in both the wreck's corrosion products. However, other corrosion products such as silica, lepidocrocite, maghemite, magnetite, benyacarite, jarosite and amorphous materials were noticed using Fourier transform infrared spectroscopy, Raman spectroscopy and X‐ray diffraction. In addition, mineralized microbial structures were also observed as significant constituents of the corrosion products. However, there were significant differences between samples from the two shipwrecks including porosity, distribution and volume percent of the corrosion products components. The mechanism of different corrosion products formation was proposed and discussed in detail.