Strain measurement with multiplexed FBG sensor arrays: An experimental investigation

In conventional rock mechanics testing, radial strain measuring devices are usually attached to the sample\u27s surface at its mid-height. Although this procedure provides a realistic picture of the lateral deformation undergone by homogeneous samples, however, this assumption may not be accurate if the tested rock has significant heterogeneity. Fibre Bragg Grating (FBG) sensors have recently been introduced to various rock testing applications due to their versatility over conventional strain gauges and radial cantilevers. FBG sensors have small size, multiplexing capability, and immunity to magnetic interference. The main objective of this study is to explore and understand the capabilities of FBG sensing for strain measurement during rock mechanics testing, including under confining. To do so, two limestone plugs (Savonnières limestone) and one acrylic Poly Methyl Methacrylate (PMMA) plug, all of 38 mm diameter, were prepared. The acrylic plug and one of the Savonnières samples plugs were subjected to Unconfined Compressive Strength (UCS) tests. The second Savonnières plug was subjected to a hydrostatic test up to 20 MPa confining at room temperature. FBG sensors of 125 μm cladding diameter with ceramics (Ormocer) coating were glued on the surface of each sample, spreading across the entire sample\u27s height. Strain gauges and cantilever-type radial gauges were used on the samples submitted to UCS for comparison. Results show that radial strain measurements and calculated elastic properties derived from the FBG readings for samples are comparable to readings from the conventional strain gauges and cantilever-type devices. Apparent bulk moduli based on volumetric strain computed from FBG radial strain readings during the hydrostatic test on the Savonnières sample was consistent with benchtop measurements conducted on the Savonnières sample and another plug extracted from the same parental block, as well as published literature data. Moreover, variations in the calculated elastic properties are interpreted as evidence that the FBG sensors detected heterogeneities in the samples\u27 inner structure, which can be seen in the density profiles computed from x-ray CT images. Such observation confirms the potential of the presented FBG sensors configuration for 3D strain mapping in rock mechanics tests

Nanomaterials for subsurface application: study of particles retention in porous media

The ability to transport nanoparticles through porous media has interesting engineering applications, notably in reservoir capacity exploration and soil remediation. A series of core-flooding experiments were conducted for quantitative analysis of functionalized TiO2 nanoparticles transport through various porous media including calcite, dolomite, silica, and limestone rocks. The adsorption of surfactants on the rock surface and nanoparticle retention in pore walls were evaluated by chemical oxygen demand (COD) and UV–Vis spectroscopy. By applying TiO2 nanoparticles, 49.3 and 68.0 wt.% of surfactant adsorption reduction were observed in pore walls of dolomite and silica rock, respectively. Not surprisingly, the value of nanoparticle deposition for dolomite and silica rocks was near zero, implying that surfactant adsorption is proportional to nanoparticle deposition. On the other hand, surfactant adsorption was increased for other types of rock in presence of nanoparticles. 5.5, 13.5, and 22.4 wt.% of nanoparticle deposition was estimated for calcite, black and red limestone, respectively. By making a connection between physicochemical rock properties and nanoparticle deposition rates, we concluded that the surface roughness of rock has a significant influence on mechanical trapping and deposition of nanoparticles in pore-throats

Influence of surfactant and electrolyte concentrations on surfactant adsorption and foaming characteristics

Surfactant adsorption and foaming characteristics are influenced by surfactant concentration and presence of inorganic electrolytes. Hence, it should be possible to optimize the performance of the surfactants in subsurface applications by understanding the influence of these parameters on surfactants. This study investigates the adsorption of sodium dodecyl sulfate (SDS) on kaolinite as a function of surfactant concentration and added electrolyte (NaCl, CaCl2and AlCl3) concentration. Influence of temperature on the electrolyte and surfactant interactions was also examined. Adsorption isotherms were obtained using surfactant concentrations higher and lower than the critical micelle concentration (CMC). Surfactants adsorption on kaolinite was determined using a surface tension technique and two phase titration methods. Adsorption data were analyzed by fitting with Langmuir and Freundlich adsorption isotherms. The foam was generated by dispersing CO2gas into the surfactant solution through a porous stone. Foam half-life and the rate of foam collapse as function of time was monitored. The adsorption of SDS by kaolinite increases with the increasing concentration of NaCl and CaCl2and decreasing temperature. However, adsorption in presence of AlCl3shows different behavior. The adsorption remains constant irrespective of the increasing AlCl3concentration. Results show that the adsorption of SDS onto kaolinite in presence and absence of salts follows the Langmuir isotherm models. Salts containing trivalent ions and divalent ions (AlCl3and CaCl2) were found to increase SDS adsorption on kaolinite and decrease bubbles stability compared to salts containing mono ions (NaCl). The order of increase in surfactant adsorption and bubble coalescence in presence of salts is as follows: AlCl3>CaCl2>NaCl. There was an optimum surfactant concentration corresponding to maximum foam stability beyond which there was either a reduction or no significant changes in foam stability. This concentration decreases in presence of salts, except for AlCl3and high concentrations of NaCl (5�wt%) and CaCl2(1�wt%). The presence of salt improved foam generation and bubble stability at SDS concentration below the CMC. Above CMC, the bubble coalescence inhibition and foam stability decreased in the presence of salt. Decrease in surfactant surface tension and CMC, the screening effect of electrostatic double layer (EDL) by salts and the ability of SDS to form a complex with divalent (Ca2+) and trivalent (Al3+) cations are critical factors affecting SDS adsorption and foaming behaviors in presence of AlCl3,CaCl2and NaCl salts. The results of this study have wide applications in the design, implementation and optimization of chemical EOR in the field

Experimental study of the influence of silica nanoparticles on the bulk stability of SDS-foam in the presence of oil

The influence of silica nanoparticles on the bulk stability of SDS-foam in the presence of oil was investigated in this study using KRÜSS dynamic foam analyzer. The bulk foam static stability was evaluated from half-decay time, liquid drainage, bubble size distribution, and change in total height and volume of the generated foams with respect to time. Results clearly showed that foam stability in the presence of oil mainly depends on the viscosity and density of the oil. Foam stability increased with the addition of silica nanoparticles due to the aggregation of the nanoparticles at the thin lamellae of the foam, which prevents spreading of the oil at the gas–liquid interface. Moreover, optimum foam stability was obtained with the modified nanosilica–SDS mixtures, while slower liquid drainage from the foam did not generally result in high foam stability

Influence of silicon oxide and aluminum oxide nanoparticles on air and CO2 foams stability in presence and absence of oil

One of the major issues in foam application for enhanced oil recovery (EOR) is the foam stability in presence and absence of oil. In this study, a systematic experimental study of the bulk and bubble scale stability of air and CO2 foams stabilised by sodium dodecyl sulphate (SDS) and nanoparticles were conducted. Foam-oil interactions were further study in etched glass micromodel in order to investigate and compare the foam performance at static and dynamic conditions. Influence of nanoparticles hydrophobicity and oil types on foam behaviors were assessed. Static bulk and bubble-scale experiments were conducted with KRÜSS dynamic foam analyser while the flow characteristics experiments were conducted in etched glass porous medium. Results show that the foam half-life increased while the size of generated bubbles decreased with the presence of nanoparticles in the surfactant solution. Successful propagation of nanoparticles-SDS foam through capillary snap-off and lamellae division was observed in presence of oil in the porous medium. Foam stability decreases with decreasing oil viscosity and density. Except for hydrophobic aluminum oxide nanoparticles with contact angle of 118.19°, the static and dynamic stability of the air and CO2 foams increased with increasing nanoparticles hydrophobicity. The addition of nanoparticles into the surfactant solution considerably improved foam stability due to the adsorption and aggregation of the nanoparticles at the thin lamellae and plateau border. This prevents liquid drainage and film thinning by increasing film elasticity and film strength from 23.2 μm to 136 μm. It can be concluded from this study, that stable air and CO2 foams can be generated with nanoparticlessurfactant mixed systems in absence and presence of oil with favourable nanoparticles hydrophobicity

Experimental investigation of minimization in surfactant adsorption and improvement in surfactant-foam stability in presence of silicon dioxide and aluminum oxide nanoparticles

Foams stabilized by a mixture of nanoparticles and surfactants are presently being considered for improving the poor macroscopic sweep efficiency of gas enhanced oil recovery (EOR) methods. The stability of these foams is influenced by the adsorption and foaming properties of the nanoparticles-surfactant mixtures. This study investigates the influence of silicon dioxide (SiO2) and aluminum oxide (Al2O3) nanoparticles on sodium dodecyl sulfate (SDS) adsorption on kaolinite and SDS-foam stability at static and dynamic conditions. The adsorption experiments were conducted by surface tension and two-phase titration methods. Adsorption data were analyzed by fitting with Langmuir, Freundlich and Temkin adsorption isotherms. Influence of salt on foam performance was investigated from bulk stability experiment conducted using KRÜSS dynamic foam analyzer. The pore scale visualization experiments were carried out with etched glass micromodels to study foam stability in porous media. Results show that SDS adsorption on kaolinite reduced by 38% in presence of Al2O3 nanoparticles and 75% in presence of SiO2 nanoparticles. The Langmuir isotherm model suits the equilibrium adsorption of sole SDS and Al2O3-SDS onto kaolinite while the Freundlich isotherm model suits the adsorption of SiO2-SDS onto kaolinite. Foam stability decreased in presence of salts until the transition salt concentration. Beyond the transition salt concentration, foam stability generally increased with the increasing salt concentrations. The presence of Al2O3 and SiO2 nanoparticles increased the foam half-life and decreased the transition salt concentrations. The dominant mechanisms of foams flow process were identified as lamellae division and bubble-to-multiple bubble lamellae division. The dominant mechanisms of residual oil mobilization and displacement by foam were found to be direct displacement and emulsification of oil. The identified pore scale mechanisms were independent of the pore geometry of the etched glass micromodels. There was lamellae detaching and collapsing during the flow process of SDS-foam in presence of oil which resulted in poor microscopic displacement efficiency. The SiO2-SDS and Al2O3-SDS foams propagated successfully in porous media in presence of oil with almost 100% microscopic displacement efficiency due to the enhanced films interfacial elasticity. The findings of this research provide an insight into surfactant adsorption minimization and pore-scale mechanisms of foam stability improvement by nanoparticles

Protein foam application for enhanced oil recovery

Protein foam was explored as a foaming agent for enhanced oil recovery application in this study. The influence of salinity and oil presence on bulk stability and foamability of the egg white protein (EWP) foam was investigated. The results were compared with those of the classical surfactant sodium dodecyl sulfate (SDS) foam. The results showed that the EWP foam is more stable than the SDS foam in the presence of oil and different salts. Although, the SDS foam has more foamability than the EWP foam, however, at low to moderate salinities (1–3 wt% NaCl), both foam systems showed improvement in foamability. At a NaCl concentration of 4.0 wt% and above, foamability of the SDS foam started to decrease drastically while the foamability of the EWP foam remained the same. The presence of oil has a destabilizing effect on both foams but the EWP foam was less affected in comparison to the SDS foam. Moreover, increasing the aromatic hydrocarbon compound percentage in the added oil decreased the foamability and stability of the SDS foam more than EWP foams. This study suggests that the protein foam could be used as an alternative foaming agent for enhanced oil recovery application due to its high stability compared to the conventional foams

Wettability of Nanostructured Transition-Metal Oxide (Al2O3, CeO2, and AlCeO3) Powder Surfaces

Wettability has been the focal point of many studies in metal oxide materials due to their applications in water–gas shift reactions, organic reactions, thermochemical water splitting, and photocatalysis. This paper presents the results of systematic experimental studies on the wettability of surfaces of nanostructured transition-metal oxides (TMOs) (Al2O3, CeO2, and AlCeO3). The wettability of nanoparticles was investigated by measuring contact angles of different concentrations of water-based nanofluids (0.05–0.1 wt%) on the glass slide. The morphology, the heterostructure, and the nature of incorporated nanoparticles were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Characteristic diffraction patterns of the nanomaterials were evaluated using energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The contact angles of water–Al2O3, water–CeO2, and water–AlCeO3 were measured as 77.5 ± 5°, 89.8 ± 4°, and 69.2 ± 1°, respectively. This study suggests that AlCeO3 is strongly water-wet (hydrophilic), while CeO2 is weakly water-wet (hydrophobic). It further demonstrated that the sizes and compositions of the nanoparticles are key parameters that influence their wetting behaviors