High Pressure Difference Research Articles

Effect of Inorganic Salt on Foam Properties of Nanoparticle and Surfactant Systems

Abstract We have studied the effect of NaCl and CaCl2 on phase behavior of foaming aqueous dispersions containing mixtures of silica nanoparticles (Ludox CL) and sulfobetaine (LHSB). At the evaluated ratio, the phase behavior results show that at a low CaCl2 concentration, sedimentation occurs, whereas a stable aqueous dispersion could be achieved when the CaCl2 concentration reaches to 20%. The adsorption experiments show that high concentrations of both NaCl and CaCl2 reduce the adsorption of LHSB to CL. In the CaCl2 dispersion the adsorption decreases significantly and only a few LHSB molecules can be adsorbed on the CL surface. Therefore, without the lower hydrophobicity of LHSB adsorption less CL could adsorbed at the air/water interface. The results on gas permeability show that aqueous dispersions containing mixtures of CL and LHSB show no obvious difference to aqueous systems containing only LHSB. The surface dilatation module of the LHSB and CL system in CaCl2 solution also shows a similar variation to the system with LHSB alone, which is significantly different from the system with 20% NaCl. Finally, foam flow tests in a porous medium show that compared to a 20% CaCl2 dispersion with the LHSB and CL system in 20% NaCl, a finer foam and a higher pressure difference could be achieved.

Insights on the morphology of air-assisted breakup of urea-water-solution sprays for varying surface tension

The efficacy of NOx reduction in diesel engines is mainly dependent on how uniformly urea-water solutions (UWS) are dispersed onto the catalyst surface of the Selective Catalytic Reduction (SCR) systems. The urea-based SCR systems also suffer drawbacks due to the formation of urea deposits onto the walls of after-treatment devices due to poor atomization characteristics of UWS. In this work, the impact of lowering the surface tension of UWS on the morphology of UWS sprays was explored using high-speed shadowgraph imaging techniques. The surface tension of UWS was lowered by adding surfactants; two surfactants viz., Sodium Dodecyl Sulfate (SDS) and Dodecyl-Dimethyl-Amine-oxide (DDA) were considered in this investigation. The surface tension of UWS was reduced to a maximum from 73.7 to 30.2 mN/m and 39.8 mN/m with the addition of DDA and SDS respectively at 75% of its respective Critical Micelle Concentration (CMC) in UWS. Even at a very low-pressure difference of 500 mbar of co-flowing air, the surfactant-added UWS tends to break-up relatively closer to the nozzle tip due to flapping-induced bag breakup, which improved its drop-size distribution. Under a relatively higher pressure difference of 2000 mbar of co-flow atomizing air, the liquid breakup was mostly due to surface stripping in surfactant-added UWS sprays that generated a large number of fine droplets. The image analyses of sprays were performed at far downstream locations from the nozzle to quantify the variations of their droplet-sizes caused by varying the surface tension of UWS. The surfactants added UWS sprays revealed a considerably narrower drop-size distribution by up to 43% compared to UWS sprays under high-pressure conditions, and this was due to a combination of flapping-induced bag breakup, surface stripping and secondary atomization of big droplets caused by reducing the surface tension of UWS. Reducing the surface tension of UWS has the potential to improve NOx reduction in SCR systems due to the reduction in droplet sizes of UWS sprays and also to reduce the formation of urea deposits.

MITIGATION OF SHOCK WAVE EFFECT PRODUCED BY AN EXPLOSION IN MINES BY CHANGING SAFETY BARRIER PENETRABILITY

Shock wave travel in a roadway with impermeable safety barriers is modeled numerically in the equilibrium and non-viscous formulation. Inclined and arched barriers are studied at the varied porosity in a range from 0 to 0.8. The inclined and arched barriers decrease the load exerted on the barrier structure by the shock wave owing to formation of a reflected wave which is oblique, or radial in case of the arched barrier. An increase in porosity of the barrier can additionally weaken the shock wave effect but barriers with high penetrability make the defensive screen inefficient, which is confirmed by the higher differential pressure at the shock wave front after passing the barrier.

Evaluating Patterns of Building Envelope Air Leakage with Infrared Thermography

The next-generation performance-based building energy codes are focusing on minimizing building envelope air leakage. The quantification of air leakage in buildings is typically performed with a blower door test. However, this test does not provide information about the locations of air leakage. The aim of this study is to demonstrate a method involving qualitative and quantitative components that can be used to characterize locations of air leakage with infrared thermography. Since air leakage can have a significant impact on building energy consumption in cold climates, like in Canada, this approach can quickly inform where air barrier discontinuities occurred during construction or where to selectively target air sealing efforts in existing buildings. The observations from this study are presented, based on a thermographic image analysis during a depressurized blower door test at various pressures, in an attempt to quantify the relative rates of air leakage. The results from the investigation showed that infrared thermography (IRT) was able to discern locations and infer relative ratios of air leakage. The qualitative analysis showed that areas of air leakage are more evident under higher pressure difference. The quantitative approach showed that a minimum of 25 Pa pressure difference was required to detect the air leakage in the vicinity of the window frame, as the surface temperature decreased rapidly (almost 60% of the indoor surface/outdoor air temperature difference) at this pressure. A temperature index was defined to prioritize the areas of air leakage for retrofitting purposes. Furthermore, a thermal image subtraction method was used to determine the characteristics of the cracks based on thermal patterns. Finally, the practical implication of this study, for building developers, home inspectors, property mangers, and homeowners, is the early detection of air leakage for both existing and newly constructed buildings which could result in energy and cost savings.

Thermally driven pumps and diodes in multistage assemblies consisting of microchannels with converging, diverging and uniform rectangular cross sections

Thermal transpiration pumping in multistage assemblies is computationally investigated. Each stage is formed by combining in series-long microchannels with (a) uniform–uniform (“uni–uni”), (b) converging–uniform (“con–uni”), (c) diverging–uniform (“div–uni”) and (d) converging–diverging (“con–div”) rectangular cross sections. In all four investigated assemblies the generated pressure difference with the associated mass flow rate is fully assessed, in terms of inlet pressure, inclination parameter and number of stages. The analysis is based on linear kinetic modeling and is valid in the whole range of gas rarefaction. It is concluded that the “con–uni” and “div–uni” assemblies provide higher pressure differences and lower mass flow rates than the “uni–uni” assembly and they may be more suitable for specific pumping applications. The characteristics of the “con–uni” and “div–uni” assemblies are very close to each other. The multistage “uni–uni”, “con–uni” and “div–uni” assemblies are more stable when operating at small inlet pressures, where the pressure difference remains almost constant in wide ranges of mass flow rate. It is advisable to add as many stages as possible to increase, depending on the application, either the pressure difference or mass flow rate or both. Furthermore, the “con–div” assembly provides smaller pressure differences and mass flow rates than the other three, but it is suitable for diode applications. It is characterized by the so-called blocking inlet pressure, where the deduced pressure difference in the converging and diverging channels is the same. A detailed parametrization of the blocking inlet pressure in terms of inclination ratio, mean height, temperature difference and gas species, has been performed. It is concluded that multistage “con–div” assemblies may be ideally applied as thermally driven microfluidic diodes to control or block the flow, as well as to separate the species in multicomponent gas mixtures.

New Acidizing Method Improves Stimulation in Deep, High-Temperature Offshore Well

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 196281, “Acidizing Done Right in Hot Offshore Wells: Case Study,” by Max Nikolaev, SPE, Bulat Kamaletdinov, and Nestor Molero, SPE, Schlumberger, et al., prepared for the 2019 SPE/IATMI Asia Pacific Oil and Gas Conference and Exhibition, Bali, Indonesia, 29-31 October. The paper has not been peer reviewed. The complete paper discusses a method of stimulating deep, high-temperature offshore wells by combining an efficient single-phase retarded acid (SPRA) system and an engineered, degradable, large-sized particulate and fiber-laden diverter (LPFD). The method was introduced in a well in the Arabian Gulf, where it helped the operator achieve effective, uniform stimulation. Introduction Treatment of deep, high-temperature carbonate reservoirs such as those in the Arabian Gulf presents a series of complex and related challenges to achieve effective and uniform stimulation. Elevated temperatures and heterogeneous formations in these reservoirs require robust treatment fluids that can withstand the harsh environment to achieve good reservoir contact with an acid system along the entire interval of interest. Emulsified acids have been the preferred stimulation choice of major operators in this region because of these acids’ superior corrosion inhibition and deeper penetration into the reservoir. However, using emulsified acid adds to the complexity of the stimulation operation by contributing to higher friction pressures, limiting pump rates, and requiring elaborate mixing procedures that constrain offshore rig-based interventions. Operators are searching for simplified acid systems that can deliver friction pressure similar to that of unmodified hydrochloric acid (HCl) and reservoir contact performance equivalent to that of emulsified acid. Arabian Gulf operators also seek a robust diverter that can withstand high differential pressure at high temperature, enabling efficient treatment coverage of all perforated intervals. Previous stimulation jobs in the region indicated a need for a significant amount of traditional diversion materials to effectively plug the leakoff zones. To address the challenges, an SPRA and a new degradable LPFD system were introduced to conduct a matrix-stimulation treatment featuring efficient contact with the reservoir, safe corrosion inhibition, and effective diversion in a well with a 320°F bottomhole static temperature and a heterogeneous environment with a permeability contrast of more than 100. The SPRA was a 15% HCl-based acid system. The fluid delivered friction pressures similar to those of unmodified 15% HCl and wormholing performance equivalent to that of emulsified acid without encountering the issues of fluid quality with respect to emulsion stability, and much higher dissolution power than organic acids and chelating agents. The pressure drop after the first acid stage was greater than 1,000 psi in approximately 60 minutes. After the second stage of acid, the pressure drop was close to 1,000 psi in approximately 30 minutes, achieving an approximately 1,000-psi increase of injection pressure across the perforations. Additionally, using the LPFD system reduced the footprint in offshore operations, simplified materials handling, and delivered the most efficient diversion performance in bullhead operations compared with that of other diverters.

A Device for the Simultaneous Determination of the Water Retention Properties and the Hydraulic Conductivity Function of an Unsaturated Coarse Material; Application to a Green-Roof Volcanic Substrate

Abstract The determination of the water retention curve (WRC) and hydraulic conductivity function (HCF) of a specific volcanic coarse granular material used as a substrate for urban green roofs in Europe was carried out on a newly developed specific device in which low suctions, typical of coarse granular materials, were controlled. Smaller suctions (up to 32 kPa) were imposed by using a hanging column system, and larger suctions (between 32 and 50 kPa) were imposed by using the axis translation technique in the same cell. The changes in suction during the tests were monitored by using a high accuracy differential pressure transducer. They were also used to determine the HCF by means of both Kunze and Kirkham’s and Gardner’s methods. The former technique was used at low suctions (<4 kPa) to account for the impedance effects due to the high air entry value ceramic porous disk and the latter was used between 4 and 50 kPa. Good comparability was observed in the data from both methods, demonstrating the good performance of the device. The mathematical expressions of the WRC of van Genuchten and Brooks and Corey were used, and a good fitting with our experimental data was obtained. Conversely, the HCFs derived from these expressions appeared to lead to a significant underestimation, confirming the need of an operational and simple device for the experimental determination of the HCF. Also, this material proved to be an appropriate material for green urban infrastructures, because of its lightweight, satisfactory water retention capability and hydraulic conductivity.

Enhanced performance of a PtCo recombination catalyst for reducing the H2 concentration in the O2 stream of a PEM electrolysis cell in the presence of a thin membrane and a high differential pressure

High electrochemical efficiency at elevated current densities and low H2 concentration in O2 can be achieved in PEM electrolysis using thin membrane and integrated recombination catalyst. An enhanced PtCo alloy recombination catalyst was synthesized and used at the anode of a membrane-electrode assembly (MEA). This allowed reducing the H2 concentration in the oxygen stream during electrolysis operation with a thin 50 μm perfluorosulfonic acid (PFSA) Aquivion® membrane. Both dual-layer and composite anode configurations (PtCo/IrRuOx) were investigated. The electrochemical performance of the MEAs containing the recombination catalyst was better than a bare MEA while producing a decrease of the H2 content at the anode. This allowed extending the partial load operation down to 5% at 55 °C under a differential pressure of 20 bar. The effects of the cathodic pressure and cell temperature (including evaluation of intermediate temperature operation at 140 °C) on both electrochemical performance and H2 concentration in the anode stream were investigated. An excellent performance of 4 A cm−2 at 1.75 V, at 140 °C, 20 bar cathode pressure, 5.5 bar anode pressure, with 0.6 mg cm−2 overall precious metal catalysts content was recorded. At 140 °C, the MEA also showed a moderate H2 concentration in O2 of about 2.3%, almost constant through most of the current density range.

Development of a Highly Elastic Composite Gel through Novel Intercalated Crosslinking Method for Wellbore Temporary Plugging in High-Temperature Reservoirs

Summary Effective mitigation of fluid loss and prevention of formation damage are substantial concerns during well completion and workover in low-pressure, high-permeability, and/or fractured reservoirs, especially with high temperature (HT). In this paper, a highly elastic composite gel is developed on the basis of the solution blending for “intercalated crosslinking.” The mechanism is the intercalation of polymer and crosslinker into layered silicate material (LSM) using a specific procedure. The gel is composed of HT resistant copolymer, crosslinker polyethyleneimine (PEI), LSM, and antioxidant in freshwater. The effects of main variables on the gelation performance are investigated. The mature composite gel strength is noticeably improved with increasing temperature. The elastic modulus (G′) of the mature composite gel prepared at 160°C can reach up to 15 000 Pa, while only a value of 6000 Pa is obtained for the gel at 130°C. The composite gel remains robust after aging 10 days at 160°C. The pressure-bearing capacity and rigidity of the mature composite gel are noticeably improved with increasing layered silicate concentration. This unique feature can benefit stress buffering when the sealing operation is conducted under high differential pressure such as the case with a long hydrostatic column. Scanning electron microscope (SEM) is used to further reveal the intercalated crosslinking mechanism of the composite gel. A temporary plugging experiment for a fractured limestone core also supports the gel's high-pressure (HP) resistance and low adsorption and retention to alleviate formation damage. The composite gel is promising for fluid loss mitigation that could be extended to other related near-wellbore operations in HT wells.

Real-time determination of rheological properties of high over-balanced drilling fluid used for drilling ultra-deep gas wells using artificial neural network

Drilling depleted and ultra-deep gas reservoirs required special drilling fluids which should be capable of bridging along the walls of the well and withstands a high differential pressure. High-overbalanced water-based drilling fluid (HOBWBDF) is one of the most common drilling fluid used to drill the ultra-deep gas wells. Drilling fluids properties such as yield point (YP), plastic viscosity (PV), apparent viscosity (AV), flow behavior index (n) and consistency index (k) are very vital inputs in managing rig hydraulics, margins of surge and swab pressure, equivalent circulation density (ECD) and hole cleaning. There is a need to develop a new technique to estimate the rheological properties in real-time using the frequent measurements of mud density and Marsh funnel viscosity, which are carried out more frequently (every 15–20 min).The main goal beyond this work is to build novel empirical models that are capable of predicting the above-mentioned rheological properties of high over-balanced water-based drilling fluid (HOBWBDF) in real-time for the first time. The models are built based on only two inputs which are the mud weight from the mud balance test and Marsh funnel viscosity measured by the Marsh funnel test. More than 1200 field measurements of rheological properties were used to feed an artificial neural network in order to develop new novel empirical models.The developed models using the ANN technique showed high accuracy for predicting the different drilling fluid rheological properties. The obtained results showed a maximum average absolute percentage error (AAPE) less than 8% with a correlation coefficient higher than 93%. The main advantages of these models are their inexpensiveness as there is no need for additional equipment to be added to the rig site. Moreover, these models would greatly help the drilling engineers to manage the ECD, surge and swab pressure and hole cleaning which in return will be reflected positively on the drilling performance.

Particle dispersion in a cleanroom – effects of pressurization, door opening and traffic flow

ABSTRACT Air cleanliness is of particular importance in clean environments, as a small source of contamination can highly disturb the true function of space. One common-place approach is to establish a positive pressure relative to adjacent areas that would avoid unwanted airborne particles. However, door operation and the movement of traffic may result in air mixing across the cleanroom door. This paper presents the results of a series of experiments to characterize the effect of pressure difference, traffic flow and door opening on cross-contamination and air quality inside the cleanroom. The experiments were conducted in an actual cleanroom where an oil-based substance was aerosolized in neighbouring areas, and its path inside the cleanroom was studied. Results suggested that the higher-pressure differentials were more effective to prevent aerosols to enter the cleanroom. Door operation can eliminate, and even reverse the pressurization across the door. Under a higher-pressure difference, however, it took a much shorter time for positive pressure to recover. The results of this work will be useful in determining the optimal settings of cleanroom operation, where the probabilities of contamination from an outside source are minimized.

Investigation of water and salt flux performances of polyamide coated tubular electrospun nanofiber membrane under pressure

In this study, a novel osmotic membrane was developed by polyamide (PA) coating on the tubular electrospun nanofiber (TuEN) support membrane. Water and reverse salt flux properties of the obtained membrane were investigated by applying pressure in addition to the osmotic forces. Surface characterization of the membrane was carried out by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) analyses and flux performance tests were performed in both cross flow and submerged membrane setups. Applying pressure from the feed to the concentrate side had significant effects on the water and salt fluxes. Higher pressure differences between the feed and concentrate sides resulted in unexpected high water fluxes up to 500 Lm−2h−1 (LMH). Besides, the pressure helps to transfer the salt content of feed water into the concentrate side, differently from the osmotic process preventing the salinity build-up at the feed side. PA coated TuEN membrane operated under pressure will exhibit a favorable solution in water/wastewater treatment applications, especially for membrane bioreactors (MBR) in terms of preventing salt accumulation in the bioreactor, decreasing the membrane fouling, increasing the volume of product water, and enabling the concentrate management.

Підвищення герметичності і екологічної безпеки ущільнень насосів АЕС

The determining factor for NPP pumps is safety, as well as the maximum sealing capacity, which imposes additional conditions when choosing the type of seal. Mechanical seals are widely used in pumps in nuclear power plants. The processes occurring at the junction of the contacting end surfaces of a seal in various operating modes are described. Cooling and safety pumps systems that pump radioactive media are subject to requirements, some of which can only be met with the use of special designs. On the basis of mechanical seals, new types of seals have been created, in which the sealing belts are unloaded and operate with a small gap in friction modes close to liquid: hydrodynamic and thermohydrodynamic seals. The principle of operation of thermohydrodynamic seals is based on the use of the deformation of the rings under the force of thermal stresses in the contact zone. At high pressure differentials and rotation speeds, when a long life is required and small leaks are allowed, seals with a continuous liquid film are used - hydrostatic seals. Impulse mechanical seals are self-adjusting non-contacting seals and are an alternative to hydrostatic and hydrodynamic non-contacting mechanical seals. Impulse mechanical seals with self-adjusting gap have a number of advantages over conventional mechanical seals and non-contacting hydrostatic and hydrodynamic mechanical seals. Seals with impulse balancing of the axially moving ring during the rotation of the shaft ensure contactless operation with low leaks, and during standstill — complete tightness. Examples of industrial application of impulse seals in pumping equipment of nuclear power plants were given.

Simulation of Stripper Flooding Due to the Increase of Feed Flowrate

In this investigation, UniSim software and the Soave-Redlich-Kong (SRK) thermodynamic model were utilized to study flooding in a Naphta stripping column. The objective of this study was to evaluate the impact of increasing feed flowrate from a design load of 121 m3/hr. to 165 m3/hr. on the performance of the plate column. In order to study only flooding in the column, UniSim software was run by keeping the LPG (Liquefied Gas petroleum) and Naphta products within the required specifications. According to the original design specifications of the stripping column, it should not be operated at high feed rates and differential pressure must not exceed 600 mbar. For the purpose of simulation, this value corresponds to a maximum allowable flooding percentage of 85%. The simulation results show that the flooding percentage was 144.5% in the case under study and 83.7% for the design case. Flooding occurred in all parts of the column with diameters of 2 m and 2.7 m. For the case under investigation, the reflux to feed ratio was reduced from 0.45 (design case) to 0.2. The originality of this investigation is the utilization of the temperature profile in the column as a tool to detect the plates where flooding could take place. The column temperature profile during the case under study suggests instability in the plates between trays 5 to 15. It is therefore suspected that flooding takes place mainly between those plates.

Water retention and transfer properties of a Green roof volcanic substrate

The water retention curve and the hydraulic conductivity function of a volcanic coarse granular material used as a substrate in an urban green roof in the Paris area was carried out on a newly developed device, in which low suctions were controlled. In the same cell, a hanging column system was used for controlling smaller suctions (up to 32 kPa) and the axis translation technique for larger suctions (up to 50 kPa). Water exchanges were monitored in connected tubes by using a high accuracy differential pressure transducer. The step changes in suction were also used to determine the hydraulic conductivity function by means of Gardner’s method, accounting for the impedance effects due to the high air entry value ceramic porous disk with Kunze and Kirkham’s method. van Genuchten and Brooks and Corey models were used for the water retention curve, but the hydraulic conductivity functions derived from these expressions appeared to lead to a significant under-estimation, confirming the need of operational and simple device for the experimental determination of the hydraulic conductivity function.

Development of Membrane Electrode Assemblies for State-of-the-Art Anion Exchange and Proton Exchange Membrane Electrolysis

Proton exchange membrane (PEM) electrolysis and anion exchange membrane (AEM) electrolysis are both able to directly produce high purity hydrogen from electricity and water. Key benefits of electrolysis using polymer membrane separators include a quick response rate, enabling load following, and ability to operate with high differential pressure. Operation under differential pressure allows for simultaneous electrolysis and electrochemical compression, simplifying overall system design. The development and stack integration of new, high performance electrolysis materials must include consideration of operating range and durability under differential pressure to maintain the technologic benefits. PEM electrolyzers are commercially available on the megawatt scale and produce hydrogen fuel that is increasingly cost competitive with fossil fuel in select parts of the world. Better utilization of low cost electricity from renewable energy (wind and solar) is one route to additional hydrogen cost reductions, for which a wide current operating range is beneficial. Thinner membranes, more active catalysts, and better electrode design enable high currents at acceptable cell efficiencies. Performance and durability data will be presented on state-of-the-art PEM electrolyzer materials operating under differential pressure. AEM electrolyzers are not currently commercially available, but promise membrane, catalyst, and balance of stack cost reductions. To begin to compete with PEM technology, performance and durability need to be improved. This work focuses on membrane stability under differential cell pressure and material integration into high performance AEM electrolyzers.

Clinical Significance of Conversion From Computational Fluid Dynamics to Morphology for Risk Evaluation of Aneurysm Recurrence After Coiling

Abstract INTRODUCTION Hemodynamic factors play a critical role in the recurrence of intracranial aneurysms after coiling. However, the computational fluid dynamics (CFD) analyses are not consistently performed all over the world, and its benefits were limited in the specific institutes. We tried to convert the hemodynamic parameters to morphological factors for the risk evaluation of aneurysm recurrence after coiling. METHODS Using pretreatment 3-dimensional rotational angiography data of 50 internal carotid artery aneurysms (7 recanalized, 43 stable) treated with endovascular coiling, we created a virtual post-coiling model produced by cutting the aneurysm dome for construction of virtual coil plane. At the virtual coil plane, we evaluated the pressure difference, which was defined as the pressure elevation at the coil plane from the parent artery divided by the dynamic pressure at the parent artery. After a statistical analysis of the relationship between the pressure difference and aneurysm recurrence, we performed statistical comparisons of pressure difference with morphological factors. RESULTS Recanalized aneurysms showed a significantly higher pressure difference than stable aneurysms (P < .001). The receiver operating characteristic analysis showed that the area under the curve value for the pressure difference (0.967). Morphologically, all 5 aneurysms that had the virtual coil plane at the line of upper border of internal carotid artery had a significantly higher pressure difference (P < .001) and recurred after coiling (P < .001). CONCLUSION The pressure difference in the virtual post-coiling model had a strong association with aneurysm recurrence after coiling. Additionally, the location of the coil plane as a morphological factor was significantly associated with pressure difference and aneurysm recurrence. The conversion of hemodynamic factors into simple morphological factors may contribute to expanded applications of the CFD analysis.

Sub-Bandage Pressure in the Canine Forelimb after Rigid Splint Application by Surgeons and Veterinary Students

Objective The aim of this study was to measure and compare sub-bandage pressures after a rigid splint was applied to the forelimb of a dog by surgeons and veterinary students. Animals One, adult, Labrador Retriever. Methods Sub-bandage pressure was measured at five locations on the limb of a dog using a previously validated pneumatic compression measurement system over a 4-hour period after splint application. All participants received the same instructions and the same dog was used for each splint application. Results Across time and location, mean sub-bandage pressures from the experienced group were significantly greater than those from the inexperienced group at all transducer locations and at all time points. People from the inexperienced group recorded the greatest range in sub-bandage pressures and had significantly higher-pressure differences across the five locations sub-bandage pressure was measured. Conclusions and Clinical Relevance Surgeons applied their splint bandages with approximately 50% greater pressure and 50% less variability between locations. The large range in sub-bandage pressures found may suggest that decreased and/or increased sub-bandage pressure may predispose to bandage complications.

Laboratory evaluation of nitrogen injection for enhanced oil recovery: Effects of pressure and induced fractures

Nitrogen has emerged as a suitable alternative to carbon dioxide for injection into hydrocarbon reservoirs worldwide to enhance the recovery of subsurface energy. Nitrogen typically costs less than CO2 and natural gas, and has the added benefit of being widely available and non-corrosive. However, the underlying mechanisms of recovery following N2 injection into fractured reservoirs that make up a large portion of the world’s oil and gas reserves are not well understood. Here we present the laboratory results of N2 injection into carbonate rocks acquired from a newly developed oil reservoir in Iran with a huge N2-containing natural gas reservoir nearby. We investigate the effectiveness of N2 injection for enhanced oil recovery in immiscible conditions before and after gas breakthrough under a low and high differential pressures across the core. In addition to the effects of pressure, we further illuminate the impacts of fractures—induced on the cores—to assess the displacement behavior and oil recovery factor. Our findings show that an ultimate oil recovery factor of more than 40% can be achieved by N2 injection in non-fractured cores even at immiscible conditions. The ultimate recovery and the onset times for oil production and gas breakthrough are found to be lowered by increasing differential pressures as well as inducing fractures (e.g., 17% reduction in ultimate recovery due to fracturing). However, at a given time when gas-oil interface has not yet reached the production zone (outlet), both increasing differential pressures and fractures transiently enhance the recovery efficiency. As a result, the impact of fractures is more pronounced in lower differential pressures, while the impact of differential pressures is stronger in the absence of fractures. Interestingly, our results attest to the role of molecular diffusion across fracture-matrix interface as the main recovery mechanism in fractured media, which controls the system dynamics before and after breakthroughs. The results not only provide a new perspective into how differential pressures and fractures fundamentally control the effectiveness of N2 flooding but also further show the promising prospects of N2 injection for EOR even at immiscible conditions.

Application of nanofluids for treating fines migration during hydraulic fracturing: Experimental study and mechanistic understanding

Hydraulic fracturing has emerged as one of the best and most economic methods for enhancing oil recovery from low permeability reservoirs such as shale gas reservoirs. However, its performance will be negatively affected by fines migration due to hydraulic fracturing process. In the present study, it has been tried to experimentally investigate the efficiency of a synthesized Nanosilica particles in reducing fines migration for the first time in literature. To this end, two sets of static and dynamic experiments, namely glass bead funnel test and core displacement analysis, were implemented, respectively. In the static test, increasing the soaking time and addition of Nanosilica led to the clearer effluent fluid, resulting in less concentrations of clay particles in solution. When the mixture of Nanosilica and glass beads was available in the solution, a higher differential pressure was obtained during dynamic condition in comparison to only glass beads, which means the lower permeability of the porous media. Moreover, DLVO theory was applied to demonstrate the clay particles absorption on the sand proppants surfaces. Consequently, it was observed that the use of Nanosilica particles mixed with sand proppant can effectively reduce fines migration; thereby, it can enhance hydraulic performance of the fracturing operation. Cited as : Moghadasi, R., Rostami, A., Hemmati-Sarapardeh, A. Application of nanofluids for treating fines migration during hydraulic fracturing: Experimental study and mechanistic understanding. Advances in Geo-Energy Research, 2019, 3(2): 198-206, doi: 10.26804/ager.2019.02.09