Examination of literature on colloidal dispersion gels for oil recovery

This paper examines literature that claims,suggests,or implies that floods with"colloidal dispersion gels"(CDGs)are superior to polymer floods for oil recovery.The motivation for this report is simple.If CDGs can propagate deep into the porous rock of a reservoir,and at the same time,provide resistance factors or residual resistance factors that are greater than those for the same polymer formulation without the crosslinker,then CDGs should be used in place of polymer solutions for most/all polymer,surfactant,and ASP floods.In contrast,if the claims are not valid,(1)money spent on crosslinker in the CDG formulations was wasted,(2)the mobility reduction/mobility control for CDG field projects was under-designed,and(3)reservoir performance could have been damaged by excessive loss of polymer,face-plugging by gels,and/or excessive fracture extension.From this review,the clear answer is that there is no credible evidence that colloidal dispersion gels can propagate deep into the porous rock of a reservoir,and at the same time,provide resistance factors or residual resistance factors that are greater than those for the same polymer formulation without the crosslinker.CDGs have been sold using a number of misleading and invalid arguments.Very commonly,Hall plots are claimed to demonstrate that CDGs provide higher resistance factors and/or residual resistance factors than normal polymer solutions.However,because Hall plots only monitor injection pressures at the wellbore,they reflect the composite of face plugging/formation damage,in-situ mobility changes,and fracture extension.Hall plots cannot distinguish between these effects-so they cannot quantify in situ resistance factors or residual resistance factors.Laboratory studiesdwhere CDG gelants were forced through short cores during 2-3 h-have incorrectly been cited as proof that CDGs will propagate deep(hundreds of feet)into the porous rock of a reservoir over the course of months.In contrast,most legitimate laboratory studies reveal that the gelation time for CDGs is a day or less and that CDGs will not propagate through porous rock after gelation.A few cases were noted where highly depleted Al and/or HPAM fluids passed through cores after one week of aging.Details about these particular formulations/experiments were sparse and questions remain about their reproducibility.No credible evidence indicates that the CDG can propagate deep into a reservoir(over the course of weeks or months)and still provide a greater effect than that from the polymer alone.With one exception,aluminum from the CDG was never reported to be produced in a field application.In the exception,Chang reported producing 1-20%of the injected aluminum concentration.The available evidence suggests that some free(unreacted)HPAM and aluminum that was associated with the original CDG can propagate through porous media.However,there is no evidence that this HPAM or aluminum provides mobility reduction greater than that for the polymer formulation without crosslinker.

Determination of the Structure of Polyacrylamide/Aluminum Citrate Colloidal Dispersion Gel System

1 INTRODUCTIONIn recent years,colloidal dispersion gel(CDG)have been attracting more and more in thefield of enhanced oil recovery on account of the cost-effectiveness and high efficiency ofblocking formation.Compared with bulk gel(BG),CDG exhibits lower polymer concentra-tion,undefined shape and selective blocking formation characteristics.The characteris-tics of CDG and BG are related to structure.In the bulk gel a continuous network of polymermolecules is formed predominant through intermolecular cross-linkages.The

In - Depth Colloidal Dispersion Gels Improve Oil Recovery Efficiency

Daqing Oilfield has carried out the production of polymer flooding was promoted since in 1996. Presently, polymer flooding is very successful in several production plants of Daqing Oilfield, and getting into industrialization production. It has played a very important role in maintaining the oilfield stable production of over 50 million tons of oil. But the high permeability variation is serious, resulting in polymer production in some production wells recylingly and production concentration increasing slowly, which adversely affects polymer flooding efficiency. Chlloid dispersion gels (CDG) is a unique in - depth permeability modification process. It can reduce in - depth reservoir permeability variation by moving into highly permeable, water saturated zones and providing high resistance to subsequent water injection in those zones, so that oil can be produced from tighter rock. So CDG can enlarge volumetric sweep, and improve oil recovery efficiency. We had a CDG pilot programme in Daqing Oil Field in 1999, now this pilot has been entering into effective period with produing more oil and less water.

Preparation and characterization of colloidal dispersions of graphene-like structures from different ranks of coals

This paper focuses on preparation of colloidal solution of graphene-like structures from different ranks of coals: brown coal,bituminous coal,low-volatile bituminous coal,anthracite. It was found that brown coal thermo-oxidative destruction leads to formation of small d = 32 nm( V = 17%) and large d = 122 nm( V = 11%) fractions of nanoparticles. The thermo-oxidative destruction of bituminous coal leads to formation of nanoparticles d = 50 nm( V = 5.2%) and d = 164 nm( V = 16%). Thermooxidative destruction of low-volatile bituminous coal and anthracite leads to formation of nanoparticles,predominantly,d = 122-190 nm. Carbon nanostructures obtained from coal are negatively charged at pH= 2-12. Colloidal solution of carbon nanostructures at dispersed phase concentration 0. 01 mg/mL is stable for 1 month. Electron diffraction patterns and X-ray analysis of carbon nanostructures showed that nanostructure from brown coal is amorphous and nanostructure from anthracite is crystalline. Results of coal macromolecules modeling and graphene-like structures obtained from them are presented.

NEW METHOD FOR EFFECTIVE VISCOSITY OF COLLOIDAL DISPERSIONS WITH PERIODIC MICROSTRUCTURES

One of the central theoretical problems in the colloid field is to determine the rheological relation between the macroscopic properties of colloidal suspensions and the microstructures of the systems. In this work, the authors develop a method of transformation field by which one call calculate the effective viscosity of an incompressible: viscous fluid containing colloidal particles (either solid particles: or liquid drops) fixed at the points of a periodic lattice. The effective viscosity of a colloidal dispersion of spherical particles is calculated. The predictions of the theory are in good agreement with the Einstein's formula for suspensions and the Taylor's formula for emulsions at low particle concentrations. At higher particle concentrations, the theory reproduces the results of Nunan and Keller. The method is also applicable to the viscosity of colloidal systems with non-spherical particles.

CURRENT COLLOIDAL DISPERSION GELS ARE NOT SUPERIOR TO POLYMER FLOODING

The suggestion that the colloidal-dispersion-gel (CDG) process is superior to normal polymer flooding is misleading and generally incorrect. Colloidal dispersion gels, in their present state of technological development, should not be advocated as an improvement to, or substitute for, polymer flooding. Gels made from aluminum-citrate crosslinked polyacrylamides can act as conventional gels and provide effective conformance improvement in treating some types of excess water production problems if sound scientific and engineering principles are respected.

A THEORETICAL RESEARCH TO EFFECTIVE VISCOSITY OF COLLOIDAL DISPERSIONS

Colloidal dispersions are common in nature with wide industrial applications. One of the central theoretical problems in the field is to determine the rheological properties of the colloidal dispersion from the microstructures of the systems. Because of the difficulties associated with the boundary-value problems of the many-particle system, existing theories for colloidal suspensions are limited to low particle concentrations. In this work, a method of transformation field is developed by which one can calculate the effective viscosity of an incompressible viscous fluid containing colloidal particles ( either solid particles or liquid drops). The predictions of the theory are in goad agreement with the Einstein's formula for suspensions and the Taylor's formula for emulsions at low particle concentrations. At higher particle concentrations, the results of Nunan and Keller are produced. The method is also applicable to the viscosity of colloidal systems with non-spherical particles.

A Global Investigation About Hard Core Attractive Yukawa Approximation and Adhesive Hard Sphere Approximation for Structure of Colloidal Dispersion Systems

The accuracy of hard core attractive Yukawa (HCAY) potential and adhesivehard sphere (AH) potential in representing the structure factor of short range square well potentialand Asakura and Oosawa (AO) depletion potential is examined by comparing theoretical predictionswith the existing simulation data and the present numerical results from the non-linear optimizedrandom phase approximation closure for Ornstein—Zernike equation. For the case of square-well (SW)potential, it is shown that the structure factor of HCAY potential based on a recently proposedsemi-analytical expression for the radial distribution function can describe the structure factor ofSW potential with reduced well width λ ≤ 2 only if the reduced contact potential βε_(sw) ≤0.25, while the analytical expression for the structure factor of AH potential under Percus-Yevick(PY) approximation completely fails for the case of λ 】 1.2. For the case of AO depletionpotential, the domain of validity of both HCAY potential and AH potential is complementary. With theabove analysis and considering the solid-liquid transition of the AH potential with an adhesiveparameter τ below 1.31 cannot be predicted by modified weighted density approximation, the roleplayed by the HCAY potential about the mapping manipulation should not be ignored.

Sterically Stabilized Poly(3, 4-ethylenedioxythiophene) Colloidal Dispersions Doped with Different Sulfonic Acids

The preparation of sterically stabilized poly（3, 4-ethylenedioxythiophene）（PEDOT） colloidal dispersions doped with different sulfonic acids is described. Three different sulfonic acids, i.e., p-toluenesulfonic acid, β-naphthalenesulfonic acid and D-camphor-10-sulfonic acid are used, facilitating the preparation of sterically stable PEDOT colloidal particles. The influences of the dopants and concentration of polymeric stabilizer on the yields, morphologies and electrical properties of the resultant colloidal particles were investigated. The colloidal particles with the size ranging from 172 to 334 nm have been obtained in good yields. The compressed pellet conductivity was as high as 4.5 Scm^-1

Real-time observation of template-assisted colloidal aggregation and colloidal dispersion under an alternating electric field

A fascinating colloid phenomenon was observed in a specially designed template-assisted cell under an alternating electrical field. Most colloidal particles experienced the processes of aggregation, dispersion and climbing up to the plateaus of the patterns pre-lithographed on the indium tin oxide glass as the frequency of the alternating electrical field increased. Two critical frequencies fcritl ≈ 15 kHz and fcrit2 ≈ 40 kHz, corresponding to the transitions of the colloid behaviour were observed. When f 〈 15 kHz, the particles were forced to aggregate along the grooves of the negative photoresist patterned template. When 15 kHz 〈 f 〈 40 kHz, the particle clusters became unstable and most particles started to disperse and were blocked by the fringes of the negative photoresist patterns. As the frequency increased to above 40 kHz, the majority of particles started to climb up to the plateaus of the patterns. Furthermore, the dynamics analysis for the behaviour of the colloids was given and we found out that positive or negative dielectrophoresis force, electrohydrodynamic force, particle-particle interactions and Brownian motion change with the frequency of the alternating electric field. Thus, changes of the related forces affect or control the behaviour of the colloids.

An oxygenating colloidal bioink for the engineering of biomimetic tissue constructs

Ensuring a sufficient oxygen supply is pivotal for the success of bioprinting applications since it fosters tissue integration and natural regeneration.Variation in oxygen concentration among diverse tissues necessitates the precise recreation of tissue-specific oxygen levels in imprinted constructs to support the survival of targeted cells.Although oxygen-releasing biomaterials,such as oxygen-generating microparticles(OMPs),have shown promise for enhancing the oxygen supply of microenvironments in injured tissues,whether this approach is scalable for large tissues and whether tissue-specific bioinks with varying OMP concentrations remain printable remain unknown.This study addresses this critical gap by introducing an innovative class of engineered oxygenated bioinks that combine colloidal-based microgels with OMPs.We report that incorporating nanosized calcium peroxide(nCaO_(2))and manganese oxide nanosheets(nMnO_(2))into hydrophobic polymeric microparticles enables precise modulation of oxygen release while controlling hydrogen peroxide release.Moreover,the fabrication of oxygenating and cytocompatible colloidal gels is achieved using an aqueous two-phase system.This study thoroughly evaluates the fundamental characteristics of the resulting bioink,including its rheological behaviors,printability,shape fidelity,mechanical properties,and oxygen release properties.Moreover,this study demonstrates the macroscopic scalability and cytocompatibility of printed constructs produced via cell-laden oxygenating colloidal bioinks.By showcasing the effectiveness of extrusion-based bioprinting,this study underscores how it can be used to fabricate biomimetic tissues,indicating its potential for new applications.The findings presented here advance the bioprinting field by achieving scalability with both high cell viability and the possibility of mimicking specifically oxygenated tissues.This work thereby offers a promising avenue for the development of functional tissues with enhanced physiological relevance.

Tunable dispersion relations manipulated by strain in skyrmion-based magnonic crystals

We theoretically investigate the propagation characteristics of spin waves in skyrmion-based magnonic crystals. It is found that the dispersion relation can be manipulated by strains through magneto-elastic coupling. Especially, the allowed bands and forbidden bands in dispersion relations shift to higher frequency with strain changing from compressive to tensile,while shifting to lower frequency with strain changing from tensile to compressive. We also confirm that the spin wave with specific frequency can pass the magnonic crystal or be blocked by tuning the strains. The result provides an advanced platform for studying the tunable skyrmion-based spin wave devices.

Pipeline thickness estimation using the dispersion of higher-order SH guided waves

Thickness measurement plays an important role in the monitoring of pipeline corrosion damage. However, the requirement for prior knowledge of the shear wave velocity in the pipeline material for popular ultrasonic thickness measurement limits its widespread application. This paper proposes a method that utilizes cylindrical shear horizontal(SH) guided waves to estimate pipeline thickness without prior knowledge of shear wave velocity. The inversion formulas are derived from the dispersion of higher-order modes with the high-frequency approximation. The waveform of the example problems is simulated using the real-axis integral method. The data points on the dispersion curves are processed in the frequency domain using the wave-number method. These extracted data are then substituted into the derived formulas. The results verify that employing higher-order SH guided waves for the evaluation of thickness and shear wave velocity yields less than1% error. This method can be applied to both metallic and non-metallic pipelines, thus opening new possibilities for health monitoring of pipeline structures.

Discontinuities of Banana Integrals in Dispersion Relation Representation

We derive the discontinuities of banana integrals using the dispersion relation iteratively,and find a series of identities between the parameterized discontinuities of banana integrals(p-DOBIs).Similar to elliptic integrals,these identities enable the reduction of various p-DOBIs to be a linear combination of some fundamental ones.We present a practical application of p-DOBIs for deriving the Picard–Fuchs operator.Then we establish the expression of generalized dispersion relation,which enables us to obtain the dispersion relation representation of arbitrary banana integrals.Moreover,we propose a hypothesis for generalized dispersion relation and p-DOBIs,which provides a simple way to calculate the discontinuities and transform dispersion relation representation to p-DOBIs.

A simple atomization approach enables monolayer dispersion of nano graphenes in cementitious composites with excellent strength gains

Carbon nano additives(CNAs)are critical to achieving the unique properties of functionalized composites,however,controlling the dispersion of CNAs in material matrix is always a challenging task.In this study,a simple atomization approach was successfully developed to promote the dispersion efficiency of graphene nanoplatelets(GNPs)in cement composites.This atomization approach can be integrated with the direct,indirect and combined ultrasonic stirrings in a homemade automatic stirring-atomization device.Mechanical and microstructure tests were performed on hardened cement pastes blended with GNPs in different stirring and mixing approaches.Results show that the direct ultrasonic stirrings enabled more homogeneous dispersions of GNP particles with a smaller size for a longer duration.The atomized droplets with the mean size of~100μm largely mitigated GNPs’agglomerations.Monolayer GNPs were observed in the cement matrix with the strength gain by up to 54%,and the total porosity decrease by 21%in 0.3 wt%GNPs dosage.The greatly enhanced dispersion efficiency of GNPs in cement also raised the cement hydration.This work provides an effective and manpower saving technique toward dispersing CNAs in engineering materials with great industrialization prospects.

Photostability of colloidal single photon emitter in near-infrared regime at room temperature

The photostability of a colloidal single photon emitter in near-infrared regime at room temperature is investigated.The fluorescence lifetime,blinking phenomenon,and anti-bunching effect of a single CdTeSe/ZnS quantum dot with an emission wavelength of 800 nm at room temperature are studied.The second-order correlation function at zero delay time is much smaller than 0.1,which proves that the emission from single quantum dots at 800 nm is a highly pure single-photon source.The effects of the irradiation duration on the fluorescence from single quantum dots are analyzed.The experimental results can be explained by a recombination model including a multi-nonradiative recombination center model and a multi-charged model.

Dispersion Relations in Diffraction in Time

In agreement with Titchmarsh’s theorem, we prove that dispersion relations are just the Fourier-transform of the identity, g(x′)=±Sgn(x′)g(x′), which defines the property of being a truncated functions at the origin. On the other hand, we prove that the wave-function of a generalized diffraction in time problem is just the Fourier-transform of a truncated function. Consequently, the existence of dispersion relations for the diffraction in time wave-function follows. We derive these explicit dispersion relations.

Real-time data processing method for CO_(2) dispersion interferometer on EAST

A real-time data processing system is designed for the carbon dioxide dispersion interferometer(CO_(2)-DI)on EAST.The system utilizes the parallel and pipelining capabilities of an fieldprogrammable gate array(FPGA)to digitize and process the intensity of signals from the detector.Finally,the real-time electron density signals are exported through a digital-to-analog converter(DAC)module in the form of analog signals.The system has been successfully applied in the CO_(2)-DI system to provide low-latency electron density input to the plasma control system on EAST.Experimental results of the latest campaign with long-pulse discharges on EAST(2022–2023)demonstrate that the system can respond effectively in the case of rapid density changes,proving its reliability and accuracy for future electron density calculation.

CFD-PBM coupled modeling of the liquid-liquid dispersion characteristics and structure optimization for Kenics static mixer

Kenics static mixers(KSM)are extensively used in industrial mixing-reaction processes by virtue of high mixing efficiency,low power homogenization and easy continuous production.Resolving liquid droplet size and its distribution and thus revealing the dispersion characteristics are of great significance for structural optimization and process intensification in the KSM.In this work,a computational fluid dynamics-population balance model(CFD-PBM)coupled method is employed to systematically investigate the effects of operating conditions and structural parameters of KSM on droplet size and its distribution,to further reveal the liquid-liquid dispersion characteristics.Results indicate that higher Reynolds numbers or higher dispersed phase volume fractions increase energy dissipation,reducing Sauter mean diameter(SMD)of dispersed phase droplets and with a shift in droplet size distribution(DSD)towards smaller size.Smaller aspect ratios,greater blade twist and assembly angles amplify shear rate,leading to smaller droplet size and a narrower DSD in the smaller range.The degree of impact exerted by the aspect ratio is notably greater.Notably,mixing elements with different spin enhance shear and stretching efficiency.Compared to the same spin,SMD becomes 3.7-5.8 times smaller in the smaller size range with a significantly narrower distribution.Taking into account the pressure drop and efficiency in a comprehensive manner,optimized structural parameters for the mixing element encompass an aspect ratio of 1-1.5,a blade twist angle of 180°,an assembly angle of 90°,and interlaced assembly of adjacent elements with different spin.This work provides vital theoretical underpinning and future reference for enhancing KSM performance.

Effect of trigger system on experimental dispersion characteristics of active surface wave testing

A trigger system is typically employed in active seismic testing to trigger and synchronize multichannel surface wave data acquisition.The effect of the trigger system on the dispersion image of surface waves is empirically known to be negligible,however,theoretical explanation regarding the effect of the trigger system is insufficient.This study systematically examines the theory for surface wave dispersion analysis and proves that the effect of the trigger system on a dispersion image is negligible via a solid theoretical explanation.Subsequently,based on the new theoretical explanation,an alternative method that uses only the relative phase difference between sensors to extract dispersion characteristics with better conceptual clarity is proposed.Two active surface wave testing cases are considered to validate the theory and method.The results indicate that(1)an accurate trigger system is not necessary for surface wave data acquisition,and(2)it is unnecessary to assume that the impact point is the generation point of the surface waves for the experimental dispersion analysis.