Injection Experiments Research Articles

Experimental investigation on heat and moisture transfer of propylene glycol-mixed steam in porous media

Propylene glycol (PG)-mixed steam enhanced extraction is a promising remediation technique for removing semi-volatile organic compounds (SVOCs) from the unsaturated zone. However, the mechanisms of heat and moisture transfer during PG-mixed steam injection remain unclear. In this study, a 2D experimental system was developed to enable non-invasive monitoring of the spatio-temporal distribution of temperature and degree of saturation during steam injection into porous media. Experiments were conducted to observe the migration of PG-mixed steam in horizontal and vertical planes across three varying particle sizes, while pure superheated steam injection experiments serving as a comparison. Temperature field results show that the addition of PG decreases the zone of influence during steam migration, while significantly enhancing the emergence of the superheated steam zone. The influence of particle size on the area variance of the saturated steam zone is greater than that of the superheated steam zone. The downward migration of the superheated steam front due to density different between PG vapor and air is impeded with decreasing permeability. Furthermore, saturation field results reveal that the condensed liquid within the superheated zone is a PG solution. The downward migration of condensates with high PG concentration might increase the potential risk of beneath groundwater pollution, highlighting the significance of understanding PG migration during PG-mixed steam injection.

Full-torus impurity transport simulation in boron powder injection experiments in the Large Helical Device

The toroidal distribution of boron deposition on plasma-facing components (PFCs) in boron powder injection using an impurity power dropper (IPD) was investigated by full-torus simulation and observations in a systematic plasma density-scan experiment. The images of the ablation of dropped boron powders observed with a visible CCD camera were consistently explained by the simulations of the ablation positions of the boron powders considering the size distribution. Simulations assuming full-torus boron deposition on the PFCs did not reproduce the observed intensity profile of boron emission lines for higher plasma densities. It indicated that the density of boron deposited on PFCs installed toroidally far from the IPD was low for higher plasma densities due to the change in the ablation positions of the boron powders toward the outboard side. The experimental results verified the previous full-torus simulation of the toroidal distribution of the boron deposition in both lower and higher plasma densities.

Investigation of the pore structure characteristics and fluid components of Quaternary mudstone biogas reservoirs: a case study of the Qaidam Basin in China

Quaternary mudstone biogas reservoirs in the Qaidam Basin have shown great potential. However, complex pore structures with high clay contents and high heterogeneity limit the understanding of the storage and migration principles of these reservoirs. In this paper, HPMI and nitrogen adsorption experiments, in combination with NMR experiments under water saturation, centrifugation, various drying temperatures and other conditions, were adopted to determine the pore structure characteristics. Specifically, the reservoir space types and pore radius distribution characteristics were clarified. The cutoff values for different types of pores were identified based on the water-saturated mudstone NMR T2 spectra for full aperture distribution scales jointly characterized by mercury injection and nitrogen adsorption experiments. Furthermore, the three pore components and the saturation of different fluids were obtained. The research results indicate that the mudstone biogas reservoir has developed various reservoir spaces, and the pore size is primarily in the micronanometer range. The average total porosity reaches 27.28%, but the proportion of movable water pores is only 9.23% with poor fluid mobility, and the fluids in the pores are mostly capillary-bound water and clay-bound water. Among the different lithologies, argillaceous sand is more likely to become a good production layer.

Quantifying aquifer heterogeneity using superparamagnetic DNA particles

Identifying and determining hydraulic parameters of physically heterogeneous aquifers is pivotal for flow field analysis, contaminant migration and risk assessment. In this research, we applied a novel uniquely sequenced DNA tagged superparamagnetic silica microparticles (SiDNAmag) to quantify hydraulic parameters and associated uncertainties of a heterogeneous sand tank. In the sand tank with lens shaped heterogeneity, we conducted three sets of multi – point injection experiments in unconsolidated (1) homogeneous (zone 0), (2) heterogeneous with a no-conductivity-zone (zone 1), and (3) heterogeneous with a high-conductive-zone (zone 2). From the breakthrough curves (BTC), we estimated the parameters distributions of hydraulic conductivity (k), effective porosity (ne), longitudinal dispersivity (αL), transverse vertical (αTV), and transverse horizontal dispersivities (αTH) applying Monte Carlo simulation approach for BTC fitting. The estimated parameters and associated uncertainties for each of the heterogeneous sections were further statistically compared (distribution non-specific Mann Whitney U test) these parameter distributions with parameter distributions estimated from the conservative salt tracer. While the time of arrival and time to peak concentration of SiDNAmag and salt in effluent were comparable, peak concentration of SiDNAmag was 1–3 log reduced as compared to the salt tracer due to first order kinetic attachment. Nonetheless, the parameters and associated uncertainty distributions (5 %–95 %) of K, ne, αL, αTV, and αTH, determined from SiDNAmag BTCs were statistically equivalent to the salt tracer in all three experiment systems. Through our experimental and modelling approach, our work demonstrated that in a coarse to very coarse grain sand medium, with lens shaped heterogeneity, the uniquely sequenced SiDNAmag were a promising tool to identify heterogeneity and determine hydraulic parameters and associated uncertainty distributions.

Study on the effect of morphology of anthracite coal containing through-fracture on CO2 enhanced coalbed methane recovery

When CO2 is injected into the coal seam, different forms of fractures within the coal have different effective diffusion areas and distribution characteristics for the gas, affecting methane's adsorption-desorption-diffusion and seepage behavior. In this study, based on the control experiments of the intact coal sample, CO2 injection experiments were carried out on three groups of coals containing through-fracture to investigate the influence of fracture morphology on CO2-enhanced coalbed methane recovery behaviors and to discuss and analyze the changes in the volume of the coal samples, the composition of the tailing gas, and the changes in the permeability during the gas injection process. The results show that: the existence of fractures has an inhibitory effect on the volume expansion after gas adsorption of the coal, and the larger the surface area of fractures, the more obvious inhibitory effect, and at the same time, the faster the strain rate; the breakthrough time of CO2 in the fractured coal samples is much shorter than that in the intact samples; the increase in the surface area of the fractures and uniformity of distribution can enhance the concentration of CH4 in the tail gas, and in the pre-injection stage, uniformity of the distribution of the fractures is more important than the surface area of the fractures in increasing the output CH4 concentration; the magnitude of permeability change and the change rate of the coal samples during CO2 injection increased with the increase in the fracture surface area of the coal samples.

Micromechanical properties and fractal homogenization of coal based on nanoindentation

Distinct from hard rock, coal is relatively soft and fragmented. It is not only challenging to prepare test coal samples that meet the requirements of standard mechanical experiments but also impossible to recycle them for repeated testing. There is an urgent need to explore new mechanical testing methods to enhance the study of the mechanical properties of coal. In this study, the micromechanical parameters of the coal matrix solid phase were acquired through targeted nanoindentation technology. The elemental composition, surface morphology, and pore structure characteristics of each indentation point were determined by energy dispersive spectrometer, optical microscope observation, and high-pressure mercury injection experiments. The fractal homogenization equation is deduced based on fractal geometry and the Mori–Tanaka method. The validity of the fractal homogenization approach is verified by integrating the micromechanical parameters and pore structure characteristics of coal, and the impact of the microstructural parameters on the macroscopic mechanical properties of coal is discussed. The results show that the proportion of clay minerals in the solid phase of the coal is the greatest (81.18%), with the main mineral components being kaolinite and illite. The elastic modulus is 1.974 ± 1.036 GPa, the hardness is 0.131 ± 0.108 GPa, and the ratio of upper and lower pore scales conforms to the fractal calibration rate. The macroscopic equivalent elastic modulus rises along with the increase in the fractal dimension. When the fractal dimension is constant, the macroscopic equivalent elastic modulus decreases with the increase in λmin/λmax and increases with the increase in solid phase elastic modulus.

The effect of CD4 injection on WD molecule sputtering at the divertor target in EAST

Tungsten (W) is one of the preferred plasma-facing materials for future fusion reactors because of the advantages of high melting point, low physical sputtering rate and low fuel retention. The lifetime and service performance of W materials are limited by erosion processes. In recent years, tungsten deuteride molecular (WD) sputtering has been discovered in tokamak. Studying WD sputtering helps to better understand the erosion of tungsten materials in tokamak. EAST adopts the method of injecting impurity gas in the divertor to alleviate the particle flux and heat flux bombarding the tungsten divertor, and CD4 is one of the impurities used. CD4 injection experiments on EAST show that after CD4 is injected from the upper outer (UO) divertor target, despite that the electron temperature (Te) around the strike point on the UO divertor target drops to about 8 eV, strong WD sputtering occurs in the far scrape-off layer (SOL) region. The divertor probe data shows that after CD4 injection, the particle flux from the upstream plasma onto the divertor split into two bands, creating a new particle flux strike point in the far SOL region. The energy of incident particles at the original strike point is significantly reduced, while the energy of incident particles at the far SOL region is enhanced. The edge electron density profile at mid-plane indicates that CD4 injection causes an increase of density in the SOL, which could improve the coupling of Lower-Hybrid Wave (LHW) with the edge plasma as evidenced by the decreasing reflected power of LHW. The increase in absorbed power of LHW could change the particle and energy transport in the edge plasma, thus plays an important role in the enhanced WD sputtering in the far SOL region after CD4 injection.

Characteristics and main controlling factors of the Sangonghe tight sandstone reservoirs in the Shengbei Sub-sag of the Turpan-Hami basin, China

The Sangonghe tight sandstone hydrocarbon reservoirs in the Shengbei Sub-sag of the Turpan-Hami Basin are key areas for hydrocarbon exploration. However, previous research has mostly focused on petrological characteristics, physical properties, and pore types. There is a lack of understanding regarding diagenesis, microscopic pore-throat features, and the impact of overpressure on the reservoir. This gap in knowledge poses a disadvantage for future studies and hydrocarbon exploration. This study examines the Sangonghe tight sandstone hydrocarbon reservoirs in the Shengbei Sub-sag of the Turpan-Hami Basin. It combines cast thin sections, physical property tests, high-pressure mercury injection experiments, low-temperature nitrogen adsorption experiments, and well logging overpressure identification to investigate the basic characteristics, diagenesis, and microscopic pore-throat features of these reservoirs. Based on this analysis, the study identifies the main controlling factors of the reservoir properties and presents three key findings. First, the reservoir rocks are primarily composed of lithic sandstone and feldspathic lithic sandstone with porosity ranging from 4% to 10% and permeability ranging between 0.1 and 10 mD, classifying it as a low-porosity, low-permeability tight sandstone reservoir. Second, the reservoir has undergone several diagenetic processes, with significant compaction and common occurrences of cementation and metasomatism. Acidic dissolution is the main dissolution process, but it is relatively weak. The pore-throat system exhibits poor and concentrated sorting, with nanometer-sized pores being predominant. These include 'ink-bottle' pores with narrow necks and wide bodies, and parallel plate-structured fissure pores. Finally, the development of the reservoirs is mainly influenced by sedimentation, dissolution, and overpressure. The parent rock provenance features a high content of stable heavy minerals, larger grain sizes, and thicker sand body layers. These factors enhanced the reservoir's resistance to compaction and promoted the development of primary intergranular pores. Additionally, organic acid fluids caused extensive dissolution of feldspar and lithic fragments, resulting in the formation of numerous secondary dissolution pores. Additionally, under-compaction overpressure helped preserve primary pores, while hydrocarbon generation overpressure extended the hydrocarbon generation period. This extended period provided the driving force for fluid migration, enhanced the transformation of reservoir space, and aided in hydrocarbon accumulation.

Prediction of Capillary Pressure Curves Based on Particle Size Using Machine Learning

Capillary pressure curves are usually obtained through mercury injection experiments, which are mainly used to characterize pore structures. However, mercury injection experiments have many limitations, such as operation danger, a long experiment period, and great damage to the sample. Therefore, researchers have tried to predict capillary pressure data based on NMR data, but NMR data are expensive and unstable to obtain. This study aims to accurately predict capillary pressure curves. Based on rock particle size data, various machine learning methods, such as traditional machine learning and artificial neural networks, are used to build prediction models and predict different types of capillary pressure curves, aiming at studying the best prediction algorithm. In addition, through adjusting the amount of particle size characteristic data, the best amount of particle size characteristic data is explored. The results show that three correlation coefficients of the four optimal algorithms can reach more than 0.92, and the best performance is obtained using the Levenberg–Marquardt method. The prediction performance of this algorithm is excellent, with the three correlation coefficients being all higher than 0.96 and the root mean square error being only 5.866. When partial particle size characteristics are selected, the training performance is gradually improved with an increase in the amount of feature data, but it is far less than the performance of using all the features. When the interpolation increases the particle size characteristics, the best performance is achieved when the feature data volume is 50 groups and the root mean square error is the smallest, but the Kendall correlation coefficient decreases. This study provides a new way to obtain capillary pressure data accurately.

The mechanism of pore pressure and adsorption swelling effect on permeability during geological storage of carbon dioxide in coal seams

Unmineable coal seams serve as ideal sites for CO2 geological sequestration, with permeability being a critical indicator for evaluating the storage capacity of coal seams. After CO2 injection, coal seam permeability undergoes continuous changes. Higher injection pressure enhances CO2 flow capacity in the coal seam and improves the injectivity; However, it also induces significant adsorption swelling deformation in the coal, leading to a decline in coal permeability. Using the non-adsorptive gas He as a reference, isothermal-non-isobaric injection experiments were conducted to measure the strain characteristics of the coal at various distances from the injection port. Based on the experiments, a model for the evolution of pore pressure in the coal was developed, changes of apparent permeability during the injection process were calculated, and the mechanisms by which pore pressure and adsorption swelling affect permeability were elucidated. The results indicate that, within the experimental pressure range, the compression deformation of coal pore surfaces caused by pore pressure accounts for less than 3 % of the total coal deformation. However, the increase in permeability resulting from pore surface compression exceeds the reduction in permeability induced by adsorption swelling. The farther from the injection point, the lower the pore pressure and the smaller the apparent permeability of the coal. With the injection pressure increasing, the loss of pore pressure along the gas flow direction also increases. The apparent permeability of the coal is determined by the combined effects of pore pressure and adsorption swelling during CO2 injection. In the initial injection stage, pore pressure results in elastic compression deformation of the coal matrix, leading to a rapid increase in apparent permeability. Permeability gradually reduces due to adsorption swelling. Higher injection pressure results in greater elastic compression deformation of the coal pore surfaces, which increases pore aperture and permeability.

I-mode plasma confinement improvement by real-time lithium injection and its classification on EAST tokamak

Abstract I-mode is a promising regime for future fusion reactors due to the high energy confinement and the moderate particle confinement. However, the effect of lithium, which has been widely applied for particle recycling and impurity control, on I-mode plasma is still unclear. Recently, experiments of real-time lithium powder injection on I-mode plasma have been carried out in EAST Tokamak. It was found that the confinement performance of the I-mode can be improved by the lithium powder injection, which can strongly reduce electron turbulence (ET) and then trigger ion turbulence (IT). And it was observed that the ET intensity is inversely proportional to the velocity shear, which suggests that the injection of lithium powder leads to a gradual enhancement of the shear flow, whereby the turbulence is reduced and consequently the confinement is improved. Four different regimes of I-mode have been identified in EAST. The Type I I-mode plasma is characterized by the weakly coherent mode (WCM) and the geodesic-acoustic mode (GAM). The Type II I-mode is featured as the WCM and the edge temperature ring oscillation (ETRO). The Type III I-mode corresponds to the plasma with the co-existence of ETRO, GAM, and WCM. The Type IV I-mode denotes the plasma with only WCM but without ETRO and GAM. It was observed that the WCM intensity is increased with lithium powder injection by the confinement improvement/pedestal temperature increase. EAST experiments demonstrate that lithium powder injection is an effective tool for real-time control and confinement improvement of I-mode plasma.

In-situ activation of persulfate by emplaced magnetite nanoparticles for degradation of 1,2-dichloroethane in porous media

In this study, column experiments were conducted to explore on the method of emplacement of magnetite nanoparticles (MNPs) for in situ activation of persulfate (PS) in sand porous media to degrade 1,2-dichloroethane (DCA), a typical recalcitrant chlorinated compound. Different molar ratios between PS and DCA (0:1, 2:1, 5:1 and 20:1) and mass contents of MNPs in the sand (0 %, 1.9 % and 5.4 %) were tested. In the absence of MNPs, degradation of DCA was negligible for a hydraulic retention time of 7 h. Presence of MNPs at the content of 1.9 % enhanced degradation of DCA and the highest removal efficiency (34.2 %) was observed at the PS-to-DCA molar ratio of 5:1. At the MNPs content of 5.4 %, increase of the PS-to-DCA molar ratio from 2:1 to 20:1 lead to not only increase in DCA removal efficiency but also substantial enhancement in chloride production, indicating that high PS concentration could cause significant degradation of the Cl-containing intermediates. In contrast to MNPs, Fe3O4 solids with much larger size (∼1 μm) were much less effective in activating PS for DCA removal even at a significantly higher content in the medium. The transport data could be well fitted by the one-site chemical nonequilibrium model, which showed kinetic DCA sorption to the MNPs as a key process for the transport. In the long-term injection experiment, a stable and significant removal of DCA (∼50 %) was observed for 254 days at the MNP content of 1.9 %. The results of this study show the potential of MNPs as a sustainable PS activator in injection-based in situ chemical oxidation for groundwater remediation.

Simulation of DIII-D disruption with argon pellet injection and runaway electron beam

Abstract The next generation of large tokamaks, including ITER, will be equipped with a disruption mitigation system (DMS) that can be activated if a disruption is deemed to be imminent. Introducing impurities by pellet (large or shattered) or massive gas injection has been shown to be an effective mitigation mechanism on many tokamaks. The goal of the mitigation is to lessen the thermal and electromagnetic loads from the disruption without generating enough high-energy (runaway) electrons to damage the device. Variations of this mitigation process with impurity injection are presently being tested on many experiments. We have modeled one such impurity injection experiment on DIII-D using the M3D-C1 nonlinear 3D extended MHD code (Jardin et al 2012 Comput. Sci. Discovery 6 014002), The model includes an argon large pellet injection and ablation model, impurity ionization, recombination, and radiation, and runaway electron formation and subsequent evolution, including both Dreicer and avalanche sources. We obtain reasonable agreement with the experimental results for the timescale of the thermal and current quench and for the magnitude of the runaway electron plateau formed during the mitigation. This is the first 3D full MHD simulation with pellets and REs to simulate the disruption process and it also provides a partial validation of the M3D-C1 DMS model.

Numerical simulation of co-firing LRC and ammonia in Pangkalan Susu 3 & 4 coal-fired steam power plant (CFSPP) capacity 210 megawatts

The effort to reduce CO2 and NOx emissions plays a crucial role in mitigating climate change, improving air quality, complying with environmental regulations, and promoting clean technology innovation. Ammonia, as an emission-free fuel, shows significant potential as a co-firing agent with Coal in coal-fired steam power plants (CFSPP). Previous studies have demonstrated promising results in emission reduction through ammonia co-firing. This research presents a numerical analysis based on Computational Fluid Dynamics (CFD) to investigate the co-firing of ammonia with low-calorific Coal (LRC) in the CFSPP Pangkalan Susu Units 3 and 4, with a capacity of 210 MW. The study employs fluid flow modelling and chemical reaction analysis using the Discrete Phase Model (DPM) to provide accurate predictions of temperature distribution and pollutant concentrations in pulverized coal boilers. Cofiring simulations were conducted with ammonia additions of 5 % and 15 % on a calorific basis. Injection experiments from each burner (A-D) were performed to identify the optimal injection location. The simulation results indicate changes in combustion characteristics, particularly in temperature distribution. The main finding reveals a temperature decrease when ammonia is added as a co-firing material, attributed to the higher H2O content, which leads to increased moisture losses. In terms of efficiency, co-firing showed a decline compared to the baseline combustion of 100 % LRC coal due to the more significant moisture losses. The highest reduction in CO2 emissions was observed when 15 % ammonia was injected from burner B in case #6, with a mass fraction value of 0.171 at the boiler outlet. Similarly, the most significant reduction in NOx emissions occurred with a 15 % ammonia co-firing from burner B, yielding a mass fraction value of 8.81E-04 at the boiler outlet. This co-firing technology is expected to enhance decarbonization efforts and optimize the use of renewable energy in the future.

Integrated Permeability Stress Sensitivity Studies of Multi-cycle Injection and Production for Underground Gas Storage

Abstract This paper details the design of multi-cycle injection and production stress simulation experiments, aimed at quantitatively characterizing the permeability stress sensitivity in underground gas storage(UGS) during multiple operation cycles. Derived from the reservoir sensitivity evaluation method and the stress sensitivity coefficient method, a suite of stress sensitivity evaluation index was introduced to discuss the effect of stress variation paths on the stress sensitivity characteristics. It is found out that the stress sensitivity is common in sampled gas storage cores. Meanwhile, there is a significant stress sensitivity hysteresis effect in multi-cycle injection and withdrawal experiments. After multiple cycles, the rock stress sensitivity is less dependent on the stress path. However, due to the superposition of multiple cycle stress sensitive hysteresis effect, the multi-cycle permeability damage ratio and irreversible damage ratio increased. The phenomenon of stress sensitivity hysteresis is especially pronounced in cores with low permeability. This study offers a theoretical foundation for predicting gas storage operation schemes and formulating technical policies.

Study on reservoir heterogeneity of Chang 8 reservoir in Hongde Oilfield, western margin of Ordos Basin and knowledge of fine stratification development practice

Abstract In view of the problems of reservoir heterogeneity and unclear understanding of main control factors in Chang8 reservoir of Hongde Oilfield in the middle part of Tianhuan, Ordos Basin, efficient development and stable production are restricted by a large number of drilling, core data and log comparative analysis, using core observation, microscopic rock slice identification, scanning electron microscopy, mercury injection and phase infiltration experiments, etc. Based on the understanding of sedimentary facies and diagenesis, the quantitative analysis of Chang 8 in the study area is carried out from the macro intra-layer, interlayer, plane heterogeneity and microscopic heterogeneity. Finally, it is concluded that Chang 8 reservoir in Hongde Oilfield presents strong heterogeneity, and sedimentary microfacies, different clastic components of sandstone, diagenesis and other main factors affecting its strong heterogeneity. At the same time, in the development practice of De 5 area of Hongde Oilfield, the multi-stage sedimentary cycle division and step production and development were taken as a breakthrough, and the differential reservoir seepage theory was innovatively used to reduce the section/plane contradiction caused by reservoir heterogeneity, and a technical system such as regional fine stratified production, differentiated reservoir fracturing and reconstruction, single sand body fine injection and production control and stratified water injection was formed. The high efficiency development and utilization of strong heterogeneous reservoir is realized.

Research and Field Application on Extreme Subdivision Water Injection Technology for Low Permeability Reservoirs

Abstract Low permeability Block A is about to enter the development phase of extremely high water cut. Due to the low overall recovery degree and residual oil scattered sporadically, the efficient development meets more difficulty and conventional residual oil analysis and adjustment methods cannot fulfil the current needs of precise development. To enhance the reservoir utilization degree, we conduct extremely concise zonal water injection experiment from three aspects: sand body description, policies establishment, and proper technique application. In terms of sand body description, four types of sand-body distribution patterns were summarized through fine characterization of vertical, planar, and spatial single sand bodies, clarifying the origin and potential distribution of residual oil. In terms of development policy, numerical simulation and reservoir engineering methods have been comprehensively applied to determine the subdivision combination of injection layers and reasonable water allocation boundaries, and subdivision principles have been established, considering single septation to thin and thick layer with combining enhancing -controlling. In terms of supporting technology, we have studied the small space subdivision process of small compartments, optimized the testing and adjustment methods, and finally achieved accurate separation, strict clamping, and accurate matching of water injection layers. Through the research and practice, it realized the finest septation of the water injection to extremely enhance the subdivision degree and the efficiency of the injection. It also have strengthened the utilization of thin and poor layers and effectively controlled the decline.

Determination method and application of variable T2 cutoff value in nuclear magnetic logging

Abstract Nuclear magnetic resonance logging (NMR) is a new logging technology. By inversion of relaxation time T2 spectrum, pore characteristics can be directly measured, independent of the influence of rock skeleton minerals, and parameters such as effective porosity, movable fluid porosity, bound water porosity, pore size distribution and permeability can be calculated. The key parameter for calculating fine pore structure is the critical relaxation time of bound water and mobile fluid, namely the T2 cutoff value. The current T2 cutoff value is a fixed value based on the T2 mean value corresponding to the flowable porosity (permeability contribution porosity) in the mercury injection experimental data. However, according to the analysis of mercury injection data, there are differences in the flowable porosity of cores with the same porosity and permeability under the same pressure difference. Based on the synchronous data of nuclear magnetic logging and core mercury injection experiment, this paper establishes a variable T2 cutoff value determination method, which significantly improves the interpretation accuracy of nuclear magnetic logging and lays a foundation for the important application of nuclear magnetic logging in reservoir fine description.

Impact of Magnetic Fields on the Efficiency of Dense Non-Aqueous Phase Liquid Removal from Unsaturated Zones Using Steam Injection

Unsaturated zone is of great importance in providing water and nutrients that are vital to the biosphere and the main factor controlling water movement from the land surface to the aquifer. Contamination of unsaturated zone by Dense Non-Aqueous Phase Liquids (NAPLs) has becoming major threat to human environment as a result of increasing concern with industrialization. The use of steam injection for remediation of porous media which are contaminated by DNAPLs has not given the desire recovery efficiency, hence the need for improvement in recovery efficiency has been a subject of continuous study. This study investigated the effect of magnetic field on the removal of DNAPL from unsaturated zone using steam injection. An unsaturated zone of a sand box of interior dimensions 110 x 74 x 8.5 cm was polluted at different periods with 200 ml of Carbon tetrachloride. Steam injection experiment with flow rate of 0.01 m3/s was performed to determine the recovery efficiencies of Carbon tetrachloride in an unsaturated zone containing sand of porosity 0.42 and permeability of 0.001163779 cm/s. Magnetic field in step of 1 Tesla (T) was introduced from 1-3 Tesla (T) into experiment. The effects of magnetic field on removal of DNAPL from unsaturated zone using steam injection only and steam injection with magnetic field were compared using descriptive statistic. The recovery efficiency of Carbon tetrachloride using steam injection only was 82.05 %, while that with varying magnetic field at 1T, 2T and 3T were 89.45%, 94.95% and 95.35% respectively. The recovery efficiency of steam injection with varying magnetic field at 1T, 2T and 3T were 9.02, 15.72, 16.21% higher than the result of steam injection only for Carbon tetrachloride. The result demonstrated the ability of steam injection to recover contaminants from the subsurface. The application of magnetic field as an aid to facilitate system activities has been signifi-cantly effective due to its ability to overcome the constraints of conventional treatment processes. A combined application of steam injection with magnetic field appreciably enhances the removal of Non Aqueous phase liquids from Unsaturated Zone.

Experimental study on the heat storage characteristics of rock bed heat storage system with different packing structure

Establishing energy storage systems can provide an effective solution to the challenges posed by the variability and intermittency of renewable energy sources. Among the available options for energy storage, rock-packed bed thermal energy storage systems are widely favored for their performance, cost-effectiveness, and reliability. The more compact the rock packing, the more adequate the heat exchange of the system; however, poorer permeability increases fluid friction losses and pressure drop, which is detrimental to heat transport within the system. The permeability and heat exchange of the system jointly determines its thermal energy storage performance. This study proposes a composite packing scheme utilizing intact rock slabs and broken rock to enhance the thermal energy storage performance of the packed bed. This approach aims to augment heat exchange efficiency and elevate energy storage density while maintaining the bed's commendable permeability. Heat injection and heat extraction experiments of rock beds were conducted to study the heat storage characteristics of the rock-packed bed thermal storage system under different packing structure. In addition, this study investigates the effect of different injection pressures on the storage and release of heat in the system. The results show that the volume of the pore space of the filled bed, serving as the primary domain for gas flow and gas-rock heat exchange, is a decisive factor affecting the packed bed's permeability and heat exchange performance. When the porosity of the packed bed increased from 5.5 % to 9.9 %, its permeability increased from 1.42 × 10−13 m2 to 3.20 × 10−13 m2, yet the thermal exchange efficiency declined from 67.2 % to 65.3 %. Reasonably arranging intact rock slabs and broken rock fill can alter the path of heat transfer within the packed bed, thereby effectively enhancing its heat storage and release performance. For the same pore volume conditions, the heat exchange efficiency of the packed bed is increased by about 10 % by increasing the number of layers of broken rock fill. Additionally, high gas injection pressures can facilitate heat storage and release processes, but it does not mean that this is more efficient. The research findings can guide the selection of packing and injection schemes in packed bed thermal energy storage systems.