Alternative Injection Research Articles

Size-dependent reactivity of Rh cationic clusters to reduce NO by CO in the gas phase at high temperatures.

The reactivity of the reduction of NO pre-adsorbed on Rh2-9+ clusters by CO was investigated using a combination of an alternate on-off gas injection method and thermal desorption spectrometry. The reduction of RhnNxOy+ clusters by CO was evaluated by varying the CO concentration at T = 903 K. Among the RhnNxOx+ clusters, the Rh3N2O2+ cluster exhibited the highest reduction activity, whereas the other clusters, Rh2,4-9NxOx+, showed lower reactivity. Density functional theory (DFT) calculations for Rh3+ and Rh6+ revealed that the rate-determining step for NO reduction in the presence of CO was NO bond dissociation through the kinetics analysis using the RRKM theory. The reduction of Rh3N2O2+ is kinetically preferable to that of Rh6N2O2+. The DFT results were in qualitative agreement with the experimental results.

Investigation of the influence of water-gas exposure modes on the efficiency of oil displacement

The purpose of the work is to analyze the efficiency of oil displacement by various agents, such as water and gas, in different modes. The methods and technologies used to increase oil recovery are considered, as well as the influence of various parameters on the efficiency of the process.The authors describe in more detail the method of water-gas exposure (VGV) using pumping-ejector systems (PES) to provide a triple effect on oil reservoirs by simultaneous or alternate injection of water and gas. Theoretical and experimental methods were used to conduct the study. The study and analysis of scientific sources on the issue of evaluating the effectiveness of oil displacement became the first stage of the study. Then laboratory tests were carried out to assess the effectiveness of oil displacement by various agents. Based on the results of the work done, it was concluded that the degree of influence of wetting processes on the final result of displacement is an extremely important factor. The uniqueness of this article lies in the study of the possibilities of using multithreaded ejectors to increase the efficiency of extraction of hydrocarbones.

Enhanced system for hydrogen storage and conversion into green methanol in a geothermal environment

Variable Renewable Energy Sources are crucial for decarbonizing industries and efficient energy storage. Hydrogen storage technologies are limited in their large-scale capabilities. PtL technology can synthesize alternative fuels like methanol, which can be used in existing energy infrastructures to produce liquid fuel. The paper presents an innovative approach for utilizing in-situ thermal energy, using a hot reservoir rock (HRR) system for methanol synthesis at high temperature and pressure in an underground large-scale natural reservoir reactor. This approach aims to integrate renewable energy technologies into a single energy generation and fuel production system, including the direct utilization of renewable sources. Solutions from the oil and gas industry can be adapted to this action, such as continuous injection, alternate injection, separate injection, or chemical flooding. Conventional geothermal reservoirs, HDR systems, and depleted hydrocarbon reservoirs can be used as “underground reactors”. However, it was also noted that there are challenges, such as catalyst distribution and the complexity of reservoir pore space.

Short-Term Reliability Assessment of Integrated Power-Gas Systems With Hydrogen Injections Using Universal Generating Function

Injecting alternative gas (e.g., green hydrogen from wind generation) into the gas system is a promising way to decarbonize the energy sector. However, the fluctuating renewable generation could lead to time-varying alternative gas injections. Then, the gas composition in the gas system may become uncertain, increasing the short-term risk of the integrated power-gas systems during the operation. This paper proposes a short-term reliability assessment approach for IPGS with alternative gas injections. First, the multi-performance and multi-state universal generating functions (UGF) are constructed to efficiently model the short-term reliability of the power-to-gas facility and the wind farm, respectively. Then, a reliability management UGF operator is proposed to minimize both load shedding and gas security violation. A set of novel reliability indices is proposed to comprehensively assess the gas security violations under uncertain gas compositions. Moreover, an analytical short-term reliability assessment approach is proposed, where the state-based sequential approximation and state-based McCormick envelope techniques are tailored and embedded. By optimizing the solution order by the system states, the nonconvexities in the reliability management optimization problem can be handled tractably without increasing the computation burden. Finally, the IEEE 24 bus Reliability Test System and the Belgium gas system are used to validate the proposed approach.

Preparation and Performance Study of Microemulsion Acid for Comprehensive Plugging Removal in Carbonate Reservoir.

Matrix acidification is one of the most effective stimulations to dissolve scales and remove damage in carbonate reservoirs. However, existing acid systems are difficult to dissolve organic and inorganic scales simultaneously, and complex multi-stage alternative injection often introduces new precipitation and damages the reservoir. Here, based on the retardation ability of emulsified acid and the stable structure of microemulsion, an oil-phase solvent was preferably selected, and the surfactant and cosurfactant were optimized to prepare an acid-in-oil type microemulsion acid capable of dissolving both organic and inorganic scales and high solubilizing for hydrochloric acid. Based on the rotating disc experiment, scale dissolution experiment and acid driving experiment, the acid-rock reaction kinetics, scale dissolution ability and acidizing and plugging removal performance of microemulsion acid in a carbonate reservoir were systematically studied and compared. The results show that Solvesso 150 (aromatic solvent) has the advantages of low toxicity, high flash point and high-scale dissolving ability. At NP-4: OP-10: A (cosurfactant) = 3:3:4, the microemulsion acid system has the strongest ability to solubilize hydrochloric acid and can solve the problem of low H+ concentration. The particle size of microemulsion acid is smaller compared to emulsified acid. At 60 °C, the mass transfer coefficient of microemulsion acid is 3.2 × 10-8 cm2/s, which is one order of magnitude less than that of emulsified acid. Microemulsion acid shows good solubility performance in dissolving organic and inorganic scales, and the comprehensive solubility of mixed scales can reach 98.28%. The stronger scale solubilization ability and lower acid-rock reaction rate enable microemulsion acid to form a thin and straight main wormhole, thus enhancing the acidizing and plugging removal effect. This study can solve the problem of poor hydrochloric acid solubilization ability of microemulsion acid to a certain extent, which provides theoretical and data support for the research and development of microemulsion acid and the efficient plugging removal technology for carbonate reservoirs.

An experimental study of CO2 injection strategies for enhanced oil recovery and geological sequestration in a fractured tight sandstone reservoir

Carbon dioxide enhanced oil recovery has been considered and tested in unconventional oil reservoirs due to its additional environmental benefits from simultaneous CO2 geological sequestration. However, it will require a proper injection strategy to overcome unfavorable sweep efficiency in CO2 displacement, which is even magnified in unconventional oil reservoirs due to strong heterogeneity caused by natural and artificial fractures. In this study, we investigated three immiscible CO2 injection strategies at reservoir conditions using tight fractured sandstone cores from the Ordos Basin, China: water alternative gas injection, cyclic CO2 injection, and CO2 foam/surfactant alternative gas injection. A pressurization and miscible CO2 injection were then added after each injection strategy to examine the influence of residual liquid distributions on the miscible displacement efficiency after the tested injection schemes. The core plugs with comparable porosity and permeability were selected, and all cores reached a similar recovery factor (∼11%) after primary CO2 flooding. We found that the cyclic CO2 injection had best performance, with the highest incremental and accumulative oil recovery at 23.6% and 32.26%. Its relatively higher sweep efficiency indicated a uniform CO2 distribution at the end of the cyclic injection, which further led to the highest incremental recovery of 4.94% in the following miscible injection. Comparable CO2 storage capacities were observed in the three fractured core samples (12.21%, 12.98%, and 9.71%, respectively) after completing the miscible displacements. In general, cyclic CO2 injection is recommended as an effective CO2 EOR and geo-storage in tight fractured rocks.

The Effectiveness of the Introduction of the Water-Alternated-Gas Injection on the example of a Carbonate Field in Kazakhstan

Background: Water-Alternated-Gas Injection (hereinafter referred to as WAG) is considered to be a suitable analogue of gas injection and waterflooding, which increase the efficiency of displacement. With continuous gas injection, the displacement front is unstable due to the low viscosity of the gas, which leads to the formation of gas tongues due to a significant difference in the mobility of gas and oil. Alternate injection of water and gas is considered a suitable option in eliminating this problem and in stabilizing the displacement front.
 Aim: The purpose of this work was to generalize the main factors affecting the efficiency of the process, based on the world experience in applying the WAG technology. The effectiveness of this technology application in a carbonate field was also considered.
 Materials and methods: This article analyzes the efficiency of oil displacement using the WAG method in a carbonate field in Kazakhstan. In order to study the proposed oil production technology, the alternate injection of water and gas into the reservoir was simulated on the ECLIPSE 100 simulator. First of all, the process of optimizing the parameters was carried out based on two injection wells. As a result, it was found that for the studied field, the duration of water and gas cycles of 3 months and the sequence of "gas water" are the optimal conditions for observing the greatest effect from WAG. Further, based on the selected parameters, WAG was scaled to the entire field, for the implementation of which several options were developed with 3, 5, 6 and 12 injection wells.
 Results: As a result of the research, the optimal oil displacement option was selected, which involves 5 injection wells with high injectivity and a large volume of injected gas.
 Conclusion: Due to the hydrophilicity of the reservoir, the effect of alternating WAG turned out to be not as significant as it could be expected, due to the effect of hysteresis of relative phase permeabilities, which can be a topic for future research.

Effect of N2/CO2 injection and alternate injection on volume swelling/shrinkage strain of coal

Effect of N2/CO2 injection and alternate injection on volume swelling/shrinkage strain of coal

Optimal Energy Flow in Integrated Electricity and Gas Systems With Injection of Alternative Gas

This paper proposes an optimal energy flow technique for the integrated electricity and gas systems (IEGS) with injections of alternative gases. Firstly, we develop a novel optimal energy flow model of IEGS with alternative gases, where the physical characteristics (e.g., specific gravity) of the gas mixtures are modeled as variables to reflect the impacts of alternative gas injections more accurately. Security indices are introduced to restrain the gas composition variation. Then, convex optimization techniques are tailored to transfer the original highly nonlinear and nonconvex optimization problem into a tractable form. An advanced sequential programming procedure is proposed with self-adaptive convergence criteria to better balance the feasibility and convergency. Finally, the IEEE 24-bus RTS and Belgium gas transmission system, and the practical 160-bus Britain gas system are used to validate the proposed techniques. It can be observed from numerical studies that the computation efficiency of the proposed solution methods is 96.44% faster than traditional mixed-integer nonlinear solvers. The injection of alternative gas can cause up to 4.32% variations in the nodal gas pressure. Nonetheless, under various uncertainties from renewable generation, load level, etc., the proposed optimal energy flow model can maintain the security of IEGS.

Study on Enhanced Oil Recovery Mechanism of CO2 Miscible Flooding in Heterogeneous Reservoirs under Different Injection Methods.

The mechanism by which oil recovery can be enhanced by different injection methods of CO2 miscible flooding to alleviate the influence of heterogeneous reservoirs was studied to optimize the injection methods, further improving oil recovery. According to the reservoir heterogeneity characteristics of the TI oil formation group in Lunnan Oilfield, a 1 m double-layer long core was designed and prepared for four CO2 miscible displacement experiments with different injection methods. By analyzing the variation in the injection-production parameters, the displacement effects of different injection methods were compared, and the mechanism of enhanced oil recovery (EOR) was summarized. The results indicate the following. ① The displacement efficiency of the different injection methods lies in the following order. Alternate CO2-water injection, continuous CO2 flooding, cyclic CO2 flooding, and alternate CO2-hydrocarbon gas injection. ② The recovery of crude oil via CO2 miscible flooding in heterogeneous reservoirs relies on both convective diffusion and miscible mass transfer. Convective diffusion depends mainly on control of the displacement pressure differential and the plugging of preferential seepage channels in high-permeability areas, while miscible mass transfer depends mainly on the swept range of the convective diffusion and the degree of miscibility between CO2 and crude oil. ③ To improve the recovery efficiency of CO2 miscible flooding in heterogeneous reservoirs, it is necessary to choose an injection method that optimizes these two aspects.

Determination of boron concentrations at trace level in graphite matrices by AMS

In order to be classified as possible nuclear grade graphite, it is necessary to establish the boron equivalent content in it. The literature offers various but complicated methods for determining the concentration of boron in graphite at the ppm level.In the past, we have developed a preliminary method to measure the trace level of boron in graphite by AMS using a small quantity of material (of the order of mg) without chemical processing. To perform such more accurate measurements, in this study we have developed the preliminary method, by the alternative injection of the isotopes 11B and 12C in the accelerator in an automatic mode.

MAAP 4.07 Analysis of Long Term Containment Heat Removal After Reactor Vessel Failure (DEC-B) for Nuclear Power Plant Krško (NEK)

The paper presents the MAAP 4.07 analysis of containment heat removal after reactor vessel failure resulting from the initial Station Blackout (SBO) accident. The accident is analysed considering mitigation measures for heat removal from the containment using alternative equipment (Alternative Residual Heat Removal (ARHR) pump and heat exchanger (ARHX) and, also, Alternative Safety Injection (ASI) pump). The mitigation actions are taken according to NEK Severe Accident Mitigation Guidelines (SAMG). There are several possibilities to remove the heat from the containment once the reactor vessel fails and, for all of them, the necessary condition is to have the sufficient source of water (Residual Water Storage Tank (RWST), Alternative Boron Water Tank (ABWT) or other) and the appropriate heat exchanger available. Two options are presented within this paper: 1. Injection to the Reactor Coolant System (RCS) using ASI pump and recirculation (sump to RCS) through ARHR system via ARHX, 2. Spraying the containment through Containment Spray (CI) system using ARHR pump and, then, recirculation (sump to spray) through CI and ARHR systems via ARHX. The results show that the containment heat removal can be done with either of analysed ways if the water is provided for recirculation (assumed containment level 3.9 m ~ 760 m3). However, with the fact that the reactor cavity is not flooded, the cooling using ASI will initially result in considerable containment pressure increase because the water is spilled through the RCS over the hot molten core debris. Therefore, it must be stated that the preferable way of containment pressure reduction, once the vessel has failed, is by using the containment spray. On the other hand, if RWST is not available, then the initial water delivery cannot be made from ABWT via CI system because this option does not exist. It shall also be pointed out that, if the active containment heat removal is started early enough, the Passive Containment Filtered Vent System (PCFVS) opening would be prevented and no fission products shall be released to environment.

Experimental study of fracture conductivity in dolomite reservoirs treated with different acid fracturing technologies

The acid fracturing stimulation mechanism of dolomite reservoirs is entirely different from that of limestone. Most existing research on dolomite acid fracturing still uses the research method of limestone. There is no unified understanding of dolomite reservoirs' acid rock reaction mechanism and stimulation mechanism. The rock outcrops of the Dengying Formation of the Sinian system in the Sichuan Basin, China, with the size of about 17.8 cm × 3.8 cm × 2.5 cm, were used to test the acid-etching morphology, corrosion volume, reaction kinetic parameters, and conductivity under different acid types, injection modes, displacements, and alternating stages with the acid corrosion experiment. The materials used in the experiment are gelling acid, crosslinking acid, and diverting acid, the dolomite content of the rock sample is about 93.79%. The experimental results show that the diverting acid had a lower viscosity and higher mass transfer rate than gelling acid, so it could form a more effective etching, the dissolution volumes in the two acids were 22.15 and 23.38 cm3, respectively. Compared with the injection mode of a single acid fluid, the alternative injection of two fluids with different viscosities can improve the nonuniform etching effect and conductivity, under the “fracturing fluid + acid fluid” alternate injection mode, the dissolution volume of rock was approximately 17.16 cm3, under the “crosslinking acid + diverting acid” alternate injection mode, the dissolution volume of rock was approximately 20.83 cm3. The reaction rate of dolomite is low, and it may be dissolved along the joint and natural fractures. The research results can provide a reference for optimizing the dolomite reservoir's stimulation technology and injection parameter design.

Synergistic study of xanthan-gum based nano-composite on PELS anionic surfactant performance, and mechanism in porous media: Microfluidic & carbonate system

Rising global energy demand and decrease in world fossil fuels reserves draw attention toward production from trapped oil in the reservoirs. CEOR methods are proved and efficient methods which can be applied for increased oil recovery. In this research, the EOR potential of a novel nanocomposite and a developed surfactant was evaluated in the presence of various ions and the production enhancement mechanisms were studied using glass micromodel. Primary, the synergistic effect of the nanocomposite and the natural surfactant on Interfacial tension (IFT) reduction and wettability alteration was studied. After quantitative analysis and investigation of the various mechanisms, it was understood that the presence of the nanocomposite in the surfactant solution alters the wettability of an oil-wet carbonate surface to a water-wet one. Adding nano-composite to surfactant solution can improve the wettability alteration ability of the surfactant up to 60.02%. The adsorption tests revealed that combining the nanocomposite with surfactant solution can reduce surfactant adsorption by 18.99 %. The Zeta potential test was utilized to evaluate the stability of the solution. The zeta potential of the nano/surfactant solution was equal to −28 which illustrated a stable solution. In addition, the zeta potential measurements demonstrated the wettability alteration mechanism. After investigating the properties of the nano-surfactant solutions in the presence of different ions, optimum concentrations were determined and the mechanisms of the nano-chemical EOR method were visually investigated by injecting the desired solutions into the glass micromodel. Eventually, five different injection scenarios were designed for the core flood tests to evaluate the performance of each solution in the porous medium. The achieved final recovery for PELS, PELS/NaCl, and PELS/NaCl/NC solutions were 48.05%, 55.62%, and 60.38%, respectively and the Alternative injection scenario was the best injection plan.

Study on Steam and Microemulsion Alternate Injection for Enhanced Productivity in Heavy Oil Fields

Study on Steam and Microemulsion Alternate Injection for Enhanced Productivity in Heavy Oil Fields

Alternative Current Injection Newton and Fast Decoupled Power Flow

This article presents an alternative Newton-Raphson power flow method version. This method has been developed based on current injection equations formulated in polar coordinates. Likewise, the fast decoupled power flow, elaborated using current injection (BX version), is presented. These methods are tested considering electrical power systems composed of 57-, 118-, and 300-bus, as well as a realistic system of 787-bus. For the robustness analysis, simulations were performed considering different loading conditions and R/X ratios of the transmission line. Based on the simulations that were realized, there is evidence that the performance of the proposed current injection methods is similar to the power injection methods.

Turbulence Effect on Transpiration Cooling Effectiveness Over a Flat Plate in Hypersonic Flow and Sensitivity to Injection Parameters

This work presents a numerical study of coolant porous injection in hypersonic turbulent boundary layer, with an analysis of blowing ratio and pore diameter effects on the cooling performance. Direct numerical simulations (DNS) are carried out for a Mach 5 flow over a flat plate with induced transition, and with a porous injection model to mimic injection from a bed of equally-spaced circular pores. The cooling performance in turbulent flow is compared to laminar 2D flow cases. Results show downstream development of a turbulent wedge-shaped structure, where a dramatic decay of the near-wall coolant concentration is observed. Blowing ratio and pore size are seen to affect the calmed and transitional regions, however they have a marginal or negligible effect within the turbulent region. A cooling effectiveness deficit/reduction of 15% to 30% for the turbulent cases, with respect to the laminar 2D cases, is observed above the injection region due to the 3D flow effects associated with the porous injection, whereas it reaches values as high as 80% in the developed turbulent region due to the turbulent convective effects. The present results shed light on the effects of turbulence on porous wall cooling and clearly indicate that alternative (ad-hoc) injection strategies and parameter calibration are needed to guarantee appropriate wall cooling in a turbulent flow.

Effect of sinusoidal injection velocity on miscible viscous fingering of a finite sample: Nonlinear simulation

The effect of a sinusoidal injection on the fingering instability in a miscible displacement in the application of liquid chromatography, pollutant contamination in aquifers, etc., is investigated. The injection velocity, U(t) is characterized by its amplitude of Γ and time-period of T. The solute transport, flow in porous media, and mass conservation in a two-dimensional porous media is modeled by the convection-diffusion equation, Darcy's equation, and the continuity equation, respectively. The numerical simulation is performed in COMSOL Multiphysics utilizing a finite-element based approach. The fingering dynamics for various time-period have been studied for two scenarios namely, injection-extraction (Γ>1) and extraction-injection (Γ<−1). The onset of fingers and vigorous mixing is observed for Γ>1, whereas for Γ<−1, the onset gets delayed. The viscosity contrast between the sample and the surrounding fluid is characterized by the log-mobility ratio R. When R>0 the rare interface becomes unstable, while for R<0 the frontal interface deformed. In the case of R<0, the extraction-injection process attenuates the fingering dynamics, which is beneficial in chromatographic separations or pollutant dispersion in underground aquifers. The injection-extraction process is observed to have a longer mixing length, indicating early interaction between both interfaces. The degree of mixing χ(t) is more pronounced for injection-extraction scenario and least for extraction-injection R<0,Γ=−2. The average convective forces are more dominant for Γ>1,R=2 till the deformed rare interface interact with diffusive frontal interface. The average diffusive forces are significant for Γ<−1,R=−2 which can be helpful in separation of chemicals in chromatography. This study therefore provided new insights into the role of alternate injection-extraction injections in altering the fingering dynamics of the miscible sample.

Experimental study on sand production of depleted oil and gas reservoirs

With the increasing demand for natural gas, the emergency peak shaving capacity of gas storage is facing great challenges. The operation of gas storage converted from depleted oil and gas reservoir has the characteristics of strong injection and production, and alternate injection and production. However, the sand production of the reservoir makes the major gas storages face the dilemma that the injection and production capacity cannot be enhanced. In this study, the impact factors of sand production in injection-production wells of gas storage converted from depleted oil and gas reservoir were analyzed, and the sand production simulation device of gas storage was developed. Aiming at the two main controlling factors of alternating load and flow, the experimental study of quantitative sand production was conducted. The experimental results show that the alternating load has a significant weakening effect on the reservoir, and the sand production is positively correlated with the number, size and span of the alternating load exerted on the reservoir. By the method of multiple regression analysis, the parameters affecting the sand production degree of the core were obtained as follows: the upper and lower limit pressure of the alternating load, the flow rate and the number of alternating loads. The sand production map was obtained by combining the sand production amount of the core and the upper limit pressure of the alternating load to evaluate the sand production degree of the injection-production wells. In addition, at the same flow rate, the ratio of sand yield of two alternating loads stages is approximately equal to the constant, which provides a reference for the prediction of sand production in gas storage. The indoor simulation experiment of sand production in gas storage provides technical ideas and theoretical basis for the reconstruction of gas storage in Nanpu 1–29 block, and guides the selection of sand control completion methods in gas storage.

Pattern rupture and channeling effect by alternating radial displacement

Effect of alternative injection to immiscible fingering instability in a Hele-Shaw cell (or porous media) is studied experimentally and numerically. The injection alternation of less/more viscous fluid results in fluid layer of fingering/circular interface, respectively. Correspondingly to the interrupted supply of less viscous fluid and continuous expansion by the following circular interface, the fingering layer is ruptured to form a unique pattern of separated fluid islands. In addition, the pattern of the most inner fingering layer of each alternation emerges with great similarity. The repeatability of these newly emerging patterns indicates preferred flow paths of injected less viscous fluid, referred to as channeling effect. The features of pattern rupture and channeling effect caused by injection alternation result in inconsistent influence to the interfacial length, which is important to many applications such as reaction and dissolution. The interfacial length increases significantly by injection alternation in the cases of less unstable conditions because of additional fluid-fluid interfaces. Nevertheless, the azimuthally ruptured fluid islands and active finger coalescences along the radial channels reduce the interfacial length. For cases of extremely vigorous fingering (higher viscosity contrast or larger injection rate) associated with frequent alternation, the overall interfacial length is reduced even with more additional fluid-fluid interfaces. All the above qualitative and quantitative observations in experiments are numerically verified by simulations.