Multilayer Gas Research Articles

Transpiration and plant hydraulics of Abies veitchii under fluctuating environmental conditions in cool montane forest

AbstractIn subalpine fir wave forests, strips of dead and weakened trees occur perpendicular to the slope next to strips of healthy trees. To reveal the transpiration by weakened Abies veitchii trees exposed to increased atmospheric evaporative demand, we investigated the ecophysiological traits closely related to the growth and transpiration, comparing them with those of the healthy trees and saplings in the fir wave of Mt. Shimagare in central Japan. The transpiration rate (E) was investigated using sap flux sensors to measure heat pulse velocity and compared with the surrogate for the needle water demand, which was computed using a multilayered gas and energy transfer model (modeled E, Emod). Weakened trees exhibited smaller diameter growth and narrower sapwood than healthy trees, as well as lower heat pulse velocity compared with healthy saplings. However, needle‐level traits did not differ significantly between weakened and healthy trees. Needle water potential at midday was as negative as the needle turgor loss point, and the measured heat pulse velocity increased linearly with Emod but leveled off above a certain Emod value in weakened trees and healthy saplings, suggesting that trees restricted E to balance the needle water budget. Heat pulse velocity of weakened trees leveled off at Emod lower than that of healthy saplings, probably due to lower capacity for water supply to the needles. Restriction of E would occur less frequently but be necessary for both weakened and healthy A. veitchii on Mt. Shimagare to avoid hydraulic failure, sacrificing photosynthetic carbon assimilation.

Efficient development technology of Upper Paleozoic Lower Shihezi tight sandstone gas reservoir in northeastern Ordos Basin

Abstract The Lower Shihezi Formation of the Upper Paleozoic at the northeastern margin of the Ordos Basin develops widely distributed thick massive and multilayer gas reservoirs. How to formulate an effective development policy is a difficult and hot spot. In this article, reservoir characteristics and production capacity influencing factors of the tight gas sandstone in Lower Shihezi Formation in this area are systematically studied, and optimization schemes of development measures for massive and multilayer gas reservoirs are proposed. The results show that the petrophysical characteristics of the small pore–mesopore type gas reservoir in the target layer are the best, with the average porosity, permeability, and coordination number of 7.6%, 0.74 mD, and 3.3, respectively. Thick sand body, high structural position, good petrophysical properties, and high drilling rate of sandstone are all conducive to drilling high production gas wells. Development policies for massive and multilayer gas reservoirs have been formulated: (1) the preferred well type for massive gas reservoir is vertical well + horizontal well, while the preferred well type for multilayer gas reservoir is horizontal well + stepped horizontal well; (2) the reasonable horizontal segment length of massive gas reservoir is 1,000 m, and the reasonable horizontal segment length of multilayer gas reservoir is 1,250 m; (3) similar to massive and multilayer gas reservoirs, the more the fracture stages, the higher the cumulative gas production, and the optimal fracture stage number of both gas reservoirs is 8; (4) the optimal fracture half-length and the angle between the fracture and the horizontal section are 140 m and 90°, respectively; and (5) the reasonable well spacing of vertical wells is 600 m and that of horizontal wells is 750 m. The development policy proposed in this study is suitable for the efficient development of complex tight sandstone gas reservoirs in similar areas.

A Coupling Model of Gas–Water Two-Phase Productivity for Multilateral Horizontal Wells in a Multilayer Gas Reservoir

A series of complex horizontal wells have been implemented in challenging gas reservoirs. Multilateral horizontal well technology can be used in multilayer gas reservoirs, facilitating the expansion of the gas drainage area and enhancing productivity. Accurate productivity calculations for multilateral wells in multilayer reservoirs are essential for effective reservoir development. However, there have been few studies in this area. This paper introduces a coupling model for calculating the gas–water two-phase productivity of multilateral wells in multilayer reservoirs, based on the principles of conformal transformation and superposition of potential functions. The accuracy of the model is validated by obtaining the distribution of flow along the horizontal wellbore through numerical simulation cases. The results from the field case and sensitivity analysis indicate that the pressure difference increases nonlinearly from the toe to the heel, and the productivity of multilateral wells decreases as the gas–water ratio increases. The method proposed in this paper is applicable for calculating the productivity of multilateral wells in multilayer reservoirs.

E-peroxone with a novel GDE decorated with hydrophobic membrane for the degradation of pyridine: Stability, byproducts and toxicity

E-peroxone process is an emerging electrochemical oxidation process, based on ozone and the in-situ cathodic generation of H2O2, but the stability of cathode is one of the key restraining factors. In this study, we designed a multilayer gas diffusion electrode (GDE) decorated with a commercial hydrophobic membrane for the degradation of pyridine. It was found that a proper control of membrane pore sizes and hot-pressing temperature can significantly promote the GDE stability. Subsequently, key operational parameters of the constructed E-peroxone system were investigated, including the ozone concentration, current density, pH value, electrolyte type and initial concentration of pyridine. The degradation pathways were proposed according to six identified transformation products. The toxicity variation along the degradation progress was evaluated with microbial respiration tests and Toxicity Estimation Software Tool (T.E.S.T.) calculation and an efficient detoxification capacity of E-peroxone was observed. This research provides a theoretical basis and technical support for the development of highly efficient and stable E-peroxone system for the elimination of toxic organic contaminants.

Theoretical and experimental research on static stiffness, performance, and lift-off characteristics of multi-layer gas foil thrust bearings

In this study, a new comprehensive fully coupled elastic-hydrodynamic model is developed for a multi-layer gas foil thrust bearing (GFTB). The interaction effects among the top foil, back board, middle foil, and bottom foil, as well as the Coulomb friction effect, are considered. The stiffness and static characteristics obtained by the experimental and theoretical approaches are in good agreement, which verifies the accuracy of the model. The contribution of each foil layer to the overall stiffness and the load-carrying mechanism are analyzed. Interaction effects of the load, preload, and rotational speed on the static performance are investigated comprehensively. Furthermore, start-stop tests are performed to achieve the lift-off speed, start-up torque, and shut-down torque under various operating conditions.

Vertical gradient of needle ozone uptake within the canopy of Cryptomeria japonica

Leaf ozone uptake through the stomata is an important index for the ozone risk assessments on trees. Stomatal conductance (gs) and ozone concentration ([O3]), determinants of the leaf ozone uptake, are known to show vertical gradients within a tree canopy. However, less is known about the within-canopy vertical gradient of leaf ozone uptake. This study was aimed to elucidate how the vertical gradient of [O3] and gs affect needle ozone uptake within a canopy of mature Cryptomeria japonica trees in a suburban forest at Tokyo, Japan. For this purpose, a multilayer gas exchange model was applied to estimate the vertical gradient of needle gs and the accumulated ozone uptake during the study period (POD1, Phytotoxic Ozone Dose above a threshold of 1 nmol m−2 s−1). In addition, we also tested several scenarios of vertical gradient of [O3] within the canopy for sensitivity analysis. The POD1 was declined from the top to the bottom of the canopy. This tendency strongly depended on the vertical gradient of gs and was hardly affected by the changes in simulated vertical reductions of the [O3]. We further assessed the photosynthesis of sunlit needles (needles absorbing both direct and diffuse light) and shaded needles (needles only absorbing diffuse light). The photosynthesis of shaded needles in the upper half of the canopy made a great contribution to the entire canopy photosynthesis. In addition, given that their POD1 was lower than that of sunlit needles, ozone may affect sunlit and shaded needles differently. We concluded that these considerations should be incorporated into modeling of the calculation of ozone uptake for mature trees to make accurate predictions of the ozone effects on trees at the canopy scale.

Well Location Evaluation of Depressurized Production from the Multilayer Gas Hydrate Reservoir

Well Location Evaluation of Depressurized Production from the Multilayer Gas Hydrate Reservoir

Fine-tuned combination of cell and electrode designs unlocks month-long stable low temperature Cu-based CO2 electrolysis

The urgency of achieving green chemical production through Cu-based CO2 electroreduction necessitates a rapid transition towards technical maturity and commercialization in the pursuit of addressing the global imperative of decarbonization. Surprisingly, limited emphasis has been placed on exploration of readily scalable cell and electrode designs, which are pivotal in ushering in the era of stable and selective CO2 electrolyzers, showcasing the innovative potential within this area. Herein, we report a breakthrough in achieving month-long stability in the production of C2H4, representing an unprecedented milestone in low-temperature CO2 to C2+ electrolysis. Initial investigations involved the evaluation of five distinct cell architectures for Cu-based CO2 electrolyzers, guided by considerations of cell potentials, scalability with current technology, and CO2 crossover. An innovative multilayer Gas Diffusion Electrode (GDE), featuring an anion exchange ionomer and metal oxide layer, is introduced for CEM-based zero-gap cells, enabling C2H4 formation despite acidic surroundings. However, selectivity towards C2H4 proved suboptimal for extended stability testing. Conversely, the tailored multilayer GDE for one-gap cell architecture achieves a commendable 54 % faradaic efficiency (FE) towards C2+ products at 300 mA/cm2. Remarkably, chronopotentiometric tests demonstrate 720 h of stability (FEC2H4 > 20 %) at 100 mA/cm2. At higher current densities (300 mA/cm2), stability is reduced to 75 h, with detailed analyses revealing distinct degradation mechanisms. At 100 mA/cm2, salt formation predominates, while at 300 mA/cm2, catalyst layer restructuring degrades catalytic activity towards C2H4. Our research underscores the potential for stable, high C2+ selectivity through innovative electrode design and scalable cell architectures, advancing sustainable CO2 utilization.

The Production Splitting Method of Offshore Multilayer Combined Water Flooding Gas Wells with Gas Dissolving.

Offshore gas reservoirs are characterized by thin interlayers, high production, few wells, etc., and are often exploited by multilayer combined mining, whereas the production dynamics of multilayer gas reservoirs are very different from those of single-layer gas reservoirs. Therefore, clarifying the gas production contribution of each layer in multilayer combined gas reservoirs is an important prerequisite for analyzing the potential of gas reservoirs and realizing efficient development. In this paper, unlike the past method of evaluating the gas production contribution of each layer by using the KH attribute of the reservoir, we combined the modified B-L equation considering CO2 dissolution and the multilayer multizone seepage equation to establish a dynamic split model of the production dynamics of multilayer water-driven gas reservoirs, verified the reliability of the model through the numerical model and the results of the production well logging, quantitatively analyzed the degree of influence of each parameter on the contribution of the layered gas production, and designed the orthogonal experiments. The main controlling factors of the gas production contribution of each layer were determined. The results of the study show that (1) the main controlling factors for the gas production contribution of each layer in the early stage of WDG are, in order, permeability, thickness, outer boundary distance, porosity, CO2 content, and total gas production rate; however, the main controlling factors for the gas production contribution of each layer in the late stage of WDG are, in order, thickness, permeability, outer boundary distance, porosity, CO2 content, and total gas production rate; and the combined view shows that the permeability and thickness have the greatest influence. (2) In multilayer production, the conditions of high permeability, close gas-water boundary, poor gas content, and low CO2 content will reduce the gas production contribution of the layer with the increase of production time. (3) Compared with the results of production logging and numerical simulation, the split model can better predict the gas production of each layer, and the prediction error is no more than 10%. (4) By comparing with the numerical simulation results, the model can realize the prediction of the time of seeing water in the layer with stronger water body capability. (5) The model takes into account the effect of the CO2 content, better reflects the actual gas composition of each layer, and can improve the production prediction accuracy by up to 4%. Considering the high cost of production logging in offshore oil and gas fields, the inability of the KH method to reflect the dynamic changes of gas production in each layer, the poor application of stratified sampling to dry gas reservoirs, and other limitations, the model in this paper can be utilized to simulate the multilayer water-driven gas drive process when the energy of the water body is strong by using the geological parameters of the reservoir and the fluid parameters, and the simulation results of this model provide directions for offshore multilayer water-driven gas reservoirs to improve the recovery rate, and for plugging and regulating the water and exploiting the potential of gas wells that have seen water.

Numerical Evaluation of Commingled Production Potential of Marine Multilayered Gas Hydrate Reservoirs Using Fractured Horizontal Wells and Thermal Fluid Injection

Multilayered reservoirs with coexisting free gas and hydrates are primary targets for commercialization, nevertheless, the extremely low permeability greatly limits their extraction efficiency. Herein, multilayer commingled production using horizontal wells stimulated by hydraulic fracturing and thermal fluid injection was proposed to enhance productivity, and the effects of key factors on co-production performance were numerically examined, with the reservoir located in the Shenhu Area as the geological background. The results indicated that due to severe interlayer contradictions, the stimulation capabilities of using fracturing or thermal fluid injection alone were limited, in particular, the extraction of hydrates severely lagged behind. However, their combination exhibited tantalizing productivity due to strengthened inter-well interaction. Reducing the fracture spacing was more effective than increasing fracture conductivity in shortening the production cycle, and intensive fractures with adequate flow capacity were suggested for gas enhancement and water control. When the fracture spacing was reduced from 30 to 5 m and the fracture conductivity increased from 10 to 100 D·cm, the horizontal section length for commercial production (average daily gas production of 50,000 m3 and recovery ratio of 0.7) was reduced from 1758 to 146 m, which is lower than the on-site horizontal section length of 250–300 m. Therefore, the proposed development mode is promising for the commingled production of gas and hydrates.

Probing dimensional consistency during multi-track multi-layer gas metal arc directed energy deposition of aluminium alloys

Probing dimensional consistency during multi-track multi-layer gas metal arc directed energy deposition of aluminium alloys

Inter-layer interference for multi-layered tight gas reservoir in the absence and presence of movable water

Due to the dissimilarity among different producing layers, the influences of inter-layer interference on the production performance of a multi-layer gas reservoir are possible. However, systematic studies of inter-layer interference for tight gas reservoirs are really limited, especially for those reservoirs in the presence of water. In this work, five types of possible inter-layer interferences, including both absence and presence of water, are identified for commingled production of tight gas reservoirs. Subsequently, a series of reservoir-scale and pore-scale numerical simulations are conducted to quantify the degree of influence of each type of interference. Consistent field evidence from the Yan'an tight gas reservoir (Ordos Basin, China) is found to support the simulation results. Additionally, suggestions are proposed to mitigate the potential inter-layer interferences. The results indicate that, in the absence of water, commingled production is favorable in two situations: when there is a difference in physical properties and when there is a difference in the pressure system of each layer. For reservoirs with a multi-pressure system, the backflow phenomenon, which significantly influences the production performance, only occurs under extreme conditions (such as very low production rates or well shut-in periods). When water is introduced into the multi-layer system, inter-layer interference becomes nearly inevitable. Perforating both the gas-rich layer and water-rich layer for commingled production is not desirable, as it can trigger water invasion from the water-rich layer into the gas-rich layer. The gas-rich layer might also be interfered with by water from the neighboring unperforated water-rich layer, where the water might break the barrier (eg weak joint surface, cement in fractures) between the two layers and migrate into the gas-rich layer. Additionally, the gas-rich layer could possibly be interfered with by water that accumulates at the bottom of the wellbore due to gravitational differentiation during shut-in operations.

Prediction of pressure and temperature profiles for two-phase flow in multilayered gas wells by DTS data

Downhole temperature and pressure data are crucial information to help us understand the fluid flow dynamics in the reservoir. With the advancement of downhole monitoring technology, high-precision and high-resolution monitoring instruments facilitate qualitative and quantitative utilization of transient downhole temperature and pressure data in monitoring applications. The distributed temperature sensors (DTSs) overcome the limitations of traditional monitoring techniques and achieve real-time temperature monitoring in complex downhole conditions. However, the physical phenomena and response mechanisms hidden in the temperature data obtained by (DTSs) in transient, multilayered combined production and two-phase gas wells have not been thoroughly studied yet.Gas-water two-phase fluid flow in the reservoir is the prime consideration of this study. In this paper, based on the principles of mass, energy conservation, Darcy's law, and the second laws of thermodynamics, a forward model is established to predict pressure and temperature distribution in a multilayered vertical gas well system by coupling the flow model and thermal model. The model considers the changes of fluid high-pressure properties and microheat effects such as the Joule-Thomson effect, viscous friction to reach the desired solution. Subsequently, the model is solved numerically and used for sensitivity analysis of parameters influencing temperature and pressure distribution, such as gas production rates, permeability, Joule-Thomson coefficient. At last, the model is applied to a multilayer combined production well. The results of the example show the pressure, temperature and production profile can be predicted precisely.

Unveiling the non-equilibrium process in multilayer mixture adsorption

The Brunauer–Emmett–Teller (BET) theory [S. Brunauer et al., “Adsorption of gases in multimolecular layers,” J. Am. Chem. Soc. 60, 309–319 (1938)] constitutes a cornerstone in gas-adsorption physics. Recently, the kinetic BET equation of single-kind adsorbate has been proposed [H. Yu and X. Zhang, “Molecular-kinetic study of multilayers gas-adsorption in a rarefied gas environment,” Phys. Fluids 34, 123106 (2022)], while its counterpart of mixed adsorbates is currently unknown. Gas mixtures are commonly found in both natural and artificial systems. To address this limitation, we have proposed a kinetic BET theory for adsorbate mixtures in this paper. Moreover, we gave an analytical solution addressing low gas pressure conditions. In this condition, we predicted the “over-adsorption” of one species in the mixture with a higher desorption rate over time, and the “inertia effect” during the crowed-out process of the fast-desorbing species. Further, we also simulated the reciprocal influence of multilayer gas adsorption on the non-equilibrium fluids. Our findings provide valuable insights into gas-adsorption experiments and can facilitate technological advancements.

Simulation study of hydrogen sulfide removal in underground gas storage converted from the multilayered sour gas field

A simulation study was carried out to investigate the temporal evolution of H2S in the Huangcaoxia underground gas storage (UGS), which is converted from a depleted sulfur-containing gas field. Based on the rock and fluid properties of the Huangcaoxia gas field, a multilayered model was built. The upper layer Jia-2 contains a high concentration of H2S (27.2 g/m3), and the lower layer Jia-1 contains a low concentration of H2S (14.0 mg/m3). There is also a low-permeability interlayer between Jia-1 and Jia-2. The multi-component fluid characterizations for Jia-1 and Jia-2 were implemented separately using the Peng-Robinson equation of state in order to perform the compositional simulation. The H2S concentration gradually increased in a single cycle and peaked at the end of the production season. The peak H2S concentration in each cycle showed a decreasing trend when the recovery factor (RF) of the gas field was lower than 70%. When the RF was above 70%, the peak H2S concentration increased first and then decreased. A higher reservoir RF, a higher maximum working pressure, and a higher working gas ratio will lead to a higher H2S removal efficiency. Similar to developing multi-layered petroleum fields, the operation of multilayered gas storage can also be divided into multi-layer commingled operation and independent operation for different layers. When the two layers are combined to build the storage, the sweet gas produced from Jia-1 can spontaneously mix with the sour gas produced from Jia-2 within the wellbore, which can significantly reduce the overall H2S concentration in the wellstream. When the working gas volume is set constant, the allocation ratio between the two layers has little effect on the H2S removal. After nine cycles, the produced gas’s H2S concentration can be lowered to 20 mg/m3. Our study recommends combining the Jia-2 and Jia-1 layers to build the Huangcaoxia underground gas storage. This plan can quickly reduce the H2S concentration of the produced gas to 20 mg/m3, thus meeting the gas export standards as well as the HSE (Health, Safety, and Environment) requirements in the field. This study helps the engineers understand the H2S removal for sulfur-containing UGS as well as provides technical guidelines for converting other multilayered sour gas fields into underground storage sites.

Optimal design of top-foil wedge shape for a specific multi-layer gas foil thrust bearing by considering aerodynamic and thermal performances

Optimal design of top-foil wedge shape for a specific multi-layer gas foil thrust bearing by considering aerodynamic and thermal performances

An Analytical Model Coupled with Orthogonal Experimental Design Is Used to Analyze the Main Controlling Factors of Multi-Layer Commingled Gas Reservoirs

The majority of China’s multi-layer low permeability tight gas reservoirs are currently being extracted through the method of multi-layer co-production. However, due to the significant disparity in physical properties and varying degrees of pressure depletion among the production layers, elucidating the primary factors influencing the productivity contribution of each gas layer remains challenging. A multi-factor analytical model is proposed for commingled gas wells with multiple layers. An unstable model is established for the production of commingled layers, and the problem of flow distribution is addressed using the Duhamel convolution principle. The Laplace transform is subsequently employed to derive the solution in the Laplace domain, which can be inverted utilizing the Stehfest inversion algorithm to obtain a real-time domain solution. The influence of reservoir factors on the stratification contribution rate has been comprehensively analyzed, encompassing permeability, porosity, initial pressure, drainage radius, and layer thickness. The orthogonal test design was employed to conduct range analysis and variance analysis separately, yielding the primary and secondary order as well as influence weight of the five factors. The findings demonstrate that, within this gas reservoir, the discharge radius, thickness, and porosity are identified as the primary factors influencing gas well productivity. Furthermore, seven horizontal flow charts illustrating the double-layer gas reservoir and five horizontal flow charts depicting single-factor variations in the double-layer gas reservoir were constructed. These charts provide a clear visualization of the impact of each reservoir factor on stratification’s contribution rate. In contrast to previous studies, this novel approach presents a comprehensive optimization framework that ranks the influence weights of individual factors and identifies the most significant factors impacting multi-layer gas reservoirs. The presented method also serves as a foundation for the subsequent selection of multi-layer gas reservoirs, formulation of gas well stimulation measures, and efficient development.

Thermo-elasto-hydrodynamic analysis of a specific multi-layer gas foil thrust bearing under thermal-fluid–solid coupling

Gas foil bearing faces severe and complex thermal-fluid–solid coupling issues when in ultra-high speed and miniaturized impeller machineries. In this study, a Thermo-Elasto-Hydrodynamic (TEHD) analysis of a specific multi-layer gas foil thrust bearing on the continuous loading process within a steady rotational speed is numerically investigated by a three-dimensional thermal-fluid–solid coupling method. Results indicate that the multi-layer foil exhibits nonlinear overall stiffness, with the thrust bottom foil serving as the primary elastic deformation structure, while the thrust top foil maintains a well-defined aerodynamic shape during a loading process, which helps reduce frictional damage and achieve an adequate loading capacity. For low loads, the fluctuation of the gas film is extremely sensitive, and it weakens dramatically as the load increases. The viscous heating and friction torque exhibit a linear relationship with an increasing bearing load after a rapid growth. Depending on the exact stacking sequence and contact position of the multi-layer gas foil, the overlapping configuration allows for efficient transfer of viscous-shearing heat accumulated at the smallest air film through thermal conduction while providing elastic support. Due to the strong inhomogeneity of the viscous heat under varying loads, the temperature distribution on the top foil surface shows pronounced variations, while the difference between the peak and average temperatures of the thrust plate and top foil surfaces widens substantially with an increasing load.

A comparative study on inflow schemes of radial throughflow cooling for thermal management of a specific multi-layer gas foil thrust bearing

In order to illustrate the effects of radial cooling throughflow on the aerodynamic and thermal behaviors of gas foil thrust bearing, a three-dimensional fluid-solid coupled numerical investigation is conducted for a specific multi-layer gas foil thrust bearing under stable operating conditions in the present study, with two inflow schemes adopted, referred as radially-inward inflow scheme and radially-outward inflow scheme, respectively. The results show that the flow fields and the thermal behavior within the gas foil thrust bearings under the two inflow schemes are significantly different due to the difference in the inflow direction and the effect of centrifugal force caused by the high-speed rotation. The radial cooling throughflow can greatly alleviate the high temperatures in the film layer and improve the cooling capacity, but the increase of mass flow rate causes a non-monotonic change of static bearing load and an enhancement of viscous-shearing heat, as well as a significant rise of the air supply pressure. The radially-inward inflow scheme allows a lower peak temperature and a more uniform temperature distribution on the thrust plate and foil surfaces, while the radially-outward inflow scheme provides a lower area-averaged temperature and consumes less air supply pressure.

Interface characteristics and stability mechanisms of bubbles in high-concentration bentonite slurry

Foam and slurry are important materials for preventing spewing of the earth pressure balance (EPB) shields, but their interaction at the interface level is not entirely understood. Herein, an anionic surfactant was used to foam bentonite slurry with a concentration of 10–30 wt%. The mechanism of the slurry on the foamability of the surfactant and the bubbles stability were analysed through surface viscoelastic modulus, ζ-potential, FT-IR, surface tension, contact angle, and microscopic observation. The results show that the bentonite slurry forms a stable three-dimensional grid structure, which increases the surface tension and free energy required for the formation of the gas–water interface. Surfactants are adsorbed on the bound water layer on the surface of bentonite particles. This increases both the electrostatic repulsion of system and the hydrophobicity of the particle and forms a multi-layered gas–water interface with high viscoelasticity, thus slowing down the drainage, coarsening, and coalescence.