Gas Layer Research Articles

Divergent Richtmyer–Meshkov instability on a heavy gas layer

Experiments on divergent Richtmyer–Meshkov (RM) instability at a heavy gas layer are performed in a specially designed shock tube. A novel soap-film technique is extended to generate gas layers with controllable thicknesses and shapes. An unperturbed gas layer is first examined and its two interfaces are found to move uniformly at the early stage and be decelerated later. A general one-dimensional theory applicable to an arbitrary-thickness layer is established, which gives a good prediction of the layer motion in divergent geometry. Then, six kinds of perturbed SF $_6$ layers with various thicknesses and shapes surrounded by air are examined. At the early stage, the amplitude growths of the inner interface for various-thickness layers collapse quite well and also can be predicted by the Bell model for cylindrical RM instability at a single interface, which indicates a negligible interface coupling effect. Later, a rarefaction wave accelerates the inner interface, causing a dramatic rise in the growth rate. It is found that a thicker gas layer will result in a larger extent that the rarefaction wave can promote the instability growth. A modified Bell model accounting for both Rayleigh–Taylor (RT) instability and interface stretching caused by a rarefaction wave is established, which well reproduces the quick instability growth. At late stages, reverberating waves inside the layer are negligibly weak such that the inner interface growth is dominated by RM instability and RT stability. The major factors driving the outer interface development are a compression wave and interface coupling. A new interface coupling phenomenon existing uniquely in divergent geometry caused by the gradual thinning of the gas layer is observed and also modelled.

Comparative analysis of gas-assisted extrusion of polypropylene sheet based on two types of gas intake

Abstract The formation of a stable gas layer is to have a significant effect on polymer gas-assisted extrusion (GAE). Previously, for vertical extrusion forming, the gap intake method was used, which tends to result in very short stabilization times for the gas layer. In this study, the effect of two gas intake modes was compared based on horizontal sheet extrusion. The results show that stabilization of the gas layer is easily achieved in the vertical gas-assisted die by introducing gas first. However, when using parallel die, the gas distributes the melt uniformly along the surrounding velocity and the gas layer can be stable for a long time. Moreover, disrupting the process sequence also makes it easy to achieve gas layer stability without affecting the tability of the gas layer in the subsequent extrusion. And, during low-speed extrusion, the flow inertia of the polymer melt is used to extend the flow channel of the gas-free–assisted section into the gas-assisted section to overcome the gravity of the polymer melt and smoothly extrude it in the parallel gas-assisted die. The parallel die can be considered for the production of GAE of daily profiles and can be used to improve quality.

Water Invasion Into Multi-Layer and Multi-Pressure Carbonate Reservoir: A Pore-Scale Simulation

AbstractCarbonate reservoirs contribute the highest proportion of natural gas production around the world, and commingled production is frequently used to increase production for the multi-layer reservoirs. However, the complex pore structure including pore, fracture, and cavity, and the presence of edge/bottom water increase the difficulties in evaluating its commingled-production performances. In this work, three comingled patterns of digital rocks are reconstructed based on the computerized tomography scanning images, and the lattice Boltzmann method is used to investigate the commingled production with water invasion. The results show that the fracture and cavity commingled production pattern has the largest interlayer heterogeneity, and the production ratio between the two layers can reach 6.7. Commingled production for the system with different interlayer pressure may lead to backflow phenomenon, which is not only dependent on the initial pressure, but also related to the heterogeneity between the producing layers. Especially, if the interlayer heterogeneity is large and the initial pressure of the low-permeability layer is lower, the backflow volume would be very large. The water invasion during commingled production can influence the flow capacity of the other gas layers even there is no pressure interference. In addition, if the water layer has larger pressure, the produced water will continuously flow back to the gas layer until the pressure of the two layers becomes balanced. The coupled effects of pressure interference and water invasion significantly damage the commingled-production performance. This work can help for better understanding of the gas-water two-phase flow behaviors during commingled production, which provides fundamental support for the scientific development of multi-layer carbonated reservoirs.

Removal of Hot Saturns in Mass–Radius Plane by Runaway Mass Loss

The hot Saturn population exhibits a boundary in mass–radius space, such that no planets are observed at a density less than ∼0.1 g cm−3. Yet, planet interior structure models can readily construct such objects as the natural result of radius inflation. Here, we investigate the role X-ray and extreme UV irradiation (XUV)-driven mass loss plays in sculpting the density boundary by constructing interior structure models that include radius inflation, photoevaporative mass loss, and a simple prescription of Roche lobe overflow. We demonstrate that planets puffier than ∼0.1 g cm−3 experience a runaway mass loss caused by adiabatic radius expansion as the gas layer is stripped away, providing a good explanation of the observed edge in mass–radius space. The process is also visible in the radius–period and mass–period spaces, though smaller, high-bulk-metallicity planets can still survive at short periods, preserving a partial record of the population distribution at formation.

Oscillations of a Channel Wall on a Nonlinear Elastic Suspension Under the Action of a Pulsating Layer of Viscous Gas in the Channel

Oscillations of a Channel Wall on a Nonlinear Elastic Suspension Under the Action of a Pulsating Layer of Viscous Gas in the Channel

Effect of improved atmospheric opacities in modelling sub-Neptunes

Aims. We investigate the impact of updated atmospheric mean opacity input values on modelled transit radius and the distribution of interior layer mass fractions. Methods. We developed and applied a coupled interior-atmosphere model. Our straightforward semi-grey calculation of atmospheric temperature enables us to perform thousands of model realisations in a Monte Carlo approach to address potential degeneracies in interior and atmospheric mass fraction. Our main constraints are planetary mass and radius from which our model infers distributions of the internal structure of exoplanetary classes ranging from Super-Earth to Mini-Neptune. We varied the relative masses of gas, envelope, mantle, and core layers subject to constraints on the bulk density from observations, and investigated the effect of updating atmospheric mean opacities. Results. First, we validate our model output with observed temperature profiles for modern Neptune. We can reproduce the basic features in the middle atmosphere but not the temperature inversion in the upper layers, which is likely because our model lacks aerosol heating. Calculated interiors are generally consistent with modern Neptune. Second, we compare with the well-studied object GJ 1214 b and obtain results that are broadly consistent with previous findings; they suggest correlations between modelled gas, water, and core mass fractions, although these are generally weak. Updating the opacities leads to a change on the order of a few percent in the modelled transit radius. This is comparable in magnitude to the planned accuracy of the PLATO data for planetary radius, suggesting that the opacity update in the model is important to implement.

Native Iron in Siberian Traps

The results of study of intrusive traps with a large-scale occurrence of native iron allowed us to identify general patterns of their composition and origin. Intrusive bodies are weakly differentiated; they feature a similar structure and mineralogical, petrochemical and geochemical composition. Two associations of rock-forming minerals were found in all the studied bodies, i.e. early deep (pre-chamber) and intra-chamber. Native iron forms nodular segregation, with a subordinate amount of cohenite, troilite and magnetite-wustite. Natural reduced iron can concentrate many elements, such as Ni, Co, Au and PGE. Their content in metal increases by hundreds or even thousands of times compared to the hosting silicate part. The formation of native iron is based on the fluid-magmatic interaction between magma substance and reducing components of the fluid, primarily of methane-hydrogen composition. As a result, dispersion of a primarily homogeneous basalt liquid into silicate and metallic components occurs. In the process of transfer, finely dispersed phases of iron form droplet-liquid segregations with a monomolecular layer of gas on their surface that prevents enlargement of metallic droplets. In the hypabyssal chamber, magma degassing occurs, including degassing from metallic spherules. The processes of droplet fusion and formation of native phase segregations begin.

Numerical Study on the Effect of Atmospheric Wind on the Fire Severity in Informal Settlements with Different Dwellings’ Wall Thermal Characteristics

AbstractThere is a persistent risk of large-scale fire conflagrations in informal settlements, which can threaten hundreds of people simultaneously. Although the literature implies that wind conditions have a significant impact on these fires, little is known about how wind conditions affect the dynamics and spread of flames in informal settlements. In order to comprehend the impact of wind conditions (speed and direction) on the time to flashover and fire severity in informal settlement dwellings with different wall thermal characteristics, a numerical study was conducted utilizing the Fire Dynamics Simulator (FDS), a Computational Fluid Dynamics (CFD) code. For six different wind speeds (1 m/s, 5 m/s, 10 m/s, 15 m/s, 20 m/s and 25 m/s) and two wind directions (side and back wind). Simulations were conducted with full-scale informal settlement dwellings burning wood cribs, analyzing the fuel mass loss rate, hot gas temperature, global equivalence ratio, radiative heat flux outside the door, and time to flashover. In addition, the influence of wall thermal properties was examined for thermally-thin steel-clad and asbestos cement-clad dwellings (thermally-thick). Regardless of wind direction, it was noticed that an increase in wind speed significantly shortened the time required to attain flashover. This was shown to be the result of the wind accelerating the burning rate of the wood cribs and, as a result, the faster temperature rise of the hot gas. Radiative heat fluxes observed outside the door increased with the wind speeds. The direction of the wind had a small effect on the investigated fire characteristics, with the side wind scenarios exhibiting somewhat longer timeframes to flashover. Thermally-thin walled informal settlement dwellings exhibited a greater fire severity, with higher fuel mass loss rates, hot gas layer temperatures, and higher external radiant heat fluxes, as well as shorter timeframes to flashover. These findings indicate that both wind speed and thermal wall characteristics have a substantial impact on the severity of fires in informal settlements and can enhance the risk of fire spread.

Numerical simulation of gas hydrate production in shenhu area using depressurization: The effect of reservoir permeability heterogeneity

An accurate description of the reservoir characteristics is essential to the precise prediction of gas production from nature gas hydrate (NGH) deposits. In most numerical studies related to large-scale onshore or offshore NGH production cases, the reservoir permeability was usually assumed to be homogeneous. In this work, a multi-layered heterogeneous-permeability reservoir model (including a hydrate-bearing layer, a three-phase layer, and a free gas layer) was established, and the gas production behavior was analyzed by using the TOUGH + HYDRATE simulator. It is found that hydrate and free gas tend to be scatteredly distributed in this reservoir model. Reservoirs with heterogeneous permeability have better gas production performance than homogeneous ones. The 10-year cumulative gas production from the heterogeneous reservoir with the heterogeneity degree of 0.4μ (622 × 104 m3) is 15.19% higher than that from the homogeneous reservoir (540 × 104 m3). Moreover, the layered production results show that the free gas layer contributes the most to gas production among the three layers. The effect of heterogeneity on gas production in high-permeability reservoirs is more obvious than that in low-permeability reservoirs. Therefore, the permeability heterogeneity of the reservoir, especially the permeability heterogeneity of the free gas layer, should be considered in the long-term prediction of NGH production.

Evaporating Rayleigh–Bénard convection: prediction of interface temperature and global heat transfer modulation

We propose an analytical model to estimate the interface temperature $\varTheta _{\varGamma }$ and the Nusselt number $Nu$ for an evaporating two-layer Rayleigh–Bénard configuration in statistically stationary conditions. The model is based on three assumptions: (i) the Oberbeck–Boussinesq approximation can be applied to the liquid phase, while the gas thermophysical properties are generic functions of thermodynamic pressure, local temperature and vapour composition, (ii) the Grossmann–Lohse theory for thermal convection can be applied to the liquid and gas layers separately and (iii) the vapour content in the gas can be taken as the mean value at the gas–liquid interface. We validate this setting using direct numerical simulations in a parameter space composed of the Rayleigh number ( $10^6\leq Ra\leq 10^8$ ) and the temperature differential ( $0.05\leq \varepsilon \leq 0.20$ ), which modulates the variation of state variables in the gas layer. To better disentangle the variable property effects on $\varTheta _\varGamma$ and $Nu$ , simulations are performed in two conditions. First, we consider the case of uniform gas properties except for the gas density and gas–liquid diffusion coefficient. Second, we include the variation of specific heat capacity, dynamic viscosity and thermal conductivity using realistic equations of state. Irrespective of the employed setting, the proposed model agrees very well with the numerical simulations over the entire range of $Ra$ – $\varepsilon$ investigated.

Numerical investigation of fracturing fluid invasion into hydrate reservoirs during hydraulic-fracturing stimulation

Hydraulic fracturing is a potentially promising stimulation technology employed for enhancing gas productivity and energy efficiency of low-permeability hydrate reservoirs. At present, most studies in the field of hydrate reservoir fracturing have mainly focused on the fracturing feasibility and recovery efficiency without considering the effects of fracturing fluids on hydrate reservoirs. However, fracturing fluid will inevitably invade hydrate reservoirs driven by high fracturing pressure, which may cause hydrate phase transitions and consequently affects fracturing. In this study, the dynamic process of fracturing fluid invasion into hydrate reservoir was simulated using the TOUGH+HYDRATE software, primarily focusing on the differences between the fracturing fluid invasion into the gas hydrate-bearing layer (GHBL), three-phase layer (TPL), and free gas layer (FGL). The results showed that a secondary hydrate column was formed within 2–10 m around the fracture by the fracturing fluid/free water and free gas during fracturing fluid invasion into the TPL and FGL, which was mainly driven by the large driving force exerted by high fracturing pressure. But the exothermic reaction of hydrate formation can provide negative feedback to the formation and expansion of the secondary hydrate column, leading to a state of phase equilibrium in the secondary hydrate formation region and the outward expansion of the secondary hydrate column in a “three-phase equilibrium” mode. It should be noted that secondary hydrate formation did not occur during fracturing fluid invasion into GHBL because of the absence of free gas, and fracturing fluid invasion into GHBL only affected reservoir temperature and pressure, which was similar to the fracturing fluid invasion into unconventional oil and gas layers. These results will provide important guidance for the potential application of hydraulic fracturing in the field tests of hydrate reservoirs and its scheme formulation.

A numerical study on film condensation of steam with non-condensable gas on a vertical plate

The film condensation of steam is very common in several industrial areas, such as condensers in power plants, seawater desalination, and air-conditioning systems. In some studies, the non-condensable gas and liquid film are overlooked for the sake of simplicity. To provide an integral computational scheme, in the present study, the film condensation of steam in the presence of non-condensable gas on a vertical plate has been simulated using a two-dimensional CFD model combining a wall condensation model and volume of fluid (VOF) model. After verification, the proposed computational scheme is used to simulate the steam condensation process, with the mass fractions of non-condensable gas varying from 5% to 45%. The results indicate that the concentration of non-condensable gas in the boundary layer decreases gradually with the condensation process, resulting in a decline in the synergy between temperature and velocity field. It can also be found that the fluctuation of the liquid film can influence the concentration distribution of the non-condensable gas layer. For cases with high concentrations of steam, the thermal resistance of liquid film can reach more than 20% of the total thermal resistance, which should not be ignored.

Measurement of hydrogen dispersion in rock cores using benchtop NMR

Electrolysis followed by underground hydrogen storage (UHS) in both salt caverns and depleted oil and gas reservoirs is widely considered as a potential option to overcome fluctuations in energy provision from intermittent renewable sources. Particularly in the case of depleted oil and gas reservoirs, a denser layer of cushion gas (N2, CH4 or CO2) can be accommodated in these storage volumes to allow for sufficient system pressure control as hydrogen is periodically injected and extracted. These gases/fluids are however fully soluble with hydrogen and thus with sufficient mixing can undesirably contaminate the extracted hydrogen product. Fluid mixing in a porous medium is typically characterized by a dispersion coefficient (KL), which is hence a critical input parameter into reservoir simulations of underground hydrogen storage. Such dispersion data is however not readily available in the literature for hydrogen at relevant storage conditions. Here we have developed and demonstrated novel methodology for the measurement of KL between hydrogen and nitrogen in a Berea sandstone at 50 bar as a function of displacement velocity (0.007–0.722 mm/s). This leverages off previous work quantifying KL between carbon dioxide and methane in rock cores relevant to enhanced gas recovery (EGR). This used infrared (IR) spectroscopy to differentiate the two fluids, hydrogen is however IR invisible. Hence the required time-resolved quantification of hydrogen concentration emerging from the rock core is uniquely performed here using bench-top nuclear magnetic resonance (NMR). The resultant hydrogen-nitrogen dispersion data as a function of displacement velocity allows for the determination of dispersivity (α = 0.31 mm). This intrinsic rock property compares favorably with previous CO2 dispersion measurements on similar sandstones, hence validating our methodology to some extent. In addition, at very low velocities, determination of the rock core tortuosity (τ, another intrinsic rock property) produces a value (τ = 10.9) that is similar to that measurement independently using pulsed field gradient NMR methods (τ = 11.3).

Study on Monitoring Reservoir Gas Density by Pulsed Neutron Logging

In mature multilayer gas reservoirs, it is a common problem to evaluate whether a potential reservoir is still productive after casing. Monitoring of unproduced or developing gas formations can guide production action plans. Intervention in unperforated zones with high gas density can increase gas production, whereas intervention in zones with low gas density is uneconomical. An RPM instrument stratum model was established by using the Monte Carlo method in this study. The model was used to simulate the response characteristics of pulsed neutron logging in a sandstone reservoir with 100% gas saturation to different reservoir gas densities, formation porosity, and shale content. The data obtained from the simulation were interpolated to construct a capture gamma ratio plate and a nonbounce gamma ratio plate. Using the constructed chart, the gas density of the reservoir can be quantitatively calculated, and then, the recovery value of the potential gas layer can be evaluated.

Exploration and development in the Zhaotong national shale gas demonstration area: Progress and prospects

The Zhaotong national shale gas demonstration area in Yunnan (hereinafter referred to as demonstration area) is China's third largest national shale gas production base after Changning–Weiyuan in Sichuan and Fuling in Chongqing. And after more than ten years of deep and careful cultivation, a series of important achievements have been obtained in the exploration and development. From the perspective of exploration and development history, theory and technology, this paper systematically summarizes the exploration discovery process and productivity construction progress of shale gas in the demonstration area, expounds the geological exploration theories and key technologies of mountain shale gas, and predicts their development prospect and direction. And the following research results are obtained. First, the exploration and development in the demonstration area has gone through five development stages, and so far, three major productivity construction zones have been formed, including Huangjinba and Zijinba middle–deep shale gas zones and Taiyang shallow shale gas zone, with cumulative proved geological reserves more than 3100 × 108 m3 and cumulative gas production more than 72 × 108 m3. It has been constructed into the third largest green shale gas demonstration base in China. Second, the “multi-field coordination and multi-element coupling” mountain shale gas enrichment, accumulation and occurrence theory of “sedimentary background controlling source rock and reservoir, reworking intensity controlling preservation, and three-dimensional sealing controlling enrichment” is put forward innovatively, and the “three-dimensional sealing system” accumulation model of extrabasinal shallow shale gas is established. Third, a series of zone selection and evaluation technologies for mountain shale gas in strongly reworked complex structural areas have been developed, and the concept of geology–engineering integration has first been adopted to create transparent shale gas reservoirs and cultivate high-yield wells. A major exploration breakthrough has been achieved from marginal basin medium deep shale gas layers to extrabasin ultra shallow to medium shallow ones, and domestic first large-scale monoblock shallow shale gas field with reserves over 2570 × 108 m3 has been discovered. Fourth, a landmark technological achievement and efficient development model with geology–engineering integration and shale geomechanical evaluation as the core has been formed, which leads the clean, green and efficient exploration and development of mountain shale gas. In conclusion, it is necessary to implement the exploration strategic idea of “two outgoing” in the demonstration area, i.e., “walking out of the stable area of the basin and marching into the complex structure areas in the Dianqianbei Depression” and “walking out of the Wufeng–Longmaxi Formation and exploring other layers for breakthrough”. What's more, it is recommended to carry out the double-layer stereoscopic horizontal well pattern deployment of “Leping Formation CBM (coal measure gas) + Longmaxi Formation shale gas” appropriately in a large scale, so as to establish a new integrated development model for the three-dimensional efficient development of mountain shale gas and CBM.

Coalescence delay mediated by the gas layer during the impact of hot droplets

Coalescence may not occur immediately when droplets impact a liquid film. Despite the prevalence of the high-temperature condition during the impact process in many applications, the effect of droplet temperature on droplet coalescence is rarely considered. In this study, we experimentally investigate the droplet coalescence during the impact of hot droplets on a liquid film by using color interferometry, high-speed imaging, and infrared imaging. We find that the coalescence of the hot droplet with the liquid film can be delayed which is mediated by the intervening gas layer between the droplet and the film. Compared with droplets at room temperature, the residence time of hot droplets can increase by more than two orders of magnitude. We find that the thickness of the gas layer increases with the droplet temperature, explaining that the thermal delay of coalescence is due to the thicker gas layer. During the hot droplet impact, the temperature gradient at the bottom of the droplet induces Maranogni flow, which can delay the drainage of the intervening gas layer. The results also show that as the Weber number increases, the residence time of the droplet decreases because of the thinner thickness of the gas layer.

Nonlinear wave interactions on the surface of a conducting fluid under vertical electric fields

In this paper, we are concerned with capillary–gravity waves propagating on a two-dimensional conducting fluid under the effect of an electric field imposed in the direction perpendicular to the undisturbed free surface. This work aims to investigate the impact of the electric fields on the nonlinear wave interactions in this context. The full system is mathematically difficult to solve since it is a nonlinear, two-layered, free boundary problem, and the interface dynamics results from the strong coupling between the Euler equations for the lower fluid layer and an electric contribution from the upper gas layer. To investigate electrohydrodynamic wave interactions, we propose a novel numerical scheme based on a time-dependent conformal map and an interpolation technique to conduct unsteady simulations of the fully nonlinear electrified Euler equations of the two-layered problem. To gain analytical insights, we first derive weakly nonlinear envelope equations based on the method of multiple scales for the resonant triad, long-short wave interaction, and modulation of a single-mode wavetrain (a special case of resonant quartet interaction). Summative remarks are made to illustrate the transition from 3-wave interactions to 4-wave interactions and vice versa, occurring when the coefficients of the associated nonlinear Schrödinger equation become singular. The fully nonlinear results obtained by the prescribed numerical method are compared with the predictions by the weakly nonlinear theories, and good agreement is achieved.

Numerical Simulation and Sensitivity Analysis of Hydraulic Fracturing in Multilayered Thin Tight Sandstone Gas Reservoir

Hydraulic fracturing is a necessary measurement to realize the commercial exploitation of oil and gas, but its application in multilayered thin tight sandstone gas reservoirs is still not perfect, which usually have thin gas layers mixed with complex intervals, and shows a dramatic variation in geological and geomechanical properties in the vertical direction. When conventional hydraulic fracturing methods are applied to this kind of reservoir, it is hard to get proper fracture propagation, especially for fracture height control. Facing this situation, this paper proposes a numerical study of the hydraulic fracturing mechanism and analyzes its influencing factors in the multilayered thin tight sandstone gas reservoir. Relying on a real reservoir in the Ordos Basin in China, relevant geological and geomechanical parameters of major gas layers and interlayers are obtained. According to these parameters, the hydraulic fracturing simulation in the multilayered thin tight gas reservoir model is carried out, based on which, the sensitivity analysis of different geological and fracturing parameters which affect the fracture propagation is performed. Furthermore, a real low-production well after fracturing in this kind of reservoir is selected as an example, and based on the analysis, an optimized fracturing scheme is proposed to adapt to the characteristics of the reservoir. According to the comparison of fracturing and production simulations, the optimized fracturing scheme can prevent hydraulic fractures from breaking through thin interlayers, control the fracture height, and prevent fractures from communicating strata with a high water-bearing layer. At the same time, with the same amount of proppant and fracturing fluid, longer fracture length and better fracture conductivity are created, so that the productivity of the optimized fracture has been greatly improved.

Analysis of fault characteristics and oil and gas enrichment differences in the No. 2 structural belt, Nanpu Sag, Bohai Bay Basin, East China

There are great differences in oil and gas enrichment at different locations in petroliferous basins, and faults are an important factor affecting the differential enrichment of oil and gas. In this paper, taking the No. 2 structure in the Nanpu Sag, Bohai Bay Basin, East China, as an example, based on the analysis of fault geometry and kinematics characteristics, the determination of oil source faults, the analysis of fault trap origin and effectiveness, and the analysis of fault caprock combinations are carried out to study the differences and mechanisms of oil and gas enrichment east and west of the Nanpu No. 2 structure. The results show that the fault-source contact relationship affects the direction of oil and gas migration. The No. 2 structure in the Nanpu Sag has a dual-source hydrocarbon supply. The western structure supplies hydrocarbons from the north and east, with oil and gas migrating along the direction parallel and perpendicular to the fault strike. The east structure supplies hydrocarbons from the south and north, with oil and gas migrating along the direction perpendicular to the fault strike. The effectiveness of fault traps affects the scale of oil and gas accumulation. Most of the traps of the Nanpu No. 2 structure formed before hydrocarbon expulsion, which are all effective traps and are conducive to oil and gas accumulation. The relationship between fault and caprock determines the vertical accumulation layers of oil and gas: The faulted thickness of the east structure is large, the fault is vertically closed, and oil and gas are enriched mainly in the deep layer. The faulted thickness of the west structure is small, and oil and gas are enriched in both deep and shallow layers.

A flame technique to isolate the detonation/product interface relevant to rotating detonation engines

A novel experimental technique is proposed to study the detonation propagation in a layer of non-reacted gas weakly confined by combustion products. This problem is relevant to rotating detonation engines, where transverse detonations are confined by products of a previous rotation cycle, and other applications such as industrial safety. The experimental technique utilizes a flame ignited along the top wall in a long channel. The preferential growth of the flame along the long direction of the channel creates a finger flame and permits to create a narrow layer of unburned gas. A detonation ignited outside of this layer then propagates through the layer. This permits to conduct accurate observations of the detonation interaction with the inert gas and determine the boundary condition of the interaction. The present paper provides a proof-of-concept demonstration of the technique in a 3.4 m by 0.2 m channel, in which long finger flames were observed in ethylene-oxygen mixtures. The flame is visualized by high-speed direct luminosity over its entire travel, coupled with pressure measurements. A direct simulation of the flame growth served to supplement the experiments and evaluate the role of the induced flow by the flame growth, which gives rise to a non-uniform velocity distribution along the channel length. Detonation experiments were also performed at various layer heights in order to establish the details of the interaction. The structure was visualized using high speed Schlieren video. It was found that an inert shock always runs ahead of the detonation wave, which gives rise to a unique double shock reflection interaction.