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The success of foam-induced flow diversion in fractured carbonates hinges on proper injection strategies, requiring an in-depth understanding of the factors responsible for stimulating fracture–matrix interactions. In this study, we present a novel investigation of the interactions between the fracture and the matrix influenced by the mobility control effect during CH4-foam injections. These interactions were probed at the pore scale using a three-phase flow system integrated with a high-resolution micro-CT scanner. In situ phase saturations were monitored and quantified to interpret the resulting fluid transport at various injection parameters. At the initial stage of foam injection, the surfactant solution was able to invade the matrix leading to water/oil displacement events, however, impeding gas penetration. Increasing total injection velocity produced higher in situ foam quality in the fracture than the injected quality, where significant fraction of the surfactant solution from the foam was primarily diverted into the matrix. A pronounced increase in the average gas saturation within the matrix was only observed at the highest injection velocity. The pore-scale evidence showed the occurrence of combined displacement processes (water/oil, gas/oil, gas/oil/water) in the matrix, attributed to the established mobility control in the fracture, which contributed to the diversion of surfactant solution and gas to the matrix. Lastly, the injection–soaking–production technique effectively mobilized the residual oil after a long injection process of CH4-foam. At this stage, the surfactant solution was no longer playing a role as the primary invading fluid; rather, it was the diverted gas that led to the increase in the matrix-oil production. [ABSTRACT FROM AUTHOR]

Optimal core length for enhanced oil recovery (EOR) core flood experiments lacks consensus. Shorter cores are commonly used, but assessing sweep efficiency in mobility control EOR methods, crucial for longer inter-well distances, remains a question. The adequacy of shorter cores in evaluating sweep efficiency in these EOR processes needs attention. Despite the recognized importance of core flood for enhanced oil recovery (EOR) applications, there is no consensus in the literature on the optimal core length to be used in displacement experiments. Therefore, it is important to address the key question "whether the shorter length cores are sufficient for proper sweep efficiency evaluation in mobility control-based EOR processes?". The objective of this study is to investigate the effect of core length on the core-scale sweep efficiency and ultimate recovery for the displacement experiments carried out at different viscosity ratios between injected fluid and residing oil. Two identical core flooding experiments were conducted using cores that have similar porous media properties ensured through chromatography scan (CT) but have different lengths of 3 and 7 inches. Two different viscosity ratio conditions (10, 0.1) were imposed sequentially in each of the core flooding experiments by injecting water at 2 ft/day as a primary slug and then 2,000 ppm HPAM polymer solutions at 0.25 ft/day as the secondary slug. The results suggest that the use of shorter-length cores for displacement experiments under unfavourable viscosity ratio conditions would overestimate the early sweep effect by over 10%. In contrast, polymer flood conducted under favourable viscosity ratio conditions resulted in a higher-pressure gradient of 95 psi and showed only a marginal ∼ 2% difference in the incremental recovery factor between shorter and longer cores from ∼ 0.4 PV to 1.9 PV injections. [ABSTRACT FROM AUTHOR]

Efficient routing is one of the key challenges in mobile ad hoc networks due to stringent requirements and deployment demands in many safety-critical application contexts such as disaster rescue operations and battlefields. In most cases, the autonomous nature of node mobility causes frequent link failures and critical packet loss, which affects the overall performance of the underlying routing function. In this paper, we proposed a novel mobility control mechanism that guides the mobility behavior of the ad hoc nodes that may potentially move out of range from others. Designated coordinator nodes allocated by weighted clustering algorithm periodically execute the mobility control function to predict the future trajectories of the mobile nodes in terms of their mobility states using extreme learning machine approach. Accordingly, appropriate control packets are sent by the coordinator nodes to the nodes that may potentially move out of range from others in order to modify their future mobility states. This, in turn, drives the routing function by efficiently avoiding the unexpected route breaks and packet loss, rather yielding higher route availability. The in-depth simulation results report that the proposed mobility control mechanism significantly yields better performance compared to the state-of-the-art approaches and shows robust behavior even in highly mobile tactical and safety-critical scenarios. [ABSTRACT FROM AUTHOR]

The purpose of the research is to propose a novel method of mobility control of condensed water by melamine during steam flooding process. Melamine is working as water permeability modifier in a non-foaming manner to control mobility of condensed water, supported by the theoretic analysis. Wettability alternatation, water residual resistance factor, and oil displacement efficiecy by melamine addition were investigated in the experiments. The contact angle was decreased by 3.6° at 200 °C indicating that the core tends to be more water wet upon addition of melamine. Water residual resistance factor, approximately representing water/oil mobility ratio, increased in response to the temperature elevation and increased pore volume during melamine injection. Water residual resistance factor reached close to 1 after subsequent hot water flood, which indicated that the reduced water permeability by melamine precipitation could be restored. The oil recovery by saturated melamine injection was increasd by 11.7% when temperature dropped from 200 to 160 °C, in comparison with pure water flooding under the same condition. The results verify the feasibility of melamine to enhance oil recovery by controlling mobility of condensed water in a steam flooding process. [ABSTRACT FROM AUTHOR]

The interest shown by some community of researchers to autonomous drones or UAVs (unmanned aerial vehicles) has increased with the advent of wireless communication networks. These networks allow UAVs to cooperate more efficiently in an ad hoc manner in order to achieve specific tasks in specific environments. To do so, each drone navigates autonomously while staying connected with other nodes in its group via radio links. This connectivity can deliberately be maintained for a while constraining the mobility of the drones. This will be suitable for the drones involved in a given path of a given transmission between a source and a destination. This constraint could be removed at the end of the transmission process and the mobility of each concerned drone becomes again independent from the others. In this work, we proposed a flocking-based routing protocol for UAVs called BR-AODV. The protocol takes advantage of a well known ad hoc routing protocol for on-demand route computation, and the Boids of Reynolds mechanism for connectivity and route maintaining while data is being transmitted. Moreover, an automatic ground base stations discovery mechanism has been introduced for a proactive drones and ground networks association needed for the context of real-time applications. The performance of BR-AODV was evaluated and compared with that of classical AODV routing protocol and the results show that BR-AODV outperforms AODV in terms of delay, throughput and packet loss. [ABSTRACT FROM AUTHOR]

This paper introduces a new mobility control method for surveillance applications of wireless sensor and actor networks. The proposed method is based on virtual electrostatic forces which act on actors to coordinate their movements. The definition of virtual forces is inspired by Coulomb's law from physics. Each actor calculates the virtual forces independently based on known locations of its neighbours and predetermined borders of the monitored area. The virtual forces generate movements of actors. This approach enables effective deployment of actors at the initial stage as well as adaptation of actors' placement to variable conditions during execution of the surveillance task without the need of any central controller. Effectiveness of the introduced method was experimentally evaluated in a simulation environment. The experimental results demonstrate that the proposed method enables more effective organization of the actors' mobility than state-of-the-art approaches. [ABSTRACT FROM AUTHOR]

$$\hbox {CO}_{2}$$ flood is one of the most successful and promising enhanced oil recovery technologies. However, the displacement is limited by viscous fingering, gravity segregation and reservoir heterogeneity. Foaming the $$\hbox {CO}_{2}$$ and brine with a tailored surfactant can simultaneously address these three problems and improve the recovery efficiency. Commonly chosen surfactants as foaming agents are either anionic or cationic in class. These charged surfactants are insoluble in either $$\hbox {CO}_{2}$$ gas phase or supercritical phase and can only be injected with water. However, some novel nonionic or switchable surfactants are $$\hbox {CO}_{2}$$ soluble, thus making it possible to be injected with the $$\hbox {CO}_{2}$$ phase. Since surfactant could be present in both $$\hbox {CO}_{2}$$ and aqueous phases, it is important to understand how the surfactant partition coefficient influences foam transport in porous media. Thus, a 1-D foam simulator embedded with STARS foam model is developed. All test results, from different cases studied, have demonstrated that when surfactant partitions approximately equally between gaseous phase and aqueous phase, foam favors oil displacement in regard to apparent viscosity and foam propagation speed. The test results from the 1-D simulation are compared with the fractional flow theory analysis reported in the literature. [ABSTRACT FROM AUTHOR]

Apparent viscosities of CO-in-water foams were measured in a wide range of shear rate from 50 to 105 inverse second for enhanced oil recovery (EOR) application. The CO-in-water dispersions, made of 50:50 weight proportions of CO and water with 1 wt.% surfactant concentration, were prepared in high-pressure recirculation apparatus under pressure where CO density becomes 0.7, 0.8, and 0.9 g/mL at each temperature of 35, 45, and 55°C. The surfactants used for the foam generation were sodium dodecyl polypropoxy sulfates with average propoxylation degrees of 4.7 and 6.2. The foam viscosity showed shear thinning behaviors with power-law indices ranging from 0.80 to 0.85, and approached a Newtonian regime in the lower shear rate range at several tens of inverse second. Zero-shear viscosity values projected from experimental data based on Ellis model were as high as 57.4 mPa·s and enough to control the mobility of water and CO in oil reservoirs. [ABSTRACT FROM AUTHOR]

Unfavorable mobility ratio and reservoir heterogeneities contribute to water fingering phenomenon that leads to relatively low oil recovery factors in heavy oil fields. Experiments have shown that injection of oil-in-water emulsions can be used as an effective enhanced oil recovery (EOR) method, leading to substantial increase in the volume of oil recovered. Capillary-driven mobility alteration of the water phase by emulsion drops leads to not only more uniform macroscopic reservoir sweep, but also a pore scale reduction in the residual oil saturation. Despite recent developments, fundamental aspects of dilute oil-in-water emulsion flow through porous media and its application as an EOR method are still not clear. Experiments were performed in a 1D flow configuration using silica sandpacks and sandstone cores to determine the effect of permeability, emulsion drop size, dispersed phase concentration and size of injected emulsion bank on the volume of displaced oil, a crude heavy oil from Campos Basin ( $$20^{\circ }$$ API). X-ray computerized tomography images obtained during experiments in a Castlegate sandstone block in a 1/4 5-spot configuration revealed that emulsion acts both in the macroscale and pore scale, improving the macroscopic sweep and lowering the residual oil saturation. [ABSTRACT FROM AUTHOR]

CO flooding is regarded as an important method for enhanced oil recovery (EOR) and greenhouse gas control. However, the heterogeneity prevalently distributed in reservoirs inhibits the performance of this technology. The sweep efficiency can be significantly reduced especially in the presence of 'thief zones'. Hence, gas channeling blocking and mobility control are important technical issues for the success of CO injection. Normally, crosslinked gels have the potential to block gas channels, but the gelation time control poses challenges to this method. In this study, a new method for selectively blocking CO channeling is proposed, which is based on a type of CO-sensitive gel system (modified polyacrylamide-methenamine-resorcinol gel system) to form gel in situ. A CO-sensitive gel system is when gelation or solidification will be triggered by CO in the reservoir to block gas channels. The CO-sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N and CO atmospheres. Sand pack flow experiments were conducted to investigate the shutoff capacity of the gel system under different conditions. The injectivity of the gel system was studied via viscosity measurements. The results indicate that this gel system was sensitive to CO and had good performance of channeling blocking in porous media. Advantageous viscosity-temperature characteristics were achieved in this work. The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs. The experimental results can provide guidelines for the deployment of the CO-sensitive gel system for field applications. [ABSTRACT FROM AUTHOR]

Fast event detection is important in wireless sensor and actor networks (WSANs) since actors can perform appropriate actions which sensor nodes are not capable to do. While WSANs inherits the typical constrains of WSNs such as energy and computation limitations of sensor nodes. In this paper, we propose a fast event detecting algorithm named RENDEZVOUS to accelerate the actor's event detecting process while keep the energy consumption of sensor nodes as minimum. When design RENDEZVOUS, we first study the mobility control of a actor to help the actor move around close to a event by using Reinforcement Learning techniques with collected sensory data. We then design a scheme to search nearby actors from the event side inspired by a searching behavior of desert ants. By both perform search actions from sensor side and actor side, the proposed algorithm can achieve fast event detecting with neglect-able additional energy cost on sensors side. Extensive simulation results demonstrate the efficiency of RENDEZVOUS. [ABSTRACT FROM AUTHOR]

Foam injection is a proven enhanced oil recovery (EOR) technique for heterogeneous reservoirs, but is less studied for EOR in fractured systems. We experimentally investigated tertiary $$\text {CO}_{2}$$ injections, and $$\text {N}_{2}$$ - and $$\text {CO}_{2}$$ -foam injections for enhanced oil recovery in fractured, oil-wet limestone core plugs. Miscible $$\text {CO}_{2}$$ and $$\text {CO}_{2}$$ -foam was compared with immiscible $$\text {CO}_{2}$$ - and $$\text {N}_{2}$$ -foam as tertiary recovery techniques, subsequent to waterfloods, in fractured rocks with different wettability preferences. At water-wet conditions waterfloods produced approximately 40 % OOIP, by spontaneous imbibition. Waterflood oil recovery at oil-wet conditions was below 20 % OOIP, due to suppressed imbibition where water predominantly flowed through the fractures, unable to mobilize the oil trapped in the matrix. Tertiary, supercritical $$\text {CO}_{2}$$ -mobilized oil trapped in the matrix, particularly at weakly oil-wet conditions, by diffusion. Recovery by diffusion was high due to small core samples, high initial oil saturation and a continuous oil phase at oil-wet conditions. Both immiscible $$\text {CO}_{2}$$ - and $$\text {N}_{2}$$ -foams and miscible, supercritical $$\text {CO}_{2}$$ -foam demonstrated high ultimate oil recoveries, but immiscible foam was less efficient (30 pore volumes injected) compared to miscible foam (2 pore volumes injected) to reach ultimate recovery. This is explained by the capillary threshold pressure preventing the injected $$\text {N}_{2}$$ gas from entering the matrix, verified by computed X-ray tomography, and the mobilized oil was displaced by the aqueous surfactant in the foam. At miscible conditions, there exists no capillary entry pressure between the oil-saturated matrix and the injected $$\text {CO}_{2}$$ , allowing foam to invade the matrix for efficient oil recovery. [ABSTRACT FROM AUTHOR]

The uniqueness and sensitivity of foam modeling parameters are crucial for simulating foam flow through porous media. In the absence of oil in the porous medium, the local-equilibrium foam model investigated in this work uses three parameters to describe the foam quality dependence: $$fmmob,\, fmdry$$ , and $$epdry$$ . Even for a specified value of $$epdry$$ , in some cases, two pairs of $$fmmob$$ and $$fmdry$$ values can experimentally match measured transition foam quality ( $$f_\mathrm{g}^{t}$$ ) and transition foam apparent viscosity ( $$\mu _\mathrm{foam,app}^t$$ ). This non-uniqueness can be broken by limiting the solution such that $$fmdry$$ is smaller than the transition water saturation ( $$S_\mathrm{w}^t$$ ). In addition, a three-parameter fit using all experimental data of apparent viscosity versus foam quality was developed to simultaneously estimate $$fmmob,\, fmdry$$ , and $$epdry$$ . However, a better strategy is to conduct and match a transient experiment, in addition to steady-state experiments, in which a gas displaces the surfactant solution at 100 % water saturation. This transient foam quality scans the entire range of fractional flow, and the values of the foam parameters that best match the experiment can be uniquely determined. The numerical artifact of pressure oscillations in simulating this transient foam process was investigated by comparing the finite difference algorithm with the method of characteristics. Sensitivity analyses indicated that the estimated foam parameters were highly dependent on the parameters used for the water and gas relative permeabilities. In particular, the water relative permeability exponent and connate water saturation are important. [ABSTRACT FROM AUTHOR]

Modeling the flow of emulsion in porous media is extremely challenging due to the complex nature of the associated flows and multiscale phenomena. At the pore scale, the dispersed phase size can be of the same order of magnitude of the pore length scale and therefore effective viscosity models do not apply. A physically meaningful macroscopic flow model must incorporate the transport of the dispersed phase through the porous material and the changes on flow resistance due to drop deformation as it flows through pore throats. In this work, we present a dynamic capillary network model that uses experimentally determined pore-level constitutive relationships between flow rate and pressure drop in constricted capillaries to obtain representative transient macroscopic flow behavior emerging from microscopic emulsion flow at the pore level. A parametric analysis is conducted to study the effect of dispersed phase droplet size and capillary number on the flow response to both emulsion and alternating water/emulsion flooding in porous media. The results clearly show that emulsion flooding changes the continuous-phase mobility and consequently flow paths through the porous media, and how the intensity of mobility control can be tuned by the emulsion characteristics. [ABSTRACT FROM AUTHOR]

Power saving is one of the key issues in Mobile Ad-Hoc Networks (MANETs). It can be realized in Medium Access Control (MAC) layer and network layer. However, previous attentions were mainly paid to MAC layer or network layer with the aim of improving the channel utilization by adopting variable-range transmission power control. In this paper we focus on the power saving in both MAC layer and network layer, and propose a Power Adjusting Algorithm (PAA). In the presence of host's mobility, PAA is designed to conserve energy by adjusting the transmission power to maintain the route's connectivity and restarting the route discovery periodically to find a new route with better energy efficiency dynamically. After analyzing the operations of PAA, we find that the length of route discovery restarting period is a critical argument which will affect power saving, and an energy consumption model is abstracted to find the optimal value of the restarting period by analyzing the energy consumption of this algorithm. PAA can handle the mobility of MANET by adjusting the transmission power and in the meantime save energy by restarting route discovery periodically to balance the energy consumption on route discovery and packet delivering. Simulation results show that, PAA saves nearly 40% energy compared with Dynamic Source Routing protocol when the maximum speed of mobile hosts is larger than 8 m/s. [ABSTRACT FROM AUTHOR]

The flow properties of complex fluids through porous media give rise to multiphase flow displacement mechanisms that operate at different scales, from pore-level to Darcy scale. Experiments have shown that injection of oil-in-water emulsions can be used as an effective enhanced-oil recovery (EOR) method, leading to substantial increase in the volume of oil recovered. Pore-scale flow visualization as well as core flooding results available in the literature have demonstrated that the enhanced recovery factor is regulated by the capillary number of the flow. However, the mechanisms by which additional oil is displaced during emulsion injection are still not clear. In this work, we carried out two different experiments to evaluate the effect of emulsion flooding both at pore and macro scales. Visualization of the flow through sand packed between transparent plexiglass parallel plates shows that emulsion flooding improves the pore-level displacement efficiency, leading to lower residual oil saturation. Oil recovery results during emulsion flooding in tertiary mode (after waterflooding) in parallel sandstone cores with very different absolute permeability values prove that emulsion flooding also leads to enhancement of conformance or volumetric sweep efficiency. Combined, the results presented here show that injection of emulsion offers multiscale mechanisms resulting from capillary-driven mobility control. [ABSTRACT FROM AUTHOR]

Recent work in wireless sensor networks, or simply called WSNs, has drawn attention to the mobility capability of each node. In Stojmenovic and Lin (IEEE Trans Parallel Distrib Syst 12: 1023–1032, ), it is proved that the optimal positions of the relay nodes along a single active flow must lie entirely on the line between the source and destination with each node spaced evenly along such a line. Based on this, we propose two practical solutions to control the relay nodes in WSNs to approach their optimal positions in the local relative coordinate system. One uses one-hop neighbor information and the other one uses two-hop neighbor information. Basically, each relay node will approach the midpoint on the line composed of neighbors. For the latter control scheme, we also discuss its different implementation with outdated two-hop neighbor information (lagged by one-round neighbor information exchange and update). This is an improvement since given nodes only reuse the two-hop neighbor information previously saved at its one-hop neighbors and does not require any extra neighbor information collection. All the new methods prevent oscillations by demanding minimal moving distance per round ( MDPR), otherwise the node does not move. Unlike the one presented in Goldenberg et al. (Proceedings of the 5th ACM International Symposium on Mobile Ad Hoc Networking and Computing (Mobihoc’04), pp 163–174 ) using only one-hop neighbor information, our methods will converge more quickly. The experimental results show a substantial improvement on the speed of achieving the optimal configuration and the total moving distance of nodes. [ABSTRACT FROM AUTHOR]

Chang and Slattery (1986, 1988b) introduced a simplified model of dispersion that contains only two empirical parameters. The traditional model of dispersion (Nikolaevskii, 1959; Bear, 1961; Scheidegger, 1961; de Josselin de Jong and Bossen, 1961; Peaceman, 1966; Bear, 1972) has three empirical parameters, two of which can be measured in one-dimensional experiments while the third, the transverse dispersivity, must be measured in experiments in which a two-dimensional concentration profile develops. It is found that nearly the same linear stability behavior results from using either model. [ABSTRACT FROM AUTHOR]

Viscous fingering and gravity tonguing are the consequences of an unstable miscible displacement. Chang and Slattery (1986) performed a linear stability analysis for a miscible displacement considering only the effect of viscosity. Here the effect of gravity is included as well for either a step change or a graduated change in concentration at the injection face during a downward, vertical displacement. If both the mobility ratio and the density ratio are favorable (the viscosity of the displacing fluid is greater than the viscosity of the displaced fluid and, for a downward vertical displacement, the density of the displacing fluid is less than the density of the displaced fluid), the displacement will be stable. If either the mobility ratio or the density ratio is unfavorable, instabilities can form at the injection boundary as the result of infinitesimal perturbations. But if the concentration is changed sufficiently slowly with time at the entrance to the system, the displacement can be stabilized, even if both the mobility ratio and the density ratio are unfavorable. A displacement is more likely to be stable as the aspect ratio (ratio of thickness to width, which is assumed to be less than one) is increased. Commonly the laboratory tests supporting a field trial use nearly the same fluids, porous media, and displacement rates as the field trial they are intended to support. For the laboratory test, the aspect ratio may be the order of one; for the field trial, it may be two orders of magnitude smaller. This means that a laboratory test could indicate that a displacement was stable, while an unstable displacement may be observed in the field. [ABSTRACT FROM AUTHOR]

A linear stability analysis has been performed for a miscible displacement in a semi-infinite system of finite thickness and unbounded width. A more general description of dispersion has been adopted than those used by previous workers. It is shown that, when there is a step change in concentration and the mobility ratio is unfavorable, the displacement can be unstable at the injection boundary. But, if the concentration is changed sufficiently slowly with time at the entrance to the system, the displacement is stable to infinitesimal perturbations, no matter how unfavorable the mobility ratio. When the mobility ratio is favorable, the displacement is unconditionally stable. [ABSTRACT FROM AUTHOR]

A one-dimensional ternary two-phase simulator has been extended to include improved physical properties. These physical properties - such as phase behavior, interfacial tension, residual saturations, relative permeabilities, phase viscosities, wettability, capillary pressure, adsorption and dispersion - are modeled as concentration dependent functions. Their functionality completely controls the chemical flood transport phenomena. In this paper, the influence of phase behavior, interfacial tension reduction, mobility control and wettability alteration on chemical flooding are analyzed. In a subsequent paper the influence of capillary pressure, adsorption, and physical and numerical dispersion will be presented. The main application of the simulator here presented is to describe enhanced oil recovery processes. It may also be applied to describe oil spill cleaning and groundwater contamination. [ABSTRACT FROM AUTHOR]