scholarly journals Foam Generation by Capillary Snap-Off in Flow Across a Sharp Permeability Transition

SPE Journal ◽  
2018 ◽  
Vol 24 (01) ◽  
pp. 116-128 ◽  
Author(s):  
Swej Y. Shah ◽  
Karl-Heinz Wolf ◽  
Rashidah M. Pilus ◽  
William R. Rossen
Keyword(s):  
Porous Media ◽  
Pressure Gradient ◽  
Surfactant Solution ◽  
Permeability Transition ◽  
Small Scale ◽  
Fractional Flow ◽  
The Core ◽  
Foam Generation ◽  
Theoretical Predictions ◽  
Gas Mobility

Summary Foam reduces gas mobility and can improve sweep efficiency in an enhanced-oil-recovery (EOR) process. Previous studies show that foam can be generated in porous media by exceeding a critical velocity or pressure gradient. This requirement is typically met only near the wellbore, and it is uncertain whether foam can propagate several tens of meters away from wells as the local pressure gradient and superficial velocity decreases. Theoretical studies show that foam can be generated, independent of pressure gradient, during flow across an abrupt increase in permeability. In this study, we validate theoretical predictions through a variety of experimental evidence. Coreflood experiments involving simultaneous injection of gas and surfactant solution at field-like velocities are presented. We use model consolidated porous media made out of sintered glass, with a well-characterized permeability transition in each core. The change in permeability in these artificial cores is analogous to sharp, small-scale heterogeneities, such as laminations and cross laminations. Pressure gradient is measured across several sections of the core to identify foam-generation events and the subsequent propagation of foam. X-ray computed tomography (CT) provides dynamic images of the coreflood with an indication of foam presence through phase saturations. We investigate the effects of the magnitude of permeability contrast on foam generation and mobilization. Experiments demonstrate foam generation during simultaneous flow of gas and surfactant solution across a sharp increase in permeability, at field-like velocities. The experimental observations also validate theoretical predictions of the permeability contrast required for foam generation by “snap-off” to occur at a certain gas fractional flow. Pressure-gradient measurements across different sections of the core indicate the presence or absence of foam and the onset of foam generation at the permeability change. There is no foam present in the system before generation at the boundary. CT measurements help visualize foam generation and propagation in terms of a region of high gas saturation developing at the permeability transition and moving downstream. If coarse foam is formed upstream, then it is transformed into stronger foam at the transition. Significant fluctuations are observed in the pressure gradient across the permeability transition, suggesting intermittent plugging and mobilization of flow there. This is the first CT-assisted experimental study of foam generation by snap-off only, at a sharp permeability increase in a consolidated medium. The results of experiments reported in this paper have important consequences for a foam application in highly heterogeneous or layered formations. Not including the effect of heterogeneities on gas mobility reduction in the presence of surfactant could underestimate the efficiency of the displacement process.

scholarly journals Foam Generation in Flow Across a Sharp Permeability Transition: Effect of Velocity and Fractional Flow

SPE Journal ◽  
2019 ◽  
Vol 25 (01) ◽  
pp. 451-464 ◽  
Author(s):  
Swej Y. Shah ◽  
Herru As Syukri ◽  
Karl-Heinz Wolf ◽  
Rashidah M. Pilus ◽  
William R. Rossen
Keyword(s):  
Pressure Gradient ◽  
Capillary Pressure ◽  
Permeability Transition ◽  
Fractional Flow ◽  
Local Pressure ◽  
The Core ◽  
Foam Generation ◽  
Gas Mobility ◽  
Foam Propagation ◽  
Strong Foam

Summary Foam reduces gas mobility and can help improve sweep efficiency in an enhanced-oil-recovery (EOR) process. For the latter, long-distance foam propagation is crucial. In porous media, strong foam generation requires that the local pressure gradient exceed a critical value (▿Pmin). Normally, this happens only in the near-well region. Away from wells, these requirements might not be met, and foam propagation is uncertain. It has been shown theoretically that foam can be generated, independent of pressure gradient, during flow across an abrupt increase in permeability (Rossen 1999). The objective of this study is to validate theoretical explanations through experimental evidence and to quantify the effect of fractional flow on this process. This article is an extension of a recent study (Shah et al. 2018) investigating the effect of permeability contrast on this process. In this study, the effects of fractional flow and total superficial velocity are described. Coreflood experiments were performed in a cylindrical sintered-glass porous medium with two homogeneous layers and a sharp permeability jump in between, representing a lamination or cross lamination. Unlike previous studies of this foam-generation mechanism, in this study, gas and surfactant solution were coinjected at field-like velocities into a medium that was first flooded to steady state with gas/brine coinjection. The pressure gradient is measured across several sections of the core. X-ray computed tomography (CT) is used to generate dynamic phase-saturation maps as foam generates and propagates through the core. We investigate the effects of velocity and injected-gas fractional flow on foam generation and mobilization by systematically changing these variables through multiple experiments. The core is thoroughly cleaned after each experiment to remove any trapped gas and to ensure no hysteresis. Local pressure measurements and CT-based saturation maps confirm that foam is generated at the permeability transition, and it then propagates downstream to the outlet of the core. A significant reduction in gas mobility is observed, even at low superficial velocities. Foam was generated in all cases, at all the injected conditions tested; however, at the lowest velocity tested, strong foam did not propagate all the way to the outlet of the core. Although foam generation was triggered across the permeability boundary at this velocity, it appeared that, for our system, the limit of foam propagation, in terms of a minimum-driving-force requirement, was reached at this low rate. CT images were used to quantify the accumulation of liquid near the permeability jump, causing local capillary pressure to fall below the critical capillary pressure required for snap-off. This leads to foam generation by snap-off. At the tested fractional flows, no clear trend was observed between foam strength and fg. For a given permeability contrast, foam generation was observed at higher gas fractions than predicted by previous work (Rossen 1999). Significant fluctuations in pressure gradient accompanied the process of foam generation, indicating a degree of intermittency in the generation rate—probably reflecting cycles of foam generation, dryout, imbibition, and then generation. The intermittency of foam generation was found to increase with decreasing injection velocities and increasing fractional flow. Within the range of conditions tested, the onset of foam generation (identified by the rise in ▿P and Sg) occurs after roughly the same amount of surfactant injection, independent of fractional flow or injection rate.

Experimental Study of Foam Generation, Sweep Efficiency, and Flow in a Fracture Network

SPE Journal ◽  
2016 ◽  
Vol 21 (04) ◽  
pp. 1140-1150 ◽  
Author(s):  
M. A. Fernø ◽  
J.. Gauteplass ◽  
M.. Pancharoen ◽  
A.. Haugen ◽  
A.. Graue ◽  
...  
Keyword(s):  
Flow Behavior ◽  
Fractured Reservoirs ◽  
Surfactant Solution ◽  
Fracture Network ◽  
Mobility Control ◽  
Fractional Flow ◽  
Sweep Efficiency ◽  
Foam Generation ◽  
Gas Mobility ◽  
Mobility Reduction

Summary Foam generation for gas mobility reduction in porous media is a well-known method and frequently used in field applications. Application of foam in fractured reservoirs has hitherto not been widely implemented, mainly because foam generation and transport in fractured systems are not clearly understood. In this laboratory work, we experimentally evaluate foam generation in a network of fractures within fractured carbonate slabs. Foam is consistently generated by snap-off in the rough-walled, calcite fracture network during surfactant-alternating-gas (SAG) injection and coinjection of gas and surfactant solution over a range of gas fractional flows. Boundary conditions are systematically changed including gas fractional flow, total flow rate, and liquid rates. Local sweep efficiency is evaluated through visualization of the propagation front and compared for pure gas injection, SAG injection, and coinjection. Foam as a mobility-control agent resulted in significantly improved areal sweep and delayed gas breakthrough. Gas-mobility reduction factors varied from approximately 200 to more than 1,000, consistent with observations of improved areal sweep. A shear-thinning foam flow behavior was observed in the fracture networks over a range of gas fractional flows.

Modeling Techniques for Foam Flow in Porous Media

SPE Journal ◽  
2015 ◽  
Vol 20 (03) ◽  
pp. 453-470 ◽  
Author(s):  
Kun Ma ◽  
Guangwei Ren ◽  
Khalid Mateen ◽  
Danielle Morel ◽  
Philippe Cordelier
Keyword(s):  
Porous Media ◽  
Relative Permeability ◽  
Population Balance ◽  
Flow In Porous Media ◽  
Fractional Flow ◽  
Foam Flow ◽  
Foam Generation ◽  
Modeling Techniques ◽  
Foam Modeling ◽  
Gas Mobility

Summary Foam, a dispersion of gas in liquid, has been investigated as a tool for gas-mobility and conformance control in porous media for a variety of applications since the late 1950s. These applications include enhanced oil recovery, matrix-acidization treatments, gas-leakage prevention, as well as contaminated-aquifer remediation. To understand the complex physics of foam in porous media and to implement foam processes in a more-controllable way, various foam-modeling techniques were developed in the past 3 decades. This paper reviews modeling approaches obtained from different publications for describing foam flow through porous media. Specifically, we tabulate models on the basis of their respective characteristics, including implicit-texture as well as mechanistic population-balance foam models. In various population-balance models, how foam texture is obtained and how gas mobility is altered as a function of foam texture, among other variables, are presented and compared. It is generally understood that both the gas relative permeability and viscosity vary in the reduction of gas mobility through foam generation in porous media. However, because the two parameters appear together in the Darcy equation, different approaches were taken to alter the mobility in the various models: only reduction of gas relative permeability, increasing of effective gas viscosity, or a combination of both. The applicability and limitations of each approach are discussed. How various foam-generation mechanisms play a role in the foam-generation function in mechanistic models is also discussed in this review, which is indispensable to reconcile the findings from different publications. In addition, other foam-modeling methods, such as the approaches that use fractional-flow theory and those that use percolation theory, are also reviewed in this work. Several challenges for foam modeling, including model selection and enhancement, fitting parameters to data, modeling oil effect on foam behavior, and scaling up of foam models, are also discussed at the end of this paper.

scholarly journals Foam Generation in Flow Across a Sharp Permeability Transition: Effect of Velocity and Fractional Flow

2019 ◽  
Author(s):  
Swej Shah ◽  
Herru As Syukri ◽  
Karl-Heinz Wolf ◽  
Rashidah Pilus ◽  
William Rossen
Keyword(s):  
Permeability Transition ◽  
Fractional Flow ◽  
Transition Effect ◽  
Foam Generation

CO2 Mobility Control

1984 ◽  
Vol 24 (02) ◽  
pp. 191-196 ◽  
Author(s):  
Stan E. Dellinger ◽  
John T. Patton ◽  
Stan T. Holbrook
Keyword(s):  
Crude Oil ◽  
Foam Stability ◽  
Surfactant Solution ◽  
Mobility Control ◽  
Reservoir Rock ◽  
Lauryl Sulfate ◽  
Foam Generation ◽  
Gas Mobility ◽  
Gas Channeling

Abstract As early as 1955, surfactants were recognized for their effectiveness in lowering gas mobility in reservoir cores by in-situ foam generation. For commercial field application a specific surfactant must have several important characteristics. it must behighly effective with low cost,chemically stable, soluble. and surface active in oil field brines, andunaffected by contact with crude oil or reservoir minerals. A static foam generator, an adaptation of a conventional blender, was used to screen more than 150 candidate surfactants. Promising additives were then ranked in a unique dynamic test, developed at New Mexico State U., that involves sequential liquid/gas flow in a vertical tube packed with glass beads. Conventional flow tests in tight, unconsolidated sandpacks show good correlation with the dynamic and static screening tests, especially those data obtained in the dynamic experiment. Some synergism exists between additives with amine oxides and amides having the most beneficial effect on foam stability and gas mobility control. The utility of cosurfactant stabilization was demonstrated in linear, two-phase flow tests through tight. unconsolidated sandpacks involving brine and gas. A solution containing 0.45% Alipal CD-128 (TM) and 0.05% Monamid 150-AD (TM) can decrease gas mobility over 100-fold. The effect appears to be time-independent, indicative of good foam stability. Alipal CD-128 alone reduces gas mobility even more, usually by a factor of two. The moderating influence of a cosurfactant could be beneficial in avoiding "overcontrol" of mobility, especially in low-permeability reservoirs. Introduction For more than 30 years recovery experts have known that CO2 possesses a unique ability to displace crude oil from reservoir rock. Although many gases have been tested for their crude-displacing efficacy, only CO2 has the ability to reduce residual oil saturations to near zero and produce significant quantities of tertiary oil in models that have been previously waterflooded to the economic limit. Early studies provided the fundamental understanding required to explain the high efficiency of CO2, but until recently the depressed price of crude has made most, if not all, CO2 field applications unprofitable. A common failing among-as-driven oil recovery processes is the severe gas channeling that occurs in the reservoir because of excessively high gas mobility. Optimistic oil recoveries obtained in laboratory flow tests with small-diameter, linear models have never been achieved in the field. Both miscible and immiscible drive processes suffer because gas channeling causes most of the oil reservoir to be bypassed and the oil left behind. The earliest work relative to the problem of lowering the mobility of CO2 does not involve CO2 at all. Because of the high potential for miscible drives that use enriched gas mixtures, considerable study was undertaken in the late 1950's on techniques to mitigate gas channeling. A few visionary investigators considered the use of foams as a possible solution to the problem. The earliest reported work was conducted by Bond and Holbrook, whose 1958 patent describes the use of foams in gas-drive processes. Because of the high cost of CO2 relative to crude oil during this period, CO2 processes were ignored. The use of foams in conjunction with CO2, was not contemplated until much later when rising crude prices revived interest in the CO2 displacement technique. CO2 exists as a dense gas or supercritical phase under reservoir conditions: therefore, experiments on controlling gas mobility are usually applicable to CO2 even though they may have been conducted with other gases such as nitrogen, methane, or even air. Concurrent with Bond and Holbrook's work, Fried, working at the USBM laboratory in San Francisco, demonstrated the potential of foam to lower the mobility of an injected gas phase. Fried's work was followed by some excellent work reporting an experimental technique involving in-situ foam generation promoted by injecting alternate slugs of surfactant solution and gas. Their patent related to the use of foam for mobility control in CO2 injection processes is especially pertinent. Laboratory work was encouraging enough that Union Oil Co. conducted a field test in the Siggins field, IL. Foam generation by alternate-slug injection and simultaneous gas-solution injection was tested. This test indicated that at concentrations below 1% the foaming agent, a modified ammonium lauryl sulfate, did not produce an effective foam. Above 1%, reduced gas mobility was obtained; however, at least 0.06 PV of surfactant solution had to be injected to achieve lasting mobility control. Since the tests were conducted sequentially, with the higher concentrations injected last, it is possible that the required amount of surfactant may be understated. A 0.1-PV bank might be more realistic for lasting mobility control. Their results also indicated that adsorption may reduce the effectiveness of a surfactant. It was suggested that future tests might benefit by selection of agents that are less strongly absorbed than ammonium lauryl sulfate. SPEJ P. 191^

Foam Generation in Porous Media

2002 ◽  
Author(s):  
P.A. Gauglitz ◽  
F. Friedmann ◽  
S.I. Kam ◽  
W.R. Rossen
Keyword(s):  
Porous Media ◽  
Foam Generation

A simplified method for fault detection and identification of mismatch modules and strings in a grid-tied solar photovoltaic system

2020 ◽  
Vol 21 (4) ◽  
Author(s):  
Namani Rakesh ◽  
Sanchari Banerjee ◽  
Senthilkumar Subramaniam ◽  
Natarajan Babu
Keyword(s):  
Characteristic Curve ◽  
Dynamic Change ◽  
Photovoltaic System ◽  
Small Scale ◽  
Pv System ◽  
Pv Array ◽  
Detection And Identification ◽  
Fault Detection And Identification ◽  
Theoretical Predictions ◽  
Solar Photovoltaic System

AbstractThe foremost problem facing by the photovoltaic (PV) system is to identify the faults and partial shade conditions. Further, the power loss can be avoided by knowing the number of faulty modules and strings. Hence, to attend these problems, a new method is proposed to differentiate the faults and partially shaded conditions along with the number of mismatch modules and strings for a dynamic change in irradiation. The proposed method has developed in two main steps based on a simple observation from the Current versus Voltage (I-V) characteristic curve of PV array at Line-Line (LL) fault. First, the type of fault is detected using defined variables, which are continuously updated from PV array voltage, current, and irradiation. Second, it gives the number of mismatch modules (or short-circuited bypass diodes) and mismatch strings (or open-circuited blocking diodes) by comparing with the theoretical predictions from the I-V characteristic curve of PV array. The proposed algorithm has been validated both on experimentation using small scale grid-connected PV array developed in the laboratory as well as MATLAB/Simulink simulations. Further, the comparative assessment with existing methods is presented with various performance indices to show the effectiveness of the proposed algorithm.

Kalmag: a high spatio temporal model of the Geomagnetic field

2021 ◽  
Author(s):  
Julien Baerenzung ◽  
Matthias Holschneider
Keyword(s):  
Geomagnetic Field ◽  
Learning Algorithm ◽  
Dynamical Evolution ◽  
Small Scale ◽  
Large Set ◽  
The Core ◽  
Resolution Model ◽  
Auto Regressive ◽  
Spatio Temporal ◽  
Marine Vessels

<p>We present a new high resolution model of the Geomagnetic field spanning the last 121 years. The model derives from a large set of data taken by low orbiting satellites, ground based observatories, marine vessels, airplane and during land surveys. It is obtained by combining a Kalman filter to a smoothing algorithm. Seven different magnetic sources are taken into account. Three of them are of internal origin. These are the core, the lithospheric  and the induced / residual ionospheric fields. The other four sources are of external origin. They are composed by a close, a remote and a fluctuating magnetospheric fields as well as a source associated with field aligned currents. The dynamical evolution of each source is prescribed by an auto regressive process of either first or second order, except for the lithospheric field which is assumed to be static. The parameters of the processes were estimated through a machine learning algorithm with a sample of data taken by the low orbiting satellites of the CHAMP and Swarm missions. In this presentation we will mostly focus on the rapid variations of the core field, and the small scale lithospheric field.  We will also discuss the nature of model uncertainties and the limitiations they imply.</p>

Plasma Resource Recovery Technology: Converting Waste to Energy and Valuable Products

2005 ◽  
Author(s):  
Pierre Carabin ◽  
Gillian Holcroft
Keyword(s):  
Carbon Monoxide ◽  
Construction Material ◽  
Resource Recovery ◽  
Waste To Energy ◽  
Small Scale ◽  
Cruise Ship ◽  
Plasma Flame ◽  
Fuel Gas ◽  
The Core ◽  
Core Technology

Plasma Resource Recovery (PRR) is a revolutionary technology that can treat virtually any type of waste by combining gasification with vitrification. Vitrification produces inert slag that can be used as a construction material. Gasification produces a fuel gas containing carbon monoxide (CO) and hydrogen (H2), used for cogeneration of electricity and steam. The plasma fired eductor which is the core technology of the PRR system is presently being used commercially on a cruise ship at a scale of 5 TPD. The capabilities of the PRR technology have been demonstrated in a pilot plant, at a rate of up to 2 TPD of various types of waste. Because of the high intensity of the plasma flame and the reduced amounts of gases produced in a gasification system, compared to traditional combustion systems, the PRR system is typically very compact. As such, the PRR technology opens the door for a decentralized, small scale approach to waste management.

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