Oil blob populations and mobilization of trapped oil in unconsolidated packs

Wardlaw, N. C.; McKellar, M.

doi:10.1002/cjce.5450630401

Cited by 72 publications

(50 citation statements)

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“…5.2.6. The phenomenon that mobilization of residual oil starts at a critical capillary number has been repeatedly observed in early researches (Chatzis and Morrow 1984;Wardlaw and McKellar 1985;Wardlaw 1988). An additional proof of the threshold for production of discontinuous oil was obtained in this study.…”

Section: Influence Of Interfacial Tension and Wettability On The Tertmentioning

confidence: 73%

“…Therefore, when water permeability is decreased, some or all traps in the porous network become harsher at the same time. Wardlaw and McKellar (1985) observed that the larger oil blobs were disconnected repeatedly during mobilization. It can also be found from their elaborate distributions where the sizes of blobs decreased with subsequent increases in capillary number.…”

Section: Fundamentals In Tertiary Oil Recovery Associated With Water mentioning

confidence: 99%

“…2.2). Although the phenomenon that tertiary oil recovery is strongly related to flow rate has long been observed (Chatzis and Morrow 1984;Wardlaw and McKellar 1985), this fact was neglected in the recently published articles when dealing with the tertiary oil recovery associated with injection of low salinity water (Zhang and Morrow 2006;Loahardjo et al 2007). …”

Section: Influence Of Flow Velocity On Tertiary Oil Recovery Associatmentioning

confidence: 99%

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Oil Recovery by Low Salinity Water Injection into a Reservoir: A New Study of Tertiary Oil Recovery Mechanism

2011

Transp Porous Med

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Low salinity water injections for oil recovery have shown seemingly promising results in the case of clay-bearing sandstones saturated with asphaltic crude oil. Reported data showed that low salinity water injection could provide up to 20% pore volume (PV) of additional oil recovery for core samples and up to 25% PV for reservoirs in near wellbore regions, compared with brine injection at the same Darcy velocity. The question remains as to whether this additional recovery is also attainable in reservoirs. The answer requires a thorough understanding of oil recovery mechanism of low salinity water injections. Numerous hypotheses have been proposed to explain the increased oil recovery using low salinity water, including migration of detached mixed-wet clay particles with absorbed residual oil drops, wettability alteration toward increased water-wetness, and emulsion formation. However, many later reports showed that a higher oil recovery associated with low salinity water injection at the common laboratory flow velocity was neither necessarily accompanied by migration of clay particles, nor necessarily accompanied by emulsion. Moreover, increased water-wetness has been shown to cause the reduction of oil recovery. The present study is based on both experimental and theoretical analyses. Our study reveals that the increased oil recovery is only related to the reduction of water permeability due to physical plugging of the porous network by swelling clay aggregates or migrating clay particles and crystals. At a fixed apparent flow velocity, the value of negative pressure gradient along the flow path increases as the water permeability decreases. Some oil drops and blobs can be mobilized under the increased negative pressure gradient and contribute to the additional oil recovery. Based on the revealed mechanism, we conclude that low salinity water injection cannot be superior to brine injection in any clay-bearing sandstone reservoir at the maximum permitted injection pressure. Through our study of low salinity water injection, the theory of tertiary oil recovery has been notably improved. Keywords

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Section: Influence Of Interfacial Tension and Wettability On The Tertmentioning

confidence: 73%

Section: Fundamentals In Tertiary Oil Recovery Associated With Water mentioning

confidence: 99%

Section: Influence Of Flow Velocity On Tertiary Oil Recovery Associatmentioning

confidence: 99%

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Oil Recovery by Low Salinity Water Injection into a Reservoir: A New Study of Tertiary Oil Recovery Mechanism

2011

Transp Porous Med

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“…Since ganglion size has a distribution, the residual saturation (fraction of immobile ganglia volume) is only a fraction of the actual non-wetting-phase saturation. In the past three decades, there has been a lot of experimental and computational work to support this fact, notably the work of Payatakes and his co-workers (Ng, Davis & Scriven 1978;Payatakes 1982;Wardlaw & McKellar 1985;Gioia, Alfani, Andreutti & Murena 2003). For example, Avraam et al (1994) and Avraam & Payatakes (1995a) performed experiments over a wide range of parameters for steady-state two-phase flow and showed that the disconnected oil ganglia contribute substantially to the oil flow.…”

Section: Modelling Of Multi-phase Flow With Ganglia In Porous Mediamentioning

confidence: 99%

Probability density function approach for modelling multi-phase flow with ganglia in porous media

Tyagi

Jenny

2011

J. Fluid Mech.

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A probabilistic approach to model macroscopic behaviour of non-wetting-phase ganglia or blobs in multi-phase flow through porous media is proposed. The key idea is to consider a set of stochastic Markov processes that can mimic the microscopic multi-phase dynamics. These processes are characterized by equilibrium probability density functions (PDFs) and correlation times, which can be obtained from microscale simulation studies or experiments. A Lagrangian viewpoint is adopted, where stochastic particles represent infinitesimal fluid elements and evolve in the physical and probability space. Ganglion mobilization and trapping are modelled by a twostate jump process with transition probabilities given as functions of ganglion size. Coalescence and breakup of ganglia influence the ganglion size distribution, which is modelled by a Langevin type equation. The joint probability density function (JPDF) of the chosen stochastic variables is governed by a high-dimensional Chapman-Kolmogorov equation. This equation can be used to derive moment (e.g. saturation, mean mobility etc.) transport equations, which in general do not form a closed system. However, in some special cases, which arise in the limit of one time scale being smaller or larger than the others, a closed set of moment transport equations can be obtained. For slowly varying and quasi-uniform flows, the saturation transport equation appears in closed form with the mean mobility fully determined, if the equilibrium PDFs are known. Furthermore, it is shown how statistical parameters such as mobilization and trapping rates and equilibrium PDFs can be obtained from the birth-death type approach, in which ganglia breakup and coalescence are explicitly considered. A two-equation transport model (one equation for the total saturation and one for the trapped saturation) is obtained in the limit of very fast coalescence and breakup processes. This model is employed to mimic hysteresis in relative permeability-saturation curves; a well known phenomenon observed in the successive processes of imbibition and drainage. For the general case, the JPDFequation is solved using the stochastic particle method, which was proposed in our previous paper (Tyagi et al. J. Comput. Phys. 227, 2008, 6696-6714). Several one-and two-dimensional numerical simulation results are presented to show the influence of correlation times on the averaged macroscopic flow behaviour.

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“…Typically cosolvent-or surfactant-enhanced aquifer remediation are designed to promote solubilization rather than mobilization, because the latter can lead to uncontrolled movement and expansion of the NAPL zone (Dawson and Roberts, 1997;Ramsburg and Pennell, 2002;Wardlaw and McKellar, 1985). Therefore, one of the important criteria in design of in-situ cosolvent flushing, is achieving maximum solubility enhancement with minimum potential of NAPL mobilization.…”

Section: Napl Mobilization and Total Trapping Numbermentioning

confidence: 99%