Injectivity and Gravity Override in Surfactant-Alternating-Gas Foam Processes

Rossen, W.; Kibodeaux, K.; Shi, J.-X.; Zeilinger, S.; Lim, M.

doi:10.2523/30753-ms

Cited by 2 publications

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“…It was shown that a higher injection rate will promote stronger foam generation (Mohd Shafian et al 2015). Rossen et al (1995a) pointed out SAG foam processes can combine high gas injectivity with low mobility at the front of the foam bank, which offers an escape from the dilemma posed by early modeling, i.e., improved vertical sweep of gas with foam requires an increase in injection pressure (Shi et al 1998). Shan and Rossen (2004) proposed an optimal injection strategy for overcoming gravity override with foam in a homogeneous reservoir.…”

Section: Introductionmentioning

confidence: 99%

Understanding aqueous foam with novel CO2-soluble surfactants for controlling CO2 vertical sweep in sandstone reservoirs

Ren

Nguyen

2017

Pet. Sci.

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The ability of a novel nonionic CO 2 -soluble surfactant to propagate foam in porous media was compared with that of a conventional anionic surfactant (aqueous soluble only) through core floods with Berea sandstone cores. Both simultaneous and alternating injections have been tested. The novel foam outperforms the conventional one with respect to faster foam propagation and higher desaturation rate. Furthermore, the novel injection strategy, CO 2 continuous injection with dissolved CO 2 -soluble surfactant, has been tested in the laboratory. Strong foam presented without delay. It is the first time the measured surfactant properties have been used to model foam transport on a field scale to extend our findings with the presence of gravity segregation. Different injection strategies have been tested under both constant rate and pressure constraints. It was showed that novel foam outperforms the conventional one in every scenario with much higher sweep efficiency and injectivity as well as more even pressure redistribution. Also, for this novel foam, it is not necessary that constant pressure injection is better, which has been concluded in previous literature for conventional foam. Furthermore, the novel injection strategy, CO 2 continuous injection with dissolved CO 2 -soluble surfactant, gave the best performance, which could lower the injection and water treatment cost.

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Section: Introductionmentioning

confidence: 99%

Understanding aqueous foam with novel CO2-soluble surfactants for controlling CO2 vertical sweep in sandstone reservoirs

Ren

Nguyen

2017

Pet. Sci.

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Optimal Design Criteria for SAG Foam Processes in Heterogeneous Reservoirs

Kloet

Renkema

Rossen

2009

EUROPEC/EAGE Conference and Exhibition

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Miscible gas injection can displace nearly all of the oil from the portions of the reservoir swept by gas. However, reservoir heterogeneity, low gas density and high gas mobility reduce sweep efficiency and drastically reduce recovery. Foam can reduce gas mobility and the effects of heterogeneity and gravity, and therefore increase sweep efficiency. Here we extend a previous study (SPE 110408) on optimal design strategy for surfactant-alternating-gas (SAG) foam processes in layered reservoirs. We develop design criteria for the optimal foam strength and slug size for a given permeability contrast between layers. We reach the following conclusions: Trends of foam strength with permeability or surfactant formulation, as measured in conventional coreflood tests at fixed injected water fraction, may not correspond to behavior in a SAG process in the field. In the cases examined, foam strength in a SAG process is much less sensitive to permeability and foam parameters than is foam strength at fixed injected water fraction. Placement of surfactant into low-permeability layers is a key challenge of SAG processes in heterogeneous reservoirs. Gas breakthrough occurs via low-permeability layers that did not receive enough surfactant. For that reason, unlike gas injection without foam, having a low-permeability layer at the top of the formation is a disadvantage because it is difficult to place foam there. Using multiple surfactant and gas slugs allows foam to redistribute surfactant in later slugs. However, this strategy suffers from poor injectivity during liquid injection, which slows the process and promotes gravity segregation. Injection of both gas and surfactant slugs at the maximum allowed injection pressure, rather than at fixed rate, gives best results. Injecting gas from only the bottom of the well offers no significant advantages in the best case, where high-permeability layers lie at top and bottom of the reservoir, and performs significantly worse if low-permeability layers lie at the top (where lack of surfactant leads to override) and bottom (where low permeability restricts injectivity) of the reservoir. A surfactant slug sized for a homogeneous reservoir is too large for a heterogeneous reservoir, because little surfactant enters lower-permeability layers: much of the injected surfactant goes to waste. A surfactant slug sized to sweep high-permeability layers and a portion of low-permeability layers performs nearly as well as one sized to sweep the entire reservoir. Introduction Gases, like steam, carbon dioxide, nitrogen or reinjected field gas, have widely been used in the industry as a sweeping agent for the displacement of oil.1,2 Unfortunately, the gas is hampered in its ability to sweep due to density differences to oil and water, high gas mobility and reservoir heterogeneity. Density difference causes the gas to override the oil, leaving significant portions of the reservoir unswept. High mobility of the gas phase as compared to mobilities of water or oil causes viscous instability that significantly worsens the override and, in combination with reservoir heterogeneities, forms high-mobility channels, leading to early gas breakthrough.3 The use of foams can significantly counter these disadvantages by lowering the gas mobility and reducing the effect of layering, therefore avoiding override and increasing sweep efficiency.4,5

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Injectivity and Gravity Override in Surfactant-Alternating-Gas Foam Processes

Cited by 2 publications

References 0 publications

Understanding aqueous foam with novel CO2-soluble surfactants for controlling CO2 vertical sweep in sandstone reservoirs

Understanding aqueous foam with novel CO2-soluble surfactants for controlling CO2 vertical sweep in sandstone reservoirs

Optimal Design Criteria for SAG Foam Processes in Heterogeneous Reservoirs

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