Improved Prediction of Foam Diversion in Matrix Acidization

Zeilinger, S.C.; Wang, M.; Kibodeaux, K.; Rossen, W.

doi:10.2523/29529-ms

Cited by 4 publications

(6 citation statements)

References 1 publication

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“…Water injection following foam generations in single core experiments have also been investigated and discussed by several others (e.g., Aarra et al, 2011;Bernard et al, 1965Bernard et al, , 1980Bhide et al, 2005;Du et al, 2007;Kibodeaux, 1997;Nguyen et al, 2009;Parlar et al, 1995;Seright, 1996;Zeilinger et al, 1995). Their findings and observations relative to our results deserve comments and discussions.…”

Section: Summary and Discussionsupporting

confidence: 65%

“…Foams can also reduce water flow. Several authors indicate that foams can survive in laboratory corefloods, at least in a weakened form, against several pore volumes of liquid injected (Aarra et al, 2011;Bernard et al, 1965Bernard et al, , 1980Bhide et al, 2005;Du et al, 2007;Nguyen et al 2009;Parlar et al, 1995;Seright, 1996;Zeilinger et al, 1995). Reduced foam stability to subsequent liquid injections has been discussed in terms of surfactant dilution, gas expansion and gas dissolution into the injected liquid phase.…”

Section: Water Blocking Abilitiesmentioning

confidence: 99%

“…Several authors have also suggested that gas dissolution could have significant effects on the foam stability in porous media against subsequent water injection after foam generation (Bhide et al, 2005;Nguyen et al, 2009;Zeilinger et al, 1995). Comparative studies indicate that the CO 2 -foams are less effective to reduce water flow compared with foams having gas components with low solubility in water (e.g., air/N 2 and CH 4 ) (Aarra et al, 2011(Aarra et al, , 2014Seright, 1996).…”

Section: Gas/water Solubilitymentioning

confidence: 99%

“…N 2 -foams: Certain N 2 -foams in the literature have been extraordinarily strong, reflected by very large pressure gradients along the porous media, which are often >> 50 bar/m (Chou, 1991;de Vires and Wit, 1990;Friedmann et al, 1991;Kovscek and Radke, 1994;Vikingstad and Aarra, 2009;Solbakken et al, 2014;Siddiqui et al, 1997a;Zeilinger et al 1995).…”

Section: Introductionmentioning

confidence: 99%

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Properties of N2- and CO2-foams as a function of pressure

Aarra

Skauge

Solbakken

et al. 2014

Journal of Petroleum Science and Engineering

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The last ~4.5 years have been the most exciting and challenging period in my life so far. I want to use this opportunity to thank at least some of the people who have supported me in one way or another during this period. I wish to express my gratitude to my supervisor Dr. Morten G. Aarra; thank you for sharing your knowledge with me, for your personal encouragement, and for the many good discussions. My co-supervisor, Professor Arne Skauge, deserves a special thank as well; thank you for scientific advice and assistance throughout the work, for giving me the opportunity to participate as a Master and PhD student at Uni CIPR, and for offering me a permanent position thereafter. Acknowledge goes to Hege Ommedal for her support as PhD-coordinator at the department of Chemistry. I am also thankful to other past and present colleagues at Uni CIPR who have made this time

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Section: Summary and Discussionsupporting

confidence: 65%

Section: Water Blocking Abilitiesmentioning

confidence: 99%

Section: Gas/water Solubilitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Properties of N2- and CO2-foams as a function of pressure

Aarra

Skauge

Solbakken

et al. 2014

Journal of Petroleum Science and Engineering

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“…Most of the literature specifically on liquid injectivity following foam is related to matrix acid diversion (Kibodeaux et al 1994;Zeilinger et al 1995;Nguyen et al 2003;Nguyen et al 2009). The objective in an acid stimulation process is to maintain low water relative permeability and reduce liquid injectivity to the greatest extent possible.…”

Section: Introductionmentioning

confidence: 99%

Laboratory Investigation of Liquid Injectivity in Surfactant-Alternating-Gas Foam Enhanced Oil Recovery

et al. 2019

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Surfactant-alternating-gas (SAG) is a favored method of foam injection, in part because of excellent gas injectivity. However, liquid injectivity is usually very poor in SAG. We report a core-flood study of liquid injectivity under conditions like those near an injection well in SAG application in the field, i.e., after a prolonged period of gas injection following foam. We inject foam [gas (nitrogen) and surfactant solution] into a 17-cm-long Berea core at temperature of 90°C with 40 bar back pressure. Pressure differences are measured and supplemented with CT scans to relate water saturation to mobilities. Liquid injectivity directly following foam is very poor. During prolonged gas injection following foam, a collapsed-foam region forms near the inlet and slowly propagates downstream, in which water saturation is reduced. This decline in liquid saturation reflects in part liquid evaporation, also pressure-driven flow and capillary effects on the core scale. In the collapsed-foam region, liquid mobility during subsequent liquid injection is much greater than downstream, and liquid sweeps the entire core cross section rather than a single finger. Mobility in the region of liquid fingering is insensitive to the quality of foam injected before gas and the duration of the period of gas injection. This implies that at the start of liquid injection in a SAG process in the field, there is a small region very near the well, crucial to injectivity, substantially different from that further out, and not described by current foam models. The results can guide the development of a model for liquid injectivity based on radial propagation of the various banks seen in the experiments.

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Laboratory Study of Gas Trapping in Foam-Acid Diversion

Xü

Rossen

2003

SPE Annual Technical Conference and Exhibition

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A series of Berea coreflood experiments modeled the process of foam-acid diversion for well stimulation. Foam was injected to steady state, followed by injection of liquid to represent acid. Pressure gradient was monitored along the core and average liquid saturation was determined by weighing the core continuously during the experiments. This approach provides direct data on liquid saturation and liquid relative permeability during foam injection and liquid injection after foam. Water saturation increased by a larger amount during post-foam liquid injection than estimated in previous studies. The liquid relative-permeability function krw(Sw) obtained during foam injection was reasonably accurate during post-foam liquid injection, until gas dissolution into the injected liquid became significant. The ultimate trapped-gas saturation during liquid injection appears to depend on previously injected foam quality; this may require a revision of models for the acid-diversion process. It appears that a sufficiently high foam quality (injected gas fraction) can eliminate the detrimental decline in pressure gradient observed during liquid injection in earlier studies. This may alter previous ideas about the optimal foam quality for foam-acid diversion. Introduction Matrix Acidizing Process. Foams have been used routinely in matrix acidizing treatments in the petroleum industry, but with inconsistent results.1–7 Matrix acidizing is a treatment for damaged sandstone or carbonate formations. Formation damage can be caused by drilling, completion, workover, or production processes. A damaged formation has plugged or constricted pore spaces, reduced permeability and reduced productivity. In an acidizing process, acid is used to dissolve material in the matrix, thus increase porosity, permeability and productivity. A formation may have layers with different porosity, permeability and rock types. Layers may also differ in degree of damage. In matrix acidizing, all damaged layers need to be treated, especially the most damaged layers. However, fluid naturally flows into the most-permeable, least-damaged layers, and may leave less-permeable and more-damaged layers under-treated. To solve this problem, foam is used to partially block the high-permeability and undamaged layers and divert acid into the less-permeable layers. Foam for Acid Diversion There are several designs for foam acidizing processes. In particular, one may pre-flush the formation with surfactant, inject foam, and then inject foam-compatible acid. A foam-compatible acid must also contain surfactant to stabilize the foam.8 Multiple slugs of foam and acid may be used. Or, instead, one may inject a surfactant pre-flush followed by continuous injection of foamed acid. This study focuses on the first process, i.e. injecting foam followed by acid. Many studies9–14 agree that foam does not alter water (or acid) viscosity or the relation between water relative permeability krw and water saturation Sw in steady foam flow. Foam does directly reduce gas mobility, thus indirectly reducing water saturation, relative permeability and mobility. Foam reduces gas mobility in part by trapping a large percentage of gas in place; up to 80–99% of gas is trapped even if foam flows at high pressure gradient.14,15 Foam reduces gas mobility also by increasing the effective viscosity of flowing gas.16–19 These two effects are related: both depend on capillary forces that give foam an apparent yield stress and trap bubbles in place.19–23 The presence of foam in a high-permeability or undamaged layers reduces liquid saturation there, reducing relative permeability of liquid krw(Sw), and thus reducing acid flow into the foam-saturated layers. On the other hand, foam is less stable in low-permeability layers.24,25 Therefore it is possible to block high-permeability zones preferentially during foam injection, and maintain foam there during acid injection. At the same time, only weaker foam is present in low-permeability or damaged zones. Acid can then be diverted into the lower-permeability or damaged zones without zonal isolation. Use of a surfactant pre-flush also increases diversion by helping to place more foam in high-permeability or undamaged layers.8

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Improved Prediction of Foam Diversion in Matrix Acidization

Cited by 4 publications

References 1 publication

Properties of N2- and CO2-foams as a function of pressure

Properties of N2- and CO2-foams as a function of pressure

Laboratory Investigation of Liquid Injectivity in Surfactant-Alternating-Gas Foam Enhanced Oil Recovery

Laboratory Study of Gas Trapping in Foam-Acid Diversion

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