Internal Phase Breaker Technology for Viscoelastic Surfactant Gelled Fluids

Crews, James B.

doi:10.2118/93449-ms

Cited by 35 publications

(8 citation statements)

References 10 publications

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“…The unsaturated fatty acids are described as auto-oxidizing into ketones, aldehydes, and saturated fatty acids that break the VES fluid. Similarly, addition of specific types of bacteria such as Enterobacter cloacae, Pseudomonas fluorescens, and Pseudomonas aeruginosa have been observed to reduce the viscosity of amine oxide surfactants such as TAPAO (Crews 2006). The mechanism for breaking may follow one of two pathways: the VES micellar structure is directly rearranged or disaggregated or, alternatively, other materials in the viscosified fluid may be degraded to form byproducts that reduce the viscosity of the gel.…”

Section: Discussionmentioning

confidence: 99%

Recent Advances in Viscoelastic Surfactants for Improved Production From Hydrocarbon Reservoirs

2016

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Viscoelastic surfactants (VES) are used in upstream oil and gas applications, particularly hydraulic fracturing and matrix acidizing. A description of surfactant types is introduced along with a description of how they assemble into micelles, what sizes and shapes of micelles can be formed under different conditions, and finally how specific structures can lead to bulk viscoelastic-solution properties. This theoretical discussion leads into a description of the specific VES systems that have been used over the last 20 years in improved oil recovery for upstream applications.VES-based fluids have been used most extensively for hydraulic fracturing. They are preferred over conventional polymer-based fracturing-fluid systems because they are essentially solids-free systems that have demonstrated less damage to the reservoir-rock formation. In fact, approximately 10% of the fracturing treatments use VES-based fluids. Important advancements in VESs have been made by introducing "pseudocrosslinking agents," such as nanoparticles, to enhance the viscosity. Fracturing-fluid systems modeled after VES have also been improved recently by developing internal breakers to lower their viscosity to flow back the well. The flexibility of VES-based fluids has been demonstrated by their application as foamed fluids, as well as their incorporation with brine systems such as produced water.A second key area that has benefited from VES-based systems is matrix acidizing of carbonate-based reservoirs. The viscosity of these VES-based fluids is mostly controlled by pH; at low pH (low viscosity), the acid system flows easily and invades pore spaces in the formation. During acidizing, the acid is spent, and the pH and viscosity increase. Because the spent acid has higher viscosity, fresh acid is diverted to low-permeability, uncontacted zones and penetrates the rocks to form wormholes. A number of experimental studies and field applications to these effects have been performed and will be described in this study.In order for VES-based fluids to play a more-prominent role in the field, inherent limitations such as cost, applicable temperature range, and leakoff characteristics will need to continue to be addressed. If we can efficiently and economically overcome these issues, VES-based fluids offer the industry an excellent clean and nondamaging alternative to conventional polymer-based fluids.

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Section: Discussionmentioning

confidence: 99%

Recent Advances in Viscoelastic Surfactants for Improved Production From Hydrocarbon Reservoirs

2016

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“…9 is that the amount of surfactant retained in the core following acid treatment was significant. This means that there is a need to use external (mutual solvent) or internal breakers (Crews 2005;Crews and Huang 2007) to reduce surfactant retention, especially if a surfactant-based acid is used in a power-water injector or a dry-gas well. …”

Section: Surfactant Retention As a Function Of Acid-injection Ratementioning

confidence: 99%

“…This is exactly what Mohamed et al (2002) noted in the field. Another solution is to use internal breakers to remove the surfactant (Crews 2005;Crews and Huang 2007).…”

Section: Effect Of Mutual Solvent On the Amount Of Surfactant Retainedmentioning

confidence: 99%

Propagation and Retention of Viscoelastic Surfactants Following Matrix-Acidizing Treatments in Carbonate Cores

Mahmoud

Nasr‐El‐Din

2011

SPE Journal

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Viscoelastic surfactants have been used extensively in the field. They have the ability to form long rod-like micelles with an increase in pH and calcium concentration, which results in increasing the viscosity and elasticity of partially spent acids. There is ongoing debate in the industry about whether the gel generated by these surfactants causes formation damage, especially in dry-gas wells. The objectives of the present study are to quantitatively determine surfactant retention in calcite cores and assess the benefits of using mutual solvents to break the surfactant gel formed inside the cores.Coreflood tests were performed using Pink Desert limestone cores (1.5 in. in diameter and 20 in. in length). The cores were injected with a surfactant-based acid that contained 15 wt% HCl, 7 vol% viscoelastic surfactant, and 0.3 vol% corrosion inhibitor. Coreflood tests were conducted at a constant injection flow rate ranging from 1.5 to 40 cm 3 /min. Surfactant and calcium concentrations were measured in the injected acid and core effluent. Mutual solvent (ethylene glycol monobutyl ether) was used in several tests to break surfactant gel.Propagation of viscoelastic surfactants in linear calcite cores was found to be a function of flow rate. Surfactant lagged calcium in the core effluent samples, especially at low flow rates. The volume of acid needed to break through the core and the amount of surfactant retained varied with acid injection rate, and exhibited a minimum at 10 cm 3 /min. A significant amount of surfactant was retained in the cores. Injection of 2 pore volumes (PV) of 10 vol% mutual solvent removed only 20% of the surfactant injected. Based on these results, there is a need to use internal breakers when surfactant-based acids are used in dry-gas wells or water injectors.

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“…Internal breakers that work by micelle rearrangement generate VES-breaking compounds over time, which penetrate and collapse the viscous, rod-like VES micelles into nonviscous, more-spherical micelles (Crews, 2005;Crews and Huang, 2007). VES fluid has been considered by many to effectively break by two methods: contact with reservoir hydrocarbons or contact and dilution with reservoir brine.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Different Brine Solutions on the Viscosity of VES Micelles

et al. 2013

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Viscoelastic surfactants can provide viscoelastic properties in brines at high temperatures (higher than 230°F). Recent studies have shown the advantages of use nanoparticles in VES fluid systems. The nanoparticles have large surface area as well as unique surface morphology and surface reactivity. They can strengthen the micelle-micelle interactions. A small concentration of these particles can maintain viscosity at higher temperatures (up to 300°F) and decrease the rate of VES fluid leakoff (Huang, Crews and Willingham, 2008).The viscoelasticity of nanoparticle-networked VES fluid systems was analyzed with a HP/HT viscometer. A series of rheology experiments have been performed by using 4 vol% amidoamine oxide surfactant in KCl, NaCl and CaBr 2 brines at temperatures up to 275°F and a shear rate of 10 s -1 . The nanoparticles evaluated were MgO and ZnO at the concentration of 6 pptg. In addition, the effect of different nanoparticle concentrations (0.5 to 10 pptg) on the viscosity of VES fluid was investigated. The oscillatory shear rate sweep (100 to 1 s -1 ) was performed from 100 to 200°F. The effect of an internal breaker on the viscosity of VES micelles was examined.

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Internal Phase Breaker Technology for Viscoelastic Surfactant Gelled Fluids

Cited by 35 publications

References 10 publications

Recent Advances in Viscoelastic Surfactants for Improved Production From Hydrocarbon Reservoirs

Recent Advances in Viscoelastic Surfactants for Improved Production From Hydrocarbon Reservoirs

Propagation and Retention of Viscoelastic Surfactants Following Matrix-Acidizing Treatments in Carbonate Cores

The Effect of Different Brine Solutions on the Viscosity of VES Micelles

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