Nondamaging Viscoelastic Surfactant-Based Fluids Used for Acid Fracturing Treatments in Veracruz Basin, Mexico

Artola, Pedro; Alvarado, Oscar; Huidobro, Efrain; Salmoran, Angel

doi:10.2118/86489-ms

Cited by 10 publications

(4 citation statements)

References 16 publications

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“…This problem is avoided by using mechanical or chemical diverting agents. Chemical diverting agents are high‐viscosity gel‐like materials that can reduce the acid loss in the wormholes and divert the acid to low‐injectivity zones (Al‐Muhareb et al, ; Artola et al, ; Fogang et al, ; Taylor et al, ). After completion of the stimulation process, the viscous gel can be broken down by using internal and/or external breakers.…”

Section: Introductionmentioning

confidence: 99%

Effects of Rheological Behavior of Viscoelastic Surfactants on Formation Damage in Carbonate Rocks

Kamal

Mahmoud

Hanfi

2018

J Surfact & Detergents

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Viscoelastic surfactants (VES) are used in various oilfield applications such as matrix stimulation and enhanced oil recovery. The loss of surfactants during the propagation of VES could result in a significant reduction in the permeability of the rock (formation damage). The objective of the current work was to identify the effect of rheological behavior of the VES on the formation damage using core‐flooding experiments, nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM) analysis. A combination of core‐flooding, NMR, and SEM techniques was used to quantify and identify the location of formation damage in carbonate core samples. The viscosity and storage modulus strongly depend on the nature and concentration of salts. The viscosity increased by increasing the salt concentration up to a specific point (15 wt% CaCl2) and then starts decreasing. The VES formulations that displayed the maximum and minimum viscosities were used to identify the impact of rheological behavior on formation damage. Core‐flooding experiments were performed to assess the formation damage due to high‐viscosity and low‐viscosity VES formulations. The reduction in the permeability of carbonate rocks reaches more than 90% of the initial permeability. It was found that low‐viscosity VES caused more damage compared with high‐viscosity VES when they were used at constant concentrations. NMR and core‐flooding results revealed that the damage took place both in pore body and pore throat. However, most of the surfactant was retained at the pore throat.

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Section: Introductionmentioning

confidence: 99%

Effects of Rheological Behavior of Viscoelastic Surfactants on Formation Damage in Carbonate Rocks

Kamal

Mahmoud

Hanfi

2018

J Surfact & Detergents

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“…In the recent decade, viscoelastic surfactants have been widely and successfully used in acidizing Zeiler et al 2004), acid fracturing Al-Muhareb et al 2003;Artola et al 2004;Bustos et al 2007;Fontana et al 2007;Bulat et al 2008), and hydraulic fracturing jobs (Samuel et al 1997). Usually, polymer-based acid systems will cause high friction pressures and formation damage because of residue precipitation, breakers are needed to enhance polymer degradation and make the flow back easier, and the cleanup time is lengthy.…”

Section: Introductionmentioning

confidence: 99%

Hydrolysis Effect on the Properties of a New Class of Viscoelastic Surfactant-Based Acid and Damage Caused by the Hydrolysis Products

Wang

Nasr‐El‐Din

et al. 2013

All Days

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Viscoelastic surfactants (VES) have been widely used in acidizing and acid fracturing. They are used as diversion agents during matrix acid treatments and leakoff control agents during acid fracturing. At high temperatures, viscoelastic surfactants hydrolyze, resulting in phase separation after a certain time. Their viscosities significantly decrease and it is much easier for them to flow back and this causes much less damage to the formation.In this study, 4 to 8 wt% of a new VES-acid system were tested at temperature up to 250°F over hydrolysis times of 0 to 6 hours. Then the solutions were neutralized by calcium carbonate until pH reached 4.5. An HP/HT rheometer was used to measure the viscosity of the spent acids. Mass spectrometry (MS) was conducted to analyze the hydrolysis products of the VES. Coreflood tests were also conducted on Indiana limestone to determine the effect of the hydrolysis products on the permeability of these cores. Temperature was set at 250°F and flow rate at 2.5 cm 3 /s.The viscosities of all VES-acid systems remained high at the beginning of hydrolysis, which was good for acid diversion. After that, the VES acid systems experienced significant viscosity reduction because of phase separation; it became much easier for the spent acid to flow back. Coreflood experiments showed little damage caused to the Indiana limestone. MS results indicated that hydrolysis was achieved through the peptide bond. Fatty acids formed the top oil layer and amine-based molecules formed the aqueous phase. This paper will summarize and discuss the details of viscosity changes of the acid systems of this kind of viscoelastic surfactant, the damage caused by the hydrolysis products, and how this kind of viscoelastic surfactant can be used to improve the treatments.

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“…In recent years, viscoelastic surfactants have been successfully applied in oilfield acid fracturing fluids (Al-Muhareb et al 2003;Artola et al 2004;Bustos et al 2007;Fontana et al 2007;Bulat et al 2008), fluidloss pills ) and matrix-acidizing fluids Al-Mutawa et al 2005;Zeiler et al 2006;Liu et al 2009;Nasr-El-Din et al 2009a, b). VES-based fluids were used in these applications because, first, they can serve as substitutes to polymers as fluid viscosifiers.…”

Section: Introductionmentioning

confidence: 99%

Impact of Hydrolysis at High Temperatures on the Apparent Viscosity of Carboxybetaine Viscoelastic Surfactant-Based Acid: Experimental and Molecular Dynamics Simulation Studies

Yan

Wang

et al. 2012

SPE Journal

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Carboxybetaine viscoelastic surfactants have been applied in acid diversion and fracturing treatments in which high temperatures and low pH are usually involved. These surfactants are subjected to hydrolysis under such conditions because of the existence of a peptide group (-CO-NH-) in their molecules, leading to changes in the rheological properties of the acid. The objective of this paper is to study the impact of hydrolysis at high temperatures on the apparent viscosity of carboxybetaine viscoelastic surfactantbased acids, and propose the mechanism of viscosity changes by molecular dynamics (MD) simulations.Surfactant-acid solutions with different compositions (surfactant concentration varied from 4 to 8 wt%) were incubated at 190 F for 1 to 6 hours. Solutions were then partially spent by CaCO 3 until the sample pH was 4.5, and the apparent viscosity was measured using a high-temperature/high-pressure (HT/HP) viscometer. To understand the mechanism for viscosity changes on the molecular level, MD simulations were carried out on spent surfactant-acid aqueous systems using the Materials Studio 5.0 Package.It was found that short-time hydrolysis at high temperatures (for example, 1 to 2 hours at 190 F) led to a significant increase in surfactant-acid viscosity. However, after incubation for 3 hours, phase separation occurred and the acid lost its viscosity. Simulation results showed that viscosity changes of amido-carboxybetaine surfactant acid by hydrolysis at high temperatures may be caused by different micellar structures formed by carboxybetaine and fatty acid soap, its hydrolysis product. The optimum molar ratio of amido-carboxybetaine and fatty acid soap to form wormlike micelles was found to be nearly 3:1 from our simulations.Our results indicate that hydrolysis at high temperatures has a great impact on surfactant-acid rheological properties. Short time viscosity build-up and effective gel breakdown can be achieved if surfactant-acid treatments are carefully designed; otherwise, unexpected viscosity reduction and phase separation may occur, which will affect the outcome of acid treatments.

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Nondamaging Viscoelastic Surfactant-Based Fluids Used for Acid Fracturing Treatments in Veracruz Basin, Mexico

Cited by 10 publications

References 16 publications

Effects of Rheological Behavior of Viscoelastic Surfactants on Formation Damage in Carbonate Rocks

Effects of Rheological Behavior of Viscoelastic Surfactants on Formation Damage in Carbonate Rocks

Hydrolysis Effect on the Properties of a New Class of Viscoelastic Surfactant-Based Acid and Damage Caused by the Hydrolysis Products

Impact of Hydrolysis at High Temperatures on the Apparent Viscosity of Carboxybetaine Viscoelastic Surfactant-Based Acid: Experimental and Molecular Dynamics Simulation Studies

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