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

Yu, Mengxi; Mahmoud, Mohamed; Nasr‐El‐Din, Hisham A.

doi:10.2118/128047-pa

Cited by 28 publications

(13 citation statements)

References 31 publications

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“…This will help the acid plug the high-permeability zones upon acid spending and divert the fresh acid to the low-permeability zones. Yu et al (2012) studied the effect of hydrolysis on the rheology of VES-based acid systems. Under high temperature and in an acidic environment, the peptide bond is broken and the system is hydrolyzed.…”

Section: Discussionmentioning

confidence: 99%

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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%

“…This resulted in a large decrease in the acid viscosity. Yu et al (2012) shows the VES-based acid-phase separation as a function of hydrolysis time at 190 F for 4-, 6-, and 8-vol% VES concentration (Figs. 3 through 5).…”

Section: Discussionmentioning

confidence: 99%

Recent Advances in Viscoelastic Surfactants for Improved Production From Hydrocarbon Reservoirs

2016

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“…Upon the reaction of acid with carbonates, the pH increases and the concentration of divalent cations in solution increases and therefore the VES-based acid system starts to build viscosity. At pH around 4, the viscosity of the spent acid will be high enough to divert the fresh acid to low permeability un-contacted zones and fresh acid starts to penetrate and react with these rocks to form wormholes (Nasr-El-Din et al 2006b;Crews and Huang 2007;Huang et al 2008b;Yu et al 2011). The viscosity of VES fluids can be reduced upon mixing with hydrocarbons.…”

Section: B Matrix Acidizingmentioning

confidence: 99%

“…Also, they found that the use of internal breaker is very important to break down the remaining VES structure to better clean up the formation after the acid treatment. Yu et al (2011) studied the retention of VES surfactant in the porous media through using coreflood experiments. The VES-based acid system used in their study consisted of 15 wt% HCl, 7 vol% VES and 0.3 vol% corrosion inhibitor.…”

Section: B1 Experimental Studiesmentioning

confidence: 99%

Recent Advances in Viscoelastic Surfactants for Improved Production from Hydrocarbon Reservoirs

Hull

Sayed

Al-Muntasheri

2015

SPE International Symposium on Oilfield Chemistry

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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 theoretical 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 twenty years or so 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 which have demonstrated less damage to the reservoir rock formation. Important advancements in VES have been made by introducing "pseudo-crosslinking agents" such as nanoparticles to enhance the viscosity. Fracturing fluid systems based on VES have also been improved recently by developing internal breakers to lower their viscosity in order 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 carbonated-based reservoirs. The viscosity of these VES-based fluids is mostly controlled by pH where, 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 un-contacted 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 here.In order for VES-based fluids to play a more prominent role in the field, inherent limitations such as cost, applicable temperature range, and leak-off 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, non-damaging alternative to conventional polymer-based fluids.

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“…VES result in a rapid viscosity built up due to the entanglement of these rod-like micelles. VES are being used in the petroleum industry for matrix stimulation and enhanced oil recovery (EOR) (Adejare and Nasralla, 2012;Aoudia et al, 2010;Hull et al, 2016;Kamal et al, 2017a;Yu et al, 2011). Matrix stimulation is often needed in limestone and dolomite reservoirs to generate wormholes.…”

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

Cited by 28 publications

References 31 publications

Recent Advances in Viscoelastic Surfactants for Improved Production From Hydrocarbon Reservoirs

Recent Advances in Viscoelastic Surfactants for Improved Production From Hydrocarbon Reservoirs

Recent Advances in Viscoelastic Surfactants for Improved Production from Hydrocarbon Reservoirs

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

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