Acid Fracturing of Deep Gas Wells Using a Surfactant-Based Acid: Long-Term
Effects on Gas Production Rate

Nasr‐El‐Din, Hisham A.; Al-Driweesh, Saad; Bartko, Kirk; AlGhadhban, Hamed; Ramanathan, Venkateshwaran; Kelkar, Shrihari Kishor; Samuel, Mathew

doi:10.2523/102469-ms

Cited by 6 publications

(6 citation statements)

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“…11,14 VES are used in well stimulation to improve oil and gas well productivity because they form high viscous gels which are desirable for well stimulation. [14][15][16] Aer well stimulation, the gels need to be removed from the reservoir in order to resume oil and gas production. VES gels are easily removed from oil reservoirs when compared to polymer gels 14 because reservoir oils reduce their viscosities easily.…”

Section: -8mentioning

confidence: 99%

Understanding viscosity reduction of a long-tail sulfobetaine viscoelastic surfactant by organic compounds

2018

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Though the transition from cylindrical micelles to spherical micelles of the anionic surfactant potassium oleate in the presence of oils has been studied, these changes have not been studied for long-tail zwitterionic surfactants. The effects of n-decane, crude oil (CO), extra virgin olive oil (EVOO) and polyglycolic acid (PGA) on the zero-shear viscosity of an aqueous solution of a sulfobetaine surfactant system were investigated at 30 C and 60 C. The main surfactant in the system was erucamidopropyl hydroxypropyl sulfobetaine. The methods employed were rheology and cryo-TEM. The solution with 3.96 wt% surfactant system and 6.2 wt% CaCl 2 was viscoelastic at both test temperatures due to the formation of entangled cylindrical micelle networks. n-Decane induced the following regimes of zeroshear viscosity change at both temperatures: (i) the high viscosity regime (HVR), (ii) the transition regime (TR), and (iii) the low viscosity regime (LVR). The HVR was characterized by high zero-shear viscosities.The TR was characterized by a sharp drop in zero-shear viscosity due to the formation of untangled micelles. The LVR was due to the formation of microemulsions. The formation of these regimes depended on the balance between micellization and oil solubilization. We reveal for the first time that the number of regimes depends on the type of oil: both CO and EVOO induced only one and two regimes at 30 C and 60 C, respectively. PGA did not significantly affect the solution at either temperature with increasing concentration, meaning the solution was resistant to decreasing pH even at higher temperatures.

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Section: -8mentioning

confidence: 99%

Understanding viscosity reduction of a long-tail sulfobetaine viscoelastic surfactant by organic compounds

2018

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“…The most common hydrocarbon that is used as an external phase is diesel, and its main function is to act as a diffusion barrier between acid and rock (Crowe et al 1974;Bergstrom et al 1975;Hoefner et al 1985;Daccord et al 1989;Peters et al 1989). This diffusion barrier will result in a reduction in acid-rock reaction rate, which will help in the creation of deep wormholes (Williams et al 1972;Guidry et al 1989;Navarrete et al 1998a and b), and creation of etched fracture surfaces (Navarrete et al 1998a and b;Nasr-El-Din et al 2006;Nasr-El-Din et al 2008a). Droplet size distribution and the viscosity of emulsified acid play an important role in the performance of emulsified acid.…”

Section: Introductionmentioning

confidence: 95%

Acid Treatments in High Temperature Dolomitic Carbonate Reservoirs Using Emulsified Acids: A Coreflood Study

Sayed

Nasr‐El‐Din

2013

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Acid treatments in deep wells drilled in carbonate reservoirs represent a challenge to the oil industry. Emulsified acid can be used in matrix acidizing and acid fracturing treatments. The delayed nature of emulsified acid is useful in creating deep wormholes and etched fracture surfaces. The high temperature of deep wells requires a special formulation of emulsified acid that is stable and effective at such high temperatures. The main objective of the present work is to study the performance of emulsified acid in stimulating high temperature deep wells drilled in dolomitic carbonate reservoirs.A coreflood study was conducted using dolomite cores, which had dimensions of 1.5 in. diameter and 6 in. length. The initial permeability of the dolomite cores used in the current study ranged from 1.6 to 20.9 md. Emulsified acid systems were formulated at 0.7 acid volume fraction, 1.0 vol% emulsifier, and 15 wt% HCl concentration. Coreflood experiments were performed at a temperature of 300°F, at injection rates range from 0.5 to 10 cm 3 /min until acid breakthrough the core. Samples of the effluent fluids were collected and analyzed using ICP to measure the calcium and magnesium concentrations. All cores were CAT scanned before acid treatment to study the presence of vugs, and after acid injection to study the characteristics of the generated wormhole.The results show that the emulsified acid created wormholes in dolomite cores, resulting in better treatment outcome. For emulsified acid injection rates in the range from 0.5 to 10 cm 3 /min, the volume of emulsified acid injected to achieve breakthrough increased with the increase in the emulsified acid injection rate. Also, there was no optimum injection rate for the injection rate range studied (0.5 to 10 cm 3 /min). The number and size of the created wormholes was function of the injection rate of emulsified acid. This paper summarizes the results obtained and recommends the use of emulsified acid systems for field applications with dolomite reservoirs.

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“…Viscoelastic surfactants were introduced to replace high-molecular-weight polymers used in some gelled acids as there were concerns of formation damage from the polymers (Lynn and Nasr-El-Din 2001;Nasr-El-Din et al 2006). Surfactantbased acids are extensively used in acid fracturing operations (Al-Muhareb et al 2003;Nasr-El-Din et al 2003b).…”

Section: Introductionmentioning

confidence: 97%

Influence of Acid-Fracture Fluid Properties on Acid-Etched Surfaces and Resulting Fracture Conductivity

2010

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While experimental studies have shown acid type significantly influences resulting fracture conductivity, there has been limited work on how fluid properties relate to etched fracture faces and hence the resulting conductivity. The effects of acid solutions injected into hydraulic fractures created in carbonate formations can be assessed at the laboratory scale in acid fracture conductivity tests that mimic the conditions in an actual acid fracture treatment.Many different acid systems are currently applied in acid fracturing treatments with various degrees of success. However, there is no clear understanding of the mechanisms that lead to success of a treatment. It is clear that acid properties influence and shape the success of an acid fracturing treatment. In order to develop a better methodology for design of acid fracturing treatments, the effect of acid fluid properties on the resulting conductivity and etching must be determined. A series of acid fracture conductivity tests was conducted using four commonly used acid fracturing fluids-gelled, in-situ gelled, emulsified, surfactant-based acid. Detailed rheological properties were measured in order to explain trends noted with conductivity data.Acid system influences the degree of etching and the etching pattern due to differences in chemical and physical properties of acid systems. Under our experimental conditions, viscoelastic acid generated the greatest degree of etching and best etching pattern. Majority of experiments showed differences in conductivity among acid systems tested with most optimal acid system depending on the closure stress. While viscoelastic acid generated the highest conductivity at low closure stress, emulsified acid resulted in the largest retained conductivity at higher loads for our experimental conditions. Furthermore, effluent analysis on both the leakoff and fracture flow showed that most of the fracture face etching is the result of leaked acid into the formation with minimal etching from the fracture flow acid.

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Acid Fracturing of Deep Gas Wells Using a Surfactant-Based Acid: Long-Term Effects on Gas Production Rate

Cited by 6 publications

References 0 publications

Understanding viscosity reduction of a long-tail sulfobetaine viscoelastic surfactant by organic compounds

Understanding viscosity reduction of a long-tail sulfobetaine viscoelastic surfactant by organic compounds

Acid Treatments in High Temperature Dolomitic Carbonate Reservoirs Using Emulsified Acids: A Coreflood Study

Influence of Acid-Fracture Fluid Properties on Acid-Etched Surfaces and Resulting Fracture Conductivity

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