A Novel CO2 Responsive Viscoelastic Surfactant based Clear Fracturing Fluid for High-Temperature Unconventional Reservoir

Abstract Viscoelastic surfactant (VES)-based fracturing fluids can reduce the risk of formation damage when compared with conventional polymer-based fracturing systems. However, many VES systems lose viscoelasticity rapidly under high-temperature conditions, leading to high fluid leakoff and problems in proppant placement. A gemini cationic VES-based system offering thermal stability above 250°F and its efficiency in friction reduction is presented in this paper. Rheology measurements were conducted on viscoelastic cationic gemini surfactant fluids as a function of temperature (70 – 300°F) and surfactant concentration. The length of surfactant alkyl chain was varied to investigate the impact of surfactant chain length on VES fluid viscosity at elevated temperatures. The effect of flow rate on friction reduction capability of the surfactant fluid was measured on a friction flow loop. Foam rheology measurements were conducted to evaluate the VES fluid's ability to maintain high temperature viscosity with reduced surfactant concentration. A gemini cationic surfactant was used to prepare a viscoelastic surfactant system that could maintain viscosity over 50 cP at a shear rate of 100 s−1up to at least 250°F. With this system, viscoelastic gel viscosity was maintained without degradation for over 18 hours at 250°F, and the fluid showed rapid shear recovery throughout. Decreasing the average alkyl chain length on the surfactant reduced the maximum working temperature of the resulting viscoelastic gel and showed the critical influence of surfactant structure on the resulting fluid performance. The presence of elongated, worm-like micelles in the fluid provided polymer-like friction reduction even at low surfactant concentrations, with friction reduction of over 70% observed during pumping (relative to fresh water) up to a critical Reynolds number. Energized fluids could also be formulated with the gemini surfactant to give foam fluids suitable for hydraulic fracturing or wellbore cleanouts. The resulting viscoelastic surfactant foams had viscosities over 50 cP up to at least 300°F with both nitrogen and carbon dioxide as the gas phase. The information presented in this paper is important for various field applications where thermal stability of the treatment fluid is essential. This will hopefully expand the use of VES-based systems as an alternative to conventional polymer systems in oilfield applications where a less damaging viscosified fluid system is required.

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Rheological Characteristics of Viscoelastic Surfactant Fluid Mixed With Silica Nanoparticles

ASME 2013 4th International Conference on Micro/Nanoscale Heat and Mass Transfer ◽

10.1115/mnhmt2013-22047 ◽

2013 ◽

Cited By ~ 1

Author(s):

Yueqiong Wu ◽

Zhongyang Luo ◽

Hong Yin ◽

Tao Wang

Keyword(s):

High Temperature ◽

Shear Rate ◽

Volume Fraction ◽

Sio2 Nanoparticles ◽

Fluid Loss ◽

Rheological Characteristics ◽

High Shear ◽

Fracturing Process ◽

Viscoelastic Surfactant ◽

Rheological Performance

Since the surfactant can form rod-like micelles or even cross-link structures, viscoelastic surfactant (VES) fluid has unique rheological characteristics. The demerits of VES fluids have been proven after being applied as the fracturing fluid for several years. However, the fluid has high fluid loss and a low viscosity at high temperature, which limits the application to hydraulic fracturing. This paper focuses on the VES fluid mixed with nanoparticles which should be an effective way to maintain the viscosity at high temperature and high shear rate. The experiments were based on preparation of uniform and stable nanocolloids, which utilize Microfluidizer high shear fluid processor. Dynamic light scattering and microscopic methods are employed to investigate the stability and micro-structure of the VES fluid. The effects of temperature, shear rate and volume fraction of the nanoparticles on rheology of VES were studied. The SiO2 nanoparticles could significantly improve the rheological performance of VES fluid, although the rheological performance at the temperature over 90 °C needs to be enhanced. The mechanisms of interactions between nanoparticles and micelles are also discussed later in the paper. At the end, the potential of VES fluid mixed with nanoparticles during application in fracturing process was discussed.

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