A Novel Co2 Responsive Viscoelastic Surfactant Based Clear Fracturing Fluid For High-Temperature Unconventional Reservoir

An unconventional reservoir is a term to describe a hydrocarbon resource that could not be technically or economically recoverable without stimulation. Unconventional oil and gas resources are 4-5 times over conventional oil and gas resources. Currently, there is a limitation for using slick-water volume fracturing and gas (water) injection adding energy for drainage and displacement individually. Also, the efficient hydrocarbons production from the high-temperature unconventional reservoir is the main challenge. In the current study, a CO2 based viscoelastic surfactant fracturing fluid with a specific molar ratio of erucic acid, 2,6,10-trimethyl-2,6,10-triazaundecane, potassium hydroxide, and carbon dioxide (EA-TMTADKOH-CO2) was developed as a good candidate for high-temperature and water alternating treatment for high-temperature unconventional reservoirs. The fracturing fluid will play the role of "one with multi-purpose" by proppant-carrying, CO2 energy supplementary displacement, and surfactant imbibition drainage displacement. The fracturing fluid (EA-TMTAD-KOH-CO2) performance evaluation method for determination of shear and heat resistance, viscoelasticity, proppant carrying capacity, gel breaking ability, and salt tolerance is employed as evaluation indices by using HTHP rheometer. The rheological results of steady shear viscosity of the fracturing fluid system confirm that the EA-TMTAD-KOH-CO2 was observed in the properties of a wormlike micelles (WLMs) structure, micelles assembly, and the intermolecular interactions. The steady shear viscosity above 41 mPa.s at a shear rate of 170 s- 1 and temperature 95 degrees C validates the excellent proppant carrying capacity as per national industry standards of the fracturing process. Further, the gel structure breaking at temperature 135 degrees C and 170 s(-1) bear the shear viscosity less than 5 mPa.s, which results in a rapid flow back from the well after the fracturing process. Moreover, the fluid system has high salt tolerance against different inorganic salts such as NaCl, KCl, CaCl2, and MgCl2 using different concentrations. By retaining the desirable qualities such as; easy to prepare, environment friendly, commercially available, high in viscoelasticity, and thermally stable; the fracturing fluid system (EA-TMTAD-KOH-CO2) will be an outstanding candidate in industrial applications like water-alternating and high-temperature unconventional reservoirs.