Synthesis and Characterization of Surfactant for Retarding Acid–Rock Reaction Rate in Acid Fracturing

Abstract

Acid fracturing is an effective method to develop ultra-low permeability reservoirs. However, the fast reaction rate reduces the effect of the acid fracturing and increases the near-well collapse risk. Therefore, it is necessary to retard the acid–rock reaction rate. In this work, we synthesized an acid-resistant Gemini zwitterionic viscoelastic surfactant (named VES-c), which has good performances such as temperature resistance, salt resistance, and shear resistance. Besides, a low concentration of VES-c increases the viscosity of the acid solution. The CO2 drainage method was used to measure the reaction rate between the dibasic acid and dolomite/broken core. We find that the dibasic acid containing 0.3% VES-c retards the dolomite reaction rate of 3.22 times compared with only dibasic acid. Furthermore, the dibasic acid containing 0.3% VES-c exhibits uniform distribution and is not easy to adhere to the solid surface. The VES-c also is favorable to reduce the formation of amorphous calcium carbonate. Retarding the rate of acid–rock reaction and enhancing the acidification are mainly attributed to VES-c's salt-tolerance, anti-adsorption, and the property of increasing the viscosity of the solution. Hopefully, this kind of surfactant retarding reaction rate is applied to other acid–rock reactions.

Permeability Enhancement Mechanism of Acidizing in Steam-Assisted Gravity Flooding Wells

“…Therefore, the acid-corroded fractures are perpendicular to the formation and can dissolve upwards or downwards, communicating different layers [19][20][21]. When the intervals with low physical properties exist between the steam injection well and the production well, as shown in Figure 2, they may severely limit the recovery rate by blocking the flow of crude oil whose viscosity is reduced by heat towards the production well [22]. In order to continuously improve the development effect of the SAGD method and achieve economic and effective development of SAGD flooding, there are still large spaces for technological improvement in areas such as breaking through the intervals with low physical properties as soon as possible, continuously expanding the swept volume of the steam chamber, increasing crack conductivity and improving supporting processes.…”

Research and application of acid fracturing stimulation mechanism in ultra-deep subsalt dolomite reservoir in Tarim Basin

“…In addition, the use of encapsulated acid is also an important means to achieve high-efficiency treatment of deep carbonate rocks (Luo et al 2019a, b). Generally speaking, the primary problems of dolomite reservoir treatment include great acid leak-off caused by the development of natural fractures (Fu et al 2019), fast acidrock reaction caused by high reservoir temperature (Rabie et al 2014;Sayed et al 2013), difficult maintenance of conductivity in acid-corroded fractures caused by high Young's modulus, large Poisson's ratio, and high crustal stress (Desouky et al 2020;Mehrjoo et al 2022), poor conductivity caused by uniform etching of dolomite with high purity (Zhang et al 2020), difficult vertical effective operation caused by numerous vertical small layers and thick reservoirs, and difficult fracture caused by great fracture pressure gradient of the reservoir (Yan et al 2021a). Therefore, the corresponding treatment measures were proposed as follows: liquid thickening (Luo et al 2021), leak-off suppression with solid particles (Pankov et al 2012), pre-flush fluid cooling (Lei et al 2018;Zhang et al 2022), large-displacement treatment (Han et al 2017), closed acidification (Aljawad et al 2019), sand-acid fracturing (Zhang et al 2021), diversion acid fracturing (Rabie et al 2012), and so on.…”