Abstract
Hydraulic fracturing is often used in unconventional shale reservoirs, and 50%–95% of the injected hydraulic fracturing fluid remains in the formation due to the capillary effect. This phenomenon has been observed in the Montney shale formation, Canada, where the flowback water recovery is generally less than 25%. Surfactant is one of the hydraulic fracturing fluid additives for reducing surface tension and capillary forces to facilitate water flowback recovery. Surfactant loss due to adsorption by the reservoir rocks reduces the chemical’s efficiency, and this causes water retention in the formation and reduces water flowback recovery. The compatibility of surfactant with reservoir rock is critical to minimize surfactant adsorption on the rock surface because this diminishes the primary function of the surfactant hydraulic fracturing fluid additive and to ensure cost-effectiveness. This study evaluates surfactant efficiency to improve flowback recovery for the Montney shale formation based on IFT, surface tension, and adsorption. This study evaluates surfactant performance and performs a fluid–fluid interaction experiment and fluid-rock compatibility investigation. Several commercial surfactants are screened for low interfacial tension and surface tension. Further analysis is carried out by evaluating the fluid-rock compatibility using the static soaking test at reservoir pressure and temperature. The pre-soaking and post-soaking test fluids were analyzed for water composition, liquid–liquid interfacial tension, surface tension, and pH. Results showed that the selected surfactant is a critical determiner of the hydraulic fracturing fluid performance. SOLOTERRA 938 is an anionic surfactant that has good compatibility with Montney shale formation. Unlike other non-ionic surfactants, SOLOTERRA 938 retains the interfacial tension and surface tension after seven days of interaction with reservoir rock. The interfacial tension remained unchanged at 0.1 mN/m. The surface tension decreased from 28.4 to 27.5 mN/m with air and from 21.7 to 20.8 mN/m with hydrocarbon because surfactant behavior changes with pH change. The surfactant concentration was measured using high-pressure liquid chromatography, and the loss was 12% after seven days of interaction with the reservoir rock (from 0.1 to 0.088wt%). The adsorption calculated based on the concentration volume showed a low value of between 0.43 and 0.97 mg/g rock.
Highlights
The hydraulic fracturing technique was first used in 1947 in the Hugoton field, Kansas (Barati and Liang 2014)
The hydraulic fracturing fluid injected into a shale gas reservoir consists of a hydraulic fracturing base fluid, proppant, and a mixture of low concentration chemical additives such as a surfactant, friction reducer, biocide, breaker, iron control, and scale inhibitor (Ferrer and Thurman 2015)
Surfactant is used as fracturing fluid additive to reduce surface tension, lower the capillary forces to facilitate the recovery of the injected fluid, alter wettability, and reduce flow friction (Penny et al 2005; Kaufman et al 2008; Fichter et al 2010; Ferrer and Thurman 2015; Mirchi et al 2015; Yue et al 2016; Chai et al 2019; Rabie et at. 2019)
Summary
The hydraulic fracturing technique was first used in 1947 in the Hugoton field, Kansas (Barati and Liang 2014). Surfactant is used as fracturing fluid additive to reduce surface tension, lower the capillary forces to facilitate the recovery of the injected fluid, alter wettability, and reduce flow friction The hydraulic fracturing fluid that remained in the formation may cause water blockage and reduce well productivity (Rabie et al 2019). Lu et al (2018) reported that the main reason for hydraulic fracturing fluids retention in the formation and reduced water recovery was surfactant adsorption on the newly fractured micro-fracture surfaces. Three types of viscoelastic surfactants are used in hydraulic fracturing fluids, cationic, anionic, and non-ionic surfactants. The screened surfactants selected for this study, SOLOTERRA 938, GlucoPure Wet, and Aspiro S2420X, are of the anionic and non-ionic types
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
