# Fracturing Fluids and Their Application in the Republic of Croatia
## 5 Fracturing Fluids--Composition and Additives
### Seatawater Fracturing Technology  
Besides developing biodegradable synthetic additives, great attention is given to the development of seawater fracturing technology. Using seawater as a base fluid to design  
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**Fluid Name** & **Fluid Composition** & **Additive Description** & **Purpose of Testing** & **Performed Tests** & **Results** \\ \hline Hybrid dual-polymer hydraulic fracturing fluid & Guar derivative and a polyacrylamide-based synthetic polymer & Emulsion form composed of acrylamide-based 2-acrylamide-acrylic acid, 2-acrylamide-2 acrylamide-2 acid & Maintaining the thermal stability of fracturing fluids (up polymer loading) & By the addition of synthetic polymer to CHMPG, a fluid that is stable up to 176 \({}^{\circ}\)C was generated; a dual-polymer system with lower polymer loading can reduce material cost and damage in the generated fractures. & By the addition of synthetic polymer fracturing fluid has good shear stability, and high-temperature highly-temperature highly-temperature low-permeability & By the addition of synthetic polymer fracturing fluid has good shear stability, and high-temperature highly-temperature high-temperature high-temperature high-temperature low-permeability & By the addition of synthetic polymer fracturing fluid can be used up to 170 \({}^{\circ}\)C. \\ \hline High Elasticity and Low Viscosity (HEV) Fracturing Fluid [63] & - & HELV is a quaternary polymer designed by copolymer copolymer & Fracturing fluid & Viscoelasticity measurements, and alternative for the development of oil and gas resources. & FELV, because of its excellent elasticity, added in the fracturing fluid improved viscosity, proper system capacity and injection. & FELV, because of its excellent elasticity, added in the fracturing fluid improved viscosity, proper system capacity and injection. fracturing fluids has many benefits, but it also presents a big challenge for the petroleum industry because of many requirements which must be met for successful fracturing [65; 66]. Seawater-based fracturing fluids are favorable in offshore applications because of the readily available seawater which can eliminate costly vessel trips for the transportation of fresh water and reduce rig rental time [66] as well as in arid regions, where freshwater is limited and more valuable in other commercial uses [65]. In addition, the development of unconventional deposits such as shale oil and gas deposits by combining multistage hydraulic fracturing and extended reach horizontal drilling requires large quantities of freshwater which could be replaced by saltwater [65]. However, using seawater as a base water to design fracturing fluids requires solving various problems resulting from the high salinity and total dissolved solids (TDS) of seawater and the presence of calcium, magnesium and sulfate ions that cause delayed hydration, alteration of the crosslinking mechanism, fluid instability at high temperatures and high scale formation [65]. Sulfate ions from seawater can react with barium from the formation water to form a barium sulfate scale that causes formation damage and restrictions in the flow through pipes [65; 67]. To effectively mitigate this serious scale problem, a combination of water treatment and chemical scale inhibitor is recommended. Nanofiltration (NF) technology can be successfully applied to water treatment because it specifically removes sulfate ions from water sources with a high sulfate content [67]. A combination of NF technology and sulfonate-based scale inhibitor offers effective scale inhibition for seawater fracturing technology applied in high-temperature formations [67]. [PERSON] et al. (2016) conducted research on the behavior of two different types of viscosifying agent--hydroxypropyl guar (HPG) and carboxymethylhydroxypropyyl guar (CMHPG)--in freshwater and seawater-based fracturing fluids [65].