Andra Tamas et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 2( Version 1), February 2014, pp.95-101 www.ijera.com 95 | Page Rheological Properties Of Some Surfactant-Based Fracturing Fluids Andra Tamas*, Martin Vincze** And Mirabela Padure* *(Faculty of Industrial Chemistry and Environmental Engineering, University Politehnica Timisoara, Romania, Blv. Vasile Parvan 6) ** (Mopeka Impex Timisoara, Romania) ABSTRACT The paper presents the rheological behavior study of some cationic surfactant-based aqueous solutions that can be used as fracturing fluids. It was followed the influence of salt type and concentration, as well as that of temperature by setting the dependence between the shear stress τ and the shear rate   . The analysis of dependence between τ and   demonstrates that all the studied solutions have non-Newtonian behavior with flow behavior index smaller than 1. Keywords - apparent viscosity, non-Newtonian behavior, surfactant I. INTRODUCTION Hydraulic fracturing is a well stimulation process used to maximize the extraction of underground resources. It refers to the procedure of creating fractures in rocks and rock formations by injecting a fracturing fluid into the cracks to force underground to open further. The main functions of a fracturing fluid are to open the fracture and to transport propping agent along the length of the fracture [1-5]. The ideal fracturing fluid should: be able to transport the propping agent in the fracture, be compatible with the formation rock and fluid, generate enough pressure drop along the fracture to create a wide fracture, minimize friction pressure losses during injection, be formulated using chemical additives that are approved by the local environmental regulations and exhibit controlled- break to a low-viscosity fluid for cleanup after the treatment [6,7]. Many types of fracturing fluids were used in oil field, such as polymer solution, crosslinked polymer, foam, viscoelastic surfactant (VES), combination between a single phase microemulsion and a gelable polymer [1]. To optimise fracture operations that increase porosity in the underground strata around the well, the fracturing fluid’s viscosity must be high enough under low shear conditions to suspend and carry proppant to the smallest crevices in the fractured rock. In addition, its viscosity must be low enough under high shear rates so that adequate flow to these newly fractured strata is obtained and the proppant is released [6]. Surfactant-based fracturing gels are considered as clean gels due to the absence of insoluble residues in their composition. This kind of fluid has been developed to minimize or eliminate damages to fractures [2, 8-10]. The composition of viscoelastic surfactant fluids is fresh water, salt and VES product (typically a quaternary ammonium salt of a long-chain fatty acid). In some cases, an organic counter ion is used to improve the thermal stability of the VES micelle structures. When the aqueous environment contains an optimum concentration of salts (usually potassium or ammonium chloride solutions), the micelles assume a rodlike shape. If the surfactant is present in a sufficient concentration (usually > 1% by volume) the micelles associate with one another. The resulting hindered movement causes the fluid to become both viscous and elastic. If the micelles are disrupted owing to shear, they will quickly reaggregate and recover when shear ceases [6,11]. II. EXPERIMENTAL 2.1. Materials and methods The surfactant used for the preparation of viscoelastic type fluids is of cationic type, with an active substance content of 30%. The main characteristics of this product are given in Table 1. The aqueous surfactant solutions also contain sodium salicylate (NaSal) (1÷5%) and potassium or ammonium chloride (0÷4%). The salts content is chosen so the sum of the percentages of the two types of salt (organic and inorganic) is always 5%. All the salts were purchased from Merck. The samples preparation was done at room temperature (25˚C), by dispersing the cationic surfactant in the aqueous solution containing organic and inorganic salts. It was used a stirrer with RESEARCH ARTICLE OPEN ACCESS