The evaluation of oil well cement additives is determined by the influence on the rheological 17 and mechanical properties of the slurry. The use of nanoadditives for cement, such as 18 bacterial nanocellulose (BNC), has been increasing in recent years due to their high tensile 19 strength, high Young's modulus, and thermal resistance. However, the influence of BNC 20 addition on the mechanical properties of the cement is not widely studied. The purpose of 21 this work is to understand the effects caused by the addition of BNC in class G cement 22 during the fresh and hardened states. Free fluid and high-pressure consistometry tests 23 have been carried out in the fresh state. In the hardened state, dynamic thermomechanical 24 analyses (DMA) and uniaxial compressive strength (UCS) tests have been performed. 25Additionally, thermogravimetric analysis (TGA) was carried out to determine the calcium 26 hydroxide content and the hydration degree (DOH). Results indicate that BNC modifies the 27 slurry behavior by reducing the free fluid content and by incrementing consistency. 28 Moreover, the calcium hydroxide content and DOH increase with the addition of BNC. The 29 mechanical properties of BNC-cement samples are increased in terms of storage modulus 30 and mechanical strength. These properties can improve the performance of cement used 31 in cementing operations. 32Re ised man scrip i h no changes marked Keywords 33 Bacterial Nanocellulose -Cementing -Mechanical Performance -Thermal Analysis 34
Introduction 35Oil well cementing is a complex procedure in wellbore operations. The cement must ensure 36 the oil well integrity and prevent links between formations (Al Ramadan et al., 2019; Kiran 37 et al., 2017). The slurry used differs from each particularly well condition, changing its 38 additives and quantities as needed. This cement mixture must meet a series of 39 requirements according to Standards, and it will be subjected to several stress loadings throughout its life span. Different problems arise during these stages, but the low tensile 41 strength and cracks propagation of the set cement (Banthia and Nandakumar, 2003) and 42 its resistance to temperature are essential properties to be optimized, as well as. 43Recently, there has been a growing interest in nanocellulose (Charreau et al., 2012). 44Nanocellulose has a background in reducing micro-cracking (Hisseine et al., 2019(Hisseine et al., , 2018. 45Its addition to cement is very likely to induce an increment in tensile strength and prevent 46 the propagation of cracks caused by external loads. There are three types of nanocellulose 47 according to how is production; microfibrillated nanocellulose (MFC), nanocrystalline 48 cellulose (NCC), and bacterial nanocellulose (BNC). 49 Bacterial nanocellulose is an environmentally friendly material (Muhd Julkapli and Bagheri, 50 2017) produced by several bacteria types in different culture media. In particular, 51Gluconacetobacter xylinus bacteria is one of the primary microbial producers of this 52 material, and ...