The International Journal of Engineering and Science (IJES) || Volume || 7 || Issue || 7 Ver. I|| Pages || PP 57-62 || 2018 || ISSN (e): 2319 – 1813 ISSN (p): 23-19 – 1805 DOI:10.9790/1813-0707015762 www.theijes.com Page 57 Tensile Strength of Oil-Well Cement Pastes Produced with Carbon Nanotubes Directly Synthesized on Clinker Paula, J. N 1 , Calixto, J. M, 2 Ladeira, L. O, 3 Ludvig, P 4 , Souza, T. C. C 5 1 Department of Civil Engineering, CEFET-MG, Brazil 2 Department of Structure Engineering, UFMG, Brazil 3 Department of Physics, UFMG, Brazil 4 Department of Civil Engineering, CEFET – MG, Brazil 5 CTNANO-Brazil Corresponding Author: Paula, J. N --------------------------------------------------------ABSTRACT-------------------------------------------------------------- This paper analyzes the influence of carbon nanotubes (CNTs) in the tensile strength of cement slurries used in oil wells. CNTs were directly synthesized on cement clinker by chemical vapor deposition process. Cement slurries containing 0.1% and 0.3% of CNTs bwoc were compared with CNT-free slurries. Polynaphtalene sulfonated (0.2% bwoc) was used as dispersant in all cement slurries. Tensile strength was evaluated at the age of 28 days. The results show the presence of CNTs in the cement slurries increases the tensile strength in approximately 65% for 0.1% CNT bwoc at age of 28 days. KEYWORDS - carbon nanotubes, cement paste, tensile strength, oil wells. -------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 22-06-2018 Date of acceptance: 07-07-2018 ------------------------------------------------------------------------------------------------------------------------------------- I. INTRODUCTION Well cementing is one of the most important operations performed in oil or gas wells. During cementing procedures, a suspension consisting in water, cement and performance controlling chemicals is pumped down into the well and placed at the interval between the case and the rock formation and left to cure. The purpose of this operation is to anchor the casing to the formation and to achieve the zonal isolation down in the well. The anchoring of the casing is usually achieved but the challenger is to obtain a complete zonal isolation [1]. Discoveries of new reserves in adverse conditions of exploration and the need to recover mature wells may create severe temperature and pressure conditions during cementing procedures. Therefore, flaws in well cementing have increased and required a greater number of interventions during production. They increase production costs and may affect the environment [2, 3]. The high temperature and pressure within an oil well often requires a particularly resilient cement system and the use of a number of high tech chemical admixtures to help ensure adequate zonal isolation [4]. With regard to the desired mechanical properties in oil wells cements, the Young’s modulus should be a low is possible, while the tensile strength of cement should be as high is possible. Conventional Portland cement slurries have a tensile- to - compressive strength ratio of approximately 10%. If this ratio were to be increase as high is possible, the life of cement sheath in a given well would been extended. Mechanical property enhancements would not be complete without tensile strength gain. This is the one of reasons for the investigation of carbon nanotubes (CNTs) cement composites. CNTs have been reported to yield a significant enhancement of tensile properties in cements [5]. Carbon nanotubes are graphene sheets rolled up to form cylinders tubes. A single walled CNT looks like a single sheet rolled up into a tube, while multiwall CNTS look like multiple sheets rolled in to a series of tube, one inside the order [6]. According to [5], CNTs behave as one-dimensional material. In addition, they present tensile strength and Young’s modulus values ten times greater than steel and a density five times smaller [7, 8, 3]. Consequently, CNTs have very high aspect ratios (length/diameter ratio) and can be distributed widely and densely at the microscopic scale yet covering longer lengths. These characteristics can be used in cement composites to bridge cracks and restrict them from increasing which can essentially create a new generation of crack-free materials [6, 8, 9, 10, 3].