Nano-Characterization of Type-G Cement Slurry Incorporating Nanoclay Cured Under High Temperature and Pressure

• DOI: 10.21012/fc9.143
• Publication Date: 2016-06-29T22:24:15Z
• Authors: M. Kalimur Rahman; S. H. Aboubakr; M. M. Reda Taha
• Keywords: 02 engineering and technology; 0210 nano-technology

Type-G cement slurry with various admixtures commonly used in oil/gas well cementing (OWC) incorporating 1, 2 and 3% nanoclay particles by weight of cement were produced. A water/cement ratio of 0.44 was used and the mixes were subjected to a temperature of 290° F and a pressure of 4666 psi for 48 hours. First, the effect of nanoclay on compressive strength evolution was investigated. Second elastic and viscoelastic characteristics of the cementitious mixes were characterized using nanoindentation. The nanoindentation tests enabled evaluating the maximum indentation depth, plastic depth, and the reduced elastic modulus. Furthermore, dwell time of 60 seconds was used to evaluate creep compliance of the cement mixes incorporating nanoclay. Fracture toughness was estimated from the nanoindentation data during the dwell loading period. Scanning electron microscope (SEM) and X-ray diffraction (XRD) microstructural analyses were conducted to explain the results observed using nanoindentation. Furthermore, finite element modeling was used to simulate the nanoindentation test and to extract the stress-strain Type-G cement material incorporating nanoclay and cured under high temperature and pressure. Moreover, The experimental observations showed that nanoclay improved compressive strength evolution with time compared with neat cement and eliminated strength retrogression problem. Furthermore, using 1 and 2% nanoclay resulted in insignificant change (-28 to +12%) of the reduced elastic modulus compared with neat cement. However, a high content of 3% nanoclay resulted in a significant increase of (+54%) in the reduced elastic modulus and a significant reduction in creep compliance compared with neat cement. Fracture analysis of nanoindentation data showed a significant improvement of fracture toughness due to the addition of nanoclay. XRD analysis and SEM investigations proved that the incorporation of nanoclay in the cement mix transforms the Calcium Hydroxide (CH) to calcium silicate hydrate (C-S-H) and reduced capillary porosity leading to higher elastic modulus and reduced creep compliance compared with neat cement. Finally, the extracted stress-strain curves using the finite element method shows that adding nanoclay resulted in stiffening OWC paste. The significance of nanoclay seems strongly dependent on the nanoclay content and the quality of its mixing with cement. DOI 10.21012/FC9.143 Kalimur Rahman et al.