TY - JOUR T1 - Nano-chemo-mechanical signature of conventional oil-well cement systems: Effects of elevated temperature and curing time JF - Cement and Concrete Research Y1 - 2015 A1 - Konrad J. Krakowiak A1 - Jeffrey J. Thomas A1 - Musso, Simone A1 - James, Simon A1 - Ange-Therese Akono A1 - Franz-Josef Ulm AB -

With ever more challenging (T,p) environments for cementing applications in oil and gas wells, there is a need to identify the fundamental mechanisms of fracture resistant oil well cements. We report results from a multi-technique investigation of behavior and properties of API class G cement and silica-enriched cement systems subjected to hydrothermal curing from 30 °C to 200 °C; including electron probe microanalysis, X-ray diffraction, thermogravimetry analysis, electron microscopy, neutron scattering (SANS), and fracture scratch testing. The results provide a new insight into the link between system chemistry, micro-texture and micro-fracture toughness. We suggest that the strong correlation found between chemically modulated specific surface and fracture resistance can explain the drop in fracture properties of neat oil-well cements at elevated temperatures; the fracture property enhancement in silica-rich cement systems, between 110° and 175 °C; and the drop in fracture properties of such systems through prolonged curing over 1 year at 200 °C.

Fig.1. Particle size distribution of the silica flour (ground quartz) incorporated…

Fig.2. Location of the “chemical poles” of the cement clinker and cement hydration…

Fig.3. Simplified schematic of: (a) the cement paste microstructure cured at room…

Fig.4. A schematic of the effect of adding an extra dimension, Al, to the statistical…

Fig.5. X-ray powder diffraction spectra with qualitative analysis of the major phases…

Fig.6. Thermal gravimetric analysis (TGA) carried out on samples cured in the…

VL - 67 JO - Cement and Concrete Research ER -