Despite recent technological advances with elastomers, polymers, fibers and reactive components that self-heal micro fissures, the cement sheath is not always able to deliver an acceptable long-term solution for today's demanding drilling environment. Changes in downhole conditions with pressure and temperature fluctuations impose stresses on the cement sheath. Consequently, shrinking and debonding of the cement sheath creates very small microannuli allowing fluid migration. Besides these external forces that cause cement sheath damage an evaluation of conventional oil well cement sheath on the nano scale from 1–100 nm reveals that the chemical bond between components is relatively brittle. This paper discusses an active nanotechnology with proven commercial track record that has been specifically developed as a crossover technology for the oil & gas industry.
The measured values from the investigation at molecule level reveal that API Class G cement mixed with patented active nanotechnology provides unique properties. The crystallization process of the cement sheath at a scale of 1 -100 nanometers shows that elements cross-link and create long needle crystalline structures that interlock, block the capillary pores, enhance dynamics and chemistry of the cement hydration process. As a result, the molecule structure changes with hydrogen bridges in stable, locked position. It is important to recognize that the mechanical properties of a cement bound material are determined during the first hours of the binding and during the first 48 hours of the hardening stage. Consequently, if a modification of the cement hydration process is required to enhance the structural, mechanical and chemical resistance behavior of the cement sheath, it has to take place within 72 hours.
The result of this comparative research shows major differences between the samples of API Class G and nano-engineered API Class G cement. Test data shows higher bending forces from the nano enhanced oil well cement as well as significantly stronger values for compressive strength.