One of the promising and expected nanomaterials that will play an important role in industry is carbon nanotubes (fig. 1).
It is known that in the middle of the 20th century, various groups of researchers involved in the catalysis of chemical reactions involving hydrocarbons drew attention to unusual oblong structures in the soot covering the catalyst.
Today, there are many ways to synthesize single-wall and multi-wall carbon nanotubes. For a general understanding, you can imagine a small folded part of a graphene sheet into a tube with glued edges – this will be the most ordinary single-walled carbon nanotube. This material has properties similar to graphene, such as high mechanical strength and electrical conductivity. In addition, carbon nanotubes have unique properties in extreme conditions such as high pressure [8].
FIG. 1. CNT under the microscope
The growing demand for the development of deep hydrocarbon deposits in difficult thermobaric conditions (High Pressure High Temperature), requires advanced technological solutions that overcome operational problems during their development. The rheological properties of cement mortars directly depend on the temperature conditions of the well, and additives used in practice that increase the pumpability of solutions have an ambiguous effect on the quality of cement stone.
The articles of Khan W.A. and Rahman M.K. [9, 10] describe the researches conducted to study the compressive strength of cement stone and the rheological properties (plastic viscosity, yield strength and strength) of grouting solutions with additives of multi-walled carbon nanotubes (MWCNT) under conditions of high pressure and temperature HPHT (Fig. 2).
The authors emphasize the importance of designing and implementing new technologies for cost-effective cementing in simulated downhole conditions of HPHT oil and gas wells. This difficult task deserves special attention when choosing a grouting solution and its modifiers to achieve the required mechanical and rheological properties of the cement mortar.
FIG. 2. MWCNT photos under a microscope
The research of the authors of the article found that even a small introduction (0.1, 0.25 and 0.5%) of MWCNT into grouting solutions leads to a significant increase in the compressive strength of cement stone, improves the rheological properties of cement mortars and, consequently, their pumpability in difficult thermobaric (HPHT) conditions.
Many research groups dealing with concretes and composite materials have attempted to study the effects of various carbon additives in cement mixtures. Scientists used not only graphite, graphene and CNT, but also considered the effect of fullerenes and fullerene soot on the physico-mechanical characteristics of cements.
