Abstract
Drilling ever deeper, and thus in increasingly difficult conditions, is associated with restrictive requirements that must be met by cement slurries. This implies the need to use advanced, innovative measures that will significantly improve the performance parameters of the cement slurry and cement stone. Due to its unique properties, an admixture of nanosilica improves the properties of the cement stone and allows for appropriate zone insulation. The article presents the results of strength tests of cement stone samples with the addition of silica nanoparticles deposited in an environment of increased temperature of 90 °C. In all three cases of modification with an admixture of nanosilica (type 1, 2 and 3, concentration 0.5%, 1% and 5%), the cement stone shows an improvement in mechanical properties, which is manifested by an increase in compressive strength. The most homogeneous results of strength measurements are for cement slurries with an admixture of type 3 nanosilica (the highest average strength: 132–149% in relation to the base sample). They show the smallest stretch marks and deviations from the average. The highest average increase in strength is for the sample with the addition of 1% nanosilica (on average 124% in relation to the base sample). This amount causes the greatest increase in strength with no significant deterioration of rheological parameters.
Highlights
In the petroleum industry, the purpose of cementing in boreholes is primarily to create a resistant and durable barrier against fluid migration
It is important to obtain a permanent connection of the cement sheath in the annular space between the borehole wall and the casing column
The presence of highly mineralized reservoir brines and hydrogen sulfide, which adversely affect the durability of the cement sheath, is important [1,2]
Summary
The purpose of cementing in boreholes is primarily to create a resistant and durable barrier against fluid migration. Examples are chemical or electrochemical precipitation, vapor deposition, atomic or molecular condensation, sol-gel processes, spray pyrolysis, laser pyrolysis, aerosol processes, and chemical or biological reduction Due to their large surface area, high aspect ratio, small size, low density, large surface area and interesting physicochemical properties, they have a strong influence on the mechanical properties of cement materials [18,19]. The literature [11,21,22,23] provides examples of the use of nanoparticles as well as nano-SiO2 and nano-Fe2 O3 additives improving the strength parameters of the cement matrix. The addition of nanosilica increases the efficiency of C-S-H gel formation by promoting pozzolanic reactions It influences the improvement of the microfilling effect of the cement matrix space.
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