Development of the composition of lightweight cement slurry using microspheres and microsilica

It is well known that Portland cement has long been used in the construction of oil and gas wells. In this case, cementing slurries based on Portland cement are placed in the annular space, and after setting, they provide long-term isolation of the formations for subsequent operation. Therefore, the cementing process and the quality of these operations are of significant importance. To minimize of complications due to circulation loss, effective lightweight additives, including microspheres and microsilica, are widely used. However, when using microspheres, they may float when the water-cement ratio increases, and the resulting slurries exhibit high water yield. Microsilica in the cement slurry reduces water yield and does not float, but it thickens the slurry. The aim of this work is to develop lightweight cementing slurries for moderate temperatures with the rational use of the aforementioned additives. The authors of this article have developed a composition of lightweight cementing slurries for various climatic conditions using these additives. It has been specifically demonstrated that by adding 10% microspheres and 10% microsilica, effective lightweight cementing slurries can be obtained, where the various properties of the additives produce a positive outcome. The addition of 0.1% anhydrous sodium silicate to the cement slurry further improves the primary technological parameters of the slurry and, in general, the cement stone. Based on the conducted studies, an increase in the compressive strength of the cement stone to 7.04 MPa with a water-cement ratio of 0.7 was observed. Keywords: cement; microsphere; microsilica; lightweight; slurry.