Which method is used to seal the casing in consolidated formations?

Utilizing cement grout is the correct method for sealing the casing in consolidated formations. This sealing method is important as it provides a strong and durable barrier between the well casing and the surrounding geological formation. Cement grout effectively prevents the migration of water and contaminants between different aquifers or from the surface into the well, ensuring water quality and protecting groundwater resources.

In consolidated formations, the rock is typically more solid and less porous, so a strong sealing method is essential to maintain the integrity of the well. Cement grout can be tailored in its composition to suit specific conditions found in different geological environments, making it a versatile choice for well construction and sealing.

Other methods like applying a thin layer of sand or using biodegradable materials may be less effective in maintaining a long-term seal against water movement in these types of formations and may not provide the necessary structural integrity needed for a reliable well. Filling with air is not a viable sealing method, as it does not prevent water inflow or contamination and would be ineffective in a practical sense for well casing applications.