The word “improvements” must be construed to mean surface improvements, machinery, and other equipment used and necessary for the operation of drilling on the land for oil or gas and the extraction of coal, cement materials, sodium sulfate, sand and gravel, road materials, building stone, chemical substances, metallic ores, or colloidal or other clays, and work performed in the development of the property for such purposes when the development work is of practical value for future operation and drilling upon the land. Wells drilled for oil or gas which do not produce oil or gas in commercial quantities may not be considered improvements.