When a well is drilled through the horizon of a coalbed from which the coal has been removed, the hole shall be drilled at least thirty feet below the coalbed, of a size sufficient to permit the placing of a liner which shall start not less than twenty feet beneath the horizon of the coalbed and extend not less than twenty feet above it. Within this liner, which may be welded to the casing to be used, shall be centrally placed the largest-sized casing to be used in the well and the space between the liner and casing shall be filled with cement as they are lowered into the hole. Cement shall be placed in the bottom of the hole to a depth of twenty feet to form a sealed seat for both liner and casing: Provided, That the liner may extend back to the surface and serve as the freshwater or coal protection casing, if done in accordance with sections eighteen and twenty-one of this article, as applicable. If the liner is constructed in this manner, the next string of casing to be run into the well shall extend at least twenty feet below the coalbed. Cement shall be placed between that string of casing and the liner from the bottom of the casing to a point at least twenty feet above the coalbed. Following the setting of the liner, drilling shall proceed in the manner provided above. Should it be found necessary to drill through the horizon of two or more workable coalbeds from which the coal has been removed, the liner shall be started not less than twenty feet below the lowest horizon penetrated and shall extend to a point not less than twenty feet above the highest horizon.