It is made possible to conduct inner defect inspection using spatial discrete data such as X-ray CT data with higher precision. When the flow rate of a cooling target fluid passing through a cooling system is high, the fan revolution speed of a cooling fan of the cooling system is controlled to achieve a target fan revolution speed so that the detected temperature of the cooling target fluid reaches a preset target temperature. Between the tamping tip and the tube a substantially cylindrical tamping element is interposed, adapted to define a tamping diameter of the ground which forms the walls of the hole obtained by the device at least equal to the diameter of the tube. The method is particularly useful for fracturing operations in medium to high permeability formations.