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Drilling Drilling the Conductor Hole, the Rathole and the Mousehole Prior to mobilising and installing the drilling rig on site, it is customary to use a smaller, specialised drilling rig to pre-drill a conductor hole and two neighbouring small diameter holes. These two holes, known in the industry as the rathole and the mousehole, are respectively used during routine drilling operations to temporarily store the "kelly", a square or hexagonal pipe used to impart rotation to the drill string, and to store the next drill pipe to be added to the string. Installing a surface conductor to a depth of approximately 12 m and drilling a rathole (~9 m) and a mousehole (~6 m) prior to the installation of the drilling rig, allow for drilling operations to begin immediately and to proceed more efficiently, as soon as the rig is set up. Preparing the drill site 1 september, 2009
Before drilling starts, the first phase consists in selecting and preparing a site to install the drilling rig and auxiliary services. Although the drilling rig itself only requires a level surface of some 60 m x 25 m, the need for adequate setback space between the well, the flare stack and the surrounding structures, including offices, lodging and laboratories, means that drilling companies must generally prepare an area of 100 m x 100 m. As well as maintaining safe distances between the different elements, an area this size allows for safe on-site handling and storage of the various equipment required for drilling operations. The ground surface must also be prepared to make sure the ground will support not only the weight of the drilling rig, but also the weight of drill pipes or casings which can reach 180 tons. Close
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