The invention relates to a device for a derrick or a drilling mast.

A drilling rig comprises a tower or a mast, in the following only called a derrick, which constitutes a supporting element of a lifting device for lifting tubes into and out of an oil well.

The derrick is designed to be capable of carrying com¬ ponents which are comprised by the lifting device, such as snatch block and hook, and the weight of tubes and other things which are lowered into a well. The derrick itself stands on a strong structure, normally being made of steel profiles, provided with a solid deck or a floor called the drill floor on top. Said structure together with drill floor and derrick constitute the carrying components of a drilling rig. The drill floor and the structure underneath are dimensioned to, among other things, stand the weight of several hundred tons of drill tubes which are stored temporarily, in an up- right position, at the one side edge of the drill

floor, when the drill bit or other downhole tool is being replaced. On a production installation covering several wells, the structure carrying the drill floor and the derrick is placed displaceably on a plane called a skid, so that the drilling rig may be skidded from one well to another.

A drawback of the known arrangement is that a drilling rig will be very heavy.

The object of the invention is to provide a device for a drilling rig, which gives a considerable reduction in weight compared to known technique.

The object is realised through the features stated in the following description and subsequent claims.

According to the invention a drill floor is arranged in the derrick somewhat above the foot thereof, contrary to known devices, in which the derrick stands on the drill floor or on the structure on which the drill floor rests. The derrick may thus rest directly on the skid or on some other carrying part of the oil instal- lation. The drill floor is secured in the derrick it¬ self at a normal height above the foundation on which the derrick stands, corresponding to the height of the sub-structure which is normally arranged between the derrick and said foundation. Temporary storing of standing tubes is in a storage area resting on said foundation, i.e. at a lower level than the drill floor. Somewhat simplified the invention may be described as the carrying structure, on which the drill floor and the derrick normally rest, having been removed and the drill floor having been lifted in the derrick to give room for blow-off valves and other equipment which must

be placed underneath the drill floor. The derrick is secured to the foundation in a manner known in itself, maybe displaceably.

The device may be used for simple light-weight snubbing rigs as well as big drilling rigs. Snubbing rigs need not have a drill floor in the usual sense, but will then have some other corresponding main working plat¬ form.

The invention will be described in further detail in the following, by means of a non-limiting exemplary embodiment, with reference to the accompanying draw¬ ings, in which

Fig. 1 is a front view of a drilling rig;

Fig. 2 is a rear view of the drilling rig;

Fig. 3 is a side view of the drilling rig.

In Fig. 1 the reference numeral 1 indicates a portal- shaped derrick with a crown block 2 mounted at the top and a travelling block 3. The derrick 1 rests on a foundation in the form of a skid 4, and a drill floor 5 is secured to the derrick 1 somewhat above the foot of the derrick 1. A blow-off valve 6 is shown schemati¬ cally underneath the drill floor 5. A storage area 7 for standing tubes 8 is shown in Fig. 3. The tubes 8 which are kept in a vertical position in a known manner by means of a finger board 9 provided with wind screen, are not shown in Fig. 1 nor in Fig. 2. Tube-handling equipment 10 is arranged in the derrick 1 in a known manner. Equipment which is often found to be placed

underneath the drill floor 5 in known arrangements, may with advantage be placed in containers beside or behind the derrick 1. In Figs. 2 and 3 are schematically shown stacked containers 11, 12 and 13 which may contain, among other things, equipment like electric plants, valves, pipes and equipment for handling drill fluid. In Fig. 3 are shown stays 14 which support the derrick 1 laterally. Hand-rails, ladders and other equipment necessary, is assumed to be well known to one skilled in the art, and will therefore not be discussed in further detail.