PROCESS FOR THE MANUFACTURE OF A CYLINDRICAL PIPE The invention relates to a process for the manufacture of a substantially cylindrical pipe at a workshop on site for use in a hole or tube, in which a flat metal stock, coiled on a reel, is unreeled, the unreeled flat metal stock is formed to a substantially round pipe shape with a seam which runs parallel to the axis of the pipe, the seam is closed and bonded, and the produced substantially cylindrical pipe is run into the hole or tube.

The substantially cylindrical pipe is preferably continuous. It is advantageously manufactured at a wellsite for use in a wellbore, but it can be suitably in the form of single joints, and it may also be made at any other site or workshop and then transported, e. g. for use inside surface lines.

The flat metal stock is suitably made from malleable metal, preferably from malleable steel i. e. from a formable steel grade.

Advantageously slots are made in the unreeled flat stock before the forming of the continuous pipe. This is preferably done by cutting, although other methods such as stamping may be applied. Cutting is preferred because by this method no material is taken away from the flat metal stock. The cutting is suitably carried out by means of a roller with protruding integrated wedge shape knives on its circumference. These knives have suitably been formed by means of a milling cutter which mills the knives out from the roller body. The knives can also be cut out from a non-hardened steel roller body which is suitably hardened after manufacturing.

The present process for the production of a continuous slotted pipe is very much preferred over the conventional processes in which the slots are made in a round pipe by abrasive hydrojetting, saw-blade-cutting, laser-cutting or plasma cutting, because in a round pipe slots cannot be made by roller cutting (no removal of material) or stamping and simple cutting and stamping methods are much cheaper than abrasive hydrojetting, saw- blade-cutting, laser-cutting or plasma cutting.

A roller process for making the slots is cheap because it is a continuous process whereby the slot configuration is fixed and does not have to be positioned for every slot, the positioning of the slots being important for the use of the ultimate slotted substantially cylindrical pipe.

In the present process the unreeled flat, metal stock, be it slotted or non-slotted, is formed to a substantially round pipe with a seam which runs parallel to its axis and thereafter the seem is closed and bonded.

The bonding is preferably carried out by welding although other methods, such as brazing or zipping may be used.

The flat metal stock from which the continuous pipe is formed according to the present invention may in principle have any thickness and width but for practical purposes thicknesses and widths in the ranges of from 1 to 8 mm and 0.075 to 1.5 m, respectively, are preferred.

This will eventually result in pipes with external diameters in the range of from, about 25 mm (1 inch) to 0.5 m (20 inches), the internal diameters being dependent on the thickness of the original flat metal stock.

The cylindrical non-slotted pipe which has been made according to the present invention is advantageously used as a work or drill string to treat or drill a borehole.

In this way a borehole can be treated or drilled using a tubing which has been produced from unreeled flat stock

at the wellsite as disclosed hereinbefore. To the tubing a downhole motor driving a drill bit is connected during the drilling. The downhole motor and the drill bit could remain in the borehole after the borehole has been completed.

After the drilling the non-slotted tubing is preferably expanded in the borehole to form a casing. By using a non-slotted tubing which has been made in accordance with the present invention as a drill string which, after expansion, acts as a casing, a considerable saving of time and costs is achieved.

In alternative cases a well is first drilLed using a non-expandable drill string, whereafter the drill string, the motor and the drill bit are removed from the well and an expandable pipe made in accordance with the present invention is lowered in the borehole and this pipe is radially expanded to form a casing, liner or casing patch in the borehole.

To form a completion system in borehole from which oil can readily be produced a cylindrical pipe made from slotted flat stock is lowered in the borehole and is radially expanded therein. The expansion is advantageously carried out by running an expander cone through the pipe. The expansion may also be suitably effected by means of an expandable pig or mandrel, e. g. a hydraulic expandable packer or steel reinforced bladder system. Such techniques are disclosed in WO 98/00626, EP 0643794 and EP 0643795.

The greatest advantage of the present invention is the ability to build continuous tubulars on site with diameters which are much larger than those which are currently available on a reel, because the tube size determines the reel diameter which is restricted to make the reels transportable.