It happens relatively often that sand and other material settle on the inside of a pipe belonging to an oil or gas well. Such deposited material may, if there is a sufficient build-up thereof, greatly inhibit fluid flow through the pipe. Normally, the deposited material will be removed by means of tools, as it is common through the application of coiled tubing, snubbing or drilling techniques.

Also in smaller amounts, even if it does not affect the well production to any substantial degree, deposited material may prevent maintenance work, especially when simple methods such as cable operations are involved.

It is not uncommon for sand and other material deposited in a well, even in moderate amounts, to prevent tools from

reaching the desired position in the well during maintenance work.

Oil and gas wells are commonly divided into the following groups: Conventional wells, in which the largest angular deviation from the vertical direction is about 65 degrees.

Extended reach wells, in which the angular deviation relative to the vertical direction exceeds 65 degrees.

Horizontal wells, in which some well sections have an angular deviation of about 90 degrees relative to the vertical direction.

According to the prior art, in conventional wells sand collectors are used, which are lowered into the well by means of a cable, for example. The sand collectors include collecting chambers and are available in designs, in which they are hammered into the sand, suck into the sand by means of a built-in piston arrangement or by a plate opening a room below atmospheric pressure, whereby the well pressure moves sand and other material into the collecting chamber.

The prior art methods are simple and their implementation relatively inexpensive. Thus, they are well suited for conventional wells, in which the deposits form bridges covering the entire pipe cross section, and in which it is

therefore easy to fill the collecting chambers with deposits by means of one of the methods mentioned above.

Two conditions, in particular, distinguish extended reach wells and horizontal wells from conventional wells as far as deposits and methods from clearing out the deposits are concerned. Deposit bridges rarely form in the pipe as, due to gravitational forces, the deposits form on the downward circumferential half. Prior art sand collectors, which are arranged to be sucked down into the deposits, are not efficient when the deposits are spread along the pipe as the . collectors will essentially be filled with fluid.

The gravitational forces acting on a tool in the axial direction of the well pipe decrease with the angular deviation of the well relative to the vertical axis, and are nil at horizontal well sections. Cable tools depending on the axial component of the tool weight to work satisfactorily, cannot be used in such conditions. The tools may be supplemented with well tractors to improve propulsion, but such devices do not normally exert sufficient force to fill a collecting chamber of the prior art.

The invention has as its object to remedy the drawbacks of the prior art.

The object is realized according to the invention through the features specified in the description below and in the following Claims.

A collecting device includes a scraping and conveying device, which, besides loosening deposited mass, transports the loosened mass into a collecting chamber.

The scraping tool, in the following referred to as a scraper, formed by a knife-like rotor and a conveyor auger, is driven by a motor provided in the tool. The rotating scraper tears up the deposited mass, after which the conveyor auger, advantageously rotating about an axis shared by the scraper, moves the loosened mass from the scraper in through a pipe and further into a collecting chamber. The invention may be connected to a well tractor which moves the collecting device along extended reach well sections and horizontal well sections. The invention is also well suited for use in conventional wells.

After the collection chamber has been filled, the tool is pulled up to the surface where it is emptied. The operation is repeated until the sand/debris deposit has been removed.

In the following is described a non-limiting example of a preferred embodiment, which is visualized in the accompanying drawings, in which: Fig. 1 shows a collecting device according to the invention at work in a well casing; and Fig. 2 shows a longitudinal section of the collecting device of Fig. 1.

In the drawings the reference numeral 1 identifies a collecting device according to the invention, comprising a scraper 2, a first bearing housing 4, a feed pipe 6 fixedly connected to the first bearing housing 4, a second bearing housing 8 fixedly connected to the opposite end portion of the feed pipe 6, a receptacle 10 fixedly connected to the

second bearing housing 8 and a motor housing 12 fixedly connected to the opposite end portion of the receptacle 10.

The collecting device 1 is preferably connected to a well tractor 14, known in itself, by means of a connector 16.

An electric or hydraulic motor 18 is disposed in the motor housing 12 and rotates a shaft 20, the shaft 20 extending concentrically through the receptacle 10 to a second bearing 22 disposed in the second bearing housing 8. A conveyor auger 24 is rotationally fixed to the shaft 20 and extends from the 'shaft 20 through the feed pipe 6 to a first bearing 26 disposed in the first bearing housing 4. The scraper 2 is fixedly connected to the conveyor auger 24.

A shut-off device 28, which may be in the form of a valve flap formed of an elastic material for example, is arranged at the second bearing housing and is arranged to prevent collected mass from flowing out of the receptacle 10. If convenient, the shut-off device 28 may be disposed above the first bearing housing 4.

When the collecting tool 1 is moved within a well pipe 30 by means of the well tractor 14, the propulsion resistance of the well tractor 14 increases as the tool 1 is moved into deposits. At a predetermined propulsion resistance the motor 18 starts automatically, whereby the rotating scraper 2 driven by the shaft 20 and conveyor auger 24, loosens the deposits while, at the same time, the scraper 2 feeds the deposits into the conveyor auger 24. Then, the deposits are moved internally through the feed pipe 6 by means of the rotating conveyor auger 24 into the receptacle 10.

The shaft 20 may be provided with conveyor auger vanes 32 to facilitate the filling of the receptacle 10.

When the receptacle 10 has been filled with deposits, the collecting tool 1 is returned to the surface, where the receptacle 10 is emptied. The cleaning operation is repeated until the deposit has been removed. When the deposit is no longer present, the propulsion resistance of the well tractor 14 will be reduced to a level below the level of engagement of the engine 18, whereby the collecting device 1 will be moved in the well pipe 30 without the scraping tool 2 and the . conveyor auger 24 rotating.