Patent Publication Number: US-6220347-B1

Title: Bore hole clearing

Description:
FIELD OF THE INVENTION 
     The present invention relates to the clearing of tubes and bores, and particularly oil well and like bore holes. 
     BACKGROUND OF THE INVENTION 
     In the drilling and operation of oil wells, a considerable amount of apparatus is often placed down the bore holes. (Although the term “down” is used, some bore holes may have considerable lengths which are far from vertical, and may be substantially horizontal). There can be considerable flows of material trough the bore hole, such as mud used for driving drill heads, and wires or pipes may be passed through the bore hole. Further, the bore hole may pass through friable strata which may be eroded. All these matters can result in the accumulation of detritus, which will here be termed “mud”, in the bore hole; its consistency may of course vary widely. The mud may be deposited along the length of the bore hole, or on top of a piece of apparatus in the bore table. 
     It is often desirable or necessary to clear a bore hole of such mud. Present techniques for such clearing are relatively primitive. Some form of scraper or similar mechanical device may be lowered into the bore hole in an attempt to loosen compacted mud, and some form of bucket or similar mechanical device may similarly be lowered into the bore hole in an attempt to capture particles or pieces of mud and pull them up to the surface. 
     OBJECT OF THE INVENTION 
     The general object of the present invention is to provide an improved technique for clearing bore holes of mud. 
     SUMMARY OF THE INVENTION 
     According to one aspect, the invention comprises using a electric motor coupled to a pump to remove mud from a bore hole. 
     According to another aspect, the invention provides apparatus for clearing a bore hole or the like of debris, comprising a housing, and a cylindrical electric motor coupled coaxially to a direct drive pump, the housing including a debris entry port into which the debris is induced to flow into the housing and wherein the inside of the housing is maintained at an inside pressure which is lower than the outside pressure. 
     Preferably the apparatus includes debris collection means for effectively isolating any debris pumped by the pump from the bore hole. 
     The electric motor preferably has a central passage through which material pumped by the pump can pass. 
     The apparatus preferably has a head rotatable by the motor for engagement with debris deposits in the bore hole. The head may be directly attached to the worm of the pump where the pump is a direct drive worm pump, or the head may comprise a tubular housing around the motor and/or pump. In the latter case, the housing may extend along the whole length of the motor and pump, with the apparatus including a port settable to allow debris to be pumped into the housing from either end. 
     The debris collection means may be a compartment attached to the motor and having a filter through which fluid may pass but which traps debris. Alternatively, the debris collection means may be a pipe (of the type known as a coiled pipe) extending from the bore hole head to the motor and pump. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Two bore hole mud clearing apparatuses embodying the invention will now be described, by way of example and not intended to be limiting, with reference to the drawing, in which: 
     FIG. 1 is a longitudinal section through the first apparatus; 
     FIG. 2 is a longitudinal section through the second apparatus; and 
     FIG. 2A is a longitudinal section through the second apparatus in a second configuration. 
    
    
     SPECIFIC DESCRIPTION 
     Referring to FIG. 1, this shows a bore hole  10  in which a piece of apparatus  11  has become detached. This piece of apparatus has a coupling element or fish  12 , which is intended to allow the apparatus  11  to be grasped and so pulled out of the bore hole. This fish has become covered by mud  13 , and it is necessary to remove this mud before the fish can be reached and grasped. 
     The bore hole  10  also contains a bore hole mud clearing apparatus  20 , which comprises three main components; a motor  21 , a pump  22 , and a mud collection chamber  23 . This apparatus is linked to the bore hole head by means of a wire  24 , which supports the apparatus mechanically (so that it can be pulled out of the bore hole) and also carries an electric power cable to the apparatus. 
     The motor  21  is a cylindrical electric motor comprising an outer stator  30  and an inner rotor  31  which has a cylindrical passage  32  along its length. The motor is powered from the power carried through the wire  24  via a connector  33 . 
     The pump  22  is a direct drive worm pump. A worm  35  is connected to the motor rotor  32 , and a housing  36  is connected to the motor stator  31 . Ports  37  provide a passage between the pump and the bore  32  through the motor. A head housing  38  is mounted on the end of the pump housing  36 , and a head rotor  39  is mounted on the end of the pump worm  35 . 
     The other end of the motor bore  32  communicates directly with the mud collection chamber  23 , which has a filter  40  which retains mud but allows liquid to escape. 
     In use, the motor  21  drives the pump  22  to suck up the mud  13  (the whole of the bore being filled with a suitable liquid acting as a carrier). The head  39  rotates against the mud, helping to loosen pieces from the body of mud. The pieces of mud sucked up are passed through the bore  32  through the motor and are collected in the mud collection chamber  23 . 
     Referring now to FIG. 2, a second bore hole mud clearing apparatus is shown. This apparatus is connected to the bore hole head by means of a coiled tube  24 ′(so termed because it is a tube and the part not in the hole is retained in the form of a large coil at the bore hole head). This coiled tube  24 ′ is hollow, and carries the electric power cable to the apparatus. 
     As before, this apparatus comprises a motor  21  and a pump  22 . The motor and pump are, in this apparatus, enclosed within a tubular housing  47 , which has a nose  46  attached to its front end. The pump rotor has attached to it a coupling element  45  which is contained within the housing nose  46  as shown. This nose is filled with viscous oil, so that the tubular housing will rotate with the motor and pump, though at slower speed. The housing terminates in an annular head  48 , which rotates against the mud, helping to loosen pieces from the body of mud. The pieces of mud are sucked away from the mass of mud  13  through the tubular housing  47 , around the nose  46  and through ports  49  into the pump. 
     From the pump  22 , the sucked up fluid with pieces of mud are passed through the passage  32  of the motor  21 . At the other end of the motor, the passage is connected to the center of the coiled tube  24 ′, through which the sucked up fluid with the pieces of mud passes to the bore hole head. The tube  24 ′ is made up of inner and outer tubes  51  and  50  as shown. 
     In the FIG. 2 configuration, the apparatus is being pushed forward along the bore hole to clear mud from in front of it. FIG. 2A shows an alternative configuration of the apparatus, in which it has been passed down the bore hole and is being pulled back out. In this configuration, it clears mud lying between it and the well head. 
     The position of the motor and pump relative to the tubular housing  47  is determined by the relationship between the nose  46  at the front end of the housing and the coupling element  45  attached to the pump rotor. When the apparatus is being pushed into the bore hole, the relative position of these elements  45  and  46  is as shown in FIG.  2 . When the apparatus is being pulled out of the bore hole, the coupling element  45  moves to the other end of the interior of the nose  46 , as shown in FIG.  2 A. This results in some ports  49  being closed and other ports  49 ′ being opened. 
     The pump now sucks from the other end of the housing  47  (the left hand end as seen in the drawings). The housing  47  rotates in the same way in both configurations of the apparatus, and has a second annular head  48 ′ at its left hand end. In the FIG. 2A configuration, this head  48 ′ rotates against the mud in the bore above the apparatus, ie between the apparatus and the bore hole head. As a result, the apparatus acts to clear mud from the bore as it is being drawn out of the bore hole, as well as when it being lowered into the bore hole (ie in the FIG. 2 configuration). 
     The rotating nose  46  may also be provided with a helical auger, so that the as the nose rotates, the auger moves the mud, assisting the action of the pump. 
     Referring back to the embodiment shown in FIG. 1, the apparatus may be hung upon a length of coiled tubing rather than the wire  24 , that is, in a similar fashion to the embodiment shown in FIG.  2 . The filter  40  may be dispensed with, and the outlet instead connected to the coiled tubing. Provided that the coiled tubing and the power cable are chosen so that there is sufficient bore available, the mud and debris may then be pumped to the surface through the coiled tubing. 
     Alternative embodiments using the principles disclosed will suggest themselves to those skilled in the art, and it is intended that such alternatives are included within the scope of the invention, the scope of the invention being limited only by the claims.