GB2061750A - Screening apparatus for drilling mud - Google Patents

Abstract

Screening of drilling mud is carried out using a screen comprising e.g. two hollow open-ended coaxial frusto-conical screening members (6 and 10), one inside the other and tapering in the same direction. The individual screening members have different mesh sizes which reduce from the inner to the outer screening members. The inner screening member is extended at its narrower end by an imperforate similarly tapering hollow open- ended neck (11) The screen comprises a horizontal central shaft (1) which is rotated and possibly also vibrated of the wider end of the screen. Contaminated mud (13) is fed into the neck (11) and solid particulate contaminants (14 and 15) pass through and along the screening members depending upon their sizes and are dumped from the wider end of the screen. Purified mud (16) passes through the outer screening member (10) into a collecting tank for further use at the drill bit. <IMAGE>

Description

SPECIFICATION Screening of drilling mud This invention relates to screening the drilling mud used in drilling into the earth for exploring for and reclaiming subterranean deposits of fluids, e.g. oil and gas.

In such drilling a drill pipe is suspended from a derrick and carries at its lower end a drill collar provided with a bit. Purified drilling mud is pumped down the drill pipe to the bit and contaminated mud is delivered up the bore outside the drill pipe to a screening system at the derrick where the solid contaminants are removed and the purified mud is pumped back to the bit.

According to the invention there is provided a screen comprising at least two hollow openended coaxial frusto-conical screening members, one inside the or another and tapering in the same direction, and the individual screening members having different mesh sizes which reduce from the inner to the outer screening members, and the inner screening member being extended at its narrower end by an imperforate similarly tapering hollow open-ended neck.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing of a screen according to the invention, in axial section.

In the drawing there is a central shaft 1 on which are keyed three hubs 2 at intervals along the shaft. Spokes 3 radiate from and are welded to each hub 2 and an innermost or first ring 4 is welded to the outer ends of the spokes 3. Between the innermost ring 4 and a second ring 5 is secured an inner hollow open-ended frust-conical screening member 6.

Further spokes 7 radiate from and are welded to the second ring 5 and a third ring 8 is welded to the outer ends of the further spokes 7. Between the third ring 8 and an outermost or fourth ring 9 is secured an outer hollow open-ended frusto-conical screening member 10. The individual assemblies of a hub 2, spokes 3 and first ring 4, second ring 5, further spokes 7 and third ring 8, and fourth ring 9 are so dimensioned that the screening members 6 and 10 are coaxial frusto-conical and tapering in the same direction. Furthermore, the outer screening member 10 has a finer mesh size than the inner screening member 6. Also secured between the first and second rings 4 and 5 at the narrower end of the inner screening member 6 is an imperforate similarly tapering hollow open-ended neck 11.In addition, an annular blanking member 12 is provided closing-off the annular space between the narrower ends of the screening members 6 and 10.

The screen is designed to be used with its shaft 1 horizontal in a screening system where contaminated drilling mud 13 is delivered via a nozzle (not shown) into the imperforate tapered neck 11 and then passes into the interior of the inner screening member 6. The mud and the smaller particles 14 of contaminant solids pass through the inner screening member 6 into the annular space between the latter and the outer screening member 10 while the larger particles 15 pass along the interior of the inner screening member 6 and are dumped from the wider end. From the annular space between the inner and outer screening members 6 and 10 the purified mud 16 passes through the outer screening member 10 into a collecting tank (not shown) while the smaller particles 14 pass through the annular space and are dumped from the wider end of the outer screening member 10.

The purified mud 16 in the collecting tank is then pumped down the drill pipe (not shown) to the drill bit (not shown) where it again becomes contaminated and is delivered back to the imperforate tapered neck 11.

It is envisaged to provide a number of such screens over a collecting tank for purified mud and to rotate the shafts 1 of the screens by a common drive shaft (not shown) at the narrow ends of the screens via a worm and worm wheel gear (not shown), the common drive shaft being driven by a hydraulic motor (not shown). It is envisaged to vibrate the shafts 1 of the screens at their wider ends. The speed of shaft rotation, the amount of shaft vibration and the mesh sizes are dependent upon the kind of material being drilled.

1. A screen comprising at least two hollow open-ended coaxial frusto-conical screening members, one inside the or another and tapering in the same direction, and the individual screening members having different mesh sizes which reduce from the inner to the outer screening members, and the inner screening member being extended at its narrower end by an imperforate similarly tapering hollow open-ended neck.

2. A screen substantially as hereinbefore described with reference to the accompanyin drawing.

3. A system for screening the drilling mud used in drilling into the earth for exploring for and reclaiming subterranean deposits of fluids, comprising a number of screens each according to claim 1 or 2 disposed over a collecting tank for purified mud and means for rotating the respective shafts of the screens in common.

4. A system according to claim 3, comprising means for vibrating the respective shafts of the screens at their wider ends.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Screening of drilling mud This invention relates to screening the drilling mud used in drilling into the earth for exploring for and reclaiming subterranean deposits of fluids, e.g. oil and gas. In such drilling a drill pipe is suspended from a derrick and carries at its lower end a drill collar provided with a bit. Purified drilling mud is pumped down the drill pipe to the bit and contaminated mud is delivered up the bore outside the drill pipe to a screening system at the derrick where the solid contaminants are removed and the purified mud is pumped back to the bit. According to the invention there is provided a screen comprising at least two hollow openended coaxial frusto-conical screening members, one inside the or another and tapering in the same direction, and the individual screening members having different mesh sizes which reduce from the inner to the outer screening members, and the inner screening member being extended at its narrower end by an imperforate similarly tapering hollow open-ended neck. An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawing of a screen according to the invention, in axial section. In the drawing there is a central shaft 1 on which are keyed three hubs 2 at intervals along the shaft. Spokes 3 radiate from and are welded to each hub 2 and an innermost or first ring 4 is welded to the outer ends of the spokes 3. Between the innermost ring 4 and a second ring 5 is secured an inner hollow open-ended frust-conical screening member 6. Further spokes 7 radiate from and are welded to the second ring 5 and a third ring 8 is welded to the outer ends of the further spokes 7. Between the third ring 8 and an outermost or fourth ring 9 is secured an outer hollow open-ended frusto-conical screening member 10. The individual assemblies of a hub 2, spokes 3 and first ring 4, second ring 5, further spokes 7 and third ring 8, and fourth ring 9 are so dimensioned that the screening members 6 and 10 are coaxial frusto-conical and tapering in the same direction. Furthermore, the outer screening member 10 has a finer mesh size than the inner screening member 6. Also secured between the first and second rings 4 and 5 at the narrower end of the inner screening member 6 is an imperforate similarly tapering hollow open-ended neck 11.In addition, an annular blanking member 12 is provided closing-off the annular space between the narrower ends of the screening members 6 and 10. The screen is designed to be used with its shaft 1 horizontal in a screening system where contaminated drilling mud 13 is delivered via a nozzle (not shown) into the imperforate tapered neck 11 and then passes into the interior of the inner screening member 6. The mud and the smaller particles 14 of contaminant solids pass through the inner screening member 6 into the annular space between the latter and the outer screening member 10 while the larger particles 15 pass along the interior of the inner screening member 6 and are dumped from the wider end. From the annular space between the inner and outer screening members 6 and 10 the purified mud 16 passes through the outer screening member 10 into a collecting tank (not shown) while the smaller particles 14 pass through the annular space and are dumped from the wider end of the outer screening member 10. The purified mud 16 in the collecting tank is then pumped down the drill pipe (not shown) to the drill bit (not shown) where it again becomes contaminated and is delivered back to the imperforate tapered neck 11. It is envisaged to provide a number of such screens over a collecting tank for purified mud and to rotate the shafts 1 of the screens by a common drive shaft (not shown) at the narrow ends of the screens via a worm and worm wheel gear (not shown), the common drive shaft being driven by a hydraulic motor (not shown). It is envisaged to vibrate the shafts 1 of the screens at their wider ends. The speed of shaft rotation, the amount of shaft vibration and the mesh sizes are dependent upon the kind of material being drilled. CLAIMS

1. A screen comprising at least two hollow open-ended coaxial frusto-conical screening members, one inside the or another and tapering in the same direction, and the individual screening members having different mesh sizes which reduce from the inner to the outer screening members, and the inner screening member being extended at its narrower end by an imperforate similarly tapering hollow open-ended neck.

2. A screen substantially as hereinbefore described with reference to the accompanyin drawing.

3. A system for screening the drilling mud used in drilling into the earth for exploring for and reclaiming subterranean deposits of fluids, comprising a number of screens each according to claim 1 or 2 disposed over a collecting tank for purified mud and means for rotating the respective shafts of the screens in common.

4. A system according to claim 3, comprising means for vibrating the respective shafts of the screens at their wider ends.