Abstract:
Apparatus and method for centrifugal pump with screw pump accelerator and reverse vane impeller adapted for use in sample collection from drilling fluid containing drill cuttings.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present invention claims the benefit of U.S. Provisional Patent Application No. 60/867,161, filed Nov. 24, 2006, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to centrifugal pumps. More particularly, the present invention relates to centrifugal pumps for fluids containing solids. 
       BACKGROUND OF THE INVENTION 
       [0003]    During the drilling of a well, mud is circulated down hole to carry away drill cuttings. On the surface the mud is recirculated in different tanks using pumping units for delivering the mud to de-silter and de-sander. 
         [0004]    Pumping of such fluids in a consistent manner can be difficult, which may make sample collection difficult and adversely affect readings or analysis of the samples. 
       SUMMARY OF THE INVENTION 
       [0005]    A pump of the present invention may be used to deliver mud to a sample catcher, which benefits from a consistent flow for analytical measurement on drilling cuttings contained in the mud. 
         [0006]    The present invention relates to an apparatus for pumping drilling mud with cuttings collected from active mud systems to the necessary height of reservoir. Specifically the pumping is performed in the field from possum belly (or mud box) to the sample catcher. The invention is providing the means for compact, portable and flow quantity adjustable pumping device for confined space as possum belly on the shale shaker. 
         [0007]    In a first aspect, the present invention provides an apparatus for pumping drilling fluid containing drill cuttings having a reverse vane pump, a screw pump, a centrifugal pump, a drive shaft common with the reverse vane pump, the screw pump, and the centrifugal pump, the drive shaft adapted to be rotatably driven by a motor. 
         [0008]    Preferably the screw pump includes helical auger. Preferably the reverse vane pump includes a blade impeller, the blade impeller having a plurality of radial blades. Preferably the blades are mounted at an angle forming a pitch. Preferably the pitch is between about 15° and about 75°. More preferably the pitch is between about 30° and about 60°. Most preferably the pitch is substantially 45°. 
         [0009]    Preferably the centrifugal pump includes a horizontal centrifugal impeller. Preferably the horizontal centrifugal impeller comprising a substantially planar wing mounted to an radial arm. Preferably the radial arm includes a twisted wing mounted at an arm angle. Preferably the arm angle is between about 15° and about 75°. More preferably the arm angle is between about 30° and about 60°. Most preferably the arm angle is substantially 45°. 
         [0010]    Preferably the apparatus includes a common housing, housing the reverse vane pump, the screw pump, and the centrifugal pump, the common housing having an upper portion proximate the centrifugal pump and a lower portion proximate the reverse vane pump. Preferably the upper portion comprising a window, the window adapted to allow air into the common housing. Preferably the lower portion includes a screen or guard, adapted to restrict the flow of larger objects into the apparatus. 
         [0011]    Preferably the lower portion includes a screw pump inlet, the screw pump inlet having an opening through the lower portion of the common housing and extending along at least a portion of the screw pump. Preferably, an adjustable lift assembly for regulating the depth of submersion of the apparatus into the drilling fluid containing drill cuttings is provided. 
         [0012]    Preferably the apparatus is powered by a drive means. Preferably the drive means includes an electric motor or a hydraulic motor, the hydraulic motor driven by pressurized hydraulic fluid from a hydraulic power pack. 
         [0013]    In a further aspect, the present invention provides a method for pumping drilling fluid containing drill cuttings including providing air into the drilling fluid containing drill cuttings for decreasing the density of the drilling fluid containing drill cuttings. 
         [0014]    Preferably the drilling fluid containing drill cuttings and air are agitated or otherwise blended or mixed or circulated. 
         [0015]    Preferably pressurized air is injected into the drilling fluid containing drill cuttings. 
         [0016]    Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein: 
           [0018]      FIG. 1  is a general view of a centrifugal pump with screw pump accelerator and reverse vanes; 
           [0019]      FIG. 2  is a top view of the centrifugal pump; 
           [0020]      FIG. 3  is a detail view of the centrifugal pump along the section  3 - 3  of  FIG. 2 ; 
           [0021]      FIG. 4  is a detail view of the reverse vane pump; and 
           [0022]      FIG. 5  is a detail view of the reverse vane pump along section  5 - 5  of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Referring to  FIG. 1 , a centrifugal pump  1 . 1  of the present invention includes a centrifugal part  1 . 1 , a screw pump part  1 . 2  and a reverse vane pump part  1 . 9 . A motion axle or shaft  1 . 3  operably connects a centrifugal impeller (such as a flat 90-degree wing  1 . 6  or a twisted 45-degree wing  1 . 7 ) and a screw pump impeller (such as screw pump blades  1 . 5 ), corresponding to that disclosed in pending U.S. patent application Ser. No. 10/907,485 filed Apr. 2, 2005 which is incorporated herein by reference, along with a reverse vane impeller  1 . 95 . The motion axle or shaft  1 . 3  may be driven by common drive means such as an electric motor  1 . 4 . 
         [0024]    An air inlet upper window  1 . 8  may be located proximate the centrifugal part  1 . 1 , for example generally at an upper portion of the centrifugal part  1 . 1  (as shown), the air inlet upper window  1 . 8  adapted to allow air to be drawn into the centrifugal part  1 . 1  in a controlled manner. The air inlet upper window  1 . 8  may be sized appropriately to allow a desired amount of air to be drawn into the casing, as would be known to one ordinarily skilled in the art. An optional screen or guard, such as ½ filter screen  3 . 0  (see  FIG. 1 ), may be provided to restrict flow of larger drill cuttings or particles or other solids into the centrifugal pump. The reverse vane impeller  1 . 95  may chop, cut, or grind the pumped material to break up the material or reduce the size of lumps, chunks, drill cuttings, or particles. The reverse vane impeller  1 . 95  may clean or help clean the filter screen  3 . 0 . Preferably there is a gap between the bottom of the pump and the bottom of the screw pump blades  1 . 5 . Preferably the gap is between about 4″ (100 mm) and about 6″ (150 mm). Preferably there is a gap between the reverse vane impeller  1 . 95  and the screw pump blades  1 . 5 . The gap is preferably at least 4″ (100 mm) for a 2×6″ pump. 
         [0025]    Referring to  FIG. 2 , an outlet  2 . 1  is shown extending centrifugally from the centrifugal part  1 . 1 . The twisted 45-degree wings  1 . 7  may provide mixing of the pumped fluid and the inlet air, particularly when placed proximate the motion axle or drive shaft  1 . 3  (as shown in  FIG. 1 ). 
         [0026]    Referring to  FIG. 4 , a reverse vane impeller  1 . 95  is shown as a plurality of vanes extending from the motion axle or shaft  1 . 3 . While shown as having two vanes or blades (e.g. like a propeller), one skilled in the art would recognize that any number of vanes (two or more) would be suitable. While shown as having an approximate reverse pitch of about 45°, one skilled in the art would recognize that pitch as only one example. The reverse vane impeller  1 . 95  is shown pitched down (when rotated clockwise from above—see  FIG. 2 ). The reverse vane impeller  1 . 95  is adapted to cause at least a partial reverse flow, in the direction opposite to the flow imparted by the screw pump blades  1 . 5  (see  FIG. 1 ). While shown ( FIG. 2 ) as being approximately 90° rotated relative to flat 90-degree wing  1 . 6  or twisted 45-degree wing  1 . 7 , one ordinarily skilled in the art would recognize the rotational orientation of the reverse vane impeller  1 . 95  may be anywhere between 0°-360°. 
         [0027]    The liquid/drilling mud is pumped up by screw pump part  1 . 2  creating positive pressure for centrifugal pump. This positive pressurizing increases performance in 3 ways: 
         [0028]    The mud level fluctuations that are very common on the drilling rigs are compensated by screw pump part  1 . 2 . Also by adjusting the level of pump one can adjust the quantity of mud pumping which is not possible with just a screw or centrifugal pump alone. The centrifugal pump  1 . 1  has to be submersed, this pumping is in full power, and no regulation and a screw pump part  1 . 2  is at full power, no regulation. 
         [0029]    The airflow from the top opening ( 1 . 8 )  FIG. 1  allows air to mix with liquid/mud pumped creating air bubbles. Thus density of the mixture is decreased and the head pressure decreased. This will result in less power requirements and load on the motor. 
         [0030]    Once the necessity of full airtight design is omitted the construction of the pump may be much lighter and cheaper to manufacture, which may significantly increase the ratio of power to size of the pump. 
         [0031]    The above-described embodiments of the invention are intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.