Patent Publication Number: US-7900695-B2

Title: Well pump device

Description:
This invention regards a well pump for use in a subsurface well. In particular, it regards a well pump comprising a feed pump that delivers driving fluid to an ejector (jet pump), and where the ejector is, directly or indirectly, especially suited for use during servicing operations in a subsurface well. 
     When carrying out service work in a subsurface well it is sometimes necessary to assist the production up to a normal level from a relatively low pressure well, or to carry out pulling operations in the well. 
     According to prior art it is customary when starting up production from a killed well, to move coiled tubing into the well and then pump gas such as nitrogen down via the coiled tubing and thereby reduce the static pressure in the well. In many cases, pulling operations are also carried out by use of coiled tubing. 
     Coiled tubing operations of this type are relatively time consuming and costly. 
     The object of the invention is to remedy or reduce at least one of the disadvantages of prior art. 
     The object is achieved in accordance with the invention, by the characteristics stated in the description below and in the following claims. 
     A well pump comprising an electrically driven feed pump and an ejector is placed in a well near the site of operation. The feed pump is connected to a wireline and receives electrical energy via a line from the surface. The feed pump pumps well fluid from the well pump surroundings to the driving side of an ejector. The main outlet from the ejector is connected to an auxiliary apparatus and delivers fluid to the well pump surroundings. 
     When utilization the well pump in a start up operation in a well, the auxiliary apparatus comprises an inlet pipe to the ejector, the inlet pipe being provided with a packing. The packing is arranged to seal an annulus between the inlet pipe and the wall or the casing of the well. 
     When initiating or stimulating production from a well, the feed pump that drives the ejector is started up, thereby causing fluid to flow from the well formation via the inlet pipe and the ejector, through a pressure increase in the ejector, past the sealing packing and on up to the surface. The ejector is relatively insensitive to contaminants in the well fluid. 
     In another embodiment in which the well pump is used as a pulling tool, the well pump is provided with an auxiliary apparatus comprising a hydraulic cylinder with a piston and a piston rod. The upper cylinder chamber of the cylinder is connected to the ejector inlet. When the ejector reduces the pressure in the upper cylinder chamber the piston and piston rod are displaced upwards, the static pressure in the well acting on the underside of the piston. 
     The piston rod is attached to an object to be pulled. Starting and stopping the feed pump will make the pulling tool repeat the pulling operation. 
     The well pump with the auxiliary apparatus is also well suited for transport into the well by means of e.g. a well tractor. 
    
    
     
       The following describes a non-limiting example of a preferred embodiment illustrated in the accompanying drawings, in which: 
         FIG. 1  shows a well pump with a connected inlet pipe and packing in a well, with arrows indicating fluid flow paths; and 
         FIG. 2  shows the well pump with a connected pulling cylinder. 
     
    
    
     In the drawings, reference number  1  denotes a well pump comprising a feed pump  2  and an ejector  4 . The well pump  1  is connected to the lower end portion of a wireline  6  and is arranged in a well  8 . There is an annulus  10  between the casing  12  of the well  8  and the well pump  1 . 
     The feed pump  2 , which receives electrical energy from the surface via a line  14 , is fed with fluid from the annulus  10  via feed openings  16 . From the feed pump  2 , the fluid flows via an inlet passage (not shown) to the driving side of the ejector  4 . 
       FIG. 1  shows the well pump connected to an inlet pipe  18  which is fitted with an external packing  20  that seals against the casing  12 . 
     The production from the well  8  can be enhanced by well fluid flowing in through the inlet pipe  18 , through the ejector  4  and out into the annulus  10  via an outlet  22 . 
     The ejector  4  aids in reducing the pressure below the packing  20  in the well casing, whereby the inflow to the casing  12  is stimulated. 
     In another embodiment, see  FIG. 2 , the well pump is connected to a hydraulic cylinder  26  provided with a sealing piston  28  and a piston rod  30 . Together, the well pump  1  and the cylinder  26  form a downhole pulling tool  32 . 
     During pulling operations, the pulling tool  32  is held in the well by a shoulder  34  or a tie bolt  36 . 
     When pulling an object  38  connected to the piston  30 , the pressure in the upper chamber  40  of the cylinder  26  is reduced by the well pump  1 , the upper chamber  40  communicating with the ejector  4 . The static pressure in the well  8  acts in the lower chamber  42  of the cylinder  26  and against the underside of the piston  28  via openings  44  in the wall of the cylinder  26 , causing the piston  28  and thus the piston rod  30  and the object  38  to be displaced upwards.