Abstract:
A method and apparatus for delivering treatment chemicals to an oil and gas well. A flush pump siphons flush from the production line of a producing well and draws in a predetermined amount of treatment chemical into the siphoned flush and then discharges the combination into the well.

Description:
RELATED APPLICATIONS 
     This application claims priority to Provisional Application Serial No. 60/144,598 filed Jul. 20, 1999 in the name of Billy Blanchard as inventor. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to the chemical treatment of wells that are in a state of production. In one aspect, the present invention relates to use of a pump that mixes the desired treatment chemicals with sufficient volume of flush from the well to carry the chemicals to the downhole equipment. 
     BACKGROUND OF THE INVENTION 
     Producing wells commonly have pumps and other equipment inside and towards the bottom of the well. This equipment is subject to corrosion, and chemicals are used to protect this downhole equipment. One common method of treating downhole equipment is by using “treater trucks” that travel from well to well to deliver the chemicals. Valving at the well site is changed and the treater truck recycles flush from the well through the well while adding chemicals into this recycling flush. When the treater truck is finished, the valving is changed back to its production position. The use of treater trucks is expensive. Additionally, they are unreliable as weather, unreliability of the operator, equipment malfunctions, etc. may disrupt the planned schedule for well treatment. Also, treater trucks are heavy and can damage the land owner&#39;s roads and property. There is also a safety risk with the human treater truck operators handling valves at the well site which if not handled properly could damage equipment. Relying on treater trucks is also disadvantageous because there are no chemicals treating the well in between the treater truck visits. 
     Another method of treating wells is using a chemical pump that is permanently at the well site injecting chemicals into the well casing. While this pump can continuously provide the chemicals, the volume of chemicals is very low. Whereas the treater trucks mixed the chemicals with the large volume of recycling flush from the well, the stand alone chemical pumps are typically small positive displacement pumps that inject small quantities of chemicals that may just “float” near the top of the well without traveling to the bottom of the well in sufficient quantities to treat the downhole equipment. 
     U.S. Pat. No. 4,375,833 to Meadows discloses the use of valving that is electronically changed periodically to recycle the flush from the well as the treater truck method does. Upon change to the recycling position, chemicals are injected into the recycling flush. The drawbacks of this method is that once again the chemicals are only treating the well periodically. Additionally, during recycling, the production of the well is off line. The valving and controls for this system are expensive and require maintenance. The Meadows patents also discloses the use of a rod pump that is used to deliver chemicals into the well either like discussed above or in combination with the valving disclosed in the Meadows patent. For example, during recycling, the rod pump delivers chemicals into to recycling flush. 
     A need exists for a device and method for low cost, low maintenance delivery of chemicals that will effectively treat the well. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method of introducing chemicals by a method for delivering treatment chemicals into a well by siphoning off a volume of flush from a production line of a well with a flush pump while the well remains in production and introducing treatment chemicals to the suction side of the flush pump to be combined with the flush. The combination of the treatment chemicals and flush is then discharged into the well by the flush pump. Another aspect of the present invention provides a flush pump for carrying out this method. Further aspects of the present invention combine the operation of a chemical pump on concert with the flush pump. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic representation of the method of the present Invention; 
     FIG. 2 is a side view of a pump jack with the pumping system of the present invention installed thereon; 
     FIG. 3 is a side view and partial cross section of the pumping system of the present invention; 
     FIG. 4 is a side view of the top of the pumping system of the present invention; 
     FIG. 5 is a side view of an alternative embodiment of the present invention with a tandem chemical pump and flush pump; 
     FIG. 6 is a cross-section view of the tandem chemical pump of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIGS. 1-3, the preferred method and apparatus of the present invention will be described. FIG. 1 schematically represents the method of the present invention. Well  10  produces fluid (oil, gas, water, or mixture thereof) through production line  12 . Flush pump  14  has suction end  16  in communication with production line  12  such that a portion of the production fluid, or flush, is siphoned off into pump  14 . Chemical pump  18  injects treatment chemicals into suction end  16  to mix with the flush. The combination of the treatment chemicals and the flush are then discharged through discharge end  20  of pump  14  which is in communication with well  10 . Due to the additional volume of the flush siphoned from production line  12 , the treatment chemicals will be able to reach the bottom of well  10  to treat downhole equipment and formation. 
     FIG. 2 shows flush pump  14  installed on pump jack  22 . Flush pump  14  is preferably a type of rod pump which is known in the art. Flush pump  14  has rod  24  that is attached to walking beam  26  of pump jack  22  at top mount  27 . As walking beam  26  travels, the other end of rod  24  is reciprocated within pump housing  28  which is mounted to base  30  of pump jack  22 . With reference to FIG. 3, rod  24  terminates inside housing  28  with plunger  32  with mixing head  34 . As plunger  32  reciprocates, flush from production line  12  is drawn through inlet ball valve  36  and into suction end  16 . Also treatment chemicals from chemical pump  18  are drawn through valve  38  into suction end  16 . The amount of treatment chemicals drawn per stroke is preferably controlled by controlling the discharge of the chemical pump. The amount of flush drawn per stroke is a function of the internal volume of flush pump  14 . By sizing the flush pump and controlling the chemical pump, the desired amount of chemicals per volume of flush can be achieved. Flush and treatment chemicals are drawn into flush pump  14  on the upstroke of plunger  32 . On the downstroke, mixing head  34  mixes the chemicals with the flush by virtue of the two fluids being forced through grooves  40  on the outer surface of mixing head  34 . Inlet ball valve  36  prevents any back flow of flush into production line  12  and valve  38  prevents back flow of chemicals into chemical pump  18 . On the downstroke, plunger  32  displaces the treatment chemicals and flush through outlet ball valve  42  at discharge end  20  of flush pump  14 . As can be seen, flush pump  14  is driven by the walking beam of the pump jack so pump  14  continuously delivers treatment chemicals with a sufficient volume of flush to carry the treatment chemicals downhole. Rod  24  also reciprocates through packing box  41  which helps seal against fluid leaking out of housing  28  around rod  24 . 
     With reference to FIG. 4, a safety feature of the present invention is shown. Break away sub  50  is connected in line between rod  24  and plunger  32 . Should the pressure inside housing  28  exceed a set maximum, break away sub  50  is designed to break before the excessive pressure damages flush pump  14  or interferes with pump jack  22 . 
     With reference to FIG. 5, an alternative embodiment of the present invention is shown where chemical pump  60  is a rod pump for delivery of treatment chemicals into suction end  16  of flush pump  14 . Chemical pump  60  is mounted in tandem with flush pump  14  by rod mount  62  and bracket  63  which couples rod  64  of chemical pump  60  to plunger  32  of flush pump  14  in a spaced apart parallel relationship. As such, rod  64  reciprocates together with plunger  32 . In this way, walking beam  26  is used to power both the flush pump and the chemical pump. 
     With reference to FIG. 6, a more detailed view of chemical pump  60  is shown. Plunger  66  has flange  68  which is biased against shoulder  70  of housing  72  by spring  74 . On the up stroke, chemical is drawn through inlet ball valve  76  and on the down stroke the chemicals are discharged through outlet ball valve  78 . This coordinates with flush pump  14 . 
     It can be appreciated that treatment chemicals can be delivered to suction end  16  of flush pump  14  without a chemical pump, for example, a metering device place between suction end  16  and a source for the treatment chemicals. Regardless of how the chemicals are introduced into flush pump  14 , they are mixed with a significant volume of flush without interrupting the production of well  10  and then discharged into the well. The volume of flush is sufficient to carry the treatment chemicals down the well.