Solids Handling Capabilities of  HDESP Pumps

Oil and Gas wells typically give up solids as a normal part of fluid production.  The solids can come from one of three sources 1)  formation solids such as coal fines and formation sand 2)  Solids introduced for completion such as mud solids and propents, and 3) By-products of chemical reactions, normally scale, paraffin and rust.  The production of solids can negatively effect the well pump by either interfering with the pumping mechanism or by clogging fluid passages leading from the pump to the surface.  Solids are generally not a problem unless the solids content exceeds 1000 ppm by weight.  If the solids concentration is higher then the critical level, then the well can still be pumped using a HDESP, but special operational procedures must be used. 

Direct interference with the pumping mechanism is rarely a problem.  The only exception is in pumps operating at flow rates of less then 100 BFPD, where direct interference has been reported in rare cases.  Contact SmithLift for guidance when operating in high solids conditions at very low flow rates.  The diaphragm pumping mechanism is immune from abrasive wear due to the non-contact nature of the pump, but balls and seats will experience rapid wear in some high sand conditions, in a manner similar to a rod pump ball and seat. 

Solids plugging is a potential problem is some operating environments.   In most cases, the plugging occurs around the ball and seat, check valve, or lower end of the tubing string.  Gravity causes the solids swept into the production fluid to drop out of the fluid when the upward velocity drops below a critical value.  In general, 1 ft/sec is required to sweep light solids to the surface.  Problems will occur if the following operational procedures are used:

1)      Tubing diameters are too large such that critical velocity is not achieved

2)      The pump is started and stopped when solids loads are larger then 0.5% (5000 ppm)  This allows the sand to settle on top of the pump and/or check valve, to the point where it cannot be swept out on the next pump restart.  Higher concentrations can be handled with smaller tubing.

3)      The pump is cycled, and the on portion of the cycle is insufficient to sweep accumulated solids to the surface.  In general, the pump output should be at least two times the tubing volume above the pump.

4)      Intake or Outlet is positioned directly in the path of falling solids that are too heavy to be pumped out of the well.  This is most often a problem where tubing rust settles on top of the pump.

5)      Solids have the tendency to aggregate into larger solids.  Scale, paraffin, and tar mixed with sand are the usual culprits.  Chemical treatment is the most common solution to these problems.

In some cases, changes to the operational procedures are not possible, or the solids concentrations and/or type of solids are such that the problem cannot be mitigated by changing the procedures.  In such cases, solids problems may occur.  HDESP’s can still be used if the solids are screened out or removed from the fluid stream.  Various screens, gravel packs and filters, as well as bailing have been used for solids mitigation.