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Magazine: World Oil
Publish Date: APRIL 2008

WHAT'S NEW IN ARTIFICIAL LIFT
Recent developments are introduced in three major artificial lift categories:

sucker rod pumping, progressing cavity pumping and gas lift. Described here are 19 recent downhole and surface equipment developments from 13 companies. Part 2, in May, will introduce developments in Electrical Submersible Pumping (ESP) and other miscellaneous new artificiallift applications. Sucker rod pumping has, in many cases, evolved from classicbeam pumps to include tower-typeunits. It is the most widely used form of artificial lift, usually involving the application of vertical rod motions, but now also cable, to operate a downhole reciprocating pump. New technologies have focused on increasing downhole pump life and efficiencies, and on prevention of sand wear. Progressing Cavity Pump (PCP) systems are based on asurfacedrive rotating arod string, which drivesadownhole pump rotor operating within an elastomeric stator. Gas well deliquefying is the removal of liquid covering the producing formation to increase gas production. Gas lift usesdownhole valvesto inject annulus gasinto the tubing under liquid columns, or under optional plungers, to reduce column density and drive liquids to surface.

SUCKER ROD PUMPING
Eleven recent technology advances introduce improved downhole systems and operational controllers. Downhole plunger. The new Farr downhole rod-pump plunger from Bakersfield, Calif.-based Muth Pump has a unique design change that allows it to pump sand, coal fines and all other solids without sticking the plunger in the pump barrel, and keeps those abrasivesolids from prematurely wearing out the pump. Figure 1 shows a side-by-side comparison of the Farr plunger vs. a conventional API plunger. The plunger connector (or bushing in the API plunger) is moved from the top of the API plunger to the bottom in the new plunger. This one simple move made a great difference in downhole rod pumping. In the API plunger, the top connector or bushing is 0.060 in. smaller than the plunger, leaving a gap at the top between the connector and the pump barrel. This gap allows solids to be forced down and outward into the gap as the plunger moves up; this further allows the solids to get betWeenplunger and pump barrel, thus wearing out the metal surfacesand/ or sticking the plunger. Moving the connector to the bottom of the Farr plunger and tapering the top inward eliminates these problems. Solids are forced inward to catch the fluid stream going up, keeping them out of the gap.

ROD PUMP CONTROLLER
In the past, operators chose between load-and-position sensors and amperage modulation to controlrod pump wells. Conventional Rod Pump Controllers (RPCs) used load and position to determine when to turn a well on or off, while Variable-Speed Drives (VSDs) used amperage modulation to vary motor speed. Weatherford's new WellPilot controller offers the best of both options as it combines the accuracyofload-andposition measurement with the precision of a VSD. The new controller uses continuous load-and-position indications to calculate pump fill correctly. The variablespeed control then slows or speeds up the pump motor to maintain the optimal level in the annulus. This minimizes backpressure on the reservoir, allowing maximum flow. It also preventS the fluid level from falling to the pumped-off level, where pump wear and damage are accelerated. Combining conventional RPC and variable-speed technologies ensures that the well...

 

Magazine: JPT Tech Apps.
Publish Date: November 2006

Downhole Rod Pump-Muth Pump LLC is replacing conventional sucker- rod-pump plungers with a new design. Solids (e.g.,sand and coal fines) have plagued downhole pumps. The Farr plunger reduces plunger wear to reduce the chance of sandentry sticking the plunger in the barrel. Generally, conventional plungers have a 0.002- to 0.003-in. clearance between the plunger and the pump-barrel wall. However, the rod connector at the top of the plunger has a 0.06-in. clearance. This mgap at the top of the plunger causes most of the problems associated with conventional plungers. As the plunger starts its upward movement, sand is forced outward into the gap because of the shape of the connector. When the well is shut in, even for a short period of time, sand will settle out and fall on top of the plunger connector. When the well is placed back on production and the plunger starts its upward movement, sand is wedged into the gap, sticking the plunger inside the pump barrel. In the Farr plunger, the connector was moved from the top to the bottom of the plunger(Fig. 2), which eliminated the 0.06-in. gap between the connector and the pump barrel at the top of the plunger. The angle at the top of the plunger was reversed to force sand inward. This new design allows sand to be pumped out of the wellbore with the fluid, thus reducing instances of sticking the pump with sand.