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Oil & Gas Automation
is a publication
of Unico, Inc.

Since 1967

Unico, Inc.
3725 Nicholson Rd.
P. O. Box 0505
Franksville, WI
262.504.7396 fax

New High-Output Engine Provides Compact Gas-Powered Lift Package

The new high-output 3.0 liter GM Vortec engine has been added to the Unico GPL™ Gas-Powered Lift product line. This unit operates artificial lift systems with a total power capacity of 60 hp (48 kW) at an engine speed of 2,400 rpm in a 42" by 42" by 55" package. The unit offers a nice extension to the 40 hp capacity of the 1.6 liter engine in similar compact package. Both units are configured to include up to four variable-speed drives for independent operation of ESP, PCP, or SRP artificial lift applications. To learn more about the GPL™ Gas-Powered Lift systems, please contact us.

Soft Landing Speed Profile Increases Sucker-Rod Pump Production

Sucker-rod pump production can generally be optimized by operating at partial pump fill percentages. Pump production for a full pump increases in proportion to pumping unit speed. As pump fill drops below 100%, fluid production increases with speed, but at a diminishing rate. Foamy fluid mixtures may require pump fill percentages as low as 60% to maximize oil production. The drawback of operating at reduced pump fills is that it causes fluid pound and associated rod stress.

Unico's Soft Landing Control feature reduces rod stress and associated damage without sacrificing pump production. The downstroke speed of the pumping unit is reduced until the plunger enters the fluid to soften the landing and then increased through the remainder of the pump stroke to maximize production.

Contact us for more information about soft landing speed profiling.

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SPE Paper Studies Production Increases at PDVSA

Production Increases at PDVSA Using an Improved SRP Control
is the title of a paper presented by Unico development engineer Ron Peterson at the 2006 SPE Annual Technical Conference and Exhibition held in San Antonio, Texas, September 24-27, 2006. Peterson prepared the paper with the cooperation of Alexander Gomez of Unico's Venezuela office and Carlos Brunings, SPE, and Wilfredo Quijada, SPE, of PDVSA. The abstract of the paper is given below. The full version of SPE 103157 can be purchased online from SPE.

"Sucker Rod Pumping (SRP) systems have used various control methods to optimize production, improve energy efficiency, and reduce maintenance. These systems typically use Rod Pump Controllers (RPCs) or timers to cycle the rod pumping unit on and off. Variable Speed Drives (VSDs) are occasionally used in conjunction with RPCs to improve operation by modulating pump speed. An improved SRP control that combines the RPC and VSD functions in an integrated system was installed on approximately 100 rod pumping systems at PDVSA starting in January 2004. The improved control resulted in a median production increase of 21%.

Embedded optimization controls in the VSD allow PDVSA engineers to preset a desired target pump fill based upon an Optimizer ID routine that samples production rates at various operating speeds and pump fill values over several days. The control subsequently adaptively modulates the pumping speed profile accordingly, thereby maintaining continuous operation at the identified optimal target pump fill. By maintaining a constant fluid level rather than the traditional cycling of fluid level between two limits, production losses associated with cycling above the target IPR well flowing pressure are eliminated. Furthermore, continuous and adaptive downhole pump speed controls allow the target IPR well flowing pressure to be reduced while simultaneously providing better protection for pumping equipment.

In addition, the VSD exercises the pump through controlled sequences that automatically identify other valuable system characteristics such as pump leakage, traveling/standing valve problems, pumping unit characteristics, counterbalance characteristics, and motor electrical parameters."

In Future Issues...

Look for the following articles in upcoming issues of Oil & Gas Automation Solutions:

Field tests of methods to eliminate rod pump gas locking and interference
Reducing power consumption and improving power factor of beam pumps
Using a torque economizer mode to improve efficiency and reduce gearbox stress
Detecting stick/slip oscillations that fatigue rod-string couplings and reduce energy efficiency of PCPs
Control options to ride through power disturbances

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