American Oil and Gas Reporter - January 2016 - 99

The VRU Pro™ from Murphy by Enovation Controls is designed specifically for monitoring
and controlling the smaller-horsepower compressors used in vapor recovery operations.
Certified for Class I, Division 2 hazardous area operations, the controller is configured as a
flexible, off-the-shelf solution that requires no programming customization while enabling
advanced features such as automatic starting and speed/recycle/capacity control.

that enables the user to select from a number of preconfigured compressor equipment options using a tactile keypad and
backlit 3.8-inch monochrome LCD display. It features CAN J1939 engine communications with a closed-loop proportional integral derivative (PID) algorithm for
monitoring and control.
At its base functionality, VRU Pro uses
a transducer to monitor tank pressures and
automatically start and stop the compressor, according to Rodriguez. The
controller keeps the compressor in a
ready-to-start condition until tank pressure
reaches the preset level. At that point, it
starts the compressor to recover the vapors
and draw pressure back down to the set
point, when it then turns off the compressor.
However, depending on the type of
compressor and engine package, Rodriguez says the system has the optionality to facilitate a variety of advanced
control capabilities, including automatic
speed, recycle and capacity control through
three-way PID monitoring of suction/discharge pressures and engine loading.
"Not every compressor package has
these advanced control options, but the feature sets are built into the control panel and
are configurable by the user though the
keypad," Rodriguez remarks. "The controller uses PID to monitor and compare
a particular feedback such as suction/discharge pressure or motor current/manifold
pressure against a set point value. It continually calculates a correction factor to
keep key parameters at their set points to
maximize the performance of the entire vapor recovery system."

Gas Separation Systems
The vast majority of U.S. wells drilled
over the past few years yields multiphase
production streams. For artificial lift systems engineered to handle liquids, associated natural gas can lead to myriad gas
interference issues. That is where gas-assisted rod pump (GARP®) technology
comes in, states Daryl Mazzanti, president
of GARP Services LLC.

"GARP's main advantage is lifting liquids from below the pump to above it so
that the rod pump can remain in a pumpfriendly place in the wellbore," Mazzanti relates.
He adds that an important secondary
benefit is improving gas separation to overcome gas interference, which allows for
higher flow rates than with conventional
rod pump installations.
"Rod pumps cannot lift liquids from below the pump until they are above it; and
this causes a liquid column between the
rod pump and the reservoir that exerts back
pressure on the reservoir, which reduces
the flow rate," Mazzanti explains. "Instead,
though, GARP raises these liquids and allows them to enter the pump, while also
lowering back pressure on the reservoir by
reducing the density of the liquid column
above it."
Mazzanti says the GARP system comes
in two sizes: the original version designed for big-bore wells of 7-inch casing
or larger; and a newer, slim-hole version
1
designed for casing sizes 4 ⁄2 inches or larger. The latter has lower upfront costs
than previous versions, he says, and also
allows higher fluid production by incorporating a two-stage installation approach:
* The first stage, GARP Lite, is intended for newer wells that have sufficient
reservoir energy to lift liquids up a small
diameter concentric velocity string, which

GARP®

Rod Pump

Previous Lift Point

Dual Tbg Connector

Packer

350' - 1,000' TVD of Head Removal

Fracture

New GARP®
Lift Point

Gas-assisted rod pump (GARP®) technology overcomes gas interference to allow for
higher flow rates, and can lift liquids from below the pump to above it. GARP's two key
lifting components are a velocity string and a gas injection system that goes around
the rod pump to lift liquids from a well's lateral section.

JANUARY 2016 99
American Oil and Gas Reporter - January 2016

Table of Contents for the Digital Edition of American Oil and Gas Reporter - January 2016
