American Oil and Gas Reporter - February 2018 - 44

SpecialReport: Multiphase Oil Recovery
nents are sent by pipeline to a central facility for storage."
Those central facilities use a heater
treater system to stabilize the oil as it
comes in. Although stabilization reduces
the amount of gas that flashes as the oil
moves from high to low pressure, Conder
says enough comes off that heater treater
systems are equipped with intermediatepressure vapor recovery units (VRUs).
The oil from the heater treater systems
goes to a vapor recovery tower (VRT),
which captures much of the flash gas. Finally, it is sent to storage tanks equipped
with a vapor control system designed to
capture any remaining gas vapors. Conder
says these vapors can be sent to an emissions
control device (ECD), which burns the gas
in a way that minimizes emissions.
"Colorado requires that we design our
storage tanks and vapor control systems
in such a way as to eliminate leaks and
minimize emissions outside of the ECD,"
he says. "In other words, we have to
design for the worst case of potential instantaneous flash gas production at the
tanks."
To handle those peak flash gas volumes,
Conder says operators use robust ECDs
and large pipe systems. To minimize the
cost, he indicates that many operators are
moving toward larger ECDs. "In the past,
we might have put in a dozen 500-barrel
tanks that were each hooked up to an
ECD with a four-foot diameter," he relates.
"Today, operators are connecting multiple
tanks to single ECDs with eight-, 12- and
even 16-foot diameters, which reduces
the footprint and could simplify maintenance."
Conder adds that local operators are
experimenting with improvements to their
VRTs. "Paraffin forms as the oil cools in
the towers, so periodically they may need
to be taken off line for hot oiling. To
slow the cooling and paraffin formation,
operators are looking at insulating the
towers."
Operators also may be able to reduce
paraffin formation by shortening residence
times. In areas with multiple VRTs,
Conder says operators may be able to
achieve that goal by channeling all the
oil into one unit. "The residence times
are intended to break emulsions, but be44 THE AMERICAN OIL & GAS REPORTER

cause the oil goes through a heater treater
before it reaches the VRT, those rarely
are a problem," he comments.
In fact, Conder says it may be possible
to eliminate VRTs altogether by running
a heater treater at a low pressure, comparable to a VRT's, such as two or three
psi, and allowing the heater treater's VRU
to handle the gas that comes off. Then
the now largely gas-free oil could be
pumped into the tanks.
Tankless Designs
Because tanks offer several ways for
emissions to escape to the atmosphere,
Conder reports operators are looking for
ways to bypass them by going directly
from heater treaters to the sales line. In
areas without pipeline infrastructure, he
recommends installing lease automatic
custody transfer (LACT) units.
"Almost all of our sites use LACTs
for load-out," he comments. "They improve safety by eliminating the need for
someone to climb the tanks when there's
snow on the stairs, reduce emissions by
eliminating the need to open thief hatches
and cut the chance of a spill."
Conder points out LACT units have
economic benefits beyond improved safety.
"Before LACT units, a hauler might
spend 90 minutes on site, with half an
hour spent hooking up and another 1020 minutes spent testing the loads and
occasionally grinding them to see if they
contain water. The LACT unit handles
all of that automatically, so the hauler
can get in and out in less than an hour.
As a result, he charges us less."
Conder suggests using LACTs with
Coriolis meters, explaining the devices
offer greater accuracy. Because LACT
units improve efficiency and safety, he
says local trucking companies are fitting
some of their trucks with LACT units to
serve smaller pads that do not have their
own.
Conder says Bonanza is benefiting
from automation on tanks and other equipment. "With automated monitoring, our
pumpers can focus on pads that need attention rather than checking every pad
every day (though we do check them on
a regular schedule). The reduced wind-

shield time enables pumpers to concentrate
on fixing problems and gives them time
to cross-train and pick up new skills."
Electric VRUs
Returning to vapor recovery, Conder
reports that Bonanza is switching from
gas-driven VRUs to units powered by
electricity. "The electric VRUs reduce
downtime from 10-15 percent down to 5
percent or less," he says. "To get the
downtime even lower, we may install
backup units. Less downtime reduces
VOC emissions, which means we can
handle more oil at one of our centralized
storage locations without passing emission
thresholds that activate more complicated
permitting regimes."
Conder says the amount of oil each
storage facility can process has gone
up tremendously. "Four or five years
ago, companies in the area pioneered
central facilities that could handle 5,0006,000 bbl/d, limited in part to VOC
emission permits. Improvements that
greatly reduce VOC emissions are supporting designs that can process much
more, with fewer calculated emissions
than earlier designs. This is a testament
to the industry's experience in operating
these facilities and subsequent improvements in facility design."
In addition to simplifying emissions
control, Conder says sending production
from multiple pads to a central facility
makes gas lift more economic. "When I
joined Bonanza Creek five years ago, I
never would have imagined that we would
have wells on gas lift for more than a
year," he recalls. "We have wells that
have been on gas lift since before I came.
"The key is that we have changed
from putting small, 200-horsepower compressors on each well to centralizing
gas lift and using an 800 horsepower-or
larger-compressor to serve several wells,"
Conder says. "It is easier to maintain
two or three high-horsepower compressors in one location than it is to keep 20
small, widely distributed compressors
running, so our uptime has improved.
The change has cut gas lift compression
costs in half, allowing Bonanza to extend
the gas lift window by injecting gas at
higher pressures."
American Oil and Gas Reporter - February 2018

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