American Oil and Gas Reporter - February 2017 - 75

SpecialReport: Enhanced Oil Recovery
and provide stable measurement over extensive service periods.
Effective validation through proving
operations (pipe provers, compact provers,
etc.) will ensure ongoing meter accountability while the advanced in situ diagnostics available for Coriolis meters help
identify abnormal events that compromise
measurement between validations. LACT
units usually are installed in remote locations, and are almost always unmanned.
Consequently, it is important to have remote accessibility to all data and operating
conditions.
Operators ask themselves when it may
make economic sense to invest in a LACT
unit versus manual or automated tank
gauging. Many install LACT units only
when a field exceeds a company's standard
production rate to reduce fiscal measurement uncertainty and help automate larger
volume transfers.
As noted, a typical LACT system has
the capability of ±0.25 percent accuracy.
By comparing that with manual gauging,
an operator can determine the amount of
fiscal exposure and production rates versus
the time it would take to pay for a LACT
unit installation.
Note that while a 1 percent error was
used in Figure 1, operators have reported
significantly higher error percentages in
manual gauging accuracy. Other considerations not included in the calculation
are the cost associated with manual operations and measurements that also can

justify installing a LACT unit.
Another option with the addition of
API Ch. 18.2 is a truck-based LACT system (Figure 2). Truck-based LACT systems can reduce the capital cost of permanent, skid-based LACT systems, but
are subject to potential damage caused
by traveling on oil field roads. It is critical
that any truck-based system be maintained
and inspected properly to ensure measurement accuracy.
Automation Systems
No matter which method of custody
transfer is chosen, all instruments and
diagnostics can be brought into a central
controller or remote terminal unit (RTU)
for remote access or direct access on
site. Human/machine interfaces can be
used to automate haul transactions using
manual or automatic tank gauging, or
LACT-based systems.
Integrating functionality into automated
production management and tank management programs has proven to eliminate
issues around production measurement
compliance, and has minimized lost-andunaccounted-for production.
Marathon Oil Corp. has reported saving
nearly $15 million by formalizing and
automating metering at its production
tanks. Better insight and early identification
of uncertainties can help contain ownership
costs and reduce fiscal risk. Solutions
for remote operations include flow computers and RTU platforms with flexible

software applications and supervisory
control, and data acquisition systems to
monitor the process of fluid transportation
(Figure 3).
Applying wired or wireless automatic
tank gauging technology, such as guided-wave radar for continuous level monitoring, improves production management
by enhancing operations. Continuous insights into actual inventory levels help
prevent reactive operator events associated
with high-level alarms, well shut-ins, or
a tank overfill situation. Oil losses to
water storage tanks and diminished storage
capacity because of excessive water levels
in oil tanks are minimized through detecting oil/water interface.
With the publication of API MPMS
Ch. 18.2, there now is an industry-acceptable path that uses guided-wave radar
for crude oil custody transfer from small
lease tanks. Where economical, installing
a LACT-based custody transfer system
can pay for itself with reduced measurement uncertainty and better use of labor.
With the addition of API Ch. 18.2, many
operators also are implementing truckbased LACT systems that reduce the
capital cost of flow measurement-based
systems.
Leveraging automation systems and
standards-based applications for well pad
tank management has the added benefit
of bringing all the measurement systems
together to maximize overall efficiency
and reduce fiscal risk.
❒

FIGURE 3
Well Pad Tank Management Haul Interface
Remote operation
control system with
user-deﬁned displays

MICHAEL
MACHUCA

1. Operations display
2. Driver
3. Open edit
4. Fluid characteristics
5. Haul details
6. Haul ticket

Conﬁgurable to ﬁeld
operations

Michael Machuca is director of
North American upstream oil and gas
marketing at Emerson Process Management. He has been with the company since 2005, helping to implement
Emerson solutions in oil and gas applications. Prior to joining Emerson,
Machuca worked for seven years designing oil field equipment, mostly for
subsea applications. He holds a B.S.
in mechanical engineering from the
University of Houston.
FEBRUARY 2017 75

American Oil and Gas Reporter - February 2017

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