American Oil and Gas Reporter - February 2019 - 90

SpecialReport: Offshore & Subsea Technology
FIGURE 2
Integrated 200-Barrel Subsea Chemical Storage and Injection System
Pressurecompensated
steel tank
(secondary)

Water-Tight Tank
Annulus to Fill with Water
As Bladder Depletes
50 Ton Padeyes

All-electric valve
actuator

9'x9'x40' ISO Frame

SMarT™ Valve
Actuator

ROV Valve Buckets
200 bbl
Double Barrier
Chemical Storage

Control Panel

10-ksi (initial) variable speed
electric injection pump

Bladder

Safe-Ject™ (Chemical Indection Unit)
SMarT™ Pump

U.S. Pat. 9,656,801

shipping container. Without a chemical
load, the unit is transportable by road,
which considerably simplifies logistics.
It can be installed with a conventional
offshore multiservice vessel (MSV). The
in-air weight of the 200-barrel unit is approximately 55 tons. While the deck
weight/space savings are much lower
than the 3,000-barrel barge, placing the
unit on the seafloor immediately adjacent
to a shallow water platform reduces manning requirements since the unit can be
operated remotely.
As an additional improvement to the
subsea injection system, the 200-barrel
system is designed to be all-electric, with
the advantages of avoiding a separate
hydraulic system and the opportunity to
use advanced "health monitoring" to determine pump and valve conditions.
The current design for production
chemical storage and injection includes:
· Usable storage capacity of 200 barrels with dual-barrier containment of one
chemical (or mixture);
· Suitability for installation/recovery
by a standard MSV;
· The capability to operate for as
long as five years subsea, with a design
life of 10 years;
· 10,000/15,000 psi injection pressure
and 10,000-foot water depth ratings;
· All-electric controls and pumps;
· A design that allows for suction
pile or mud mat foundations;
· A cost-effective "design one, build
many" philosophy; and
· Connection to a subsea injection
point or unmanned platform though conventional flying leads using a remotely
operated vehicle.
90 THE AMERICAN OIL & GAS REPORTER

Chemical/fabric
qualified storage
bladder (primary)

As noted, both the 3,000-barrel barge
and the 200-barrel systems store the
chemical inside a dual-barrier containment
system. This patented system utilizes an
engineered fabric as the first or primary
barrier and a steel hold or steel tank as a
secondary barrier in the event of any
failure of the primary barrier.
For the 200-barrel system, the design
philosophy includes performing any inspection, maintenance or repair work at
quayside. The five-year subsea service
life lowers initial costs when compared
with a traditional 20- or 25-year subsea
service life. With the "repair at quayside"
philosophy, the 200-barrel units can be
upgraded easily if early experience yields
significant design improvements, or if
changes are needed in the chemical treatment program.
Technology Step-Outs
The 200-barrel system incorporates

technology step-outs in three key areas:
engineered fabric as a primary containment
for production chemicals, a high-pressure
subsea chemical injection pump, and electric valve actuators and pump drivers.
All three areas have been the focus of
targeted technology qualification efforts.
The storage bladder configuration was
selected in conceptual design work that
evaluated many options. The selected
configuration for the storage bladder then
was subjected to scale-model testing, as
illustrated in Figure 3.
The compatibility between the stored
chemical and the bladder fabric creates
an important design issue. The chemical
storage bladders are fabricated from chemically resistant engineered fabric materials.
To confirm this compatibility, independent
third-party laboratory confirmation/testing
has been performed for several typical
production chemicals. A qualification
procedure, needed for different sitespecific chemicals that have not yet been
tested, also has been developed with input
from numerous industry subject matter
experts.
Future plans for the 200-barrel system
include completing all pump and actuator
qualification testing, fabricating a complete
unit, conducting in-water system integration testing, and offshore field demonstration. The pump and actuator tests are
well advanced and on course for completion in a few months (Figure 4).
Plans call for system integration testing
to be performed in an onshore, in-water
test tank near Houston. Integration testing
is anticipated to be complete by late

FIGURE 3
Bladder Conﬁguration Testing
Testing Results
*

Bladder behavior was
consistent, predictable &
repeatable

Able to achieve very low
chemical residuals after
pump-down

No observed detrimental
bladder material behavior

Over 30 SME participants + regulators
witnessed model test/demonstration

American Oil and Gas Reporter - February 2019

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