American Oil and Gas Reporter - August 2015 - 83

SpecialReport: Hydraulic Fracturing Technology

This degradable frac ball is made
from a composite polymer with
exceptional tensile strength.
Manufacturer Bubbletight says
similar polymer technology is
enabling completely degradable
frac plugs, diverter balls and diversion powders that are reliable
and effective.

Elongation and shear are also important.
If the shear strength is too low, as the
ball is forced onto the seat, the seat will
shear a ring off the ball's diameter and
cause it to pass through."
Tensile strength generally correlates
with all three qualities, but there are materials that have a high tensile strength
but poor downhole performance, Rosenholm warns. He says the characteristics
an operator should look for will depend
partly on the application. "In a hot environment, the operator may want a product
with a high modulus, because it may
soften less quickly," he illustrates.
For plugs, ductility/malleability and
compression strength can be important,
Rosenholm says. He recommends operators also look at the plugs' sealing elements.
"To date, the Achilles' heel of degradable plugs has been the elastomeric sealing
element. No one has yet come up with
an elastomer that degrades quickly enough
to be practical," he says. "In many cases,
the elastomers are degradable, but the
degradation may take two years."
To provide faster degradation, Bubbletight has developed a sealing element
made from a version of the plastic used
to make DCP. "We can tailor the material
to degrade anywhere from a day to a
month, and the material can be molded
and extruded net-shape," Rosenholm reports.
For high-temperature or high-pressure
applications, Rosenholm recommends using a metal-based degradable. "Good
degradable metals cost more than polymers, but they do not soften and deflect
as quickly, so they have better perform-

ance," he explains.
Bubbletight manufactures degradable
composite metals (DCM), which Rosenholm says are stronger than degradable
alloys or cast products. "Our unique manufacturing process allows magnesium
and other reactive elements to be combined
without being re-melted. As a result, the
DCM material has superior strength without compromising the degradation characteristics of the reactive elements," he
relates.
Subsea System
The Lower Tertiary Wilcox trend in
the Gulf of Mexico holds great promise,
but to tap it, operators need completion

systems capable of withstanding extreme
pressures and temperatures. Baker Hughes
says it is meeting that need with an ultradeepwater integrated completion and production system. The company points out
that it developed the system in only three
years by forming an integrated, 95-person
team and using a Six Sigma design
process.
The process started with research to
gain an in-depth understanding of customer
requirements, recalls Robbie Pateder, the
team's senior director. "We gathered information from customers and consulted
with Baker Hughes' reservoir development
services team to build the basis of design
for what the completion system had to
do," he says.
"From that research, we knew the system would need to withstand bottomhole pressures as high as 25,000 psi and
temperatures as great as 300 degrees
Fahrenheit," he relates. "In addition, each
well in the play would cost at least $400
million, so we had to deliver production
and recovery rates high enough to make
that investment worthwhile. Because the
target formations had extremely low permeabilities and porosities, the system
would need to deliver unprecedented
treatment and stimulation programs.
"We wanted it to be able to deliver 5
million pounds of proppant and pump
fluid at up to 50 barrels a minute to
address these formations," Pateder adds.
With development costs being so high,
the system had to improve the net present
value of these projects significantly, Pateder

After three years, a 95-person product development team at Baker Hughes has introduced an integrated subsea completion system for the ultradeepwater Lower Tertiary
Wilcox trend in the Gulf of Mexico. According to the company, the system offers completion and reservoir management capabilities that will enable operators to maximize
the value of each well.

AUGUST 2015 83

American Oil and Gas Reporter - August 2015

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