Andy Rosenholm Bubbletight LLC

1. Author: C. Andrew Rosenholm
Chief Technology Officer
Bubbletight, LLC - Needville, Texas USA
•June 6 - 7, 2017
•The Westin Galleria
•Houston, Texas
WEDNESDAY 11:00 – 11:30
DEGRADABLE POLYMERS AND
METALS FOR REFRACTURING

2. 2
USES FOR DEGRADABLE POLYMERS AND METALS IN WELL REFRACTURING:
• Restimulation of wells using degradable polymer particulate as temporary diverting agents
• Diverter (perf) balls to temporarily block existing perforations
• Frac plugs used when perforating new zones
• Drop balls for use with plugs and pre-existing seats

3. 3
Challenge to degradable adoption:
A major issue facing the makers and users of polymer and metal degradables in our current
economic environment is the availability and low-cost nature of coiled-tubing (CT) mill-out
services. In concert with cheap CT, low-cost - easy to drill composite frac plugs and balls
have taken a bite out of the market for downhole degradables.
Opportunities for degradable adoption:
Refrac opportunities have created new markets for degradables beyond the traditional uses
in fracturing.
The increasing prevalence of long lateral sections in wells has created a natural market for
degradable plugs and balls – it is difficult to mill out with CT in long laterals.
Whereas the market for degradable balls used in sliding-sleeve fracking has declined (plug
and perf is used on over 70% of US frac jobs), the market for lower-cost degradable plugs
(i.e.: polymer) is beginning to open up.
Interest in degradable polymers for alternative downhole tool components is on the rise as
tool designers discover uses for degradable polymers in frangible tool components.
Overview

4. Metal or Polymer?
Degradable metals:
• Primarily made from magnesium and/or
aluminum
• Generally require chlorides or acid in order to
degrade
• Degradation is accelerated with temperature
• Grades labeled “fresh water” react in an extreme
fashion in the presence of chlorides
• Exothermic degradation reaction consumes fluid
– lack of fluid can halt degradation
Degradable polymers:
• Generally rely on temperature to degrade
• Degradation is usually retarded with the
presence of chlorides
• The presence of acid may accelerate
degradation
• “Low-temp” and “high-temp” polymers
• Polymers can degrade better in fluid-
starved conditions than metals

5. Advantages of Degradable Polymers to Degradable Metals
1. Cost (lower)
2. Easily extruded into shapes
3. Easily machined into final form
4. Net-shape formable with injection molding, compression molding and casting
5. Degrade without the aid of chlorides or acids
6. There are seemingly endless numbers of polymers to design with
Disadvantages of Degradable Polymers to Degradable Metals
1. Strength (can be lower)
2. Tool designers are used to designing with metals and composites
3. IP Issues
4. Image issues (polymers have a lower perceived-value than metals)
5. Industry perception that polymers can leave behind non-degraded mass and “goo”
6. Degradation temperatures can be an issue for many types of polymers (too high or too low)
Pros and Cons of Polymers Versus Metals

6. Degradable Metals in Oil & Gas Downhole Applications
Frac Balls Frac Plugs
© Bubbletight, LLC, 2016 © Bubbletight, LLC, 2015

7. Physical Forms of Degradable Metals
Forging Extrusion Casting

8. Physical Manifestations of Metal Degradation - Mg
Magnesium degrades via an exothermic reaction – the temperature rises during degradation.
The products of the degradation process include hydrogen and ash.
© Bubbletight, LLC, 2016© Bubbletight, LLC, 2016© Bubbletight, LLC, 2016© Bubbletight, LLC, 2016

9. Physical Manifestations of Metal Degradation - Al
Aluminum degrades via an exothermic reaction – the temperature rises during
degradation. Aluminum degrades less readily than magnesium.
The products of the degradation process include hydrogen.
© Bubbletight, LLC, 2016

10. Physical Manifestations of Metal Degradation
© Bubbletight, LLC, 2016© Bubbletight, LLC, 2016© Bubbletight, LLC, 2016© Bubbletight, LLC, 2016

11. Applications include:
• Diverter polymer/chemicals
• Diverter balls
• Frac balls
• Frac plugs
• Frangible downhole tool components
• Well screen encapsulation
• Dissolvable pigs
Degradable Polymers, Elastomers and Thermosets in Oil & Gas Downhole Applications
Diverter Balls
Frac Plugs
Frac Balls
Sealing Elements Diverter Polymer
© Bubbletight, LLC, 2017
© Bubbletight, LLC, 2017
© Bubbletight, LLC, 2017
© Bubbletight, LLC, 2017
© Bubbletight, LLC, 2017

12. • Powder/flake/pellet: Diverter fluids/chemicals
• Fibers/monofilament: Diverter fluids/chemicals
• Extruded shapes: Cylinder, cruciform, etc. - diverter fluids/chemicals
• Spheres/balls: Diverter and frac balls
• Extruded rod and tube: Converted into downhole tool components
• Compression molded shapes: Thermoset sealing elements for downhole tools
• Injection molded shapes: Spheres/balls, downhole tool components
Physical Forms of Degradable Polymers; incl. Elastomers and Thermosets
© Bubbletight, LLC, 2017 © Bubbletight, LLC, 2017 © Bubbletight, LLC, 2017

13. Physical Manifestations of Polymer Degradation
Surface Erosion
• Sample is eroded from the surface
• Mass loss is faster than the ingress of water into the bulk
• Ablative
• Examples: Bubbletight patent-pending polymers and elastomers
Bulk Degradation
• Degradation takes place throughout the whole of the sample
• Ingress of water is faster than the rate of degradation
• Loss of physical properties
• Examples: PGA, PLA, PHA, PLGA, PCL
© Bubbletight, LLC, 2017
© Bubbletight, LLC, 2015

14. Diverter Polymer
Used to form a temporary “bridge” or plug in existing perforations
so that other perforations may be fractured/refractured. Must
degrade and self-remove after fracturing process
Types:
Rock Salt
Benzoic Acid Flakes
PLA
PGA
Proprietary: Divertol™

15. Diverter Polymer
Divertol™ Low-temperature Diverter Polymer
Mesh Distribution Sieve Opening μm
10-12 4% 1700~1400
12-14 8% 1400~1180
14-16 16% 1180~1000
16-30 56% 1000~500
30-42 9% 500~355
42-60 4% 355~250
60-83 2% 250~180
83-100 1% 180~150
0 0
25
40
50
60
70
90
100
0
10
20
30
40
50
60
70
80
90
100
0 50 100 150 200 250 300 350
PercentSolubuility
Temperature ° F
Divertol™ Low-temperature Diverter Polymer - Solubility /1 Hour
Exposure Fresh Water
Particle size and size distribution is important. Particles that are too large can foul a fracturing pump unit.
A broad distribution of particle sizes and shapes can maximize bridging effectiveness.
Degradation/solubility temperature and fluid compatibility is also important.
Sizing example:
Degradation/solubility temperature example:

16. Effect of Downhole Conditions on Polymer Degradation
Bottom Hole Temperature (BHT):
• Varies by shale formation
• Pump-down fluid generally at ambient temperature
• Shut-in duration is important
• Degradables generally fall into low- and high-temperature types
Fracturing fluid additives effect degradation:
• Acid
• Chlorides (KCl, NaCl)
Proppant can create a mechanical blockage with some degradable polymers

17. Fracturing Fluid Additives and their Effect on Degradation of Polymers
HCl Accelerates degradation for some but not all degradable polymers
KCl, NaCl retards degradation for most degradable polymers
Proppant can cause a sand-pack with some degradable polymers

18. Fracturing Fluid Composition

19. Shale Play BHT ° F
• Marcellus: 100-150
• Permian: 100-200
• Woodford: 150-225
• Barnett: 150
• Eagleford: 150-350
• Bakken: 190-240
• Haynesville: 280-380
Bottom-Hole-Temperatures (BHT) of US shale formations in °F

20. DCP™2X 3.3% NaCl Brine
DCP™2X Fresh
DCP™1X 3.3% NaCl Brine
DCP™1X Fresh
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
160° F 170° F 180° F
1% 4%
44%
11%
14%
59%
37%
61%
80%
84% 86%
95%
PERCENT WEIGHT LOSS - 24 HOURS
Bubbletight, LLC patent-pending polymers and
elastomers are specifically-formulated to
degrade in temperatures < 200° F
A serious, yet often unmentioned, concern
is the temperature needed for “degradable”
polymers to degrade or dissolve.
PGA reportedly needs approximately 30
days to degrade at 180° F and 10 days at
210° F.
Another commercialized degradable
polymer ball advertises that it will take 28
days for a Ø 3 ½” ball to fully degrade at
200° F
Bottom-Hole-Temperatures Are Often Less than 200°F
© Bubbletight, LLC, 2015
PLA Frac Ball Before and After 210° F Soak
© Bubbletight, LLC, 2017

21. Degradable Polymer Types:
Natural polymers: The polymers which are
obtained naturally are called natural polymers.
A natural polymer has its origin in plants and
animals
Synthetic polymers: The man-made polymers
or the polymers which are synthesized in the
laboratory are called synthetic polymers
• Polyhydroxyalkanoates (PHA)
• Poly(hydroxybutyrate) (PHB)
• Polylactic Acid (PLA)
• Chitin
• Collagen
• Gelatine
• Animal protein
• Starch
• Polyglycolic Acid (PGA)
• Polylactic Acid (PLA)
• DCP™ Degradable Composite Polymer
• DEP™ Degradable Elastomeric Polymer
• DDP™ Degradable Diverter Polymer
Thiol-Based Polymers
Hydrogels

22. Thiol-ene polymers are formed by the stoichiometric reaction of multi-functional enes with multifunctional thiols. The “thiol-ene” reaction
proceeds via a radical-mediated step-growth mechanism that can be initiated by light, peroxides, thermal initiators or any system whereby
radicals are generated.
Excerpt from: Thiol-X Chemistries in Polymers and Materials Science © The Royal Society of Chemistry 2013
The characteristic features of step-growth thiol-X reactions, such as excellent network uniformity and narrow thermal transitions as well as
their stoichiometric nature. Thiol-X network materials generally possess uniform structures with very narrow glass transitions. The ability to
prepare novel, advanced architecture polymers and perform site-specific functionalization reactions has been of significant interest in
polymer design and synthesis in recent years. The recognition and development of ‘click’ chemistry and other highly efficient coupling
chemistries has, in many instances, allowed polymer chemists to achieve these goals.
Excerpt from: Soft Matter, 2015 Sep 14;11(34):6852-8. doi: 10.1039/c5sm01260k. Epub 2015 Aug 3. Multiple shape memory polymers based on laminates formed from thiol-click chemistry based polymerizations. Podgórski M1, Wang
C, Bowman CN.
The thiol-ene reaction (also alkene hydrothiolation) is an organic reaction between a thiol and an alkene to form an alkyl sulfide. This reaction
was first reported in 1905, but it gained prominence in the late 1990s and early 2000s for its feasibility and wide range of applications. This
reaction is accepted as a click chemistry reaction given the reactions’ high yield, stereoselectivity, high rate, and thermodynamic driving
force. (Wikipedia)
Thiol-based polymers have been mentioned in at least one recent patent application where the thiol-based polymer is capable of at least
partially degrading in a wellbore, and the thiol-based polymer is selected from the group consisting of a thiol-ene reaction product, a thiol-yne
reaction product, a thiol-epoxy reaction product, and any combination thereof. The downhole tool claims wherein the thiol-based polymer
further comprises at least one of a degradable functional group comprising one or more of a degradable monomer, a degradable oligomer,
and a degradable polymer. Additionally, the thiol-based polymer has a glass transition temperature and exhibits a resilient characteristic
above the glass transition temperature and a rigid characteristic below the glass transition temperature, and wherein the downhole tool or
component thereof comprises the at least one thiol-based polymer having the resilient characteristic, the rigid characteristic, or any
combination thereof. (www.uspto.gov)
Thiol-Based Degradable Polymers

23. Hydrogel for use in downhole seal applications
US 20060278391 A1
The present invention is a composition for forming seals. The composition
includes a base material and a hydrogel. The base materials is preferably
an elastomer or a thermoplastic. Seals formed with the composition are
particularly suited for use in a wellbore environment. The inclusion of
hydrogel in the seals allows the seals to be manipulated or altered through
certain environmental factors. For instance, temperature, oil/water ratio, pH
and the electronic field may all be used to alter the characteristics of the
hydrogel. In this way, the seal may be caused to swell in response to a
specific stimulus, thereby preventing or sealing a leak without requiring
additional work or input from the operator. (uspto.gov)
A gel is a state of matter in between a solid and liquid. A gel is not a full
liquid because parts of the gel are insoluble in water, these parts give the
gel a certain amount of rigidity. A "hydrogel" is the popular term referring to
gels made out of water soluble polymers. In view of environmental and
physiological applications, hydrogels can be synthesized to be
biodegradable. Excerpt from: Michael Abiola Bajomo, MEng(Hons)
Supervisor: Dr A Bismarck, Dr Joachim Steinke (Department of Chemistry, Imperial College)
Sponsors: Faraday Plastics Partnership and Halliburton Energy Services
Imperial College – London
Smart Crosslinking of Water Soluble Polymers
Hydrogels
A hydrogel is a network of polymer chains that are hydrophilic, sometimes found as a colloidal gel in which water is the dispersion medium.
Hydrogels are highly absorbent (they can contain over 90% water) natural or synthetic polymeric networks. Hydrogels also possess a degree
of flexibility very similar to natural tissue, due to their significant water content. (Wikipedia)
Hydrogel of a superabsorbent polymer (Wikipedia)

24. Degradable Thermosets
A Thermosetting resin is a prepolymer in a soft solid or viscous liquid state that changes irreversibly into
an infusible, insoluble polymer network by curing – generally with heat.
Thermosets can be made “degradable” through the addition of degradable polymer or metal particulate or
through the use of a thermoset material susceptible to degradation through contact with hot water and/or
acids.

25. A major issue in the development of degradable downhole tools such as frac plugs has been the development of
degradable sealing elements (elements). By nature, rubber does not degrade well in water, and elements have
traditionally been made from NBR.
Approaches to making rubber degrade have generally included adding degradable polymers to the rubber.
The volume of research devoted to making rubber degrade in water has seemingly eclipsed the research done on rigid
degradable polymers, at least in the oil & gas field. See: Fig. 2: Degradable Polymers Claimed in Patents For Sealing
Element Use in Oil & Gas Downhole Applications A-Z
© Bubbletight, LLC, 2016
© Bubbletight, LLC, 2016
© Bubbletight, LLC, 2016
Degradable Sealing Elements

26. An alternative approach in manufacturing degradable
sealing elements is to develop a fully-degradable
elastomeric sealing element such as the patent-pending
DEP™ Degradable Elastomeric Polymer Bubbletight has
developed
Degradable Sealing Elements
© Bubbletight, LLC, 2016
The blending of brittle biopolymers with elastomers gives an option to create bio-based and/or biodegradable
materials with tailored properties. Similarly to starch, the improvement of the impact resistance of poly(lactic
acid) has been one of the main objectives of its modification by using several types of biopolymers such as
starch, polyurethane, natural rubber (NR), tough polyhydroxyalkanoate copolymers and polyesters including
poly(butylene succinate) and poly(ε-caprolactone).
Composition: Rubber + degradable polymer, degrades at 250° F +, Hardness 80 Shore A, Hardness 90
Shore A
Water-degradable elastomer:
Source: Kureha

27. Conclusions
Great opportunities exist for enhanced use of degradable materials:
• Broad range of degradable polymers and metals to choose from
• Plug and perf fracturing
• Refrac operations
• Long-lateral fracs
• Diverter polymer
• Other types of downhole tools
Know your downhole conditions when choosing a degradable material:
• BHT is important when choosing polymers
• BHT and chlorides important when choosing metals
• Desired time for degradation (time-on-seat, duration of frac, shut-in duration)
• Fracturing fluid additives affect degradation

28. C. Andrew Rosenholm
Chief Technology Officer
Bubbletight, LLC
P.O. Box 60
11726 Padon Road
Needville, Texas 77461 USA
andy@bubbletightusa.com
(979) 793-3377