C. Andrew Rosenholm, President / Owner

Rockwell Oil and Gas Tool Salescar@rockwelloil.com

Energy Rubber Group, Inc.

2014 Winter Technical Meeting

WATER-DISSOLVABLE POLYMERS FOR USE IN MANUFACTURING FRAC BALLS, SEATS AND PLUGS

Examples of degradable polymers in use today:

SuturesTacksBone anchorsGolf teesFlatwareBagsFoam packaging

Why use water-dissolvable polymers downhole?

Main reason: To avoid costly mill-outs

Remnants of tools (balls, plugs, seats) will dissolve over time, increasing product flow and production

Q: Why aren’t degradable plastics more prevalent downhole?

A: Most degradable plastics lack the tensile strength necessary to hold up to the high pressures used in fracking < 15,000 PSI

DOWNHOLE TOOLS ARE SUBJECTED TO EXTREME PRESSURES!

Fig. 1: Frac ball on seat as used in sliding-sleeve fracking, note the 1/16” per side shelf spacing

Fig. 2: Sliding-sleeve frac illustration showing balls and seats

APPLICATIONS FOR DISSOLVABLE DOWNHOLE TOOLS

Fig. 3: Composite plug used in plug-and-perf frac completions

PRACTICAL DEGRADABLE POLYMERS:

PETROLEUM-BASED:Oxo-degradable polymers: These additives (pro-oxidants) use a saltof a transition metal such as cobalt (Co), iron (Fe), manganese (Mn) or nickel (Ni) to drive the oxidation process which, under the action of heator light, will reduce the molecular weight of the polymer to a levelwhere bacteria & fungi in the soil or disposal environment can furtherreduce the material into water, carbon dioxide & biomass.Traditional base resins: PE, PP, PS, PET

Polymers with hydrolysable backbones (aliphatic polyesters):• Polylactide (PLA) (Crystallinity 12.29% to 47.54%)• PLLA (Crystallinity 37%)• Polyglycolide (PGA) (Crystallinity 45-55%)

NATURAL/AGRO-POLYMERSPolymers produced from plants:• Polysaccharides: Starch and cellulose • Lipids

Polymers produced from animal sources:• Collagen, chitin

During the first phase of degradation, water penetrates the biodegradable device, initially cutting the chemical bonds and converting the long polymer chains into shorter and shorter fragments (hydrolysis).

Crystallinity effects degradation

Ø 3.750” PGA ball failure mode at 7,900 psi

Notice how the ball fractured instead of extruding throughthe seat, this failure mode is a hallmark of crystallinity

Fresh Water When the frac ball was kept in water for one month at room temperature little degradation occurred. Raising the temperature of the water to 200° F initiated the dissolving process. At the elevated temperature pieces of the frac ball started to flake off, making a popping sound.

Brine Water No major changes were observed at any temperature the first 39 h. At increased temperatures (200° F), the ball appeared to dissolve slowly, flaking. Within the next 14 h the diameter was reduced significantly, The Ø1.70’’ ball was reduced to Ø1.39’’. 10 % KCl No major changes were observed over the first 30 hrs. Even at 200° F the ball shrunk only a minimal amount from Ø2.13’’ to Ø2.11’’. After 30 hrs the ball started giving off flakes with loud popping noises. 10 % HCl No changes were observed at room temperature within the first week.

OBSERVATIONS ON THE DEGRADABILITY OF PGA

PGA THICKNESS DECREASE

GF PLA PGA PEEK 450G0

2000400060008000

100001200014000160001800020000

Tensile Strength ISO 527 (psi)

Tensile Strength ISO 527 (psi)

PGA CF-PEEK G100

100020003000400050006000700080009000

Maximum pressure held Ø 3.750" ball (psi)

Maximum pressure held Ø 3.750" ball (psi)

ALTERNATIVES TO DEGRADABLE POLYMER

Reactive metals: Magnesium, Aluminum, Calcium Brand names: InTallic™, ExSolv™ Metall

PROS:• High pressure capabilities• Rapid degradation

CONS:• Very expensive• Limited supply

REACTIVITY OF METALS

Ø 3.500” REACTIVE METAL BALL PRESSURE TEST RESULTS

Brine Water At room temperature it took the frac ball 9 days to dissolve completely. Increasing the temperature to 200° F resulted in the frac ball dissolving within 22 hrs.

Figure 3 – ExSolv™ Metall Acid/brine-dissolvable metal alloy Size comparison after 5 days in brine water at room temperature

Figure 2 – ExSolv™ Metall Acid/brine-dissolvable metal alloy frac ball dissolving

OBSERVATIONS ON THE DEGRADABILITY OF REACTIVE METALS

CONCLUSIONS:

• DEGRADABLE POLYMER DOWNHOLE TOOLS OFFER A COST-EFFECTIVEWAY TO PREVENT COSTLY MILL-OUTS

• IN APPLICATIONS WHERE DEGRADABLE POLYMERS ARE NOT STRONG ENOUGH,DEGRADABLE METALS CAN SUBSTITUTE, I.E.: USE DEGRADABLE POLYMER FRAC BALLSUP TO Ø 2.500” THEN SUBSTITUTE REACTIVE METAL BALLS FOR LARGER SIZES

• DEGRADABLE POLYMERS NEED ONLY H2O TO BREAK DOWN – HCl CAN ACT ASAN ACCELERANT

• DEGRADABLE METALS NEED SALTS AND/OR ACID TO BREAK DOWN