WATER-DISSOLVABLE POLYMERS FOR USE IN Energy Rubber Group, Inc. 2014 Winter Technical Meeting C. Andrew Rosenholm, President / Owner Rockwell Oil and Gas Tool Sales car@rockwelloil.com WATER-DISSOLVABLE POLYMERS FOR USE IN MANUFACTURING FRAC BALLS, SEATS AND PLUGS

Examples of degradable polymers in use today: Sutures Tacks Bone anchors Golf tees Flatware Bags Foam 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

APPLICATIONS FOR DISSOLVABLE DOWNHOLE TOOLS Fig. 2: Sliding-sleeve frac illustration showing balls and seats 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 salt of a transition metal such as cobalt (Co), iron (Fe), manganese (Mn) or nickel (Ni) to drive the oxidation process which, under the action of heat or light, will reduce the molecular weight of the polymer to a level where bacteria & fungi in the soil or disposal environment can further reduce 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-POLYMERS Polymers produced from plants: Polysaccharides: Starch and cellulose Lipids Polymers produced from animal sources: Collagen, chitin

Crystallinity effects degradation 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).

Ø 3.750” PGA ball failure mode at 7,900 psi Notice how the ball fractured instead of extruding through the seat, this failure mode is a hallmark of crystallinity

OBSERVATIONS ON THE DEGRADABILITY OF PGA 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.

PGA THICKNESS DECREASE

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

OBSERVATIONS ON THE DEGRADABILITY OF REACTIVE METALS 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 2 – ExSolv™ Metall Acid/brine-dissolvable metal alloy frac ball dissolving Figure 3 – ExSolv™ Metall Acid/brine-dissolvable metal alloy Size comparison after 5 days in brine water at room temperature

CONCLUSIONS: DEGRADABLE POLYMER DOWNHOLE TOOLS OFFER A COST-EFFECTIVE WAY TO PREVENT COSTLY MILL-OUTS IN APPLICATIONS WHERE DEGRADABLE POLYMERS ARE NOT STRONG ENOUGH, DEGRADABLE METALS CAN SUBSTITUTE, I.E.: USE DEGRADABLE POLYMER FRAC BALLS UP TO Ø 2.500” THEN SUBSTITUTE REACTIVE METAL BALLS FOR LARGER SIZES DEGRADABLE POLYMERS NEED ONLY H2O TO BREAK DOWN – HCl CAN ACT AS AN ACCELERANT DEGRADABLE METALS NEED SALTS AND/OR ACID TO BREAK DOWN