Water-dissolvable polymer frac balls from Putnam Precision Molding, a division of Ensinger Engineering Plastics, are designed for use in sliding sleeve frac applications. They have a flexible strength of 29,000 psi, specific gravity of 1.6 and can withstand up to 14,000 psi fracking pressure.
While made to dissolve over time, the action isn’t instantaneous. “It’s not like an Alka-Seltzer,” says Fred Mooers, market development manager-energy, Ensinger Industries. Degradation rates vary with temperature of the water. A 2-inch ball takes approximately 12 hours to dissolve in 300-degree F liquid, three days in 250-degree liquid, 11 days in 200-degree liquid and 46 days in 175-degree liquids. A ball in 100-degree liquid would dissolve in approximately 1,400 days.
The dissolvable ball is designed to eliminate the need to retrieve balls that occasionally become stuck in wells during the fracking process.
“If for some reason a ball extrudes through the thin seal area of the seat, it becomes trapped on the backside,” Mooers says. “To retrieve the lost ball, you need to go down and drill the seat out.”
Other balls designed for sliding-sleeve frac applications include PEEK, TORLON and NYLON GF injection molded balls. PEEK balls have a pressure rating equal to G-10 at the weak orientation and are temperature rated for continuous use up to 500 degrees F.
Mooers says the injection molding process reduces material waste and can be lighter in weight than a G-10 (1.8 specific gravity). “Some of the fracking companies want the balls to be a little bit lighter in weight. A carbon fiber ball is 1.4 [specific gravity]. And with some other compounding that we can put in the mix, we can start to approach 1.2, so we’re getting closer to something that can float; getting these balls back out is very important. They would like them to come out in one piece and just flow out under pressure. Then there are applications in the Bakken, where it is my understanding they are looking for a very high specific gravity ball that can get down the hole very quick.”
Ensinger’s TORLON injection frac balls are made from polyamide-imide and have a specific gravity of 1.7, while NYLON GF (Polyamide 6) fracking balls have a specific gravity of 1.6 to 1.7.
Frac balls designed for plug-and-perf applications from Ensinger include the injection-molded NYLON MF and NYLON GF. The NYLON MF (Polyamide 6) balls have a specific gravity of 3.4, while the NYLON GF (Polyamide 6) has a specific gravity of 1.6 to 1.7.
The balls are resistant to most chemicals, and are available in standard and custom sizes, ranging from 1 to 3.75 inches in diameter in 0.125-inch increments. 860/928-7911; www.putnamprecisionmolding.com.