Four frac tank explosions occurred over two incidents due to static electricity buildup during air/foam assisted flowback operations. Static was generated as oil, water, gas, and sediment flowed through pipes at high velocity into lined, non-grounded frac tanks. This prevented static discharge and led to sparks when the electric charge jumped the gap between charged liquids in the tank and protruding downcomers. To prevent future explosions, operators should use open-top gas buster systems to reduce fluid velocity, allow static dissipation, and prevent accumulation of flammable gas mixtures at tank hatches.

1. FRAC TANK EXPLOSIONS

7. XTO Energy Explosion Site 1 Nov. 10, 2005 – Major County, OK Location Configuration Downcomer entered the front of the tank.

8. XTO Energy Explosion Site 1 Nov. 10, 2005 – Major County, OK Picture of Downcomer

9. Internal Configuration of Frac Tank: Site 1

10. XTO Energy Explosion Site 2 March 31, 2006 – Major County, OK Downcomer Configuration Downcomer is chained to the tank Static Arc Point

11. XTO Energy Explosion Site 2 March 31, 2006 – Major County, OK Oil/Water/Natural Gas contents Downcomer 2 Part Epoxy Lining on Wall Static Builds and Arcs from Fluid to Downspout

12. XTO Energy Explosion Site 2 April 3, 2006 – Major County, OK

14. Fire Triangle Application Air/Foam Flowback Static Electricity Spark Natural Gas & Oil Vapors

22. Typical Frac Tank Configuration

31. Progression of Gas Buster Piping 2” Line 4” Line 8” Line 16” Line 24” Line The line splits at a header system. The header split, along with the increase in pipe diameter, slows the velocity of fluid!

33. Gas Buster Piping and Vents

34. Side Vents at back of Frac Tank

35. Gas Buster System in Wyoming

36. Gas Buster System in Wyoming