A Pennsylvania natural gas well "blowout" last week helped drive prices to a 14-week high on concern that tighter restrictions on offshore drilling following BP Plc's Gulf of Mexico spill will spread onshore.

The incident on June 3 at the project operated by EOG Resources Inc. shot flames and drilling fluids 75 feet (23 meters) into the air, the state Department of Environmental Protection said in a statement on June 5. The well is in the Marcellus Shale gas find in Clearfield County, about 122 miles northeast of Pittsburgh.

With offshore exploration curtailed, dependence on shale gas may grow, amplifying the impact of any disruptions. A "blowout" is the industry's term for a surge of pressurized oil or gas that causes an eruption and is what caused the explosion and fire at BP's Macondo well in the Gulf April 20, resulting in the biggest oil spill in U.S. history.

"The shale problem is a bullish factor in the market," said Carl Larry, president of Oil Outlooks & Opinions LLC in Houston. "A lot of people are starting to worry about the Gulf production of gas. The more we cut back on Gulf production, the more we rely on shale production."

Eoin Treacy's view The consequences of the BP oil spill are far reaching but one effect is that the six-month ban on deep water drilling puts new Gulf of Mexico natural gas supply on hold. The Pennsylvania blowout is probably not in and of itself very much to be worried about from the perspective of shale gas supply. A more serious issue could be increased regulation of unconventional drilling practices as a result of the BP spill. Water usage agreements could be a further headwind (Also see Comment of the Day on Friday). Add the upcoming Atlantic hurricane season into the equation and the risk appears skewed towards higher natural gas prices.

Prices range around $4 for the last two months. This area also marked the upper side of the long-term base. Natural gas broke successfully above $4.50 last week and a sustained move back below that level would be required to question scope for some further upside.