AGL Resources more than doubled its third-quarter operating revenue, lifting the natural gas company’s profits.

But low natural gas prices combined with a glut of supplies and lack of pipeline capacity to move it continued to stress the company’s wholesale business.

Atlanta-based AGL, the nation’s largest natural gas distribution-only company, reported a third quarter net income of $9 million, or 8 cents a share, swinging from a loss of $3 million, or 4 cents a share during the same time a year ago.

Removing expenses from the company’s purchase of Illinois-based Nicor, AGL’s earnings were 9 cents a share during the third quarter, up from 2 cents a share during the same period a year ago.

Operating revenue for the quarter, ending Sept. 30, more than doubled to $614 million, from $295 million a year ago.

A warmer-than-expected 2012 has led AGL to lower its earnings guidance from between $2.60 and $2.75 a share, something that executives have warned shareholders about for several months. AGL’s previous guidance for 2012 was between $2.80 and $2.95 a share.

“You can see the weather anomalies that have affected [our companies],” said Chief Executive John W. Somerhalder II, during a conference call with analysts Thursday.

AGL owns and operates seven natural gas utilities totaling 4.5 million customers, as well as retail and wholesale units. Profits for the natural gas utilities, which include Atlanta Gas Light, rose to $80 million, up from $70 million a year ago.

Increased supplies of natural gas nationwide have led to lower bills for AGL’s customers. But that’s not good news for AGL’s wholesale unit, Sequent Energy Management. The lack of pipeline capacity, particularly in the Marcellus Shale region, has meant Sequent has stored more gas for a longer period of time.

The business unit took steps to curb costs and also started an aggressive schedule to withdraw gas from storage, allowing the wholesale unit to narrow its net loss to $23 million, from $37 million a year ago.

“Economic value largely remains in our storage rollout schedule,” Somerhalder said. “This is the second-strongest rollout schedule in Sequent’s history.”