Natural gas pipeline revenues remained flat at $22.4 billion in 2016, but gross margins increased slightly to 70%, according to analysts who recently reviewed FERC's 2016 natural gas pipeline database.

Pipelines experienced a 4.6% compound annual growth rate beginning in 2003, but revenues have been flat since 2014, said Sanford Bernstein analysts Jean Ann Salisbury, Kartik Misra and Zhenhao Li. But because operating expenditures have consistently declined -- due in large part to falling natural gas prices -- gross margins were able to edge higher.

"Overall, margins have improved almost every year since 2000, with only 2000-2001 seeing a slight decrease in operating margin," the analysts said in a report issued Friday.

Firm transport supplied 95% of revenues, while interruptible transport, which makes up 15% of volumes, produced only 5% of revenue.

"EQT Equitrans pipeline has led the way with a five-year compounded growth rate of 22.5%, which has been seen at a steady rate since 2011," the analysts said. "The second fastest revenue grower has been Kinder Morgan's Ruby Pipeline, with a 22.4% five-year compounded growth rate."

The largest decliner was Kinder Morgan's Louisiana Pipeline (KMLP), which saw revenues tumble to $200,000 in 2016 from $233 million in 2015. At the end of 2016, KMLP proposed modifying its pipeline system in order to serve the Sabine Pass liquefied natural gas terminal in Louisiana. The project would increase north-to-south capacity by at least 600,000 Dth/d.

Nine out of the 10 biggest volume growers from 2011-2016 benefited from Marcellus and Utica shale gas, while the fastest declining volumes were on pipelines either related to declining basins, including the Haynesville, Barnett and Rockies, or to gas formerly going to the Northeast.

 "Those attached to declining basins will likely continue to decline (and hit revenue cliffs when contracts expire), while many Northeast bound pipelines will reverse flow and thus their fortunes," the analysts said.

Sanford Bernstein's analysis covered 176 major gas pipelines, including two pipelines that only began showing operating revenue in 2016.