Thought the energy-risk narrative had gotten repetitive and you could safely ignore the chatter about it during bank-earnings season? Think again.

Oil prices dipped below $30 per barrel for the first time in 13 years this week, and lenders — which had been so reassuring last year — are starting to take more aggressive action to protect against deteriorating credit quality in their energy portfolios.

A trio of banking companies — Hancock Holding in Gulfport, Miss.; Associated Banc-Corp in Green Bay, Wis.; and BOK Financial in Tulsa, Okla. — recently announced that they will sharply increase the size of their loan-loss provisions to reflect deepening issues in their energy books.

Analysts, meanwhile, have been pointing to such warnings as harbingers for increased pain when other banks report fourth-quarter results in coming weeks.

To be sure, no two energy portfolios are the same, in terms of size, client mix and risk, and bankers largely communicated throughout last year that their oil-related issues were under control. And, so far, no Texas banks have gone public with plans to boost reserves.

Still, recent preannouncements are creating increased concern, and have been prompting more questions, about bigger losses now that oil prices have fallen below $30 a barrel. BOK Financial, in particular, warned in a press release Wednesday about an "increased risk of loss" since the stagnation in oil prices has entered its second year.

A key number to focus on in fourth-quarter results is the size of each bank's energy reserve as a percentage of total energy loans.

Kevin Fitzsimmons and Joseph Fenech, analysts at Hovde Group, wrote in a Jan. 11 note to clients that added provisioning by Associated and Hancock will push those banks' energy reserves close to 5% of total energy loans.

A 5% reserve "will likely become — in investors' minds at least — somewhat of a new required minimum for the energy reserve," the analysts wrote. "Banks that opt not to take it to that level will likely face scrutiny on why that bank's reserve doesn't need to be that high."

Brady Gailey, an analyst at Keefe, Bruyette & Woods, also drew attention to a 5% energy reserve in a Dec. 17 note to this clients. He highlighted five banks — Cullen/Frost Bankers in San Antonio; LegacyTexas Financial Group in Plano; Green Bancorp in Houston; MidSouth Bancorp in Lafayette, La.; and BOK Financial — that had general energy reserves ranging from 1.4% to 2.4% on Sept. 30.

Cullen/Frost also appears on a watch list for Stephen Moss, an analyst at Evercore Partners, who also included Zions Bancorp. in Salt Lake City, Texas Capital Bancshares in Dallas, Prosperity Bancshares in Houston and Independent Bank Group in McKinney, Texas. He also noted that energy credits make up 16% of Cullen/Frost's overall loan book, while they make up 4% to 7% of total loans at the other banks on his list.

Fitzsimmons and Fenech pointed out that the $22 billion-asset Hancock and the $27 billion-asset Associated are larger institutions, adding that their moves could be "an indication that regulators are gearing up to get more involved in assessing banks' energy exposure." (Their note was issued before the $31 billion-asset BOK Financial issued its warning.)

For those keen on tracking results for energy lenders, Comerica in Dallas and Southwest Bancorp in Stillwater, Okla., are expected to report earnings next Tuesday, based on the latest earnings calendar from Yahoo Finance. Associated and Hancock are expected to release results on Jan. 21.

LegacyTexas, MidSouth and Zions plan to disclose quarterly earnings on Jan. 25, with Cullen/Frost reporting the next day. BOK Financial, Green Bancorp, Independent and Iberiabank in Lafayette, La., are set for Jan. 27. Hilltop Holdings in Dallas is expected to report next month.

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Corrected January 14, 2016 at 6:54AM: An earlier version of this story incorrectly quoted from a report from Stephen Moss. In his report, Moss stated that energy credit make up 16% of total loans at Cullen/Frost, not Zions Bancorp.