Matador Resources Co. and Endeavor Energy Resources LP are selling bonds to refinance credit lines, the latest in a string of energy companies tapping the note market to pay down revolving debt.

Endeavor sold $300 million of eight-year senior unsecured debt to refinance its asset-based line of credit, according data compiled by Bloomberg. The 8.125 percent notes were sold at par to yield 634 basis points more than comparable government debt. Matador is marketing $350 million in senior unsecured notes maturing in 2023 in its inaugural bond sale to pay off borrowings under its revolver and debt assumed with its purchase of Harvey E. Yates Co., the company said in a statement.

Energy companies, dealing with a commodity slide that has seen the price of oil fall by more than half since June, are looking to shore up finances even as bond-market borrowing costs for the industry have risen to 9 percent from 5.6 percent last year, according to Bank of America Merrill Lynch Indexes.

“Without liquidity there is no chance of survival given the downturn in energy prices, and producers are looking for every way to lock it in,” Brian Gibbons, a senior analyst for oil and gas at CreditSights Inc., said in a telephone interview “Companies are trying to weather the downturn, hoping to see higher energy prices on the other side.

The longer commodities stay under pressure, the more energy company borrowing may increase, Gibbons said.

Junk-rated energy borrowers have already sold about $12 billion in bonds this year, more than double the amount issued during the last three months of 2014, according to data compiled by Bloomberg. Junk, or high-yield, high-risk issuers, are rated below Baa3 by Moody’s Investors Service and BBB- at Standard & Poor’s.

April is a crucial month for the industry because it’s when lenders are due to recalculate the value of properties that borrowers staked as loan collateral. With those assets in decline along with oil prices, banks are preparing to cut the amount they’re willing to lend. That will squeeze companies’ ability to produce more oil.