U.S. shale drillers are increasingly worried that swelling Russian natural gas exports will slash their European market share.

American gas exporters already are cranking out almost all the fuel they can, but as U.S. capacity to ship the fuel overseas expands, some domestic drillers are pessimistic about the prospect of increasing sales to the red-hot European market, the Federal Reserve of Kansas City found in its quarterly energy-industry survey. U.S. gas output is expected to increase, partly because some supplies of the fuel come out of the ground as a byproduct of oil drilling — so-called associated gas.  

“Associated gas will increase as the U.S. shale drilling ramps up in future years,’’ one anonymous oil and gas executive told Kansas City Fed researchers in the report released on Friday. “European demand will be further satisfied from Russian supply reducing the U.S. market share.” The bank’s region covers important oil and gas state’s such as Oklahoma and Wyoming, as well as parts or all of New Mexico, Colorado, Kansas and Nebraska.Europe is on the doorstep of winter with many of its biggest economies nursing significant gas supply deficits, forcing heavy industry to shut down factories because of surging prices and leaving policy makers scrambling to protect consumers from skyrocketing energy bills.As buyers scour the globe for cargoes of liquefied natural gas, benchmark Dutch futures have more than quadrupled this year, raising the specter of winter blackouts. Gas powerhouse Russia took some of the edge of European worries this week when Vladimir Putin pledged to boost shipments to western customers, but it’s not yet clear if that will be enough.