A record 160 commercial banks could fail or require federal assistance this year, the result of the sudden depression in the oil industry this year and continuing problems in agriculture and real estate, the chairman of the Federal Deposit Insurance Corp. said yesterday.

L. William Seidman said in an address to a meeting of the U.S. League of Savings Institutions that the agency boosted its estimate of 1986 failures from 120 -- about the same number that failed in 1985 -- because the number of banks on the agency's problem lists is climbing. At the end of last year, the FDIC judged that 1,140 of the nation's 15,000 banks were having serious problems. Five months later -- after 55 banks failed -- the problem list grew to more than 1,300.

Seidman said the average bank failure will be small -- the average insolvent institution will have assets of about $40 million -- and the record number of 1986 failures can be expected to cost the FDIC about $1 billion. But Seidman said that investment income and premiums paid by insured banks will exceed costs by about $1 billion.

He said that the FDIC's strength is demonstrated by its ability to absorb a record number of bank failures and still run a $1 billion operating surplus.