The match was the Nottinghamshire all-rounder's third in the format for England this year which, coupled with his appearances in the first three Tests against the same opposition, took him past the 20-point threshold to earn a deal.
Test appearances earn a player five points apiece on the England and Wales Cricket Board's tally system, with limited-overs games worth two and Patel thus reaching 21.
ECB national selector Geoff Miller said: "This contract reflects the contribution Samit has made to our T20 and Test teams this winter and we congratulate him on his achievement."
Patel made a useful 24 in the first T20 international at Pune and nine in Saturday's win in Mumbai.
He struggled in the Tests, averaging just 17.25 with the bat and taking only one wicket before being replaced by Joe Root for the fourth match in Nagpur.
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