Venezuela will hold a 73 percent stake in the cross-border Loran-Manatee field, estimated to hold 10 trillion cubic feet of gas.
Trinidad and Tobago Energy Minister Carolyn Seepersad-Bacha said the field had been under discussion for almost 20 years.
The deal is seen as part of a long-term strategy for Trinidad and Tobago to shore up reserves and stimulate new upstream activity.
The two countries are also expected to negotiate similar agreements for the Dorado-Kapot and Cocuina Manakin fields, located on the shared maritime border.
"This is a start, and we are going to be looking towards other areas where accords can be made," Seepersad-Bacha said after signing the agreement Wednesday with Venezuelan Petroleum and Energy Minister Rafael Ramirez, Trinidad and Tobago's Newsday reports.
Trinidad and Tobago's Prime Minister Patrick Manning signed a framework agreement for oil and gas resources between the countries with Venezuelan President Hugo Chavez in March 2007.