The company, incorporated more than 80 years ago in Papua New Guinea, announced it discovered natural gas while drilling its Kidukidu-1 well.
The company said gas was encountered across two zones. One measured 167 feet while the other measured 65 feet.
The Kidukidu prospect is 166 miles off the northwest coast of Port Moresby in 320 feet of water.
"Kidukidu 1 is the third and final well to be drilled" in the area, the company said in a Thursday statement.
French energy company Total signed agreements with Oil Search in October to acquire stakes in the shallow waters of the Gulf of Papua.
The French company said the objective of the deal was to explore and appraise five licenses said to contain a high potential for natural gas.
Papua New Guinea has rich deposits of oil and natural gas, with mineral and oil exports accounting for the bulk of the country's gross domestic product. Papua New Guinea is said to hold as much as 22.5 trillion cubic feet of natural gas reserves, the U.S. Energy Information Administration reported.