The first exploratory drilling in the East Sea concerning the country's "Blue Whale" oil and gas prospect has failed to confirm economic feasibility.

A senior official at the energy ministry said Thursday while partial signs of gas were detected during the initial drilling, the hydrocarbon saturation rate, a key factor in estimating how much oil and gas can be produced from a reservoir, was not enough to secure economic feasibility.

The drilling into one of the seven potential oil and gas reserves some 40 kilometers off Pohang, North Gyeongsang Province, was conducted for 47 days from December 20 at a depth of three-thousand-021 meters, one-thousand-761 meters of which were below the seabed.

The official said the drilling confirmed that the prospect has a satisfactory quality of geological system and that the ministry plans to outsource analysis of the collected samples and data.

The interim results are expected between May and June, while the final report will likely come in August.

The government plans to start a bidding process in late March to select companies to lead the exploration projects and to attract foreign investment.