Currently, the company is drilling out the cement plug and washing out the hole. Once this has been done it will to run casing calibre and cement bond log to a depth of about 1005.8 metres.

Gas2Grid said the re-entry is intended to establish if the well can be completed for a long-term test of one of the two gas zones. On a 1960 drill stem test, the well flowed at 5 million cubic feet per day at an 850-metre deep gas zone and 12.6 million cfd at 1850m, the company said.

“If the re-entry is not possible due to technical reasons, such as corroded casing or junk in the hole, the rig will immediately be skidded some 20 yards (21.88m) on the stie and commence drilling a new well to the target zones,” Gas2Grid managing director Gundi Royle said.

The combined 17.6 million cubic feet per day flow from the two zones, if sustained, would be sufficient to fire a 40MW power plant, the company said in a previous report.

Upon success this time around, the company hopes to produce gas for electricity generation.

"In the sixties, gas had no commercial value, as gas-fired power generation as it is now used was not yet developed," Royle said at the time.

"Furthermore, an electricity hungry market has developed some 30 km north of SC44 where Cebu City, which has 1.5 million inhabitants and is the second largest city in the Philippines, has a significant manufacturing centre."

Before spudding, the historic well was opened up, the top cleaned out and a new wellhead fixed onto the casing.

Gas2Grid, which holds a 100% interest in the 100,000 hectare licence, announced in August it was appraising the Malolos feature to establish a sustainable gas flow.

The Malolos feature, with potential gas resources of 50 bcf, is on trend with three other culminations - Butak, Barili and Esperanza - which have estimated gas resources of 240 bcf, based on assumptions from the Malolos-1, according to Gas2Grid.