More tests in Cagayan Basin gas site set for 2nd semester

STATE firm Philippine National Oil Co.-Exploration Corp. (PNOC-EC) is lining up further tests before the end of the year on an energy asset in Isabela province that could boost the share of natural gas in the country’s energy mix.

“For the Mangosteen project, we will conduct further testing to determine the volume of the gas reserve within the next six months,” company president and CEO Pedro A. Aquino Jr. said in an interview.

PNOC-EC managed to flow gas from the Mangosteen-1 well in Service Contract (SC) 37 over the summer but further tests are needed to check if reserves are at commercial volumes.

PNOC-EC is the upstream oil and gas subsidiary of the Philippine National Oil Co.

The Department of Energy (DOE) said in a project update earlier this month that gas flows detected by PNOC-EC only confirmed the presence of the resource, not its viability.

Simulation tests must be done for better estimates on the volume, optimal flow rate and other relevant reservoir properties, the DOE said.

“We are determining the volume of the producible gas,” Aquino said.

Drilling began on March 21, 2015 and focused gas flow tests on two zones. Formation fluids were allowed to flow from the well to the surface to determine the type of fluids and how fast they can be produced.

PNOC-EC was unable to flow gas in commercial volumes from the Mangosteen-1 well due to restricted gas flow.

“However, they were still able to flow and flare gas twice for a short period from the accumulated gas in the separator,” the DOE said.

A separator is a pressure vessel used for separating well fluids produced from oil and gas wells in onshore and offshore drilling operations.

Cagayan Basin is one of the 16 Sedimentary Basins in the Philippines. It is said to have a potential unmapped resource of 1,938 billion cubic feet (BCF) of gas and 26 million barrels of oil.

Based on the “Philippine Petroleum Resource Assessment, Vol. 8-Cagayan Basin” of the DOE, the potential “mapped” or better studied resource is 123BFC of gas and 3 million barrels of oil.

Presently, there are two service contracts in Cagayan Basin: SC37 operated by the PNOC-EC and SC 52 operated by Frontier Oil Corp., a private company that recently deferred plans of listing in the Philippine Stock Exchange.

SC37 used to host a commercial operation: the San Antonio Gas Field. It opened on July 4, 1994 as the Philippines’ first commercial gas field and provided electricity through the San Antonio Gas Power Plant to more than 10,000 households in Isabela province.

However, the gas reserves were exhausted after 14 years and the gas power plant was shut down on July 31, 2008.

By that time, the operation had generated a total of 187,482.12 megawatt-hours of power with total gas output from San Antonio-1A well of 3.54BCF.

On March 21, 2015, PNOC-EC spudded another drilling. It is called the Mangosteen-1 well in Brgy. Balintocatoc, Santiago City, Isabela.

The Mangosteen prospect has an estimated recoverable resource potential of about 71 BCF based on the original target, which is significantly higher than that of the San Antonio gas field with only 4 BCF.