Norman Harsono, Jakarta – A misfired explosion during the drilling of the YYA-1 oil well caused a massive oil spill in West Java in July last year, according to an Energy and Mineral Resources investigation team.
The ministry's oil and gas environment director Adhi Wibowo said on Tuesday that the explosive – whose function was to perforate the bore pipe to allow gas inside – should have been detonated 6,600 feet below the surface. Instead, the explosive was detonated at 700 feet, where the lower pressure enabled greater damage.
"It damaged the bore pipe and the geological formation such that the drill rig became tilted," he said, referring to the fact that the YYA-1 oil rig, owned by state-owned oil company Pertamina, was tilted 13 degrees following the oil spill.
Pertamina had even deployed tug boats to ensure the rig did not tilt any further.
The broken well is one of three wells underneath Pertamina's offshore platform in the ONWJ Block, 2 kilometers north of Karawang. The spill had reached nine islands in Thousand Islands regency as of September, with islands such as Untung Jawa and Lancang suffering the most.
Officials from the Environment and Forestry Ministry previously estimated environmental cleanup efforts would take as long as six months.
"We are still investigating why this premature explosion happened. There might have been unexpected pressure from the rock formation that triggered the explosive," Adhi said.
He added that the investigative team, consisting of academics and industry practitioners, was expected to have the final investigation result out by next month. They determined a "premature explosion" as the oil spill's cause in December last year.
The oil spill was caused by a gas well kick – the release of gas caused by low pressure in a wellbore – on July 12, 2019, that worsened two days later. The spill is estimated to cost "hundreds of billions of dollars" to clean up, according to a source.