In May 2006, the Indonesian oil and gas company PT Lapindo Brantas was drilling the Banjar-Panji 1 exploration well targetting gas in the Kujung Formation carbonates in the Brantas PSC area. The well was located in the Porong subdistrict of Sidoarjo in East Java. In the first stage of drilling the drill string first went through a thick clay seam, then through sands, shales, volcanic debris and finally into permeable carbonate rocks. The Banjar Panji-1 well was cased down to 1,091 m. At 5:00 a.m. local time on the 29th of May 2006, after the well had reached a total depth of 2,834 m, water, steam and a small amount of gas erupted at about 200 m southwest of the well. It was the birth of the world’s most destructive mud volcano near the town of Sidoarjo, just over 11 years ago – and to this day it has not stopped erupting. Two further eruptions occurred on the second and the third of June about 1,000 m northwest of the well, but these stopped on June 5, 2006.
There was controversy as to what triggered the eruption and whether the event was a natural disaster or not. According to PT Lapindo Brantas it was the 2006 Yogyakarta earthquake that triggered the mud flow eruption, and not their drilling activities. Two days before the mud eruption, an earthquake of magnitude 6.3 hit the south coast of Central Java and Yogyakarta provinces killing 6,234 people and leaving 1.5 million homeless.
After the Sidoarjo mud flow disaster, known as Lusi, Lapindo Brantas took over responsibility in covering the cost of emergency response and victim resettlement, paying more than $550 million despite its acquittal as the cause of the mudflow in 2009 by Indonesia’s Supreme Court. Uncertainty still surrounds the exact cause of the eruption, with scientists and geological experts unable to reach a unanimous conclusion. Some argue it was the result of drilling while others support the theory that its cause was a natural disaster linked to the reactivation of Mt. Semeru in nearby Yogyakarta.
The Sidoarjo eruption is the largest of its kind. Initially, more than 100,000 tonnes a day was oozing to the surface. This has decreased tenfold, and an analysis based on Japanese satellite observations of ground subsidence suggests a further tenfold decrease can be expected in the next few years. Prof. Michael Manga from the University of California at Berkeley said: “By 2017, it should be more or less over. In real numbers, that’s 1,000 tonnes a day – a thousand pick-up trucks per day of mud. I expect that if the eruption rate drops below some number, that it will just plug itself and stop erupting.” Previous best estimates had indicated Lusi could go on erupting for 25 years or more.
In January 2016, the Jakarta Post said that PT Lapindo Brantas was planning to redrill a gas well in Tanggulangin district which is located some 5 kilometers from the center of the Lusi mudflow. PT Lapindo Brantas has some 30 wells already in operation in Sidoarjo area.