A mud volcano, which has caused millions of dollars worth of damage was caused by the drilling of a gas exploration well, an international team of scientists has concluded. The two-year-old mud volcano, Lusi, still is spewing huge volumes of mud, and has displaced more than 30,000 people.

The most detailed scientific analysis to date disproves the theory that an earthquake that happened two-days before the mud volcano erupted in East Java, Indonesia, was potentially to blame. The report by British, American and Indonesian and Australian scientists outlines and analyzes a detailed record of operational incidents on the drilling of a gas exploration well.

This latest theory is challenged by the company that drilled the well, and some experts who argued that the Yogyakarta earthquake two days before the eruption was the cause. University of California, Berkeley, researchers undertook a systematic study to test the claims that the eruption was caused by this earthquake. They found that none of the ways earthquakes trigger eruptions could have played a role at Lusi. “In this case, the earthquake was simply too small and too far away,” says a spokesperson.

The new report concludes the effect of the earthquake was minimal because the change in pressure underground due to the earthquake would have been tiny. Instead, scientists are “99 percent” certain drilling operations were to blame. Another researcher explains: “We show that the day before the mud volcano started there was a huge ‘kick’ in the well, which is an influx of fluid and gas into the wellbore. We show that after the kick, the pressure in the well went beyond a critical level. This resulted in the leakage of the fluid from the well and the rock formations to the surface – a so-called ‘underground blowout.’ This fluid picked up mud during its accent, and Lusi was born. Chances of controlling this pressure would have been increased if there was more protective casing in the borehole. We are more certain than ever that the Lusi mud volcano is an unnatural disaster, and was triggered by drilling the well.”