East Java mudflow linked to gas drilling

Indonesia’s disastrous mud volcano, linked to Australian company Santos, was probably caused by gas-drilling activities, a new scientific study says.

The study, published in the US Geological Society of America (GSA) journal, GSA Today, says the East Java mudflow was likely caused by a nearby gas-drilling operation, and could continue for “many months and possibly years to come”.

It also warned of a “dramatic collapse” around the main mudflow opening in the coming months.

The seemingly unstoppable mud volcano erupted 200 metres from Santos’ part-owned Banjar Panji exploration well during deep drilling in May last year, spewing out up to 150,000 cubic metres of sludge a day.

Despite efforts to stop it, the thick mud has flooded eight villages in heavily populated east Java, covering houses, businesses, paddy fields, mosques and schools to their rooftops and forcing the permanent relocation of more than 12,000 local residents.

“The … mud eruption appears to have been triggered by drilling of overpressured porous and permeable limestones at depths of 2830 metres below the surface,” the GSA Today article says.

“We propose that the borehole provided a pressure connection between the aquifers in the limestones and overpressured mud in overlying units.

“As this was not protected by steel casing, the pressure induced hydraulic fracturing, and fractures propagated to the surface, where (mud) …started to erupt.”

The well operator, Lapindo, has repeatedly said it believed the mudflow was triggered by an earthquake not the drilling, while the third joint-venture partner, PT Medco has said “gross negligence” was to blame, alleging the 3km-deep well was not properly cased.

A preliminary report by Japanese and Indonesian scientists two weeks ago saying the well breach was most likely caused by the earthquake appeared to back Lapindo’s claims.

However, the new study describes the earthquake as “coincidental”.

It said the earthquake was an unlikely trigger because it occurred two days before the mud volcano erupted, and there were no other mud volcano eruptions in Java at the same time.

The article said the mud flow could continue for some time.

“The unabated 173 days of very active eruption indicate a large aquifer has been penetrated and we can be confident that some kind of eruptive activity will continue for many months and possibly years to come,” it said.

“A region several kilometres wide should undergo sag-like subsidence over the coming months with more dramatic collapse surrounding the main vent.”

Indonesian police have been investigating the case for months, and have named 13 suspects.

Santos owns a non-operating 18 per cent stake in the Banjar Panji exploratory well venture, in partnership with the two Indonesian companies.

It has previously said its share of the cost of the mudflow disaster could be $A43.7 million, but warned its costs could be higher still, when the final damage bill was calculated.

“Further announcements in relation to Santos’s share of potential costs relating to the Banjar Panji-1 incident will be made as definitive information became available and had been evaluated,” Santos said.

Spokesman Chris Bennett said the company would not comment on the likely cause of the mud volcano while a police investigation was underway.

Source: AAP