Sidoarjo mudflow

インドネシア東ジャワ地方のSidoarjo（スラバヤの南方30 km）では，2006/5に泥火山が噴出し，現在も活動をつづけている．1日10万m³とも推定される大量の熱水と泥が噴出し，周囲に熱水と泥の流れをつくっている．この泥火山の源は，深さ1〜2 kmの過剰圧状態の水とガスの層だと考えられている．この泥火山の噴出は，この地区で行われていた天然ガスの掘削と関係しているかもしれない．また，泥水の噴出を止めるいくつかの対策が行われているが，どれも成功していない．

(Wikipedia)

On 28 May 2006, a private Indonesian oil and gas exploration company, PT Lapindo Brantas, started to drill in the area to search for a natural gas source. After 3.2 km deep of drilling, the drilling pipe penetrated a liqud segment causing a connection to the surface. A hot hydrogen sulphide gas escaped followed by 60°C hot mud volcano. Some 50,000 m3 of hot mud were erupting every day as of August; in September, the amount increased to some 125,000 cubic metres daily. By early September about 25 square km had been flooded by mud. An investigation published in January 2007 reported the mudflow to vary between 7,000 and 150,000 cubic metres per day.

Since May 2006, more than 13,000 people in the Porong subdistrict have been displaced from eight villages. Twenty-five factories had to be abandoned. Rice fields and fish and shrimp ponds have been destroyed. Infrastructure has been affected including a toll road, railroad tracks, and a gas pipe. On 23 November eleven fatalities were reported from the explosion of a gas pipe possibly caused by the mud flow. It is feared that the environmental impact will spread when further mud flow is directed to the Porong River and then to the sea. Further, it is anticipated that the area around the mud vent will sink forming a crater.

Causes
The cause of the eruption is under discussion. On one side there is speculation that an earthquake that struck Yogyakarta on May 27, the day before the well erupted, may have cracked the ground, creating potential pathways for the mud to reach the surface. However, the epicenter was about 300 km away, and the magnitude was only a 2 on the Richter scale near Porong. On the other side it has been suggested that the drilling procedure was faulty by not using a casing, and possibly using a low pressure drilling technique, and inadequate supervision. Without casing liquid at any level could enter the drilling hole and thus escape.

It is suspected that there is a pressurized liquid layer of undetermined size about 3 to 5 km below the surface that has found its way to the surface.

According to a 2007-published study directed by Richard Davies of Durham University's Centre for Research into Earth Energy Systems (CeREES) the cause of the eruption is most likely the faulty drilling procedure as no casing was used. Earthquake as a cause is dismissed on the basis of the time relationship, the absence of other mud vents, and geological data.

Lapindo Brantas
The drilling company Lapindo Brantas was a subsidiary owned by PT Energi Mega Persada Tbk, in turn 60% owned and controlled by the Bakrie Group. The Bakrie Group is owned by the Coordinating Minister for the People's Welfare Aburizal Bakrie and his brothers. Lapindo Brantas has taken over the initial responsibility and costs caring for the mitigation of the effects of the mud flow. It indicated to have set aside $ 140 million of which half had been used by September. While officially not running the family business since joining the cabinet, A. Bakrie received protests by environmentalists in view of the damage done by his family's company.

In September 2006 Lapindo Brantas was sold for $ 2 to Lyte Ltd, an off-shore company founded earlier in 2006 by the Bakrie Group. In this way Energi that had suffered a major loss in shareholder value would be released from the responsibilities connected with the calamity. There is concern, however, that Lyte Ltd (now renamed Bakrie Gas & Oil) as a limited off-shore company may declare bankruptcy and thus relieve investors of further obligations that may well reach $ 1 billion.