A volcano of a different kind

Monday, December 24, 2007

Alan V. Morgan

Strange and catastrophic events take place on our world on a regular and ongoing basis. Most of these are events, especially the larger ones, are “natural phenomena” caused by the shudders and burps of our planet, but sometimes these catastrophes are triggered by human activity.  

 
Occasionally these causes are inadvertent — perhaps involving some unfortunate and perhaps un-thought of combination of circumstances that led to disaster. The Frank Slide in Alberta might be one such example. However, on other occasions the disaster was created by humans “who should have known better”. 
 
One of these, appearing in news items over the past few years, is the Indonesian mud volcano, nick-named “Lusi” near Surabaya, in East Java. The “volcano” first erupted on May 29th 2006 after the Indonesian oil and gas exploration group, Lapindo Brantas, drilled an exploratory well that was inadequately protected from blow out. The results have been spectacular and pose an ongoing and expensive threat to the immediate neighborhood of the steaming vent. 
Water and mud pool in decomposing rhyolite, Kerlingarfjöll, Central Iceland
 

Figure 1: Water and mud pool in decomposing rhyolite, Kerlingarfjöll, Central Iceland.

Mud volcanoes are not unusual features. They occur in various parts of the world and have been previously described in Wat On Earth. The term is a catch-all, describing phenomena that range from small-scale mud pots that bubble gases and fine mud in volcanic regions (for example, Iceland or Yellowstone; Fig. 1), to undersea methane vents from subsea clathrate deposits to onshore releases of gases from hydrocarbon deposits, such as those on the Aspheron Peninsula in the Baku region of Azerbaijan, the area of the world’s first modern oil wells (Fig. 2). 
A small methane bubble breaks the surface of a mud volcano in Baku
 

Figure 2: A small methane bubble breaks the surface of a mud volcano in Baku.

Lusi (derived from the Indonesian name for mud (Lumpur) and Sidoarjo (the small town in the province of Porong) is an example of the latter (Fig. 3). 
 
What caused the disaster and could it have been prevented?  
 
Lusi in 2006 showing the main vent, areas of inundation and temporary dykes
 

Figure 3: Lusi in 2006 showing the main vent, areas of inundation and temporary dykes.(Wikipedia)

It appears that Lapindo Brantas had targeted a gas horizon contained within the Kujong Formation carbonates. This unit is over-pressurised and the lower drill string that entered the formation at 2,834m depth was not cased; a normal procedure in areas of oil and gas exploration. At 5 a.m. on May 29th a small blowout of water, gas and mud occurred some 200 m southwest of the well. The cause is assumed to be hydro fracturing of the overlying units that allowed the pressurized water, gas and mud to flow to the surface. 
 
The physical results over the past 19 months have been spectacular; the economic effect for the region devastating, and, for the local inhabitants, absolutely catastrophic. 
 
In September 2006 the flowing mud broke through an emergency dyke system flooding paddy fields inundating almost 2.5 square kilometres and displacing 11,000 villagers from eight villages near the vent. Two months later at least 11 people were killed from a pipe-line explosion, likely caused by subsidence in the area. By February 2007 the mud flows had covered 3.6 km2 and were up to 10m thick (Fig. 4). Four small villages had been buried together with 25 factories, a cemetery, 15 mosques and 18 schools, a major toll road as well as smaller roads and a railway line. 
One of the small adjacent villages flooded by mud and water from Lusi.
 

Figure 4: One of the small adjacent villages flooded by mud and water from Lusi. (Wikipedia).

By the end of January 2007 the mud volcano was producing between 7,000 and 150,000 m3 of mud per day (some 5,000m3 /day in June; 25,000m3 in July; 50,000m3 in August and 120,000m3 /day in September). Since that time geologists have shown that the eruption was a manmade event and not connected to the major 6.3 magnitude Yogyakarta earthquake that occurred some 300 km away two days before the blowout as suggested by company officials. Lapindo Brantas was subsequently asked to pay close to US$277 million as compensation and over US$144 million in additional costs to seal the well. 
 
Commencing on February 27th 2007 large concrete balls weighing about 70kg each and chained in groups of 4 were dropped from a crane into the main vent in the hope that this would stop the flow of mud. This effort was stopped on March 31st. 
 
By the end of March the mud volcano had grown to a height of 14m (46 feet), while the surrounding land had sunk about 30cm from the start of the eruption. The inundation zone had expanded to 6 km2. Efforts to channel the mud into a nearby river and from there to the sea were relatively unsuccessful because of the viscosity of the mud. 
 
In May 2007 engineers decided that a 15 story dam some 10m (33 feet) thick and 120m in diameter would be built around the volcano. The containment walls will consist of two rings of thick steel pipes encased in concrete up to 48m (158 feet) high. The facility will have a water extraction unit that will take the liquid component via a chute to a nearby river for disposal while the more solid fraction would remain to act as a sealing “plug” over the main vent area. The dam is expected to take 8 months to complete and a geology museum and a park will be added. 
 
The latest information shows the area of inundation to be about 7km2 (Fig. 5) and projected to go to 10km2.  The clean-up costs are expected to go to more than US$1 billion. There is a chance of major subsidence in the area and undoubtedly there will be more to this story in years to come. 
 

Figure 5: Ikonos satellite view showing Lusi and surrounding area. The main Bali toll road can be seen broken by flooding in the centre of the image. Factory and housing complexes (top) are in white where a retaining dyke collapsed and mud has started to dry out. Retaining dykes are shown and the vent area is being circled for a major dam wall.

Ikonos satellite view showing Lusi and surrounding area
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