Sidoarjo mud flow

Mud volcano systems are fairly common, particularly in the Indonesian province of East Java. Beneath the island of Java is a half-graben lying in the east–west direction, filled with over-pressurized marine carbonates and marine muds. It forms an inverted extensional basin that has been geologically active since the Paleogene epoch. The basin started to become overpressurized during the Oligo-Miocene period. Some of the overpressurized mud escapes to the surface to form mud volcanoes, which have been observed at Sangiran Dome near Surakarta (Solo) in Central Java and near Purwodadi city, west of Lusi. The East Java basin contains a significant amount of oil and gas reserves, therefore the region is known as a major concession area for mineral exploration. The Porong subdistrict, south of Sidoarjo city, is known in the mineral industry as the Brantas Production Sharing Contract, an area of approximately that consists of three oil and gas fields: Wunut, Carat, and Tanggulangin. As of 2006, three companies—Santos (18%), MedcoEnergi (32%), and PT Lapindo Brantas (50%)—had concession rights for this area; PT Lapindo Brantas acted as an operator. ==Chronology==

On 28 May 2006, PT Lapindo Brantas targeted gas in the Kujung Formation carbonates in the Brantas PSC area by drilling a borehole named the "Banjar-Panji 1 exploration well". In the first stage of drilling, the drill string first went through a thick clay seam ( deep), then through sands, shales, volcanic debris, and finally into permeable carbonate rocks. Two further eruptions occurred on the second and the third of June about 800–1,000 m northwest of the well, but these stopped on 5 June 2006. A magnitude 6.3 earthquake occurred in Yogyakarta at ~06:00 local time on 27 May 2006, approximately southwest of Sidoarjo. It has been suggested that a small (20 barrel) mud loss occurred in the Banjar Panji-1 well seven minutes after the earthquake (consistent with the time taken for the seismic waves to reach the Lusi location), The well suffered a complete loss of circulation at 12:50 p.m. local time on 26 May 2006, which was between 1.5 and 4.75 hours after three large aftershocks. A loss of circulation happens when drilling mud—necessary for maintenance of well bore stability—that is pumped down a shaft does not return to the surface but is lost into an opening or a fault system. This mud loss problem was finally stopped when "loss circulation material" was pumped into the well, a standard practice in drilling an oil-and-gas well. A day later, the well suffered a "kick", an influx of formation fluid into the well bore. The kick was reported by Lapindo Brantas drilling engineers as having been killed within three hours, though alternative interpretations of drilling records, specifically ongoing fluctuations in downhole drill-pipe pressure, indicate that the kick continued for at least 24 hours. Early the next day, on 29 May 2006, steam, water, and mud began erupting up to above the well, a phenomenon that is now known as the "Lusi mud volcano". Dense drilling mud and cement were pumped down the Banjar Panji-1 well at various times in the 48 hours after the mudflow started, in an attempt to kill the surface mud eruption. Lapindo Brantas daily drilling records state that "bubble intensity reduced and elapse time between each bubble is longer" after pumping dense drilling mud down the well, indicating direct communication between Banjar Panji-1 and the Sidoarjo mudflow. ==Possible causes==

The Lusi eruption was a major disaster for the people living nearby, with the loss of homes, other properties, as well as livelihoods. To explain what triggered the mud volcano, three hypotheses have been suggested, though none has won universal support: • Drilling-induced fracturing or fault reactivation (reflecting a human-made event) • Earthquake-triggered fault reactivation (reflecting a natural event) • Geothermal processes (reflecting geothermal heating) Drilling-induced fracturing From a model developed by geologists working in the UK, Similarly, a NE–SW crack in the surface in the drill site may be evidence of an underground blowout. The well may have suffered an underground blowout that resulted in a surface breach. Earthquake-induced fault reactivation The relatively close timing of the Yogyakarta earthquake, the problems of mud loss and kick in the well, and the creation of the mud volcano continue to interest geoscientists. Experts from Norway, Russia, France, and Indonesia have suggested that the shaking caused by the earthquake may have induced liquefaction of the underlying Kalibeng clay layer, releasing gases and causing a pressure change large enough to reactivate a major fault nearby (the Watukosek fault), creating a mudflow path that caused Lusi. They have identified more than ten naturally triggered mud volcanoes in the province of East Java, with at least five near the Watukosek fault system, confirming that the region is prone to mud volcanism. They also showed that surface cracks surrounding Lusi predominantly run NE–SW, the direction of the Watukosek fault. Increased seep activity in the mud volcanoes along the Watukosek fault coincided with the 27 May 2006 seismic event. A major fault system may have been reactivated, resulting in the formation of a mud volcano. Geothermal process Lusi is near the arc of volcanoes in Indonesia where geothermal activity is abundant. The nearest volcano, the Arjuno-Welirang complex, is less than 15 km away. The hot mud suggests that some form of geothermal heating from the nearby magmatic volcano may have been involved. ==Investigations==

Cause Controversy exists around 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 mudflow eruption, and not their drilling activities. Two days before the mud eruption, an earthquake of moment magnitude 6.3 hit the south coast of Central Java and Yogyakarta provinces, killing 6,234 people and leaving 1.5 million homeless. At a hearing before parliamentary members, senior executives of PT Lapindo Brantas argued that the earthquake was so powerful that it had reactivated previously inactive faults and also created deep underground fractures, allowing the mud to breach the surface, and that their company presence was coincidental, which should exempt them from paying compensation damage to the victims. However, a UK team of geologists downplayed Lapindo's argument and concluded "...that the earthquake that occurred two days earlier is coincidental". concluded that the volcano was not a natural disaster but the result of oil and gas drilling. Criminal investigations were then initiated against several senior executives of the company, since the drilling operation had put the lives of local people at risk. Aburizal Bakrie's Bakrie Group, one of the owners of PT Lapindo Brantas, tried to distance themselves from the Lusi incident. Afraid of being held liable for the disaster, Bakrie Group announced that they would sell PT Lapindo Brantas to an offshore company for only $2, but blocked the sale. Lapindo Brantas was asked to pay about 2.5 trillion rupiah (about US$276.8 million) to the victims and about 1.3 trillion rupiah as additional costs to stop the flow. Some analysts predicted that the Bakrie Group would pursue bankruptcy to avoid the cost of cleanup, which could amount to US$1 billion. On 15 August 2006, the East Java police seized the Banjar-Panji 1 well to secure it for the court case. The Indonesian environmental watchdog WALHI, meanwhile, had filed a lawsuit against PT Lapindo Brantas, President Susilo Bambang Yudhoyono, the Indonesian Minister of Energy, the Indonesian Minister of Environmental Affairs, and local officials. After investigations by independent experts, the police concluded that the mudflow was an "underground blowout" triggered by the drilling activity. It was further noted that steel-encasing lining had not been used, which could have prevented the disaster. Thirteen Lapindo Brantas executives and engineers faced twelve charges of violating Indonesian laws. ==Status==

2008 As of 30 October 2008, the mud was flowing at a rate of per day. By mid-August 2011, it was being discharged at a rate of 10,000 m3 per day, with 15 bubbles around its gushing point. One study found that the mud volcano was collapsing under its own weight, possibly beginning caldera formation. The researchers said the subsidence data could help determine how much of the local area would be affected. They used GPS and satellite data recorded between June 2006 and September 2007, showing that the area affected by Lusi had subsided by between per year. The scientists found that if Lusi continued to erupt for 3–10 years at the rates measured during 2007, then the central part of the volcano could subside by between . They proposed that the subsidence was due to the weight of mud and collapse of rock strata caused by the excavation of mud from beneath the surface. Their study also found that while some parts of Lusi were subsiding, others were rising, suggesting that the Watukosek fault system had been reactivated by the eruption. A study by a group of Indonesian geoscientists, led by Bambang Istadi, projected the area affected by the mudflow over a ten-year period. The model simulated the mudflow and its likely outcome in order to find safe places to relocate people and affected infrastructure. After new hot gas flows began to appear, workers started relocating families, and some sustained injuries, including severe burns. In Siring Barat, 319 families were displaced, and in Kelurahan Jatirejo, 262 families were expected to be affected. Protesters took to the streets, demanding compensation, which added more delays to the already stressed detour road for Jalan Raya Porong and the Porong-Gempol toll road. A local official, Saiful Ilah, signed a statement announcing that "The government is going to defend the people of Siring." Protests subsequently came to an end, and traffic flow returned to normal an hour later. Stakeholder exit The Australian oil and gas company Santos Limited was a minority partner in the venture until 2008. In December 2008, the company sold its 18% stake in the project to Minarak Labuan, the owner of Lapindo Brantas Inc. Labuan also received a payment from Santos of $US22.5 million ($A33.9 million) "to support long-term mud management efforts". The amount was covered by existing provisions for costs relating to the incident. Santos had provisioned for $US79 million ($A119.3 million) in costs associated with the disaster. The company had stated in June 2006 that it maintained "appropriate insurance coverage for these types of occurrences". 2010 New mudflows began in April 2010, this time on Porong Highway, which is the main road linking Surabaya with Probolinggo, despite roadway thickening and strengthening. A new highway, planned to replace the existing one, was held up by land acquisition issues. The main railway, which runs by the area, was in danger of explosions due to seepage of methane, and ignition could occur from something as simple as a tossed cigarette. As of June 2009, residents had received less than 20% of the suggested compensation for the disaster. By mid-2010, reimbursement payments had not been fully settled, and legal action against the company had stalled. 2013 In late 2013, international scientists who had been monitoring the situation were reported as saying that the eruption of mud at Sidoarjo was falling away quite rapidly and that there were indications that the eruption might cease by perhaps 2017, much earlier than previously estimated. They noted that the system was losing pressure quite rapidly and had begun pulsing rather than maintaining a steady flow. The pulsing pattern, it was believed, was a clear sign that the geological forces driving the eruption were subsiding. 2016 By 2016, the mudflow continued, with tens of thousands of liters of mud contaminated with heavy metals leaking into rivers. The site had also become of interest to "disaster tourists". transferring all duties to the Ministry of Public Works. The government programs that operate to evaluate environmental dangers and protect essential public assets have worked to oversee such site operations. These include conducting surveillance, focusing on ground deformation and gas emissions while protecting the area from mud flow through barrier systems and directing it into specially designed channels that link directly to the Porong River. The area is maintained under supervision, and the environment around the mud flow area has been checked for pollution and land subsidence, which continues to happen at lower rates than during the first years of the disaster. Revived controversy Out of the three hypotheses on the cause of the Lusi mud volcano, the hydro-fracturing hypothesis appeared to be the one most debated. On 23 October 2008, a public relations agency in London, acting for one of the oil well's owners, started to publicise what it described as "new facts" on the origin of the mud volcano, which were subsequently presented at an American Association of Petroleum Geologists conference in Cape Town, South Africa, on 28 October 2008. The assertion of geologists and drillers from Energi Mega Persada was that "At a recent Geological Society of London Conference, we provided authoritative new facts that make it absolutely clear that drilling could not have been the trigger of LUSI." The data was published in 2009 in the Journal of Marine and Petroleum Geology. The report of the debate and its outcomes was published in AAPG Explorer Magazine. The article stated that the voting process was a decision by the moderator and only reflected opinions of a group of individuals in the session room at that time, and that it was in no way endorsed by the association. It further cautioned readers not to consider the voting result as constituting scientific validation. On the possible trigger of the Lusi mud volcano, a group of geologists and drilling engineers from the oil company countered the hydro fracturing hypothesis. In the same journal, a group of geologists and drilling engineers refuted the allegation, showing that the maximum pressure of the "kick" was too low to fracture the rock formation. They further stated that the model developed by Davies was much too simplistic and failed to consider the entire available dataset and other relevant information in its analysis. A 2010 technical paper related to the debate presented a balanced overview on the anatomy of the Lusi mud volcanic system, with particular emphasis on critical uncertainties and their influence on the disaster. In July 2013, Lupi et al. proposed that the Lusi mud eruption was the result of a natural event, triggered by the Yogyakarta earthquake two days before. As a result, seismic waves were geometrically focused at the Lusi site, leading to mud and CO2 generation and a reactivation of the local Watukosek Fault. According to their hypothesis, the fault is linked to a deep hydrothermal system that fed the eruption. This hypothesis was heavily criticized due to the original models containing a major error. The original study proposed that a "high velocity layer" focussed earthquake waves, amplifying the effect of the earthquake. There still remains significant doubt about this revised model, as another study indicated that there was no geological or geophysical evidence for any significant domed high-velocity layer at the mudflow location that would reflect and amplify seismic waves. replicated the seismic wave propagation modelling at the Sidoarjo mudflow location using the two competing velocity models Liquefaction of the Kalibeng clays is a crucial component of the earthquake-induced fault reactivation hypothesis, as this process releases gases and fluids that cause the pressure changes proposed to have induced fault slip. The data also showed that gas increases from downhole formations only commenced when the drilling kick occurred, providing further support that the mudflow was triggered by drilling activities. ==Gallery==

Alone Close to Protected Area.jpg|Area of destruction, with earth embankment in background School destroyed by mud.jpg|Submerged school Remenants of Sidoarjo town.JPG|Area of Sidoarjo destroyed by mudflow Mud hole opening.JPG|Scale of the mud hole, with efforts to contain it using embankments Lake created by mud with steaming mud flow in background.jpg|Lake created by mud, with steaming mudflow in background Lapindo Mudflow, Sidoarjo, Jawa Timur, Indonesia - panoramio (3).jpg|Eruption gas plume SidoarjoMudFlowSource.JPG|Gas plumes next to excavators working Lapindo Mudflow, Sidoarjo, Jawa Timur, Indonesia - panoramio.jpg|View of mud expanse and flooded area after rainfall Staircase to Sidoarjo Mudflow viewing area.jpg|Staircase to viewing area ==References==