Sidoarjo mud flow

Sidoarjo mud flow



The Sidoarjo mud flow or Lapindo mud, also informally abbreviated as Lusi, a contraction of Lumpur Sidoarjo (lumpur is the Indonesian word for mud), is a mud volcano[1] in the subdistrict of Porong, Sidoarjo in East Java, Indonesia that has been ongoing since May 2006. The biggest mud volcano in the world was created by the blowout of a natural gas well drilled by PT Lapindo Brantas, although company officials contend that it was caused by a distant earthquake.

Approximately 30,000 m³ (1 million cubic feet) of mud — equivalent to the contents of a dozen Olympic-size swimming pools — are expelled per day.[2] It is expected that the flow will continue for the next 30 years.[3] Although the Sidoarjo mud flow has been contained by levees since November 2008, resultant flooding regularly disrupts local highways and villages. Further breakouts of mud are still possible.[4]
Geological setting

Mud volcano systems are fairly common on Earth, and particularly in East Java province. Beneath the island of Java is a half-graben lying in the east-west direction, filled with overpressured marine carbonates and marine muds.[5] It forms an inverted extensional basin which has been geologically active since the Paleogene epoch.[6] The basin started to become overpressured during the Oligo-Miocene period. Some of the overpressured mud escapes to the surface to form mud volcanoes, which have been observed at Sangiran Dome and near Purwodadi city, 200 km (124 miles) west of Lusi.

The East Java Basin contains a significant amount of oil and gas reserves and therefore the region is known as a major concession area for mineral exploration. The Porong subdistrict, 14 km south of Sidoarjo city, is known in the mineral industry as the Brantas Production Sharing Contract (PSC), an area of approximately 7,250 km² which 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.[7]


Mud eruption chronology

On May 28, 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 (500–1,300 m deep), then sands, shales, volcanic debris and finally into permeable carbonate rocks.[1] At this stage the borehole was surrounded by a steel casing to help stabilise it. At 5:00 a.m. local time (UTC+8) a second stage of drilling began and the drill string went deeper, to about 2,834 m (9,298 ft), this time without a protective casing, after which water, steam and a small amount of gas erupted at a location about 200 m southwest of the well.[8] Two further eruptions occurred on the second and the third of June about 800–1000 m northwest of the well, but these stopped on June 5, 2006.[8] During these eruptions, hydrogen sulphide gas was released and local villagers observed hot mud, thought to be at a temperature of around 60 °C (140 °F).[9]

A magnitude of 6.3 earthquake occurred in Yogyakarta [10] at ~06:00 local time 27 May 2006, approximately 250 kilo-meters South West from Sidoarjo. Seven minutes after the earthquake a mud loss problem in the well was noted. After two major aftershocks, the well suffered a complete loss of circulation.[11][12] A loss of circulation is when drilling mud that is pumped down hole does not return to the surface but is lost into some opening or a fault system. This mud loss problem was finally stopped when a loss circulation material was pumped in 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 appears to have been killed within three hours. The next day, 29 May 2006, steam, water and mud began erupting 200 meters away from the well, a phenomena that is now known as Lusi mud volcano.
[edit] Hypotheses on the possible causes of LUSI

The birth of Lusi was a major disaster for the general population that lives nearby, the loss of their houses, belongings as well as their livelihood. For the scientific community, however, it was a chance to study the evolving geological process of a mud volcano. In the past, mud vulcanologists could only study existing or ancient mud volcanoes conducted during the dormant periods between eruptions of an already existing structure. This is a rare occasion and a unique opportunity to conduct scientific experiments to further our understanding. Lusi also offered scientists to study the down hole condition of a mud volcano from the neighboring Banjar-Panji exploration well lithologies.

To explain what triggered the Lusi mud volcano, three hypotheses are suggested:

Hydro-fracturing of the formation, hence a drilling related problem

From a model developed by geologists working in the UK,[8] the drilling pipe penetrated the overpressured limestone, causing entrainment of mud by water. The influx of water to the well bore caused a hydrofracture, but the steam and water did not enter the borehole; they penetrated the surrounding overburden and pressured strata. The extra pressure formed fractures around the borehole that propagated 1–2 km to the surface and emerged 200 m away from the well. The most likely cause of these hydraulic fractures was the unprotected drill string in the second stage of drilling.[8] While steel casing is used to protect the well bore in oil or gas exploration, this protection can only be applied in stages after each new section of the hole is drilled, see drilling for oil.

The relative closeness, around 600 feet (180 m), between Lusi mud volcano and the well being drilled by Lapindo (the Banjarpanji well) may not be a coincidence and may suggest there is a connection as less than a day before the start of Lusi mud flow, the Banjarpanji well suffered a kick. Their analysis suggests that the well has a low resistance to a kick.[13] Similarly, a NE-SW crack in the surface in the drill site is suggested to be a proof of an underground blowout. The well may have

Fault reactivation, hence a seismic related natural event

The relatively close timing of the Yogyakarta earthquake, the problem of mud loss, the problem of kick in the well and the birth of the Lusi mud volcano are striking and continue to puzzle the Geo-scientists. Was this purely a coincidence or was Lusi caused by the same seismic event that triggers the Yogyakarta earthquake? Based on their field works, a group of geoscientists from Norway, Russia, France and Indonesia suggest that a major fault (the Watukosek fault) that crosses nearby may have been reactivated, creating a mud flow path that caused Lusi.[14][15]

They have identified more than 10 mud volcanoes in the East Java province with at least five in the vicinity of the major Watukosek fault system, all naturally triggered, thus confirming that the region is prone to mud volcanism. They also documented the direction of surface cracks surrounding Lusi that are predominately NE-SW; the direction of the Watukosek fault. Increased seeps activity in the number of mud volcanoes along the Watukosek fault coincided with the May 27, 2006 seismic event shows that their plumbing system were affected. All these suggest that a major fault system may have been reactivated that resulted in the formation of a new mud volcano


Geothermal process

Lusi location is near the arc of volcanoes in Indonesia where geothermal activities are 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.[16] The hot water and steam flowing from the vent, the location of Lusi that is near a magmatic volcano complex and its recharge system appears that Lusi is likely to be a geothermal phenomenon.

These three hypotheses on the possible causes of Lusi are still debated by the earth scientists; all claimed to have the evidence and analysis to support their hypotheses. It will take more unbiased and purely technical analysis to really understand what causes the birth of the Lusi mud volcano. A correct understanding on the phenomenon is a must and an important first step prior to attempting any relief effort.

Investigation
Cause

There was controversy as to what triggered the eruption and whether the event was a natural disaster or not. According to PT Lapindo Brantas it was the May 2006 earthquake that triggered the mud flow eruption, and not their drilling activities.[17] 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 the parliamentary members, senior executives of PT Lapindo Brantas argued that the earthquake was so powerful that it had reactivated previously inactive faults and also creating 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.[17] If the cause of the incident is determined to be natural, then the government of Indonesia has the responsibility to cover the damage instead. This argument was also recurrently echoed by Aburizal Bakrie, the Indonesian Minister of Welfare at that time, whose family firm controls the operator company PT Lapindo Brantas.[18][19]

However the UK team of geologists downplayed Lapindo's argument and concluded that the earthquake was not merely coincidental.[8] While it could have generated a new fracture system and weakened strata surrounding the Banjar-Panji 1 well, it could not have been the cause of the formation of the hydraulic fracture that created the main vent 200 m (660 ft) away from the borehole. Additionally there was no other mud volcano reported on Java after the earthquake and the main drilling site is 300 km (190 mi) away from the earthquake's epicenter. The intensity of the earthquake at the drilling site was estimated to have been only magnitude 2 on Richter scale, the same effect as of a heavy truck passing over the area.[1]

In June 2008, a report released by British, American, Indonesian, and Australian scientists [20] concluded that the volcano was not a natural disaster, but the result of oil and gas drilling.[4]
[edit] Legal case

On June 5, 2006, MedcoEnergi (one partner company in the Brantas PSC area) sent a letter to PT Lapindo Brantas which accused them of breaching safety procedures during the drilling process.[17] The letter further attributes "gross negligence" to the operator company for not equipping the well bore with safety steel casing. Soon afterwards then-vice president Jusuf Kalla announced that PT Lapindo Brantas and the owner, the Bakrie Group, must compensate thousands of victims affected by the mud flows.[21] A criminal investigation was then started against several senior executives of the company because the drilling operation has put the lives of local people at risk.[22]

Aburizal Bakrie frequently said that he is not involved in the company's operation and further detached himself from the incident.[citation needed] Even in his capacity as Minister of Welfare, Aburizal Bakrie was reluctant to visit the disaster site.[citation needed] Aburizal Bakrie's family business group, Bakrie Group, one of the owners of PT Lapindo Brantas, had been trying to distance themselves from the Lusi incident. Afraid of being liable for the disaster, Bakrie Group announced that they would sell PT Lapindo Brantas to an offshore company for only $2, but Indonesia's Capital Markets Supervisory Agency blocked the sale.[23] A further attempt was made to try to sell to a company registered in the Virgin Islands, the Freehold Group, for US$1 million, which was also halted by the government supervisory agency for being an invalid sale.[23] Lapindo Brantas was asked to pay about 2.5 trillion rupiah (about US$ 276.8 million) to the victims and about 1.3 trillion rupiah as additional costs to stop the flow.[24] Some analysts predict that the Bakrie Group will emulate many US mining companies and pursue bankruptcy to avoid the cost of clean up, which could amount to US$ 1 billion.[25]

On August 15, 2006, the East Java police seized the Banjar-Panji 1 well to secure it for the court case.[26] The Indonesian environmental watchdog, WALHI, have meanwhile filed a suit against PT Lapindo Brantas, President Susilo Bambang Yudhoyono, the Indonesian Minister of Energy, the Indonesian Minister of Environmental Affairs and local officials.[27]

After investigations by independent experts, police have concluded the mud flow was an "underground blow out", triggered by the drilling activity. It is further noted that the steel casing lining had not been used which could have prevented the disaster. Thirteen Lapindo Brantas' executives and engineers face twelve charges of violating Indonesian laws.[28]

Current status

As of October 30, 2008, the mud flow is still ongoing at a rate of 100,000 m3 per day.[29] A study has found that the mud volcano is collapsing under its own weight, possibly beginning caldera formation.[30] The researchers say the subsidence data could help determine how much of the local area will be affected by Lusi. Their research used GPS and satellite data recorded between June 2006 and September 2007 that showed the area affected by Lusi had subsided by between .5 and 14.5 metres (1 ft 8 in and 47 ft 7 in) per year. The scientists found that if Lusi continued to erupt for three to 10 years at the constant rates measured during 2007 then the central part of the volcano could subside by between 44 and 146 m (144 and 479 ft). They propose the subsidence is due to the weight of mud and collapse of rock strata due to the excavation of mud from beneath the surface. Their study has also found that while some parts of Sidoarjo are subsiding others are rising suggesting that the Watukosek fault system has been reactivated due to the eruption.[31]

A study by a group of Indonesian geo-scientists led by Bambang Istadi predicted the area affected by the mudflow over a ten year period.[32] The model simulated the mud flow and its likely outcome in order to find safe locations to relocate people and affected infrastructures.

After new hot gas flows began to appear, workers started relocating families and were injured in the process. The workers were taken to a local hospital to undergo treatment for severe burns. In Siring Barat, 319 more families have been displaced and in Kelurahan Jatirejo, 262 new families are also going to be affected by the new flows of gas. Protesting families took to the streets demanding compensations, which in turn added more delays to the already stressed detour road for Jalan Raya Porong and the The Porong-Gempol toll road.

The government has stated that their heart is with the people, although the cabinet meeting on how to disburse the compensation has been delayed until further notice. Local official, Saiful Ilah, signed a statement announcing that "The government is going to defend the people of Siring." After this announcement all protests came to an end and traffic flow returned to normal an hour later.[33]

New mudflows spots have begun in April 2010, this time on Porong Highway, which is the main road linking Surabaya with Probolinggo and islands to the east including Bali, despite roadway thickening and strengthening. A new highway is planned to replace this one however are held up by land acquisition issues. The main railway also runs by the area, which is in danger of explosions due to seepage of methane and ignition could come from something as simple as a tossed cigarette.[34]

As of June 2009, the residents had received less than 20% of the suggested compensation. By mid-2010, reimbursement payments for victims have not been fully settled, and legal actions against the company have stalled. It is worth mentioning that the owner of the energy company, Aburizal Bakrie was the Coordinating Minister for People's Welfare at the time of the disaster. He is now the chairman of one of the most influential political parties in Indonesia.

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 widely 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 (see next section).[citation needed] The assertion of the 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." Other verbal reports of the conference in question indicated that the assertion was by no means accepted uncritically, and that when the novel data is published, it is certain to be scrutinised closely.[citation needed]

In 2009, this well data was finally released and published in the Journal of Marine and Petroleum Geology for the scientific community uses by the geologists and drillers from Energi Mega Persada.[12] It is a common practice in the oil and gas industry to closely guard their drilling and geologic information, and the company involved is of no exception. After such release, however, future scientific research on Lusi should have an access to a set of credible data and not as constraint as early authors were in their limited and questionable quality data to back their claims.

After hearing the (revised) arguments from both sides for the cause of the mud volcano at the American Association of Petroleum Geologists International Convention in Cape Town in October 2008, the vast majority of the conference session audience present (consisting of AAPG oil and gas professionals) voted in favor of the view that the Lusi (Sidoarjo) mudflow had been induced by drilling. On the basis of the arguments presented, 42 out of the 74 scientists came to the conclusion that drilling was entirely responsible, while 13 felt that a combination of drilling and earthquake activity was to blame. Only 3 thought that the earthquake was solely responsible, and 16 geoscientists believed that the evidence was inconclusive.[35]

The report of the debate and its outcomes was published in AAPG Explorer Magazine.[36] 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 in no way endorsed by the association. It further cautioned readers not to consider the voting result in any way as a scientific validation.

On the possible trigger of Lusi mud volcano, a group of geologists and drilling engineers from the oil company countered the hydro fracturing hypothesis.[12] They suggested that analysis based on the well data showed that the well was safe and pressure in the well bore was below the critical pressure. It is therefore unlikely that the well was fractured as charged. Their paper also published data and well information for the first time to the scientific communities as opinions and technical papers up to that time lacked accurate well data and were forced to rely on a number of assumptions.

In February 2010, a group led by experts from Britain's Durham University said the new clues bolstered suspicions the catastrophe was caused by human error. In journal Marine and Petroleum Geology, Professor Richard Davies, of the Centre for Research into Earth Energy Systems (CeREES), said that drillers, looking for gas nearby, had made a series of mistakes. They had overestimated the pressure the well could tolerate, and had not placed protective casing around a section of open well. Then, after failing to find any gas, they hauled the drill out while the hole was extremely unstable. By withdrawing the drill, they exposed the wellhole to a "kick" from pressurised water and gas from surrounding rock formations. The result was a volcano-like inflow that the drillers tried in vain to stop.[37][38]

In the same Marine and Petroleum Geology journal, the group of geologists and drilling engineers refuted the allegation showing that the “kick” maximum pressure were too low to fracture the rock formation.[39] The well pressure analysis based on credible data showed that the well is stronger than the maximum pressure exerted on the well. This implied that the hydro fracturing hypothesis is likely to be incorrect. They further stated that the model developed by Prof. Davies is much too simplistic by not considering all the available dataset and information in its analysis.

The 2010 technical paper in this series of debate presents the first balanced overview on the anatomy of the Lusi mud volcanic system with particular emphasis on the critical uncertainties and their influence on the disaster.[40] It showed the differences in the two hypotheses, the source of water and the current understanding on the subsurface geology below the mud volcano. It is obvious that more geological field studies and analysis based on factual data need to be done before any conclusion can be deduced on what actually caused Lusi mud volcano.


References

1. ^ a b c Richard van Noorden (2006-08-30). "Mud volcano floods Java". news@nature.com. http://www.bioedonline.org/news/news.cfm?art=2755. Retrieved 2006-10-18.
2. ^ Richard A. Lovett. "Nick Robinson". http://news.nationalgeographic.com/news/2007/01/070125-mud-volcano.html.
3. ^ . http://www.abc.net.au/news/stories/2009/06/22/2604203.htm?section=justin. Retrieved 2009-06-22.
4. ^ a b Sidoarjo mud flow from NASA's Earth Observatory, posted December 10, 2008. This article incorporates public domain text and images from this NASA webpage.
5. ^ Simon A. Stewart and Richard J. Davies (May 2006). "Structure and emplacement of mud volcano systems in the South Caspian Basin". AAPG Bulletin 90 (5): 771–786. doi:10.1306/11220505045. http://aapgbull.geoscienceworld.org/cgi/content/abstract/90/5/771.
6. ^ S. J. Matthews and P. J. E. Bransden (1995). "Late Cretaceous and Cenozoic tectono-stratigraphic development of the East Java Sea Basin, Indonesia". Marine and Petroleum Geology 12 (5): 499–510. doi:10.1016/0264-8172(95)91505-J.
7. ^ "Brantas". Our Activities. Santos Ltd.. Archived from the original on 2006-11-01. http://web.archive.org/web/20061101115255/http://www.santos.com/Content.aspx?p=290. Retrieved 2007-03-04.
8. ^ a b c d e f Richard J. Davies, Richard E. Swarbrick, Robert J. Evans and Mads Huuse (February 2007). "Birth of a mud volcano: East Java, May 29, 2006". GSA Today 17 (2): 4. doi:10.1130/GSAT01702A.1. http://www.gsajournals.org/perlserv/?request=get-document&doi=10.1130%2FGSAT01702A.1. Retrieved 2007-03-04.
9. ^ a b Dennis Normile (29 September 2006). "GEOLOGY: Mud Eruption Threatens Villagers in Java". Science 313 (5795): 1865. doi:10.1126/science.313.5795.1865. PMID 17008493.
10. ^ a b Manga, M. (2007). "Did an earthquake trigger the May 2006 eruption of the Lusi mud volcano?". Eos (Transactions, American Geophysical Union) v. 88: 201.
11. ^ a b Davies, R.J., Brumm, M., Manga, M., Rubiandini, R., Swarbrick, R., Tingay, M. (2008). "The East Java mud volcano (2006 to present): an earthquake or drilling trigger?". Earth and Planetary Science Letters 272 (3-4): 627–638.
12. ^ a b c d Sawolo, N., Sutriono, E., Istadi, B., Darmoyo, A.B. (2009). "The LUSI mud volcano triggering controversy: was it caused by drilling?". Marine & Petroleum Geology 26: 1766–1784.
13. ^ a b Tingay, M.R.P., Heidbach, O., Davies, R., Swarbrick, R. (2008). "Triggering of the Lusi Mud Eruption: Earthquake Versus Drilling Initiation". Geology 36(8): 639–642.
14. ^ a b Mazzini, A., Svensen, H., Akhmanov, G.G., Aloisi, G., Planke, S., Malthe-Sorenssen, A., Istadi, B. (2007). "Triggering and dynamic evolution of the LUSI mud volcano, Indonesia". Earth and Planetary Science Letters 261 (3-4): 375–388.
15. ^ a b Mazzini, A., Nermoen, A., Krotkiewski, M., Podladchikov, Y., Planke, S., Svensen, H. (2009). "Strike-slip faulting as a trigger mechanism for overpressure release through piercement structures. Implications for the LUSI mud volcano, Indonesia.". Marine and Petroleum Geology 26(8): 1751–1765.
16. ^ a b Sudarman, S., Hendrasto, F. (2007). "Hot mud flow at Sidoarjo". In: Proceedings of the International Geological Workshop on Sidoarjo Mud Volcano, Jakarta, IAGI-BPPT- LIPI, February 20–21, 2007. Indonesia Agency for the Assessment and Application of Technology, Jakarta..
17. ^ a b c Chris Holm (14 July 2006). "Muckraking in Java's gas fields". Asia Times Online. http://www.atimes.com/atimes/Southeast_Asia/HG14Ae01.html. Retrieved 2007-03-05.
18. ^ "Drilling blamed for Java mud leak". BBC News. 24 January 2007. http://news.bbc.co.uk/2/hi/asia-pacific/6293757.stm. Retrieved 2007-03-05.
19. ^ "Indonesia minister says Java mudflow natural disaster". Reuters. 17 January 2007. http://today.reuters.co.uk/news/articleinvesting.aspx?type=oilRpt&storyID=2007-01-17T125125Z_01_JAK242260_RTRIDST_0_INDONESIA-MUD.XML&pageNumber=0&imageid=&cap=&sz=13&WTModLoc=InvArt-C1-ArticlePage2. Retrieved 2007-03-05.
20. ^ Javan mud volcano triggered by drilling, not quake , press release from UC Berkely, 09 June 2008
21. ^ "Lapindo must cover people's losses from Sidoarjo mudflow: VP". ANTARA. 20 June 2006. http://www.antara.co.id/en/arc/2006/6/20/lapindo_must_cover_peoples_losses_from_sidoarjo_mudflow_vp/. Retrieved 2007-03-05. [dead link]
22. ^ Lucy Williamson (17 August 2006). "Mud flood threatens Java residents". BBC News. http://news.bbc.co.uk/2/hi/asia-pacific/4798501.stm. Retrieved 2007-04-05.
23. ^ a b "Indonesia gas blast linked to volcanic mud". International Herald Tribune. 23 November 2006. http://www.iht.com/articles/2006/11/23/news/blast.php. Retrieved 2007-03-05.
24. ^ "Mud disaster team readies new transportation corridor". 2007-01-13. http://www.corfina.com/financial_news/2007/20070113.html. Retrieved 2007-03-16.
25. ^ "Seeking gas, Indonesians face geysers of mud". International Herald Tribune. 5 October 2006. http://www.iht.com/articles/2006/10/06/asia/web.1006mud.php. Retrieved 2007-03-05.
26. ^ "Police seize Lapindo Brantas' rig". ANTARA. 15 August 2006. http://www.antara.co.id/en/arc/2006/8/15/police_seize_lapindo_brantas_rig/. Retrieved 2007-03-05. [dead link]
27. ^ "Indonesia watchdog sues over "mud volcano"". ANTARA. 12 February 2007. http://www.antara.co.id/en/arc/2007/2/12/indonesia_watchdog_sues_over_mud_volcano/. Retrieved 2007-03-05. [dead link]
28. ^ "Mining firm blamed for mud flooding: report". ABC News Online. March 25, 2007. http://www.abc.net.au/news/newsitems/200703/s1881051.htm. Retrieved 2007-04-10.
29. ^ "Geologists Blame Gas Drilling for Indonesia Mud Disaster". Physorg. October 30, 2008. http://www.physorg.com/news144596883.html.
30. ^ "Study finds Indonesia 'mud volcano' collapsing". AFP. May 28, 2008. http://afp.google.com/article/ALeqM5jEbdX6_pFakYzsR16PHho3vvu1PQ.
31. ^ "World's fastest-growing mud volcano is collapsing, says new research". http://earthobservatory.nasa.gov/Newsroom/MediaAlerts/2008/2008052826906.html.
32. ^ Istadi, B., Pramono, G.H., Sumintadireja, P., Alam, S. (2009). "Simulation on growth and potential Geohazard of East Java Mud Volcano, Indonesia". Marine & Petroleum Geology, Mud volcano special issue 26: 1724–1739.
33. ^ "Tiga Pekerja Terbakar, Warga Tutup Raya Porong". Jawa Pos. May 25, 2008. pp. 16.
34. ^ http://www.thejakartaglobe.com/news/latest-mudflow-bubble-on-sidoarjo-roadway-raises-fears-of-explosion/370173
35. ^ Morgan, James (1 November 2008). "Mud eruption 'caused by drilling'" (web). News Article. BBC News. http://news.bbc.co.uk/2/hi/science/nature/7699672.stm. Retrieved 11-1-2008.
36. ^ http://www.aapg.org/explorer/2008/12dec/mud.cfm
37. ^ "Human error to blame for Indonesia's mud volcano: scientists". AFP. http://www.google.com/hostednews/afp/article/ALeqM5jtvT9FIv-X9he7cJkscTCwO6g1JQ. Retrieved 2010-02-12.
38. ^ Madrigal, Alexis (2010-02-10). "Mud Volcano Was Man-Made, New Evidence Confirms". Wired Science. http://www.wired.com/wiredscience/2010/02/mudvolcano/. Retrieved 2010-02-12.
39. ^ Sawolo, N., Sutriono, E., Istadi, B., Darmoyo, A.B. (2010). "Was LUSI caused by drilling? – Authors reply to discussion". Marine & Petroleum Geology 27: 1658–1675.
40. ^ Tingay, M.R.P. (2010). Anatomy of the ‘Lusi’ Mud Eruption, East Java.