LUSI
LIBRARY: KNOWLEDGE MANAGEMENT
WIKI-LUSI
WIKIPEDIA TERKAIT LUSI: Sidoarjo mud flow
Wikipedia
Banjir Lumpur panas Sidoarjo
Menjadi
bahan untuk diperbaiki sesuai fakta yang ada
Sidoarjo mud flow
From Wikipedia, the free encyclopedia
Sidoarjo mud flow, October 20, 2009. NASA ASTER satellite image. Red areas indicate plants in this false-color image
Sidoarjo mud flow, November 11, 2008. NASA ASTER satellite image
The same location prior to the eruption, August 28, 2004. NASA ASTER satellite image
At its peak Lusi spewed up to 180,000 m³ of mud per day.[3] By mid August 2011, mud was being discharged at a rate of 10,000 m³ per day, with 15 bubbles around its gushing point. This was a significant decline from the previous year, when mud was being discharged at a rate of 100,000 cubic metres per day with 320 bubbles around its gushing point.[4] It is expected that the flow will continue for the next 25 to 30 years.[3][5] Although the Sidoarjo mud flow has been contained by levees since November 2008, resultant floodings regularly disrupt local highways and villages, and further breakouts of mud are still possible.[6]
Contents
Geological setting
Geological setting
Mud volcano
systems are fairly common on Earth, and 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-pressured marine carbonates and marine muds.[7]
It forms an inverted extensional basin
which has been geologically active since the Paleogene
epoch.[8]
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 near Surakarta
(Solo) in Central Java and near Purwodadi city, 200 km (120 mi) 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,
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.[9]
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 through sands, shales, volcanic
debris and finally into permeable carbonate
rocks.[1]
At this stage
steel casing was installed in the borehole to help stabilize it. At
5:00 a.m. local time (UTC+7) 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.[10]
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.[10]
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).[11]
A magnitude 6.3
earthquake occurred in Yogyakarta[12]
at ~06:00 local time 27 May 2006, approximately 250 kilometres Southwest of
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.[13][14]
A loss of
circulation happens when drilling mud—necessary for maintenance of wellbore
stability—that is pumped down a shaft does not return to the surface but is
lost into some 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
appears to have been killed within three hours. The next day, on 29 May 2006,
steam, water and mud began erupting up to 200 meters above the well, a
phenomenon that is now known as the Lusi mud volcano.
Hypotheses on the possible causes
The birth of
Lusi was a major disaster for the population living nearby, with loss of their
houses, properties and 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 during
dormant periods. Thus, Lusi is a rare occasion and a unique opportunity to
conduct scientific experiments to further our understanding.
It also offers
opportunities to study the down hole condition of a mud volcano from the
neighboring Banjar-Panji exploration well lithologies.
To explain what
triggered the mud volcano, three hypotheses have been suggested, though none
has won universal support:
- Hydro-fracturing of the formation (reflecting a drilling
problem)
- Fault reactivation (reflecting a natural event)
- Geothermal process (reflecting geothermal heating)
Hydro-fracturing of the formation, hence a drilling related
problem
From a model
developed by geologists working in the UK,[10]
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.[10]
Though steel
casing is used to protect the well bore in oil or gas exploration, this can
only be applied in stages after each new section of the hole is drilled; see drilling
for oil.
The relatively
small distance, around 600 feet (180 m), between the Lusi mud volcano and
the well being drilled by Lapindo (the Banjarpanji well) may not be a
coincidence, as less than a day before the start of the mud flow the well
suffered a kick.
Their analysis
suggests that the well has a low resistance to a kick.[15]
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. Also, a
likely contributor is the dissociation of methane hydrates.
Fault reactivation, hence a seismic related natural event
The relatively
close timing of the Yogyakarta earthquake, the problems of mud loss and kick in
the well and the birth of the mud volcano continue to interest geoscientists.
Was the mud
volcano due to the same seismic event that triggered the earthquake?
Geoscientists from Norway, Russia, France and Indonesia have suggested that a
major fault nearby (the Watukosek fault) may have been reactivated, creating a
mud flow path that caused Lusi.[16][17]
They have
identified more than 10 naturally triggered mud volcanoes in the East Java
province, 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 May 27, 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 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.[18]
The hot water
and steam flowing from the vent, the location of Lusi near a magmatic volcano
complex and its recharge system indicates that Lusi may be a geothermal
phenomenon.
Investigation
Cause
Mudflow,
photo taken on July 21, 2006
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.[19]
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.[19]
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.[20][21]
However the UK
team of geologists downplayed Lapindo's argument and concluded "...that
the earthquake that occurred two days earlier is coincidental."[10]
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 a heavy truck passing over the
area.[1]
In June 2008, a
report released by British, American, Indonesian, and Australian scientists,[22]
concluded that the volcano was not a natural disaster, but the result of oil
and gas drilling.[6]
Legal case
On June 5,
2006, MedcoEnergi (one partner company in the Brantas PSC area) sent a letter
to PT Lapindo Brantas accusing them of breaching safety procedures during the
drilling process.[19]
The letter
further attributes "gross negligence" to the operator company for not
equipping the well bore with steel safety encasing.
Soon afterwards
then-vice president Jusuf Kalla
announced that PT Lapindo Brantas and the owner, the Bakrie Group, would have
to compensate thousands of victims affected by the mud flows.[23]
Criminal
investigations were then initiated against several senior executives of the
company because the drilling operation had put the lives of local people at
risk.[24]
Aburizal Bakrie
frequently said that he is not involved in the company's operation and further
distanced 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 held 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.[25]
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.[25]
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.[26]
Some analysts predict that the Bakrie Group will pursue bankruptcy
to avoid the cost of cleanup, which could amount to US$1 billion.[27]
On August 15,
2006, the East Java police seized the Banjar-Panji 1 well to secure it for the
court case.[28]
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.[29]
After
investigations by independent experts, police had concluded the mud flow was an
"underground blow out", triggered by the drilling
activity. It is further noted that steel encasing lining had not been used
which could have prevented the disaster. Thirteen Lapindo Brantas' executives
and engineers face twelve charges of violating Indonesian laws.[30]
Destruction
caused by the Sidoarjo mud flow, January 2014
Current status
2008
As of October
30, 2008, the mud flow was still ongoing at a rate of 100,000 m3 per
day.[31]
By mid August 2011, mud 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.[32]
The researchers said 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 proposed
that the subsidence was due to the weight of mud and collapse of rock strata
due to the excavation of mud from beneath the surface. Their study also found
that while some parts of Sidoarjo were subsiding, others were rising suggesting
that the Watukosek fault system had been reactivated because of to the
eruption.[33]
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.[34]
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 some 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 were been displaced and in Kelurahan Jatirejo, 262 new
families were expected to be affected by the new flows of gas. Protesting
families took to the streets demanding compensation which in turn added more
delays to the already stressed detour road for Jalan Raya Porong and the The
Porong-Gempol toll road.
The Indonesian
government has stated that their heart is with the people. However the cabinet
meeting on how to disburse compensation has been delayed until further notice.
A local official Saiful Ilah signed a statement announcing that, "The
government is going to defend the people of Siring." Following this
announcement protests came to an end and traffic flow returned to normal an
hour later.[35]
Stakeholder exit
The Australian
oil and gas company Santos Ltd. 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
provision for costs relating to the incident.
Santos had provisioned
for $US79 million ($A119.3 million) in costs associated with the disaster.
Santos had stated in June 2006 that it maintained "appropriate insurance
coverage for these types of occurrences".[36]
2010
New mudflows
spots 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.[37]
As of June
2009, the residents had received less than 20% of the suggested compensation.
By mid-2010, reimbursement payments for victims had not been fully settled, and
legal action against the company had 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, and is currently the chairman of Golkar, one of
the most influential political parties in Indonesia.
2011
In 2011,
Lapindo Brantas published an independent Social Impact Report.[38]
The Sidojaro
mud is rich in rock salt (Halite) and has provided a source of income for the local
residents who have been harvesting the salt for sale at the local market.[citation needed]
2013
In late 2013,
international scientists who had been monitoring the situation were reported as
saying that the eruption of mud at Sidoardjo had was falling away quite rapidly
and that the indications were that the eruption might cease by perhaps 2017,
much earlier than previously estimated.
The scientists
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.[39]
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.[14]
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.[40]
The report of
the debate and its outcomes was published in AAPG Explorer Magazine.[41]
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.[14]
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.[42][43]
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.[44]
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.[45]
It showed the differences in the two
hypotheses, the source of water and the current understanding on the subsurface
geology below the mud volcano. 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.
In July 2013,
Lupi et al. proposed that the Lusi mud eruption was the result of a natural
event, triggered by a distant earthquake at Yogyakarta
two days before.
As a result
seimic 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 feeds the
eruption.[46]
Gallery
-
Photo taken of the area of Sidoarjo destroyed by the mud.
-
School destroyed by mud flow.
-
Lake created by mud with steaming mud flow in background.
-
Image shows scale of the mud hole, with efforts to contain it by removing the mud and creating embankments for flood defence.
References
|accessdate= (help)- Lupi M, Saenger EH, Fuchs F, Miller SA (July 21, 2013). "Lusi mud eruption triggered by geometric focusing of seismic waves". Nature Geoscience. doi:10.1038/ngeo1884. Retrieved July 22, 2013.
External links
- Internet Portal for Lapindo's Victim
- Bakrie & Brothers homepage
- High format pictures of the mud volcano presented by The Boston Globe
- Satellite imagery and Google Earth kml satellite image overlays by CRISP/National University of Singapore
- The EGU Newsletters, Issue 19 March 2007: Mud volcano in Java, known locally as 'Lusi' may continue to erupt for months and possibly years. p.5.
- Humanitus Sidoarjo Fund – LUSI Research Library
Tidak ada komentar:
Posting Komentar