Mark Tingay 2010: Anatomy of the ‘Lusi’ Mud Eruption, East Java

Anatomy of the ‘Lusi’
Mud Eruption, East Java

Mark Tingay 2010:

Anatomy of the ‘Lusi’ Mud Eruption,
East Java
Mark Tingay

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Anatomy of the ‘Lusi’
Mud Eruption, East Java

Mark Tingay 2010:

Tectonics, Resources and Exploration (TRaX), Australian
School of Petroleum
University of Adelaide, SA 5005, Australia

Mark.tingay@adelaide.edu.au

INTRODUCTION AND BACKGROUND
The Sidoarjo mud flow, also known as ‘Lusi’ (a contraction of
Lumpur Sidoarjo) is a unique geological disaster that has ignited
widespread scientific and political controversy. The mud flow
was first observed in a rice paddy in the Porong district at
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Anatomy of the ‘Lusi’
Mud Eruption, East Java

Mark Tingay 2010:

approximately 5am on the 29th of May 2006 and has been
erupting continuously ever since (almost 4 years at the time of
writing).

The

mudflow

has

claimed

17

lives,

displaced

approximately 40000 people, inundated 7km2 of a major town
and caused more than US$550 million in damages (Figure 1;
Cyranowski, 2007).
Lusi is an example of a mud volcano, a relatively common
geological feature in which subsurface mud is extruded at the
surface. However, Lusi is unusual in that it is the first recorded

instance of the birth of a new mud volcano within an urban
region and thus represents a new type of geological disaster
(Davies et al., 2006). Furthermore, there has been intense
scientific and political scrutiny over the triggering of Lusi, with
some researchers suggesting the mudflow resulted from a
blowout in the Banjar Panji-1 well located 150m away (Davies et
al., 2008; Tingay et al., 2008), while a competing theory
maintains the disaster was initiated by the Mw6.3 May 27 th 2006
Yogyakarta earthquake (Mazzini et al., 2007; Sawolo et al.,
2009). However, despite numerous papers and public debates,
the controversy remains unresolved, primarily due to the many
unknowns in the subsurface anatomy of the mud volcano, the
uncertainties
following

surrounding

the

initial

events

eruption

in

the

and

weeks

prior

discrepancies

and
over

interpretation of petroleum engineering data from the Banjar
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Anatomy of the ‘Lusi’
Mud Eruption, East Java

Mark Tingay 2010:

Panji-1 well (Davies et al., 2010; Sawolo et al., 2010).

Figure 1. Aerial view of the Lusi mud eruption looking southwest
(photo taken late may 2007). The mud flow has covered 7km2
of the cisty of Sidoarjo and displaced approximately 40000
people. The main vent has been erupting continuously since the
29th

of

May

2006

at

rates

of

up

to

170000

m 3/day.

Approximately 73 million m3 of mud was erupted in the first 3
years, approximately 1/7th the volume of Sydney harbour.

The issue of triggering of the mudflow is not simply of academic
or legal interest, but has significant implications for the 40000
victims displaced by the disaster, most of whom have not
received full or extensive compensation or relief aid. The
company responsible for drilling the Banjar Panji-1 well (Lapindo
Brantas) has provided partial compensation to residents of four
villages

affected

by

the

mudflow,

while

the

Indonesian

government has provided some relief to other affected people
and has assumed control of the disaster zone. However, Lapindo
Brantas have halted further compensation to the disaster victims
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Anatomy of the ‘Lusi’
Mud Eruption, East Java

Mark Tingay 2010:

(claiming the disaster is natural and not their responsibility),
while international aid agencies will also not provide needed
relief and support (claiming the disaster is man-made and thus
should be funded by Lapindo Brantas). Thus, whilst the
triggering issue continues to be debated, many victims of the
disaster have lived for almost 4 years in refugee villages and

shanty towns built adjacent to the disaster zone. Furthermore,
knowledge of the subsurface anatomy of the Lusi mudflow is
essential for predicting the likely longevity of the disaster, the
possible evolution of the region (in particular the ongoing
subsidence of the area, the reactivation of faults and possibility
of caldera collapse) and whether there may be potential
engineering solutions to kill or control the mudflow.
This paper presents an overview of the geology of the Lusi
disaster and, in particular, provides new information on the
subsurface geology and highlights the key uncertainties in the
anatomy of the mud volcano. Furthermore, all papers on the
Lusi mudflow to date have supported a particular triggering
mechanism and thus presented a subsurface geology that is
somewhat biased towards that mechanism. This study attempts
to provide the first unprejudiced summary of the anatomy of the
Lusi mud volcano, presenting both proposed models of the
subsurface geometry along with their pros and cons.
REGIONAL GEOLOGY
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Anatomy of the ‘Lusi’
Mud Eruption, East Java

Mark Tingay 2010:

The Lusi mud volcano (7º 31’ 37.8”S, 112º 42’ 42.4”E) is
located in the city of Sidoarjo, approximately 25 km south of
Surabaya, the largest city in Eastern Java, Indonesia. Lusi is
located within the East Java Basin, an E-W trending inverted
back-arc basin that underwent extension during the Paleogene
and

was

reactivated

during

the

early

Miocene-Recent

(Kusumastuti et al., 2002; Shara et al., 2005). The MioceneRecent of the East Java Basin in the region around Lusi are
comprised of shallow marine clastics and carbonates, marine
muds, volcaniclastic sediments and volcanic units from the
nearby Penanggungan volcanic complex (located 15km to the
SW of Lusi).
The subsurface geology of Lusi was originally reported in many
studies to be comprised of the following units (Davies et al.,
2006; Mazzini et al., 2007; Davies et al., 2008; Tingay et al.,
2008; Sawolo et al., 2009). (i) Recent alluvium (alternating
sands and shales; 0-290m); (ii) Pleistocene Pucangan Formation
(alternating sands and shales; 290-900m); (iii) Pleistocene
Upper Kalibeng undercompacted smectite-illite muds (9001870m); (iv) Pleistocene Upper Kalibeng volcaniclastic sands
(1870-≈2833m) and (v) Oligocene Kujung reefal carbonates
(≈2833-≈3500m).

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Anatomy of the ‘Lusi’
Mud Eruption, East Java

Mark Tingay 2010:

New Revisions to the Stratigraphy below Lusi
New evidence indicates two major changes to this stratigraphy.
Firstly, the reefal carbonates have been commonly described as
the Kujung Carbonates, which is a major reservoir rock within
the East Java Basin, particularly offshore in the Madura Strait
(Sharaf et al., 2005). The Kujung Carbonate is an early-late
Oligocene (22-28 Ma) transgressive reefal formation. However,
a red algal fragment from the carbonates at the top of the
nearby and stratigraphically equivalent carbonate build up in the
nearby Porong-1 well (7 km ENE of Lusi) was dated by
strontium isotope ratios as being formed in approximately 16 Ma
(Kusumastuti et al., 2002). Hence, the carbonates underneath
Lusi are not the Oligocene Kujung formation, but are most likely
the Middle Miocene Tuban Formation (22-15 Ma; Sharaf et al.,
2005). The known reservoir and fluid properties from other wells
penetrating the Kujung Carbonates has been used for modelling
possible longevity of Lusi as well as in arguments as to whether
Lusi was triggered by drilling (Sawolo et al., 2009; Swarbrick et
al., under review). However, the new evidence that the
carbonates under Lusi are probably of the younger Tuban
Formation renders these previous calculations using Kujung
Formation data spurious.
In addition to the younger reinterpretation of the carbonates,
new evidence also suggests that the lithology of the reported
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Anatomy of the ‘Lusi’
Mud Eruption, East Java

Mark Tingay 2010:

volcaniclastic sands requires correcting. This unit had not been
previously observed in hydrocarbon exploration and production
wells in the area and was reported as being comprised of
volcaniclastics by the on-site mud logging (and then in all
publications examining the Lusi disaster). However, detailed
reanalysis of the cuttings reveals that this unit is actually
comprised of volcanic rocks (primarily dacites and welded tuffs)
that had been ground into mostly sand-sized fragments by the
drilling

process

and,

thus,

mistakenly

interpreted

as

volcaniclastic sands by the mud logger. The new interpretation
of these units as extrusive igneous rocks is supported by
petrophysical log data collected in this interval that reveals a
remarkably uniform, very dense and fast formation (ρ=2.552.65 g/cm3; DT=160-120 µs/ft). The high density and fast pwave velocity of these volcanic sequences indicates that these
volcanic rocks have extremely low porosity (0.65% observed at
depths of >1700m in Banjar Panji-1 (Mazzini et al., 2007).
Finally, biostratigraphical analysis of the erupted mud reveals
the presence of forams and nannofossils observed in cuttings
collected from 1219-1828m depth in Banjar Panji-1. Thus, the
solid fraction of the mud being erupted at Lusi can be well
constrained as primarily coming from the Upper Kalibeng Clays
from between 12191828m depth (Mazzini et al., 2007).
The eruption of mud from Lusi is predominately from one vent,
termed the ‘main vent’ or ‘big hole’. The circular main vent is
approximately 100 m in diameter and has been flowing at rates
of up to 170000 m3/day, with average rates previously
estimated at 90000-100000 m3/day (Davies et al., 2006;
Mazzini et al., 2007; Istadi et al., 2009). However, the Sidoarjo
Mudflow Mitigation Agency (Badan Penanggulangan Lumpur
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Anatomy of the ‘Lusi’
Mud Eruption, East Java

Mark Tingay 2010:

Sidoarjo; BPLS) calculated in early June 2009 that the volume of
mud contained in holding ponds at the time was approximately
65 million m3 and that approximately 8 million m 3 had been
pumped from the holding ponds to the Porong River. Hence, the
total volume of mud erupted by Lusi in its first three years was
approximately 73 million m3 (ignoring potential errors due to
volume

additions

through

rainfall

and

reductions

due

to

evaporation and earlier unmonitored mud pumping and sluicing
of mud into the river). This equates to an average flow rate of
approximately 64000 m3/day over the first three years, and a
significant reduction on the average estimates that have been
used in estimates of Lusi longevity and evolution (Istadi et al.,
2009; Swarbrick et al., under review). Furthermore, flow rate,
whilst

fluctuating

from

day

to

day,

has

been

gradually

diminishing since September 2006 and, at the time of writing, is
estimated as being approximately 20000-30000 m3/day.
The shallow subsurface geometry of the main vent from the
surface to the Upper Kalibeng clays is uncertain. Seismic images
of major mud volcanoes in Azerbaijan commonly suggest that
mud feeder pipes are conical in shape (Stewart and Davies,
2006). However, analysis of exposed Miocene-Pliocene mobile
shale systems in Brunei indicates that mud volcano feeder
systems may be comprised primarily of planar shale dykes
entrained up faults or tensile fractures (Morley et al., 1998;
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Anatomy of the ‘Lusi’
Mud Eruption, East Java

Mark Tingay 2010:

Tingay et al., 2003). The 100 m wide circular main vent and the
extremely high flow rate suggest that the feeder system under
Lusi is either conical in shape or comprised of several very large
open and intersecting fractures. Such an open pipe-like shallow
feeder channel is consistent with measurements obtained during
the 2007 attempt to stop Lusi by dropping sets of concrete balls
tied together by heavy chain into the main crater. Whilst the
attempt to drop these ‘balls and chains’ down the vent failed to
stop or reduce the mud flow, cables attached to several of the
concrete balls showed that some of the sets dropped down to
depths of 800-1000 m. This indicates that a major feeder
pathway is open to a width of at least 30cm down to a depth of
1000m.
Almost all of the mudflow has erupted from the main vent.
However, a number of minor secondary sites of eruption have
also occurred in the region. Three moderately-sized, but shortlived (lasting approximately one week), sand and mud eruptions
occurred up to 1000m from the main vent in the days following
the initial Lusi eruption. Since then, numerous very small (