Bilge slick detail

PERKASA Caught Bilge-Dumping?

Possible Bilge Dumping by Indonesian Cement Carrier in the Strait of Malacca

By Lucy Meyer

On February 15, 2019, a vessel that appeared to be releasing oily waste was captured by satellite almost 10 kilometers offshore Peureulak, a small town in Aceh Province, on the northern tip of the Indonesian island of Sumatra. Radar imagery from the European Space Agency’s Sentinel-1 satellite shows an 18-kilometer slick trailing a northbound ship, visible as a bright spot at the end of the dark slick.

Bilge slick detail
Figure 1. Sentinel-1 radar satellite image showing suspected bilge-dumping (dark, linear slick) off Sumatra on February 15, 2019.

The ship is traveling through the Strait of Malacca, a narrow strip of water between Sumatra and the Malay Peninsula. The Strait is one of the world’s busiest shipping lanes as it is both the shortest and most convenient path between the Indian and Pacific Oceans. Due to the Strait’s high density of marine traffic of all types, oil spills — accidental and intentional — are likely to occur. Figure 1 illustrates suspected bilge dumping, a typically intentional discharge of oily waste from ships to reduce ballast water or free up space in the cargo holds. Typically, bilge-dumps form distinctive linear slicks visible on satellite imagery.

While radar satellite images are very useful tools for detecting slicks, they are typically not detailed enough to allow identification of the responsible vessel. However, many vessels broadcast their identity and other information using the radio-frequency Automatic Identification System (AIS). AIS use is required for all large cargo vessels and tankers. By studying the AIS broadcasts in this area using exactEarth’s ShipView service, which collects the signals using satellites and ground-based receivers, SkyTruth analyst Bjorn Bergman determined the Indonesian cement carrier PERKASA (Figure 2) was at this location when the Sentinel-1 radar image was acquired. Formerly known as KOEI MARU NO 7, the vessel was built in 1981 by Ube Industries, Ltd., a Japanese chemical manufacturing company. Today, the ship is operated by PT Indobaruna Bulk Transport (IBT), an Indonesian shipping company based in Jakarta.

Figure 2. MV PERKASA [source: IBT].
Figure 3. PERKASA’s AIS broadcast track overlain on Sentinel-1 image.

Figure 3 shows the PERKASA’s  AIS-derived track overlain on the Sentinel-1 image, revealing a very close match between the vessel’s path and the suspected bilge slick. The AIS signal immediately to the south of the vessel location on the image indicates it was traveling 11 knots (~20.4 km/h) at 11:17 UTC;  the signal immediately following at 12:10 UTC indicate the vessel was traveling 10.8 knots (~20.0 km/h). Using the location data encoded with these AIS signals, we calculated the likely position of PERKASA at the instant the image was acquired (11:43 UTC). The ship’s predicted location closely matches the vessel’s position in the Sentinel-1 image, and no other vessels broadcasting AIS were likely candidates for a match. This leads us to infer that PERKASA is the vessel seen apparently discharging oily bilge waste in the satellite image.

Slicks to the south
Figure 4. Zoomed-out view of Sentinel-1 image showing a series of patchy slicks along the coast of Aceh Province, Indonesia. Dark, linear slick at upper left is the suspected bilge slick from PERKASA shown in Figures 1 and 3.

To the south, a chain of less-distinctive slicks along the coast are roughly aligned with PERKASA’s track (Figure 4). These slicks are broad and striated as opposed to the slender 18-kilometer long slick, which could be a result of wind and current blowing apart what had originally been a series of discharges from the vessel. The AIS transmissions from PERKASA are infrequent in this region (Figure 5), making us somewhat less confident that this vessel was also the source of these patchy slicks.

Slicks to the south + AIS
Figure 5. PERKASA’s AIS-derived track overlain on Figure 4.

The operator of PERKASA, IBT, claims “we put high priority in safety by adhering to policies, practices, and procedures in our Safety Management System to ensure the safety of crews, staffs, cargoes, vessels, as well as environment.” In addition nearly all of IBT’s fleet is registered with classification societies. According to The International Association of Classification Societies (IACS), the purpose of a classification society is “to provide classification and statutory services and assistance to the maritime industry and regulatory bodies as regards maritime safety and pollution prevention.” IACS is a non-governmental organization composed of twelve classification societies.  PERKASA is registered with Biro Klasifikasi Indonesia (BKI) and Nippon Kaiji Kyokai (ClassNK), which is a member of IACS.  

One of the certification services provided by ClassNK is the Verification for Clean Shipping Index (CSI). The objective of CSI is to verify the environmental performance of a vessel’s operations in five areas, including water and wastes. Ballast water, sewage/black water, garbage, sludge oils, and bilge water are covered under this category.

Bilge dumping — intentional or otherwise — would seem to violate the principles touted by the vessel operator, and call into question the effectiveness of the classification societies.  

What can we learn from the longest oil spill in US history?

[This is a guest post about the ongoing Taylor Energy oil spill from Dr. Ian MacDonald, oceanographer at Florida State University. Ian helped SkyTruth make independent estimates of the size of the Deepwater Horizon oil spill in 2010 that dwarfed the estimates told to the public by BP.]

As recently as two days ago — March 13, 2019 — pollution experts at the National Oceanic and Atmospheric Administration were reporting a 14 square-mile oil slick that originated out in the Gulf of Mexico about 12 miles from the Birdfoot Delta’s farthest bit of land.  By now there are hundreds of satellite and aerial images telling the same, sorry story. The source is the wreck of MC20A, an oil platform owned by Taylor Energy Company that was destroyed by winds, waves, and mudslides spawned by Hurricane Ivan in 2004. Last fall, the Coast Guard and other agencies federalized the response to an oil spill that has been going on for fourteen years and counting, disinviting the company from the latest effort to stem the flow by attaching a massive containment dome to what remains of the platform.  Although the company has long insisted that the spill is trivial–no more than 10 gallons per day–a growing chorus of scientists have disagreed, by orders of magnitude. My personal estimate is 96 barrels (4032 gallons) per day, and I tend toward the low end of the scientific opinions.

Why the Feds changed their mind, and how come it took so long, are questions I address in a report on the longest offshore oil spill in U.S. history.  I tell the story from my perspective as an oceanographer who studies natural and unnatural oil inputs to the ocean, and based on what is now over seven years of funded research on MC20A.  

Storms like Ivan seem to be growing more common.  The sediments lost from the drastic reduction of Louisiana wetlands have been deposited on the slope in huge mud lobes–some of which will inevitably slide toward the sprawling network of aging platforms and pipelines that surrounds the Delta.  The lessons we learn from MC20A, and the response by a unified command under the direction of the US Coast Guard, may be put to the test again, possibly much more severely than with MC20A.

Will we be ready?
Read my report to learn more.  

A look back at 20 years of oil and gas permitting in Wyoming

A shift in priorities of the EPA under the current administration has raised awareness of an increase in oil and gas permitting across the USA. However, the increase began before the current administration. Although the federal government controls most regulations and laws that affect permitting, other factors such as global oil and gas prices, advances in drilling and production technology, and state governments’ willingness to accommodate investors have an effect on permitting and investment by energy companies. It should be pointed out that permitting does not necessarily indicate drilling as companies can request permits but then hold on to the permits until either eventually drilling, requesting a new permit, or selling the permit to another company. This can tie up land for decades and is covered in more detail by The Wilderness Society’s report: “Land Hoarders: How Stockpiling Leases is Costing Taxpayers”.

Wyoming has an economy that is built on coal and oil, but in the 80s and early 90s it was suffering from an oil glut that caused prices to drop. As prices began to recover throughout the 1990s and 2000s and eventually boom (Fig.1), some companies sought to diversify into natural gas (read more in James Hamilton’s paper “Causes and Consequences of the Oil Shock of 2007-08). Many began to drill for gas in the coal fields of Wyoming, and to apply the relatively new technology of hydraulic fracturing (“fracking”) to extract natural gas from previously uneconomic, low-permeability sandstone and shale reservoirs found throughout the Rocky Mountain West.

Oil and gas prices since 1985.

Figure 1. Oil and gas prices since 1985.

The oil and gas boom ended abruptly in 2008 when the effect of the global financial crisis reached the oil and gas markets and prices plummeted.

To better understand the effect these events had on Wyoming, I analyzed permits for new oil and gas wells, issued by the state over the past 20 years. This data is freely available from the Wyoming Oil and Gas Conservation Commision website: First, I should point out that this data has inconsistencies and holes, due to apparent data entry errors like missing or incorrect dates, missing latitude or longitude, typos, etc. Unfortunately, this meant nearly 24% of the total permits had to be left out of my analysis. Some errors still remain, as seen in this map of permit applications received by the state (Fig. 2). Each county is colored differently and there appear to be some permits which either have the wrong county listed or incorrect map coordinates.

Distribution of oil and gas drilling permit applications, color coded by county.

Figure 2. Distribution of oil and gas drilling permit applications, color coded by county.

What immediately stands out is the relatively densely-packed permits in Campbell county, in the north-east of the state. When I looked closer at this county over time, I saw that most of the permit applications were submitted during the beginning of the boom of 1998-2008. This is quickly followed by a sharp drop around 2000, the time hydraulic fracking made drilling in other parts of the state (and country) more profitable. The original method of coal bed methane drilling was considered uneconomical compared to this new fracking method. At that time, I saw a rise in permit applications across other counties (Fig. 3), but far more subdued than the earlier rush, possibly because fracking made deposits across the country viable and so the increase was more widespread across and outside Wyoming. This is just a theory though, these could easily be due to business strategies of companies “capturing” land before their competitors.

Applications for oil and gas drilling permits received over time by county.

Figure 3. Applications for oil and gas drilling permits received over time by county.

The rate of permit applications slows for all counties as the boom ended around 2008 with a short-lived rise leading up to 2016. The boom and bust periods can be seen more clearly when I looked at the overall quantity of permit applications across Wyoming (Fig. 4).

Total number of oil and gas drilling permits applied for in Wyoming.

Figure 4. Total number of oil and gas drilling permits applied for in Wyoming.

The initial rush of the boom was followed by a dip and second climb as fracking technology took off. This is followed by the bust of 2008. There is a slight rise again around 2016, but it drops off by 2017. The effect of this activity is closely reflected in unemployment figures for the state (Fig. 5). Considering that I am looking at permitting however, and not drilling, this correlation should be seen as a reflection of oil and gas companies’ business activities in a holistic sense.

Unemployment rate for Wyoming over the past 20 years.

Figure 5. Unemployment rate for Wyoming over the past 20 years.

Initially, there’s an overall steady decline in unemployment as the boom sweeps up employees but this rockets up once the bust comes along. Interestingly, between 2012 and 2016, there is a steady rise in permit applications which is reflected by the steady drop in unemployment but this is interrupted by a bump in unemployment around 2016. The restoring of the unemployment level after 2016 is not reflected in the drop in permit applications, however. Those appear to drop off.

Although there are booms and busts, the overall number of well permits is constantly increasing (by simple fact of the number of new permits applied for always outweighing the number of permits expiring). The animated image below (Img. 1) shows the growth of oil and gas permit applications as companies move across the state.

Image 1. Permits applied for over the past 20 years.

Image 1. Permits applied for over the past 20 years. (Click to see time-series)

Graphs and maps give us a good idea of the trends but sometimes it is even more helpful to see the physical reality of these numbers.  This is an area in the most heavily permitted county, Campbell (Img. 2).

Image 2. Comparison of an area of Campbell county from July 1999 to July 2018.

As well as the dramatic increase in well pads (i.e., drilling sites), these images show the addition of access roads threading across the landscape.

What this data doesn’t show is the large amount of orphaned wells that were left behind after the price of oil and natural gas dropped in 2008. This has left a legacy of about 3600 abandoned wells (scroll to bottom for total number of orphaned wells currently tracked by Wyoming Oil and Gas Conservation Commision). Often the state, and therefore, the taxpayers, are left to handle this burden because the responsible companies are either unknown, unable to cover the cleanup costs, or have declared bankruptcy and disappeared. Understandably, the state would prefer to see the wells operate once more rather than paying considerable amounts of money to seal them up and restore the land. But these aging, unsecured wells pose a threat to the environment and to public health.  

Many of the coalbed methane wells built at the beginning of the boom were approved with permission to dump untreated “flowback water” on the surface. The companies convinced the state that this  fluid, coming straight from the coal seams targeted by the drilling, would be beneficial for the parched land even though most of the untreated fluid was highly saline. Also, the effect of flooding the land with large volumes of water was extremely unnatural to the existing ecosystem. Many areas that were normally good for grazing became unusable because they were flooded with this salty water. Land that was adapted to little rainfall and snowmelt was suddenly exposed to a constant flow of brine. The companies pushed the idea of plentiful of water for agriculture and wildlife to drink while downplaying the issue of the quality of the water. The state also towed this line while court battles challenging the “beneficial use” permits, led by landowners and conservation groups, were upheld in court. Eventually, they implemented a water-to-gas ratio cap on surface discharges since many of the wells were producing plenty of salty water but little or even no gas at all.

One other trend that I discovered while scrutinizing the permit database was the time it took to process these permits (Fig. 6 & 7). Plotting permit approval times at first appears to show a distribution that follows the general trends that I’ve seen so far, tracking the boom and bust periods. For comparison, I plotted these for both the year of permit application (Fig. 6) and year of approval (Fig. 7).

Figure 6. Permit approval time arranged by year of application.

Figure 6. Permit approval time arranged by year of application.


Figure 7. Permit approval time arranged by year of approval.

Figure 7. Permit approval time arranged by year of approval.

The red lines track the annual average wait time and give a clearer picture of the trend. The spread of wait times fluctuate far more than the actual average wait time. Although the average does not appear to fluctuate much, the scale is a little deceptive as the average wait time extends from 15 days in 1998 to 40 days in the year 2000. The average wait time appears to initially rise with the start of each drilling boom but even out fairly quickly. This changes later when the average wait time climbs sharply around 2013. By 2017, the average wait time has increased considerably to 130 days.

These trends offer insight into the recent history of oil and gas permitting activity in Wyoming. It should be noted that although there was a lot of ‘noise’ in the data that I had to correct or discard, the remaining data helps give me a clearer sense of how oil and gas development is driving change on Wyoming’s landscape. My analysis has been based purely on the history of permitting in Wyoming, not actual drilling. For an analysis on drilling, please look at the Fracktracker Alliance’s page on oil and gas activity in Wyoming. I hope you’ve enjoyed this breakdown of permit data for Wyoming. I hope to take a similar look at other states’ drilling permits, so stay tuned!

Sentinel 1 imagery showing a slick visible with Synthetic Aperture Radar that appears to be emanating from the stricken vessel on July 17.

Signs of oil from the SSL Kolkata

Followers of our work will recall the merchant vessel SSL Kolkata that was being towed by the Indian Navy after catching fire on June 13th off the Sundarbans in the Bay of Bengal.  The Indian Navy had to abandon the ship after a series of explosions and it has been stuck in shallow water ever since. There have been concerns that the 400 tonnes of heavy fuel oil might start leaking as the ship is listing and cracks are developing. The Sundarbans are the world’s largest collection of mangrove forests and a Unesco World Heritage site (, and a major oil spill here could be devastating. We see indications in this Sentinel 1 radar satellite image from July 17 that this is a legitimate concern: there appears to be a 17km slick coming from the vessel, being pushed by the strong currents from the Ganges Delta.

Sentinel 1 imagery showing a slick visible with Synthetic Aperture Radar that appears to be emanating from the stricken vessel on July 17.

Sentinel 1 imagery showing a slick visible with Synthetic Aperture Radar that appears to be emanating from the stricken vessel on July 17.

Considering the volume of oil onboard, the slick on July 17 is far smaller than what we would expect if there were a serious leak. This Sentinel 2 multispectral image from the 19th has also captured the slick. Though it doesn’t give us a complete image of the slick as a radar image would (due to interference from the clouds and cloud shadows), we do get an idea of how the slick is spreading not just south, but also north toward the Delta.

Oil slicks seen in Sentinel 2 imagery taken two days later on July 19.

Oil slicks seen in Sentinel 2 imagery taken two days later on July 19.

Attempts have been made to salvage the ship but were abandoned after cracks developed and the ship started listing. Now that the fuel tank is underwater, they will need to suck the oil out carefully using a method known as “hot tapping.” Although poor weather has delayed these plans, we have observed one tugboat, the Lewek Harrier, visiting the site as recently as the 19th according to its Automatic Identification System (AIS) signal. Though we couldn’t definitively identify the vessel visible in this image at the time it was collected, the Lewek Harrier was the only vessel that was broadcasting AIS in the area on that day. The MCS Elly II has also been operating in the area though we haven’t seen it in any images.

[ Image 3 ]

This vigilant tug, the Lewek Harrier, has been a regular visitor.

This vigilant tug, the Lewek Harrier, has been a regular visitor.

We hope this means an end to this leak and that the extent of the spill will be limited. We will continue to watch this area closely as there is still a real threat to the nearby Sundarbans.

You can find more info on the cleanup here. 

You can find more info from when the containers began slipping off the ship here

Pretty Parallax Planes

While scanning the European Space Agency’s (ESA) Sentinel-2 satellite images for signs of the Sanchi oil slick, I came across an unusual sight of what appeared to be three, brightly-colored aircraft flying in tight formation. I’m not enough of a GIS rookie to be fooled into thinking China’s latest stealth jets were malfunctioning, what I was observing was a single aircraft’s image split into three spectral bands of red, green, and blue.

This flight was snapped by Sentinel-2 on its way to Tokyo (flight data from

To explain why this happens, we need to take a look at the source of these images: Sentinel-2’s MultiSpectral Instrument (MSI) sensor. This can be thought of as a very advanced camera that can see beyond the usual visual spectrum and into the near-infrared (great for monitoring vegetation) and shortwave infrared. Instead of just one sensor in a camera, the MSI sensor has 12 in a row. For a more technical explanation, take a look at ESA’s guide on the MSI sensor here. Imagine a push-broom with 12, wide bristles and you’ll have an idea of how these sensors sweep across the Earth as the satellite flies overhead. Each sensor splits the image into 10 different spectral bands using a stripe filter which means not only is each band detected at a slightly different angle, they are also detected at slightly different times. What this means for an image like the one above, a “true color” composite made up of the MSI’s red, green, and blue bands, is that when the bands are combined, an assumption has to be made about how far away the object is to correct for the parallax and “focus” the image on the target — and for earth-observation systems like Sentinel, the target is the surface of the earth. An element of parallax is factored in when we combine the bands in the same way that our brains adjust for the parallax of the different angles our eyeballs are seeing. This is called orthorectification. For an example of this, hold your finger halfway between this screen and your face and focus on these words. As well as being a bit blurry, you should be seeing more than one finger. In the same way, the RGB bands are combined with the focus on the surface of the Earth so an aircraft at a higher altitude splits into three images, one for each band. Since this Airbus A321 was cruising at an altitude of about 33,000 feet, the aircraft’s position was projected onto the Earth’s surface resulting in three different images, one for each of the bands.

The time difference between when each band is detected also adds to the offset. This isn’t noticeable for stationary or slow-moving objects but an aircraft is moving fast enough to see a difference. In the image we found, the aircraft’s speed, about 550kts (according to, is probably the biggest cause of the shift between images but if you look closely at the contrails, you can see some sideways drift between the first and last image of the plane. The image below, from just off the east coast of Bulgaria, better highlights the two effects of the forward motion of the aircraft and the sideways shift due to parallax.

Example of parallax off the east coast of Bulgaria.

If we really wanted to fix the aircraft’s image, we would need to adjust for the parallax at that distance as well as the delay between each band’s detection (to account for the aircraft’s speed). The result would be that the aircraft would now be one, complete image but everything else would be a multicolor mess.

For more info on this effect, check out this post by Tyler Erickson, or some direct information from the European Space Agency (skip to chapter 2.5).