Indonesia frontier gets new look

Deep Waters Probed for Seeps

American Association of Petroleum Geologists (AAPG)

The challenge:

Develop an extensive but focused overview of deepwater exploration potential offshore Indonesia

TGS-NOPEC Geophysical Company in Perth, Australia, knew it had to provide an extraordinary solution to attract industry interest.

So it turned to a highly innovative approach for gathering multiple forms of offshore data.

"Indonesia's frontier basins, especially the deepwater basins, are very, very under-explored. Most exploration in Indonesia has actually been focused around discoveries," said AAPG member Peter Baillie, TGS-NOPEC chief geologist Asia-Pacific.

Baillie will provide details of the offshore study in the presentation "Innovative Frontier Exploration Using Seismic and SeaSeep™ Data, Indonesia," during AAPG's International Conference in Cape Town in October.

The company held preliminary discussions with the Indonesian government in the first half of 2006, according to Baillie. Going in, it understood that a wealth of good data would be needed to generate attention for the nonexclusive survey.

"We're dealing with deepwater frontier areas that the industry has ignored or written off,” Baillie said. “We had to provide evidence of prospectivity – including charge – to get the industry interested.

"With the combination of traditional seismic plus additional information, all of a sudden, it gives you a whole new picture of these frontier basins," he added.

The company said its survey was the world's largest multibeam bathymetry study – as well as the world's first non-exclusive SeaSeep study.

An Innovative Setting

Few places in the world need exploration innovation as much as Indonesia.

An early member of OPEC, Indonesia has seen a long decline in production.

It became a net crude oil importer more than three years ago as its oil output slid below one million barrels per day.

TGS-NOPEC estimated the country produces about 950,000 barrels a day of crude oil currently, declining at 5 percent per year, and around seven billion cubic feet of natural gas per day.

In May this year, Indonesia announced it would leave OPEC.

Half of Indonesia's 60 basins could be prospective for hydrocarbon production, but its deepwater offshore basins were not only largely unexplored but also largely unevaluated.

To assess the country's deepwater prospects, the company went well beyond its usual approach of simply acquiring seismic data, Baillie said. In its offshore Indonesia project during the past year and a half, TGS-NOPEC has:

  • Acquired 34,000 kilometers of new 2-D seismic data.
  • Developed 400,000 square kilometers of SeaSeep data.
  • Generated additional gravity and magnetic data.
  • Taken more than 1,100 tightly targeted sediment cores.
  • Conducted over 3,000 geochemical analyses.

Major companies have lacked the necessary data and evidence of hydrocarbon presence to undertake large scale exploration offshore Indonesia, Baillie noted.

He said the need for information beyond seismic was obvious.

"We had to find evidence of charge,” he said, “so we used high-resolution, multi-beam bathymetry and backscatter to find potential hydrocarbon seeps on the seafloor.

"When we found seeps or what we thought were seeps, we went in and sampled them,” he said. “Once we had samples, we subjected them to standard geochemistry.”

Signs of Seeps

Multibeam bathymetry uses multiple bands of swath sonar to develop a highly detailed topographic picture of the seafloor.

"On the multibeam bathymetry we've got a bin size of 25 meters. Even small mud volcanoes are coming in at that scale," Baillie explained.

"We've also used backscatter, which is the intensity of the reflected sound wave, and the bin size there is five meters, so your resolution is even greater," he said.

Signs of seeps include both positive and negative seafloor relief – hills or holes – although that isn't always present.

"Around some of the seeps there's no surface expression at all, but when you get hydrocarbons leaking you get communities of organisms, chemosynthetic communities," Baillie said.

"That has an acoustic contrast with the regular muddy substrate you get in deep water, so you pick them up on the backscatter," he added.

TGS-NOPEC sampled the seep locations and offshore study areas using navigated piston coring.

The piston-corer tool was steered from the coring vessel using USBL (Ultra Short Base Line) Navigation on the coring device coupled with differential GPS on the vessel, according to Baillie. That allowed precise placement for each core taken even at great depth.

"There's a transponder in the piston-coring device that can communicate with the vessel,” he said. “They've got computer programs to accurately position the core on the seabed.

"Once we identified the seeps on the seabed, we could navigate our way in with an accuracy of plus or minus 10 meters in over two kilometers of water depth," he added.

Another significant advantage of GPS was that the company knew exactly where all the cores in the study originated.

Sea-Faring Rover Boys

Each six-meter-long core underwent analysis that included examining any history of hydrocarbon seepage. For each core, “we took three samples and subjected those to a suite of geochemistry," Baillie said.

To be successful, he said, the Indonesia survey had to combine the expertise and cooperation of several people and organizations.

"There was a combination of different groups,” he explained. “The Indonesian government had the vision and foresight to support our work. We had a company that provided us with financial and technical expertise. And we went in and did it.”

Paul Gilleran, TGS-NOPEC manager Asia-Pacific, said the idea for surveying and studying the offshore Indonesia seeps actually came from an old concept in the industry.

"I think the idea was started by Exxon, to tell you the truth, with the Rover Boys who were around 50 years ago,” Gilleran noted. “Exxon sent them around the world to find seeps. The difference was, we did it underwater.

“Multibeam technology has been around the oil business for some years, primarily used as a tool for pipeline routing and identification of shallow hazards,” he continued. “The idea to adapt this technology for seep detection as part of an integrated exploration tool came from a group of Unocal Indonesia explorationists, in collaboration with California-based AOA Geophysics, which published this work during the 2005 Indonesian Petroleum Association Conference.

“It was this initial work and the desire to explore frontier basins that led to the Indonesian frontier Basins Project.”

That group of former Unocal Indonesia Co. employees started Black Gold Energy LLC after the Chevron-Unocal merger.

Black Gold is an exploration company currently focused on Indonesia but planning to expand into other areas, according to AAPG member John Decker, the company's general manager in Jakarta.

As a forerunner to the extensive TGS-NOPEC survey, Unocal conducted its own bathymetry/backscatter study of selected areas offshore Indonesia in 2003, Decker said.

“We did a program where Unocal was able to convince itself – and convince everybody who worked on the project – that oil seeps could be found on the ocean bottom,” he said.

“And it worked very, very well,” he added. “It's an incredibly powerful differential tool for basins.”

Surveying the Scene

Most seabed seeps found in the Unocal and TGS studies were gas seeps of various sizes, but several liquid hydrocarbon seeps also were discovered.

“In those situations we can run biomarkers, determine the age of the oil, the age of the source, the source facies of the oil,” Decker noted.

For instigating and underwriting the survey, the Indonesian government granted Black Gold right of first refusal on 10 offshore exploration blocks, half of them included in a current bid round, he said.

The company will conduct drilling operations there, probably in 2010-11, and “we intend to find and produce oil,” according to Decker.

He expects some major oil companies, large independents and national energy companies to join the hunt.

“The majors are looking at trends and basins,” he noted. “In this portfolio TGS has identified there are both prospect opportunities and huge basinal trend opportunities.”

He said the survey was so beneficial “we plan to use it in other basins around the world and in other basins in Indonesia.”

Gilleran said TGS-NOPEC drew on earlier studies, its own experience and consultation with industry experts to help define the survey expanse, which covers a number of large areas along the Indonesian archipelago.

"A lot of that was based on knowledge and geologic concepts and opportunity. We have been working in Indonesia for several years," he said.

He called the offshore survey "an incredible logistical operation – it's a huge area" covering a total length of about 5,000 kilometers.

"There's a lot of fishing in some of the areas – they fish in deepwater as well as shallow water,” Baillie said. “That's the kind of thing you run into in Indonesia.”

According to Gilleran, most of the offshore areas had been unevaluated, under-evaluated or poorly evaluated for exploration potential.

"A large number of potential prospects or even basins were written off by industry with little or no data at all, and some of the time with erroneous interpretation," he said.

Gilleran said TGS does not discuss individual survey costs but did say the investment was significant.

"We had up to 11 vessels operating at once," he said, including two seismic vessels, two multi-beam vessels, a coring vessel and chase boats.

‘A Step Beyond’

With the last of the processed seismic data arriving in July, the survey is finished and available for industry buy-in on a non-exclusive basis, Baillie said.

"In some areas we got excited about what we saw and we went back and acquired more data there, but it's all completed now-it's totally in the bag," he said.

With such a large area under study, the company concentrated on gathering proof of petroleum systems and producing plenty of data for evaluation.

"We took a portfolio approach, knowing we would get technical wins and technical not-so-much wins," Baillie said.

High-quality 2-D seismic was included instead of 3-D primarily because of the size of the evaluation area. More focused 3-D surveys could come later when companies zero in on specific prospects.

Baillie will discuss geological and geographical details and additional survey specifics at the AAPG Cape Town meeting.

In this case, an innovative approach paid off.

"Our results were quite spectacular," Baillie said.

"We've gone a step beyond anything we'd ever done in the past."

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