Remote location presents challenges

Africa Rift Basin Is a New Frontier

American Association of Petroleum Geologists (AAPG)

Talk is rife about the end of the big finds in the oil patch.

Yet the explorers take the edge off of such thinking as they continue to come up with new impressive discoveries – such as the Albert Basin situated on the western arm of the East African rift valley.

“The Albert Basin is one of the newest petroleum basins in sub-Sahara,” said AAPG member Paul Logan, chief geologist at Heritage Oil in Towcester, England. “We think it’s a petroleum system with potentially several billion barrels of oil.

“It’s a very large basin,” Logan noted, “about 45 kilometers across by maybe 90 kilometers long.

“There were some wells drilled in the 1930s which found some oil shows,” he said. “There are some oil seeps around the margins of the basin, which is what drew us and others in to look here.”

Heritage, which has worked in Uganda for a number of years, is currently busy with its licenses along Lake Albert on the western Ugandan side of the Albert Basin. It shares a 50-50 interest with Tullow Oil on Block 3A along the southern part of the lake and on Block 1 to the north.

In between, Tullow holds a 100 percent interest in Block 2.

“In the past two years there have been 10 wells drilled in this area, all of which have been successful,” Logan said. “Some have been appraisal wells, but for a new frontier province it’s a pretty astonishing success rate.”

Promising Beginnings

The two companies participated in a significant Heritage-operated discovery well – the Kingfisher #1 – in 2007, which went down on the eastern shore of Lake Albert in Block 3A. The well flowed almost 14,000 barrels per day of light, sweet oil from four zones in the Miocene-Pliocene rocks, according to Logan.

An appraisal well – the Kingfisher #2 – is currently drilling.

It’s designed specifically to appraise reservoir zones discovered by the Kingfisher #1 well and to explore a deeper potential objective not reached by the initial well because of rig limitations.

At press time the appraisal well had reached a depth of 9,642 feet, with the drill bit headed toward a total depth of 13,530 feet. Heritage reported that excellent oil shows had been encountered from three potential sandstone reservoir zones over a gross vertical interval of approximately 345 feet. Preliminary interpretation of the zones indicated they could be the lateral equivalent of three pay zones in the Kingfisher #1 well.

Logan noted they’re drilling on a little spit of land that juts out into the lake because they don’t have the capacity to drill in the lake, which is more than 400 feet deep at its maximum.

“We have to drill from shore, and there’s a limit to what we can reach,” he said. “We work closely with Tullow and we both have prospects in the lake, so we’re working to bring a unit in to enable both of us to drill in the lake toward the end of the year or early next year.”

The Ugandan/Democratic Republic of Congo border extends along the middle of Lake Albert. For now the two companies are limited to drilling on the Uganda side of the lake, but they hold title to the two blocks encompassing most of the DRC side and will have the OK to drill there once they acquire a presidential decree.

A Daunting Task

Working in such a remote area can sometimes be a daunting task in myriad ways. Lack of road access to the Kingfisher drill site, for example, creates a significant challenge.

Logan noted they shipped a barge in from Houston, which arrived in the form of 12 or more modular units. Each unit had to be driven 1,200 kilometers, placed in the lake and put together to construct the barge. This enabled the crew to ship the rig, supplies and equipment down the lake to the drill site.

It’s not just the logistics on the drilling side that make this a tough go.

Global Geophysical Services faced similar challenges early last year when it teamed up with IMC Geophysics International to conduct a seismic survey for Heritage.

 Global transported its specialized acquisition equipment from the United States to Uganda to work with IMC in the southern part of the lake to acquire a seamless 3-D data set across the water, the land component of the survey area and the gap between. The equipment was disassembled in Houston, shipped, transported over land via trucks, barged down the lake and reassembled at the shore.

Weather in the region poses another problem for operations. Severe storms are a familiar occurrence in this lake locale, so it’s not a benign environment.

Any new exploration target presents its own set of geological challenges, and the Albert Basin is no exception.

“We’re using high resolution quantitative palynology to establish a stratigraphy for the first time in this basin because there was nothing there before,” Logan said. “We’ve been very successful in doing that.

“The palynology has proved vital in understanding the climatic and depositional history of the sequence,” Logan noted. “We’ve established the age of the basin as being Miocene and younger, which has been quite important, so it’s quite a young basin.

“It’s a challenge to come to grips with a completely new basin,” Logan said.

“But this is no puddle – It’s potentially quite a significant petroleum province.

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Several papers on the Albert Basin and other plays in east and central Africa will be presented during the AAPG International Conference and Exhibition, set Oct. 26-29 in Cape Town, South Africa.

Paul Logan will present the paper “Exploration on the Frontier – Toward an Understanding of the Albert Basin” at 3:10 p.m. on Monday, Oct. 27.

His paper is part of a session titled “East and Central Grabens of Africa: Unraveling the Puzzle.” 

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