The Magdalena River is considered to be one of the great rivers in South America.
It originates in the Andes Mountains and travels northward for a distance of 1,000 kilometers, draining an area of 400,000 square kilometers prior to flowing into the Caribbean Sea near Cartagena.
The river drops its cargo of mixed volcanic, basement and reworked clastic sediments into the offshore Colombia basin at a water depth exceeding 4,000 meters subsea. The result is a delta and a deepwater fan up to 16 kilometers thick and covering a 180,000-square-kilometer area, built from Miocene to the present time.
Operators long have been captivated by the region’s onshore oil and gas seeps and mud volcanoes, along with the evidence pointing to oil and gas seepage offshore.
Oil and gas shows have been commonplace in the many wells drilled onshore and near shore.
Even so, only modest-scale accumulations have been encountered onshore. One sizeable (five TCF +/-) shallow water gas field dubbed Chuchupa-Ballena was discovered near the coastline.
But there’s excitement aplenty over the potential for good things to come.
The Right Neighborhood?
Anadarko (APC) has six leases in the deepwater Magdalena fan, one being a farm-in with Ecopetrol. APC is the operator of all six blocks, two of which are technical evaluation agreements and four being E&P contracts.
“We’re doing a 5,250-square-kilometer 3-D on five blocks with our partner, Ecopetrol,” said AAPG member Brian Frost, new ventures manager for international business development at APC. “In the next couple of months, we’ll start acquiring a 2-D survey on one of our technical evaluation agreement areas.
“We’re supposed to drill two exploration wells at the end of 2014/2015,” he said. “These will be the second and third deepwater wells in all of Colombia.”
The first well was drilled by ExxonMobil, Petrobras and Ecopetrol about five years ago in 450 meters of water, basically testing the upper slope, Frost noted.
“We’re going for the reservoirs down at the toe-of-slope,” he said. “These wells will be in about 1,000 to 1,200 meters of water, and we see potential down to 3,000 meters water depth.”
Anadarko began looking in Colombia about four years ago, intrigued by the huge delta sitting there since Miocene time and the many oil and gas shows onshore. Piston coring in the deepwater revealed evidence of hydrocarbons.
“We thought it was a lot like East Africa prior to 2009, a lot of oil and gas shows onshore and seeps on the coastline,” Frost said. “A lot of wells were drilled onshore and on the shelf, but no one found anything very big.
“We’re hoping it’s like East Africa was, meaning it’s the right neighborhood but the wrong address,” he said. “I think the right address is deepwater; that’s the place that hasn’t been looked at yet.
“What we’ve seen are large structures, and we think there’s good reservoir potential,” Frost notes. “What it needs is drilling, and that’s what Anadarko does – we drill wells.”
Solving the Puzzle – Now
Sparse 2-D data can be tied back to a DSDP (Deep Sea Drilling Project) well drilled 200 kilometers offshore during the 1970s that shows some Cretaceous source rock potential. The well drilled into Cretaceous volcanics and encountered rocks with relatively high TOC content.
“The depositional environment was unusual,” Frost emphasized. “There were phosphatic beds, which is something you don’t expect to find on oceanic crust.
“We can tie that back underneath the Magdalena fan, and if that facies improves in organic content and source rock richness, then you could have a sizeable petroleum system for something where you don’t have any outcrops for source rocks,” he said.
“In East Africa in the Rovuma Basin, we and Eni have probably found 150 TCF of gas, but we still have no clue what the source rock is.
“That’s disconcerting,” he noted wryly.
Still, this geoscientist takes a pragmatic approach to exploration.
“As explorers, we must deal with not enough information,” he said. “But if you wait around until you have all of the pieces to the puzzle, then there won’t be much opportunity left.”
It’s a given that exploration is a risky business, particularly when you’re pushing beyond the boundaries of the known.
“If you do jobs correctly in frontier exploration, you may only be looking at a 25 percent chance of success,” Frost cautioned. “So you’ll be wrong more often than right.
“But the times we do get it right we can hit homeruns, so it’s worthwhile to do.” he said. “Even though some places didn’t work for us, our deepwater programs have been very successful.”
He emphasized that what the deepwater Caribbean offshore Colombia needs now is more seismic coverage and wells.