Amerisur Resources and new partner Occidental Petroleum (Oxy) are set to start a multi-well drilling campaign onshore Colombia as early as the first quarter next year after agreeing a farm-in deal worth $93.2 million.

US independent Oxy is fronting the cash for drilling and the majority of investments for new 2D seismic after agreeing to take half of Amerisur’s 100% interest in four blocks — Putumayo-9, Terecay, Tacacho and Mecaya — in south-west Colombia’s Putumayo basin.

“It is basically the start of the development of this basin,” Amerisur chief executive John Wardle told Upstream after it revealed the deal, which will see Oxy pay 100% of a $38 million five-well drilling programme as well as 85% of a gross cost of $65 million for 878 kilometres of new 2D seismic.

Wardle said the maiden well will be in Putumayo-9 in the first or second quarter, with a second coming in Mecaya, possibly in the third quarter. Tacacho will then see three wells, the first of which could spud around the end of 2019, with Wardle not predicting activity at Terecay before 2020.

All targets are oil and conventional, with the partners having flexibility in the drilling programme to move the sequence of wells.

“We are basically trailblazers in this area. But we are not inventing a new paradigm here, we are basically applying the same exploration techniques and concepts that have been applied in Ecuador and Peru over the years with some very interesting results,” Wardle said.

Drilling depths at Amerisur’s Platanillo block in the area are around 9000 feet (2743 metres), with wells taking 17 or 18 days to drill, he said. Well depths at Tacacho are expected to be about 4500 to 5000 feet and drilling should take 12 to 14 days.

“Mecaya, Terecay and Tacacho were not in our immediate short and medium-term programme. The effect of this deal (with Oxy) is to bring forward the exposure to those very large resource bases while not giving us any requirement for capex — it is full financed, basically.”

Wardle said Amerisur needed to bring in a partner to finance exploration at Terecay and Tacacho in particular as they are large blocks, each at nearly 590,000 gross acres.

The first has estimated gross prospective resources of 224 million barrels of oil, with the second at 364 million barrels. By contrast, Putumayo-9 is given a gross prospective resource estimate of 64 million barrels and Mecaya just 4 million — although Wardle said all estimates are conservative.

“We decided to only speak with larger companies, because the materiality in this portfolio gives you that access,” Wardle said of the farmout process, which was launched late last year.

“We decided to go with Oxy, not on the basis of what their potential offer would be, but more the ability to work with them, their understanding of the prospects, which is very deep.”

Amerisur spoke with other companies active in Colombia, but not as large as Oxy, which is the second-largest producer in Colombia behind state player Ecopetrol and has been present in the country for more than 40 years.

Amerisur will retain operatorship of the blocks as part of the farmout deal, while Oxy will also get access to its partner's OBA export pipeline, which runs across the border into Ecuador.

“That will be tariffed at commercial rates to the partner,” Wardle said.

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Amerisur links with Oxy for Colombia wells drive