The four blocks are located in deep waters some 150 kilometers off Colombia's northern Caribbean coast, Ecopetrol said in a statement.
Ecopetrol will take a 40% stake in the blocks, while Occidental subsidiary Anadarko Colombia Co will have a 60% stake and will serve as the blocks' operator, Ecopetrol said.
"We're very pleased to seal this new alliance with (Occidental), a first-rate partner, to continue strengthening our exploration portfolio in Colombia's Caribbean," Ecopetrol Chief Executive Felipe Bayon said in the statement.
The deal is subject to approval from Colombia's oil regulator, the company said.
(Reuters - Reporting by Oliver Griffin; Editing by Leslie Adler)