British energy explorer Tullow Oil said Thursday some of its oil reserve areas in Kenya were poorly developed, though it remained upbeat about the potential.

Tullow announced exploration results from Blocks 10BB and 13T, which it operates in parity with Africa Oil Corp.

Tullow said it encountered a "poorly developed oil bearing reservoir" in Block 13T, though deploying rigs elsewhere in the nearby Amosing discovery would target an area it said "may be one of the largest discoveries in the basin to date."

African Oil Corp., in a separate statement, said early 2013 testing from both blocks yielded a flow rate of about 5,000 barrels of oil per day.

Angus McCoss, exploration director for Tullow, said in a statement early exploration results from Kenya were in line with expectations.

"Our focus remains on continuing to explore and appraise our first successful basin, as well as stepping out into several untested basins, which together form a chain of prospective basins that have the potential to become a transformational new oil province," he said.