Lake will be leaving the position with immediate effect, according to a company statement.
Jens Pace, currently serving as chief operating officer, will assume the role and will be joining the company’s board in “due course”, African Petroleum said.
Pace, a geoscientist with over 30 years of industry experience, held exploration leadership roles in Africa and other regions for BP.
“It is with regret that Stuart is leaving us and we wish him a speedy and full recovery. He has been a great leader for African Petroleum and has enabled the company to take great strides forwards,” Charles Matthews, chairman of African Petroleum said.
“Jens and the rest of the experienced management team have been working very closely with Stuart during our ongoing partner negotiations and we remain confident in our ability to successfully conclude transactions in the near future,” he said.
Earlier this year, African Petroleum raised $12.5 million in a private placing to fund its budding west African exploration drive.
At the time, Lake said that the net proceeds from the placing would be used to fund an ongoing exploration programme, including seismic costs and licence fees.