Tullow Oil today announced that chief executive Aidan Heavey will leave the role to become group chairman later this year, and will be replaced by the company's chief operating officer, Paul McDade.
Heavey, who founded Tullow and has led it for 31 years, will take on the chairman role after the group's annual general meeting on 26 April, replacing Simon Thompson, who is stepping down from the board.
Thompson said today that the board has "long been aware of the need to plan carefully for Aidan's retirement from Tullow".
"After careful consideration of the options, we are confident that this succession plan provides Tullow with the right combination of stability, continuity and fresh-thinking," he added.
"Paul has been an outstanding member of the board and has served Tullow with great distinction for 12 years as COO. With Aidan as chairman, Paul and Tullow will continue to benefit from the founder’s years of experience and deep understanding of the relationships that underpin our business in Africa."
News of the changes follow's Tullow's announcement last week that finance chief Ian Springett is to take an extended leave of absence from the company in order to undergo medical treatment.
The firm also reported today that revenue in 2016 is expected to have fallen by 19 per cent to $1.3bn (£1.1bn), blaming continued weak oil prices.
Tullow also said production from its new Tweneboa, Enyenra, Ntomme (TEN) oil fields in Ghana is expected to average 50,000 barrels per day (bpd) this year, lower than previously expected, due to problems with managing pressure in one of the reservoirs.
Meanwhile, capital expenditure has been cut again - in 2017, spending linked to operating activities is expected to reduce from $0.9bn to $0.5bn.
Heavey said 2016 had been "another tough year for the oil and gas sector and for Tullow".
However, he added: "The company showed exceptional resilience and strong operational performance to deliver TEN on time and on budget; to deal with the technical issues at Jubilee; make good progress in exploration and development in East Africa and begin the process of reducing our debt from free cash flow.
"Tullow is therefore now very well placed to take advantage of the opportunities that conditions in the sector offer. We took action early to deal with lower oil prices and we are now benefitting from the re-set and re-structured business that we created."