Exploration company Tullow Oil has written off $2.3 billion in relation to exploration work and some of its assets in 2014 and reduced its 2015 investment programme for a second time.
Tullow is working to contain costs amid a dramatic fall in oil prices.
It also said it was continuing to review its core business, days after a source told Reuters the firm was expecting to make job cuts.
The company, which focuses its activities in Africa, said it expected to make a gross profit of $0.6 billion in 2014, with revenue of $2.2 billion, slightly below analyst estimates.
Tullow employs more than 2,000 people across 22 countries, with its African operations accounting for half the total workforce.
It had already cut its capital expenditure plans for this year to $300m, down from $1 billion invested in the first half of 2014 alone.
Today it further cut its capital expenditure plans to $200m.
Oil companies across the globe have been hit by a 60% drop in crude prices in seven months, putting them under pressure to find new areas of their businesses where costs can be trimmed.
British oil major BP has already announced a $1 billion restructuring programme that will involve thousands of job cuts. Rival Shell, meanwhile, has said that it will cut 5-10% of workers at its Albian Sands mining project in Canada.
The company's chief executive Aidan Heavey said that it had already taken steps to strengthen the business to adapt to current market conditions.
He said this work will continue during the year to ensure the company is in a position to benefit when conditions improve.
The Tullow CEO said that it had re-allocated its future capital to focus on delivering high-margin oil production in West Africa which will grow significantly to around 100,000 bopd net to Tullow by the end of 2016 and will generate stable, long-term cash flows for the business.
"While this is a challenging time for our sector, Tullow is fortunate to benefit from world-class, low cost and high margin assets, strong and growing cash flows and a broad, diversified funding position," he added.
The company said its key new production asset, its TEN oilfield in Ghana, is on track for a mid-2016 start-up.
