LONDON—BP added more than a billion dollars to its share buyback programme on Tuesday as it likened itself to a “cash machine” benefiting from higher oil and gas prices and a strong trading performance in the third quarter. Natural gas and power prices around the world surged this autumn as tight gas supplies collided with strong demand in economies recovering from the pandemic. BP said it expected natural gas prices to remain strong in the coming months of peak winter demand. The company “is a cash machine at these sort of (oil and gas) prices and the business is running very well,” Chief Executive Officer Bernard Looney told Reuters. Underlying replacement cost profit, the company’s definition of net earnings, reached $3.32 billion in the third quarter, exceeding analysts’ expectations for $3.06 billion. That compares with $2.8 billion in profit in the second quarter and $86 million a year earlier, when …