Exxon Mobil has today reported a quarterly profit that topped analysts' estimates, as its oil and natural gas output rose slightly on a year-over-year basis. 

The company's fourth-quarter net income fell to $6 billion, or $1.41 a share, from $8.38 billion a year ago. 

But earnings excluding the impacts of tax reform and impairments rose to $6.4 billion from $3.73 billion a year ago. 

Analysts had forecast a $1.08 a share profit excluding one-time items, according to data from Refinitiv. 

Exxon's oil equivalent production rose to just over 4 million barrels per day, up from 3.9 million bpd in the same period the year prior. 

The company said its output in the Permian Basin, the largest US shale basin, rose 90% from a year ago. 

Exxon said it earned $1.1 billion more in its upstream business than it did in the fourth quarter of 2017, and said higher natural gas prices were partially offset by lower liquids pricing. 

Pretax earnings in its refining business were $2.7 billion, up $1.70 billion over the same time the previous year. 

Profits in Exxon's chemicals business were down $191m on weaker margins, growth-related expenses and higher downtime and maintenance.

Exxon chief executive Darren Woods credited the better than expected results to the company optimising its operations across the board.