Exxon Mobil Corporation, one of the Big Oil majors, reported earnings of $6 billion ($1.41 per share assuming dilution) in the fourth quarter of 2018, down 29 percent from the $8.4 billion registered in the prior-year quarter.

Its revenue rose 8 percent to $71.9 billion in the fourth quarter compared to the same quarter in 2017. The Q4 2018 revenue was almost $5 billion lower compared to the third quarter. Revenue was also well below the $74.18 billion average forecast of some analysts.

Full-year 2018 results were more positive, however. ExxonMobil announced estimated 2018 earnings of $20.8 billion ($4.88 per share assuming dilution), up 6 percent compared to $19.7 billion year-on-year. Earnings were $21 billion as against $15.3 billion in 2017 excluding U.S. tax reform and asset impairments.

For the full-year 2018, ExxonMobil's profits amounted to $20.84 billion, slightly higher than the profit of $19.7 billion in 2017. ExxonMobil said 2018 was its best year since 2014 when it earned $32.5 billion.

“Strong results during a period of commodity price volatility demonstrate ExxonMobil’s ability to deliver superior cash flow in different market environments,” said CEO Darren Woods. “Our continued focus on long-term fundamentals and portfolio improvements position us well to grow shareholder value.”

Woods also said ExxonMobil’s 2018 results also demonstrate its advantages in technology, scale and integration that will allow it to successfully compete across commodity price cycles.

The world’s largest oil refiner also exceeded analysts' forecasts by almost one-third. The reasons: its biggest refining boom in six years and a massive boost in its Permian Basin shale oil output. Encompassing Texas and New Mexico, the Permian Basin is North America's most prolific oil field and a source of reliable revenues and income for Big Oil. Woods said the company will see "very good returns" in the Permian.

The Baytown Refinery of ExxonMobil in Texas
The Exxon/Mobil refinery in Baytown, Texas. Scott Olson/Getty Images

Analysts said oil prices rose in most of 2018 but plunged in the fourth quarter. This sharp drop was caused by a combination of strong production in the U.S. and elsewhere. It was also due to mounting concern that slowing global economic growth will derail demand for crude this year and into the next.

A drop in oil prices slowed down ExxonMobil's pace of spending on exploration. As a consequence, capital spending in Q4 was 13 percent lower year-on-year.

Exxon plans to spend $30 billion on new drilling and refinery expansions this year, up 16 percent from 2018. In Texas, ExxonMobil announced plans to expand its Baytown refinery to handle growing Permian crude output.