Hopes for a $40 billion-plus oil and gas deal bonanza this year and next have been dashed by the scrapping of some high-profile sales, but bankers are still optimistic that growing confidence in commodity prices and a wealth of capital will keep them busy.

The collapse of plans by ExxonMobil and apparently Italy's ENI for Australian asset sales worth several billion dollars in total have put a hole in the pipeline of deals for 2021, with Wood Mackenzie describing the development as "worrying" for the M&A outlook.