Abandonment and dismantling of a field

At what point is a field abandoned ? The answer is simple: as soon as the oil or gas starts to be more expensive to extract than it is sold for. In general that happens because of a drop in production, as a consequence of pressure reduction in the field. It can also happen when the proportion of water extracted increases rapidly, or again, for oil wells where the gas is not commercialised, when the proportion of gas makes a sudden jump (when the pressure descends beyond the thermodynamic bubble point). More rarely (fortunately!), a well can be prematurely abandoned following a bad surprise, for example a well productivity significantly below forecast. The life of a field also depends on the price of oil and gas. It is obvious that if the price of a barrel of oil goes from 50 to 100 dollars, all fields will be exploited longer than was initially planned. On the contrary, if there is a long-term drop in prices, certain fields will be abandoned earlier than planned.

When a petrol company abandons a field, its life does not necessarily stop even then. If the field is no longer profitable for one company, other smaller companies may be interested in taking it over, because their overheads are lower, or they are satisfied with a profitability lower than that demanded by the major companies. Or again, the smaller companies may be content with production volumes that would no longer satisfy the large companies. The national company of the country involved sometimes also takes back fields abandoned by the companies.