Where to look for fields?

Oil and gas develop in sedimentary basins. We are therefore going to be interested in those zones where superimposed layers of different rocks have accumulated over tens of millions of years. Sedimentary basins are numerous on the surface of our planet. They can be found, of course, at sea, but also on land, in zones that were in the past covered by the sea.

In the early days of the petroleum adventure, nowhere had been drilled: the basins were totally untouched by exploration. Today, virgin basins are very rare. Only a few such zones remain, because their climate or geography is very hostile, or because they are still protected for ecological reasons, such as in the Antarctic. Therefore we know which zones are rich in oil or in gas (or both), those are the prolific basins. Others are less rich and some totally sterile.

Moreover, the sedimentary basins have been more or less explored. Those known for a long time have been the object of numerous drilling operations and are in little danger of revealing new, super-giant deposits or even ones of a biggish size: we say in this case that the exploration is mature. This is the case, for example, in the North Sea. The petroleum companies who explore are obviously going to aim at positioning themselves in regions which are still far from mature, to be able to discover big volumes of hydrocarbons.

Nevertheless, exploration work remains to be done, even in the mature zones. There, it is a question of looking for smaller and subtler deposits (more difficult to see or to get images). Drilling can also be done alongside fields already discovered.

Can a petroleum company undertake drilling wherever it wants and whenever it wants? No, because what is under the surface of the earth belongs everywhere to the state. This is not only true on land, of course, but also at sea. A country is owner of the mineral resources situated up to 200 nautical miles off its coasts and on the whole of its continental plateau (see illustration).

Interested companies send in their propositions: an undertaking for the total amount to be spent and for the volume of exploration work to be completed over a given period (in general from 2 to 5 years). The companies often act in groups of associates of 2 or 3 companies, which allows them to share the expenses (enormous!) and the risks (high!) if their propositions are accepted. At the due date of the tender operation, the countries examine all the offers and choose the company, or association of companies, that is going to be responsible for drilling the proposed zones. Once a company has obtained the exploration licence (or permit), work can begin. The company can at any moment negotiate the sale of part or all of its interests in the zone it has just acquired. For this reason, a sort of permanent market in zones for exploration exists. For some of the zones, exploration is just beginning. For others, drilling has already been carried out and, according to whether the results are positive or negative, interest in the zone increases or diminishes and its traded value likewise. Within all oil companies, there are teams of specialists who permanently follow all the propositions for sale of interests throughout the world.
The sales or the exchanges of interests are the object of bitterly disputed negotiations.